On April 26, 1986, operators at the Chernobyl Nuclear Power Plant were running a test to see what would happen to its nuclear reactors in a power outage — and they triggered the worst nuclear accident in human history.

The plant generated fission power using several nuclear cores, where uranium atoms were split. The process generates successively more heat and free neutrons as atoms split into progressively lighter ones, eventually turning feedwater into steam that powers turbines. Separate cooling water that circulated around the plant's nuclear cores and a "moderator" material was meant to keep the reaction stable.

Reactor 4 was scheduled to be shut down for regular maintenance, so the operators decided to test whether, during a power outage, the turbines could keep the coolant water circulating long enough for the emergency diesel generators to kick in.

The operators started reducing power to the reactor around 1 a.m. on April 25. However, a Kyiv-based operator that controlled the electricity grid wouldn't allow for a complete shutdown, as the grid needed power. So contrary to the prescribed test protocol, the reactor was kept at half-power levels from 2 p.m. to around 11 p.m. local time. (This decision led to a buildup of xenon that made the reactor unstable.)

By the time the test resumed, a less-experienced night crew was on duty. Ideally, the team should have raised power to a higher level to stabilize the reactor before restarting the shutdown test. Instead of bringing the power back up, the operators accidentally lowered it further.

By about 12:30 a.m. on April 26, they realized the power had dropped too rapidly. They tried to raise it by removing almost all of the control rods, which are designed to slow the atom-splitting reaction by absorbing neutrons. The power levels then fluctuated rapidly, and the operators took multiple measures to control the reaction, including temporarily lowering feedwater levels.

A power surge 100 times larger than normal was detected. The operators then tried to get the reaction under control by lowering all 211 control rods into the core, but they jammed. At 1:23 a.m., two back-to-back steam explosions occurred, blew the roof off the building, and spewed radioactive material high into the atmosphere. The debris triggered a massive fire. The core had partially melted down.

Hundreds of thousands of people were forced to evacuate nearby towns. Two workers died immediately in the disaster, and some of the emergency firefighters and "liquidators" who raced to contain the fire and prevent further melt down ultimately died of radiation sickness or cancer down the line. The cancers were likely caused by the radioactive iodine, strontium and cesium that permeated the area after the explosions.

The former Soviet Union tried to keep the meltdown a secret, but elevated radiation levels were detected across Europe, particularly in Scandinavia, in the weeks following the disaster.

In the years after, children in nearby regions experienced higher levels of thyroid cancer than had been typical in the past. But a United Nations report from 2000 found "no increases in overall cancer incidence or mortality that could be associated with radiation exposure." That said, the report acknowledged that some upticks in cancer rates would be expected to take decades to show up in the data.

Today, the 1,000-square-mile (2,700 square kilometers) Chernobyl exclusion zone around the plant is one of the most radioactive places on the planet and a nature preserve. It is also a natural test bed to see what happens when animals and plants are exposed to high levels of radiation, as well as a direct example of "evolution in action."

Experts have spent decades dissecting the missteps that led to the catastrophe, including the poor training of the nuclear plant operators and their subsequent failure to follow safety protocols. Keeping the reactors at half power for hours didn't help, either.

But at heart of the meltdown was a critical design flaw in the Reaktor Bolshoy Moshchnosti Kanalnyy (RBMK) reactors used at Chernobyl and elsewhere in the Soviet Union. All reactors use a "moderator" material to slow fission-produced neutrons so they can stay in the core and fuel further reactions, while water is used as a coolant to keep the cores from overheating and triggering a runaway reaction.

In the "light water" nuclear reactors typically used in the U.S. and Europe, water is both a moderator and a coolant. This means that, as the reaction gets hotter, more and more water turns to steam, leaving less water to act as a moderator, Live Science previously reported. The reaction has a built-in negative feedback loop in which the more heat and steam is produced, the less efficiently fission occurs.

At Chernobyl, however, graphite served as the moderator. In such a system, as steam forms, the graphite heats up, and the fission reaction speeds up as well. This creates the potential for a runaway positive feedback loop, because steam creates voids where the reaction speeds up, which can quickly boil all the coolant water. This is called a "high positive void coefficient."

It didn't help that the control rods were tipped with graphite, which temporarily sped up the fission reaction just as the operators were trying to slow it down. British officials had warned the Soviets that RBMK reactors had serious defects at least nine years prior to the Chernobyl accident, but most of those issues were not corrected, The New York Times reported at the time.

There are several RBMK reactors still operating in Russia, but most of those have undergone extensive safety retrofitting so that such a runaway reaction is, in theory, much less likely.

China's nuclear fusion reactor, dubbed the "artificial sun," has breached a major fusion limit by firing plasma beyond its usual operational range, advancing humanity's slow progress towards near-limitless clean energy.

The Experimental Advanced Superconducting Tokamak (EAST) kept plasma — the high-energy fourth state of matter — stable at extreme densities, which was previously seen as a major obstacle in the development of nuclear fusion, according to a statement released by the Chinese Academy of Sciences.

"The findings suggest a practical and scalable pathway for extending density limits in tokamaks and next-generation burning plasma fusion devices," study co-lead author Ping Zhu, a professor in the School of Electrical and Electronic Engineering at the University of Science and Technology in China, said in the statement.

Nuclear fusion offers the potential for near-limitless clean energy. In other words, energy without much nuclear waste or climate-warming greenhouse gas emissions released by burning fossil fuels. The new findings, published Jan.1 in the journal Science Advances, could bring our species one step closer to unlocking this energy source, which some researchers claim we could harness within decades.

However, nuclear fusion technology has been in development for more than 70 years, and it's still very much an experimental science, with reactors typically consuming more energy than they can produce. Meanwhile, climate scientists are calling for deep cuts to greenhouse gas emissions now as the impacts of climate change are already being felt around the world. Nuclear fusion is therefore unlikely to represent a practical solution to the current climate crisis — but could power our world in the future.

Fusion reactors are designed to fuse two light atoms into a single heavy atom via heat and pressure. By doing so, they generate energy in a similar way to the sun. However, the sun has a lot more pressure than Earth's reactors, so scientists compensate by corralling hot plasma at temperatures far hotter than the sun.

China's EAST is a magnetic confinement reactor, or tokamak, designed to keep plasma continuously burning for prolonged periods. The reactor heats plasma and traps it inside a donut-shaped chamber using powerful magnetic fields. Tokamak reactors have yet to achieve fusion ignition, which is the point at which the fusion process becomes self-sustaining, but the EAST reactor has been increasing the amount of time it can maintain a steady, highly confined loop of plasma.

One hurdle for fusion researchers is a density limit called the Greenwald Limit, beyond which plasma typically becomes unstable. This limit is a problem because, while higher plasma densities enable more atoms to whack into one another, thereby lowering the energy cost of ignition, instability also kills the fusion reaction.

To overcome the Greenwald limit, scientists at EAST carefully managed the plasma's interaction with the reactor's walls by controlling two key parameters upon starting the reactor: the initial fuel gas pressure and the electron cyclotron resonance heating, or the frequency at which electrons in the plasma absorbed microwaves. This kept the plasma stable at extreme densities of 1.3 to 1.65 times beyond the Greenwald Limit — much higher than the tokamak's usual operational range of 0.8 to 1, according to the study.

This isn't the first time the Greenwald Limit has been breached. For example, the U.S. Department of Energy's DIII-D National Fusion Facility tokamak in San Diego broke through the limit in 2022, and in 2024, researchers at the University of Wisconsin–Madison in Wisconsin announced that they had maintained a stable tokamak plasma at about 10 times the Greenwald Limit using an experimental device.

However, the breach at EAST enabled the researchers to heat the plasma to a previously theorized state called the "density-free regime" for the first time, where the plasma remained stable as the density increased. The research is based on a theory called plasma-wall self organization (PWSO), which proposes that a density-free regime could be possible when the interaction between the plasma and the reactor's walls is in a carefully balanced state, according to the statement.

Progress made at EAST and in the U.S. will inform the development of new reactors. China and the U.S. are both part of the International Thermonuclear Experimental Reactor (ITER) program, which is a collaboration between dozens of countries to build the world's largest tokamak in France.

ITER will be another experimental reactor designed to create sustained fusion for research purposes, but could pave the way for fusion power plants. The ITER reactor is expected to begin producing full-scale fusion reactions in 2039.

Nuclear waste could be repurposed into a rare isotope necessary for nuclear fusion, which could theoretically produce near-limitless amounts of clean energy, one scientist says.

The radioactive version of hydrogen, called tritium, is not naturally readily available on Earth, is expensive to produce, and can be made in limited quantities. At the fall meeting of the American Chemical Society (ACS) this week, Terence Tarnowsky, a physicist at Los Alamos National Laboratory, suggested that tritium could be harvested from a byproduct of nuclear fission, which powers existing nuclear reactors.

Nuclear fusion is the process of combining atoms to release heat. While several fusion reactions could theoretically produce power, one of the more common ones would fuse tritium with deuterium, another isotope of hydrogen, to produce helium.

But, as of now, nuclear fusion is not possible on a commercial scale because scientists have not yet figured out how to achieve large-scale ignition — the point where a self-sustaining reaction produces more energy than is put in.

Another big barrier, though, is the cost of fuels like tritium.

"Nuclear fusion has the potential to offer emission-free, abundant energy," Tarnowsky told Live Science. "But there's limited availability and a high cost for tritium right now, and that presents a barrier to the technology's success."

Producing tritium efficiently

The first generation of nuclear fusion reactors that will contribute to the power grid will likely rely on a reaction that requires tritium, Tarnowsky said. While other fusion reactions, such as fusing deuterium and helium-3, could theoretically be harnessed to produce power, they require much higher temperatures to work and are therefore more expensive and less practical.

Gathering large amounts of tritium, though, presents a problem: The isotope is radioactive and has a very short half-life. Collections of tritium decay by 5.5% per year, "so you can't put excess tritium in a bank and get it all in 50 years like you can with other energy sources," Tarnowsky said.

Related: World's largest nuclear fusion reactor is finally completed. But it won't run for another 15 years.

For future nuclear fusion plants to be successful, a new, cheaper method of producing tritium will be necessary, Tarnowsky said. "You need to have this capability already up and running."

Current nuclear plants rely on nuclear fission, during which atoms split apart and release energy. But fission results in significant amounts of long-lived nuclear waste. Spent nuclear fuel — fuel that once powered nuclear fission but is no longer usable — is made up of unusable uranium and plutonium, along with products of fission, like strontium and iodine isotopes, which can take up to hundreds of millions of years to decay, according to the U.S. Environmental Protection Agency.

Tarnowsky proposes generating tritium from the vast amounts of still-radioactive nuclear waste by using a particle accelerator to split the atoms in that waste. The dividing atoms would go through a series of reactions, eventually yielding tritium. The process wouldn't eliminate nuclear waste, because the leftovers from this process would be as hazardous as the starting material, but it would get further use from this byproduct.

The basic principles of the design are not new, Tarnowsky said in a statement from ACS, but recent technological advances could make this method of producing tritium vastly more efficient.

Tarnowsky's early calculations estimate that, using 1 gigawatt of energy — which costs at least tens of millions of dollars — this system could produce 4.4 pounds (2 kilograms) of tritium in a year. That amount of tritium, if used for nuclear fusion, could power tens of thousands of homes in the U.S. for a year.

Tarnowsky projects that this design could produce more than 10 times as much of the isotope as other methods, using the same amount of power.

"A very large paradigm shift"

Right now, the U.S. lacks a stable, predictable and cheap supply of tritium, which costs about $15 million per pound ($33 million per kilogram), Tarnowsky said in the statement. Meanwhile, we do have thousands of tons of nuclear waste, which is expensive to store and potentially harmful to surrounding environments.

"This technology is possible today," he told Live Science. "It would be a very large paradigm shift with respect to utilizing the spent nuclear fuel that we have already, owned by the government."

Many details still need to be worked out before Tarnowsky can create a full proposal for how this would work.

But Tarnowsky is excited that his design is being received positively now, given that nuclear accidents like those at Three-Mile Island and Chernobyl made nuclear power a taboo topic just decades ago. "The times have changed," he told Live Science.

A recently concluded experimental campaign at the Wendelstein 7-X stellarator at the Max Planck Institute for Plasma Physics (IPP) in Greifswald, Germany has smashed previous fusion records and set a new benchmark for reactor performances.

Nuclear fusion offers a tantalizing promise of unlimited clean energy. By smashing together isotopes (or different versions) of hydrogen at incredibly high temperatures, the resulting superheated plasma of electrons and ions fuses into heavier atoms, releasing a phenomenal amount of energy in the process.

However, while this fusion reaction is self-sustaining under the extraordinary temperatures and pressures within stars, recreating these conditions on Earth is a huge technical challenge — and current reactor concepts still consume more energy than they are able to produce.

Stellarators are one of the most promising reactor designs, so named for their mimicry of reactions in the sun. They use powerful external magnets to control the high-energy plasma within a ring-shaped vacuum chamber and maintain a stable, high pressure. Unlike simpler tokamak reactors — which pass a high current through the plasma to generate the required magnetic field — stellarators' external magnets are better at stabilizing the plasma through the fusion reactions, a feature that will ultimately be necessary when translating the technology to commercial power plants.

In the recent experiments, the W7-X stellarator outperformed previous benchmarks set by the decommissioned tokamak reactors JT60U in Japan and JET in the UK, especially over how long the plasma can be sustained.

Related: Nuclear fusion could be the clean energy of the future

Most notably, the international team revealed that the reactor had reached a new record high triple product — a key metric for the success of fusion power generators. The triple product is a combination of the density of particles in the plasma, the temperature required for these particles to fuse, and the energy confinement time (a measure of how well the thermal energy is held by the system). A certain minimum value called the Lawson criterion marks the point at which the reaction produces more energy than it uses and becomes self-sustaining, so a higher triple product indicates a more efficient reaction.

"The new record is a tremendous achievement by the international team," said Thomas Klinger, Head of Operations at Wendelstein 7-X and Head of Stellarator Dynamics and Transport at IPP in a statement. "Elevating the triple product to tokamak levels during long plasma pulses marks another important milestone on the way toward a power-plant-capable stellarator."

Key to the success of this latest milestone was the development of a new fuel pellet injector that combined continuous refueling of the reactor with pulsed heating to maintain the required plasma temperature. Over a 43-second period, 90 frozen hydrogen pellets were fired into the plasma at up to 2,600 feet (800 metres) per second, roughly the speed of a bullet. Pre-programmed pulses of powerful microwaves heated the plasma, which reached a peak temperature of 30 million degrees C, and this coordination between the microwave pulses and the pellet injection crucially extended how long the plasma could be stably maintained.

This same campaign also increased the energy turnover of the reaction to 1.8 gigajoules over a six-minute run, smashing the reactor's previous record of 1.3 gigajoules from February 2023. Energy turnover is a combination of the heating power and plasma duration of a fusion reactor and an indication of the reactor's ability to sustain the high-energy plasma. It is therefore another crucial parameter for future power plant operation. The new value even exceeds the record achieved by the Experimental Advanced Superconducting Tokamak (EAST) in China earlier this year, further evidencing stellarators' potential.

"The records of this experimental campaign are much more than mere numbers. They represent a significant step forward in validating the stellarator concept—made possible through outstanding international collaboration," summarized Robert Wolf, Head of Stellarator Heating and Optimization at IPP in statement.

Around the U.S., about 90,000 tons of nuclear waste is stored at over 100 sites in 39 states, in a range of different structures and containers.

For decades, the nation has been trying to send it all to one secure location.

A 1987 federal law named Yucca Mountain, in Nevada, as a permanent disposal site for nuclear waste — but political and legal challenges led to construction delays. Work on the site had barely started before Congress ended the project's funding altogether in 2011.

The 94 nuclear reactors currently operating at 54 power plants continue to generate more radioactive waste. Public and commercial interest in nuclear power is rising because of concerns regarding emissions from fossil fuel power plants and the possibility of new applications for smaller-scale nuclear plants to power data centers and manufacturing. This renewed interest gives new urgency to the effort to find a place to put the waste.

In March 2025, the U.S. Supreme Court heard arguments related to the effort to find a temporary storage location for the nation's nuclear waste — a ruling is expected by late June. No matter the outcome, the decades-long struggle to find a permanent place to dispose of nuclear waste will probably continue for many years to come.

I am a scholar who specializes in corrosion; one focus of my work has been containing nuclear waste during temporary storage and permanent disposal. There are generally two forms of significantly radioactive waste in the U.S.: waste from making nuclear weapons during the Cold War, and waste from generating electricity at nuclear power plants. There are also small amounts of other radioactive waste, such as that associated with medical treatments.

Related: How do you decontaminate objects exposed to radioactivity?

Waste from weapons manufacturing

Remnants of the chemical processing of radioactive material needed to manufacture nuclear weapons, often called "defense waste," will eventually be melted along with glass, with the resulting material poured into stainless steel containers. These canisters are 10 feet tall and 2 feet in diameter, weighing approximately 5,000 pounds when filled.

For now, though, most of it is stored in underground steel tanks, primarily at Hanford, Washington, and Savannah River, South Carolina, key sites in U.S. nuclear weapons development. At Savannah River, some of the waste has already been processed with glass, but much of it remains untreated.

At both of those locations, some of the radioactive waste has already leaked into the soil beneath the tanks, though officials have said there is no danger to human health. Most of the current efforts to contain the waste focus on protecting the tanks from corrosion and cracking to prevent further leakage.

Waste from electricity generation

The vast majority of nuclear waste in the U.S. is spent nuclear fuel from commercial nuclear power plants.

Before it is used, nuclear fuel exists as uranium oxide pellets that are sealed within zirconium tubes, which are themselves bundled together. These bundles of fuel rods are about 12 to 16 feet long and about 5 to 8 inches in diameter. In a nuclear reactor, the fission reactions fueled by the uranium in those rods emit heat that is used to create hot water or steam to drive turbines and generate electricity.

After about three to five years, the fission reactions in a given bundle of fuel slow down significantly, even though the material remains highly radioactive. The spent fuel bundles are removed from the reactor and moved elsewhere on the power plant's property, where they are placed into a massive pool of water to cool them down.

After about five years, the fuel bundles are removed, dried and sealed in welded stainless steel canisters. These canisters are still radioactive and thermally hot, so they are stored outdoors in concrete vaults that sit on concrete pads, also on the power plant's property. These vaults have vents to ensure air flows past the canisters to continue cooling them.

As of December 2024, there were over 315,000 bundles of spent nuclear fuel rods in the U.S., and over 3,800 dry storage casks in concrete vaults above ground, located at current and former power plants across the country.

Even reactors that have been decommissioned and demolished still have concrete vaults storing radioactive waste, which must be secured and maintained by the power company that owned the nuclear plant.

The threat of water

One threat to these storage methods is corrosion.

Because they need water to both transfer nuclear energy into electricity and to cool the reactor, nuclear power plants are always located alongside sources of water.

In the U.S., nine are within two miles of the ocean, which poses a particular threat to the waste containers. As waves break on the coastline, saltwater is sprayed into the air as particles. When those salt and water particles settle on metal surfaces, they can cause corrosion, which is why it's common to see heavily corroded structures near the ocean.

At nuclear waste storage locations near the ocean, that salt spray can settle on the steel canisters. Generally, stainless steel is resistant to corrosion, which you can see in the shiny pots and pans in many Americans' kitchens. But in certain circumstances, localized pits and cracks can form on stainless steel surfaces.

In recent years, the U.S. Department of Energy has funded research, including my own, into the potential dangers of this type of corrosion. The general findings are that stainless steel canisters could pit or crack when stored near a seashore. But a radioactive leak would require not only corrosion of the container but also of the zirconium rods and of the fuel inside them. So it is unlikely that this type of corrosion would result in the release of radioactivity.

A long way off

A more permanent solution is likely years, or decades, away.

Not only must a long-term site be geologically suitable to store nuclear waste for thousands of years, but it must also be politically palatable to the American people. In addition, there will be many challenges associated with transporting the waste, in its containers, by road or rail, from reactors across the country to wherever that permanent site ultimately is.

Perhaps there will be a temporary site whose location passes muster with the Supreme Court. But in the meantime, the waste will stay where it is.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

The first nuclear weapon test, code-named "Trinity," took place in the New Mexico desert at 5:30 a.m. on July 16, 1945. This test was a proof of concept for the secret nuclear science taking place at Los Alamos as a part of the Manhattan Project during World War II and would lead to the atomic bombs being dropped on Hiroshima and Nagasaki, Japan, just a few weeks later.

Since those detonations, the development of nuclear weapons has accelerated. Countries around the world have built their own nuclear stockpiles, including over 5,000 nuclear warheads held by the U.S.

Yet, even though the basic components of this technology are no longer secret, nuclear weapon development remains a scientific and engineering challenge. But why are nuclear weapons still so difficult to produce?

A big part of the difficulty comes from deriving the chemical elements used inside these weapons to create an explosion, Hans Kristensen, director of the Nuclear Information Project at the Federation of American Scientists, told Live Science in an email.

"That basic idea of a nuclear explosion is that nuclear [fissile] materials are stimulated to release their enormous energy," he said. "To produce fissile material of sufficient purity and sufficient quantity is a challenge [and] this production requires considerable industrial capacity."

Related: How many nuclear bombs have been used?

The enormous release of energy is called a nuclear fission reaction. When this reaction occurs, a chain reaction starts where the atoms are split apart to release energy. This is the same kind of reaction that makes nuclear energy possible.

Uranium and plutonium enrichment

The fissile material inside a nuclear bomb is primarily isotopes of uranium and plutonium, which are radioactive elements, Matthew Zerphy, a professor of practice in nuclear engineering at Penn State, told Live Science. Natural uranium consists of different isotopes, including a large amount of uranium-238 (U-238) and a smaller amount of uranium-235 (U-235), which is more readily fissionable. To access this more fissionable isotope, uranium ore is mined and then goes through several processes for "enrichment" in which the U-235 concentration is increased so that it can be used for nuclear weapons.

"One way to enrich uranium is to turn it into a gas and spin it very rapidly in centrifuges," Zerphy said. "Because of the difference in mass between U-235 and U-238, the isotopes are split, and you can separate out U-235."

For weapons-grade uranium, this separation continues up to concentrations of over 90% U-235, Zerphy said. The most challenging part of this process, which can take weeks to months, is the chemical transformation of the element itself, which requires intensive energy and specialized equipment. One chemical hazard during this process is the possible release of uranium hexafluoride (UF₆), a highly toxic substance that, if inhaled, can damage the kidneys, liver, lungs, brain, skin and eyes.

The process to produce weapons-grade plutonium is even trickier, he said, because this element does not occur naturally like uranium does. Instead, plutonium is a byproduct of nuclear reactors using uranium fuel, which means to produce plutonium, scientists need to handle radioactive, spent nuclear fuel and process the material through "intense" chemical processing. The processing of this material can also pose a safety risk if a critical mass is collected accidentally, Zerphy said, which is the smallest amount of fissile material needed to sustain a self-sustaining fission reaction.

"You'd be very careful to not have that happen while you're in the process of making these components to make sure that things aren't inadvertently brought together and entering some kind of criticality," he said, which could lead to an accidental explosion.

Related: Why did the atomic bomb dropped on Hiroshima leave shadows of people etched on sidewalks?

Although the scientific principles of bringing these components together is well understood, creating and controlling this reaction in a fraction of a second can still be difficult.

"The weapons are designed such that when they are detonated a 'supercritical' mass of fissile material is created very quickly … in a very small space," Zerphy said. "This causes an exponential increase in the number of fissions spreading throughout the material almost instantaneously."

This quick spread of atomic fission is a big part of what makes a nuclear reaction so destructive, he said.

In the case of thermonuclear weapons, which were developed after World War II and use a combination of both nuclear fission and fusion to create an even stronger explosion, a standard fission reaction then has to spark a secondary and stronger fusion reaction. This fusion reaction is the same kind of power found at the center of the sun.

Nuclear weapons testing

Once these weapons are created, scientists and engineers need to be sure the weapons will work as needed, should they ever be used. When nuclear weapons were first developed, scientists would test the weapons themselves at test sites (which devastated the environment of the "deserted" areas where they were tested, as well as people and animals that lived nearby). In contrast, modern weapon testing relies on computer models. This is part of the work done by the National Nuclear Security Administration (NNSA).

"NNSA … develop[s] tools for qualifying weapon components and certifying weapons, ensuring their survivability and effectiveness in various scenarios," an NNSA spokesperson told Live Science in an email. "This involves advanced simulations using supercomputing systems, materials science, and precision engineering to ensure weapons function as intended."

Ultimately, the complexity and challenges of building these weapons may explain why so few nuclear superpowers exist in the world today.

Editor's note: This article was updated at 12:54 p.m. ET on March 20 to note that nuclear weapons have nuclear reactions, not chemical ones, as was previously stated in the top image caption. It was updated again at 7:05 p.m. ET on March 31 to clarify how natural uranium is enriched to increase U-235 concentrations.

Periodic table of elements quiz: How many elements can you name in 10 minutes?

Scientists have developed an innovative battery that converts energy from radioactive waste into electricity, transforming a hazardous by-product of nuclear power generation into a potential energy source for specialized applications.

Nuclear power plants generate 18% of electricity in the United States, according to the World Nuclear Association. While this energy source produces no carbon emissions, it does generate radioactive waste that can be environmentally hazardous and remains active for thousands of years.

Seeking to repurpose this waste, a research team from Ohio State University used high-density materials that emit light when absorbing radiation called scintillator crystals combined with solar cells to convert gamma radiation into electricity.

“Nuclear waste emits powerful gamma radiation, a high-energy form that can penetrate most materials,” Raymond Cao, lead author of the study published in the journal Optical Materials: X and a professor in mechanical and aerospace engineering at Ohio State, told Live Science in an email. “Our device employs a scintillator, a specialized material that absorbs these gamma rays and converts their energy into visible light — similar to how glow-in-the-dark objects function, but driven by radiation rather than sunlight. This light is then captured by a solar cell, like those found in solar panels, which transforms it into electrical power.”

The prototype battery, measuring just 4 cubic centimeters — about the size of a teaspoon of sugar — was tested at Ohio State’s Nuclear Reactor Laboratory using two radioactive sources: cesium-137 and cobalt-60. The battery produced 288 nanowatts of power when powered by cesium-137 and 1,500 nanowatts when using the more radioactive cobalt-60 isotope — enough to operate microelectronic systems such as microchips or emergency equipment.

