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MIT takes a page from Tony Stark, edges closer to an ARC fusion reactor

Lucas Mearian | Feb. 4, 2016
Fusion reactors, like the one used by Marvel's 'Iron Man', would provide a source of clean, sustainable energy for the world

The reactors would also use less energy to operate than fission reactors.

While MIT's current Alcator C-Mod produces no electricity, it demonstrates the effects of a magnetic containment field on super-heated plasma, and by hot we're talking about 100 million degrees Fahrenheit. By comparison, our Sun is a chilly 27 million degrees Fahrenheit.

Far from being dangerous, the 100-million-degree plasma instantly cools and resumes a gaseous state when it touches the inner sides of the reactor. That's why a powerful magnetic containment field is needed.

Just like a fission nuclear reactor, a fusion reactor would essentially be a steam engine. The heat from the controlled fusion reaction is used to turn a steam turbine that, in turn, drives electrical generators.

MIT's current C-Mod fusion device uses plentiful deuterium as its plasma fuel. Deuterium is a hydrogen isotope that is not radioactive and can be extracted from seawater.

In order to create a conceptual ARC reactor, however, a second hydrogen isotope is needed: tritium. That's because the rate at which deuterium-deuterium isotopes fuse is about 200 times less than the rate at which deuterium-tritium isotopes fuse.

Tritium, while radioactive, only has a half-life of about 10 years. Although tritium does not occur naturally, it can be created by bombarding lithium with neutrons. As a result,  it can be easily produced as a sustainable source of fuel.

With fusion reactors, smaller is better

While MIT's reactor might not fit conveniently into Tony Stark's chest (that is a movie after all), it would be the smallest fusion reactor with the most powerful magnetic containment chamber on earth. It would produce the power of eight Teslas or about two MRI machines.

By comparison, in southern France, seven nations (including the U.S.) have collaborated to build the world's largest fusion reactor, the International Thermonuclear Experimental Reactor (ITER) Tokamak. The ITER fusion chamber has a fusion radius of 6.5 meters and its superconducting magnets would produce 11.8 Teslas of force.

However, the ITER reactor is about twice the size of ARC and weighs 3,400 tons -- 16 times as heavy as any previously manufactured fusion vessel. The D-shaped reactor will be between 11 meters and 17 meters in size and have a tokamak plasma radius of 6.2 meters, almost twice the ARC's 3.3-meter-radius.

The concept for the ITER project began in 1985, and construction began in 2013. It has an estimated price tag of between $14 billion and $20 billion. Whyte, however, believes ITER will end up being vastly more expensive, $40 billion to $50 billion, based on "the fact that the U.S. contribution" is $4 billion to $5 billion, "and we are 9% partners."

 

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