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This Reactor May Have Finally Solved Nuclear Fusion's Biggest Problem

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a close up of a light: This nuclear reactor may have finally solved fusion's biggest problem. The next frontier for energy is closer than it's ever been.

Atomic Energy Authority/Culham Centre for Fusion Energy/EUROFusion This nuclear reactor may have finally solved fusion's biggest problem. The next frontier for energy is closer than it's ever been.

  • A unique nuclear reactor could finally solve a huge fusion problem.
  • The MAST Upgrade tokamak has a special exhaust system that reduces heat.
  • With less heat, the reactor can run longer without replacing ruined parts.

With a revolutionary new heat exhaust system, scientists in England might have just found the key to unlocking a cooler future for nuclear fusion—and brought the world one step closer to actually realizing the long-promised next frontier for energy.

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Scientists have worked for decades on different tokamak reactors, or donut-shaped chambers in which atoms are combined (fused, for fusion) to generate plentiful energy. The white-hot plasma can reach 100 million degrees Fahrenheit or more, causing heavy wear and tear on all the components of these reactors.

There are downsides and controversial elements to fusion research. So far, no tokamak reactor has “recouped” its own energy cost—not even close!—so no one has demonstrated that nuclear fusion even works as an energy source, let alone the plentiful source its advocates say it will be.

For naysayers, this is evidence that fusion is farfetched and impractical. The running joke is that nuclear fusion is always 10 to 20 years away.

diagram: MAST Upgrade’s full exhaust system highlighted in green.

MAST Upgrade’s full exhaust system highlighted in green.

Enter the Culham Centre for Fusion Energy, which operates under the U.K. Atomic Energy Authority (UKAEA). There, scientists have built the Mega Amp Spherical Tokamak (MAST), which originally operated from 2000 to 2013 and has been upgraded and boosted for the 2020s. Now, MAST Upgrade is using its new heat exhaust system, the Super-X diverter, to greatly reduce the heat burden on all of the spherical tokamak’s parts.

Exhaust heat is such a big issue for tokamaks that it’s actually the primary focus of the whole MAST Upgrade project. Inside the tokamak reactor itself, plasma is contained by a powerful magnetic field, so the super-hot plasma doesn’t touch the walls. But heat must be able to vent out of the tokamak, and that’s where destruction starts.

The super-hot exhaust is removed by a system called the diverter, and the current crop of diverters is too fragile to be in the line of fire inside of tokamaks. “Diverter components would require replacement every few years, making it difficult for fusion to become an economically competitive energy source,” UKAEA writes.

a close up of a blackboard: The Super-X Diverter highlighted in a schematic diagram.

 The Super-X Diverter highlighted in a schematic diagram.

Enter the Super-X diverter, which decreases the heat output tenfold.

“Super-X reduces the heat on the exhaust system from a blowtorch level down to more like you’d find in a car engine,” lead scientist Andrew Kirk said in a UKAEA statement. That, in turn, means the diverter can last a lot longer with the same parts—cutting down on reactor shutdowns for replacing them.

So, what does this mean for the future of nuclear fusion? Well, IKAEA says exhaust heat has been one of the major obstacles to a working compact fusion power plant, which the U.K. hopes to build and get online by the 2040s. If the Super-X diverter can reduce the heat burden to a manageable level, that could be the last missing piece to a very challenging puzzle.

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