On March 28, 1979, at 4:00 am, reactor two of the Three Mile Island nuclear plant suffered a catastrophic failure. The problem was relatively simple: a stuck value prevented reactor coolant from returning to reactor core, causing the core to overheat and ultimately melt down. Around seven hours later, pressurized radioactive steam was vented into the atmosphere, causing radiation levels down-wind of the plant to be up to nine times higher up to 100 miles away.
