Wednesday, May 16, 2012



- (?) in one place described as "A 1999 cable-TV documentary which probes the March 1979 near-catastrophe at the Three Mile Island nuclear power plant in Pennsylvania."

- in another place: "1999 PBS-TV documentary, "Meltdown At Three Mile Island", chronicling the terrifying near-catastrophe that occurred in Pennsylvania at the Three Mile Island nuclear power plant in March 1979."

Three Mile Island accident - Wikipedia, the free encyclopedia

Three Mile Island accident

From Wikipedia, the free encyclopedia

President Jimmy Carter touring the TMI-2 control room with (l to r) Harold Denton, Governor Dick Thornburgh, and James Floyd, supervisor of TMI-2 operations, on July 9th, 1979.

President Jimmy Carter leaving Three Mile Island for Middletown, Pennsylvania, April 1, 1979.
The Three Mile Island accident was a partial nuclear meltdown which occurred at the Three Mile Island power plant in Dauphin County, Pennsylvania, United States on March 28, 1979. It was the worst accident in U.S. commercial nuclear power plant history,[1] and resulted in the release of small amounts of radioactive gases and radioactive iodine into the environment.
The power plant was owned and operated by General Public Utilities and Metropolitan Edison(Met Ed). The reactor involved in the accident, Unit 2, was a pressurized water reactormanufactured by Babcock & Wilcox.
The accident began at 4 a.m. on Wednesday, March 28, 1979, with failures in the non-nuclear secondary system, followed by a stuck-open pilot-operated relief valve (PORV) 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. In particular, a hidden indicator light led to an operator manually overriding the automatic emergency cooling system of the reactor because the operator mistakenly believed that there was too much coolant water present in the reactor and causing the steam pressure release.[2] The scope and complexity of the accident became clear over the course of five days, as employees of Met Ed, Pennsylvania state officials, and members of the U.S. Nuclear Regulatory Commission (NRC) tried to understand the problem, communicate the situation to the press and local community, decide whether the accident required an emergency evacuation, and ultimately end the crisis. The NRC's authorization of the release of 40,000 gallons of radioactive waste water directly in the Susquehanna River led to a loss of credibility with the press and community.[2]
In the end the reactor was brought under control, although full details of the accident were not discovered until much later, following extensive investigations by both a presidential commission and the NRC. The Kemeny Commission Report concluded that "there will either be no case of cancer or the number of cases will be so small that it will never be possible to detect them. The same conclusion applies to the other possible health effects".[3] Several epidemiological studies in the years since the accident have supported the conclusion that radiation released from the accident had no perceptible effect on cancer incidence in residents near the plant, though these findings are contested by one team of researchers.[4]Cleanup started in August 1979 and officially ended in December 1993, with a total cleanup cost of about $1 billion.[5] The incident was rated a five on the seven-point International Nuclear Event Scale: Accident With Wider Consequences.[6][7]
Communications from officials during the initial phases of the accident were confusing.[8] There was an evacuation of 140,000 pregnant women and pre-school age children from the area.[9][10][11] 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 new reactor construction that was already underway in the 1970s.[12] Public reaction to the event was probably influenced by The China Syndrome, a movie which had recently been released and which depicts an accident at a nuclear reactor.[13]

Current status

Viewed from the west, Three Mile Island currently uses only one nuclear generating station, TMI-1, which is on the left. TMI-2, to the right, has not been used since the accident. Note that this is a pre-accident photo taken when TMI-2 was in operation.
Unit 1 had its license temporarily suspended following the incident at Unit 2. Although the citizens of the three counties surrounding the site voted by a margin of 3:1 to retire Unit 1 permanently, it was permitted to resume operations in 1985. General Public Utilities Corporation, the plant's owner, formed General Public Utilities Nuclear Corporation (GPUN) as a new subsidiary to own and operate the company's nuclear facilities, including Three Mile Island. The plant had previously been operated by Metropolitan Edison Company (Met-Ed), one of GPU's regional utility operating companies. In 1996, General Public Utilities shortened its name to GPU Inc. Three Mile Island Unit 1 was sold to AmerGen Energy Corporation, a joint venture betweenPhiladelphia Electric Company (PECO), and British Energy, in 1998. In 2000, PECO merged with Unicom Corporation to form Exelon Corporation, which acquired British Energy's share of AmerGen in 2003. Today, AmerGen LLC is a fully owned subsidiary of Exelon Generation and owns TMI Unit 1, Oyster Creek Nuclear Generating Station, and Clinton Power Station. These three units, in addition to Exelon's other nuclear units, are operated by Exelon Nuclear Inc., an Exelon subsidiary.
General Public Utilities was legally obliged to continue to maintain and monitor the site, and therefore retained ownership of Unit 2 when Unit 1 was sold to AmerGen in 1998. GPU Inc. was acquired by FirstEnergy Corporation in 2001, and subsequently dissolved. FirstEnergy then contracted out the maintenance and administration of Unit 2 to AmerGen. Unit 2 has been administered by Exelon Nuclear since 2003, when Exelon Nuclear's parent company, Exelon, bought out the remaining shares of AmerGen, inheriting FirstEnergy's maintenance contract. Unit 2 continues to be licensed and regulated by the Nuclear Regulatory Commission in a condition known as Post Defueling Monitored Storage (PDMS).[89]
Today, the TMI-2 reactor is permanently shut down with the reactor coolant system drained, the radioactive water decontaminated and evaporated, radioactive waste shipped off-site, reactor fuel and core debris shipped off-site to a Department of Energy facility, and the remainder of the site being monitored. The owner says it will keep the facility in long-term, monitored storage until the operating license for the TMI-1 plant expires at which time both plants will be decommissioned.[14] In 2009, the NRC granted a license extension which means the TMI-1 reactor may operate until April 19, 2034.[90][91]

No comments:

Post a Comment