Korean nuclear fusion reactor achieves 100 million °C for 30 seconds

While the duration and temperature alone aren't records, the simultaneous achievement of heat and stability brings us a step closer to a viable fusion reactor

The majority of scientists agree that fusion power is still decades away. Conceptual designs for a commercial reactor are being drawn up while work continues on the large ITER experimental fusion reactor in France.

Yong-Su Na and his colleagues have been able to keep the hot, ionised state of matter in the device stable for 30 seconds by running a reaction at extremely high temperatures.

This is important to control. If it touches the walls of the reactor it will quickly cool and cause a lot of damage. Some researchers use an edge transport barrier, which is a sharp cut-off in pressure near to the reactor wall, to sculpt the plasma and keep it from escaping. Other people use an internal transport barrier that creates higher pressure closer to the centre. Both can cause instability.

The Korea Superconducting Tokamak Advanced Research (KSTAR) device was used by Na's team to achieve a lower plasma density. The approach seems to boost temperatures at the core of the plasma and lower them at the edge, which will likely extend the lifespan of reactor components.

Dominic Power at Imperial College London says that it's possible to increase the energy produced by a reactor by making it hotter, denser or more dense.

He says that the density confinement is compensated for by higher temperatures in the core, which is a good thing. There is a lot of uncertainty about how well our understanding of the physics scales to larger devices. ITER is going to be larger than KSTAR.

Read more: DeepMind uses AI to control plasma inside tokamak fusion reactor

Na says that the key to stability was low density and fast ion-regulated enhancement. The team doesn't know the mechanisms involved.

Limitations with hardware stopped the reaction after 30 seconds. Na says that carbon components on the wall of the reactor will be replaced with tungsten in order to improve the reproducibility of experiments.

There are technical hurdles that need to be overcome before a fusion reactor can be built, according to Lee Margetts at the University of Manchester. The method of withdrawing heat from the reactor will be developed.

He says it's engineering. If you think about it from the point of view of a gas-fired or a coal-fired power station, if you didn't have anything to take the heat away, they would switch it off.

The scientific challenges left in fusion research should be doable, but it will be hard to make money from it.

He says that the magnetic confinement fusion approach has evolved to solve the next problem. The engineering challenges of actually building an economical power plant based on this is something that makes me uneasy.

There is a journal reference called Nature.