The accident occurred when engineers were testing the operation of the cooling system and the emergency cooling systems of nuclear testing, but the members have been delayed over the set to rehearse by night shift engineer. Has a higher vapor pressure suddenly cutting automation systems, but it doesn't work. Resulted in a higher heat to members no. 4 nuclear meltdown and explosion-proof. The result from the explosion caused the radiation contaminated ashes kammantaphap spout up to the atmosphere. Cover to the West of the Soviet Union. Eastern Europe. Europe, Northern Europe, Western Belarus and Russia Ukraine political. The population of more than 336,000 people leaving the area contingency sample.