Related: Why radioactive waste is being melted into glass

While this output is far below the kilowatts needed to power your kettle, the researchers believe this technology could be scaled up for applications at or beyond the watts level with the right power source.

Regardless, the new technology wouldn’t be used in homes — the system relies on high levels of ambient radiation to operate, so would need to be in situ at waste sites. For example, the researchers envision the battery being deployed in nuclear systems for space and deep-sea exploration, where extreme radiation levels render conventional power sources impractical.

“We do not produce or carry a radiation source; instead, this device is designed for locations where intense gamma radiation is already present,” Cao said. “The beauty of this approach is that shielding materials can be replaced with a scintillator, and the glowing light it produces can be harvested and converted into electricity.”

Before it’s rolled out, however, a few hurdles remain. According to Cao, the high levels of radiation gradually damage both the scintillator and the solar cell. “Further development is needed for more durable, radiation-resistant materials to ensure the system’s longevity,” he said.

If overcome, these long-lasting batteries could be deployed in high-radiation areas that are difficult to access, with little to no maintenance required, making them an attractive energy solution.

“The nuclear battery concept is very promising,” co-author Ibrahim Oksuz said in a statement. “There's still lots of room for improvement, but I believe in the future, this approach will carve an important space for itself in both the energy production and sensors industry.”

China's "artificial sun" reactor has broken its own world record for maintaining super-hot plasma, marking another milestone in the long road towards near-limitless clean energy.

The Experimental Advanced Superconducting Tokamak (EAST) nuclear fusion reactor maintained a steady, highly confined loop of plasma — the high-energy fourth state of matter — for 1,066 seconds on Monday (Jan. 20), which more than doubled its previous best of 403 seconds, Chinese state media reported.

Nuclear fusion reactors are nicknamed "artificial suns" because they generate energy in a similar way to the sun — by fusing two light atoms into a single heavy atom via heat and pressure. The sun has a lot more pressure than Earth's reactors, so scientists compensate by using temperatures that are many times hotter than the sun.

Nuclear fusion offers the potential of a near-unlimited power source without greenhouse gas emissions or much nuclear waste. However, scientists have been working on this technology for more than 70 years, and it's likely not progressing fast enough to be a practical solution to the climate crisis. Researchers expect us to have fusion power within decades, but it could take much longer.

EAST's new record won't immediately usher in what is dubbed the "Holy Grail" of clean power, but it is a step towards a possible future where fusion power plants generate electricity.

East is a magnetic confinement reactor, or tokamak, designed to keep the plasma continuously burning for prolonged periods. Reactors like this have never achieved ignition, which is the point at which nuclear fusion creates its own energy and sustains its own reaction, but the new record is a step towards maintaining prolonged, confined plasma loops that future reactors will need to generate electricity.

"A fusion device must achieve stable operation at high efficiency for thousands of seconds to enable the self-sustaining circulation of plasma, which is critical for the continuous power generation of future fusion plants," Song Yuntao, director of the Institute of Plasma Physics responsible for the fusion project at the Chinese Academy of Sciences, told Chinese state media.

Related: Nuclear fusion could be the clean energy of the future — but these 'tough' challenges stand in the way

EAST is one of several nuclear fusion reactors worldwide, but they all currently use far more energy than they produce. In 2022, the U.S. National Ignition Facility's fusion reactor briefly achieved ignition in its core using a different experimental method to EAST, relying on quick bursts of energy, but the reactor as a whole still used more energy than it consumed.

Tokamaks like EAST are the most common nuclear fusion reactors. EAST heats up plasma and traps it inside a donut-shaped reactor chamber — called the tokamak — with powerful magnetic fields. For the latest record, researchers made several upgrades to the reactor, including doubling the power of its heating system, according to Chinese state media.

The data gathered by EAST will support the development of other reactors, both in China and internationally. China is part of the International Thermonuclear Experimental Reactor (ITER) program, which involves dozens of countries, including the U.S., U.K. Japan, South Korea and Russia.

The ITER reactor, which is being built in southern France, contains the world's most powerful magnet and will fire up in 2039 at the earliest. ITER will be an experimental tool designed to create sustained fusion for research purposes, but could pave the way for fusion power plants.

"We hope to expand international collaboration via EAST and bring fusion energy into practical use for humanity," Song said.

The way scientists think about fusion changed forever in 2022, when what some called the experiment of the century demonstrated for the first time that fusion can be a viable source of clean energy.

The experiment, at Lawrence Livermore National Laboratory, showed ignition: a fusion reaction generating more energy out than was put in.

In addition, the past few years have been marked by a multibillion-dollar windfall of private investment in the field, principally in the United States.

But a whole host of engineering challenges must be addressed before fusion can be scaled up to become a safe, affordable source of virtually unlimited clean power. In other words, it's engineering time.

As engineers who have been working on fundamental science and applied engineering in nuclear fusion for decades, we've seen much of the science and physics of fusion reach maturity in the past 10 years.

But to make fusion a feasible source of commercial power, engineers now have to tackle a host of practical challenges. Whether the United States steps up to this opportunity and emerges as the global leader in fusion energy will depend, in part, on how much the nation is willing to invest in solving these practical problems — particularly through public-private partnerships.

Related: Nuclear fusion reactor in UK sets new world record for energy output

Building a fusion reactor

Fusion occurs when two types of hydrogen atoms, deuterium and tritium, collide in extreme conditions. The two atoms literally fuse into one atom by heating up to 180 million degrees Fahrenheit (100 million degrees Celsius), 10 times hotter than the core of the sun. To make these reactions happen, fusion energy infrastructure will need to endure these extreme conditions.

There are two approaches to achieving fusion in the lab: inertial confinement fusion, which uses powerful lasers, and magnetic confinement fusion, which uses powerful magnets.

While the "experiment of the century" used inertial confinement fusion, magnetic confinement fusion has yet to demonstrate that it can break even in energy generation.

Several privately funded experiments aim to achieve this feat later this decade, and a large, internationally supported experiment in France, ITER, also hopes to break even by the late 2030s. Both are using magnetic confinement fusion.

Challenges lying ahead

Both approaches to fusion share a range of challenges that won't be cheap to overcome. For example, researchers need to develop new materials that can withstand extreme temperatures and irradiation conditions.

Fusion reactor materials also become radioactive as they are bombarded with highly energetic particles. Researchers need to design new materials that can decay within a few years to levels of radioactivity that can be disposed of safely and more easily.

Producing enough fuel, and doing it sustainably, is also an important challenge. Deuterium is abundant and can be extracted from ordinary water. But ramping up the production of tritium, which is usually produced from lithium, will prove far more difficult. A single fusion reactor will need hundreds of grams to one kilogram (2.2 lbs.) of tritium a day to operate.

Right now, conventional nuclear reactors produce tritium as a byproduct of fission, but these cannot provide enough to sustain a fleet of fusion reactors.

So, engineers will need to develop the ability to produce tritium within the fusion device itself. This might entail surrounding the fusion reactor with lithium-containing material, which the reaction will convert into tritium.

To scale up inertial fusion, engineers will need to develop lasers capable of repeatedly hitting a fusion fuel target, made of frozen deuterium and tritium, several times per second or so. But no laser is powerful enough to do this at that rate — yet. Engineers will also need to develop control systems and algorithms that direct these lasers with extreme precision on the target.

Additionally, engineers will need to scale up production of targets by orders of magnitude: from a few hundreds handmade every year with a price tag of hundreds of thousands of dollars each to millions costing only a few dollars each.

For magnetic containment, engineers and materials scientists will need to develop more effective methods to heat and control the plasma and more heat- and radiation-resistant materials for reactor walls. The technology used to heat and confine the plasma until the atoms fuse needs to operate reliably for years.

These are some of the big challenges. They are tough but not insurmountable.

Current funding landscape

Investments from private companies globally have increased — these will likely continue to be an important factor driving fusion research forward. Private companies have attracted over US$7 billion in private investment in the past five years.

Several startups are developing different technologies and reactor designs with the aim of adding fusion to the power grid in coming decades. Most are based in the United States, with some in Europe and Asia.

While private sector investments have grown, the U.S. government continues to play a key role in the development of fusion technology up to this point. We expect it to continue to do so in the future.

It was the U.S. Department of Energy that invested about US$3 billion to build the National Ignition Facility at the Lawrence Livermore National Laboratory in the mid 2000s, where the "experiment of the century" took place 12 years later.

In 2023, the Department of Energy announced a four-year, $42 million program to develop fusion hubs for the technology. While this funding is important, it likely will not be enough to solve the most important challenges that remain for the United States to emerge as a global leader in practical fusion energy.

One way to build partnerships between the government and private companies in this space could be to create relationships similar to that between NASA and SpaceX. As one of NASA's commercial partners, SpaceX receives both government and private funding to develop technology that NASA can use. It was the first private company to send astronauts to space and the International Space Station.

Along with many other researchers, we are cautiously optimistic. New experimental and theoretical results, new tools and private sector investment are all adding to our growing sense that developing practical fusion energy is no longer an if but a when.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Nuclear fusion technology could get a breakthrough from an unexpected place: mayonnaise.

In a new study, published in May in the journal Physical Review E, scientists plopped the creamy condiment into a churning wheel machine and set it whirling to see what conditions made it flow.

"We use mayonnaise because it behaves like a solid, but when subjected to a pressure gradient, it starts to flow," study lead author Arindam Banerjee, a mechanical engineer at Lehigh University in Pennsylvania, said in a statement.

This process could help elucidate the physics that occur at ultrahigh temperatures and pressures inside nuclear fusion reactors — without having to create those extreme conditions.

Related: World's largest nuclear fusion reactor is finally completed. But it won't run for another 15 years.

Nuclear fusion forges helium from hydrogen at the hearts of stars. In theory, it could be the source of nearly limitless clean energy on Earth — if the reaction could produce more energy than it requires to run.

That's a tall order; star-powered fusion occurs at 27 million degrees Fahrenheit (15 million degrees Celsius), according to NASA. And a star's massive gravity forces hydrogen atoms together, overcoming their natural repulsion. On Earth, however, we don't have those crushing pressures, so human-made fusion reactors must run 10 times hotter than the sun.

To reach these mind-melting temperatures, scientists use multiple approaches, including one called inertial confinement.

In this process, physicists freeze pea-sized pellets of gas — typically a mix of heavy isotopes, or versions, of hydrogen — into metal capsules. Then, they blast the pellets with lasers, which heats the gas to 400 million F (222 million C) in a flash — and, ideally, turns it into a plasma where fusion can occur, according to the statement.

Unfortunately, the hydrogen gas wants to expand, causing the molten metal to explode before hydrogen has time to fuse. This explosion occurs when the metal capsule enters an unstable phase and starts to flow.

Banerjee's team realized that molten metal behaves a lot like mayonnaise at lower temperatures: It can be elastic, meaning it bounces back when you push on it, or plastic, meaning it doesn't bounce back, or flowing.

"If you put a stress on mayonnaise, it will start to deform, but if you remove the stress, it goes back to its original shape," he said. "So there's an elastic phase followed by a stable plastic phase. The next phase is when it starts flowing, and that's where the instability kicks in."

In the new study, the researchers placed mayonnaise in a machine that accelerated the egg-and-oil emulsion until it started to flow. Then, they characterized the conditions at which the condiment transitioned between plastic, elastic and unstable states.

"We found the conditions under which the elastic recovery was possible, and how it could be maximized to delay or completely suppress the instability," Banerjee said.

The study also found which conditions allowed for more energy yield.

Of course, mayonnaise and ultrahot metal capsules are different in many ways. So it remains to be seen whether the team's findings can be translated to a pellet of plasma many times hotter than the sun.

A nuclear reactor in the U.K. has just broken a new fusion record. 

In a news conference today (Feb. 8), representatives from the Joint European Torus (JET) facility declared that the reactor's final tests yielded 69.26 megajoules of heat from just 0.21 milligrams of fuel — the equivalent of burning 4.4 pounds (2 kilograms) of coal. This is more total energy — though not more net positive energy — than any other fusion reaction has produced thus far. 

Tests such as this could help unlock fusion as a viable source of clean, near-limitless energy, the researchers said.

JET first fired up in 1983 in Oxfordshire, England. Its doughnut-like shape, known as a tokamak, allows scientists to whip modified hydrogen atoms into hot plasma by accelerating them to breathtaking speeds using a magnetic field. This setup creates the necessary conditions for nuclear fusion — the combination of two light atomic nuclei into one heavier one, releasing enormous amounts of energy in the process.

Over the course of its 40 years of operation, JET has produced numerous fusion milestones, including becoming the first reactor to use a 50/50 mixture of deuterium (hydrogen with an extra neutron) and tritium (hydrogen with two extra neutrons) atoms — now considered a standard fusion fuel. 

"We can reliably create fusion plasmas using the same fuel mixture to be used by commercial fusion energy powerplants, showcasing the advanced expertise developed over time," Fernanda Rimini, JET's scientific operations leader, said in a statement. 

Related: Nuclear fusion reactor 'breakthrough' is significant, but light-years away from being useful

However, this record will be JET's last. The project was decommissioned in December 2023, shortly after the record-breaking test took place. Researchers have now begun the arduous process of taking the reactor apart, a task that is expected to last until 2040. But over that time, they hope to learn even more about what made JET tick, including how renegade plasma blasts affected the tokamak's internal structure. It will also help scientists develop safer strategies to dispose of radioactive waste, the team said.

JET's legacy will live on in the International Thermonuclear Experimental Reactor (ITER), a massive tokamak in southern France scheduled to start up in 2025. The $22 billion dollar project will use a very similar fusion strategy, but at a much larger scale. 

"Throughout its lifecycle, JET has been remarkably helpful as a precursor to ITER," Pietro Barabaschi, ITER's director-general, said in the statement. "The results obtained here will directly and positively impact ITER, validating the way forward and enabling us to progress faster toward our performance goals once operation begins."

Scientists in the U.K. have created mini, seed-sized nuclear fuel cells that could power futuristic flower-shaped reactors on the moon as soon as 2030.

The tiny new fuel cells, developed by researchers at the Nuclear Futures Institute at Bangor University in Wales, are roughly the size of poppy seeds, which are around 0.04 inch (1 millimeter) across. The mini pellets are a type of tri-structural isotropic particle (TRISO) fuel, which is made from uranium, carbon and oxygen surrounded by a hard, ceramic-like shell. The cells are much more durable and efficient than traditional nuclear fuels, which makes them perfect for space exploration.

The fuel cells are designed to power the Space Flower Moon Micro Reactor, a conceptual car-sized fusion reactor designed by Rolls-Royce. Funding for the reactor was secured in early March, and the design is a leading candidate to power future moon bases as a part of NASA's Artemis program, which aims to establish a permanent base on the moon by 2030. Researchers think one of the durable pellets could power a single reactor for up to 15 years.

The fuel cells have now been sent to NASA for testing, which will simulate how the nuclear pellets deal with the simulated forces of a rocket launch and whether they are as efficient as the researchers claim, according to the BBC.

Related: How long would it take to walk around the moon?

Reliable power sources will be crucial for future moon bases because solar power cannot be relied upon at night, when temperatures plummet below minus 200 degrees Fahrenheit (minus 129 degrees Celsius) and vast amounts of energy will be needed to heat living quarters and vital infrastructure.

"On the moon and on planetary bodies that have day and night, we can no longer rely on the Sun for energy and therefore must design systems such as the small micro-reactor to sustain life," project researcher Simon Middleburgh, a nuclear materials expert at Bangor University, said in a statement.

Nuclear reactors are the only current viable option for creating a reliable power source on such a short timescale, Middleburgh said. However, "the fuel must be extremely robust and survive the forces of launch and then be dependable for many years," he added.

The shells of TRISO fuels withstand corrosion, oxidation and high temperatures, and prevent radiation from leaking from the fuel, all of which may arise in space, according to the U.S. Department of Energy.

In addition to being robust enough to survive the journey to the moon, a main attraction of TRISO fuels is that they are extremely small, which makes them much more cost-effective to launch into space.

Although the mini reactor is designed primarily for space exploration, it could also provide a temporary source of reliable energy in areas affected by natural disasters such as earthquakes, tsunamis and tropical storms, the researchers said.

NASA isn't the only entity with its eyes on the moon. On Aug. 23, India's Chandrayaan-3 spacecraft landed near the moon's south pole in search of resources for a future lunar base. And in 2021, China and Russia announced plans to develop a joint base on the moon, although this project has suffered a recent setback after Russia's Luna 25 lander crash-landed on the moon last month.

In the early morning hours of April 26, 1986, the Chernobyl Nuclear Power Plant in Ukraine (formerly part of the Soviet Union) exploded, creating what many consider the worst nuclear disaster the world has ever seen.

Even after many years of scientific research and government investigation, there are still many unanswered questions about the Chernobyl accident — especially regarding the long-term health impacts that the massive radiation leak will have on those who were exposed. 

Related: 5 weird things you didn't know about Chernobyl

Where is Chernobyl?

The Chernobyl Nuclear Power Plant is located about 81 miles (130 kilometers) north of the Ukrainian capital, Kyiv, and about 12 miles (20 km) south of the border with Belarus, according to the World Nuclear Association. It is made up of four reactors that were designed and built during the 1970s and 1980s. A human-made reservoir, roughly 8.5 square miles (22 sq. km) in size and fed by the Pripyat river, was created to provide cooling water for the reactor.

The city of Pripyat, founded in 1970, was the nearest town to the power plant at just under 2 miles (3 km) away and housed almost 50,000 people in 1986. A smaller and older town, Chernobyl, was about 9 miles (15 km) away and home to about 12,000 residents. The remainder of the region was primarily farms and woodland.

Chernobyl nuclear power plant

The Chernobyl plant used four Soviet-designed RBMK-1000 nuclear reactors — a design that's now universally recognized as inherently flawed. RBMK reactors were of a pressure tube design that used an enriched U-235 uranium dioxide fuel to heat water, creating steam that drives the reactors' turbines and generates electricity, according to the World Nuclear Association.

In most nuclear reactors, water is also used as a coolant and to moderate the reactivity of the nuclear core by removing the excess heat and steam, according to the World Nuclear Association. But the RBMK-1000 used graphite to moderate the core's reactivity and to keep a continuous nuclear reaction occurring in the core. As the nuclear core heated and produced more steam bubbles, the core became more reactive, not less, creating a positive-feedback loop that engineers refer to as a "positive-void coefficient."

What happened at Chernobyl?

The explosion occurred on April 26, 1986, during a routine maintenance check, according to the U.N. Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Operators were planning to test the electrical systems when they turned off vital control systems, going against the safety regulations. This caused the reactor to reach dangerously unstable and low-power levels.

Reactor 4 had been shut down the day before in order to perform the maintenance checks to safety systems during potential power outages, according to the Nuclear Energy Agency (NEA). While there is still some disagreement over the actual cause of the explosion, it is generally believed that the first was caused by an excess of steam and the second was influenced by hydrogen. The excess steam was created by the reduction of the cooling water, which caused steam to build up in the cooling pipes — the positive-void coefficient — which caused an enormous power surge that the operators could not shut down.

The explosions occurred at 1:23 a.m. on April 26, destroying reactor 4 and initiating a booming fire, according to the NEA. Radioactive debris of fuel and reactor components rained over the area while fire spread from the building housing reactor 4 to adjacent buildings. Toxic fumes and dust were carried by the blowing wind, bringing fission products and the noble gas inventory of naturally-occurring odorless and colorless gases with it.

Radioactive fallout

The explosions killed two plant workers — the first of several workers to die within hours of the accident. For the next several days, as emergency crews tried desperately to contain the fires and radiation leaks, the death toll climbed as plant workers succumbed to acute radiation sickness.

The initial fire was stifled by about 5 a.m., but the resulting graphite-fueled fire took 10 days and 250 firefighters to extinguish, according to the NEA. However, toxic emissions continued to be pumped into the atmosphere for an additional 10 days.

Most of the radiation released from the failed nuclear reactor was from fission products iodine-131, cesium-134 and cesium-137. Iodine-131 has a relatively short half-life of eight days, according to UNSCEAR, but it is rapidly ingested through the air and tends to localize in the thyroid gland. Cesium isotopes have longer half-lives (cesium-137 has a half-life of 30 years) and are a concern for years after their release into the environment.

Evacuations of Pripyat commenced on April 27 — about 36 hours after the accident had occurred. By that time, many residents were already complaining about vomiting, headaches and other signs of radiation sickness. Officials closed off an 18-mile (30 km) area around the plant by May 14, evacuating another 116,000 residents. Within the next few years, 220,000 more residents were advised to move to less contaminated areas, according to the World Nuclear Association. 

Related: Images: Chernobyl, frozen in time

Effects of Chernobyl on humans

Twenty-eight of the workers at Chernobyl died in the first four months following the accident, according to the U.S. Nuclear Regulatory Commission (NRC), including some heroic workers who knew they were exposing themselves to deadly levels of radiation in order to secure the facility from further radiation leaks.

The prevailing winds at the time of the accident were from the south and east, so much of the radiation plume traveled northwest toward Belarus. Nonetheless, Soviet authorities were slow to release information about the severity of the disaster to the outside world. But when radiation levels raised concern in Sweden about three days later, scientists there were able to conclude the approximate location of the nuclear disaster based on radiation levels and wind directions, forcing Soviet authorities to reveal the full extent of the crisis, according to the United Nations.

Within three months of the Chernobyl accident, a total of 31 people died from radiation exposure or other direct effects of the disaster, according to the NRC. Between 1991 and 2015, as many as 20,000 cases of thyroid cancer cases were diagnosed in patients who were under the age of 18 in 1986, according to a 2018 UNSCEAR report. While there may still be additional cases of cancer that emergency workers, evacuees and residents may experience throughout their lifetimes, the known overall rate of cancer deaths and other health effects directly related to Chernobyl's radiation leak is lower than was initially feared. "The majority of the five million residents living in contaminated areas … received very small radiation doses comparable to natural background levels (0.1 rem per year)," according to an NRC report. "Today, the available evidence does not strongly connect the accident to radiation-induced increases of leukemia or solid cancer, other than thyroid cancer."

Some experts have claimed that unsubstantiated fear of radiation poisoning led to greater suffering than the actual disaster. For example, many doctors throughout Eastern Europe and the Soviet Union advised pregnant women to undergo abortions to avoid bearing children with birth defects or other disorders, though the actual level of radiation exposure these women experienced was likely too low to cause any problems, according to the World Nuclear Association. In 2000, the United Nations published a report on the effects of the Chernobyl accident that was so "full of unsubstantiated statements that have no support in scientific assessments," according to the chairman of UNSCEAR, that it was eventually dismissed by most authorities.

Chernobyl's effect on the environment

Shortly after the radiation leaks from Chernobyl occurred, the trees in the woodlands surrounding the plant were killed by high levels of radiation. This region came to be known as the "Red Forest" because the dead trees turned a bright ginger color. The trees were eventually bulldozed and buried in trenches, according to the National Science Research Laboratory at Texas Tech University.

The damaged reactor was hastily sealed in a concrete sarcophagus intended to contain the remaining radiation, according to the NRC. However, there is ongoing intense scientific debate over how effective this sarcophagus has been and will continue to be into the future. An enclosure called the New Safe Confinement structure began construction in late 2006 after stabilizing the existing sarcophagus. The new structure, completed in 2017, is 843 feet (257 meters) wide, 531 feet (162 m) long, and 356 feet (108 m) tall and designed to completely enclose reactor 4 and its surrounding sarcophagus for at least the next 100 years, according to World Nuclear News.

Despite the contamination of the site — and the inherent risks in operating a reactor with serious design flaws — the Chernobyl nuclear plant continued operation to meet the power needs of Ukraine until its last reactor, reactor 3, was shut down in December 2000, according to World Nuclear News. Reactors 2 and 1 were shut down in 1991 and 1996, respectively. Complete decommissioning of the site is expected to be completed by 2028.

The plant, the ghost towns of Pripyat and Chernobyl, and the surrounding land make up a 1,000-square-mile (2600 square kilometers) "exclusion zone," which is restricted to nearly everyone except for scientists and government officials.

Despite the dangers, several people returned to their homes shortly after the disaster, with some sharing their stories with news sources such as the BBC, CNN and The Guardian. And in 2011, Ukraine opened up the area to tourists wanting to see the after-effects of the disaster firsthand.

Chernobyl today

Today, the region, including within the Chernobyl exclusion zone, is filled with a variety of wildlife that have thrived without interference from humans, according to National Geographic. Thriving populations of wolves, deer, lynx, beaver, eagles, boar, elk, bears and other animals in Chernobyl have been documented in the dense woodlands that now surround the silent power plant. Nonetheless, a handful of radiation effects, such as stunted trees growing in the zone of highest radiation and animals with high levels of cesium-137 in their bodies, are known to occur. 

Related: Infographic: Chernobyl nuclear disaster 25 years later

The area has recovered to some extent, but is far from returning to normal. But in the areas just outside the exclusion zone, people are beginning to resettle. Tourists continue to visit the site, with visitation rates jumping 30% to 40% thanks to a 2019 HBO series based on the disaster. And the catastrophe that occurred at Chernobyl resulted in a few significant changes for the nuclear industry: concern about reactor safety increased in eastern Europe as well as around the world; the remaining RBMK reactors were modified to reduce the risk in another disaster; and many international programs including the International Atomic Energy Agency (IAEA) and the World Association of Nuclear Operators (WANO) were founded as a direct result of Chernobyl, according to the World Nuclear Association. And around the globe, experts have continued researching ways to prevent future nuclear disasters.

Russian invasion

On Feb. 24, 2022, during a full invasion of Ukraine ordered by Russian president Vladimir Putin, Russian troops captured the Chernobyl Nuclear Power Plant, taking its staff hostage. 

Just a day later (Feb. 25), after heavy fighting between Ukrainian and Russian forces, increased radiation levels were detected at the power plant, according to Ukrainian officials and online data from Chernobyl exclusion zone's automated radiation-monitoring system. Gamma radiation, a high-energy type of electromagnetic radiation, increased 20 times above typical levels at multiple inspection points. This radiation spike was likely due to radioactive dust that was thrown into the air due to nearby disturbances from war equipment and fighting. 

"If it's a resuspension of dust, this is generally stuff that was not that mobile, or it would have blown away," Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists, previously told Live Science. "So it's probably heavier particles of soil that don't disperse very far."

