Two decades after a sodium leak and fire shut it down and nearly six decades after it was first conceived, the Monju prototype fast-breeder reactor in Tsuruga, Fukui Prefecture, suffered another blow Wednesday when the Nuclear Regulation Authority called for it to be turned over to another operator.

To date, over ¥1 trillion has been poured into Monju — a plant that has never produced commercial electricity. Despite remaining inactive, safety measures alone cost ¥50 million a day.

Anti-nuclear activists have hailed the NRA's unusually critical language as an important step toward scrapping the reactor, which was supposed to burn plutonium mixed with uranium.