Three Mile Island Unit 2

Three Mile Island Unit 2
Name	Three Mile Island Unit 2
Location	Dauphin County, Pennsylvania, Susquehanna River
Coordinates	40°06′35″N 76°40′40″W
Country	United States
Operator	Metropolitan Edison Company / General Public Utilities Corporation
Reactor type	Pressurized water reactor
Reactor supplier	Babcock & Wilcox
Construction start	1968
Commissioned	1974
Status	defueled, partially dismantled

Contents

Three Mile Island Unit 2 Three Mile Island Unit 2 was a nuclear reactor located on Three Mile Island near Harrisburg, Pennsylvania that experienced a partial core meltdown in 1979, producing a seminal crisis involving Nuclear Regulatory Commission, President Jimmy Carter, and widespread public concern. The event catalyzed action from Nuclear Regulatory Commission, spurred litigation involving General Public Utilities Corporation and Metropolitan Edison Company, and influenced policy debates in the United States Congress, Environmental Protection Agency, and state governments.

Background and design

Unit 2 was a pressurized water reactor designed and built by Babcock & Wilcox and operated by Metropolitan Edison Company under ownership of General Public Utilities Corporation. The plant sat on Three Mile Island in Dauphin County, Pennsylvania on the Susquehanna River near Harrisburg, Pennsylvania. Its design followed commercial PWR features used by other plants such as Indian Point Energy Center and Davis-Besse Nuclear Power Station, including a primary coolant loop, steam generators, pressurizer, and emergency core cooling systems influenced by earlier reactors like Shippingport Atomic Power Station and designs overseen by the Atomic Energy Commission. Regulatory licensing involved the Nuclear Regulatory Commission and state utility regulators including the Pennsylvania Public Utility Commission.

On March 28, 1979, a combination of mechanical failures, including a stuck-open pilot-operated relief valve and feedwater pump malfunctions, produced a loss-of-coolant condition and partial core meltdown at Unit 2 that paralleled concerns raised after incidents at reactors such as Fermi 1 and SL-1. The sequence involved operators at Metropolitan Edison Company and control-room crew actions that were later compared to operator responses in event analyses by the Nuclear Regulatory Commission, investigators from the Department of Energy, and independent panels like the Kemeny Commission. Media coverage by outlets including The New York Times, Time (magazine), and broadcasts on CBS News and NBC News amplified public attention, prompting a visit by President Jimmy Carter and involvement by federal agencies including the Environmental Protection Agency and the Federal Emergency Management Agency.

The emergency response mobilized state officials such as Pennsylvania Governor Dick Thornburgh, local emergency services in Dauphin County, Pennsylvania, and federal agencies including the Nuclear Regulatory Commission and the Department of Energy. Investigations included the presidentially chartered Kemeny Commission chaired by John G. Kemeny, NRC accident evaluations, and studies by academic institutions such as Massachusetts Institute of Technology and Oak Ridge National Laboratory. Litigation and oversight proceedings involved General Public Utilities Corporation, Metropolitan Edison Company, and regulatory hearings before the Nuclear Regulatory Commission and the United States Congress, where legislators from Pennsylvania and national committees debated nuclear policy. Congressional committees, including the Senate Committee on Environment and Public Works and the House Committee on Energy and Commerce, examined safety culture, operator training, and regulatory adequacy.

Cleanup operations at Unit 2, managed by organizations including GPU Nuclear and contractors with experience from Hanford Site and Savannah River Site projects, entailed defueling, decontamination, and remediation overseen by the Nuclear Regulatory Commission and state regulators. A protracted cleanup removed irradiated fuel, shipped spent fuel to an on-site spent fuel pool and later to dry cask storage, while decontamination used techniques developed at facilities like Oak Ridge National Laboratory and contractors with ties to Bechtel Corporation and Westinghouse Electric Company. The partial meltdown site underwent entombment planning, portioned dismantlement, and long-term surveillance coordinated with the Environmental Protection Agency and the Pennsylvania Department of Environmental Protection. Economic and legal frameworks involved utility rate cases before the Pennsylvania Public Utility Commission and settlements with local governments.

Assessments by the Environmental Protection Agency, epidemiological studies by institutions including Johns Hopkins University and Centers for Disease Control and Prevention, and analyses in peer-reviewed journals debated potential health effects, cancer risk, and radiological exposure to populations in Dauphin County, Pennsylvania, Lancaster County, Pennsylvania, and surrounding counties. Environmental monitoring by the Nuclear Regulatory Commission and Environmental Protection Agency tracked radioisotopes similar to those characterized at Chernobyl disaster and routine releases at plants like Indian Point Energy Center for comparative purposes. Economically, the accident affected the utility finances of General Public Utilities Corporation, led to litigation involving municipalities such as Harrisburg, Pennsylvania, and influenced energy debates in the United States Congress and state legislatures over electricity markets and ratepayer impacts.

The Unit 2 accident prompted sweeping reforms at the Nuclear Regulatory Commission, new training standards influenced by the Institute of Nuclear Power Operations, emergency planning revisions coordinated with the Federal Emergency Management Agency, and changes in licensing and oversight considered by United States Congress members and committees. It shaped public perceptions captured by commentators at The New York Times, The Washington Post, and advocacy groups such as Greenpeace and influenced policy at national laboratories including Argonne National Laboratory and Sandia National Laboratories. The event informed international nuclear safety dialogues at organizations like the International Atomic Energy Agency and contributed to design, human factors, and regulatory practices applied at reactors worldwide, echoing lessons integrated into post-accident reforms at plants such as Davis-Besse Nuclear Power Station and regulatory reviews conducted after Fukushima Daiichi nuclear disaster.

Category:Nuclear accidents and incidents in the United States Category:Buildings and structures in Dauphin County, Pennsylvania