This Tuesday may be a day of red letters in world scientific history. The US Department of Energy will announce today a “scientific breakthrough” in the field of nuclear fusion. Last weekend, the British newspaper Financial Times revealed that scientists at the Lawrence Livermore National Laboratory (LLNL), located in California, managed to obtain a “net gain of energy” from an experimental fusion reactor.
These revelations did not take long to arouse the enthusiasm of the international scientific community. In fact, nuclear fusion is a technology that could drastically change the relationship between humans and energy by making it more durable and sustainable. BFM Business takes stock of this technology, the advances in this area and what remains to be done to develop its full potential.
• Which is nuclear fusion?
As its name suggests, nuclear fusion consists of fusing two light atomic nuclei of hydrogen to create a heavy one, helium, in order to release energy during the process. It opposes nuclear fission, a technique used in nuclear power plants, which corresponds to breaking the bonds of heavy atomic nuclei. Fusion is a source of fascination because it is the process that takes place in stars, including our Sun. Thanks to the extreme conditions of heat and pressure that prevail there, hydrogen atoms fuse to form helium, producing an immense amount of energy in the process.
Fusion is only possible by heating the material to extremely high temperatures (on the order of over 100 million degrees). “So we have to find ways to isolate this extremely hot material from anything that could cool it down. That is the problem of confinement”, explains Erik Lefebvre, project manager of the Atomic Energy Commission (CEA).
• What are the two methods of fusion?
The first method is magnetic confinement fusion. Light hydrogen atoms (deuterium and tritium) are heated in a huge reactor. The matter is then in the state of plasma, a kind of very low-density broth. It is controlled by a magnetic field, obtained by magnets. This is the method that will be used for the international ITER project, currently under construction in France, and the one used by JET (Joint European Torus) near Oxford.
A second method is inertial confinement. There, very high-energy lasers are sent into a thimble-sized cylinder containing the hydrogen. This is the technique used by the French Laser Megajoule (LMJ), or the most advanced project in this field, the American National Ignition Facility (NIF), on which the Californian laboratory depends. The objective is then more to demonstrate the physical principle, when the first method seeks to reproduce a configuration close to a future fusion reactor.
• Why has LLNL made a breakthrough?
By achieving an unprecedented “net energy gain” in nuclear fusion, Lawrence Livermore National Laboratory scientists have for the first time produced more energy than the amount used to cause this reaction. According to the Financial Times, 2.5 megajoules of energy were produced, or 120% of the 2.1 megajoules used by the 192 lasers aimed at a target as small as a thimble, where lightweight hydrogen atoms are placed to fuse. .
Such a result would finally provide proof of a physical principle imagined decades ago. It would therefore be a “success for science”, stressed Tony Roulstone, a professor at the University of Cambridge. If this breakthrough is confirmed, “this is a huge step forward, extremely exciting,” said Jeremy Chittenden, professor of plasma physics at Imperial College London. “Proof that the long-sought goal, the holy grail of fusion, can be achieved.”
Unlike fission, fusion does not carry any risk of a nuclear accident. “If there are ever some lasers missing that don’t fire at the right time, or if ever the confinement of the plasma by the magnetic field (…) is not perfect,” the reaction will simply stop, explains Érik Lefebvre. Also, nuclear fusion produces less radioactive waste than current power plants. Above all, it does not generate greenhouse gases unlike coal or gas plants.
• Why is there still a long way to go?
“There is still a long way to go” before “an industrial-scale demonstration that is commercially viable,” warns Érik Lefebvre. According to him, such projects will take another 20 to 30 years to complete. Among the challenges: increasing the efficiency of the laser sources and reproducing the experiment at much higher rates.
Due to its still early stage of development, nuclear fusion does not represent an immediate solution to the climate crisis and the need for a rapid transition from fossil fuels. Therefore, to limit global warming it is absolutely necessary to reduce greenhouse gas emissions as much as possible today, all climate experts insist.
Other nuclear fusion projects are under development, notably the international ITER project, currently under construction in France. Instead of lasers, the so-called magnetic confinement technique will be used: hydrogen atoms will be heated in a huge reactor, where they will be confined by the magnetic field of magnets.
Source: BFM TV