Even with this radiation spike however, "the dose rates they're finding are not that much greater than the usual dose rates in that area, which, admittedly, are probably about a hundred times the background dose of anywhere else in the world," Lyman said. "But even so, if [the troops] don't spend that much time in the area, it's not going to have a significant impact on their health compared to the threat of dying in war."

The IAEA released a statement on Feb. 24 saying that it was following the situation at the power plant with "grave concern." Rafael Mariano Grossi, IAEA director general, appealed for "maximum restraint to avoid any action that may put the country's nuclear facilities at risk," according to the statement.

At the IAEA General Conference in 2009, the organization's member states (which includes Russia) adopted a decision stating "any armed attack on and threat against nuclear facilities devoted to peaceful purposes constitutes a violation of the principles of the United Nations Charter, international law and the Statute of the Agency," Grossi noted.

On March 9, Ukraine's state energy company announced that Chernobyl's nuclear power plant and all the facilities in the exclusion zone had been completely disconnected and were without electricity. This led Ukrainian officials to express their concern that the spent nuclear material kept in the plant's cooling pools could heat up and evaporate into its immediate surroundings. But nuclear energy experts cautioned that the plant's roughly 20,000 spent nuclear fuel units, which are 22 years old, were fairly cold and that an event of this kind would be highly unlikely.

"The spent fuel rods are at minimum 22 years old. They have very little heat to dissipate," Mark Nelson, the managing director of the Radiant Energy Fund, which advises companies and nonprofits about nuclear energy, wrote on Twitter. "Their heat is low enough that experts I've talked to expect weeks or even months to heat the water enough to dry out the pool. Even then, natural air circulation should be sufficient."

Sometime during the Russian occupation, looters stole radioactive material and isotopes from a radiation monitoring laboratory near the defunct nuclear power plant, according to the Institute for Safety Problems of Nuclear Power Plants (ISPNPP). As it contains no plutonium or uranium, the stolen material cannot be used to make nuclear weapons, but it could possibly make a dirty bomb, although this risk is also low, Live Science previously reported. 

On March 31, Ukraine's state nuclear company Energoatom announced that Russian troops had left the plant, taking a small number of the plant's Ukrainian security officers with them. Russian troops evacuated the area after a failed attempt to capture the nearby Ukrainian capital of Kyiv. The rest of the plant's hostaged workers, who had been forced to maintain the plant under gunpoint, were freed. Energoatom also said that Russian soldiers had dug a number of trenches in the radioactively contaminated soil in the Red Forest, leading to unconfirmed speculation that some of the invaders had contracted radiation sickness. 

Additional resources

Read more about how water cools and moderates nuclear reactors from the International Atomic Energy Agency. Or find the latest news about the Chernobyl Nuclear Power Plant on the power plant's website. To learn about longstanding health effects from the Chernobyl disaster, go to the Canadian Safety Nuclear Commission.

Bibliography

World Nuclear Association. "Chernobyl Accident 1986" Updated May 2021.

World Nuclear Association. "Cooling Power Plants." Updated September 2020.

United Nations Scientific Committee on the Effects of Atomic Radiation. "The Chernobyl accident." Updated April 2021.

Nuclear Energy Agency. "Chapter I The site and accident sequence." Updated 2002.

U.S. Nuclear Regulatory Commission. "Backgrounder on Chernobyl Nuclear Power Plant Accident." Updated/reviewed August 2018.

United Nations. "International Chernobyl Disaster Remembrance Day 26 April." 

United Nations Scientific Committee on the Effects of Atomic Radiation. "Evaluation of Data on Thyroid Cancer in Regions Affected by the Chernobyl Accident." 2018.

Lars-Erik Holm. The Lancet. July 22, 2000.

National Science Research Laboratory. "Chernobyl Research." Copyright January 2020. 

World Nuclear News. "Chernobyl confinement structure systems begin operation." Feb. 8, 2019.

World Nuclear News. "Decommissioning of Chernobyl units approaches." Feb. 19. 2014.

BBC. "The people who refused to leave Chernobyl." April 26, 2016.

CNN. "After Chernobyl, they refused to leave." Nov. 7, 2013.

The Guardian. "Chernobyl now: 'I was not afraid of radiation' – a photo essay." June 7, 2019.

Live Science. "Chernobyl Woos Tourists with Promise of 'Negligible' Risk." Dec. 15, 2010.

Live Science. "Nearly 30 Years After Chernobyl Disaster, Wildlife Returns to the Area." Oct. 13, 2015.

National Geographic. "Animals Rule Chernobyl Three Decades After Nuclear Disaster." April 18, 2016.

Live Science. "Is It Safe to Visit Chernobyl?" June 7, 2019.

BBC. "The people who moved to Chernobyl." Oct. 12, 2018.

Live Science. "Disaster Tourists Are Flocking to Chernobyl, Thanks to HBO Series." June 5, 2019.

Live Science. "Who Will Prevent the Next Chernobyl? (Op-Ed)" April 25, 2016.

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International Atomic Energy Agency. "IAEA Director General Statement on the Situation in Ukraine." Feb. 24. 2022.

This article was updated on June 20, 2019 by Live Science Contributor Rachel Ross.

On April 26, 1986, an accident at Ukraine's Chernobyl nuclear power plant caused some 350,000 people to flee their homes as thick plumes of radioactive material spewed into the sky, according to the World Nuclear Association. Upon evacuating, they would have had to decontaminate their clothes, bodies and any items to avoid being exposed to and spreading toxic radioactive substances. Later, the surrounding region would have to be cleaned up as well.

But how do you decontaminate objects and people that have been exposed to dangerous levels of radiation? To answer that question, it's important to understand the basics of how radioactivity works.

Essentially, radioactivity means that the atoms in a given material have too much energy or mass to be stable. Over time, these unstable atoms shed their excess in the form of radiation — subatomic particles that travel at the speed of light.

Not all radiation or radioactive substances are considered contamination, and they are often not harmful at low levels. "Radioactive material is everywhere in our environment — in the soils, the air, the water, our food and our bodies," Barbara Hamrick, a certified health physicist at the University of California, Irvine Medical Center, told Live Science in an email. But "we don't consider that contamination, because we expect it to be there," she said.

Related: How radioactive is the human body?

Radiation comes in two forms: ionizing and nonionizing. Nonionizing radiation is lower in energy, and includes things like radio waves, microwaves and sunlight, which are generally not harmful in moderation (as long as you wear sunscreen for the latter). Ionizing radiation, by contrast, is energetic enough to damage your body, according to the Centers for Disease Control and Prevention. It does this by breaking the bonds holding strands of DNA together, leading to cell death, according to research published in the journal Genetics and Molecular Biology. A hefty dose of ionizing radiation — for example, from a nuclear weapon or nuclear power plant meltdown — can cause burns, blisters, nausea, hair loss and even cancer. Workers wear hazmat suits to protect against this type of radiation at a nuclear power plant. 

While ionizing radiation is scary, the particles themselves can't contaminate objects (or people) and make them radioactive. "They are similar to X-rays, which pass through patients and do not leave any contamination behind,' Michael Ojovan, an associate reader in materials science and waste immobilization, told Live Science. Rather, objects become contaminated only when they get some amount of unwanted radioactive material on them.

A lot of dangerous ionizing radioactive material is transmitted in the form of dust, sometimes called nuclear fallout, which can settle onto the surface of various objects and contaminate them. This dust is easy to remove manually. In fact, many decontamination procedures involve simply wiping down the contaminated object, or washing it with soap and water. The materials used to wash off the contamination — for instance wipes, water and soap — then become waste that has to be stored in silos made of reinforced concrete, occasionally buried deep underground, according to the United States Nuclear Regulatory Commission. 

But things can get a little more intense if you're dealing with higher doses of radioactive material. "Heavily contaminated objects are decontaminated using strong chemicals," such as nitric acid and permanganate, Ojovan said. These chemicals can bind to radioactive metals in a process called chelation and render them inert, according to the Environmental Protection Agency.

At Chernobyl, liquidators helped filter and clean the water around the nuclear reactor using chemical cleaning methods. They also constructed the thick concrete and lead "sarcophagus" around the reactor to help prevent more radioactive material from leaking into the ground or water supply.

People exposed to high levels of ionizing radiation should take off their outer layers of clothing, which can remove up to 90% of radioactive material, and then shower with soap and water or wipe themselves down, according to ready.gov, a U.S. disaster preparedness site. And they definitely shouldn't condition their hair, as at the microscopic level hair looks like a bristly pine cone; conditioner smooths down these bristles, which could trap radioactive dust within a person's hair.

If an object can't be decontaminated with water or chemical treatments, it's probably best to put it in the storage silo; many hazardous radioactive materials take an extremely long time to peter out on their own. As a radioactive substance emits particles, it becomes slightly less energetic; the amount of time it takes to lose half of its energy is called its half-life. After 10 half-lives, it will emit less than 0.5% of the original radiation, at which point it may be considered safe in many instances, according to Hamrick.

A handful of hazardous radioactive substances, like iodine-131, have short half-lives of just a few days. However, many others have extraordinarily long half-lives. Uranium-235, which is commonly used in nuclear power plants, has a half-life of about 710 million years, according to the Environmental Protection Agency. If you got uranium-235 dust all over your favorite shirt, you'd have to wait over 7 billion years to get it back.

Japan is currently preparing to release 500 olympic swimming pools' worth of water that was tainted by the Fukushima nuclear plant meltdown into the Pacific Ocean. The water has been treated, filtered and diluted, but still contains trace amounts of radioactive tritium, according to Reuters. Tritium has a half-life of 12.3 years, so the water would take 123 years to be considered non-radioactive. But in a controversial move, Japanese officials, along with other experts from around the world, hope that the ocean will dilute the water enough to render it completely harmless.

Nuclear fusion is the reaction that churns at the hearts of stars, in which two light atomic nuclei merge into a single heavier nucleus. Fusion produces very little nuclear waste, and no greenhouse gas emissions, which means it has long been touted as a potential clean alternative to conventional energy sources. But what drives this process? And could it ever become a viable commercial power energy source?

What is fusion?

Fusion occurs when two light atoms bond together, or fuse, to make a heavier one. The total mass of the new atom is less than that of the two that formed it; the "missing" mass is given off as energy, as described by Albert Einstein's famous "E=mc^2" equation.

Usually, atomic nuclei repel each other because they have the same charge. High temperatures, pressures, or both are required to overcome this repulsion. On Earth, temperatures in nuclear fusion reactors reach nearly six times those found in the core of the sun, according to Oak Ridge National Laboratory. At this heat, the hydrogen is no longer a gas but a plasma, an extremely high-energy state of matter in which electrons are stripped from their atoms.

Fusion differs from fission, which splits atoms and results in substantial radioactive waste, which is hazardous.

Fusion is the dominant source of energy for stars in the universe. It is also a potential energy source on Earth, if scientists can figure out how to get more energy out of the reaction than it requires to initiate it. When set off in an intentionally uncontrolled chain reaction, nuclear fusion drives the hydrogen bomb. Fusion is also being considered as a possibility to power crafts through space.

Nuclear fusion energy

The "Holy Grail" of clean power is to generate commercial energy from nuclear fusion reactions.  

Scientists have pursued this goal for decades. Fusion is such an attractive alternative to existing energy sources because it produces little-to-no radioactive waste or greenhouse gas and requires relatively simple ingredients. Key to this dream of limitless clean power is producing more energy from the reaction than it takes to produce it. 

In 2022, scientists with Lawrence Livermore National Laboratory's National Ignition Facility (NIF) announced that for the first time, a nuclear fusion core produced more energy than it consumed. The ignition facility uses laser beams to confine a plasma of deuterium and tritium, two isotopes, or versions, of hydrogen. But experts say a viable commercial fusion reactor is likely decades away. That's because to heat the plasma, scientists must draw energy from the electrical grid. So to make the reaction viable, the energy produced by the reaction must also account for the sizable amount of energy lost as electricity is converted to the light that powers the lasers.

Deuterium-Tritium fusion: The most promising combination for power on Earth today is the fusion of a deuterium atom with a tritium one to create a helium atom. The process, which requires temperatures of approximately 72 million degrees F (39 million degrees Celsius), produces 17.6 million electron volts of energy. 

Current experiments with deuterium-tritirum fusion are ongoing at the the DIII-D National Fusion Facility in San Diego, California. The largest potential nuclear reactor, the ITER project in southern France, which is still years from completion, also uses these two isotopes to power its reaction. Unlike the NIF reactor, the ITER project uses strong magnets to steer the hydrogen plasma around a donut-shaped reactor, called a tokamak. 

Deuterium is a promising ingredient because it is an isotope of hydrogen, containing a single proton and neutron but no electron. In turn, hydrogen is abundant in water. A gallon of seawater (3.8 liters) could produce as much energy as 300 gallons (1,136 liters) of gasoline.

Tritium contains one proton and two neutrons. It was produced in large quantities during nuclear missile testing in the 20th century, but its half-life is about 12 years, meaning half of the quantity decays in that time frame. Scientists at ITER have proposed making tritium in large quantities by bombarding lithium, an element found in Earth's crust, with neutrons.

Deuterium-deuterium fusion: Theoretically more promising than deuterium-tritium because of the ease of obtaining the two deuterium atoms and the higher energy yields it would produce, this method is also more challenging because it requires extremely high temperatures to work. Several test nuclear fusion reactors can reach temperatures around 270 million F (150 million C), according to ITER. However, a solely deuterium-deuterium reaction would require temperatures of at least 720 million to 900 million F (400 million to 500 million C), according to EuroFusion, a consortium of national fusion institutes located around Europe.

So far, the only facility capable of initiating the deuterium-deuterium reaction is the Joint European Torus (JET) facility, which has only achieved it fleetingly, according to EuroFusion.

Fusion reactions in stars

Proton-proton fusion: The dominant driver for stars like the sun with core temperatures under 27 million F (15 million C), proton-proton fusion begins with two protons and ultimately yields high energy particles such as positrons, neutrinos, and gamma rays. In order to achieve fusion as such low temperatures, stars rely on crushing pressures of more than 200 billion times those of atmospheric pressure on Earth, according to West Virginia University.

Carbon cycle: Stars with higher temperatures merge carbon rather than hydrogen atoms. In this process, stars begin with carbon-12 and walk through six different steps to produce a helium nucleus and another carbon-12 atom, according to the Swinburne University Centre for Astrophysics and Supercomputing.

Triple alpha process: Stars such as red giants at the end of their phase, with temperatures exceeding 180 million F (100 million C) fuse helium atoms together rather than hydrogen and carbon.

Additional resources

Read more about the fusion that powers the stars from NASA. This video describes  how the largest nuclear fusion reactor is being built. And read more about the race to build such reactors in "The Star Builders: Nuclear Fusion and the Race to Power the Planet" (Scribner, 2021).

Scientists have just announced a breakthrough in nuclear fusion ignition: For the first time the heart of a powerful fusion reactor has briefly generated more energy than was put into it. But experts are urging caution, saying that the breakthrough, while hugely significant, is still a long way from safe, limitless nuclear energy.

On Tuesday (Dec. 13), physicists at the U.S. government-funded National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California announced that they were able to fire a laser carrying roughly 2 megajoules of energy into a tiny fuel pellet made up of two hydrogen isotopes, turning the atoms into plasma and producing 3 megajoules of energy — a 50% increase. 

Scientists are very excited by the results, but wary of overhyping them. The reactor as a whole did not produce a net gain of energy. For a fusion reaction to be practically useful, the tens of megajoules drawn from the electrical grid, converted into the laser beams and fired into the reactor core would have to be significantly less than the energy released from the plasma. 

Related: Nuclear fusion reactor core produces more energy than it consumes in world-first demonstration

But the new plasma ignition milestone only accounts for the laser energy in and the plasma energy out, not the sizable loss from converting electricity to light. 

What's more, the reaction takes place in a tiny fuel pellet inside the world's biggest laser, lasts only a few billionths of a second, and can only be repeated every six hours. This makes the reaction far too inefficient for practical purposes. 

"Net energy gain is a significant milestone, but to put it in perspective, it means fusion is now where Fermi put fission about eighty years ago," Ian Lowe, a physicist and emeritus professor at Griffith University in Australia, told Live Science. "The huge technical problem is maintaining a mass of plasma at a temperature of several million degrees to enable fusion, while extracting enough heat to provide useful energy. I still haven't seen a credible schematic diagram of a fusion reactor that achieves that goal."

How fusion reactors work

Existing fusion reactors can be split into two broad categories: inertial confinement reactors like the NIF's, which contain the hot plasma with lasers or particle beams, and magnetic confinement reactors, such as the U.K.-based Joint European Torus (JET), Europe's upcoming International Thermonuclear Experimental Reactor (ITER), and China's Experimental Advanced Superconducting Tokamak (EAST), which sculpt the plasma into various torus shapes with strong magnetic fields. At ITER, the field confining the burning plasma will be 280,000 times as strong as the one around Earth. 

The varying reactor types reflect different strategies for overcoming fusion's intimidating technical barriers. Magnetic confinement reactors, known as tokamaks, aim to keep the plasma continuously burning for prolonged periods of time (ITER's goal is to do this for up to 400 seconds). But, despite edging ever closer, tokamaks have yet to create a net energy gain from their plasmas. 

On the other hand, inertial confinement systems like the NIF reactor, which also operates to test thermonuclear explosions for military purposes, generate bursts of energy by quickly burning one tiny chunk of fuel after another. This fuel, however comes in the form of discrete pellets, and scientists have yet to figure out how to replace them quickly enough to maintain a reaction for longer than the tiniest fraction of a second.

"That is very, very tricky because it would mean that you need to position your next pellet during the time that the [plasma] cloud expands in the vessel," Yves Martin, the deputy director of the Swiss Plasma Center at the École polytechnique fédérale de Lausanne in Switzerland, told Live Science. "This pellet is typically one millimeter [0.04 inches] big in diameter and it has to be positioned in a room which is nine meters [30 feet] across. As far as I know, it still costs several tens of thousands of dollars [to get the reaction going]. To be interesting, it should go down to one dollar or even less."

A very expensive isotope

Another problem for fusion reactors is the dwindling supplies of tritium, a key isotope that is combined with deuterium as fuel for the reaction. Once a common and unwanted byproduct of open air nuclear weapons tests and nuclear fission — which splits atoms instead of combining them and produces far more radioactive waste — tritium's 12.3-year half-life means that much of its existing stock is already on the way to being unusable, making it one of the most expensive substances on Earth at $30,000 per gram. 

Physicists have proposed other methods for making tritium, such as breeding it inside nuclear reactors that capture stray neutrons. But, besides some smaller scale experiments, rapidly ballooning costs meant plans to test tritium breeding at ITER had to be scrapped. 

Fusion researchers believe that if the political will can be found and the engineering challenges solved, the first viable fusion reactors could come online as soon as 2040. But that's still ten years too late to keep global warming below the target of 1.5 degrees Celsius (2.7 degrees Fahrenheit), by 2030.

"Decision makers yearn for the holy grail of clean energy from an abundant resource," Lowe said. "Having spent squillions on fusion research, they are very reluctant to give up, just as they spent decades chasing the fantasy of the breeder reactor [a fission reactor which outputs more energy than it consumes]."

Nevertheless, recent years have seen improvements to fusion technology arriving in a steady stream. These include a successful trial of AI to control the plasma inside a tokamak; a slew of records in power generation, plasma burn time, and reactor temperatures across multiple experiments; and the rewriting of a foundational rule which could enable future reactors to generate twice as much power. In light of these advances, fusion scientists insist that multiple strategies for a long-term solution to the climate crisis are necessary, and that fusion will become a vital component of a future carbon-free energy system. 

"If we wanted to rely on renewables only, we would need such an excess of installations to have the amount of energy you would typically need in winter, or in a period with no wind. We need something which will be the base level that will produce exactly what you want," Martin said. "It's not because I believe in fusion that I will not put some solar panels on my roof. In a sense, we really need to use everything that is better than fossil fuels."

Chernobyl's nuclear power plant has lost electricity again, just hours after being switched back on, Ukraine's state energy company has said. 

Russian forces attacked the defunct nuclear facility on the very first day of the invasion (Feb. 24), seizing it after heavy fighting and taking its roughly 210 staff hostage, Live Science previously reported. After briefly being restored last night, the plant's electricity has now been disconnected from the electrical grid yet again, potentially stopping the approximately 20,000 spent nuclear fuel units held in the plant's cooling tanks from receiving cooling.

Ukraine's grid operator, Ukrenergo, has blamed Russian troops for damaging the plant's high-voltage power line for the second time and has demanded safe entry for a repair crew to access it.

Related: 5 weird things you didn't know about Chernobyl

"The Chornobyl NPP [Nuclear Power Plant] is an important facility that cannot be left without a reliable energy supply," Ukrenergo wrote on Facebook. "Unimpeded and quick access of Ukrenergo repair crews to these lines for inspections and repairs is extremely important not only for Ukrainian consumers but also for Europe as a whole."

Ukrenergo said that restoring power to the plant will help to "avoid a repeat disaster at the Chernobyl nuclear power plant." Ukrainian officials have also warned that the plant's lack of access to power could increase the likelihood of the evaporation and discharge of nuclear material, and potentially expose plant personnel to a dangerous dose of radioactive material.

But nuclear experts, including the United Nations' International Atomic Energy Agency (IAEA), have downplayed these concerns, saying that cutting off power to the Chernobyl power plant will not have a drastic impact on the facility's safety. 

The IAEA wrote in a tweet that while the development "violates (a) key safety pillar," it saw "no critical impact on safety," as "the heat load of spent fuel storage pool and volume of cooling water at #Chornobyl Nuclear Power Plant '' were "sufficient for effective heat removal without need for electrical supply."

"The fuel in these pools is decades old, and hence has very little residual heat being generated. This low heat load added to the very large volume of water in the cooling pools means that the heat coming from the fuel can be dissipated safely even without power to circulate the water." Tom Scott, a radioactive materials professor at University of Bristol in England, said in a statement.

The seven pillars of nuclear safety are regulatory requirements set out by the IAEA for nuclear facilities. Among them are the requirements to maintain the physical integrity of nuclear facilities; ensure that staff are not under coercion or duress; and guarantee a constant supply of electricity to facilities.

IAEA officials have expressed increasing concern for the well-being of the Chernobyl staff, who have been held hostage at the plant for just under three weeks. Workers would usually leave the radioactive plant after work hours ended but have now been forced to live at the site.

Russian troops have also taken over Zaporizhzhia plant, an active nuclear power plant. Systems set up to monitor the nuclear material at the Chernobyl and Zaporizhzhia facilities stopped transmitting data to the IAEA on Tuesday (March 8) and Wednesday (March 9). Safeguards are the technical measures that the IAEA uses to keep track of radioactive material's activity and location. With these offline, the agency has no way of knowing the location of the plant's nuclear material, increasing the possibility that it could fall into the wrong hands.

Originally published on Live Science.

Chernobyl’s nuclear power plant and all the facilities in the Chernobyl exclusion zone have been completely disconnected and are now without electricity, Ukraine’s state energy company has announced. 

Russian forces attacked the defunct nuclear facility on the very first day of the invasion (Feb. 24), seizing it after heavy fighting and taking its roughly 210 staff hostage, Live Science previously reported. Now that the plant has been disconnected from the electrical grid, the roughly 20,000 spent nuclear fuel units held in the plant's cooling tanks will no longer receive active cooling.

Ukrainian officials have warned that this could increase the likelihood of the evaporation and discharge of nuclear material, and give a dangerous dose of radioactive material to the plant’s personnel. Some nuclear energy experts, however, have cautioned that, as the spent fuel rods are now 22 years old and much colder than they were, this event is unlikely.

Related: 5 weird things you didn't know about Chernobyl

"The spent fuel rods are at minimum 22 years old. They have very little heat to dissipate," Mark Nelson, the managing director of the Radiant Energy Fund, which advises companies and nonprofits about nuclear energy, wrote on Twitter. "Their heat is low enough that experts I've talked to expect weeks or even months to heat the water enough to dry out the pool. Even then, natural air circulation should be sufficient."

The Ukrainian State Service of Special Communications and Information Protection of Ukraine (SSSCIP) has blamed the power outage on "damage caused by the occupiers," although there has yet to be any independent verification of the cause. 

Ukraines foreign minister Dmytro Kuleba said that the Chernobyl plant's reserve diesel generators had a 48-hour capacity, and called for a ceasefire to restore the electricity.

Meanwhile, officials from the UN's International Atomic Energy Agency (IAEA) have expressed increasing concern for the well-being of the staff at Chernobyl, who have been held hostage at the plant for two weeks. Workers would usually leave the radioactive plant after work hours ended but have now been forced to live at the site. 

Systems set up to monitor the nuclear material at Chernobyl’s radioactive waste facilities stopped transmitting data to the UN's nuclear watchdog on Tuesday (March 8). Safeguards are the technical measures that the IAEA uses to keep track of nuclear material. With these offline, the agency has no way of knowing the location of the plant's nuclear material, increasing the possibility that it could fall into the wrong hands.  

The IAEA said in a statement that "remote data transmission from safeguards monitoring systems installed at the Chernobyl NPP had been lost," and that while workers have "access to food and water, and medicine to a limited extent", the "situation for the staff was worsening."

Staff at the facility are responsible for decommissioning the site and ensuring the safe disposal of the radioactive material inside the plant’s defunct reactors. However, since the Russian occupation of Chernobyl, that work has been put on hold. Prior to the power outage, workers could only be contacted via email.

"I'm deeply concerned about the difficult and stressful situation facing staff at the Chernobyl nuclear power plant and the potential risks this entails for nuclear safety," IAEA Director General Rafael Grossi said in the statement. "I call on the forces in effective control of the site to urgently facilitate the safe rotation of personnel there."

Eight of Ukraine's 15 operational nuclear reactors are still online, Ukraine's nuclear regulator said in the statement, including two at the Zaporizhzhya plant that was captured by Russian forces last week, Live Science previously reported. Staff at the Zaporizhzhya plant, which briefly caught fire after being shelled during its capture, are working in shifts. Radiation at both Chernobyl and Zaporizhzhya has been reported to be at normal levels.

Originally published on Live Science.

Russian troops have seized Ukraine's Zaporizhzhia nuclear power plant after overnight shelling sparked a fire near one of the facility's reactors, which burned for several hours.

