For the first time ever, physicists have set off a controlled nuclear fusion reaction that released more energy than what was put into the experiment.
The milestone laser shot took place on Dec. 5 at the U.S. Department of Energy’s National Ignition Facility at Lawrence Livermore National Laboratory in California. The fact that there was a net energy gain qualified the shot, in technical terms, as ignition. “Reaching ignition in a controlled fusion experiment is an achievement that has come after more than 60 years of global research, development, engineering and experimentation,” said Jill Hruby, under secretary of energy for nuclear security and the administrator of the National Nuclear Security Administration.
However, officials acknowledged that it’s still likely to be decades before commercial fusion power becomes a reality. They said the most immediate impact of the breakthrough will be felt in the field of national security and the stewardship of America’s nuclear weapons stockpile.
If nuclear fusion power can be harnessed, that could open up a new era of cleaner, more abundant energy. One of the potential fuels for fusion is deuterium, an isotope of hydrogen that can be extracted from seawater.
Fusion takes advantage of the same reaction that lights up the sun. Unlike nuclear fission, which involves the decay of heavy radioactive elements, fusion smashes together lighter elements so forcefully that some of the mass of the fuel is converted into energy in line with Albert Einstein’s famous E=mc2 equation.
Researchers around the world have been working to maximize the efficiency of fusion reactions in the lab. The biggest project is the international ITER experiment in France, which will use a giant magnetic confinement device known as a tokamak. The National Ignition Facility uses a different approach, which focuses a blast from 192 high-powered lasers on a tiny capsule containing a deuterium-tritium target that’s smaller than a BB pellet.
The NIF team has been trying to achieve ignition for years, but it’s been devilishly difficult to craft the target pellet and the geometry of the laser blast to produce the pressures and temperatures required for fusion. Mark Herrmann, program director for weapon physics and design at the Livermore Lab, compared the effort to a race between heating up the target and losing that heat due to tiny defects in the design.
“For many, many decades, we lost the race,” Herrmann said.
Thanks in part to machine learning tools, the design was improved over the past few months. At 1:03 a.m. PT Dec. 5, a laser shot put 2.05 megajoules of energy into the experiment — and got back 3.15 megajoules of neutron-producing fusion energy. “A gain of 1.5,” said Marv Adams, NNSA’s deputy administrator for defense programs.
Tammy Ma, who leads Livermore Lab’s Inertial Fusion Energy Institutional Initiative, said she “burst into tears” when she heard about the successful shot.
Energy Secretary Jennifer Granholm said the achievement would “go down in the history books.”
“This milestone moves us one significant step closer to abundant carbon-free energy powering our society,” she said.
The wider fusion research community also hailed the breakthrough. “Today’s announcement shows the world that fusion is not science fiction: It will soon be a viable source of energy,” Andrew Holland, CEO of the Fusion Industry Association, said in a news release. “There are still many steps between these experimental results and fusion power plants, but this is an important milestone for fusion.”
David Kirtley — the CEO of Helion Energy, a commercial fusion company based in Everett, Wash. — said achieving ignition is “a really big deal for fusion science.”
“Even though at the National Ignition Facility, they were not focused on commercial energy, at Helion we believe this paves the way for private business to now focus and turn up the speed on getting commercial energy to the grid,” Kirtley said.
The researchers behind the experiment didn’t downplay the challenges. Although the laser shot itself registered a net energy gain, Livermore Lab director Kim Budil pointed out that the total electrical energy required “from the wall” to support the experiment was 300 megajoules — roughly 100 times the amount of fusion energy produced.
“Our calculation suggests that it’s possible with a laser system at scale to achieve hundreds of megajoules of yield, so there is a pathway to a target that produces enough yield,” Budil said. “But we’re very distant from that right now.”
Moreover, the National Ignition Facility is designed to do a laser shot only about once a day, but a power plant would have to produce energy continuously. (And for what it’s worth, one kilowatt-hour of energy is equivalent to 3.6 megajoules.)
“A few decades of research on the underlying technologies could put us in a position to build a power plant,” Budil said.
Michael Mann, a climate scientist at the University of Pennsylvania, cautioned against getting too excited about today’s announcement. “I’d be more excited about an announcement that U.S. is ending fossil fuel subsidies,” Mann said in a series of tweets. “That doesn’t mean it isn’t good news, but it does mean that it won’t play a significant role in decarbonizing our economy by 50% this decade, which is necessary to avert catastrophic >1.5C (3F) warming.”
Focusing on existing sources of renewable energy and improving technologies for energy storage, efficiency and conservation are more realistic strategies for dealing with the climate challenge over the next decade, Mann said.
In addition to advancing the cause of clean energy, ignition contributes to NNSA’s national security mission, Adams said.
“First, it will lead to laboratory experiments that help NNSA defense programs continue to maintain confidence in our deterrent without nuclear explosive testing,” Adams said. “Second, it underpins the credibility of our deterrent by demonstrating world-leading expertise in weapons-relevant technologies. That is, we know what we’re doing.”
Helion Energy’s Kirtley, who conducted research into plasma propulsion systems before turning his focus to commercial fusion power, said the breakthrough could have off-Earth implications as well.
“Interestingly, I think this is even more applicable for space propulsion applications of fusion than it is for commercial electricity generation,” he said. “The pulsed inertial method that the National Ignition Facility is doing is a high-gain ignition type of system for electricity generation. Helion is focused on really efficient small-scale generators, but in space, the inertial application at high gain and high energy yield is really one of the key goals.”
Michael Eades, chief engineer for Seattle-based Ultra Safe Nuclear Technologies, said nuclear pulse propulsion is farther off than the systems that are the focus of his company’s research. Nevertheless, he said achieving ignition is a welcome development. “We’re excited by the news of the gain in energy, and we see it as enabling far future missions — maybe beyond the solar system,” Eades said.