The U.S. Nuclear Fusion Breakthrough Is a Huge Milestone—But Unlimited Clean Energy Is Still Decades Off

In some ways, scientists at the Department of Energy’s National Ignition Facility (NIF) have been a bit down and out. The $3.5 billion facility was designed to replicate the atom-smashing reactions that occur inside the sun, a difficult process that requires enormous amounts of heat and pressure, and could theoretically solve humanity’s energy and climate woes.

But technical obstacles put NIF a decade behind in its goal of achieving fusion “ignition,” that is, getting more energy out of one of those reactions than it put in. The facility uses the largest lasers in the world to try and do that, focusing energy on a tiny capsule filled with hydrogen isotopes. But those lasers, based on 1980s technology, were in some ways already dated by the time they were installed, taking hours to cool down each time they are fired. And much of the team’s resources aren’t even devoted to achieving the holy grail of nuclear fusion, instead being focused on weapons research.

On Dec. 5—after decades of effort—scientists at the laboratory finally created a controlled fusion reaction that released more energy than the researchers blasted into it, an important step toward the long sought-after goal of generating almost unlimited power from clean, plentiful fusion energy. (Notably we have uncontrolled fusion reactions down pat—they’re the basis of hydrogen bombs). After bringing in an external team of scientists to confirm the findings, the U.S. Department of Energy (DOE) announced the development on Dec. 13. “This is a landmark achievement for the researchers and staff at the National Ignition Facility,” said Energy Secretary Jennifer Granholm in a press release. “This milestone will undoubtedly spark even more discovery.”

“We were not sure if it was ever going to work,” says Peter Littlewood, a physics professor at the University of Chicago and former director of Argonne National Lab, a DOE research center. “They deserve a tremendous amount of credit for slogging through this.”

Today’s news builds on a notable success achieved by the National Ignition Facility in August 2021, when it fired its lasers on a capsule of deuterium and tritium (hydrogen atoms with an extra one or two neutrons, respectively), setting off a reaction that unleashed 1.3 megajoules (MJ) of energy. It wasn’t as much as the 1.9 MJ that the lasers blasted into it, but it was still eight times more energy output than the facility’s previous record. Then, for months afterward, the NIF team failed to replicate the results. Whisperings started, with some physics community observers calling for the facility to finally be shut down. In July of this year, Nature reported that scientists at NIF had ceased trying to replicate their results from last year, and were instead focusing on a new strategy. It seems that focus has now paid off.

The NIF success also comes a few months after another successful fusion experiment in the U.K. Instead of lasers, scientists there used a donut-shaped tokamak, a machine that uses magnetic fields to heat hydrogen atoms to extraordinary temperatures in order to create a fusion reaction. Though that experiment didn’t reach the break-even point in terms of energy output, the results helped validate an approach being pursued by a multi-nation consortium building the larger $22 billion ITER (International Thermonuclear Experimental Reactor) tokamak project in France. That project, its designers claim, will create a reaction that outputs ten times more energy than researchers add in.

Scientists have been trying for decades to generate an output like the one achieved at the NIF, and the results are undoubtedly an important scientific and technical milestone. But tokamak technology is closer to potential commercialization than the NIF laser approach; Energy Department officials say that pursuing both methods is important to building up the science of nuclear fusion.

Fusion technology still faces an array of extremely difficult technical hurdles, and Littlewood says it will be decades before it could potentially be used to power homes and businesses, if it ever reaches that point at all. He terms the technology a “hail mary pass” to solve the climate crisis (fusion reactions produce no emissions, and wouldn’t have the meltdown risk or difficulties disposing of used fuel that plague nuclear fission reactors.) But the new experimental results don’t exactly mean that the technology will be coming any sooner, he says. “This isn’t really dancing in the streets. It’s more, ‘Phew, finally we got here.’”

It’s important also to keep in mind the amount of energy that researchers managed to generate. The result of the recent DOE experiment might be characterized as a small explosion, but the 3.15 MJ it outputted is equivalent to the energy content of about a tenth of a gallon of gasoline. Notably, the energy that the lasers input into the reaction, 2.05 MJ, is only a tiny share of the 300 MJ of energy the facility needed to run the experiment. “I don’t want to give you the sense that we’ll plug the NIF into the grid,” said Kim Budil, director of Lawrence Livermore National Laboratory, speaking in a press conference on Dec. 13. “That is definitely not how this works.”

The private sector has poured close to $5 billion dollars into commercializing fusion energy, with many companies trying out creative alternate approaches that are different from those being pursued by public research groups at NIF and ITER. Michl Binderbauer, CEO of commercial fusion company TAE Technologies, is much more optimistic about the timeline to potential commercialization than Littlewood—he says commercial fusion power plants could be coming in the next ten years.

“I think for humanity [the NIF experiment] should induce an enormous amount of confidence that we’re going to get there,” Binderbauer says. “It’s an enormous point of validation that we weren’t just chasing ghosts.”