World leaders have condemned the "reckless" attack on the plant, the largest nuclear facility by capacity in Europe, after a projectile struck an auxiliary training building just 490 feet (150 meters) from one of the plant's reactor units, starting a fire that blazed from early morning until around 6:20 a.m. local time Friday (March 4).

Firefighters successfully put out the fire, with no damage reported to reactors or safety systems, and radiation hasn't exceeded baseline levels, according to the International Atomic Energy Agency. Employees have continued to work on the site after its capture by Russian forces, the Ukrainian state inspectorate for nuclear regulation said in a statement. Ukraine’s nuclear agency said that three soldiers had been killed and two wounded by the attack.

Related: 5 weird things you didn't know about Chernobyl

"The plant's staff continues to work on power units, ensuring the stable operation of nuclear facilities," Energoatom, Ukraine's nuclear power operator, wrote on Telegram. "Unfortunately, there are dead and wounded among the Ukrainian defenders of the station."

The Zaporizhzhia plant, which is situated in southeastern Ukraine near the city of Enerhodar, produces enough energy to supply 4 million households with electricity, covering roughly one-fifth of Ukraine's population. 

The attack on the plant, which came on the ninth day of Russia's invasion of Ukraine, has raised concerns about the security of Zaporizhzhia and Ukraine's three remaining operational nuclear power plants. The Ukrainian state inspectorate for nuclear regulation has warned that "loss of the possibility to cool down nuclear fuel will lead to significant radioactive releases into the environment," which could "exceed all previous accidents at nuclear power plants, including the Chernobyl accident and the accident at the Fukushima Daiichi nuclear power plant."

"Russian people, I want to appeal to you: How is this possible? After all, we fought together in 1986 against the Chernobyl catastrophe," Ukrainian President Volodymyr Zelenskyy said in a televised address on Friday. U.S. President Joe Biden called the Ukrainian president in the early hours of the morning to speak about the situation at the plant, according to the White House. The two leaders urged the Russian government to halt military activity around the area and allow firefighters and emergency responders to enter the plant.

Some experts, however, think that making close connections between Zaporizhzhia and the Chernobyl disaster could be a mistake.

Large parts of the Chernobyl exclusion zone, which lies about 60 miles (100 kilometers) north of the capital, Kyiv, have been closed off since the disastrous meltdown of Ukraine's Chernobyl nuclear power plant in 1986. In that disaster, two explosions inside the plant's reactor flipped its 2,000-ton (1,800 metric tons) lid like a coin, blanketing the surrounding 1,000 square miles (2,600 square kilometers) with radioactive dust and reactor chunks. Following evacuation and the dousing of the nuclear fire — which cost many firefighters their lives — the reactor was sealed off and the area was deemed uninhabitable by humans for the next 24,000 years. After fighting broke out there last week, the zone is also occupied by Russian forces, Live Science previously reported. 

Despite the frightening surface similarities between the two events, Zaporizhzhia's reactors are much safer than the ones at Chernobyl, according to nuclear scientists. Unlike Chernobyl's RBMK-1000 reactors, Zaporizhzhia uses more modern pressurized water reactors, which require significantly less uranium fuel in the reactor core, thus limiting the likelihood of a runaway chain reaction. Two layers of protection — a steel-reinforced concrete outer containment unit and a 8-inch-thick (20 centimeters) steel inner vessel — also surround the reactor. Both layers are designed to withstand earthquakes and explosions. Pressurized water reactors also shut down automatically in the event of an emergency. 

Nonetheless, a direct shell hit to the outside of a reactor could still be dangerous, according to Robin Grimes, a professor of materials physics at Imperial College London. Puncturing the Zaporizhzhia reactors' twin shells wouldn't lead to an explosion like at Chernobyl, he says, but it would still release a lot of dangerous material.

"It is not designed to withstand explosive ordinance such as artillery shells," Grimes said in a statement. "While it seems to me unlikely that such an impact would result in a Chornobyl-like nuclear event, a breach of the pressure vessel would be followed by the release of coolant pressure, scattering nuclear fuel debris across the vicinity of the plant and a cloud of coolant with some entrained particles reaching further." 

Despite being much safer than those at Chernobyl, Zaporizhzhia's reactor cores still contain a lot of highly radioactive fuel, and this is not the only source of concern. Environmentalists and nuclear experts have long warned that the plant's spent nuclear fuel rods, cooling in acres of open water pools and standing in open-air yards behind the site, could produce catastrophic airborne plumes of radiation if struck by a stray shell or missile.

On the day before the blaze (March 3), crowds of local residents and employees of the nuclear facility attempted to block Russian troops from advancing toward the plant by setting up improvised barricades, but after some resistance, the Russian troops broke through.

Edward Obbard, a nuclear engineering program coordinator at the University of New South Wales in Australia, said that the greatest impact of the attack is not the risk of nuclear fallout but rather the loss of electricity to the Ukrainian people and the likelihood of much more fighting.

"The availability of nuclear power is vital to energy security in multiple European States and particularly in Ukraine," he said in a statement. "All nuclear-related risks to people in the vicinity, even in very worst case scenarios, pale in comparison to the very direct and lethal hazard of continued fighting on the ground."

Originally published on Live Science.

Russian troops have captured the Chernobyl nuclear power plant, which still contains nuclear waste that could pose a threat to the surrounding area. What would happen if the site were to be bombed?

"Our defenders are giving their lives so that the tragedy of 1986 will not be repeated," Ukrainian President Volodymyr Zelenskyy tweeted a few hours before the power plant was seized yesterday. "This is a declaration of war against the whole of Europe."

Chernobyl is the site of four nuclear reactors, three of which have been decommissioned. The fourth was the source of the historic explosion in 1986. That reactor is now protected by an inner concrete sarcophagus and a new, 32,000-ton outer shell. In addition, spent nuclear fuel from the other reactors is still stored at the site, along with radioactive waste from contaminated equipment. 

Even though the reactor is covered, radiation has contaminated the entire site. In fact, dozens of radioactive elements were launched into the air during the meltdown, with a few of them considered the most dangerous to life, including the isotopes iodine 131, strontium 90, cesium 134 and cesium 137; the strontium and cesium isotopes have long enough half-lives that they still linger at the site, according to the International Atomic Energy Agency. 

Now, some public figures have expressed fears that any future shelling of these sites could spread this radioactive material far beyond Chernobyl's exclusion zone — an off-limits area around the disaster — even as far as neighboring countries.

On Thursday morning (Feb. 24), Anton Gerashchenko, an adviser and former deputy minister at the Ukrainian Ministry of Internal Affairs, wrote on Facebook, "If as a result of the occupiers' artillery strikes the nuclear waste storage facility is destroyed, the radioactive dust may cover the territories of Ukraine, Belarus and the EU [European Union] countries!"

Related: 5 interesting facts about Chernobyl

But the reality may not be so dire, according to Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists. "Even if there were an inadvertent shelling of that confinement structure, I think it would take more than that to mobilize a significant amount of radioactive material," Lyman told Live Science.

"It would be hard for me to imagine that kind of consequence," Lyman added. 

Spent fuel, or the radioactive elements that were used to fuel the power plant, continue to decay into more stable elements and, in doing so, continue to release heat, he said. 

"The most serious concern is the wet storage of spent fuel, because that's probably the most concentrated quantity of radioactive material on-site," Lyman said. "Generally, spent nuclear fuel still has decay heat. And so if it's in wet storage, there has to be some way of removing that heat." 

That fuel has been cooling for at least a couple of decades. "And so that decay heat is not that significant," Lyman said. "But still, if there was disruption to cooling … or if there was a breach of the pool that led to draining water, then that fuel could conceivably heat up to the point where it might burn. That's probably the biggest threat." 

However, such burning could take days or weeks, he added.

A more recent concern involves rising radiation levels around the facility, most likely a result of radioactive dust kicked up by military vehicles. But the type of dust and the radiation doses being measured suggest that this may not be much of a threat, either, according to Lyman.

"If it's a resuspension of dust, this is generally stuff that was not that mobile, or it would have blown away," he said. "So it's probably heavier particles of soil that don't disperse very far." More likely, he added, it might cause a temporary increase in radiation levels, and the data will show whether that's true.

But even such a temporary increase may not be a danger to human health, Lyman said.

"The dose rates they're finding are not that much greater than the usual dose rates in that area, which, admittedly, are probably about a hundred times the background dose of anywhere else in the world," Lyman said. "But even so, if [the troops] don't spend that much time in the area, it's not going to have a significant impact on their health compared to the threat of dying in war."

Nonetheless, Lyman thinks this event shows that plans for nuclear power need to consider the possibility of war. 

"The potential for nuclear power plants to be targets at wartime is something that really needs consideration," Lyman said, "especially when they're talking about expanding nuclear power to parts of the world that currently have more unstable regions." 

Originally published on Live Science.

Chinese government scientists have unveiled plans for a first-of-its-kind, experimental nuclear reactor that does not need water for cooling.

The molten-salt nuclear reactor, which runs on liquid thorium rather than uranium, is expected to be safer than traditional reactors because the molten salt cools and solidifies quickly when exposed to the air, insulating the thorium, so that any potential leak would spill much less radiation into the surrounding environment compared with leaks from traditional reactors. 

The prototype reactor is expected to be completed next month, with the first tests beginning as early as September. This will pave the way for the building of the first commercial reactor, slated for construction by 2030.

As this type of reactor doesn't require water, it will be able to operate in desert regions. The location of the first commercial reactor will be in the desert city of Wuwei, and the Chinese government has plans to build more across the sparsely populated deserts and plains of western China, as well as up to 30 in countries involved in China's "Belt and Road" initiative — a global investment program that will see China invest in the infrastructure of 70 countries.

Related: Science fact or fiction? The plausibility of 10 sci-fi concepts

Chinese government officials view nuclear energy exports to be a key part of the Belt and Road program.

"'Going out' with nuclear power has already become a state strategy, and nuclear exports will help optimize our export trade and free up domestic high-end manufacturing capacity," Wang Shoujun, a standing committee member of the China People's Political Consultative Conference (CPPCC) — a political advisory body which acts as a link between the Chinese government and business interests, said in a report on the CPPCC's website.

Thorium — a silvery, radioactive metal named after the Norse god of thunder — is much cheaper and more abundant than uranium, and cannot easily be used to create nuclear weapons. The new reactor is a part of Chinese President Xi Jinping's drive to make China carbon-neutral by 2060, according to the team at the Shanghai Institute of Applied Physics that developed the prototype. China currently contributes 27% towards total global carbon emissions, the largest amount from any individual country and more than the entire developed world combined, according to a 2019 report by the US-based Rhodium Group. 

"Small-scale reactors have significant advantages in terms of efficiency, flexibility and economy," Yan Rui, a physics professor at the Shanghai Institute of Applied Physics, and colleagues wrote in a paper about the project published July 15 in the journal Nuclear Techniques. "They can play a key role in the future transition to clean energy. It is expected that small-scale reactors will be widely deployed in the next few years." 

Instead of using fuel rods, molten-salt reactors work by dissolving thorium into liquid fluoride salt before sending it into the reactor chamber at temperatures above 1,112 Fahrenheit (600 degrees Celsius). When bombarded with high energy neutrons, thorium atoms transform into uranium-233, an isotope of uranium which can then split, releasing energy and even more neutrons through a process called nuclear fission. This starts a chain reaction, releasing heat into the thorium-salt mixture, which is then sent through a second chamber where the excess energy is extracted and transformed into electricity. 

Thorium reactors have long held an elusive appeal for nuclear scientists. Sitting just two positions to the left of uranium on the periodic table of chemical elements, nearly all mined thorium is thorium-232, the isotope used in nuclear reactions. In contrast, only 0.72% of total mined uranium is the fissile uranium-235 used in traditional nuclear reactors. This makes thorium a much more abundant source of energy. 

Thorium’s advantages don’t stop there. The waste products of uranium-235 nuclear reactions remain highly radioactive for up to 10,000 years and include plutonium-239, the key ingredient in nuclear weapons. Traditional nuclear waste has to be housed in lead containers, isolated in secure facilities, and subject to rigorous checks to ensure that it doesn’t fall into the wrong hands. In contrast, the main byproducts of a thorium nuclear reaction are uranium-233, which can be recycled in other reactions, and a number of other byproducts with an average “half-life” (the time it takes for half of a substance’s radioactive atoms to decay to a non-radioactive state) of just 500 years. 

After the 2 megawatt prototype has undergone tests in September, China plans to build its first commercial thorium reactor. Measuring only 10 feet (3 meters) tall and 8 feet (2.5 m) wide, the researchers claim it will be capable of generating 100 megawatts of electricity, enough to provide power for 100,000 people. Still, it must be paired with other equipment, like steam turbines, to make usable electricity. 

The molten-salt reactor concept was first devised back in 1946 as part of a plan by the predecessor to the U.S. Air Force to create a nuclear-powered supersonic jet. 

However, the experiment and the many others which followed — including an experimental reactor at Oak Ridge National Laboratory in Tennessee which operated for many years — ran into problems. Corrosion caused by the hot salt cracked pipes and the weak radioactivity of thorium makes it very difficult for fission reactions to build up to sustainable levels without adding uranium. The investigations into thorium stopped.

It is not yet clear how, sixty years later, Chinese researchers have solved these technical problems.

China's effort is the furthest developed of many other fresh attempts to create thorium reactors, including one called Natrium, which plans to build a pilot plant in Wyoming and enjoys the financial backing of Bill Gates and Warren Buffett.

Nuclear reactors aren't the only technology China is investing in as a part of its effort to become carbon-neutral. The Baihetan Dam, the second-largest hydroelectric facility in the world after China's Three Gorges Dam, went online in June and has an energy-generating capacity of 16 gigawatts. The U.K.-based energy consultancy Wood Mackenzie estimates that China will add 430 gigawatts of new solar and wind power capacity in the next five years.

Even as China positions itself as a global leader in the fight against climate change, the country is already under acute strain from extreme weather events. Severe flooding in the province of Henan this week displaced around 100,000 people and killed at least 33, CNN reported. The weather bureau in Zhengzhou, the capital of the region, said the three days of rain matched levels seen only "once in 1,000 years."

Originally published on Live Science.

Fission and fusion are both natural atomic processes that release incredible amounts of energy, but in many ways, they are opposites. Fission involves the splitting of a single, generally heavy, atomic nucleus, whereas fusion requires the combining of two or more light atoms. 

Atoms include protons and neutrons bound together in a central nucleus. Radioactive elements, like uranium, may contain dozens of these particles in their atomic hearts. 

Fission occurs when heavy elements such as uranium spontaneously decay, which causes their nuclei to split. Each of the resulting halves has slightly less mass than the original atomic core, and the missing mass is converted to energy. 

Related: Why NASA's Mars rover Perseverance will use nuclear power to stay warm

Physicists Lise Meitner and Otto Frisch discovered the principles underlying fission after receiving a private letter from nuclear chemist Otto Hahn in December 1938. Hahn's experiments showed that uranium atoms that were bombarded with neutrons would split, and Meitner and Frisch used the new science of quantum mechanics to explain why this happened.

All three scientists soon realized the terrible implications of their discovery, which was happening under the shadow of World War II. A single instance of fission might release a relatively small amount of power, but many fission reactions happening at the same time had the potential to be quite destructive if used to develop something like an atomic bomb.

Nuclear fission for energy and weapons

When a uranium atom naturally goes through fission, it releases a neutron that will careen around. If this neutron hits other nearby uranium atoms, they will also split, creating a cascading chain reaction. In 1951, engineers built the first power plant harnessing the process of nuclear fission to produce energy, according to the U.S. Department of Energy.  

In a nuclear power plant, this process is carefully controlled. Fission releases heat, which boils water and generates steam that spins a turbine. 

But in an atomic bomb, the cascading chain reaction spirals out of control, with fission happening at an ever-increasing rate. This releases a tremendous amount of power in a short span, generating the devastating blast of the bomb. 

Related: 6 years after Fukushima: Has Japan lost faith in nuclear power? 

Why fusion doesn't produce energy, yet

Fusion, by contrast, has yet to be fully developed as a human power source. In nuclear fusion, two nuclei of a light element, such as hydrogen, must overcome their natural electromagnetic repulsion and merge into a single, heavier nucleus. 

The resulting entity is slightly less massive than the original two nuclei, and just like with fission, this missing mass is converted into energy. But generating enough power to smash atoms together until they stick is not easy and generally requires the extreme environment of a star's belly to happen.

Engineers have long dreamed of making sustained fusion reactions here on Earth. Fusion power would produce less nuclear waste than fission and uses relatively common light elements, such as hydrogen —  rather than rarer uranium — as a fuel supply, according to the International Atomic Energy Agency.

Related: Nuclear fusion reactor could be here as soon as 2025

But creating and sustaining fusion is difficult. An international experiment to test the feasibility of using sustained nuclear fusion to produce energy has built a magnet that's as tall as a four-story building and 280,000 times more powerful than Earth's magnetic field, as part of the International Thermonuclear Experimental Reactor (ITER). 

But ITER, a scientific partnership among 35 countries, has suffered numerous delays during its construction and isn't expected to generate more power than it consumes until at least the 2030s. 

Additional resources

• Check out this helpful table that lists the difference between fission and fusion, from Chemistry LibreTexts. 
• Watch this video from the U.S. Department of Energy summarizing how fission and fusion work. 
• Learn more about the ITER experiment on the project's website. 

Above our heads there is a powerful energy source created by nature, the Sun. Because the Sun is 93 million miles from us, only one-billionth of the Sun's total energy output reaches the Earth, creating a world blooming with life. The energy that the sun gives the Earth's surface every second is more than the total electricity generated from all power plants in the world in the entire year of 2018.

Here on Earth, humans power machines mostly by harvesting energy: for example, harvesting the energy of falling water and converting it to electricity in hydroelectric power plants. To create energy, you have to convert matter to energy.

Chain reactions

One way to do that is to split atoms, the basic building blocks of all matter in the universe. Do so controllably and you can produce a steady flow of energy. Lose control and you release a lot of energy all at once in a nuclear explosion.

The core of every atom, the nucleus, is made up of even smaller particles, protons and neutrons. The force holding the nucleus together stores a huge amount of energy. To obtain energy from the nucleus, scientists came up with a process of splitting a heavy atom into lighter atoms. Because the lighter atoms don't need as much energy to hold the nucleus together as the heavy atoms, energy is released as heat or light. This process is called nuclear fission.

When one atom is split, a chain reaction starts: The split atom will trigger another atom to be split, and so on. To make the chain reaction controllable, scientists developed ways to slow down the splitting, such as absorbing some of the split particles.

Nuclear power

Nuclear power plants harvest the energy released by splitting atoms controllably. The world's largest nuclear power plant is the Kashiwazaki-Kariwa Nuclear Power Station in Japan. It consists of seven nuclear reactors, with a maximum capacity of about 8,000 megawatts. The world's largest single nuclear reactor is a tie between the two reactors at China's Taishan Nuclear Power Plant. Each Taishan reactor has a capacity of 1,750 megawatts.

This amount of power is much smaller than uncontrolled nuclear reactions, such as atomic bombs. Nowadays, the energy output from detonating an atomic bomb is equivalent to the electricity the Kashiwazaki-Kariwa plant generates in half a year.

A downside of fission is nuclear waste. The split atoms are usually unstable and emit dangerous radiation. Nuclear waste needs to be stored properly for many years.

Nuclear fusion

Scientists have also discovered another type of nuclear reaction, one that produces energy without nuclear waste. As two lighter atoms combine into a heavy atom, the lost mass converts into energy. This process is called nuclear fusion. Fusion is happening in the core of the Sun. Every second, the sun burns about 600 million tons of hydrogen into about 596 million tons of helium, yielding energy equivalent to trillions of atomic bombs.

However, it is very difficult to achieve nuclear fusion on Earth. Fusion happens only at extreme conditions, such as the very high temperatures and pressure of the Sun. Scientists have yet to effectively demonstrate controllable nuclear fusion that produces more energy than it consumes, but they are working hard to do so. One way is to shoot high-power lasers from different directions at a tiny speck of hydrogen isotopes.

Nuclear fusion energy would be a promising energy solution in the future. But don't forget, we have a huge nuclear fusion reactor above our heads, the Sun. With the improving efficiency of solar energy, we don't even need to create energy, just capture more of what the Sun gives us every day.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

In 2019, a group of scientists and distillers decided to create a bold new type of booze: Atomik, an artisanal alcoholic spirit made from ingredients grown in the Chernobyl nuclear power plant's still-radioactive exclusion zone. (The booze itself was not radioactive after the distilling process, Live Science previously reported).

Now, the first batch of Atomik is finally complete — and all 1,500 bottles of it have been seized by Ukrainian Secret Services agents for unknown reasons, according to a statement from Atomik's manufacturer, The Chernobyl Spirit Company.

"It seems that they are accusing us of using forged Ukrainian excise stamps, but this doesn't make sense since the bottles are for the U.K. market and are clearly labelled with valid U.K. excise stamps," Jim Smith, founder of the company and a professor at the University of Portsmouth in the U.K., said in the statement.

Related: 5 weird things you didn't know about Chernobyl

Elina Smirnova, a lawyer representing the company, added that the seizure was a "clear violation" of Ukrainian law. If Atomik does make its way onto shelves, it will be the first consumer product from the Chernobyl region since the infamous 1986 meltdown, the company said.

Soon after the nuclear disaster, officials deemed the Chernobyl exclusion zone — the 1,000-square-mile (2,600 square kilometers) area surrounding the damaged power plant — uninhabitable by humans for 24,000 years. However, plants and animals are now thriving in the region — and so is tourism. According to local tourism officials, Chernobyl sees upwards of 60,000 visitors a year, with visits spiking after the May 2019 debut of HBO's "Chernobyl" miniseries.

Atomik is made from apples grown in Ukraine's Narodychi District, which sits on the edge of the exclusion zone and was heavily polluted by fallout from the meltdown. This region still has a population of nearly 10,000 people, according to Ukraine's State Statistics Service, and must abide by stringent agricultural restrictions.

With Atomik, Smith and his colleagues hope to prove that some products made near  the exclusion zone can be safe for consumption, according to the company's website. Several years ago, the Atomik team tested rye crops from the exclusion zone for radiation, and found that the grains were indeed contaminated. However, Smith said, all traces of radiation were removed during the distillation process, making Atomik no more dangerous than other commercially available spirits.

Since then, the founders have changed their recipe from a rye-based booze to an apple-based one — but, according to Smith, the distillation process still renders the final product completely radiation-free. If Atomik makes it to liquor shops, 75% of the company's profits will be used "to help bring jobs and investment to the Chernobyl affected areas of Ukraine and to further support the community," according to the company's statement.

In the meantime, would you care to try a bottle of wine exposed to cosmic radiation aboard a space station for 14 months? It'll only cost you $1 million.

Originally published on Live Science.

Iran announced that it is enriching uranium to 20% purity — does that mean they could develop a nuclear bomb?

The uranium enrichment process began at the Fordow nuclear facility in Iran on Monday (Jan. 4), according to the Islamic Republic News, the official news agency of the Iranian government. A purity of 20% far exceeds the limit of 3.67% allowed under the 2015 Iran nuclear deal, which President Donald Trump withdrew from in 2018, Live Science previously reported. 

Enriched uranium can be used in nuclear reactors and for the creation of nuclear bombs, but how significant is the 20% purity milestone?

"20% is the lowest enrichment that is considered practical for making a nuclear weapon," Edwin Lyman, Director of Nuclear Power Safety, Climate and Energy Program at the Union of Concerned Scientists, told Live Science in an email. "However, 20% is not a magical dividing line between weapon-usable and non-weapon-usable material," Lyman said. 

Related: Doomsday: 9 real ways Earth could end

What is enriched uranium? 

Uranium is a radioactive element that occurs naturally in the environment. Uranium found in the Earth's crust is primarily made up of two different isotopes, or forms of uranium, that differ based on their atomic weight. Uranium-238 is heavier than uranium-235 and much more common, making up more than 99% of natural uranium. 

The far more common uranium-238, however, can't be used in most nuclear reactors and cannot be used in nuclear bombs. For those purposes, uranium-235 is needed. That's because the lighter isotope is "fissile," which means that its nucleus can easily be split to trigger the nuclear chain reaction underlying both nuclear power and bombs. When a neutron slams into an atom of uranium-235, the nucleus splits, throwing off additional neutrons, which then collide with other uranium-235 atoms, generating a chain reaction of nuclear fission, Live Science previously reported. This generates heat, and in turn, energy.

In a nuclear bomb, the fission occurs at an ever-increasing rate in what is known as a supercritical reaction, until the energy is released in a massive blast. Achieving this supercritical reaction requires higher concentrations of uranium-235 than is required to generate nuclear power.

Uranium-238 can be split, but can't sustain this nuclear chain reaction.But through a complicated, resource-intensive chemical process known as enrichment, some uranium-235 in a sample can be separated from the uranium-238, thereby increasing the concentration of the more useful form of the element, Live Science previously reported. 

Engineers first use a chemical reaction to turn a sample of mined uranium ore (consisting of both uranium-238 and uranium-235 isotopes) into a gas. Centrifuges then spin the gas at high speeds. This generates an intense centrifugal force that pulls heavier uranium-238 isotopes towards the wall of the tube, leaving the lighter-235 isotopes closer to the center where they can be extracted, Live Science previously reported.

Only a small amount of uranium-238 is removed each time before the gas is moved to another tube, and then another and so on, to slowly increase the concentration of uranium-235 through hundreds of thousands of spins. 

The most common nuclear reactors use fuel enriched to contain between 3% and 5% uranium-235. For nuclear weapons, uranium is typically enriched all the way to 90%. 

However, according to Lyman, this doesn't necessarily have to be the case. Furthermore, a plant designed to create fuel for nuclear power can also be "easily reconfigured" to produce material for nuclear weapons, Lyman said. 

How close is Iran to making a bomb?

Iran insists that its nuclear program is peaceful and that they are simply retaliating against U.S. sanctions imposed on them by Trump, according to BBC News. 

The 2015 Iran nuclear deal, also known as the Joint Comprehensive Plan of Action (JCPOA), was created between Iran and a group of five nations (China, France, Germany, Russia, the United Kingdom and the United States) in order to ensure Iran's nuclear program would remain exclusively peaceful. By limiting the scope of Iran's nuclear program, including enrichment activities and research and development, the deal extended the time it would take Iran to produce enough material for nuclear weapons to at least a year. 

