The U.S. fusion energy breakthrough: Everything you need to know

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On Tuesday, the Department of Energy is expected to announce a long-awaited milestone in the development of nuclear fusion power: net energy gain. The news, first reported by the FinancialTimes and confirmed by The Washington Postcould galvanize the fusion community, which has long touted the technology as a possible clean-energy tool to fight climate change.

But how important is the “net energy gain” anyway – and what does it mean for the fusion power plants of the future? Here’s what you need to know.

Existing nuclear power plants operate using fission — separate heavy atoms to create energy. In fission, a neutron collides with a heavy uranium atom, splitting it into lighter atoms and releasing a lot of heat and energy at the same time.

Fusion, on the other hand, works in the opposite direction – it involves smashing two atoms (often two hydrogen atoms) together to create a new element (often helium), the same way stars create energy. In this process, the two hydrogen atoms lose a small amount of mass, which is converted into energy according to Einstein’s famous equation, E=mc². Because the speed of light is very, very fast – 300,000,000 meters per second – even a tiny amount of lost mass can result in a ton of energy.

What is “net energy gain” and how did researchers arrive at it?

So far, researchers have successfully fused two hydrogen atoms, but it still takes more energy to do the reaction than they get back. Net energy gain – where they get back more energy than they put in to create the reaction – has been the elusive holy grail of fusion research.

Now, researchers at the National Ignition Facility at Lawrence Livermore National Laboratory in California are set to announce that they have achieved a net energy gain by firing lasers at hydrogen atoms. The 192 laser beams compress hydrogen atoms to about 100 times the density of lead and heat them to about 100 million degrees Celsius. The high density and high temperature cause the atoms to fuse into helium.

Other methods being investigated involve the use of magnets to confine the super hot plasma.

“If this is what we expect, it’s like the Kitty Hawk moment for the Wright brothers,” said Melanie Windridge, plasma physicist and CEO of Fusion Energy Insights. “It’s like the plane is taking off.

Does that mean Fusion Power is ready for prime time?

No. Scientists call the current breakthrough a “scientific net energy gain” – meaning more energy came out of the reaction than was contributed by the laser. This is a milestone that has never been reached before.

But this is only a net energy gain at the micro level. The lasers used at Livermore’s lab are only about 1% efficient, according to Troy Carter, a plasma physicist at the University of California, Los Angeles. This means that it takes about 100 times more energy to operate the lasers than they are ultimately able to supply to the hydrogen atoms.

Researchers will therefore still have to reach the “net engineering energy gain”, or the point at which the whole process takes less energy than is produced by the reaction. They will also need to understand how to transform the energy produced – currently in the form of kinetic energy from the helium nucleus and the neutron – into a usable form for electricity. They could do this by converting it to heat and then heating steam to spin a turbine and run a generator. This process also has efficiency limitations.

All of this means that the energy gain will likely have to be pushed much, much higher for fusion to be truly commercially viable.

At the moment, researchers can also only perform the fusion reaction about once a day. In the meantime, they must allow the lasers to cool down and replace the fusion fuel target. A commercially viable plant should be able to do this multiple times per second, says Dennis Whyte, director of MIT’s Plasma Science and Fusion Center. “Once you have the scientific viability,” he said, “you have to determine the technical viability.”

What are the benefits of merging?

The possibilities of Fusion are enormous. The technology is much, much safer than nuclear fission, because fusion cannot create runaway reactions. It also does not produce radioactive by-products that must be stored, or harmful carbon emissions; it just produces inert helium and a neutron. And we are unlikely to run out of fuel: the fuel for fusion consists only of heavy hydrogen atoms, which can be found in seawater.

When could fusion actually power our homes?

That’s the trillion dollar question. For decades, scientists have joked that fusion is still 30 or 40 years away; Over the years, researchers have variously predicted that fusion plants would be operational in the 1990s, 2000s, 2010s, and 2020s. Current fusion experts say this is not a a matter of time, but a matter of will – if governments and private donors fund fusion aggressively, they say, a prototype fusion power plant could be available in the 2030s.

“The timing isn’t really about time,” Carter said. “It’s a question of innovation and effort.

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