Energy

ARC reactor design uses superconducting magnets to draw fusion power closer

ARC reactor design uses superc...
A cutaway view of the proposed ARC reactor that could see commercially viable fusion power become a reality sooner rather than later
A cutaway view of the proposed ARC reactor that could see commercially viable fusion power become a reality sooner rather than later
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A cutaway view of the proposed ARC reactor that could see commercially viable fusion power become a reality sooner rather than later
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A cutaway view of the proposed ARC reactor that could see commercially viable fusion power become a reality sooner rather than later
MIT PhD candidate Brandon Sorbom holds REBCO superconducting tapes (left), which are the enabling technology behind the ARC reactor
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MIT PhD candidate Brandon Sorbom holds REBCO superconducting tapes (left), which are the enabling technology behind the ARC reactor

Fusion power can seem a bit like the last bus at night; it's always coming, but never arrives. MIT is working to change that with a new compact tokamak fusion reactor design based on the latest commercially available magnetic superconductor technology. The ARC (affordable, robust, compact) reactor design promises smaller, cheaper reactors that could make fusion power practical within 10 years.

A commercially viable fusion reactor has been the Holy Grail of engineering since the 1950s, with the potential to turn almost all other major electricity sources into an historical footnote overnight. If perfected, it would essentially be an inexhaustible source of power, impacting on almost every aspect of life, from the environment to global politics. The trick is making it practical.

Put simply, fusion involves placing hydrogen atoms under very high heat and pressure until they fuse into helium atoms, which releases tremendous amounts of energy. The Sun does this as a matter of course, but reproducing those conditions on Earth outside of a hydrogen bomb has proven difficult.

There are a number of fusion reactor designs, but one of the most promising is the tokamak reactor, which is a hollow metal chamber shaped like a donut twisted into a figure eight. Inside the chamber is a vacuum into which hydrogen isotopes deuterium and tritium are introduced. These are superheated to the temperature of the Sun's interior forming a plasma that is contained and compressed by powerful magnetic fields. The magnetic coils responsible for producing these magnetic fields are key to the whole process and the biggest bottleneck to progress.

An international consortium, including scientists from the European Union, India, Japan, China, Russia, South Korea, and the United States, is planing to build the world's most powerful fusion reactor based on a tokamak. Work began on the International Thermonuclear Experimental Reactor (ITER) in 1985, and at an estimated cost of US$40 billion, it isn't slated to start full operations until 2027. Even then, it will be on a purely experimental basis.

MIT PhD candidate Brandon Sorbom holds REBCO superconducting tapes (left), which are the enabling technology behind the ARC reactor
MIT PhD candidate Brandon Sorbom holds REBCO superconducting tapes (left), which are the enabling technology behind the ARC reactor

MIT's ARC reactor is an example of how a single change can completely alter the design of a system. It uses new commercially available superconductors made of rare-earth barium copper oxide (REBCO) superconducting tapes that are capable of producing high-magnetic field coils. The stronger magnetic fields generated by these coils do a better job of confining superhot plasma, so the reactor can be smaller, cheaper and take less time to build.

Intended for basic fusion power research, the ARC reactor is based on the same physics as ITER, though the team also describes it as a potential prototype plant that could generate significant amounts of power. According to MIT, the equations governing reactor design show that power output increases to the fourth power of the increase in the magnetic field. In other words, double the strength of the field and the power goes up 16 fold. The new superconductors being used by MIT should increase fusion power by a factor of 10 over standard superconducting technology, with knock-on effects for reactor design.

With a major radius of 3.3 m (10.8 ft) and a minor radius of 1.1 m (3.6 ft), the ARC is a 500 MW reactor that is half the diameter of ITER, but will boast a similar power output. Also, the new superconducting magnets will allow for a steady power output, while today's experimental reactors can only operate for a few seconds at a time before their copper coils overheat.

MIT has also designed the ARC reactor so that the fusion power core can be removed without needing to dismantle the reactor, which is a big plus for a research reactor. In addition, the solid cladding normally wrapped around the fusion chamber has been replaced with a circulating liquid. This eliminates the need to replace the cladding as it degrades, since the liquid can simply be replaced.

The researchers say the current design could generate three times more energy than is fed into it to keep it running, but they are hopeful of boosting this to five or six times in the future. Since no current fusion reactor can maintain even a sustained break even point, this would be a major breakthrough. The team says reactors like the ARC have been built in about five years, and that their design could generate electricity for about 100,000 people.

The team's results were published in Fusion Engineering and Design.

Source: MIT

13 comments
ColtJohnson
Finally energy source that doesn't pollute.. Hopefully this makes it to production and just doesn't disappear like some things have.
andyfreeze
Why does this read as a glossy ad? Just read the spin. Could be available in ten years? Oh come on now. Its an experimental reactor to be completed by 2027. At the bare minimum, it will be another twenty years before we see anything. In that time, we also have gen3 to come on song. Give me a break, they have been working on fussion since the 1950's and no gen 3 s are anywhere near service ready. This is all interesting but it is research premissed on a vacuum of alternatives. Just read the yearly report on the nuclear industry and it doesnt look pretty.
Rann Xeroxx
I really think this is the future of power and electric cars the future of transportation. Its not a matter of "if" really.
Jeff Goldstein
This article is very confused. It never really says how long it will take to build a test reactor using this technology. It mentions 5 years but reads as if no one proof read that paragraph. If they are saying 5 years. Why so long and how much will it cost? It does clearly make it sound like it is a total waste to spend time, effort and money on the existing ITER program.
Nostromo47
Didn't Lockheed/Martin have a compact fusion reactor in the works at the Palmdale, California Skunkworks? Last I heard in 2014, they were just months away from having a working prototype that could fit in a Winnebago. Comparisons to Walter Heisenberg White and Breaking Bad are too tempting!
corgidaddy
Someone hasn't told these students and professors that this isn't possible. I appreciate the efforts of Rann Xeroxx, to tell us this. Rann should really be writing to the students and professors at MIT and the University of Washington (they are working on something like this), and Lockheed Martin. It may be too late already for Rann. More and more students and professors and research scientists are becoming confident about this. Rann should have worked towards a doctorate in nuclear physics and another in electrical engineering so that his protests could be more effective.
nicho
"affordable, robust, compact" ... Or someone really wanted to call it an ARC reactor.
michael_dowling
Sounds promising if what they say about conventional magnetic coils having to be shut down to prevent overheating is the reason for stopping the reaction.If they can maintain field intensity indefinitely,that would be a major advance.
Fast Eddie
In my lifetime, fusion power has always been 50 years in the future...and it still is. Terrestrial containment systems seem close enough to impossible that I think we should wind down the costly research...and put the money into other systems. I am not opposed to thermonuclear power. In fact, my preferred thermonuclear concept is simple: procure or find a ball of hydrogen gas so large that it compresses itself to fusion ignition. Then, because such as gas ball is going to be large...and very hot...place it far in space, say, 93 million miles away from the Earth. Extracting the endlessly flowing energy from this thermonuclear reactor would require large photovoltaic panels across the Earth, but that should be very feasible. Why do I have to come up with all the good ideas myself?!
Gannet
" the potential to turn almost all other major electricity sources into an historical footnote overnight." Yeah. In 25 odd years time when my solar panels might need replacing, I'll see how well they are doing with fusion. Given that solar PV is still getting better and cheaper ... I wonder when they will give up trying stuff like this.