By breaking these limitations, Lyman says that time — known as the "breakout time" — has decreased, meaning they are developing their nuclear program beyond what was agreed and are getting closer to being able to create nuclear weapons more quickly if that is their intent. "My guess is that it is well below a year at this point (if it ever really was greater than a year)," Lyman said. 

However, that does not mean that Iran will try to make nuclear weapons or that the current developments can't be rolled back, Lyman said.

Originally published on Live Science.

Crops grown near the Chernobyl nuclear site in Ukraine are still contaminated with radiation from the explosive 1986 disaster. 

In a new study, researchers found that wheat, rye, oats and barley grown in this area contained two radioactive isotopes — strontium 90 and cesium 137 — that were above safe consumption limits. Radioactive isotopes are elements that have increased masses and release excess energy as a result.

"Our findings point to ongoing contamination and human exposure, compounded by lack of official routine monitoring,” study author David Santillo, an environmental forensic scientist at Greenpeace Research Laboratories at the University of Exeter, said in a statement, referring to the fact that the government suspended its radioactive goods monitoring program in 2013. 

Related: 5 weird things you didn't know about Chernobyl

Santillo and his colleagues, in collaboration with researchers from the Ukrainian Institute of Agricultural Radiology, analyzed 116 grain samples, collected between 2011 and 2019, from the Ivankiv district of Ukraine — about 31 miles (50 kilometers) south of the nuclear plant. 

This area is outside of Chernobyl's "exclusion zone," which is a 30 mile (48 km) radius around the plant that was evacuated in 1986 and has remained unoccupied. They found radioactive isotopes, predominantly strontium 90, were above safe consumption level in 48% of samples. They also found that wood samples collected from the same region between 2015 and 2019, had strontium 90 levels above the safe limit for firewood.

The researchers believe that the lingering radiation in the wood, in particular, may be the reason for the continued contamination of crops, almost 35 years after the disaster. When analyzing the wood ash from domestic wood-burning ovens, they found strontium 90 levels that were 25 times higher than the safe limit. Locals use this ash, as well as ash from the local thermal power plant (TPP), to fertilize their crops, which continues to cycle the radiation through their soil. 

However, computer simulations suggest that it could be possible to grow crops in the region at "safe" levels if this process of repeated contamination ceased. The researchers are now calling for the Ukrainian government to reinstate its monitoring program and create a system for properly disposing of radioactive ash. 

"Contamination of grain and wood grown in the Ivankiv district remains of major concern and deserves further urgent investigation,” study author Valery Kashparov, director of the Ukrainian Institute of Agricultural Radiology, said in the statement. "Similarly, further research is urgently needed to assess the effects of the Ivankiv TPP on the environment and local residents, which still remain mostly unknown."

The findings were published on Dec. 17 in the journal Environment International.

Originally published on Live Science.

Radioactivity levels have spiked in the atmosphere over northern Europe, and that could indicate damage at a nuclear power plant in western Russia, according to a Dutch health agency that has analyzed the data. The radioactive spike suggests damage to a nuclear fuel element, the Associated Press reported.

However, the Russian nuclear power operator Rosenergoatom has denied problems related to facilities in Kola and Leningrad, the two nuclear plants operating in the region, according to TASS, a Russian news agency, as reported by the AP.

Related: 5 weird things you didn't know about Chernobyl

Several Scandinavian watchdog agencies detected the elevated levels of the radionuclides (or radioactive isotopes). Radionuclides are atoms whose nuclei are unstable; the excess energy inside the nucleus gets released through radioactive decay. In particular, concentrations of the radionuclides cesium-134, cesium-137 and ruthenium-103 rose in parts of Finland, southern Scandinavia and the Arctic, Lassina Zerbo, the Executive Secretary of the Comprehensive Nuclear-Test-Ban Treaty Organization, wrote on Twitter. Though these pose no harm to humans, they are byproducts of nuclear fission, Zerbo wrote. 

"The radionuclides are artificial, that is to say they are man-made. The composition of the nuclides may indicate damage to a fuel element in a nuclear power plant," an official with the National Institute for Public Health and the Environment in the Netherlands, which analyzed the isotope data, said on Friday (June 26).

Because so few measurements have been taken, monitoring agencies weren't able to identify a specific source, NIPHE officials said.

The sudden radioactivity spike echoes the events following the Chernobyl nuclear meltdown, the biggest nuclear disaster in history. Within a few days of the 1986 disaster, a Swedish nuclear power plant detected elevated radioactivity levels, according to an account from the European parliament.

In recent years, another radioactive mystery cloud wafting over Europe was tied to Russia. In 2017, a plume holding 1,000 times the normal levels of ruthenium-106 was detected over Europe, The Washington Post reported. Russia denied any involvement, though a nuclear reprocessing plant in Russia was a strong suspect, according to a 2019 study in the journal Proceedings of the National Academy of Sciences.

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Originally published on Live Science.

An explosion off Russia's Arctic coast has led to speculation that the incident resulted from a failed test of a nuclear-powered cruise missile. But do the details of the deadly blast point to such a weapon — one that no country has yet successfully created — and if so, what would that mean for global warfare?

Russian authorities have confirmed that five scientists were killed in the incident on a sea platform close to the coastal town of Nenoksa last Thursday (Aug. 8), but the country has released few details. The Russian Ministry of Defense initially said that the incident involved a liquid-fuel rocket engine and that no dangerous substances were released, but reports of a sudden rise in radiation levels in the nearby city Severodvinsk cast doubt on those claims.

Russia watchers quickly linked the incident to the development of a nuclear-powered cruise missile called 9M730 Burevestnik, announced by Russian President Vladimir Putin last year, Reuters reported. And on Sunday (Aug. 11),  an official at the state nuclear agency Rosatom admitted that the institute where the scientists were working was investigating nuclear power sources, according to another Reuters report.

Related: The 10 Most Dangerous Space Weapons Ever

Aircraft and missiles that rely on a nuclear reactor rather than the burning of fuel to provide propulsion aren't an entirely new idea, said Edwin Lyman, acting director of the Nuclear Safety Project at the Union of Concerned Scientists. Both the U.S. and the Soviet Union investigated the idea during the Cold War but ultimately abandoned the efforts due to the complexity and safety concerns around flying nuclear reactors and the advent of intercontinental ballistic missiles that provided a simpler alternative.

"It was even too crazy for the Cold War Atomic Energy Commission to consider, which means it was really far out there," Lyman told Live Science. "That is why so many people were surprised when Putin declared they were doing it again."

The motivation for the idea is that nuclear power provides energy over much longer periods than conventional fuels, Lyman said. Nuclear reactors generate power by capturing heat produced by large atoms splitting into smaller ones in a process called fission; and this process can release huge amounts of energy from a small amount of fuel, providing a very long-lived power source. That longevity would give a missile incredibly long range, so it could spend months in the air and take a circuitous route to evade any missile defenses.

Few details have been released about how Russia proposes to integrate a nuclear power source into a missile, Lyman said. But the project has frequently been compared to the U.S. Supersonic Low Altitude Missile (SLAM), a planned uncrewed aircraft that would have flown below radar at supersonic speeds to deliver multiple nuclear warheads deep into enemy territory.

The SLAM project was canceled in 1964, but the weapon was to be propelled by a ramjet. This type of jet engine specializes in high speeds and uses the aircraft's forward motion to compress air as it enters the engine rather than doing so via fan blades as conventional jets do. But instead of burning jet fuel to heat the compressed air and provide thrust, as other ramjets and conventional jets do, the proposed vehicle would have used thermal energy generated by an onboard nuclear reactor.

There are reasons to believe that the weapon Russia is developing would be significantly different from the U.S. proposal, though, said Edward Geist, a policy researcher and Russia expert at the RAND Corporation, a think tank.

"While few technical details have been revealed about Burevestnik, the Russian media has reported repeatedly that it is a subsonic system," he told Live Science. That would appear to rule out a ramjet design, as these operate only at supersonic speeds, he said, suggesting that the missile is a descendant of Soviet-era research into “closed-cycle” nuclear propulsion of  aircraft designed to fly below the speed of sound.

Related: Could the US Stop Nuclear Weapons?

The SLAM reactor was designed to use an “open-cycle” approach where the compressed air was heated by putting it in direct contact with the fuel rods - the ceramic tubes holding radioactive uranium or plutonium isotopes that go through fission to produce energy. These rods  produce tremendous amounts of heat, but  also spew radioactive material that would end up in the engine’s exhaust in an open-cycle approach. Russia's closed-cycle technology, however, would use some kind of heat exchanger to transfer energy from the reactor to the air without the two coming in contact, Geist said.

Regardless of the specific design, Lyman said a number details call into question whether the Burevestnik system was even involved in the incident. Most proposals for nuclear-powered missiles would use a conventional rocket engine to get them airborne before switching on the reactor, he said. But this explosion occurred on the platform. Fresh fuel that has yet to undergo fission isn't that radioactive, he said, so it's unlikely an inactive reactor could have caused the kind of radiation spike recorded in Severodvinsk.

Geist agreed and added that the test site appears to have been too close to populated areas to be carrying out potentially dangerous tests on an unshielded nuclear reactor. "But if they're only testing non-nuclear components of Burevestnik there, why have the reactor present at all?" Geist said.

Rosatom claims the explosion involved a "nuclear battery," Geist said, though he added that statements from Russian officials are not reliable sources of information. This statement appears to refer to a device that generates energy by harnessing the heat from decaying radioactive materials rather than from nuclear fission. The approach has been used to power spacecraft, but Lyman pointed out that it's highly unlikely to produce enough thrust to power a cruise missile.

All that makes pinning the incident on Burevestnik somewhat premature, Geist said, especially as there are other potential culprits. Putin unveiled the Burevestnik missile last year as part of a suite of "superweapons" that included a nuclear-powered torpedo dubbed Poseidon; Putin also suggested there were other systems under development that have yet to be publicly announced.

The Russian president linked the development of those weapons to the 2002 U.S. withdrawal from the Anti-Ballistic Missile Treaty, which banned systems designed to shoot down nuclear-armed missiles.

"These systems are intended to make the development of comprehensive strategic defenses look as complicated and forbidding as possible to potential adversaries, particularly the United States," Geist said.

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Originally published on Live Science.

A vast cloud of nuclear radiation that spreadover continental Europe in 2017 has been traced to an unacknowledged nuclear accident in southern Russia, according to an international team of scientists.

The experts say the cloud of radiation detected over Europe in late September 2017 could only have been caused by a nuclear fuel-reprocessing accident at the Mayak Production Association, a nuclear facility in the Chelyabinsk region of the Ural Mountains in Russia, sometime between noon on Sept. 26 and noon on Sept. 27.

Russia confirmed that a cloud of nuclear radiation was detected over the Urals at the time, but the country never acknowledged any responsibility for a radiation leak, nor has it ever admitted that a nuclear accident took place at Mayak in 2017. [Top 10 Greatest Explosions Ever]

The lead author of the new research, nuclear chemist Georg Steinhauser of Leibniz University in Hanover, Germany, said that more than 1,300 atmospheric measurements from around the world showed that between 250 and 400 terabecquerels of radioactive ruthenium-106 had been released during that time.

Ruthenium-106 is a radioactive isotope of ruthenium, meaning that it has a different number of neutrons in its nucleus than the naturally occurring element has. The isotope can be produced as a byproduct during nuclear fission of uranium-235 atoms.

Although the resulting cloud of nuclear radiation was diluted enough that it caused no harm to people beneath it, the total radioactivity was between 30 and 100 times the level of radiation released after the Fukushima accident in Japan in 2011, Steinhauser told Live Science.

The research was published today (July 29) in the journal Proceedings of the National Academy of Sciences.

Ruthenium release

The cloud of radiation in September 2017 was detected in central and eastern Europe, Asia, the Arabian Peninsula and even the Caribbean.

Only radioactive ruthenium-106 — a byproduct of nuclear fission, with a half-life of 374 days — was detected in the cloud — Steinhauser said.

During the reprocessing of nuclear fuel — when radioactive plutonium and uranium are separated from spent nuclear fuel from nuclear power reactors — ruthenium-106 is typically separated out and placed into long-term storage with other radioactive waste byproducts, he said.

That meant that any massive release of ruthenium could only come from an accident during nuclear fuel reprocessing; and the Mayak facility was one of only a few places in the world that carries out that sort of reprocessing, he said.

Advanced meteorological studies made as part of this new research showed that the radiation cloud could only have come from the Mayak facility in Russia. "They have done a very thorough analysis and they have pinned down Mayak — there is no doubt about it," he said.

The accident came a little more than 60 years since a nuclear accident at Mayak in 1957 caused one of the largest releases of radiation in the region's history, second only to the 1986 explosion and fire at the Chernobyl nuclear power plant, which is now in the Ukraine. [Chernobyl Nuclear Disaster 25 Years Later (Infographic)]

In the 1957 accident, known as the Kyshtym disaster after a nearby town, a tank of liquid nuclear waste at the Mayak facility exploded, spreading radioactive particles over the site and causing a radioactive plume of smoke that stretched for hundreds of miles.

Nuclear accident

The study showed that the 2017 accident at Mayak was unlikely to have been caused by a relatively simple release of radioactive gas, Steinhauser said. Rather, a fire, or even an explosion, might have exposed workers at the plant to harmful levels of radiation, he added.

Russia has not acknowledged that any accident occurred at the Mayak facility, maybe because plutonium is made there for thermonuclear weapons. However, Russia had established a commission to investigate the radioactive cloud, Steinhauser said.

The Russian commission ruled that there was not enough evidence to determine if a nuclear accident was responsible for the cloud. But Steinhauser and his team hope it may look again at this decision in the light of the new research.

"They came to the conclusion that they need more data," he said. "And so we feel like, okay, now you can have all of our data — but we would like to see yours as well."

Any information from Russia about an accident at the Mayak facility would help scientists refine their research, instead of having to rely only on measurements of radioactivity from around the world, Steinhauser said.

The international team of scientists involved are keenly interested in learning more about its causes. "When everybody else is concerned, we are almost cheering for joy, because we have something to measure," he said. "But it is our responsibility to learn from this accident. This is not about blaming Russia, but it is about learning our lessons," he said.

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Originally published on Live Science.

Audiences have been gripped by Chernobyl, the HBO/Sky series that charts the events and aftermath of the Chernobyl nuclear power plant disaster of April 1986.

I have coordinated a number of international research projects on the impacts of the Chernobyl accident, and made dozens of visits to the Exclusion Zone around Chernobyl. There has been considerable praise for the attention to detail in the sets, props and clothes that helped immerse viewers in a sense of being in late-period Soviet society — including from those that remember it first hand. But there are also errors, or aspects of how the story plays out that have been invented to add drama to the story.

Related: 5 Weird Things You Didn't Know About Chernobyl

1. The helicopter crash

The dramatic scene early on in which a helicopter crashes while attempting to fly over the reactor — apparently due to the intense radiation — never happened. But helicopter video footage taken at the time shows static and distortions generated by the intense radiation field above the reactor core, and there were reports of pilots getting radiation sickness from their sorties.

2. The 'Bridge of Death'

The unforgivably late response of the authorities meant that citizens of Pripyat were out in the open after the accident — and some did go to the so-called "bridge of death" nearer the plant to watch the fire. But I've seen no evidence that all the people on the bridge died, and no evidence that radiation doses there were so dangerously high.

3. Radiation sickness in Pripyat

In fact, on average, residents of Pripyat received an average dose of around 30 millisieverts (mSv) — about the same as three whole-body CT scans - due to the late warning about the danger. There is a scene in the local hospital that appears to show children suffering from radiation sickness: Experts confirmed 134 cases of radiation sickness among the firemen and plant operators, but none among the population of Pripyat.

Related: Why did people take iodine pills after Chernobyl exploded?

4. 'You're sitting next to a nuclear reactor'

In highly emotional scenes we see the pregnant wife of a firefighter visiting her husband suffering from acute radiation syndrome in Moscow Hospital Number Six. This happened, and is one of numerous first-hand accounts the series draws from Voices from Chernobyl by the Belarussian journalist and Nobel laureate Svetlana Alexievich. But the drama implies that the baby absorbed such high doses of radiation from the husband that it subsequently died. A US doctor who helped treat the plant workers and firefighters says that the patients didn't present a significant radiation risk to staff and visitors. Studies after Chernobyl have found no convincing evidence that pregnancy outcomes were affected by radiation exposures.

5. Reactors aren't nuclear bombs

The fears of a nuclear explosion in the two to four-megatonne range due to reactor core meltdown, which, it was claimed, would destroy the nearby city of Kiev and make large areas of Europe uninhabitable, turned out to be wrong. Nuclear power stations don't explode like nuclear bombs — and certainly not thermonuclear ones in the megatonne range. In any case, such an explosion wouldn't have destroyed Minsk, nor would it have made Europe uninhabitable.

Related: 10 Chernobyl-Style Reactors Still Operate Across Russia

6. The divers

The three heroic men who worked to drain the tanks of water below the primary containment chamber to prevent nuclear fuel coming into contact with water which was believed would cause an explosion did so in vain. Subsequent analysis found that the tanks were already mostly empty, and the interaction of the melting fuel with the water might even have helped cool it.

7. The helicopter pilots

The incredibly brave attempts by helicopter pilots to drop boron, sand and lead onto the melting fuel rods likely helped to put out the fire burning in the graphite moderator, but it largely missed the nuclear fuel and the melted core which, after burning through the primary containment, cooled down by itself.

Related: Is It Safe to Visit Chernobyl?

8. The miners

The brave miners who made huge efforts to dig a tunnel under the reactor building to install a heat exchanger to remove heat from under the core also did so in vain: the heat exchanger was never used as the core cooled before it was installed. The risk of radioactivity entering the water table under the reactor (sited near a lake and river system) was found to be elevated, but still low.

9. The liquidators

At the end of the series, claims about the aftermath shown onscreen imply that no studies were made of the hundreds of thousands of liquidators who cleaned up after the accident. In fact there were many studies of this group, and they have proved inconclusive on whether there was an increase in cancer. It is likely they did experience an increased cancer risk, but this was very small compared to the many other health risks they faced and continue to face, including cardiovascular disease, smoking and — a general problem across former Soviet countries — excess alcohol consumption.

Related: How Did Radiation Affect the 'Liquidators' of the Chernobyl Nuclear Meltdown?

10. Failings

Scientists come out as heroes from the show. While there were countless heroes, including scientists, in the aftermath of Chernobyl, ultimately the Soviet scientific community as well as its political system was responsible for the design flaws of the RBMK reactor, the lack of safety culture, and unforgivable lack of preparedness for such an accident.

A cautionary tale

It is important not to underestimate the consequences of the Chernobyl disaster. Studies have found an increase in thyroid cancer, mainly due to the failure of the Soviet authorities to prevent consumption of products contaminated with short-lived radioactive iodine-131 in the weeks after the accident.

Recent analyses of affected populations up to 2015 found 5,000 out of a total of 20,000 thyroid cancer cases to be due to radiation. Fortunately, though serious, thyroid cancer is treatable in 99% of cases. Some reports suggest that the consequences of relocating hundreds of thousands of people, the economic consequences of abandonment of land and the understandable fear of radiation have had greater negative effects than the direct health consequences of radiation.

Chernobyl the series is amazing to watch, and the reconstruction of events before and during the accident was remarkable. But we should remember that it is a drama, not a documentary. In the years since 1986, many myths have been perpetuated about the accident, and these myths have unquestionably hindered the recovery of the affected populations.

More than 30 years on, this recovery continues. If it is to have any chance of success it must be based not on the emotion and the drama, but on the best available scientific evidence. Evidence which shows that, except at the extreme doses which plant operators, firemen and helicopter pilots received during the Chernobyl disaster, the risks of radiation are tiny compared to other health risks we all face in our lives.

Jim Smith, Professor of Environmental Science, University of Portsmouth

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Editor's Note: This story was updated on Monday, June 10 at 4:45 p.m. E.D.T.

In the new HBO miniseries "Chernobyl," Russian scientists uncover the reason for an explosion in Reactor 4 at the Chernobyl Nuclear Power Plant, which spewed radioactive material across northern Europe.

That reactor, a design called the RBMK-1000, was discovered to be fundamentally flawed after the Chernobyl accident. And yet there are still 10 of the same type of reactor in operation in Russia. How do we know if they're safe?

The short answer is, we don't. These reactors have been modified to lessen the risk of another Chernobyl-style disaster, experts say, but they still aren't as safe as most Western-style reactors. And there are no international safeguards that would prevent the construction of new plants with similar flaws. [Images: Chernobyl, Frozen in Time]

"There are a whole number of different types of reactors that are being considered now in various countries that are significantly different from the standard light-water reactor, and many of them have safety flaws that the designers are downplaying," said Edwin Lyman, a senior scientist and the acting director of the Nuclear Safety Project at the Union of Concerned Scientists.

"The more things change," Lyman told Live Science, "the more they stay the same."

Reactor 4

At the center of the Chernobyl disaster was the RBMK-1000 reactor, a design used only in the Soviet Union. The reactor was different from most light-water nuclear reactors, the standard design used in most Western nations. (Some early U.S. reactors at the Hanford Site in Washington state were a similar design with similar flaws, but were fixed in the mid-1960s.)

Light-water reactors consist of a large pressure vessel containing nuclear material (the core), which is cooled by a circulating supply of water. In nuclear fission, an atom (uranium, in this case), splits, creating heat and free neutrons, which zing into other atoms, causing them to split and release heat and more neutrons. The heat turns the circulating water to steam, which then turns a turbine, generating electricity.

In light-water reactors, the water also acts as a moderator to help control the ongoing nuclear fission within the core. A moderator slows down free neurons so that they're more likely to continue the fission reaction, making the reaction more efficient. When the reactor heats up, more water turns to steam, and less is available to play this moderator role. As a result, the fission reaction slows. That negative feedback loop is a key safety feature that helps keep the reactors from overheating.

The RBMK-1000 is different. It also used water as a coolant, but with graphite blocks as the moderator. The variations in the reactor design allowed it to use less-enriched fuel than usual and to be refueled while running. But with the coolant and moderator roles separated, the negative feedback loop of "more steam, less reactivity," was broken. Instead, RBMK reactors have what's called a "positive void coefficient."

When a reactor has a positive void coefficient, the fission reaction speeds up as the coolant water turns to steam, rather than slowing down. That's because boiling opens up bubbles, or voids, in the water, making it easier for neutrons to travel right to the fission-enhancing graphite moderator, said Lars-Erik De Geer, a nuclear physicist who is retired from the Swedish Defence Research Agency.

From there, he told Live Science, the problem builds: The fission becomes more efficient, the reactor gets hotter, the water gets steamier, the fission becomes more efficient still, and the process continues.

Run-up to disaster

When the Chernobyl plant was running at full power, this wasn't a big problem, Lyman said. At high temperatures, the uranium fuel that powers the fission reaction tends to absorb more neutrons, making it less reactive.

At low power, though, RBMK-1000 reactors become very unstable. In the run-up to the Chernobyl accident on April 26, 1986, operators were doing a test to see if the plant's turbine could run emergency equipment during a power outage. This test required running the plant at reduced power. While the power was lowered, the operators were ordered by Kiev's power authorities to pause the process. A conventional plant had gone offline, and Chernobyl's power generation was needed.

"That was very much the main reason why it all happened in the end," De Geer said.

The plant ran at partial power for 9 hours. When the operators got the go-ahead to power most of the rest of the way down, there had been a buildup of neutron-absorbing xenon in the reactor, and they couldn't maintain the appropriate level of fission. The power fell to nearly nothing. Trying to boost it, the operators removed most of the control rods, which are made of neutron-absorbing boron carbide and are used to slow the fission reaction. Operators also reduced the flow of water through the reactor. This exacerbated the positive void coefficient problem, according to the Nuclear Energy Agency. Suddenly, the reaction became very intense indeed. Within seconds, the power surged to 100 times what the reactor was designed to withstand. [Chernobyl Nuclear Disaster 25 Years Later (Infographic)]

There were other design flaws that made it difficult to get the situation back under control once it started. For example, the control rods were tipped with graphite, De Geer says. When the operators saw that the reactor was starting to go haywire and tried to lower the control rods, they got stuck. The immediate effect was not to slow the fission, but to enhance it locally, because the additional graphite at the tips initially boosted the fission reaction's efficiency nearby. Two explosions rapidly followed. Scientists still debate exactly what caused each explosion. They both may have been steam explosions from the rapid increase in pressure in the circulation system, or one may have been steam and the second a hydrogen explosion caused by chemical reactions in the failing reactor. Based on the detection of xenon isotopes at Cherepovets, 230 miles (370 kilometers) north of Moscow after the explosion, De Geer believes that the first explosion was actually a jet of nuclear gas that shot several kilometers into the atmosphere.

Changes made

The immediate aftermath of the accident was "a very unnerving time" in the Soviet Union, said Jonathan Coopersmith, a historian of technology at Texas A&M University who was in Moscow in 1986. At first, the Soviet authorities kept information close; the state-run press buried the story, and the rumor mill took over. But far away in Sweden, De Geer and his fellow scientists were already detecting unusual radioactive isotopes. The international community would soon know the truth.

On May 14, Soviet leader Mikhail Gorbachev gave a televised speech in which he opened up about what had happened. It was a turning point in Soviet history, Coopersmith told Live Science.

"It made glasnost real," Coopersmith said, referring to the nascent policy of transparency in the Soviet Union.

It also opened a new era in cooperation for nuclear safety. In August 1986, the International Atomic Energy Agency held a post-accident summit in Vienna, and Soviet scientists approached it with an unprecedented sense of openness, said De Geer, who attended.

"It was amazing how much they told us," he said.

Among the changes in response to Chernobyl were modifications to the other RBMK-1000 reactors in operation, 17 at the time. According to the World Nuclear Association, which promotes nuclear power, these changes included the addition of inhibitors to the core to prevent runaway reactions at low power, an increase in the number of control rods used in operation and an increase in fuel enrichment. The control rods were also retrofitted so that the graphite would not move into a position that would increase reactivity.

Chernobyl's other three reactors operated till 2000 but have since closed, as have two more RBMKs in Lithuania, which were shut down as a requirement of that country entering the European Union. There are four RBMK reactors operating in Kursk, three in Smolensk and three in St. Petersburg (a fourth was retired in December 2018).

