It’s an old joke that many fusion scientists have grown tired of hearing: Practical nuclear fusion power plants are just 30 years away — and always will be.

But now, finally, the joke may no longer be true: Advances in magnet technology have enabled researchers at MIT to propose a new design for a practical compact tokamak fusion reactor — and it’s one that might be realized in as little as a decade, they say. The era of practical fusion power, which could offer a nearly inexhaustible energy resource, may be coming near.

Using these new commercially available superconductors, rare-earth barium copper oxide (REBCO) superconducting tapes, to produce high-magnetic field coils “just ripples through the whole design,” says Dennis Whyte, a professor of Nuclear Science and Engineering and director of MIT’s Plasma Science and Fusion Center. “It changes the whole thing.”

The stronger magnetic field makes it possible to produce the required magnetic confinement of the superhot plasma — that is, the working material of a fusion reaction — but in a much smaller device than those previously envisioned. The reduction in size, in turn, makes the whole system less expensive and faster to build, and also allows for some ingenious new features in the power plant design. The proposed reactor, using a tokamak (donut-shaped) geometry that is widely studied, is described in a paper in the journal Fusion Engineering and Design, co-authored by Whyte, PhD candidate Brandon Sorbom, and 11 others at MIT. The paper started as a design class taught by Whyte and became a student-led project after the class ended.

Power plant prototype

The new reactor is designed for basic research on fusion and also as a potential prototype power plant that could produce significant power. The basic reactor concept and its associated elements are  based on well-tested and proven principles developed over decades of research at MIT and around the world, the team says.

“The much higher magnetic field,” Sorbom says, “allows you to achieve much higher performance.”

Fusion, the nuclear reaction that powers the sun, involves fusing pairs of hydrogen atoms together to form helium, accompanied by enormous releases of energy. The hard part has been confining the superhot plasma — a form of electrically charged gas —  while heating it to temperatures hotter than the cores of stars. This is where the magnetic fields are so important—they effectively trap the heat and particles in the hot center of the device.

While most characteristics of a system tend to vary in proportion to changes in dimensions, the effect of changes in the magnetic field on fusion reactions is much more extreme: The achievable fusion power increases according to the fourth power of the increase in the magnetic field. Thus, doubling the field would produce a 16-fold increase in the fusion power. “Any increase in the magnetic field gives you a huge win,” Sorbom says.

Tenfold boost in power

While the new superconductors do not produce quite a doubling of the field strength, they are strong enough to increase fusion power by about a factor of 10 compared to standard superconducting technology, Sorbom says. This dramatic improvement leads to a cascade of potential improvements in reactor design.

The world’s most powerful planned fusion reactor, a huge device called ITER that is under construction in France, is expected to cost around $40 billion. Sorbom and the MIT team estimate that the new design, about half the diameter of ITER (which was designed before the new superconductors became available), would produce about the same power at a fraction of the cost and in a shorter construction time.

But despite the difference in size and magnetic field strength, the proposed reactor, called ARC, is based on “exactly the same physics” as ITER, Whyte says. “We’re not extrapolating to some brand-new regime,” he adds.

Another key advance in the new design is a method for removing the the fusion power core from the donut-shaped reactor without having to dismantle the entire device. That makes it especially well-suited for research aimed at further improving the system by using different materials or designs to fine-tune the performance.

In addition, as with ITER, the new superconducting magnets would enable the reactor to operate in a sustained way, producing a steady power output, unlike today’s experimental reactors that can only operate for a few seconds at a time without overheating of copper coils.

Liquid protection

Another key advantage is that most of the solid blanket materials used to surround the fusion chamber in such reactors are replaced by a liquid material that can easily be circulated and replaced, eliminating the need for costly replacement procedures as the materials degrade over time.

“It’s an extremely harsh environment for [solid] materials,” Whyte says, so replacing those materials with a liquid could be a major advantage.

Right now, as designed, the reactor should be capable of producing about three times as much electricity as is needed to keep it running, but the design could probably be improved to increase that proportion to about five or six times, Sorbom says. So far, no fusion reactor has produced as much energy as it consumes, so this kind of net energy production would be a major breakthrough in fusion technology, the team says.

The design could produce a reactor that would provide electricity to about 100,000 people, they say. Devices of a similar complexity and size have been built within about five years, they say.

