But that doesn't mean a fusion reactor will be coming anytime soon.
Scientists at a government lab in California have moved one tiny step closer to a long-standing dream: Generating energy from a fusion reaction, the same force that powers the sun.
That doesn't mean that a boundless source of clean, waste-free, and accident-proof nuclear energy is around the corner. But the experimental breakthrough does move researchers a step closer to solving some of the fundamental physics behind fusion, which has important implications for both energy production and national security.
Researchers at California's Lawrence Livermore National Laboratory reported Wednesday that for the first time, they have managed to get more energy out of the heart of a fusion reaction than they put into it.
"This is closer than anyone's gotten before, and it's really unique to get out of the fuel as much energy as put in," Omar Hurricane, the lead author of the paper announcing the results, said in a report published on the web site of Scientific American.
The breakthrough came after the scientists changed the way they bombarded a tiny capsule containing deuterium and tritium, two of the key isotopes of hydrogen used in fusion research, with energy from roughly 192 lasers. By blasting the target with more energy early on, they were able to keep it from imploding too quickly.
But overall, the experiment still required more energy input than was generated by the implosion. What's more, the tweak to the way the lasers bombard the target lowered the pressure inside. Achieving higher pressures is key to achieving the holy grail of fusion research: ignition, or a self-sustaining fusion reaction. That means the ultimate goal of a power plant that can replicate the sun and provide worry-free clean power remains a distant dream at this point.
"There are a large number of steps to be taken from where we are now, to having a power plant producing electrons on the grid," Andrew Klein, a professor of nuclear engineering at Oregon State University, told Foreign Policy.
Other nuclear experts are even more skeptical.
"This has no significance for energy. The whole fusion idea has been terribly oversold for many decades," Victor Gilinsky, a former member of the Nuclear Regulatory Commission, told FP.
Still, even if fusion-powered reactors are more in the realm of science fiction than a realistic piece of America's energy policy, the advances at the National Ignition Facility hold some real value: they could make it easier for scientists to more accurately test the U.S. nuclear weapons arsenal.
That's actually the primary mission of the ignition facility at Lawrence Livermore, and a real necessity, since physical testing of nuclear warheads is no longer allowed. The National Nuclear Security Administration, the part of the Energy Department responsible for nuclear weapons and naval reactors, told Congress in 2012 that it needs to have a better understanding of the physics inside thermonuclear explosions if it is to really be able to use computer models to test and maintain the U.S. nuclear deterrent.
The latest experiment solved one problem that has long dogged researchers: Getting actual results to match computer simulations of a fusion reaction. At the same time, researchers discovered evidence of "bootstrapping," where alpha particles thrown off by the implosion of the fuel contribute energy to the fusion reaction itself. That's important to make the fusion reaction self-sustaining.
"The experimental results have matched computer simulations much better than previous experiments, providing an important benchmark for the models used to predict the behavior of matter under conditions similar to those generated during a nuclear explosion," Lawrence Livermore said in a press release.
"This experiment represents an important milestone in the continuing demonstration that the [nuclear] stockpile can be kept safe, secure and reliable without a return to nuclear testing," the lab said.
Eduard Dewald - Lawrence Livermore National Laboratory