These reactors "aren't as good as ours," De Geer said, "but they are better than they used to be."

"There were fundamental aspects of the design that couldn't be fixed no matter what they did," Lyman said. "I would not say they were able to increase the safety of the RBMK overall to the standard you'd expect from a Western-style light water reactor."

In addition, De Geer pointed out, the reactors weren't built with full containment systems as seen in Western-style reactors. Containment systems are shields made of lead or steel meant to contain radioactive gas or steam from escaping into the atmosphere in the event of an accident.

Oversight overlooked?

Despite the potentially international effects of a nuclear plant accident, there is no binding international agreement on what constitutes a "safe" plant, Lyman said.

The Convention on Nuclear Safety requires countries to be transparent about their safety measures and allows for peer review of plants, he said, but there are no enforcement mechanisms or sanctions. Individual countries have their own regulatory agencies, which are only as independent as local governments enable them to be, Lyman said.

"In countries where there is rampant corruption and lack of good governance, how can you expect that any independent regulatory agency is going to be able to function?" Lyman said.

Though no one besides the Soviet Union made RBMK-1000 reactors, some proposed new reactor designs do involve a positive void coefficient, Lyman said. For example, fast-breeder reactors, which are reactors that generate more fissile material as they generate power, have a positive void coefficient. Russia, China, India and Japan have all built such reactors, though Japan’s is not operational and is planned for decommission and India’s is 10 years behind schedule for opening. (There are also reactors with small positive void coefficients operating in Canada.)

"The designers are arguing that if you take everything into account, overall they're safe, so that doesn't matter that much," Lyman said. But designers shouldn't be overconfident in their systems, he said.

"That kind of thinking is what got the Soviets into trouble," he said. "And it's what can get us into trouble, by not respecting what we don't know."

Editor's Note: This story was updated to note that most, but not all, of the control rods were removed from the reactor, and to note that some early reactors in the United States also had a positive void coefficient, though their design flaws were fixed.

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Originally published on Live Science.

Negotiations over denuclearization of North Korea collapsed this morning after North Korean dictator Kim Jong Un insisted the United States lift all economic sanctions in return for any nuclear disarmament.

U.S. Secretary of State Mike Pompeo said that talks with North Korea will soon resume, according to the Associated Press. However, before the Trump administration announced the lack of agreement, U.S. negotiators had already backed off the demand that Kim and his government allow access and transparency to the international community concerning their nuclear weapons program.

North Korea, like all countries with a nuclear program, is quite secretive about its research and testing. No one knows exactly how much nuclear material North Korea has or even exactly what kinds of warheads they've developed. [North Korea: A Hermit Country from Above (Photos)]

But North Korea won't necessarily have to let the entire world poke around its nuclear facilities to show that they've slowed or stopped their pursuit of nuclear arms. According to nuclear security experts, there are many ways to monitor the situation remotely — but they can provide only limited information without North Korea's cooperation.

"There is a whole panoply of technologies," said Sharon Squassoni, a professor and nuclear security expert at The George Washington University.

Testing, testing

North Korea has been claiming to be on the verge of shutting down its nuclear weapons program for as long as the country has admitted to having nuclear weapons. In 2005, then-leader Kim Jong Il admitted the country had nukes, and then signed an international statement promising to abandon its nuclear weapons program. In 2006, the country tested its first nuclear bomb.

That history of failed negotiations has security experts cautious about any potential for progress to be made between Trump and Kim, particularly since neither side has been very clear on what they consider "denuclearization," Squassoni said. Still, the meeting did represent an opportunity to bring North Korea back into a dialogue, said Alexander Glaser, the director of the Nuclear Futures lab at Princeton University. Even if North Korea refuses to share full information about its program, Glaser said, it might be possible to create a phased approach involving some remote monitoring and some onsite inspections that could prove whether the country is really meeting its promises.

The easiest aspect of the program to track is whether North Korea is actively testing nuclear bombs. North Korea's cooperation is not required. Nuclear explosions are pretty obvious, and the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) already runs a commission to monitor the atmosphere, oceans and subsurface for any testing. Infrasound monitors are capable of detecting aboveground explosions, and underwater microphones can detect undersea testing (both of which were banned under the Partial Nuclear Test Ban Treaty of 1963).

Underground nuclear tests show up on seismometers that are designed to detect earthquakes. There are many such arrays, run by research organizations, governments and even private entities, and quite a few of those upload all their data online, said Jeffrey Park, a geophysicist at Yale University. That means that anyone with an internet connection can detect an underground nuclear test, as long as they know what to look for. [The 22 Weirdest Military Weapons]

"We ordinarily have fairly good ideas about where nuclear testing is going on," Park said, "So any kind of tremor near a nuclear test site attracts a lot of attention."

Nuclear tests create a lot of what geophysicists call "p-waves," which are compressional waves created by the big blast pushing everything outward, all at once. These waves look quite different from the signals created by earthquakes, Park said. Earthquakes are caused by faults sliding side-by-side, so their seismic signals are dominated by shear-wave energy.

Knowns and unknowns

Thanks to remote seismic monitoring, the international community can tell within seconds to minutes if Kim's regime has denoted something at its underground testing site, Punggye-ri. By triangulating the source of waves detected at different seismic stations, scientists can even tell exactly where at the site the explosions occurred, even if they were as close as a kilometer apart from one another. North Korea detonated bombs at Punggye-ri in 2006, 2009, 2013, 2016 and 2017. The first two tests are widely considered to be failures, Park said. The 2013 and 2016 tests, he said, were indicative of a first-generation plutonium fission bomb, not unlike the bomb dropped on Nagasaki in 1945.

North Korea claims that the 2016 and 2017 bombs were both thermonuclear, or hydrogen bombs, which generate explosions via nuclear fusion rather than fission. Some outside experts think the North Korean government really does have a thermonuclear bomb, though others, including Park, are skeptical. For the purpose of gaining recognition on the world stage, Pyongyang would like everyone to believe its nuclear program is strong, Park said, but it's not clear that the testing done so far indicates the existence of a thermonuclear bomb.

"There's a lot we don't know," Squassoni said.

Many of those unknowns are challenging to fill in without cooperation from Kim's regime. For example, Squassoni said, North Korea has only one plutonium reactor, so outside experts could make an educated guess as to how much plutonium the country had to work with. But intelligence operations and one 2010 tour given to Stanford University experts have revealed that North Korea can also enrich uranium, which is done in facilities that are far easier to hide than a huge reactor. There is at least one uranium-enrichment facility in the country, Glaser said, and probably at least one more at an unknown location. (Either uranium or plutonium can be used to make nuclear weapons.)

"There may even be a third site that we are not aware of," he said.

Another easy-to-conceal facet of the nuclear program is the development of delivery systems. It does North Korea little good to have a 1945-style bomb, Park said; those require delivery by enormous bombers. What the country needs to be truly threatening is a warhead that can be delivered by missile. North Korea suspended missile launches in 2018, and maintaining that moratorium was almost certainly part of the negotiations in Hanoi, Glaser said.

Remote cooperation

Learning about what's going on inside nuclear facilities is a tough challenge, said Squassoni, who once worked in the U.S. State Department and who is now on the board of the Bulletin of the Atomic Scientists (the group responsible for the Doomsday Clock). Informants on the inside are hard to come by. And North Korea is not likely to hand over a list off all their facilities to the international community. [Doomsday: 9 Real Ways Earth Could End]

"We have a ballpark sense of the nuclear program, but I'm sure there would be some surprises if we got access," Squassoni said.

If the North Korean government were willing to let out even a little information at a time, the world could monitor much of their activity from afar, Glaser said. Satellite reconnaissance can be used to ensure that there is no activity at plutonium- or uranium- production facilities; the same can be true for missile-launch sites (which are still being maintained despite the moratorium on launches). Air monitoring and soil or vegetation samples could show any hint of production of radioactive materials. With enough information and enough time, scientists could conduct a sort of "nuclear archaeology," Glaser said, by figuring out how much uranium had been mined in North Korea and then comparing that to the number of warheads the country claims. That accounting could make it clear whether the country was hiding anything.

Even in a best-case scenario, confirmation of denuclearization couldn't happen overnight, Glaser said.

"It will take years to confirm the completeness of the declaration, or to have high confidence in the absence of undeclared items," he said. "There is no way around this."

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Originally published on Live Science.

A private nuclear-fusion company has heated a plasma of hydrogen to 27 million degrees Fahrenheit  (15 million degrees Celsius)  in a new reactor for the first time — hotter than the core of the sun.

UK-based Tokamak Energy says the plasma test is a milestone on its quest to be the first in the world to produce commercial electricity from fusion power, possibly by 2030.

The company, which is named after the vacuum chamber that contains the fusion reaction inside powerful magnetic fields, announced the creation of the superhot plasma inside its experimental ST40 fusion reactor in early June.

The successful test – the highest plasma temperature achieved so far by Tokamak Energy – means the reactor will now be prepared next year for a test of an even hotter plasma, of more than 180 million degrees F (100 million degrees C).

That will put the ST40 reactor within the operating temperatures needed for controlled nuclear fusion; the company plans to build a further reactor by 2025 that will produce several megawatts of fusion power.

"It's been really exciting," Tokamak Energy co-founder David Kingham told Live Science. "It was very good to see the data coming through and being able to get the high-temperature plasmas — probably beyond what we were hoping for." [Science Fact or Fiction? The Plausibility of 10 Sci-Fi Concepts]

Tokamak Energy is one of several privately funded companies racing to create a working fusion reactor that can supply electricity to the grid, perhaps years before the mid-2040s, when the ITER fusion reactor project in France is expected to even achieve its "first plasma."

It could be another decade after that before the experimental ITER reactor is ready to create sustained nuclear fusion — and even then, the reaction will not be used to generate any electricity.

Star in a jar

The nuclear fusion of hydrogen into the heavier element helium is the main nuclear reaction that keeps our sun and other stars burning for billions of years — which is why a fusion reactor is sometimes likened to a "star in a jar."

Nuclear fusion also takes place inside powerful thermonuclear weapons, also known as hydrogen bombs, where hydrogen is heated to fusion temperatures by plutonium fission devices, resulting in an explosion hundreds or thousands of times more powerful than a fission bomb.  

Earthbound controlled fusion projects like ITER and the Tokamak Energy reactors will also fuse hydrogen fuel, but at much higher temperatures and lower pressures than exist inside the sun.

Proponents of nuclear fusion say it could make many other types of electricity generation obsolete, by producing large amounts of electricity from relatively small amounts of the heavy hydrogen isotopes deuterium and tritium, which are relatively abundant in ordinary seawater.

"Fifty kilograms [110 lbs.] of tritium and 33 kilograms [73 lbs.] of deuterium would produce a gigawatt of electricity for a year," while the amount of heavy hydrogen fuel in the reactor at any one time would be only a few grams, Kingham said.

That’s enough energy to power more than 700,000 average American homes, according to figures from the US Energy Information Administration.

Existing nuclear-fission plants generate electricity without producing greenhouse gas emissions, but they are fueled by radioactive heavy elements like uranium and plutonium, and create highly radioactive waste that must be carefully handled and stored. [5 Everyday Things That Are Radioactive]

In theory, fusion reactors could produce far less radioactive waste than fission reactors, while their relatively small fuel needs mean that nuclear meltdowns like the Chernobyl disaster or Fukushima accident would be impossible, according to the ITER project.

However, veteran fusion researcher Daniel Jassby, who was once a physicist at Princeton Plasma Physics Laboratory, has warned that ITER and other proposed fusion reactors will still create significant amounts of radioactive waste.

Road to nuclear fusion

The ST40 reactor and future reactors planned by Tokamak Energy use a compact spherical tokamak design, with an almost round vacuum chamber instead of the wider donut shape being used in the ITER reactor, Kingham said.

A critical advance was the use of high-temperature superconducting magnets to create the powerful magnetic fields needed to keep the superhot plasma from damaging the reactor walls, he said.

The 7-foot-tall (2.1 meters) electromagnets around the Tokamak Energy reactor were cooled by liquid helium to operate at minus 423.67 degrees F (minus 253.15 degrees C).

The use of advanced magnetic materials gave the Tokamak Energy reactor a significant advantage over the ITER reactor design, which would use power-hungry electromagnets cooled to a few degrees above absolute zero, Kingham said.

Other investment-funded fusion projects include reactors being developed General Fusion, based in British Colombia and TAE Technologies, based in California.

A Washington-based company, Agni Energy, has also reported early experimental success with yet a different approach to controlled nuclear fusion, called "beam-target fusion," Live Science reported earlier this week.

One of the most advanced privately funded fusion projects is the compact fusion reactor being developed by U.S.-based defense and aerospace giant Lockheed Martin at its Skunk Works engineering division in California.

The company says a 100-megawatt fusion reactor, capable of powering 100,000 homes, could be small enough to put on a truck trailer and be driven to wherever it is needed.

Original article on Live Science.

Editor's Note: This story was updated at 5:50 p.m. E.D.T.

The ongoing joke in the world of physics is that commercially viable fusion energy has been just on the horizon — 30 years away at most — for the past eight decades. Now, a new Washington-based startup, Agni Energy Inc., has a plan for a fusion reactor the company said could be closer than "just on the horizon."

Existing nuclear reactors use a process called fission, which releases energy by breaking atoms apart. But fission creates radioactive byproducts that must be collected and stored. Fusion, the opposite of fission, means joining things together — in this case, atoms. 

Fusion reactors slam atoms together and thereby release energy. But scientists haven't yet been able to create a useful fusion reactor — one that creates more energy than is put in. If scientists ever reach "the horizon" of fusion energy, these reactors would create a whole lot more energy than fission, without the harmful byproducts. After all, this process is what powers the sun.

Most fusion reactors use one of two methods: They either heat plasma (gas that contains ions) to extreme temperatures using laser or ion beams, or they squeeze the plasma with magnets to very high densities. [6 Cool Underground Science Labs] 

But both methods are riddled with problems. Beams require feeding a whole lot of energy into the system, said Demitri Hopkins, chief scientific officer of Agni Energy Inc. With magnets, if you energize plasma, you may not keep the atoms stable enough to contain all the energy.

Forgotten idea

The new approach would use both electrical and magnetic fields to create a hybrid fusion device. This so-called "beam-target fusion" doesn't try to fuse the atoms from one source; rather, it hits a beam of atoms against a solid target — and the atoms from the beam fuse with the atoms from the target. The ion beam in this approach consists of deuterium, or heavy hydrogen ions with one neutron, and the target consists of tritium ions, a heavy hydrogen with two neutrons. The approach uses hydrogen, which is the lightest element, because in fusion, the lightest elements produce the most energy, according to Hopkins.

Magnetic lenses stabilize and excite the atoms in the ion beam, and when the beam hits the target, the two types of hydrogen atoms merge and release high-energy neutrons that can then be used to heat water or power steam turbines. The fusion also creates nontoxic helium and a little bit of the original fuel source, tritium, which is slightly radioactive but can be reused as fuel, Hopkins said.

This beam-to-target fusion idea was first proposed in the 1930s and was "thought to be unviable," because it uses more energy than it generates, Hopkins said. "This was originally discarded as a path to fusion energy because it radiates out a lot of energy [that's not usable]. It scatters too much when it hits the target," Hopkins told Live Science. "Too much energy is lost that way, and that was sort of the end of the [idea]."

Less scattering

The team behind the new approach, however, said it can tweak atoms, in both the target and the beam, by playing with their spin polarization — or the orientation of their spin (a fundamental concept that refers to which way particles are rotating). By tilting the spins just so, the researchers can overcome the so-called Coulomb barrier, or the forces that repel atoms that get too close together, Hopkins said. That minimizes the extent to which atoms scatter, increasing the energy collected. [5 Everyday Things That Are Radioactive]

Hopkins and fellow high school students, Forrest Betton and Eric Thomas, engineered a small desktop model back in 2011 and found that spin polarization increased energy efficiency by two orders of magnitude.

However, not everyone is convinced this scheme will scale beyond that desktop model.

"While such systems can make a low level of fusion reactions … obtaining more energy out than what you're putting in is hopeless for pretty fundamental reasons," Donald Spong, a plasma physicist working on fusion reactions at Oak Ridge National Laboratory in Tennessee, told Live Science in an email.

That's because the scattering will likely be too high, said Spong, who is not involved in Agni's research.

Even if exotic states of spin polarization reduced scattering, "one would have to evaluate whether the energy required to produce the so-called exotic state would be overcome by the claimed increase in reaction efficiency," Spong said.

John Foster, a plasma physicist at the University of Michigan who is not part of the project, doesn't think it's impossible but just very tricky. "I can't say never, just that it's challenging," he said. "With solid targets, scattering is significant."

However, "it is established that spin polarizing does enhance the efficiency greatly," he said. "The trick is pulling it off in practice and en masse."

Hopkins said he is optimistic that Agni's design won't take as long as 30 years. "People have been saying they're close to fusion for the last 80 years," Hopkins said. "Eventually, someone's going to crack it."

It'll be exciting to see which ship, if any, will find the horizon first.

Editor's Note: This story was updated to correct the method of converting fusion energy into usable energy. Fusion can power a steam turbine, not a wind turbine.

Originally published on Live Science.

Russia's got a floating nuclear plant on a barge, and it's heading for the Bering Strait — just a short hop from Alaska.

The "Akademik Lomonosov," according to a statement from Russian nuclear energy company Rosatom, docked in the Russian port of Murmansk on Saturday (May 19). There it will receive its supply of nuclear fuel. Tugboats will eventually haul the nuclear plant to the town of Pevek in the Russian Far East — just 53 miles (86 kilometers), as Reuters noted, from the western edge of Alaska, across the Bering Strait.

The St. Petersburg-built power plant will replace a coal plant and an older, landlocked nuclear plant. It will serve a population of about 50,000 people, Rosatom said. [Top 10 Greatest Explosions Ever]

Rosatom pitches the Lomonosov as the first in a series of floating plants that will serve remote Russian communities and cut greenhouse gas emissions. There are objections from within the anti-nuclear wing of the environmental movement, which is represented by a subset of hardline environmental groups like Greenpeace and doesn't necessarily include all environmentalists.

In an April 26 blog titled "What Could Possibly Go Wrong with a Floating Nuclear Power Plant?" Greenpeace nuclear experts Jan Haverkamp and Rashid Alimov suggested these plants will primarily serve to power Russian fossil-fuel extraction efforts in the de-iced Arctic, and said, "If this development is not halted, the next nuclear catastrophe could well be a Chernobyl-on-ice or a Chernobyl-on-the-rocks."

Rosatom highlighted the potential for immediate emissions reductions and cited support from nuclear advocates. It said that no nuclear material would be left in the Arctic, and that in 40 or 50 years the plant will be towed away from the site for decommissioning.

Once the Lomonosov, with its two KLT-40 reactors — similar to reactors used to power Russian icebreaker ships — is hooked up to the power grid along the Bering Strait, it will be the only floating plant of its kind in the world.

In the late 1960s and early 1970s, the U.S. planned to park a floating reactor off the coast of New Jersey, as Matt Reimann reported for Timeline. It was planned as the first in a series of floating reactors built with the idea that construction costs would drop if all the necessary skilled labor were located in one place, before the plants were shipped elsewhere. However plans for the plant were scrapped as energy became less profitable during the 1973 oil embargo.

Originally published on Live Science.

Dangerous radioactive waste has been trapped inside solid glass in a first-of-its-kind demonstration, according to a statement from the Pacific Northwest National Laboratory (PNNL) in southeastern Washington.

In the demonstration, scientists at PNNL, a part of the U.S. Department of Energy (DOE), mixed low-activity radioactive waste — that is, waste with very small concentrations of radioactivity — with liquid glass, then let it harden into a durable, solid material. This so-called vitrification process immobilized the radioactive and chemical materials within the glass, the PNNL said.

"The radioactive elements are chemically bound as part of the glass material," Will Eaton, who led the test for PNNL, told Live Science. "And the glass material is a durable waste form that isolates the radioactivity from the environment for a very long time." [5 Everyday Things That Are Radioactive]

For the experiment, conducted in April, scientists from PNNL's Radiochemical Processing Laboratory took about 3 gallons (11 liters) of low-activity waste from a tank at the Hanford Site, a decommissioned nuclear production complex located next to PNNL in southeastern Washington. This small-scale demonstration is a key step forward in the goal of treating millions of gallons of hazardous waste that was generated from more than 40 years of plutonium production at Hanford, whose reactors produced plutonium for America's defense program, PNNL said.

"The experience from this test will help us as we prepare for full-scale operations," Albert Kruger, a glass scientist with the DOE's Office of River Protection (ORP), said in a statement. The ORP, which is responsible for the retrieval, treatment and disposal of the 56 million gallons (211 million liters) of chemical and radioactive waste stored in underground tanks at Hanford, did the test in partnership with PNNL and Washington River Protection Solutions, which manages Hanford tank operations.

To trap the hazardous liquid waste in glass, scientists mixed it with glass-forming materials, such as silica, and then slowly pumped the mixture into a melter that reached 2,100 degrees Fahrenheit (1,148 degrees Celsius). At the end of the test, the scientists had about 20 lbs. (9 kilograms) of glass.

"This successful test confirms the science and engineering approach," Eaton said in the statement. "Seeing actual Hanford low-activity waste being converted to glass is really exciting. It ties together 20 years of work from the design and construction of the Waste Treatment Plant to the research and testing that has supported that effort."

If the glass breaks, as it did in the test, "then you have multiple pieces of glass," Eaton told Live Science in an email. "The waste components are chemically bound and are a part of the glass material. The dissolution of the glass over time (which happens very slowly) depends of surface area, so some minor cracking has a very small effect on leaching into the environment."

Later this year, researchers plan a second vitrification test on about 2 gallons (7.5 liters) of waste from a different tank at Hanford. However, this waste will test different filtration- and ion-exchange methods, the PNNL said.

Once this test is completed, the low-activity waste glass containers will be stored in the Integrated Disposal Facility at the Hanford Site.

Original article on Live Science.

There's a whiff of something radioactive in the air.

A research plane flying over the Aleutian Islands on Aug. 3, 2016 detected a single speck of enriched uranium floating about 4.3 miles (7 kilometers) above Alaska's far-western island chain, according to a new research paper that will be published in April in The Journal of Environmental Radioactivity.

The uranium sample was tiny and harmless, a small chunk of a mote of dust just 580 nanometers wide (about half the size of a red blood cell). And it was completely alone; no other radioactive material turned up in that stretch of sky. But, the researchers wrote, it was "definitely not from a natural source."

And the scientists can't explain how it got there.

The plane's onboard mass spectrometer, brought along to analyze standard-issue pollution, detected just a single uranium particle, mixed with traces of chemicals from burning oil, the authors reported. And on its own, that find wouldn't be too remarkable — uranium is the heaviest element commonly found on Earth, after all.

"Particulate matter containing uranium can originate from sources such as combustion of coals with trace uranium, windblown crustal material, and mining and processing of ores, whether it be for the uranium itself or other minerals such as rare earths [a group of chemically similar elements that aren't actually that rare, but are difficult to mine] and phosphate," the researchers wrote. [The 10 Greatest Explosions Ever]

What makes this particle unusual is that it was rich in an isotope called uranium-235, or U-235, which made up about 2.6 percent to 3.6 percent of its mass, according to the paper. Naturally occurring uranium typically contains just 0.7 percent U-235, with the rest given over to the much more common uranium-238.

That's a big deal.

As Richard Rhodes described in his book "The Making of the Atomic Bomb," published by Simon and Schuster in 1987, uranium-235, an atom made up of 92 protons and 143 neutrons, is special because it can easily sustain a nuclear chain reaction. That's the process of one atom splitting, flinging neutrons out into space, those neutrons smashing into the atom's neighbors and causing them to split, and so on. Uranium-238, with its extra three neutrons, just doesn't give itself over to sustained chain reactions of the kind needed for nuclear power, or nuclear weapons.

Rhodes wrote that refining uranium-235 out of large natural samples of mostly uranium-238 was one of the most important challenges during the race to build the first atomic bomb in the 20th century. And that process remains a challenge today.

The Aleutian Islands sample, with its relatively high percentage of uranium-235 content, is already refined enough to serve in a nuclear reactor, the researchers wrote. (A bomb requires something closer to 90 percent uranium-235 content.)

Finding a sample of refined uranium in the open air is bizarre and remarkable, but it's not dangerous on its own, experts said.

"It's not a significant amount of radioactive debris by itself," Dan Murphy, a National Oceanic and Atmospheric Administration scientist and one of the paper's authors, told Gizmodo, which originally reported on the paper. “But it’s  the implication [of this finding is] that there's some very small source of uranium that we don’t don't understand."

For one thing, as the paper stated, the particle is much smaller than the particles of uranium dust that emerge from typical nuclear facilities. It's possible, the authors suggested, that a forest fire or something similar kicked up old particles from an event like the Chernobyl meltdown — but there haven't been any recent incidents that would be obvious culprits for that kind of thing.

Beyond the uranium particle itself, the air sample the plane collected wasn't unusual, with its only notable feature being some diluted trace burnt-oil pollution, the researchers wrote. Based on prevailing air currents, it's likely the particle came to Alaska from somewhere within a broad swath of Asia, including China, Japan and the Korean Peninsula.

But, the researchers cautioned, the science of figuring out just how individual particles might have arrived in a given patch of air is too inexact to determine the mysterious uranium's origin with any certainty.

Originally published on Live Science.

A team of researchers has a plan to achieve nuclear fusion that actually produces energy, and their proposal looks very different from the fusion projects the world has already seen.

If the team is right, its strange, spherical hydrogen-boron reactor could be built in useful form before any ongoing conventional fusion projects reach completion.

The secret behind the new reactor design? It relies on completely different elements than older projects do, and it uses different methods to heat up its core. [The 8 Hottest Places on Earth]

Elusive power source

There's a lot of energy locked away inside atoms.

Much of that energy makes up the binding forces that hold atoms together. Physicists have known for most of the last century that they could tap into that energy by splitting those bonds. That reaction, atomic fission, has been deployed to destroy the cities of Hiroshima and Nagasaki, as well as to power every nuclear reactor that exists in the world today.

