The Korean nuclear fusion reactor reaches 100 million degrees Celsius for 30 seconds

Continuous and stable experiment is the latest evidence that nuclear fusion is moving from being a physical problem to an engineering problem


7 September 2022

fusion reactor

Tokamak’s Superconducting Korean Advanced Search Experience

korean institute of fusion energy

The nuclear fusion reaction lasted for 30 seconds at temperatures over 100 million degrees Celsius. While duration and temperature alone do not record, the simultaneous achievement of heat and stability brings us one step closer to a viable fusion reactor—as long as the technology used can be scaled up.

Most scientists agree that the viable force of fusion is still decades away, but incremental advances in understanding and results are still to come. An experiment conducted in 2021 has created a reaction active enough to be self-sufficient, and concept designs for a commercial reactor are being developed, while work continues on a large ITER experimental fusion reactor in France.

Currently Young Soo Na At Seoul National University in South Korea, his colleagues succeeded in performing a reaction at the extremely high temperatures that would be required for a viable reactor, keeping the state of the hot ionized material formed inside the device stable for 30 seconds.

The control of the so-called plasma is vital. If it touches the walls of the reactor, it cools quickly, suffocating the reaction and causing significant damage to the chamber that holds it. Researchers typically use different forms of magnetic fields to contain the plasma — some use an edge transfer barrier (ETB), which sculpts the plasma with a sharp cut in pressure near the reactor wall, a condition that prevents heat and plasma from escaping. Others use an internal transport barrier (ITB) that creates a higher pressure near the center of the plasma. But both can create instability.

The Na team used modified ITB technology in the Korea Tokamak Superconducting Advanced Research (KSTAR) instrument, achieving a much lower plasma density. Their approach appears to enhance and lower temperatures in the plasma core at the tip, which could extend the life of reactor components.

To increase the power a reactor produces, you can make the plasma really hot, make it really dense or increase the confinement time, says Dominic Power of Imperial College London.

“This team discovered that the confinement density is actually slightly lower than in conventional operating modes, which isn’t necessarily a bad thing, because it is compensated by higher core temperatures,” he says. “It’s certainly exciting, but there is a great deal of uncertainty about how well we understand physics at the larger hardware scale. So something like ITER would be much, much bigger than KSTAR.”

Na says that lower densities were key, and that “fast” or more active ions in the plasma core – the so-called fast ionic regulated improvement (FIRE) – are integral to stabilization. But the team did not yet fully understand the mechanisms involved.

The interaction was stopped after only 30 seconds due to hardware limitations, and longer periods should be possible in the future. KSTAR is now closed to upgrades, with the carbon components on the reactor wall replaced with tungsten, which Na says will improve the repeatability of the experiments.

Lee Margets At the University of Manchester, UK, he says the physics of fusion reactors is now well understood, but there are technical hurdles to overcome before a working power plant can be established. Part of that will be developing ways to draw heat from the reactor and use it to generate electric current.

“It’s not physics, it’s engineering,” he says. “If you just think about this from the point of view of a gas or coal power plant, if you don’t have anything that removes the heat, the people running it will say ‘we have to switch it off because it gets too hot and it will melt the power plant,’ which is exactly the situation here.” .

Brian Appleby At Imperial College London, he agrees that the remaining scientific challenges in fusion research must be achievable, and that FIRE is a step forward, but that commercialization will be difficult.

“The magnetic confinement fusion approach has a very long history of development to solve the next problem it faces,” he says. “But the thing that makes me a bit nervous, or uncertain, is the engineering challenges of building an economical power plant based on this.”

Journal reference: temper natureAnd the DOI: 10.1038 / s41586-022-05008-1

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