| March 1979
On March 28, 1979, one of the two nuclear reactors at Three Mile Island Nuclear Powerplant--located on an island in the Susquehanna River near Harrisburg, Pennsylvania--suffered a partial core meltdown. On that morning, several water-coolant pumps failed on the second reactor (TMI-2). The reactor shut itself down eight seconds later, but the core temperature continued to rise because valves controlling the emergency cooling water were stuck closed. The core was eventually flooded and brought under control. Minimal radioactive material was released. Because of uncertainty of how much radiation had been, or would be released, the Pennsylvania Governor ordered pregnant women and children within five miles of Three Mile Island evacuated as a precaution.
Although TMI-2's containment held, the reactor was heavily contaminated. No one could enter the plant for two years. The TMI-2 reactor was entombed in concrete. TMI-1 was restarted in 1986.