But it turns out that the reverse reaction, atomic fusion, is even more powerful (it is the reaction that powers the sun, after all). While fission reactors usually split very large atoms, like uranium or plutonium, fusion reactors aim to smash very light atoms together. Typically, those nuclei are heavy isotopes of hydrogen, such as deuterium and tritium, meaning they have extra neutrons. They fuse to form helium, releasing massive amounts of energy in the process.

All the largest known weapons in the human arsenal are fusion bombs, also known as hydrogen bombs, that smash deuterium and tritium together to release massive explosions and flashes of radiation. However, no useful fusion reactors exist. Every model that has been built uses up more energy sustaining the hot plasma necessary for the fusion reaction than the model produces in electricity.

Still, many researchers argue that once net-positive nuclear fusion is achieved, it will offer a source of functionally unlimited energy, with transformative effects for the global energy economy.

Game changer?

The new hydrogen-boron reactor is potentially a game changer for a simple reason: efficiency.

A deuterium-tritium reactor faces two challenges on the way to producing electricity: A lot of the energy gets wasted as atoms shed neutrons during the reaction, and the remaining energy can't be converted directly to electricity. Instead, it's used to heat up water, which turns a turbine, which produces electricity. So, most of the energy put into the reaction can't be efficiently translated into usable electricity.

But in the new study, which was published Dec. 12 in the journal Laser and Particle Beams, Heinrich Hora, a physicist at the University of New South Wales in Australia, and colleagues argued that they can sidestep these challenges by using a completely different fusion reaction.

If you fuse hydrogen-0 (just a single proton with no neutrons or electrons) and boron-11 (a version of boron with six neutrons) to make three helium-4 nuclei (each containing two protons and two neutrons), the researchers wrote, no neutrons get wasted. The atoms combine cleanly without losing any of their core particles. And in the reactor Hora proposes, the energy of the plasma could be converted directly into electricity without wastefully heating up water along the way, because the fusion's energy is released as a stream of electrically charged particles, which can relatively easily be turned into current in a wire.

Unlike deuterium-tritium reactors, which hold superheated plasma in place using magnets inside donut-shaped chambers, Hora's spherical hydrogen-boron reactor uses lasers to trigger and sustain the reaction. Those lasers are critical, Hora said: They waste much less energy heating up the atoms in the plasma and use less energy keeping the atoms in place. [5 Everyday Things that Are Radioactive]

The lasers allow the hydrogen-boron plasma to reach temperatures of 5 billion degrees Fahrenheit (3 billion degrees Celsius) and densities 100,000 times greater than those of the plasmas inside a deuterium-tritium reactor. Those are much more intense reaction conditions than other projects aim for, but Hora and his team wrote that it should be easier to achieve these conditions given current technology, at least according to the researchers' early experiments and simulations.

The spherical shape, meanwhile, would allow the superhot plasma to retain a more efficient cylindrical shape at its core, which makes it an ideal target for the cylindrical laser. A spherical shape also efficiently retains the energy produced by the fusion reaction, the researchers said.

No energy-positive fusion reactor of any kind yet exists. But this is the type of early work that might one day make it happen.

Originally published on Live Science.

The world's first nuclear fusion plant has now reached 50 percent completion, the project's director-general announced Wednesday (Dec. 6).

When it is operational, the experimental fusion plant, called the International Thermonuclear Experimental Reactor (ITER), will circulate plasma in its core that is 10 times hotter than the sun, surrounded by magnets as cold as interstellar space.

Its goal? To fuse hydrogen atoms and generate 10 times more power than goes into it by the 2030s.

Ultimately,  ITER is meant to prove that fusion power can be generated on a commercial scale and is sustainable, abundant, safe and clean.

"With ITER and fusion energy, we have a chance to leave a powerful and positive legacy for future generations, instead of the current energy outlook," Bernard Bigot, director-general of ITER, told Live Science. [Top 10 Craziest Environmental Ideas]

Conceptual design

Nuclear fusion, the same reaction that occurs in the heart of the sun, merges atomic nuclei to form heavier nuclei. Nuclear fusion has been a long-sought goal because fusion reactions generate far more energy than burning fossil fuels do. For example, a pineapple-size amount of hydrogen atoms offers as much energy as 10,000 tons of coal, according to a statement from the ITER project.

Unlike today's nuclear fission plants —which splits large atoms into smaller ones — a fusion plant would not generate high levels of radioactive waste. And in contrast to fossil fuel plants, fusion energy does not generate the greenhouse gas carbon dioxide, or other pollutants. [The Reality of Climate Change: 10 Myths Busted]

ITER aims to use superconducting magnets to fuse hydrogen atoms and produce massive amounts of heat. Future nuclear fusion plants can then use this heat to drive turbines and generate electricity.

The experimental reactor will not use conventional hydrogen atoms, whose nuclei each consist of one proton. Instead, it will fuse deuterium, whose nuclei each possess one proton and one neutron, with tritium, whose nuclei each have one proton and two neutrons. Deuterium is easily extracted from seawater, while tritium will be generated inside the fusion reactor. The supply of these fuels is abundant, enough for millions of years at current global energy usage, according to ITER.

And unlike fission reactors, fusion is very safe: If fusion reactions get disrupted within a fusion plant, fusion reactors will simply shut down safely and without need of external assistance, the ITER project noted. In theory, fusion plants also use only a few grams of fuel at a time, so there is no possibility of a meltdown accident.

Unprecedented challenge, big delays

Although fusion energy has many potential benefits, it has proved extraordinarily difficult to achieve on Earth. Atomic nuclei require huge amounts of heat and pressure before they fuse together.

To overcome that huge challenge, ITER aims to heat hydrogen to about 270 million degrees Fahrenheit (150 million degrees Celsius), 10 times hotter than the core of the sun. This superheated hydrogen plasma will get confined and circulated inside a donut-shaped reactor called a tokamak, which is surrounded by giant superconducting magnets that control the electrically charged plasma. In order for the superconducting magnets to function, they must be cooled to minus 452 degrees F (minus 269 degrees C), as cold as interstellar space.

Industrial facilities around the world are manufacturing 10 million components for the reactor. The reactor is often billed as the most complicated piece of engineering ever built. For example, magnets more than 55 feet high (17 meters) must get fitted together with a margin of error of less than 0.04 inches (1 millimeter).

"So many of the technologies involved are really at the cutting edge," Bigot said. "We are pushing the boundaries in many fields – cryogenics, electromagnetics, even the use of giant tooling devices. Cooling 10,000 tons of superconducting magnet material to minus 269 degrees, for example, is unprecedented in scale."

A scientific partnership of 35 countries is building ITER in southern France. All members share in ITER's technology, and they receive equal access to the intellectual property and innovations that come from the effort.

The idea of a scientific partnership to build a fusion plant was first conceived at the 1985 Geneva Summit between Ronald Reagan and Mikhail Gorbachev. The ITER project began in earnest in 2007, and was originally due to be completed in 10 years for $5.6 billion. However, the project is more than a decade behind schedule, and its estimated cost has ballooned to about $22 billion.

"When the original ITER project was established and agreed upon by members, their understanding was that the design was nearly complete and ready for construction, and that wasn't even close to being accurate," said William Madia, vice president at Stanford University, who led an independent review of ITER in 2013.

Bigot took over the troubled project in 2015. "It's making better progress for sure," Madia, a former director of the Oak Ridge and Pacific Northwest national laboratories, told Live Science. "I'm a big supporter and fan of Bernard Bigot — I think he's done a good job. In two or maybe three more years, if he continues to make progress, we may see real changes in attitude regarding ITER."

Circulating plasma

ITER is now halfway toward its initial goal of circulating plasma.

"It is definitely a big milestone for us," Bigot said.

Bigot said ITER remains on schedule for first plasma in 2025. "When we set that schedule in November 2015, we had many skeptics," Bigot said. "This schedule has no 'float' or contingency, meaning it is the best technically achievable schedule. This means we are constantly working to anticipate and mitigate risks that could cause additional delay or cost. It is not easy. But in the past two years, we have met every milestone, and we remain on track. We have also learned a lot about working as a team. This gives us confidence as we face the remaining 50 percent."

The final goal, of course, is not just circulating plasma, but fusing deuterium and tritium to create a "burning" plasma that generates significantly more energy than goes into it. The ITER tokamak should generate 500 megawatts of power, while commercial fusion plants would house larger reactors to generate 10 to 15 times more power. A 2,000-megawatt fusion plant would supply 2 million homes with electricity, the according to a statement.. [Quiz: The Science of Electricity]

"Optimistically, they'll get a burning plasma in the 2030s," Madia said.

If the project proves successful, ITER scientists predict that fusion plants may start coming online as soon as 2040, with a 2 gigawatt fusion plant built to last 60 years or more, according to the statement. The capital costs of building a nuclear fusion plant should be similar to those of current nuclear fission plants ― about $5 billion per gigawatt. At the same time, nuclear fusion plants just use deuterium and tritium, and so avoid "the costs of mining and enriching uranium, or the costs of caring for and disposing of radioactive waste," Bigot said.

Although building a nuclear fusion plant costs more than building a fossil fuel plant, "fossil fuel costs are very high, and fuel costs for fusion are negligible, so over the life of the plant, we expect it will average out," Bigot said.

At the same time, fossil fuels have costs other than financial ones. "The huge cost of fossil fuels is in the environmental impacts, whether due to mining, pollution or release of greenhouse gases," Bigot said. "Fusion is carbon-free."

Original article on Live Science.

This article was originally published at The Conversation. The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.

Over Christmas vacation in 1938, physicists Lise Meitner and Otto Frisch received puzzling scientific news in a private letter from nuclear chemist Otto Hahn. When bombarding uranium with neutrons, Hahn had made some surprising observations that went against everything known at the time about the dense cores of atoms – their nuclei.

Meitner and Frisch were able to provide an explanation for what he saw that would revolutionize the field of nuclear physics: A uranium nucleus could split in half – or fission, as they called it – producing two new nuclei, called fission fragments. More importantly, this fission process releases huge amounts of energy. This finding at the dawn of World War II was the start of a scientific and military race to understand and use this new atomic source of power.

The release of these findings to the academic community immediately inspired many nuclear scientists to investigate the nuclear fission process further. Physicist Leo Szilard made an important realization: if fission emits neutrons, and neutrons can induce fission, then neutrons from the fission of one nucleus could cause the fission of another nucleus. It could all cascade in a self-sustained "chain" process.

Thus began the quest to experimentally prove that a nuclear chain reaction was possible – and 75 years ago, researchers at the University of Chicago succeeded, opening the door to what would become the nuclear era.

Harnessing fission

As part of the Manhattan Project effort to build an atomic bomb during World War II, Szilard worked together with physicist Enrico Fermi and other colleagues at the University of Chicago to create the world's first experimental nuclear reactor.

For a sustained, controlled chain reaction, each fission must induce just one additional fission. Any more, and there'd be an explosion. Any fewer and the reaction would peter out.

In earlier studies, Fermi had found that uranium nuclei would absorb neutrons more easily if the neutrons were moving relatively slowly. But neutrons emitted from the fission of uranium are fast. So for the Chicago experiment, the physicists used graphite to slow down the emitted neutrons, via multiple scattering processes. The idea was to increase the neutrons' chances of being absorbed by another uranium nucleus.

To make sure they could safely control the chain reaction, the team rigged together what they called "control rods." These were simply sheets of the element cadmium, an excellent neutron absorber. The physicists interspersed control rods through the uranium-graphite pile. At every step of the process Fermi calculated the expected neutron emission, and slowly removed a control rod to confirm his expectations. As a safety mechanism, the cadmium control rods could quickly be inserted if something started going wrong, to shut down the chain reaction.

They called this 20x6x25-foot setup Chicago Pile Number One, or CP-1 for short – and it was here they obtained world's the first controlled nuclear chain reaction on December 2, 1942. A single random neutron was enough to start the chain reaction process once the physicists assembled CP-1. The first neutron would induce fission on a uranium nucleus, emitting a set of new neutrons. These secondary neutrons hit carbon nuclei in the graphite and slowed down. Then they'd run into other uranium nuclei and induce a second round of fission reactions, emit even more neutrons, and on and on. The cadmium control rods made sure the process wouldn't continue indefinitely, because Fermi and his team could choose exactly how and where to insert them to control the chain reaction.

Controlling the chain reaction was extremely important: If the balance between produced and absorbed neutrons was not exactly right, then the chain reactions either would not proceed at all, or in the other much more dangerous extreme, the chain reactions would multiply rapidly with the release of enormous amounts of energy.

Sometimes, a few seconds after the fission occurs in a nuclear chain reaction, additional neutrons are released. Fission fragments are typically radioactive, and can emit different types of radiation, among them neutrons. Right away, Enrico Fermi, Leo Szilard, Eugene Wigner and others recognized the importance of these so-called "delayed neutrons" in controlling the chain reaction.

If they weren't taken into account, these additional neutrons would induce more fission reactions than anticipated. As a result, the nuclear chain reaction in their Chicago experiment could have spiraled out of control, with potentially devastating results. More importantly, however, this time delay between the fission and the release of more neutrons allows some time for human beings to react and make adjustments, controlling the power of the chain reaction so it doesn't proceed too fast.

The events of December 2, 1942 marked a huge milestone. Figuring out how to create and control the nuclear chain reaction was the foundation for the 448 nuclear reactors producing energy worldwide today. At present, 30 countries include nuclear reactors in their power portfolio. Within these countries, nuclear energy contributes on average 24 percent of their total electrical power, ranging as high as 72 percent in France.

CP-1's success was also essential for the continuation of the Manhattan Project and the creation of the two atomic bombs used during World War II.

Physicists' remaining questions

The quest to understand delayed neutron emission and nuclear fission continues in modern nuclear physics laboratories. The race today is not for building atomic bombs or even nuclear reactors; it's for understanding of basic properties of nuclei through close collaboration between experiment and theory.

Researchers have observed fission experimentally only for a small number of isotopes – the various versions of an element based on how many neutrons each has – and the details of this complex process are not yet well-understood. State-of-the-art theoretical models try to explain the observed fission properties, like how much energy is released, the number of neutrons emitted and the masses of the fission fragments.

Delayed neutron emission happens only for nuclei that are not naturally occurring, and these nuclei live for only a short amount of time. While experiments have revealed some of the nuclei that emit delayed neutrons, we are not yet able to reliably predict which isotopes should have this property. We also don't know exact probabilities for delayed neutron emission or the amount of energy released – properties that are very important for understanding the details of energy production in nuclear reactors.

In addition, researchers are trying to predict new nuclei where nuclear fission might be possible. They're building new experiments and powerful new facilities which will provide access to nuclei that have never before been studied, in an attempt to measure all these properties directly. Together, the new experimental and theoretical studies will give us a much better understanding of nuclear fission, which can help improve the performance and safety of nuclear reactors.

Both fission and delayed neutron emission are processes that also happen within stars. The creation of heavy elements, like silver and gold, in particular can depend on the fission and delayed neutron emission properties of exotic nuclei. Fission breaks the heaviest elements and replaces them with lighter ones (fission fragments), completely changing the element composition of a star. Delayed neutron emission adds more neutrons to the stellar environment, that can then induce new nuclear reactions. For example, nuclear properties played a vital role in the neutron-star merger event that was recently discovered by gravitational-wave and electromagnetic observatories around the world.

The science has come a long way since Szilard's vision and Fermi's proof of a controlled nuclear chain reaction. At the same time, new questions have emerged, and there's still a lot to learn about the basic nuclear properties that drive the chain reaction and its impact on energy production here on Earth and elsewhere in our universe.

Artemis Spyrou, Associate Professor of Nuclear Astrophysics, Michigan State University and Wolfgang Mittig, Professor of Physics, Michigan State University

This article was originally published on The Conversation. Read the original article.

A mysterious cloud of radioactive material that hovered over Europe last month came from Russia, Russian weather monitoring data released today (Nov. 21) suggests.

The spike in radioactivity was caused by a substance called ruthenium-106. But what, exactly, is ruthenium-106, does it pose risks to human health and how did it get into the air?

History of radioactive cloud

Member countries of the International Atomic Energy Agency, an international organization that promotes peaceful use of nuclear energy, detected the radioactive isotope ruthenium-106 hovering above 14 European countries in early October, according to a statement from France's Nuclear Safety Authority. Based on radioactivity levels across the continent, experts suspected the origin was somewhere in Russia Russia denied a nuclear accident occurred. [Images: Chernobyl, Frozen in Time]

Today, however, the Russian Meteorological Service said it detected "extremely high contamination" with ruthenium-106 above the southern Ural Mountains in September. In Argayash, levels of ruthenium-106 were 986 times normal levels in late September, according to Rosgidromet, the weather monitoring service.

Nuclear-fuel byproduct

Ruthenium-106 is a radioactive isotope of ruthenium, meaning it has a different number of neutrons than the naturally occurring form of the element. The hard, white metal is chemically similar to platinum, and can be produced by dissolving platinum in nitric acid and hydrochloric acid. Ruthenium is incredibly rare and was discovered in 1844 in the Ural Mountains, Live Science previously reported.

Ruthenium-106, however, is not found naturally, according to France's Nuclear Safety Authority. Instead, it is typically produced by the nuclear fission, or splitting, of uranium-235 atoms in nuclear reactors. Ruthenium-106 is also often produced during the reprocessing of nuclear fuel. Nuclear reprocessing involves separating the radioactive plutonium and uranium from spent nuclear fuel from nuclear power reactors, according to the Union of Concerned Scientists.

Ruthenium-106 is also used in head and eye radiation cancer treatments, according to the Journal of Radioanalytical and Nuclear Chemistry. It is also found in trace levels in satellites, as part of their thermoelectric generators, according to the Institut de Radioprotection et de Sûreté Nucléaire (IRSN), a French institute focusing on radiological and nuclear risks.

High doses of ruthenium are toxic and carcinogenic when ingested. The material is strongly retained in the bones. However, the levels detected over the past two months seem to be safe, according to the IRSN.

"The concentration levels of ruthenium-106 in the air that have been recorded in Europe and especially in France are of no consequence for human health and for the environment," the IRSN said in a statement.

While food might be contaminated with ruthenium for several miles around the epicenter of the nuclear release, the chance that contaminated food will be exported is also low, the IRSN said.

Likely source

The radioactive cloud didn't contain any other nuclear waste products, ruling out the possibility that the spike came directly from a nuclear reactor, according to the French Nuclear Safety Authority.

Given that ruthenium-106 has no natural source and no one reported fallen satellites in the region, the likeliest source for the toxic cloud is an uncontrolled release of nuclear material, the Nuclear Safety Authority said.

Just 19 miles (30 kilometers) from the Argayash weather station is the Mayak Production Association in Chelyabinsk Oblast, which reprocesses nuclear fuel for radioactive material used in research and industry, according to the Straits Times, a Singapore-based media outlet.

However, Rosatom, the state nuclear agency that runs the Mayak plant, denied any involvement.

"The contamination of the atmosphere with ruthenium-106 isotope registered by Rosgidromet is not linkedto the activity of Mayak," Rosatom officials said in a statement. "The measurements which Rosgidromet has released suggest that the dose people might have received is 20,000 times less than the allowed annual dose and presents no threat at all to health."

The Mayak facility has experienced past nuclear accidents. In 1957, for instance, the world's third biggest nuclear accident, called the Kyshtym disaster, exposed hundreds of thousands of people nearby to radioactive contamination. The two biggest nuclear disasters occurred at the Chernobyl Power Plant in Ukraine and the Fukushima Daiichi Nuclear Power Plant in Japan, respectively.

Originally published on Live Science.

Workers at a nuclear-waste site in Washington state were recently told to hunker down in place after a tunnel in the nuclear finishing plant collapsed, news sources reported yesterday (May 9).

Workers at the Hanford nuclear site were told to either evacuate or shelter in place, and to avoid eating or drinking anything after the tunnel collapsed, according to the Yakima Herald. The U.S. Department of Energy activated an Emergency Operations Center for dealing with the disaster.

The tunnel was part of the plutonium and uranium extraction facility (PUREX) said to be holding a lot of radioactive waste, including railway cars used to carry spent nuclear fuel rods, news agency AFP reported. At least some of the radioactive waste at the Hanford facility contains radioactive plutonium and uranium, according to the DOE, although at least some of it is also radioactive "sludge" composed of a mixture of radioactive substances. Right now, authorities have not revealed whether radioactive substances have been released or whether people have been exposed any of these contaminants. [Images: Chernobyl, Frozen in Time]

But if people were indeed exposed to the radioactive waste containing plutonium and uranium, what health risks would they face? And how can people minimize their risk of exposure?

Radioactive plutonium and uranium

All radioactive material, as it decays, can cause harm. As unstable radioactive isotopes, or versions of an element with different molecular weights, decay into slightly more stable versions, they release energy. This extra energy can either directly kill cells or damage a cell's DNA, fueling mutations that may eventually lead to cancer.

Plutonium, one of the radioactive substances that may be present at the Hanford site, has a half-life of 24,000 years, meaning that's how long it takes for half of the material to decay into more stable substances. As such, it sticks around in the environment, and in the body, for a long time.

Plutonium exposure can be very deadly for living creatures. A 2011 study in the journal Nature Chemical Biology found that rat adrenal-gland cells ferried plutonium into the cells; the plutonium entered the body's cells largely by taking the natural place of iron on receptors. That study found that plutonium also can linger preferentially in the liver and blood cells, leaching alpha radiation (two protons and neutrons bound together). When inhaled, plutonium can also cause lung cancer.

However, because the human body still slightly prefers iron to plutonium for its biological processes, that preference could potentially provide avenues for treating plutonium exposure, by flooding such receptors and preventing plutonium from being taken in by the cells, the study authors noted.

In addition, a 2005 study in the journal Current Medicinal Chemistry found that there are some short-term treatments for plutonium exposure. Studies in the 1960s and 1970s identified agents, such as Diethylenetriaminepentaacetic, which can help the body remove plutonium faster. Other drugs, such as ones used to treat iron-processing disorders such as beta-thalassemia, or bone-strengthening drugs that treat osteoporosis, may also be useful for plutonium exposure, the study found.

Uranium, another radioactive element that may be present at dangerous concentrations in the PUREX tunnel, also can have harmful effects on human health. Uranium isotopes have half-lives ranging from 4.5 billion years to 25,000 years.

The biggest health risk people face after being exposed to uranium is kidney damage, according to the Centers for Disease Control and Prevention. People exposed to uranium may also experience lung problems, such as scar tissue (fibrosis)  or emphysema (large air sacs in the lungs). At high doses, uranium can directly cause kidneys and lungs to fail, according to the CDC. However, studies have found that people who drink well water containing low doses of uranium do not show any marked changes in kidney function.

Like plutonium, uranium emits alpha radiation. Uranium may also decay into radon, which has been tied to an increased cancer risk in several studies, particularly in miners who are exposed to higher levels of the toxin.

It's not clear whether there are other radioactive substances in the Hanford site area, but radioactive forms of iodine and cesium can also cause problems such as thyroid cancer, Live Science previously reported.

Radiation sickness

Overall, radiation from any source increases the risk of cancer, and the cancer risk increases with higher exposures. Extremely high doses of radioactive waste can induce a condition known as radiation sickness, in which the gastrointestinal tract literally bleeds and sloughs off its lining. During the Chernobyl nuclear disaster, 28 emergency workers died directly from radiation poisoning in the three months after the disaster, and rates of cancer in nearby populations increased four to 10 years after the disaster, Live Science reported.

However, exposures in more recent nuclear disasters, such as the nuclear meltdown at the Fukushima Daiichi plant, have not typically been high enough to show highly elevated rates of cancer. For instance, a Japanese worker who was exposed to 10 rem (100 millisievert, or mSv), a measurement of radiation, may face a lifetime cancer risk that is elevated by half a percent, Kathryn Higley, director of the Oregon State University Department of Nuclear Engineering and Radiation Health Physics, previously told Live Science. That radiation dose amounts to the levels received with about five CT scans. Most people in the United States receive 0.3 rem (3 mSv) of radiation each year from natural sources, such as the sun, Live Science previously reported.

In addition, studies have found lower rates of cancer in nuclear plant workers than in the general population, likely because these workers tend to be healthier than the people in the nearby population, according to a 2004 study in the French journal Revue Epidemiological Sante Publique. Therefore, untangling a slightly elevated risk of cancer due to radiation exposure from a slightly lower risk due to healthier habits could be tricky, the study noted.

Originally published on Live Science.

Six years have passed since the Fukushima nuclear disaster on March 11, 2011, but Japan is still dealing with its impacts. Decommissioning the damaged Fukushima Daiichi nuclear plant poses unprecedented technical challenges. More than 100,000 people were evacuated but only about 13 percent have returned home, although the government has announced that it is safe to return to some evacuation zones.

In late 2016 the government estimated total costs from the nuclear accident at about 22 trillion yen, or about US$188 billion – approximately twice as high as its previous estimate. The government is developing a plan under which consumers and citizens will bear some of those costs through higher electric rates, taxes or both.

The Japanese public has lost faith in nuclear safety regulation, and a majority favors phasing out nuclear power. However, Japan's current energy policy assumes nuclear power will play a role. To move forward, Japan needs to find a new way of making decisions about its energy future.

Uncertainty over nuclear power

When the earthquake and tsunami struck in 2011, Japan had 54 operating nuclear reactors which produced about one-third of its electricity supply. After the meltdowns at Fukushima, Japanese utilities shut down their 50 intact reactors one by one. In 2012 then-Prime Minister Yoshihiko Noda's government announced that it would try to phase out all nuclear power by 2040, after existing plants reached the end of their 40-year licensed operating lives.

Now, however, Prime Minister Shinzo Abe, who took office at the end of 2012, says that Japan "cannot do without" nuclear power. Three reactors have started back up under new standards issued by Japan's Nuclear Regulation Authority, which was created in 2012 to regulate nuclear safety. One was shut down again due to legal challenges by citizens groups. Another 21 restart applications are under review.

In April 2014 the government released its first post-Fukushima strategic energy plan, which called for keeping some nuclear plants as baseload power sources – stations that run consistently around the clock. The plan did not rule out building new nuclear plants. The Ministry of Economy, Trade and Industry (METI), which is responsible for national energy policy, published a long-term plan in 2015 which suggested that nuclear power should produce 20 to 22 percent of Japan's electricity by 2030.

Meanwhile, thanks mainly to strong energy conservation efforts and increased energy efficiency, total electricity demand has been falling since 2011. There has been no power shortage even without nuclear power plants. The price of electricity rose by more than 20 percent in 2012 and 2013, but then stabilized and even declined slightly as consumers reduced fossil fuel use.

