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South Korea takes massive step toward sustainable nuclear fusion reactions

Plasma at over 100 million kelvin for 20 seconds adds to list of noteworthy fusion breakthroughs in 2022

Scientists in Korea have succeeded in sustaining a plasma gas at 100 million kelvin for up to 20 seconds without significant instabilities, a feat thought to be a significant step forward in the quest for a sustainable nuclear fusion reaction.

Nuclear fusion – in which huge amounts of energy are released from the fusing of lighter elements into heavier ones – has become something of a Holy Grail in the search for a replacement for fossil fuels.

Despite progress in the field, a sustainable reactor that produces more energy than it consumes still remains some way off.

One of the barriers has been maintaining the stability and temperature of plasma – the fourth state of matter made up of unbound ions or charged atoms.

Korea Superconducting Tokamak Advanced Research, or KSTAR, operates using a hydrogen plasma confined by a magnetic field.

But researchers have so far been unable to achieve a sustainable fusion performance, which requires a high temperature above 100 million kelvin and sufficient control of instabilities to ensure steady-state operation in the order of tens of seconds.

Researchers at the facility now report they have overcome the threshold. "Here we report experiments at the Korea Superconducting Tokamak Advanced Research device producing a plasma fusion regime that satisfies most of the above requirements," a research paper published in Nature said.

"A low plasma density combined with a moderate input power for operation is key to establishing this regime by preserving a high fraction of fast ions. This regime is rarely subject to disruption and can be sustained reliably even without a sophisticated control, and thus represents a promising path towards commercial fusion reactors," the authors said.

This year has seen other – albeit incremental – breakthroughs in the journey toward a sustained fusion reaction.

In January, researchers at National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California described how they achieved burning plasma – where the heat from fusing nuclei takes over as the main source of fuel heating – across four experiments which each produced more than 100 kilojoules of energy.

The result marked an important step toward nuclear fusion, but it is not true ignition – where a self-sustaining reaction will produce more energy than goes in.

In February, scientists and engineers running the Joint European Torus (JET) facility in Oxford, UK, announced a record-breaking 59 megajoules of heat energy from fusion, more than double the previous record achieved by JET.

Yet some experts remain downbeat about the prospects for the commercialization of nuclear fusion as a power source in the next two or three decades.

Speaking to the UK's Parliament in May, the aptly named Dame Sue Ion, former chair of the UK Nuclear Innovation Research Advisory Board, said the physics might demonstrate net gain this decade or the beginning of the next.

"But when will you get a prototype plant that demonstrates that commercial fusion may be even remotely possible? You're talking about post-2040. If you're talking about the availability of fusion power on the grid, then it is well into the second half of the century, if all the engineering and technical challenges that are yet to come are solved," she told MPs.

"I think there's a difference between confidence that it will work and confidence that it will work 24 hours a day, seven days a week, 365 days a year and satisfy an economic environment in which it's got to live. And my answer to that is, I honestly don't know."

At the same hearing, Tim Luce, head of science and operation at ITER, the world's largest fusion experiment relying on magnetic confinement, warned that any economically viable fusion power source was unlikely to arrive in time to avoid the "sacrifices" that will be necessary to meet climate change targets. ®

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