Most fusion power plant designs depend upon heating hydrogen isotopes to searing temperatures within a confined space. Eventually, when the isotopes are energised enough, they fuse with one another and form the element helium. This process yields neutrons that are able to exit the confinement and transfer their heat to a system that can spin turbines and generate electricity. Such designs are attractive since they would create neither the long lasting radioactive waste that fission power plants do nor would they depend upon rare materials like plutonium. Even so, there have been problems.
One key issue that engineers have struggled with is that of containing the super hot cloud of isotopes known as plasma. The main way that designers have aimed to do this is with magnetic fields that keep the highly energised particles in place but, as temperatures soar, the plasma can leak out of confinement, make contact with nearby physical walls and shed heat, which effectively ruins the fusion process.
In 2014, Lockheed Martin, an American engineering firm, announced that they had come up with a magnetic field design that would actively strengthen as plasma approached the walls but the company was vague on the details of how their design would work. Now, the MIT team is taking a different approach by simply making a much more powerful magnetic field and laying out the details of precisely how they would do it in Fusion Engineering and Design.
The new work, produced by a team of students led by PhD student Brandon Sorbom and his adviser Dennis Whyte, began as a class project and depends upon using a form of tape made from rare-earth barium copper oxide. The tape, which has only recently come on the market, is a superconductor, a material viewed as essential to fusion power plants because it allows strong magnetic fields to be produced without consuming large amounts of electricity. However, what makes the tape special amongst superconductors is that, unlike most which lose their superconducting properties when exposed to very high magnetic fields, the tape entirely retains its ability to superconduct under these conditions and produces a magnetic field that is twice as strong as result.
Not only is this strengthened field important for keeping plasma contained but it also forces the isotopes making up the plasma into a tighter space that drives more fusion events, releases more neutrons and generates more heat to be sent off to spin turbines. As such, the MIT team expect the generated fusion power of their design to be about ten times greater than the fusion power that would be created by a fusion power plant of similar size lacking the new superconducting tape.
While it might be possible to use the tape to build a reactor the size of ITER and generate even more power, Mr Sorbom and his colleagues argue that it is more prudent to use the tape to build a much smaller reactor that is more affordable and can be built on a shorter timescale.
As for an approximate price tag, using the cost of materials and of test reactor structures of similar sizes built in recent years, Mr Sorbom and his colleagues calculate that the cost to build the reactor would likely be in the region of 5.5 billion dollars. That is certainly expensive, but a mere fifth of the cost of ITER due to the new reactor’s considerably smaller size.
Formally, the MIT team refer to their design in the academic literature as an ARC reactor because it is affordable, robust and compact but, as those familiar with comic book lore are likely aware, ARC reactor technology is what powers the ironman suit. Indeed, Tony Stark attended MIT.