Nuclear fusion reactor 'breakthrough' is significant, but light-years away from being useful
Useful, cost-effective nuclear fusion remains a distant dream, despite a small step in the right direction from the government's NIF reactor.
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."
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Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.
By Robert Lea
Fusion is often promoted as the green energy source of the future, generating carbon-free power by fusing together hydrogen isotopes in the same way as the Sun. Getting the isotopes to meld requires extreme temperatures and every fusion reactor built so far has consumed more heat than it produces.
On 5 December, 2022, at the National Ignition Facility in Livermore, in the US, 192 laser beams hit a small capsule filled with deuterium and tritium housed in a golden cylinder, causing what physicists call ‘ignition’. For the first time, the amount of energy produced by a controlled nuclear fusion reaction was larger than the energy carried by the lasers used to initiate it. The target absorbed 2.05 megajoules of energy, emitting 3.15 megajoules in return, a 54% energy gain.
Why does it matter?
The potential to exploit this experimental scheme, called inertial fusion, to produce clean energy is still decades away. In fact, to deliver 2.05 megajoules on to the target, the laser system absorbed the sum of nearly 322 megajoules of electric energy from the grid.
Nevertheless, the result is big news to scientists. “It was 10 years in the making”, says Stefano Atzeni, an expert in inertial fusion at Sapienza university in Rome. “NIF was supposed to reach ignition a few years after its launch in 2009, but the first round of experiments yielded just a few kilojoules.”
NIF was not originally built to produce energy, but to maintain the US thermonuclear weapon stockpile, offering an alternative way to test them after underground nuclear tests were banned in 1996. But the latest results expanded its mission from national security to energy programmes, with the inclusion of the inertial approach in the 10-year plan for commercial fusion energy launched by the White House in March.
In 2012 in France, ASN validated ITER’s overall design and authorized construction to start. But it imposed several “hold points” in the construction process when ITER must demonstrate that the reactor meets safety requirements. One of those points comes when workers are set to lower and weld together the first two of nine reactor sections, each weighing 1200 tons, because the process is irreversible: The welded sections are too heavy to remove from the pit if any later changes or inspections are required.
France’s nuclear regulator has ordered ITER, an international fusion energy project, to hold off on assembling its gigantic reactor until officials address the safety concerns inherent in the project. The ITER Organization was expecting to get the green light to begin to weld together the 11-meter-tall steel sections that make up the doughnut-shaped reactor, called a tokamak.
But on 25 January, 2022, France’s Nuclear Safety Authority (ASN) sent a letter ordering a stoppage until ITER can address concerns about neutron radiation, slight distortions in the steel sections, the failure of the steel at high temperatures, and the loads on the concrete slab holding up the reactor.
ITER staff say they intend to satisfy ASN by April so they can begin to weld the reactor vessel by July. “We’re working very hard for that,” says ITER Director-General Bernard Bigot.
The ASN letter was reported by New Energy Times on 21 February but was obtained independently by Science. It highlights three problem areas. The first concerns loads on the structure holding up the tokamak. Known as the B2 slab, it is a 1.5-meter-thick block of reinforced concrete the size of two U.S. football fields. It rests on 493 seismic dampers to isolate the reactor from earthquakes. It’s designed to support 400,000 tons, but ASN wants reassurance that, following some design changes during construction, the loads on the slab are still within safety limits. “We have to complete a modeling of the mass as built,” Bigot says.
A second concern is over radiation protection for staff working near the reactor once it begins operations. The main radiation coming out of the reactor will be high-energy neutrons, which are stopped by the thick concrete walls in the building that will surround the reactor. No one will be in the reactor building when it is operating, Bigot says. But over its lifetime, the reactor itself becomes radioactive from the neutron bombardment, creating a complicated radiological environment for workers who enter the building when the tokamak is not in operation. Existing “radiological maps do not make it possible to demonstrate control of limiting exposure to ionizing radiation,” ASN says, according to a translation of its letter.
Bigot says ASN usually only requires nuclear facilities to produce a 2D model of potential radiation exposures. But ITER built a 3D simulation to predict neutron fluxes more precisely. ASN wants more evidence that this model is as robust as the simpler one, Bigot says. “We have to demonstrate that our choice is the best option.”
A third concern is over welding the first two tokamak sections. Following their construction in South Korea, managers discovered slight deformities in the surfaces that must be welded together. ITER staff developed a fix that would involve both robotic and human welders, but ASN is not convinced. Bigot says he now has a report from the Spanish company that developed the robotic welding system. The company tested the process on a full-scale mockup and showed it will be possible for workers to get into the confined spaces needed to make the welds. That report will form part of ITER’s April response to ASN.
