What

Nuclear fusion could potentially provide abundant, safe energy without the significant production of greenhouse gas emissions or nuclear waste. But it has remained frustratingly elusive as a practical technology for decades. An important milestone toward that goal has now been passed: a fusion reaction that derives most of its heat from its nuclear reactions themselves rather than the energy pumped into the fuel from  at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) in California has reported this so-called burning plasma condition using an approach called inertial-confinement fusion, where the ferociously high temperatures and pressures needed to initiate fusion in a fuel of hydrogen isotopes are produced by intense pulses of laser light. The researchers’ findings appear in Nature, with companion papers published in Nature Physics and on the preprint repository arXiv.org. “The data clearly show that they have reached that condition,” says fusion physicist George  of tha University of California, San Diego, who was not involved in the work.NIF results are a really big deal,” says fusion physicist Peter Norreys of the University of Oxford, who was not part of the studies. “They show that the pursuit of an inertial fusion reactor is a realistic possibility for the future and not built upon difficult and insurmountable physics.” Plasma physicist Kate Lancaster of the University of York in England, who was also not involved in the research, agrees. This is an incredible achievement, which is a culmination of a decade of careful, incremental research, she says.Nuclear fusion, the process that fuels stars and that is triggered explosively in hydrogen bombs, requires extreme heat and pressure to give atoms enough energy to overcome the electrostatic repulsion between their positively charged nuclei so that they can fuse and release energy. The usual fuel for producing controlled fusion in reactors consists of a mix of the heavy hydrogen isotopes deuterium and tritium, which may unite to make helium. The energy this releases can be harnessed for electricity generation—for example,by using the heat to drive conventional power turbines. Unlike nuclear fission—the process used in all nuclear power plants today—fusion does not use or generate large quantities of long-lived radioactive materials. And in contrast to fission, fusion does not involve a chain reaction, which makes it inherently safer: any changes to the working conditions of a fusion reactor will cause it to automatically shut down in an instant.Fission’s advantage is that it typically occurs in reactors at temperatures of a little more than 1,000 kelvins, whereas deuterium-tritium (D-T) fusion starts at temperatures of around 100 million kelvins—hotter than the heart of the sun. Handling such a seething plasma is, to put it mildly, immensely challenging. One approach is to confine it with magnetic fields into a doughnut shape inside a chamber called a tokamak. This is the method of choice for many fusion projects, including the International Thermonuclear Experimental Reactor (ITER). for which a global collaboration is building a massive experimental reactor in France that is slated to achieve sustained fusionno earlier than 2035