Last year, the government officially decided to decommission Monju — the Japan Atomic Energy Agency’s prototype fast breeder reactor in Tsuruga, Fukui Prefecture. The government plans to continue developing a fast reactor with an eye on later developing a demonstration reactor, which are both seen as more practically feasible than the Monju reactor. For the time being, the government plans to continue developing and accumulating technology for ASTRID (see below) — an acronym for Advanced Sodium Technological Reactor for Industrial Demonstration — jointly with the French government. Current light-water reactors for commercial nuclear power plants mainly use uranium as fuel. Ordinary water, known as light water, cools the reactors. This water slows neutrons from the nuclear fission chain and effectively causes uranium to repeatedly split. Fast breeder reactors and fast reactors use plutonium as fuel and liquid sodium as coolant. Neutrons are not slowed down and can be used at high speeds. Fission occurs more easily when fast neutrons hit plutonium.
Japan News 13th Feb 2017 read more »