Three Mile Island Nuclear Accident (4 h, mar 28, 1979 y – 4 h, mar 28, 1979 y)
The Unit 2 reactor had a partial meltdown. When this happened it released radioactive gases and radioactive iodine into the air. This was caused by a drastic decrease of coolant in the reactor causing it to overheat and start the meltdown. When the workers noticed this they rushed over and looked at the core's water amount that was still full. They thought that if it was full then the reactor had enough in it. The reactor had a stuck open valve that was draining all of the water right out of it.
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