Updated December 13, 2022 at 9:59 AM ET

Scientists with the U.S. Department of Energy have reached a breakthrough in nuclear fusion.

For the first time ever in a laboratory, researchers were able to generate more energy from fusion reactions than they used to start the process. The total gain was around 150%.

"America has achieved a tremendous scientific breakthrough," Energy Secretary Jennifer Granholm said at a press conference.

The achievement came at the National Ignition Facility (NIF), a $3.5 billion laser complex at Lawrence Livermore National Laboratory in California. For more than a decade, NIF has struggled to meet its stated goal of producing a fusion reaction that generates more energy than it consumes.

But that changed in the dead of night on Dec. 5. At 1 AM local time, researchers used laser beams to zap a tiny pellet of hydrogen fuel. The lasers produced 2.05 megajoules of energy, and the pellet released roughly 3.15 megajoules.

It's a major milestone, one that the field of fusion science has struggled to reach for more than half a century.

"In our laboratory we've been working on this for almost 60 years," says Mark Herrmann, who oversees the NIF program at Livermore. "This is an incredible team accomplishment."

Researchers say that fusion energy could one day provide clean, safe electricity without greenhouse gas emissions. But even with this announcement, independent scientists believe that dream remains many decades away.

Unless there's an even larger breakthrough, fusion is unlikely to play a major role in power production before the 2060s or 2070s, says Tony Roulstone, a nuclear engineer at Cambridge University in the U.K., who's done an economic analysis of fusion power.

"I think the science is great," Roulstone says of the breakthrough. But many engineering obstacles remain. "We don't really know what the power plant would look like."

At that rate, fusion power won't come soon enough for the Biden administration, which is seeking to bring America's net greenhouse gas emissions to zero by 2050 — a goal that experts say must be met to avoid the worst effects of climate change.

Laser power

Fusion power has long fired the imaginations of nuclear scientists and engineers. The technology would work by "fusing" light elements of hydrogen into helium, generating an enormous amount of energy. It's the same process that powers the sun, and it's far more efficient than current nuclear "fission" technology. What's more, fusion power plants would generate relatively little nuclear waste, and they could run off of hydrogen readily found in seawater.

The ten-story-tall NIF facility is the world's most powerful laser system. It is designed to aim 192 beams onto a tiny cylinder of gold and depleted uranium. Inside the cylinder is a diamond capsule smaller than a peppercorn. That capsule is where the magic happens — it's filled with two isotopes of hydrogen that can fuse together to release astonishing amounts of energy.

When the lasers are fired at the target, they generate x-rays that vaporize the diamond in a tiny fraction of a second. The shockwave from the diamond's destruction crushes the hydrogen atoms, causing them to fuse and release energy.

NIF first opened in 2009, but its initial laser shots fell well short of expectations. The hydrogen in the target was failing to "ignite", and the Department of Energy had little to show for the billions it had invested.

Then in August 2021, after years of slow but steady progress, physicists were able to ignite the hydrogen inside the capsule, creating a self-sustaining burn. The process is analogous to lighting gasoline, says Riccardo Betti, the chief scientist of the laboratory for laser energetics at the University of Rochester. "You start with a little spark, and then the spark gets bigger and bigger and bigger, and then the burn propagates through."

Bang in a box

This self-burning ignition actually resembles a process similar to that of a modern thermonuclear warhead, albeit on a much smaller scale.

The United States has not tested a nuclear weapon since 1992, and the primary purpose of the NIF facility is to conduct very small-scale bangs that closely mimic nukes. The data from these tiny explosions are fed into complex computer simulations that help physicists understand whether the nation's nuclear weapons remain reliable, despite decades on the shelf.

"We use these experiments to get experimental data to compare to our simulations," says Herrmann, who also oversees nuclear weapons research at the lab. In addition, he says the radiation from the explosions can be used to test components. Such tests will make sure that new and refurbished parts of nuclear weapons behave as expected.

More out than in

Even after last-year's achievement, there was still one more goal to reach – producing more power from the tiny capsule than the lasers put in.

Herrmann says that the August 2021 shot gave the team a starting point. "That put us on the threshold," he says. "We actually made a lot of progress in the last year." Steady improvements in the lasers, targets, and other components gradually put the facility in a position where it could finally generate energy from the capsule.

"It is a big scientific step," says Ryan McBride, a nuclear engineer at the University of Michigan. But, McBride adds, that does not mean that NIF itself is producing power. For one thing, he says, the lasers require more than 300 megajoules worth of electricity to produce around 2 megajoules of ultraviolet laser light. In other words, even if the energy from the fusion reactions exceeds the energy from the lasers, it's still only around one percent of the total energy used.

Moreover, it would take many capsules exploding over and over to produce enough energy to feed the power grid. "You'd have to do this many, many times a second," McBride says. NIF can currently do around one laser "shot" a week.

