![]() In the process, they release a small part of their combined mass as energy. In fusion, however, small, light atoms such as hydrogen fuse into bigger ones. Today’s nuclear power plants rely on nuclear fission, which releases energy when large, heavy atoms such as uranium break apart due to radioactive decay. Though nuclear fusion and nuclear fission both draw energy from the atom, they operate differently. “It looks like science fiction, but they did it, and it’s fantastic what they’ve done,” says Ambrogio Fasoli, a fusion physicist at the Swiss Federal Institute of Technology in Lausanne. “It’s a fundamental building block.”Įven so, after decades of trying, scientists have taken a major step toward fusion power. “I don’t want to give you the sense that we’re going to plug the NIF into the grid-that’s not how this works,” Budil added. According to Kim Budil, director of Lawrence Livermore National Laboratory, the lasers required 300 megajoules of energy to produce about 2 megajoules’ worth of beam energy. While NIF’s reaction produced more energy than the reactor used to heat up the atomic nuclei, it didn’t generate more than the reactor’s total energy use. ![]() The achievement does not mean that fusion is now a viable power source. Being able to study the conditions of ignition in detail will be “a game-changer for the entire field of thermonuclear fusion,” says Johan Frenje, an MIT plasma physicist whose laboratory contributed to NIF’s record-breaking run. In reaching scientific breakeven, NIF has shown that it can achieve “ignition”: a state of matter that can readily sustain a fusion reaction. Energy Secretary Jennifer Granholm said at a Washington, D.C. “Simply put, this is one of the most impressive scientific feats of the 21st century,” U.S. ![]() Fusion researchers have long sought to achieve net energy gain, which is called scientific breakeven. Though the conflagration ended in an instant, its significance will endure. In a tiny blaze lasting less than a billionth of a second, the fusing atomic nuclei released 3.15 megajoules of energy-about 50 percent more than had been used to heat the pellet. The pellet compressed and generated temperatures and pressures intense enough to cause the hydrogen inside it to fuse. On December 5, an array of lasers at the National Ignition Facility (NIF), part of the Lawrence Livermore National Laboratory in California, fired 2.05 megajoules of energy at a tiny cylinder holding a pellet of frozen deuterium and tritium, heavier forms of hydrogen. For the first time, a fusion reactor has produced more energy than was used to trigger the reaction. Today, researchers announced a milestone in this effort. So, one can release energy either by splitting very large nuclei, like uranium with 92 protons, to get smaller products, or fusing very light nuclei, like hydrogen, with just one proton to get bigger products.For more than 60 years, scientists have pursued one of the toughest physics challenges ever conceived: harnessing nuclear fusion, the power source of the stars, to generate abundant clean energy here on Earth. It turns out that the most tightly bound atomic nuclei are around the size of iron, which has 26 protons in the nucleus. ![]() If a nuclear reaction produces nuclei that are more tightly bound than the originals then energy will be produced by fusion, and for fission the opposite is true. The key to why some atoms split and release energy while others fuse to do the same lies in how tightly the protons and neutrons are held together. Binding energy Smaller nuclei fuse and release energy until at iron no more energy is released by fusion. This is why fusion is still in the research and development phase – and fission is already making electricity. The reasons that have made fusion so difficult to achieve to date are the same ones that make it safe: it is a finely balanced reaction which is very sensitive to the conditions – the reaction will die if the plasma is too cold or too hot, or if there is too much fuel or not enough, or too many contaminants, or if the magnetic fields are not set up just right to control the turbulence of the hot plasma. Unlike nuclear fission, the nuclear fusion reaction in a tokamak is an inherently safe reaction.
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