Japan's Basic Energy Law requires the government to release a strategic energy plan every three years, so debate over the new plan is expected to start sometime this year.

Public mistrust

The most serious challenge that policymakers and the nuclear industry face in Japan is a loss of public trust, which remains low six years after the meltdowns. In a 2015 poll by the pro-nuclear Japan Atomic Energy Relations Organization, 47.9 percent of respondents said that nuclear energy should be abolished gradually and 14.8 percent said that it should be abolished immediately. Only 10.1 percent said that the use of nuclear energy should be maintained, and a mere 1.7 percent said that it should be increased.

Another survey by the newspaper Asahi Shimbun in 2016 was even more negative. Fifty-seven percent of the public opposed restarting existing nuclear power plants even if they satisfied new regulatory standards, and 73 percent supported a phaseout of nuclear power, with 14 percent advocating an immediate shutdown of all nuclear plants.

Who should pay to clean up Fukushima?

METI's 22 trillion yen estimate for total damages from the Fukushima meltdowns is equivalent to about one-fifth of Japan's annual general accounting budget. About 40 percent of this sum will cover decommissioning the crippled nuclear reactors. Compensation expenses account for another 40 percent, and the remainder will pay for decontaminating affected areas for residents.

Under a special financing scheme enacted after the Fukushima disaster, Tepco, the utility responsible for the accident, is expected to pay cleanup costs, aided by favorable government-backed financing. However, with cost estimates rising, the government has proposed to have Tepco bear roughly 70 percent of the cost, with other electricity companies contributing about 20 percent and the government – that is, taxpayers – paying about 10 percent.

This decision has generated criticism both from experts and consumers. In a December 2016 poll by the business newspaper Nihon Keizai Shimbun, one-third of respondents (the largest group) said that Tepco should bear all costs and no additional charges should be added to electricity rates. Without greater transparency and accountability, the government will have trouble convincing the public to share in cleanup costs.

Other nuclear burdens: Spent fuel and separated plutonium

Japanese nuclear operators and governments also must find safe and secure ways to manage growing stockpiles of irradiated nuclear fuel and weapon-usable separated plutonium.

At the end of 2016 Japan had 14,000 tons of spent nuclear fuel stored at nuclear power plants, filling about 70 percent of its onsite storage capacity. Government policy calls for reprocessing spent fuel to recover its plutonium and uranium content. But the fuel storage pool at Rokkasho, Japan's only commercial reprocessing plant, is nearly full, and a planned interim storage facility at Mutsu has not started up yet.

The best option would be to move spent fuel to dry cask storage, which withstood the earthquake and tsunami at the Fukushima Daiichi nuclear plant. Dry cask storage is widely used in many countries, but Japan currently has it at only a few nuclear sites. In my view, increasing this capacity and finding a candidate site for final disposal of spent fuel are urgent priorities.

Japan also has nearly 48 tons of separated plutonium, of which 10.8 tons are stored in Japan and 37.1 tons are in France and the United Kingdom. Just one ton of separated plutonium is enough material to make more than 120 crude nuclear weapons.

Many countries have expressed concerns about Japan's plans to store plutonium and use it in nuclear fuel. Some, such as China, worry that Japan could use the material to quickly produce nuclear weapons.

Now, when Japan has only two reactors operating and its future nuclear capacity is uncertain, there is less rationale than ever to continue separating plutonium. Maintaining this policy could increase security concerns and regional tensions, and might spur a "plutonium race" in the region.

As a close observer of Japanese nuclear policy decisions from both inside and outside of the government, I know that change in this sector does not happen quickly. But in my view, the Abe government should consider fundamental shifts in nuclear energy policy to recover public trust. Staying on the current path may undermine Japan's economic and political security. The top priority should be to initiate a national debate and a comprehensive assessment of Japan's nuclear policy.

Tatsujiro Suzuki, Professor and Director, Research Center for Nuclear Weapons Abolition, Nagasaki University.

Editor's note: This article has been corrected to reflect the fact that one ton of separated plutonium is enough to produce more than 120 crude nuclear weapons.

This article was originally published on The Conversation. Read the original article.

The searing heat deep inside Earth is what keeps the planet churning — creeping tectonic plates, erupting volcanoes and a working magnetic field — but how much of this sizzling energy does the planet have in its tank?

Scientists have long wondered how much energy remains in the planet today, 4.6 billion years after the rocky world formed. Now, a team of researchers plans to have an answer to the gargantuan question by 2025. By determining how much energy Earth has left, scientists will better understand the building blocks of the planet and its energy-spending processes.

When all of the energy is used up, that means Earth will "die" in the sense that the moon is "dead" because it does not have the energy for mantle convection, volcanism, and other planetary processes.

These planetary processes run on two types of energy: primordial energy, which is the heat left over from Earth's violent formation, and nuclear energy, or the heat produced during natural radioactive decay. [Photos: The Strangest Places on Earth]

Earth energy

Past calculations of Earth's inner energy have varied.

"We're in a field of guesses," one of the study's authors, William McDonough, a professor of geology at the University of Maryland, said in a statement. "At this point in my career, I don't care if I'm right or wrong. I just want to know the answer."

Here's how McDonough and his team will tackle the problem: As has been done for past estimates, the scientists will measure Earth's geoneutrinos, or the antimatter partners of neutrinos — ghostly subatomic particles that pass right through Earth relatively unscathed. The antineutrino particles are byproducts of nuclear reactions, resulting from radioactive decay of elements such as thorium and uranium.

"The particles will tell us about how many atoms of uranium and thorium are inside the Earth. Therefore, that will tell us about how much radioactivity potential there exists," McDonough told Live Science. "We know the Earth radiates 46 terawatts of heat, or power, and so what we determine for nuclear energy, the difference would amount to the primordial energy left."

Previous research has demonstrated that these heat-producing radioactive elements alone are insufficient to account for the 46 TW the Earth radiates; therefore, residual primordial energy must be present. Determining the amount of energy left from both sources will also offer insight into how the Earth is burning its fuel, its consumption rate in the past and its future fuel budget.

"There are two gas gauges — one primordial energy and one nuclear energy," McDonough explained. "If we have lots of nuclear energy, we used up our primordial energy. If we have a little bit of nuclear energy, then we have not used up our primordial energy."

McDonough said the amount of fuel left could be the difference between the planet continuing to function for 5 billion years or 10 billion years. When the fuel does run out, which McDonough said will happen, then the planet will essentially "die" as its planetary processes no longer function.

The detectors used to find the antineutrino particles are each the size of a small office building, housed about a mile underground. Antineutrinos are identified inside the detector when the particles crash into a hydrogen atom, causing two characteristic light flashes. There are currently two such detection facilities, in Japan and Italy, which record only about 16 collisions per year. Three new detectors — one in Canada and two in China — are expected to come online in 2022.

"Once we collect three years of antineutrino data from all five detectors, we are confident that we will have developed an accurate fuel gauge for the Earth and be able to calculate the amount of remaining fuel inside Earth," McDonough said in the statement about the team's 2025 goal.

The study was published Sept. 9 in the journal Nature Scientific Reports.

Original article on Live Science.

If you're trying to stabilize nuclear waste, don't use organic kitty litter.

That's the take-away of a 277-page report, just released by the Department of Energy (DOE), on a radioactive leak that occurred at the underground Waste Isolation Pilot Plant (WIPP) east of Carlsbad, New Mexico, on Feb. 14, 2014.

Investigators confirmed that a 55-gallon metal drum of nuclear waste burst open after it was packed with the wrong kind of cat litter, as had been suspected since last year. [Nuclear Security: Best & Worst Countries (Infographic)]

Kitty litter isn't just used to absorb urine; it's long been used for industrial purposes, too. Traditional cat litter is usually made from inorganic silicates that can stabilize nitrate salts found in nuclear waste, James Conca explained in Forbes last year.

"Nitrate salt solutions can ignite when they dry out," Conca wrote. "So you need to stabilize nitrate solutions before they dry out, or prevent them from completely drying out."

When the drum in question was packed at Los Alamos National Laboratory, in New Mexico, it was filled with organic kitty litter called Swheat Scoop, which, as the name suggests, is primarily made with wheat. A report in the Santa Fe New Mexican last year suggested the mistake might have stemmed from a typo in Los Alamos' policy manual, which said to ensure "an organic absorbent (kitty litter)" was added to the waste when preparing drums of nitrate salt.

DOE officials concluded the contents of the drum were "chemically incompatible" and that gases built up over time, causing the lid to burst open after it was stored at WIPP.

"Experiments showed that various combinations of nitrate salt, Swheat Scoop®, nitric acid and oxalate self-heat at temperatures below 100 degrees C (212 degrees Fahrenheit)," DOE officials wrote in a summary of the findings. "Computer modeling of thermal runaway was consistent with the observed 70-day birth-to-breach of Drum 68660."

No one was seriously hurt as a result of the accident, though 21 people were exposed to low-level radioactivity.

WIPP is used to store drums full of things like debris, protective gear and tools that have been contaminated with plutonium and other artificial radioactive elements created during nuclear weapons development. The facility is the nation's only permanent underground nuclear waste dump, located about a half-mile underground in geologically stable salt deposits.

But WIPP has been closed since the accident, and it might take more than a half-billion dollars to get the facility operational again, the Albuquerque Journal reported. However, U.S. Energy Secretary Ernest Moniz said this week that the dump could be back online in about a year.

Follow Megan Gannon on Twitter. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Extremely low levels of radioactive cesium from Japan's 2011 Fukushima nuclear meltdown are present in ocean water offshore Northern California, researchers announced Monday (Nov. 10).

In seawater collected about 100 miles (161 kilometers) offshore of Eureka, the amount of cesium-134 was 2 Becquerels per cubic meter of water (a unit of measure based on the number of radioactive decay events per second per 260 gallons of water). That's about 1,000 times lower than the drinking water limit set by the U.S. Environmental Protection Agency.

This level of radioactivity does not represent a health hazard for people who want to fish or swim in the area, said Ken Buesseler, a marine chemist at the Woods Hole Oceanographic Institution in Massachusetts, who helped analyze the seawater. Buesseler is leading a crowdfunded citizen science program to track cesium levels from the meltdown by collecting water samples along the U.S. and Canadian West Coast.

A swimmer who spent 6 hours every day for a year in water with 10 Becquerels per cubic meter of cesium-134 would still receive 1,000 times less radiation than the dose from a single dental X-ray, Buesseler said. "Now, we have measurements that confirm that for human health, when a mother from Santa Cruz calls me and asks if it's safe for my son to go surfing, we have far fewer concerns," he said.

To date, no cesium-134 has been found at Canadian or U.S. beaches, including those in Hawaii, Alaska, Washington, Oregon and California. The short-lived isotope has only been detected offshore.

Cesium-134 does not occur on its own in nature — only forming in nuclear reactors — and it has a short two-year half-life. These qualities make cesium-134 an ideal tracer of the pollution from the Fukushima Daiichi nuclear power plant meltdown following the 2011 Japan earthquake and tsunami. [Fukushima Radiation Leak: 5 Things You Should Know]

The new results also support fish sampling results from the Food and Drug Administration, Buesseler said. To date, the FDA has not detected radioactive iodine or cesium in fish caught in the North Pacific and Alaska waters, where currents carry the Fukushima pollution.

It's possible that cold currents that upwell along the West Coast, especially along California, may keep the eastward-flowing cesium-134 from reaching beaches for several more months, but researchers need more data to confirm this idea.

"It's not a public health threat, but those last 100 miles are pretty tricky," Buesseler said.

It costs about $550 to $600 to test each sample at Buesseler's lab. No federal or state research agencies have stepped in to help offset the costs, so public fundraising pays for the analyses.

The latest samples were collected on donated time during a research cruise from Dutch Harbor, Alaska, to Eureka, California, by the Moss Landing Marine Laboratories in California. LUSH Cosmetics donated $12,000 to test 24 water samples, but another 20 or so samples are still sitting, waiting for someone to underwrite the cost.

Buesseler will present the findings Thursday (Nov. 13) at the Society of Environmental Toxicology and Chemistry's annual meeting in Vancouver, British Columbia.

Follow Becky Oskin @beckyoskin. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

How fast is really fast? If you're going by the U.S. Navy's standards, it's about 2.25 million mph (3.6 million km/h).

That's how fast the Navy's giant Nike laser can move a "target" (i.e., a tiny capsule about the size of a peppercorn), according to the U.S. Defense Department. The laser pulses a super-strong beam of electrons through a mixture of gases. This speeds up the electrons and makes it possible for this beam of energy to move things at extremely high speeds. In fact, the laser moves things so quickly that it recently earned a Guinness World Records title for achieving "Highest Projectile Velocity," a distinction previously held by researchers in Japan.

While the laser's world record title isn't as easy to digest as some others — say, "World's Biggest Hot Dog" — it's still a significant achievement. The laser is at the forefront of clean energy, according to Guinness World Records officials, enabling researchers to study nuclear fusion as an environmentally friendly energy alternative.

Stationed at the U.S. Naval Research Laboratory in Washington, D.C., the fluoride krypton (KrF) laser works by heating up a fuel target, something that researchers with the project call a "thin plastic foil." Typically, the fuel targets used for confined nuclear fusion reactions contain a mixture of deuterium and tritium, two hydrogen isotopes, but the U.S. Navy Lab doesn't specify what kind of fuel target they used for their experiments with the Nike laser.

When the laser heats up the tiny piece of plastic foil, the target accelerates to a speed of up to 2.25 million mph (3.6 million km/h). To put that into perspective, it's over twice as fast as the fastest-spinning star in the galaxy, which rotates around at a dizzying pace of 1 million mph (1.6 million km/h).

The fuel target travels a fraction of an inch (less than 1 millimeter) before arriving at its destination (its goal is to collide with another, stationary piece of foil). The impact generates an enormous amount of pressure, which compresses the fuel target. In other words, the piece of plastic foil becomes extremely dense and extremely hot, setting off fusion reactions that can be used to produce energy.

If this process sounds complicated, that's because it is. Known as inertial confinement fusion, it's one of several processes used to initiate nuclear fusion, the type of reaction that powers both stars and hydrogen bombs.

The set of experiments that won the U.S. Navy its Guinness World Record title were performed nearly five years ago, according to Armed with Science, the official blog of the U.S. Department of Defense. However, researchers at the Navy Lab just recently received their certificate from Guinness World Records officials.

Since then, Navy researchers have actually increased the speed at which the laser can move its target. The new "really fast" is about 2.6 million miles per hour (4.2 million km/h), according to the researchers.

Follow Elizabeth Palermo @techEpalermo. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

This article was originally published at The Conversation. The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.

Engineers at Fukushima nuclear power plant have been trying to create a £185m ice wall to isolate contaminated water from mixing with groundwater. However, there has been a steady stream of news articles reporting on problems associated with the work so far. They are simply adding to the sense of despair and distrust that has hung over the clean-up operation since the disaster occurred at the site more than three years ago. However, a closer look at the technology inspires hope.

Strong foundations

Artificial ground freezing (AGF) is not as crazy as it might sound. It is a technique that has been used in civil engineering for more than a century. Invented by German engineer FH Poetsch in the 1880s for use in the mining industry, the principle of the process has not changed since then.

The idea is to pipe brine solution (extremely salty water) at –30°C to extract heat from the under the surface, and to cause the water in cracks and pores to freeze. The ice binds the rock and soil grains together in a sheet up to several metres thick, while also preventing the movement of unfrozen water through the ground.

At Fukushima, they will insert 1,550 pipes that go 33 metres deep. In the last month 100 pipes have been put in place, and testing has begun.

The freezing of the ground has two effects – improved strength and reduced permeability – which make AGF a useful solution to a range of civil engineering problems. As well as stabilising shafts and preventing water from entering working areas in mines, AGF is widely used in construction of dams and tunnels, where water can make the excavation impossible.

Two of the largest, most complex infrastructure projects in the US in recent years – the “Big Dig”, tunnelling an interstate beneath downtown Boston, and the New York East Side Access project which involves boring a new rail tunnel beneath already-buried road and rail networks – have used AGF extensively. It has also been one of the standard options on the table for engineers on London’s £15 billion Crossrail project.

In all these cases, ice-wall technology holds advantages over other methods. It is completely reversible with minimal environmental footprint. It can accommodate a wide range of soil formations and structures, critically giving it the ability to operate in sites which already harbour buried structures and services, such as at Fukushima.

Complex, but not sci-fi

Despite the long history of ice-wall technology in civil engineering, every project is different and subsurface environments are notoriously complex. Things can, and do, go wrong. Nevertheless, the key risk factors are well known. Poor design and maintenance of the refrigeration system is a predictable hazard, manageable through strong project leadership and use of well-informed AGF specialists in both the specification and implementation phases.

Less predictable is the effect of groundwater flow, which is a critical factor at Fukushima since groundwater management is the primary objective of building an ice wall there. Moving water freezes less easily than stationary water, and when it does it is not easy to predict how it would do so. Improvements in computer simulation of freezing behaviour in porous media and in modelling the complexity of subsurface environments are key.

So the scale of the challenges faced by the ice-wall engineers at Fukushima are huge. But they are not unprecedented. Ground freezing has even been used for radiation mitigation before, for example at mining operations in Canada and Australia where radioactive radon gas is a threat to the health and safety of mineworkers. The idea of using ice-wall technology to isolate and treat a volume of contaminated groundwater – exactly the objective at Fukushima – is based on patents outlining the concept of an underground ice-walled storage volume dating back to the 1960s.

None of this diminishes the magnitude of the problems facing engineers and managers at the world’s highest-profile contaminated site. But the ice-wall technology itself is not the bizarre stunt that has sometimes been portrayed. It might even work.

Next, read this: What is the ‘acceptable risk’ when planning a nuclear power plant?

Jonathan Bridge receives funding from the Natural Environmental Research Council and the Technology Strategy Board. He consults to the UK National Nuclear Laboratory.

This article was originally published on The Conversation. Read the original article. Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.

So-called "green" kitty litter may be a good idea for eco-conscious cat lovers, but it's a bad idea for nuclear waste storage.

That's the assessment from an investigation into a radiation leak that occurred at the only nuclear waste storage site in the United States, the underground Waste Isolation Pilot Project (WIPP) located east of Carlsbad, New Mexico.

The radiation leak occurred Feb. 14: Nine days earlier, a truck inside the underground facility caught fire. Though the two events were likely unrelated, investigators fear they both resulted from a lax safety culture that has developed at the nuclear waste facility, according to the Associated Press. [Nuclear Security: Best & Worst Countries (Infographic)]

"I'm just dying to know why this happened and who approved it, because it was a dumb idea," Jim Conca, a scientist who worked at WIPP from 2000 to 2010, told the Associated Press, referring to the organic kitty litter. "You just can't make a change to the procedure without reviewing it."

Why kitty litter?

Though it may seem strange to use a product as mundane as kitty litter to safeguard the nation's nuclear waste, kitty litter has been used for decades at industrial facilities.

Older types of kitty litter are made of clay — especially bentonite clay — which readily absorbs and holds liquids. Cat litter and other clay-based compounds are frequently used at oil drilling facilities, petroleum bulk plants and gas stations to clean up spills and control liquid wastes.

Clay-based cat litter can also be used to control odors and mold in garbage cans and diaper pails; eliminate oil, engine coolant and other driveway stains; clean up spilled paint (before it dries); eliminate rodents; and add traction on icy roads and sidewalks.

"Cat litter has been used for decades in radiochemistry labs and nuclear facilities to stabilize certain radwastes [radioactive wastes], like liquid scintillation solutions, evaporator bottoms and other materials," Conca wrote in Forbes, referring to industrial wastes that contain radioactive material.

However, the switch from clay-based kitty litter to an organic kitty litter — which is usually made from wheat, corn and recycled paper or pine sawdust — may have triggered a chemical reaction that led to the radiation leak at WIPP, according to the preliminary investigation.

How safe is WIPP?

The ongoing investigation at WIPP, which is about 2,100 feet (640 meters) underground in geologically stable salt deposits, has yet to determine the exact cause of the radiation leak. "Kitty litter is in the field of theories," Jill Turner, spokeswoman for the New Mexico Environment Department, told Reuters.

The amount of radiation released from WIPP is considered minor: "The levels of Pu [plutonium] and Am [americium] released were a million times less than any environmental concern, thousands of times less than any health concern, and 40 times less than ordinary background," Conca wrote in Forbes.

WIPP had operated since 1999 with no significant safety problems, officials have asserted. The facility is expected to hold nuclear material safely for millions of years into the future — the salt deposits in the region have been stable for more than 200 million years.

Nonetheless, officials are concerned that investigators found melted plastic and rubber on some of the drums and boxes holding radioactive waste, suggesting that some kind of heating occurred in the area where the waste is stored.

While the investigation proceeds, officials have closed the facility to all incoming waste. WIPP accepts nuclear waste from Los Alamos National Laboratory, Idaho National Laboratory and the Savannah River Site (a nuclear weapons site) in South Carolina.

"I just hope it doesn't take years to get back on track, because it would be a shame," Conca told the Carlsbad Current Argus. "It is wrong to erase 15 years of a perfect record. Look at the chemical industry or the oil industry. People die from explosions and no one calls to shut down the oil industry."

Follow Marc Lallanilla on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

This article was originally published at The Conversation. The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.

It is the received wisdom that nuclear weapons and nuclear power are inseparable. Consequently, any country that builds a civilian nuclear power station is able to build an atomic bomb within a couple of years.

Clearly there are overlaps in knowledge and technology between the civil and military nuclear industries. How closely is power generation connected with weapons production?

Experiments in the 1960s, and a student project in the 1970s, showed that a well-informed scientist could get close to recreating the design of Fat Man, the atomic bomb used at Nagasaki.

Information about the physics of a nuclear weapon’s core is probably not the limiting factor in nuclear proliferation. The critical part of a nuclear bomb, which sets it apart from any other weapon, is the presence of an amount of a material (known as fissile material) that is capable of maintaining a nuclear chain reaction (called the critical mass). This usually means either uranium or plutonium.

While uranium is naturally occurring, plutonium is for all practical purposes a synthetic element – only produced by man.

However, it’s not as simple as digging up sufficient uranium ore and extracting the uranium metal. Only one isotope of uranium (²³⁵U) and one of plutonium (²³⁹Pu) can conveniently be used to manufacture a weapon (I’ll explain what the numbers mean below).

²³⁵U only occurs as around 1% of natural uranium. The other 99% is ²³⁸U.

To make a practical uranium bomb, about 60kg of 80% pure ²³⁵U is needed. There are several methods for separating ²³⁵U from ²³⁸U. All methods are complex and the details of some remain classified.

Heavier isotope, smaller bomb

You probably noticed that the superscript 238 (as in ²³⁸U) is one less than 239 (from ²³⁹Pu) – this is important.

Inside a nuclear reactor there is a large number of free particles called neutrons. It is the neutrons that mediate the nuclear reactions.

When a neutron hits the nucleus of a ²³⁵U atom, the nucleus usually splits into two large pieces and releases several new neutrons. This is the process known as fission.

A neutron hitting a nucleus does not always cause fission. ²³⁸U can absorb a neutron and after a couple of other reactions become ²³⁹Pu. This process is known as breeding.

Again this is significant – compared with ²³⁵U’s bare critical mass of ~50kg, the bare critical mass of ²³⁹Pu is around 11kg. In other words, the amount of material needed to make a bomb with ²³⁹Pu is a fifth that of ²³⁵U.

These figures can be lowered to around 4kg ²³⁹Pu for very advanced designs. Fat Man used around 6.2kg and some advanced methods, such as using a tamper and polonium based neutron boosting. The potentially much lower critical mass of plutonium makes it the preferred material for weapons production.

Another advantage of plutonium is that it has different chemical properties and reactivities to uranium. So, rather than needing sophisticated isotope separation technology, the two metals can be separated by well-known metal processing chemistry (such as the PUREX method which involves dissolving them in acid, reacting both metals with an organic compound, extracting the organic compounds into kerosene and selectively reducing the plutonium so that it can be re-extracted back into water).

Side effects of breeding plutonium

²³⁹Pu is fissile, if a neutron hits it; about 75% of the time it splits. The other 25% of the time, the nucleus captures another neutron to become ²⁴⁰Pu.

²⁴⁰Pu is much less likely to capture another neutron. Therefore, over time the amount of ²⁴⁰Pu compared with ²³⁹Pu in a reactor core will go up. This isn’t a problem as such for the reactor (although it can create waste issues), but is a huge problem for nuclear weapons manufacture.

Induced vs spontaneous

Above I described induced fission. The question left hanging is – where does the first neutron in the chain come from?

Some atoms, when they undergo radioactive decay, do not follow their usual pathway (alpha decay for ²³⁹Pu and ²⁴⁰Pu). One in five million ²⁴⁰Pu atoms and one in five trillion ²³⁹Pu atoms undergo spontaneous fission, meaning they break up without warning and release some neutrons. These events are where those “first neutrons” can come from.

The high spontaneous fission rate of ²⁴⁰Pu acts as a kind of poison in the core of nuclear bombs. More than about 7% ²⁴⁰Pu and the likelihood that the warhead won’t work increases, and the dangers of handling the more radioactive ²⁴⁰Pu become too great.

The 7% limit is reached in a typical nuclear reactor after about 90 days (depends on the reactor design and the 235U enrichment). Typical commercial power reactor fuel cycles are around two years. If the fuel cycle is shorter the electricity becomes uneconomic.

All this means that the plutonium than can be extracted from the fuel rods of a commercial nuclear power reactor is not suitable for making nuclear weapons.

Historical perspective

There are five declared and four other nuclear-armed countries (assuming Israel’s warheads detonate). There are 31 nations with nuclear power stations (and 58 with research reactors). Only seven of the nine nuclear-armed countries have civilian power programs.

All of the technical factors can be circumvented with sufficient time and money. Uneconomic fuel cycles can be run and warheads built with high levels of radioactivity. However, no country has developed indigenous nuclear weapons after deploying civilian nuclear power stations.

Historically, if a country wants to produce a nuclear bomb, they build reactors especially for the job of making plutonium, and ignore civilian power stations.

Martin Boland receives funding from and collaborates with the Australian Nuclear Science and Technology Organisation.

This article was originally published at The Conversation. Read the original article. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science .