US Department of Energy officials announced a history-making accomplishment in nuclear fusion Tuesday: For the first time, US scientists produced more energy from fusion than the laser energy they used to power the experiment.
A so-called "net energy gain" is a major milestone in a decadeslong attempt to source clean, limitless energy from nuclear fusion -- the reaction that happens when two or more atoms are fused together.
The experiment put in 2.05 megajoules of energy to the target and resulted in 3.15 megajoules of fusion energy output -- generating more than 50% more energy than was put in. It's the first time an experiment resulted in a meaningful gain of energy.
"This monumental scientific breakthrough is a milestone for the future of clean energy," said Democratic US Sen. Alex Padilla of California in a statement.
The breakthrough was made by a team of scientists at the Lawrence Livermore National Laboratory's National Ignition Facility in California on December 5 -- a facility the size of a sports stadium and equipped with 192 lasers.
Energy Secretary Jennifer Granholm on Tuesday called the breakthrough a "milestone."
"Ignition allows us to replicate, for the first time, certain conditions that are only found in the stars and sun," Granholm said. "This milestone moves us one significant step closer to the possibility of zero-carbon, abundant fusion energy powering our society."
Granholm said scientists at Livermore and other national labs do work that will help the US move quickly toward clean energy and maintain a nuclear deterrent without nuclear testing.
"This is what it looks like for America to lead, and we're just getting started," Granholm said. "If we can advance fusion energy, we could use it to produce clean electricity, transportation fuels, power, heavy industry and so much more."
Arati Prabhakar, director of the White House Office of Science and Technology Policy, spoke about how, as a young scientist early on in her career, she spent three months at Lawrence Livermore working on its nuclear fusion project.
Prabhakar reflected on the generations of scientists who got to today's achievement with nuclear fusion. "It took not just one generation but generations of people pursuing this goal," she said. "It's a century since we figured out it was fusion that was going on in our sun and all the other stars. In that century it took so many different kinds of advances that ultimately came together to the point that we could replicate that fusion activity in a laboratory."
Why a net gain in energy matters
We are still a very long way from having nuclear fusion power the electric grid, never mind one power plant itself. The US project, while groundbreaking, only produced enough energy to boil about 2.5 gallons of water, Tony Roulstone, a fusion expert from the University of Cambridge's Department of Engineering told CNN.
That may not seem like much, but the experiment is still hugely significant because scientists demonstrated that they can actually create more energy than they started with. While there's many more steps until this can be commercially viable, that is a major hurdle to cross with nuclear fusion, experts say.
"This is very important because from an energy perspective, it can't be an energy source if you're not getting out more energy than you're putting in," Julio Friedmann, chief scientist at Carbon Direct and a former chief energy technologist a Livermore, told CNN on Monday. "Prior breakthroughs have been important, but it's not the same thing as generating energy that could one day be used on a larger scale."
Past fusion experiments including one in the United Kingdom have generated more energy, but have not had nearly as big of an energy gain. For instance, earlier this year, UK scientists generated a record-setting 59 megajoules of energy -- about 20 times as much as the US-based project. Even so, the UK project only showed an energy gain of less than one megajoule.
There's still many years and a long way to go to make the project commercially viable. Neither the US or UK-based projects "have the hardware and steps in place to convert fusion neutrons to electricity," Anne White, head of MIT's Department of Nuclear Science and Engineering, told CNN.
But Roulstone pointed out that big ambitious nuclear energy projects must start somewhere: In 1942, scientists in Chicago ran the first fission nuclear reactor for just 5 minutes in its first run; 15 years later, the first US-based nuclear power plant went online in Pennsylvania.
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