Three Mile Island.docx - Three Mile Island accident The...

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Three Mile Island accident The Three Mile Island accident occurred on March 28, 1979, in reactor number 2 of Three Mile Island Nuclear Generating Station (TMI-2) in Dauphin County, Pennsylvania , United States , near Harrisburg . It was the most significant accident in U.S. commercial nuclear power plant history. The incident was rated a five on the seven-point International Nuclear Event Scale . The accident began with failures in the non-nuclear secondary system, followed by a stuck-open pilot-operated relief valve in the primary system, which allowed large amounts of nuclear reactor coolant to escape. The mechanical failures were compounded by the initial failure of plant operators to recognize the situation as a loss- of-coolant accident due to inadequate training and human factors , such as human- computer interaction design oversights relating to ambiguous control room indicators in the power plant's user interface . The accident crystallized anti-nuclear safety concerns among activists and the general public, resulted in new regulations for the nuclear industry, and has been cited as a contributor to the decline of a new reactor construction program that was already underway in the 1970s. The partial meltdown resulted in the release of radioactive gases and radioactive iodine into the environment. Worries were expressed by anti- nuclear movement activists; however, epidemiological studies analyzing the rate of cancer in and around the area since the accident, determined there was a small statistically non-significant increase in the rate and thus no causal connection linking the accident with these cancers has been substantiated. Cleanup started in August 1979, and officially ended in December 1993, with a total cleanup cost of about $1 billion. Emergency declared At 6:57 am, a plant supervisor declared a site area emergency , and less than 30 minutes later station manager Gary Miller announced a general emergency, defined as having the "potential for serious radiological consequences" to the general public. He held a press conference in which he was reassuring, yet confusing, about this possibility, stating that though there had been a "small release of radiation...no increase in normal radiation levels" had been detected. These were contradicted by another officials who claimed that no radioactivity had been released. In fact, readings from

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