Three Mile Island‑1 Closed at Age 45

WNISR, 22 September 2019

The Three Mile Island (TMI) Unit 1 was closed on 20 September 2019, the plant owner Exelon Corp. announced. The 45-year old 819 MW Pressurized Water Reactor (PWR), located near Middletown in Pennsylvania was connected to the grid on 19 June 1974. The closure brought to an end nuclear generation at the site where Unit 2 in 1979 suffered a partial core-melt accident.

“Today we celebrate the proud legacy of TMI Unit 1 and the thousands of employees who shared our commitment to safety, operational excellence and environmental stewardship for nearly five decades,” said Bryan Hanson, Exelon’s senior vice president and chief nuclear officer stated.

Although in 2009 the reactor had been granted a Nuclear Regulatory Commission (NRC) 20-year license extension to operate until 2034, Exelon announced on 8 May 2019 that TMI-1 would permanently close by 30 September 2019. In August 2015, TMI-1 did not clear the Pennsylvania New Jersey Maryland Interconnection LLC (PJM) electricity-capacity auction for the 2018-19 planning year, and in 2017 Exelon warned that failure to approve subsidies by the Pennsylvania legislature before 1 June 2019 would lead to the reactor’s closure. As of 20 September 2019, no such legislation has been passed.

Forty years ago TMI-2 suffered the most serious accident in U.S. commercial nuclear power plant operating history when its core partially melted on 28 March 1979. In closing down TMI-1, Exelon stressed that it had never owned TMI-2 that suffered the accident. The official President’s Commission report on the causes of the accident concluded that a combination of personnel error, design deficiencies, and component failures was responsible. TMI-1 was shut down following the accident but permitted to restart in 1985 against objections from the local community, non-governmental organizations and a Commissioner of the NRC.