U.S. lab says it repeated fusion energy feat — with higher yield

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A group of U.S. scientists say they have repeated their landmark energy feat — a nuclear fusion reaction that produces more energy than is put into it. But this time, they say the experiment produced an even higher energy yield than one in December that got international attention for making a major step forward toward the long elusive goal of producing energy through fusion.

This second achievement by researchers at the federal Lawrence Livermore National Laboratory in California is another crucial step — albeit in a journey that may still take decades to complete — in the quest for an unlimited source of cheap and clean power. The successful effort was initially reported by the Financial Times on Sunday.

“We have continued to perform experiments to study this exciting new scientific regime. In an experiment conducted on July 30, we repeated ignition at (the National Ignition Facility),” Paul Rhien, a spokesman for the federal laboratory, said in a emailed statement. “Analysis of those results is underway, but we can confirm the experiment produced a higher yield than the December test.”

Rhien said the lab “won’t be discussing further details” of the July experiment until after more analysis. But the team plans to “share the results at scientific conferences and peer-reviewed publications as part of our normal process for communicating scientific results.”

Scientists produced the world's first fusion reaction with net energy gain — a major milestone in the decades-long quest for unlimited, cheap, clean power. (Video: Brian Monroe, Drea Cornejo, Austin Meyers/The Washington Post)

Right now, nuclear power plants use fission, which creates energy by splitting atoms — the science at the center of the blockbuster “Oppenheimer.” While nuclear power produces bountiful clean energy, it has long drawn concerns over safety, though it is getting renewed attention amid an international push to reduce greenhouse gas emissions and slow global warming.

Fusion, on the other hand, creates energy by merging atoms together. It’s long been a dream because it could create limitless clean energy without the radioactive byproducts of nuclear power or the risk of meltdown. Plus, the fuel to make fusion happen is simply heavy hydrogen atoms, which can be found in something that Earth has in abundance: seawater. No mining of uranium is required.

Researchers have produced fusion reactions before, but it has taken more energy to cause the reaction than they could get back. The key thing about these last two experiments is that they get more energy back than they put in to create the reaction. That efficiency has been the elusive holy grail of fusion research.

The White House praised the work at the time of the first breakthrough in December.

“This is such a wonderful example of a possibility realized, a scientific milestone achieved and a road ahead to the possibilities for clean energy,” Arati Prabhakar, the White House science adviser, said during a news conference.

Still, scientists are far away from using the energy produced by fusion.

Researchers can only create a fusion reaction about once a day because they have to let the lasers cool and replace the fuel target. But a commercially viable fusion plant would need to be able to do it several times per second, Dennis Whyte, director of the Plasma Science and Fusion Center at MIT, previously told The Washington Post.

“Once you’ve got scientific viability,” he said, “you’ve got to figure out engineering viability.”