Reactor could finally deliver fusion power
It’s a dream that physicists have pursued for the better part of a century. Fusion power, a clean-burning, safe form of nuclear energy that mimics the sun. Like a miniature sun, it would have the capacity to produce heat for millions of years. For so long, it’s been just a dream. But researchers at MIT and Commonwealth Fusion Systems think they’re on the right track to making it a reality.
SPARC (soonest/smallest private-funded affordable robust compactor), as the project is known, is not the only fusion reactor in the works. In July, engineers in France began construction on ITER (international thermonuclear experimental reactor), a collaboration among 35 countries that is scheduled to begin operations in 2035. Both reactors will use giant magnetic devices known as tokamaks to keep the explosive elements reacting within the confines of the reactor.
A major difference between the two is that ITER is the world’s largest fusion project, while SPARC is deliberately many times smaller. SPARC’s high-temperature superconducting magnets will be about three times smaller in diameter than ITER’s even as they deliver up to 21 teslas of magnetic field strength compared to the 12 teslas ITER will max out at. This will enable SPARC to be only a few feet wide, many times smaller than ITER. “That dramatic reduction in size is accompanied by a reduction in weight and cost,” MIT Plasma Science and Fusion Center deputy director Martin Greenwald told LiveScience. “That’s really the game-changer.”
SPARC is different in another significant way; it would be a “burning plasma” reactor, fusing hydrogen isotopes into helium. With no more energy input required, the reaction would be self-sustaining and theoretically go on for millions of years. This is quite similar to how the sun generates energy, but such power has never been harnessed here on Earth.
Assuming SPARC works—the Journal of Plasma Physics recently published seven papers containing contributions from 47 scientists at 12 institutions that Greenwald told the New York Times confirm “the design we’re working on is very likely to work”—it could provide the blueprint for fusion power plants with little to no greenhouse gas emissions.
“Fusion power plants could be one-to-one replacements for fossil fuel plants, and you wouldn’t have to restructure electrical grids for them,” Greenwald said. Currently available renewables such as wind and solar energy “are not accommodated well by the current design of electric grids.”
Just how powerful SPARC can be remains to be seen. The researchers are targeting anywhere from 250 to 1,000 megawatts for fusion power plants based on SPARC. Typical power plants in the US generate 100 to 500 MW. ITER should generate about 500.
It’s also important to note how much energy the reactor will put out compared to how much goes in to start the reaction. This ratio is known as a Q factor. No fusion plasma has ever produced a positive Q factor. It’s always consumed more energy than it releases. But the analyses of SPARC indicate that it will at minimum have a Q factor or 2 and could go as high as 10 or even more. ITER is also designed to have a Q factor of 10 for long pulses of 400 to 600 seconds.
ITER is set to begin experiments in 2025, taking about 10 years to get up to its full power configuration. Construction on SPARC should take three or four years, with electricity generation beginning in 2035. Both projects will be tinkering with their reactions and machinery in the meantime to perfect the reactors. So it will be still be some years before we know if we’re capable of large-scale fusion power, but we’re definitely closer than ever before. The future is bright.
“We haven’t run into anything where we say, ‘Oh, this is predicting that we won’t get to where we want,’” Greenwald said. “We believe it’s going to work.”
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