For the past 20 years, MIT's Plasma Science and Fusion Center (PSFC) has been experimenting with nuclear fusion through the world's smallest tokamak-type (doughnut-shaped) nuclear fusion device -- the Alcator C-Mod.
The goal? To produce the world's smallest fusion reactor -- one that crushes a doughnut-shaped fusion reaction into a 3.3 meter radius -- three of which could power a city the size of Boston.
And MIT researchers are getting close to their goal, despite a recent cut in federal funding that could slow their progress.
The lessons already learned from MIT's smaller Alcator C-Mod fusion device have enabled researchers, including MIT Ph.D candidate Brandon Sorbom and PSFC Director Dennis Whyte, to develop the conceptual ARC (affordable, robust, compact) reactor.
"We wanted to produce something that could produce power, but be as small as possible," Sorbom said.
A working ARC fusion reactor would use 50 megawatts (MW) of power to produce 500MW of fusion power, 200MW of which could be delivered to the grid. That's enough to provide 200,000 homes with electricity.
While three other fusion devices roughly the same size as the ARC have been built over the past 35 years, they didn't produce anywhere near its power. What also sets MIT's reactor apart is its superconductor technology, which would enable it to create 50 times the power it actually draws. (MIT's PSFC last year published a paper on the prototype ARC reactor in the peer reviewed journal ScienceDirect.)
The ARC reactor's powerful magnets are modular, meaning they can be easily removed and the central vacuum vessel in which the fusion reaction occurs can be replaced quickly; besides allowing upgrades, a removable vessel means a single device could be used to test many vacuum vessel designs.
Fusion reactors work by super heating hydrogen gas in a vacuum, the fusing of hydrogen atoms form helium. Just as with splitting atoms in today's fission nuclear reactors, fusion releases energy. The challenge with fusion has been confining the plasma (electrically charged gas) while heating it with microwaves to temperatures hotter than the Sun.
The result of successfully building an ARC reactor would be a plentiful source of clean and reliable power, because the needed fuel -- hydrogen isotopes -- is in unlimited supply on Earth.
"What we've done is establish the scientific basis...for, in fact, showing there's a viable pathway forward in the science of the containment of this plasma to make net fusion energy -- eventually," Whyte said.
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