A cutaway view of the proposed ARC reactor. Thanks to powerful new magnet technology, the much smaller, less-expensive ARC reactor would deliver the same power output as a much larger reactor. Credit: the MIT ARC team
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. Using rare-earth barium copper oxide (REBCO) superconducting tapes, to produce high-magnetic field coils “just ripples through the whole design,” says Prof Dennis Whyte.
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 hard part has been confining the superhot plasma—electrically charged gas— while heating it to temperatures hotter than the cores of stars. Magnetic fields trap the heat and particles in the hot center of the device. The achievable fusion power increases according to the 4th power of the increase in the magnetic field. ie doubling field =16X increase in the fusion 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 vs standard superconducting technology.
MIT PhD candidate Brandon Sorbom holds REBCO superconducting tapes (left), which are the enabling technology behind the ARC reactor. When it is cooled to liquid nitrogen temperature, the superconducting tape can carry as much current as the large copper conductor on the right, enabling the construction of extremely high‑field magnets, which consume minimal amounts of power. Credit: Jose‑Luis Olivares/MIT
The world’s most powerful planned fusion reactor, 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, would produce about the same power at afraction of the cost and in a shorter construction time.
Another key advance is a method for removing the the fusion power core from the donut-shaped reactor without having to dismantle the entire device which is good for research aimed at improving the system by using different materials or fine-tune the performance. The new superconducting magnets enables the reactor to produce 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.
+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.
The reactor should be capable of producing ~3X as much electricity as is needed to keep it running, but the design could probably be improved to increase that proportion to about 5-6X. 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 design could produce a reactor that would provide electricity to about 100,000 people, 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.
https://newsoffice.mit.edu/2015/small-modular-efficient-fusion-plant-0810
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