Three Mile Island Nuclear Generating Station


Three Mile Island Nuclear Generating Station, is a shut-down nuclear power plant on Three Mile Island in Pennsylvania, US, on the Susquehanna River just south of Harrisburg. It has two separate units, Unit 1 and Unit 2 .
The plant was the site of the most significant accident in United States commercial nuclear energy when, on March 28, 1979, TMI-2 suffered a partial meltdown. According to the U.S. Nuclear Regulatory Commission report, the accident resulted in no deaths or injuries to plant workers or in nearby communities. Follow-up epidemiology studies did not find causality between the accident and any increase in cancers. One work-related death has occurred on-site during decommissioning.
The reactor core of TMI-2 has since been removed from the site, but as of 2009 the site has not been fully decommissioned. In July 1998, Amergen Energy agreed to purchase TMI-1 from General Public Utilities for $100 million.
The plant was originally built by General Public Utilities Corporation, later renamed GPU Incorporated. The plant was operated by Metropolitan Edison Company, a subsidiary of the GPU Energy division. In 2001, GPU Inc. merged with FirstEnergy Corporation. On December 18, 2020, FirstEnergy transferred Unit 2's license to EnergySolutions' subsidiary, TMI-2 Solutions, after receiving approval from the NRC.
Exelon was operating Unit 1 at a financial loss since 2015. In 2017, the company said it would consider ceasing operations at Unit 1 because of high costs unless there was action from the Pennsylvania government. Unit 1 officially shut down at noon on September 20, 2019.
Unit 1 decommissioning was expected to be completed in 2079 and would have cost $1.2 billion, but in September 2024, Constellation Energy, the owner of the Unit, announced plans to invest $1.6 billion to bring the facility back online. The plant is expected to resume operations in 2028 as the Crane Clean Energy Center. The entirety of the plant's energy output will be sold to Microsoft Corporation. Microsoft entered into a 20-year agreement to purchase as much electricity as possible from the plant, which will support the company’s growing energy needs for its expanding network of data centers.
Unit 2, which has been dormant since the accident in 1979, is expected to close in 2052.

Emergency zones and nearby population

The NRC defines two emergency planning zones around nuclear power plants: a plume exposure pathway zone with a radius of, concerned primarily with exposure to, and inhalation of, airborne radioactive contamination, and an ingestion pathway zone of about, concerned primarily with ingestion of food and liquid contaminated by radioactivity.
The 2010 U.S. population within of Three Mile Island was 211,261, an increase of 10.9 percent in a decade, according to an analysis of U.S. Census data. The 2010 U.S. population within was 2,803,322, an increase of 10.3 percent since 2000. Cities within 50 miles include Harrisburg, York, and Lancaster.

Electricity production

During its last full year of operation in 2018, Three Mile Island generated 7,355 GWh of electricity. In that same year, electricity from nuclear power produced approximately 39% of the total electricity generated in Pennsylvania, with Three Mile Island Generating Station contributing approximately 4% to the statewide total generation. In 2021 electrical generating facilities in the state of Pennsylvania generated approximately 241 TWh of total electricity.
YearJanFebMarAprMayJunJulAugSepOctNovDecAnnual
2001598,586558,484617,640540,691309,720427,684591,460588,699562,563130,2080491,0285,416,763
2002628,077569,814631,547606,413622,103575,870609,816609,997595,565619,838610,530633,9497,313,519
2003631,984572,521631,971605,628624,685597,862610,219609,588592,306309,494---
418,8156,197,031------------
2004628,992592,136630,817606,796595,895590,383593,006609,964594,931628,330606,727595,2577,273,234
2005634,556574,716633,072603,671622,371590,245606,729606,110590,523431,976227,852633,6406,755,461
2006634,770574,064629,263604,524620,189592,955607,024610,066598,981626,894533,567594,7317,227,028
2007633,504571,450628,411604,807616,716591,972610,453608,744591,535387,453173,525626,7246,645,294
2008634,479593,989631,886606,166622,685593,699611,785615,991591,191620,414610,566632,2477,365,098
2009632,599571,398627,785601,665613,866593,159610,822607,848593,508438,962---
05,888,909------------
2010132,230564,608571,255599,167558,978586,421604,409594,950568,086621,174607,344625,1286,633,750
2011625,004564,025622,273595,735593,238589,577599,464603,021563,240453,96882,899626,3856,518,829
2012629,556589,831624,849608,509613,382596,485610,350417,839478,175624,454614,324630,5037,038,257
2013629,685570,617629,618606,648621,454595,263610,260614,906599,698536,50461,179583,2366,659,068
2014629,732534,623629,723608,793614,408614,413613,793616,228598,666625,480610,804630,9827,327,645
2015631,581569,154629,454607,974490,525594,154577,760613,283593,923576,59484,416629,2236,598,041
2016630,503587,527627,463607,175620,556588,999599,964609,354593,371622,807607,486387,4477,082,652
2017629,440569,389629,237604,756622,133594,829610,064615,158336,473404,367612,290632,1246,860,260
2018633,552571,419630,787607,853614,580594,845611,421609,506594,668623,620611,295632,2787,335,824
2019632,206570,764629,016604,853617,709594,819608,513605,781350,5350---
5,214,196-------------

Three Mile Island Unit 1

The Three Mile Island Unit 1 is a pressurized water reactor designed by Babcock & Wilcox with a net generating capacity of 819 MWe. The initial construction cost for TMI-1 was, equal to $ billion in 2018 dollars. Unit 1 first came online on April 19, 1974, and began commercial operations on September 2, 1974. TMI-1 was licensed to operate for 40 years from its first run, and in 2009, its license was extended by 20 years, which means it could have operated until April 19, 2034.
TMI-1 had a closed-cycle cooling system for its main condenser using two natural draft cooling towers. Makeup water was drawn from the river to replace the water lost via evaporation in the cooling towers. Once-through the cooling towers, river water was used in the service water system, cooling auxiliary components and removing decay heat when the reactor was shut down. On February 17, 1979, TMI-1 went offline for refueling. It was brought back online on October 9, 1985, after public opposition, several federal court injunctions, and some technical and regulatory complications – more than six years after it initially went offline.
Unit 1 was scheduled to be shut down by September 2019 after Exelon announced they did not receive any commitments for subsidies from the state, rendering Exelon financially unable to continue operating the reactor. TMI-1 was shut down on September 20, 2019, but may be brought back. The CEO of Constellation Energy, the owner of Unit 1, says the reactor is in "excellent shape," and estimated that it would go online within three years of committing to a restart. Constellation is conducting tests for a potential decision to reopen.