A nuclear disaster that occurred at the Fukushima nuclear power plant in Japan following a major earthquake and tsunami on 11 March 2011. It led to a series of equipment failures resulting in a nuclear meltdown, explosion, and the release of radioactive material into the environment. The tsunami was responsible for breaking the connection to one of the boiling water reactors to the power grid, causing the reactors to overheat. The earthquake and flooding prevented a controlled shutdown. Seawater was used in an attempt to cool the reactors before some electrical power was eventually restored to cool the reactors. It was the biggest nuclear accident since Chernobyl in 1986.