In experiments culminating the 40-year run of the Joint European Torus (JET), the world’s largest fusion reactor, researchers announced today they have smashed the record for producing controlled fusion energy. On 21 December 2021, the U.K.-based JET heated a gas of hydrogen isotopes to 150 million degrees Celsius and held it steady for 5 seconds while nuclei fused together, releasing 59 megajoules (MJ) of energy—roughly twice the kinetic energy of a fully laden semitrailer truck traveling at 160 kilometers per hour. The energy in the pulse is more than 2.5 times the previous record of 22 MJ, set by JET 25 years earlier. “To see shots in which it sustains high power for a full 5 seconds is amazing,” says Steven Cowley, director of the Princeton Plasma Physics Laboratory (PPPL).
JET was a testbed. Starting in 2006, engineers upgraded its magnets, plasma heating system, and inner wall to make it as ITER-like as possible. When it restarted in 2011, the signs were not good, says Cowley, who was then director of the Culham Centre for Fusion Energy, which runs JET on behalf of the European Union’s EuroFusion agency. “We couldn’t get into the same regimes.”
JET’s recent achievement doesn’t mean fusion-generated electricity will flow into the grid anytime soon, however. Researchers had to put roughly three times as much energy into the gas as the reaction produced.
But the result gives them confidence in the design of ITER, see above, a giant fusion reactor under construction in France, which is supposed to pump out at least 10 times as much energy as is fed in. “This is very good news for ITER,” says Alberto Loarte, head of ITER’s science division. “It strongly confirms our strategy.”
Fusion has long been promoted as a future green energy source. If the same nuclear reaction that powers the Sun could be duplicated on Earth, it could provide plentiful energy with small amounts of nuclear waste and no greenhouse gases. But producing net energy has proved elusive. In August 2021, researchers at the National Ignition Facility, which triggers fusion by heating and crushing tiny pellets of fuel with 192 converging laser beams, reported they had gotten to 71% of this break-even mark, closer than anyone else, but only for an instant.
The UK's JET and France's ITER, in which Japan was promised 20% of the research staff on the French location of ITER, as well as the head of the administrative body of ITER, represent different approaches, one that is more suitable for sustained energy production. Both are tokamaks: doughnut-shaped vessels wrapped in a grid of powerful magnets that hold the superhot ionized gas, or plasma, in place and prevent it from touching and melting the vessel walls. Researchers in the 1980s believed JET and a rival machine at PPPL (DOE's Princeton Plasma Physics Laboratory is located at Princeton University's Forrestal Campus approximately three miles north of the University's main campus, now dismantled) would quickly reach breakeven. JET got close in 1997, generating a short, 1.5-second burst that reached two-thirds of the input power.
But slow progress spurred researchers in the 1990s to design ITER, an enormous tokamak 20 meters wide that holds 10 times as much plasma as JET. A larger plasma volume, models predicted, would maintain fusion conditions longer by making it harder for heat to escape. The $25 billion ITER, funded by China, the European Union, India, Japan, South Korea, Russia, and the United States, is due to start operation in 2025 but won’t produce large amounts of power until 2035, when it is due to start burning the energy-producing isotopes deuterium and tritium (D-T).
JET’s early operation taught ITER’s designers a key lesson. JET was lined with carbon because it resists melting. But it turned out to “soak up fuel like a sponge,” says Fernanda Rimini, JET’s plasma operations expert. So ITER’s designers opted to use the metals beryllium and tungsten.
Painstakingly, the JET team worked out what was going on. They found that high energy plasma ions were knocking out tungsten ions from the wall, causing them to radiate energy and bleed heat out of the plasma. Over many years, the team worked out a coping strategy. By injecting a thin layer of gas, such as nitrogen, neon, or argon, close to the vessel wall, they could cool the outermost edge of the plasma and stop ions from hitting the tungsten. “Bit by bit we clawed back performance,” Cowley says.
In September 2021, JET researchers set out to see what their redesigned machine could do. That meant switching fuel, to D-T. Most fusion reactors run on ordinary hydrogen or deuterium, which allows them to explore the behavior of plasmas while avoiding the complications of tritium, which is both radioactive and scarce. But JET staff were itching to test their machine in real power-producing conditions. First, they had to revive the reactor’s tritium-handling facilities, not used for 2 decades, which extract unburned tritium and deuterium ions from waste gas after each shot and recycle them.
