< U.S. reaches a fusion power milestone. Will it be enough to save the planet?

ROB SCHMITZ, HOST:

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

A MARTÍNEZ, HOST:

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.

SCHMITZ: Wow.

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.

SCHMITZ: OK.

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.

SCHMITZ: OK.

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.

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