Still, the long-term potential is staggering, says Arati Dasgupta, a nuclear scientist with the U.S. Naval Research Laboratory. Whereas a giant pile of carbon-spewing coal might generate electricity for a matter of minutes, the same quantity of fusion fuel could run a power plant for years–with no carbon dioxide emissions. "This is a great demonstration of the possibility," Dasgupta says. But, she adds, many technical issues remain. "It's a huge undertaking."

And getting economical power out of a fusion reactor is even tougher, says Roulstone. He and his team looked at a rival technology known as a tokamak and concluded that there were still an enormous number of challenges to making fusion work economically. His analysis estimated that fusion won't be ready for the grid before the second half of this century. He believes the same timeline holds for NIF's technology. "It's not very easy to see how you scale this into a power reactor quickly," he says.

By then most climate experts believe the world will have to have already made drastic cuts to carbon emissions to avoid the worst effects of climate change. To limit warming to 2.7 degrees Fahrenheit by the end of the century, the world must nearly halve its carbon output by 2030 — a far shorter timescale than what's needed to develop fusion.

Betti agrees that the timeline to building a fusion plant is "definitely decades". But, he adds, that could change. "There's always a possibility of breakthrough," he says. And the new NIF results could help spur that breakthrough forward. "You're going to get more people to look into this form of fusion, to see whether we can turn it into an energy-making system."

Copyright 2022 NPR. To see more, visit https://www.npr.org.



This morning, U.S. scientists are announcing a big advance in nuclear fusion.


Now, that's the process that powers our sun. And if - if - it could be brought to Earth, it would mean nearly limitless clean energy.

SCHMITZ: Joining us now is NPR science correspondent Geoff Brumfiel. Good morning, Geoff.

GEOFF BRUMFIEL, BYLINE: Good morning, Rob.

SCHMITZ: So, Geoff, break down this breakthrough for us.

BRUMFIEL: Right. So last week at the Lawrence Livermore National Laboratory in California, scientists did something they've never done in a laboratory setting before. They got more energy out of a nuclear fusion reaction than they put into it.


BRUMFIEL: And there are some caveats. We'll get to those caveats in a minute. But this is a big deal because nuclear fusion is very hard to make happen on Earth. Basically, fusion is the process of sticking lightweight atoms together. When they fuse, when they glom together, they release a ton of energy. But getting them to stick is really tough.

SCHMITZ: This is very exciting. How did they do this?

BRUMFIEL: With lasers. It's like the...

SCHMITZ: Lasers.

BRUMFIEL: ...Classic science - pew-pew-pew (ph) laser science. They have this multi-billion dollar facility called the National Ignition Facility. It's pretty much the most powerful laser on Earth. And basically, all these laser beams are pointed at one teeny, tiny target made of gold and depleted uranium. Inside that target is an even tinier sphere of diamond - about the size of a peppercorn. And inside that are different isotopes of hydrogen. So basically 192 laser beams go in. The energy squeezes all that hydrogen together until it ignites and burns, kind of like the head of a match. But this is a real brute-force approach to making nuclear fusion happen.

SCHMITZ: This is fascinating. How much power did that produce?

BRUMFIEL: Well, here's the sort of caveat part. It wasn't all that much.


BRUMFIEL: So the experiment did generate more power out than the lasers put in, but the lasers themselves require a ton of electricity to operate. So actually, they still ended up using a lot more power than they got out the other end. And this is just sort of the start of the problem with this whole laser approach.


BRUMFIEL: I spoke to Ryan McBride, a nuclear engineer at the University of Michigan, and he said if you wanted to make electricity, you'd need to zap several of these diamond targets every second.

RYAN MCBRIDE: So that's like (vocalizing). You know, that's a lot of pulsing. There's a debris field left as these things are blasted. And you'd have to, like, clear that debris, inject another one, have all the lasers hit it.

BRUMFIEL: And you have to do that over and over for days and months and years. And at the moment, they can only zap a target once a week. So power is a long way off.

SCHMITZ: OK. Does this have any other uses?

BRUMFIEL: Yeah, it turns out the exploding target is actually like a thermonuclear weapon. And, in fact, the main job of the National Ignition Facility, or NIF, as it's known, is to make sure our aging nuclear weapons still work.

MCBRIDE: We no longer test nuclear weapons. And so they've built machines like NIF as surrogates to doing actual tests since we haven't tested since 1992.

BRUMFIEL: And so this is a big deal for that side of things as well because it means that weapons physicists can make sure their calculations are correct.

SCHMITZ: So bottom line, Geoff - this sounds huge, like Thomas Edison lightbulb huge. But maybe it's not going to change the world just yet.

BRUMFIEL: Yeah, it's a big step forward. But the scientists I spoke to said fusion energy remains decades away. And to put things in perspective, the U.S. has tried to cut its carbon emissions in half by 2030, which is only a few years away. So I don't think this is going to solve the climate crisis. But on the bright side, it does show that humans are good at solving tough problems. So maybe don't count us out just yet.

SCHMITZ: NPR's Geoff Brumfiel. Thanks, Geoff.

BRUMFIEL: Thank you, Rob. Transcript provided by NPR, Copyright NPR.

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