Important preparatory research for ITER is conducted in the Joint European Torus JET in Culham in Oxfordshire. Many ITER details like the beryllium-coated tiles for the inside of the vacuum vessel, or the divertors that function like ‘vacuum cleaners’, getting rid of the extra helium-4 nucleus’ and other unwanted particles in the hot plasma, were developed in Oxfordshire. In 1997, JET set a world record by achieving 16 MW of fusion power, while the input was 24 MW – this is a ratio of 66 percent: not perfect, but fusion research is moving ahead. In the year 2003, JET has experimented with small amounts of tritium, and in 2018 experiments with deuterium-tritium plasmas are scheduled.
The 12th ITER International School will be held from 26 to 30 June 2023, hosted by Aix-Marseille University in Aix-en-Provence, France. The subject of the 2023 school is "The Impact and Consequences of Energetic Particles on Fusion Plasmas" with a scientific program coordinated by Simon Pinches (ITEROrganization).
Established in 2007, the ITER Organization is a collaborative energy project involving 35 countries. It received the nuclear power operator license from the French authorities in 2012.
The seven domestic agencies of the ITER include the European Union, India, Japan, South Korea, China, Russia, and the US. Fusion for Energy is the participant in the ITER project from the European Union.
Tokamak, is a Russian acronym, which means toroidal or doughnut-shaped chamber with magnetic coils. The various components of the ITER Tokamak include vacuum vessel, cryostat, electromagnet system, blanket modules and divertors.
Nuclear fusion takes place in the vacuum vessel of the Tokamak when two hydrogen isotopes, deuterium and tritium, react to create an electrically charged gas called plasma at temperatures of 150 million degree Celsius. The vacuum vessel can hold 840m3 of plasma.
The fusion reaction continues for long duration by the heat generated in the plasma. The Tokamak uses magnetic field generated by the electromagnet system to confine and control the plasma.
The ITER Tokamak vacuum vessel is a doughnut-shaped stainless steel vessel. It has a height of 11.4m, outer diameter of 19.4m and an interior volume of approximately 1,400m3.
The vacuum vessel will have double walls and the space between them will be filled by approximately 9,000 modular blocks, which act as a shield from neutron radiation. Borated and ferromagnetic stainless steel will used to make the blocks, which weigh up to 500kg each.
A cylindrical vacuum chamber called cryostat will house the vacuum vessel and the electromagnet system. The volume of cryostat is 16,000m³ and internal diameter is 28m. It is made of stainless steel and weighs approximately 3,850t.
The space between the vacuum vessel and cryostat will be filled with two layers of thermal shielding made of stainless steel panels. Europe will deliver five vacuum vessel sectors and the remaining four will be supplied by South Korea. The modular blocks will be supplied by India, which is also responsible for supplying the cryostat.
The inner wall of the vacuum vessel is covered by blanket modules to protect the structure from heat energy and fast-moving neutrons produced during nuclear fusion. As many as 440 blanket modules made of beryllium, high-strength copper and stainless steel will cover an area of 600m2 and provide nuclear shielding.
A divertor will be placed at the bottom of the vacuum vessel to remove heat released during fusion reaction, protect walls from fast-moving neutrons, and minimise plasma contamination. Tungsten will be used for manufacturing the divertor.electromagnet system
The ITER Tokamak will feature a 10,000t electromagnet system, which will have stored magnetic energy of 51 Giga Joules (GJ). The electromagnet system comprises of toroidal field magnets, poloidal field magnets, a central solenoid and correction magnets.
The vacuum vessel will be surrounded by 18 D-shaped toroidal field magnets that confines the plasma within the vessel. The magnets produce 41GJ of magnetic energy and a maximum field of 11.8 tesla. Each magnet weighs approximately 360t.
The project requires 19 toroidal field magnets including one spare. Japan is responsible for procuring ten toroidal field coils and the remaining nine will be supplied by Europe.
The poloidal magnet system consisting of six ring-shaped poloidal field coils is located outside the torroidal magnet system to shape the plasma. The magnets produce 4GJ of magnetic energy and a maximum field of 6 tesla.
The central solenoid consists of six independent coil packs made of niobium-tin cable, which enabls a powerful current to be generated in the plasma. It will have 6.4GJ of stored magnetic energy and a maximum field of 13 tesla. Central solenoid is being manufactured by the US, while Japan had supplied niobium-tin coils.
