Fusion experiment sets new energy record

The era of the Joint European Torus (JET) ends with a new world record for fusion energy. The European test facility in the UK generated 69 megajoules of energy for five seconds - more than any other fusion facility before it. These results were presented by the UK Atomic Energy Authority (UKAEA) at a press conference on 8 February 2024.

Fusion power plants are designed to mimic the processes inside the sun, where the light atomic nuclei of hydrogen fuse together. To do this, the particles have to overcome their electrical repulsion. While in the sun, the enormous force of gravity compresses and heats everything sufficiently, this requires strong magnetic fields and high temperatures of more than 100 million degrees Celsius in terrestrial reactors.

The new result from JET is one of its last: it comes from a final series of experiments that were carried out with JET before its decommissioning in December 2023. The techniques researched with the facility since 1983 provided the basis for four decades for the much larger successor ITER in France, which is still under construction after numerous delays.

Even with experiments in December 2021 JET managed to set a world record announced in 2022 by releasing 59 megajoules of heat during a plasma discharge that also lasted five seconds, which corresponds to the calorific value of several kilograms of lignite. And as has now become public, JET beat its own record by ten megajoules with a pulse on 3 October 2023. The 0.2 milligrams of fuel used for this consisted of the hydrogen types deuterium and tritium. Such a mixture is also considered promising for a future fusion power plant. As Athina Kappatou from the Max Planck Institute for Plasma Physics in Garching explained, the record was ultimately a fortunate side effect of experiments in which various scenarios for future power plants were tested.

To generate this amount of heat, however, about three times as much energy was needed to heat up JET, as scientific coordinator Mikhail Maslov explained during the press conference. The energy balance was therefore not positive.

While JET produced a continuous output of around 13 megawatts over the pulse duration of five seconds, the successor project ITER is designed for around 500 megawatts. The experiments there should ultimately achieve a positive energy balance - but will still not feed any electricity into the grid. The scientific director of ITER, Tim Luce, made it clear during the press conference that he does not expect experiments at ITER to match those of JET until the "second half of the next decade".

When a fusion power plant will be built that actually contributes to the electricity supply for mankind - and whether other projects, for example in China, will beat the European endeavours to the punch - remains to be seen. In response to the old question posed during the press conference as to whether commercial nuclear fusion is still 20 years away, the panel of experts responded with a general smile and a hope expressed by Kappatou: "Humanity needs fusion energy. It's worth sticking to the goal."

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