“Fusion energy is certain to be the most important source of electricity on earth in the 22nd century, but we need it much sooner than that to avoid catastrophic global warming,” says David Kingham, CEO of Tokamak Energy Ltd. in the UK, who was not connected with this research. “This paper shows a good way to make quicker progress,” he says.

The MIT research, Kingham says, “shows that going to higher magnetic fields, an MIT speciality, can lead to much smaller (and hence cheaper and quicker-to-build) devices.” The work is of “exceptional quality,” he says; “the next step … would be to refine the design and work out more of the engineering details, but already the work should be catching the attention of policy makers, philanthropists and private investors.”

The research was supported by the U.S. Department of Energy and the National Science Foundation.

very good

Great! Congrats.

not bad i guess

Can this be inserted into an existing reactor. It seems like you could shorten the construction time by modding rather than starting from scratch?

The cautious tone is, no doubt, reflecting the many previous failures to do this - so good luck! Get Elon Musk or Google interested...

Faster, Please.

Watch out Tony Stark; looks like someone's stealing your idea. ;)

Well name anyway. :)

Good job MIT, about time! With this design, I'm seeing that other advances in superconductors will just lead to even more powerful plants, smaller and more compact. If this is viable on a large-scale, you might have just solved the Earth's energy problems!

I want to believe...

Hello im just curious if anyone knows how the earth creates lightning.we already know its a positive and negitive.whats making the positive charge in the air?friction from the pressure of zero gravity, which is pushing down on a spinning ozone, creating friction???? Throw a negitive to the positive and you got 1000 million volts too 1 billion volts of pure electricity....

Just half of the diameter of ITER - unfortunately means half the cost of ITER if done by the same inefficient methods. Even $20B is too much.

"New design could finally help to bring the long-sought power source closer to reality"

That's highly unlikely. Any design that ultimately uses a heat source to produce energy and a Rankine cycle to extract the energy is already more expensive than existing energy sources with even better credentials.

It doesn't make a difference if the heat source is coal, fission, fusion, or ground up pandas. If you consider even just the steam turbine equipment, it's already more expensive than a wind turbine producing the same energy - yes, even with a 33% average CF.

So, this means the ITER reactor project should be... scrapped, suspended, re-designed...?

Love to see an experimental prototype prove the theory behind this! Although I'm a little jaded by previous fusion 'breakthroughs' I can't help but feel excited by this one.

MIT want the U.S. government to pay MIT to do this. How about MIT license the young post-grads who wrote the paper to commercialize it?

When can we expect to see the Kickstarter campaign???

I want it to work but can't help being a bit cynical at the pre-match grandstanding..... "achievable fusion power increases according to the fourth power" but the current achievable fusion power is zero.

I predict it will be nicknamed the Rebco Donut.

tony stark's arc reactor is near to invent.......well done MIT researchers. i like it.

What about weight? is it possible to combine this with a Bussard drive and havepractical intersystem and perhaps interstellar transportation?

I'm guessing the inclusion of this engineering breakthrough in comments after a Dilbert cartoon increased awareness tenfold at least. Always knew something important was happening in all the time I've spent reading Dilbert. Now this! Wowed.

Oops. Perpetual energy? It will produce 3 times the amount of energy needed to make it work? Just take one third and feed it back into the unit...

$40 billion dollars for a reactor that won't work?

I wrote a term paper on nuclear fusion in 1958 in high school. I questioned how nuclear fusion would ever work pointing out that a nuclear bomb was being contained by a magnet and that enough energy to power a thousand homes was required to produce a nanosecond of electricty barely noticeable.

Nuclear fusion is a black hole exploited by various entities to acquire vast sums of money.

If all of the money spent on nuclear fusion was spent on solar panels we could cover the earth with them.