A total of 18 correction coils inserted between the toroidal and poloidal field coils will correct any magnetic field errors caused by main magnets due to imperfections in their manufacturing or their position. China will supply the correction coils.
Deuterium and tritium will be used as fuel for ITER Tokamak. Deuterium can be extracted from seawater, while tritium is a rare mineral and small quantities are produced during the nuclear fission reaction in Canada Deuterium Uranium (CANDU) reactors.
The tritium available globally will be sufficient for the operations of ITER for only 20 years. ITER’s Test Blanket Module programme is responsible for testing tritium breeding concepts by mounting lithium blanket modules inside the ITER vacuum vessel.
Scientifically, the neutron produced in the fusion process can react with lithium-6(2) to produce helium and tritium along with huge amount of heat energy. The commercial success of ITER concept depends on the production of tritium using lithium blanket modules.
ITER was supposed to cost about 5 billion Euros, but already five years later, the costs were estimated at 15 billion, with ‘first plasma’ in 2027 the earliest and further cost increases pending (a 2014 estimate talked about 21 billion US dollars). This makes ITER the most expensive terrestrial research collaboration ever – only the construction of the International Space Station ISS was more costly. An estimated investment of £15.5bn ($22.6bn) is being made in the project. Europe is making 45.46% contribution to the total project investment, while the remaining six members are contributing 9.09% each.
The ITER members are making in-kind contributions to the project by supplying various parts, systems and building facilities. The in-kind contributions account for approximately 90% of the total project cost and the remaining 10% is through cash.
The VFR consortium is responsible for the construction of the main buildings at the Tokamak complex. The consortium comprises of VINCI Construction Grands Projets, Razel-Bec, Dodin Campenon Bernard, Campenon Bernard, GTM, Chantiers Modernes, and Ferrovial Agromanis.
ITER-India, the ITER project participant from India, awarded a contract to L&T Heavy Engineering, a subsidiary of Larsen & Toubro, to design, manufacture and install ITER Cryostat in August 2012. MAN Energy Solutions and SPIE Batignolles TPCI are subcontractors for this project.
Mitsubishi Heavy Industries (MHI) will manufacture the inner coil structures for all 19 toroidal field coils.
Today, on the one hand, there is the promise of limitless energy supply, emission-free and without the long-term radiation problems of nuclear fission. The idea behind it is simple: in the Sun, the nuclei of hydrogen atoms are continuously fused into helium nuclei. This process releases enormous amounts of energy. Fusion researchers hope to reproduce this process in fusion reactors on Earth.
On the other hand, these promises have been made for at least six decades, with the first working fusion reactor always being ‘fifty years away’ – since fusion research started after the Second World War.
Cautious estimates today say that perhaps by 2060 or so, there might be a real fusion reactor that actually produces more energy than it requires. Existing experiments are far from this point. Furthermore, the international ITER project has mostly hit the headlines with reports on mismanagement and cost explosions. So where is fusion research today? Somewhere between lofty promises and stark realities.
Fusion of deuterium with tritium creates helium-4, freeing a neutron and releasing thermal energy in the process. Future fusion reactors are supposed to operate with a deuterium-tritium mixture.
Fusion of deuterium with tritium creates helium-4, freeing a neutron and releasing thermal energy in the process. Future fusion reactors are supposed to operate with a deuterium-tritium mixture. Credit: Wykis, Public Domain
Last month, the first successful plasma test at the Wendelstein 7-X at the Max Planck Institute for Plama Physics in Greifswald in northern Germany, experiment was hailed as the breakthrough. But not even this experiment is anywhere close to producing energy, on the contrary, it requires a lot of energy to heat helium plasma to about 100 million degrees centigrate, and to cool and power the superconductive magnetic coils at the same time to contain the plasma.
Plasma is one of the four fundamental states of matter, the others being solid, liquid and gas. It can be produced by heating gases to extremely high temperatures. This increases the number of charge carriers, making it not only the perfect state for fusion experiments, but also rendering it electrically conductive: thus it can be contained within a magnetic field. Plasma cannot contain itself. If it so much as touches the experiment’s walls, it would cool immediately and the experiment would be over. Only the lighter elements of the periodic table – lighter than iron – release energy when fused, the heavier elements absorb energy. Conversely, only the much heavier elements release enough energy in nuclear fission to make classic nuclear power stations possible.
So while the public hears about rising costs and management failures, science is slowly but surely making progress.