The accident at

Three Mile Island

was a partial melting of the heart of unit 2 (a pressurized water reactor manufactured by Babcock & Wilcox) of Three Mile Island Nuclear Generating Station in Dauphin County, Pennsylvania, near Harrisburg in 1979. The plant was owned and operated by General Public Utilities and the Metropolitan Edison Co. He was the biggest accident in the history of commercial production of the U.S. nuclear industry, with consequent release of up to 481 PBq (13 million curies) of radioactive gases, but less than 740 GBq (20 curies) of particularly hazardous iodine-131.

The incident began at 04:00 Wednesday, March 28, 1979, the deficiencies in the system of non-nuclear, followed by a controlled valve stuck open (PORV) in the primary circuit, which has large amount of reactor coolant Nuclear run.