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Scientists announce nuclear fusion breakthrough

JUANA SUMMERS, HOST:

This morning, scientists announced a breakthrough in the field of nuclear fusion. Fusion is the process that powers the sun. Scientists have been struggling for decades to make it work here on Earth. NPR's Geoff Brumfiel has this report on the breakthrough and what it could mean.

GEOFF BRUMFIEL, BYLINE: To give you a sense of just how long this took, listen to President Biden's science adviser, Arati Prabhakar. She remembers working on nuclear fusion in 1978.

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ARATI PRABHAKAR: You got to picture this. I'm wearing my bellbottoms. I've got long, black hair. And I show up, and I'm a 19-year-old kid, and they give me a laser to work on.

BRUMFIEL: Prabhakar was working at the Department of Energy's Lawrence Livermore National Laboratory. And the job was this - to try and use that laser to squish lightweight atoms of hydrogen together until they fused. It's a process known as nuclear fusion, and it can generate enormous amounts of power with no greenhouse gases. She worked on it for the summer, and then she left.

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PRABHAKAR: I went off and didn't do anything more about fusion, but the people I worked with and their successors kept going.

BRUMFIEL: And today, decades later, they announced they'd finally done it. The breakthrough came at Livermore's $3.5 billion National Ignition Facility. Mark Herrmann is the scientist in charge. He says there's been lots of setbacks and disappointments along the way, but the team never gave up.

MARK HERRMANN: Ultimately, that determination and grit is really what enabled this exciting success.

BRUMFIEL: Last week, researchers pointed to 192 laser beams at a tiny diamond sphere the size of a peppercorn. Inside was hydrogen fuel. The lasers went zap. The peppercorn imploded. And the fuel ignited in a fusion burn that released more energy than the lasers put in. They measure energy in something called megajoules, and this fusion made about 3.15 megajoules, which sounds cool, but it's not exactly that simple because lasers actually need a lot of juice from the electricity grid to work.

HERRMANN: The laser pulled more than 300 megajoules off the grid. And then the fusion energy that came out was, again, about 3 mega joules.

BRUMFIEL: In other words, the facility still used way more power overall than it produced. Ryan McBride is a nuclear engineer at the University of Michigan who wasn't involved in this breakthrough. He says today's milestone is important.

RYAN MCBRIDE: It is a big scientific step.

BRUMFIEL: But, he says, there are several more obstacles to making laser fusion work. To generate steady power would require lasers to zap multiple pellets every second.

MCBRIDE: So it'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 and then inject another one, have all the lasers hit it.

BRUMFIEL: Day after day for months and years. McBride says he doubts laser fusion could produce electrical power anytime soon.

MCBRIDE: It's many decades, as far as I can see.

BRUMFIEL: Meanwhile, the U.S. is seeking to cut its greenhouse gas emissions in half by 2030, a target that looks to be too close for fusion to help. Geoff Brumfiel, NPR News. Transcript provided by NPR, Copyright NPR.

Geoff Brumfiel works as a senior editor and correspondent on NPR's science desk. His editing duties include science and space, while his reporting focuses on the intersection of science and national security.
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