JET fusion reactor breaks energy record with output of 59MJ

Researchers at the JET nuclear fusion reactor have broken their nearly 25-year-old energy record. The fusion reactor delivered a power of approximately 11MW for 5 seconds, for a total energy of 59MJ. The old record was 22MJ.

The fusion experiment dates from December 21, 2021, but the data has only now been processed and published. The old record is not completely broken. In 1997, the researchers managed to generate a peak power of 16MW in the fusion reactor, but the reaction could only be sustained for a short time. This resulted in an energy output of 21.7MJ. Although the peak power was lower at the new record, the fusion reaction was sustained longer. As a result, a total energy output of 59MJ could be achieved with a capacity of 11MW. The fusion reaction was sustained for five seconds, much longer than the large second of the 1997 record.

Before the fusion, a plasma of deuterium and tritium was generated and confined in a tokamak reactor. Such a reactor encloses the hot plasma with the help of magnetic fields, so that it does not melt the walls. Deuterium and tritium protons can fuse in the plasma to, among other things, helium, converting part of the mass of the reactants into energy. The JET tokamak is a smaller version of ITER’s under construction reactor; the latter is about ten times as large. Both reactors are research reactors that are being developed by a consortium of European research institutes. The Joint European Torus is located in Oxford, UK, while ITER is under construction in the south of France. Both reactors are not intended to actually be put into operation for energy production, but to investigate the feasibility of a commercial nuclear fusion reactor.

With the new energy record, and in particular the duration of maintaining the plasma, an important step has been taken towards that feasibility. The reaction of the JET reactor is not energy positive. The Q factor, the ratio between energy input and energy production, was 0.33 in the 5 second reaction in the last experiment. Only with a Q-value above 1, a reactor provides net energy. The JET researchers are working, among other things, on a way to channel the heat produced at the outlet of the reactor in the right direction. That is something that will be even more difficult with the larger ITER reactor.