On December 8, 1995, metallic sodium leaked from the secondary cooling system of Monju, the fast breeder reactor in Tsuruga, Fukui Prefecture, and caught fire. According to the magazine Gendai, its operator at the time, Dōnen, made false reports and repeatedly tried to conceal what had happened. Monju restarted in May 2010. In August of the same year, a device used in fuel handling fell inside the reactor, and Monju stopped again.
In December 2016, a meeting of the ministers responsible for nuclear energy decided that Monju would not restart and would be decommissioned. More than one trillion yen had been spent on it. According to nippon.com, it had operated on only 250 days in 22 years.