Yes it will have interstellar with super fluid helium 3 as coolant on rpm that will have 0 gravity. I designed a regular superconducting generator on ISO diagram on paper of course not physically. I had a protected chamber for the magnetic field could be 200 times stronger than the earth. Not cool if anyone disrupts that OK!!! That be terrorism! So after my 3/4 of drawn out I realized I hit o gravity and that if it was possible to be safely inside the generator there will be no g force. I accidential design a UFO. I love engineering and cryogenics. I am highly skilled. I am a plumber with many other gifts and college degrees. I have many designs and I have passion to solve water and energy crisis. Passion over rides being forced to work for all things. Follow your passion and carry on with safety first. We will know if disruption of magnetic from anyone who does not proceed with special protection of such unknown technology. Please carry on with the safety of our alive earth that is dieing from old ways. This is my thoughts only. Take care and God speed on the good work. neillium

Meh all these comments seem dreamy. Interstellar? This is the first alleged practicall fusion prototype being touted at being small, cheaper, and efficient and people are sitting here talking about interstellar nuttery.

MIT is looking to get some of the big money allocated for ITER. They know the DOE favors Tokamacs.

The core problem is that Tokamacs can't do any aneutronic reactions as required energy levels are too high. So even if they could get to net-positive energy, they'll destroy their superconductors so quickly (through neutron bombardment) that they'll not be able to succeed ultimately in producing a FINANCIALLY break-even machine.

Tokamacs have long been a joke to serious engineers, but they pay good money apparently.

For the future of fusion look to the polywell design.

Are they saying that doubling the magnet field would produce a 16 fold increase in power output purely from the tighter plasma confinement, holding the total amount of plasma constant and only spiking the density??

http://www.lockheedmartin.com/...

No mention of Lockheed's work in this area.

Sounds promising...$5 Billion is a achievable budget; dramatically less in the way of construction and operational complexity is a magnificent achievement; 3-6 times sustaining power as output is quite possibly close to commercially feasible...

Pssst... don't tell MIT but the Brits have beaten them to it...again https://www.youtube.com/watch?...

Nano materials composites are the newest article of 1663 of LANL or NNSA. This new material can multi different materials over lade and bonded together. This they explained in the magazine of NNSA where it all started. That they are working on newer ways of materials to take high intense radiation, coldest, and toughest stuff to play with. Sorry if it seems I should just stink to plumbing but can't. Cryogenic Engineering, mechanical engineering, and plumbing engineering is under me. Master of Science in Environmental and Civil Engineering is calling me after serious car accident. To who that thinks I'm should stink to plumbing. I was engineering my own pro type without fusion, fission, but kinetic force on a shaft that feeds liquid helium to 100% more effective power. "Maybe you should stop your ignorant mouth of your's and dream what's possible within yourself." You might learn a thing or two. Nano-compistes materials are so perfect for nuclear breach on filtration. Nano-filteration could solve the world's problems as with geothermal, space, fusion, and so on any ho. neillium

This is very cool and I hope it works out well. However, I don't understand what will cause this to succeed (politically) where the Integral Fast Reactor didn't. If we are seriously worried about clean and plentiful power generation, shouldn't we build some of the safe and insanely fuel-efficient plants that were developed over 20 years ago? There is no doubt that fusion will eventually be our primary energy source, but if a safe fission reactor design gets tabled by congress today, why would a fusion reactor make it through?

"In 2001, as part of the Generation IV roadmap, the DOE tasked a 242-person team of scientists from DOE, UC Berkeley, MIT, Stanford, ANL, LLNL, Toshiba, Westinghouse, Duke, EPRI, and other institutions to evaluate 19 of the best reactor designs on 27 different criteria. The IFR ranked #1 in their study which was released April 9, 2002.[41]

At present there are no Integral Fast Reactors in commercial operation, however a very similar fast reactor, operated as a burner of plutonium stockpiles, the BN-800 reactor, became commercially operational in 2014"

https://en.wikipedia.org/wiki/...

This is a serious, non-rhetorical, question. I would love to know the answer.

Give. Us. Fusion. Now!

People have been trying to get a fusion reactor to work for years - it seems to be an inherently difficult trick. An old friend of mine once said 'the only way to get a stable reliable fusion reactor going is nature's way - it's called a sun...'

I hope he's wrong.

One problem I consider tricky is that of stability. Suppose you get the hot plasma to a state in which it starts to react. At this point in space it's temperature will rise and it will expand - and the magnetic containment, which was right for the conditions just before the reaction started, is wrong for the now much hotter fluid.... what do you do?

I speak as a trained scientist completely ignorant of this area of research.

Allan.

Reprinted with permission of MIT News