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New results from the JET tokamak offer positive news for tokamak reactor designs based on deuterium-tritium fuel, according to the European Consortium for the Development of Fusion Energy, EUROfusion.

Reporting on experiments run in deuterium-tritium (DT) during JET's record-breaking campaign in 2021—and comparing them to control experiments performed in pure deuterium (DD)—EUROfusion researchers found that future fusion power plants using DT fuel may experience fewer energy losses in their burning plasma due to instabilities than previously anticipated.

"Our goal was to study whether our earlier findings on turbulence reduction in tokamak plasmas with high-energy ions could be replicated in DT plasmas, the primary fuel for the international ITER project and future fusion power plants," explain Jeronimo Garcia (CEA-IRFM, France) and Yevgen Kazakov (LPP-ERM/KMS, Belgium), the leading authors of a paper* published in Nature Communications.  

What they found in experiments that replicated ITER conditions as closely as possible was that, with tritium in the mix, core plasma conditions actually improved. They also observed "a new beneficial state" at the edge of the plasma, without unwanted energy bursts. "Our results demonstrate that the addition of heavier tritium ions has a calming effect on the plasma, reducing turbulence," says Garcia.

This is good news for ITER and future magnetic confinement fusion reactors. Alberto Loarte, head of the ITER Science Division, had this reaction: "The results in these studies show that there is better-than-expected performance in DT plasmas compared with DD plasmas; in particular, instabilities triggered by fast particles in DT plasmas such as those expected for fast helium produced by fusion in ITER can reduce energy losses from the plasma and increase fusion performance. The studies show that if instabilities remain at low levels they actually increase performance, whereas we had formerly assumed that they would most likely decrease it. The results also show that in conditions that are relevant to ITER, it might be possible to replace the intermittent burst of plasma energy through edge localized modes (ELMs) through a much more benign continuous outflow more easily handled by the wall in ITER."

See the original story on the EUROfusion website here.

*J. Garcia, Y. Kazakov et al., Nature Communications 15, 7846 (2024) https://doi.org/10.1038/s41467-024-52182-z

--Image: D-T plasma in JET pulse #99896, together with the computed zonal poloidal flows. Credits — plasma photo: UKAEA; flow calculation: FAR3D code

Speaking at a round table on the green energy transition at the Forum Aix-Marseille economic conference, head of the ITER Science & Integration Department Alain Becoulet said the fusion ecosystem was developing rapidly but wouldn’t be ready to meet short-term decarbonization goals.

“This is an important moment for humanity because the technology is coming out of the research laboratory and being demonstrated,” noted Becoulet. “ITER is part of a flotilla of advances in fusion research, industrial testing, and private-sector investment. This is creating the ecosystem and supply chain that will be needed to roll out this energy source on a planetary scale.”

However, Becoulet warned that even after the first fusion power plant is successfully demonstrated, it will take decades to build the thousands of plants required for a global energy transition. He added that in the meantime, broader use of conventional fission plants or new SMRs (small modular reactors) could reduce carbon emissions.

The conclusions of the day's debates and discussions will be shared at the national Cercle des Etats de la France conference, which helps shape France’s economic policies.