Three Mile Island Accident

The three mile island (tmi) plant, located on the Susquehanna River, about 10 miles from Harrisburg, Pennsylvania, was the site of what the Nuclear Regulatory Commission (NRC) calls the most serious nuclear accident in American history. Metropolitan Edison then owned the TMI facility, consisting of two reactors. The accident began at about 4:00 a.m. on March 28, 1979, in the nonnuclear section of the power plant, when the pumps that feed water to the system to create steam (which propelled the power turbines) failed. Because these pipes carry away part of the heat from the reactor, the cooling system would be required to carry the extra load. The water and steam pressure increased in the cooling system, which caused a relief valve to open. The ...