The core of the Russian Fast Breeder Reactor on June 27, 2017 in Zarechny, Svedlovsk Oblast, Russia. Pallava BaglaGetty Images That’s not the case in China. The CFR-600 is a sodium-cooled fast-neutron reactor, which means instead of using water, like most of the world’s working nuclear power plants, it’s cooled by liquid sodium, with a much broader temperature range and less interactivity than water. And fast neutrons have more natural energy than the alternative, thermal neutrons, which must be held in a temperature-controlled medium in order to act. Fast reactors don’t require the medium. Inside the CFR-600 is a fuel called