MIT researchers have found a way for nuclear fusion reactors to shed excess heat, one of the biggest hurdles to making them work.

If predictions are anything to go by, the first nuclear fusion reactors – where near-limitless, clean and cheap energy could be produced – are just a few decades away. While some remain sceptical of this vision, a number of the world’s top scientists are working to make it a reality.

To that end, a team of researchers at MIT has helped find an answer to one of the biggest problems posed by the technology: how to shed excess heat.

The team’s design is unlike that of typical fusion plants, making it possible to open the device’s internal chamber and replace critical components. This is essential for the newly proposed heat-draining mechanism when temperatures inside the chamber reach millions of degrees Celsius.

Like a car exhaust

Publishing their findings to the journal Fusion Engineering and Design, the researchers said the way the design sheds heat is similar to the exhaust in a car. In the new design, the ‘exhaust pipe’ is much longer and wider than is possible in any of today’s versions. This means that while it is much better at shedding heat, the engineering needed to make that possible required dozens of design alternatives.

After much trial and error, the team eventually created a design known as the ARC, standing for advanced, robust and compact. Featuring magnets built in sections for easy removal, it is possible to access the entire interior of the chamber and place the secondary magnets inside its main coils rather than outside.

In conventional fusion reactor designs, the secondary magnetic coils (which shape the plasma) lie outside the primary ones, because there is simply no way to put these coils inside the solid primary coils. That means the secondary coils need to be large and powerful, to make their fields penetrate the chamber. As a result, they are not very precise in how they control the plasma shape.

Revolutionary design

Not only do the high-temperature superconductors used in the ARC design’s magnets enable a compact, high-powered power plant, but they also provide a lot of options for optimising the design in different ways.

Described by the director of MIT’s Plasma Science and Fusion Center, Prof Dennis Whyte, as a “really exciting” and “revolutionary” design, the exhaust concept brings us one step closer to achieving a working fusion reactor.

If achieved, it would allow for engineers to produce clean, abundant energy using a fuel derived from seawater called deuterium.

“This is opening up new paths in thinking about divertors and heat management in a fusion device,” Whyte said.