The Joint European Torus in Britain is preparing to start pivotal tests of a fuel mix that will eventually power the International Thermonuclear Experimental Reactor (Iter) – the world’s biggest nuclear-fusion experiment, Nature magazine reported.

In December, researchers at Jet started conducting fusion experiments with tritium, a rare and radioactive isotope of hydrogen. In June, Jet will begin fusing even quantities of tritium and deuterium, another isotope of hydrogen, Nature magazine said.