原子力安全・保安院
In March 2011, a 9.0-magnitude earthquake and its accompanying tsunami struck a nuclear power station in Fukushima Daiichi area of northeastern Japan. A number of safety systems were badly damaged by the tsunami leading to a loss-of-coolant (LOCA) event which damaged the nuclear core of several reactors. The Nuclear and Industrial Safety Agency (NISA) announced that the subsequent release of radioactivity into atmosphere qualified as the highest level of radiological event scale, INES level 7. The radioactive materials released in Fukushima Daiichi area are mostly iodine-131 and cesium-137.