The disaster at the Chernobyl nuclear power plant in Pripyat, Ukraine (then part of the Soviet Union) produced more than 400 times more radiation than the Hiroshima atomic bomb and is considered to be the worst nuclear accident in history.

April 26, 1986: Reactor Number Four at the Soviet-designed plant explodes after an experiment when staff temporarily cut off the reactor’s safety systems, aiming to test the unit’s capacity. Shortly afterwards a series of powerful blasts caused by overheated steam inside the reactor completely destroys the unit.