Three Mile Island 1

Basic Facts:

  • Location: Middletown, Pennsylvania
  • Owner: Exelon Corporation
  • Operator: Exelon Nuclear
  • Construction Cost: $2.6B (2018$)
  • Plant Output: 840 MW
  • Property Size: 810 acres
  • Status: Closure Announced
  • Employees: 675
  • Expected Shut Down Date: 2019
  • Current DTF Balance: $650M (2018$)
  • DTF Balance Prior to Decommissioning: $930M (2018$)
  • Decommissioning Cost Estimate: $490M (2018$)
  • Spent Nuclear Fuel on Site: 667 metric tons
Three Mile Island 1 Photojpg


Three Mile Island Unit 1 is an 820MW pressurized water reactor located on the shores of the Susquehanna River. Unit 1 construction began in 1968 and the facility began commercial operations in 1974. Unit 1 received an initial operating license of 40-years. In 2009, the NRC granted Unit 1 a twenty-year license extension thereby extending its licensed operational life to 2034.

In 2017, plant owners announced their intention to close Unit 1 in 2019 unless plant economics became more favorable. In 2018, the Pennsylvania General Assembly’s Nuclear Caucus released a bicameral report more fully exploring this issue.


The Three Mile Island Generating Station is located within Dauphin County, Pennsylvania. As of 2016:

  • Population: 280,000
  • Per Capita Annual Income: $49,000
  • Unemployment rate (not seasonally adjusted): 4.5%

The annual payroll at the Three Mile Island Generating Station is approximately $60M and in 2017 the plant contributed $1M in property tax payments.

Contact Information

Economic Development Administration Representative:

  • Christopher Casper, Philadelphia Regional Office, t: (215) 597-1074, e: [email protected]

University Center

Nuclear Regulatory Commission Contact

Unless specific costing information has been provided, decommissioning costs were derived from 2017 Decommissioning Funding Status Report.
Information herein obtained from public sources. Corrections are welcome and may be directed to [email protected].

Additional Information

Massive tax cut sought for TMI, as Exelon says closed nuclear power station isn’t worth a dime

December 3, 2020

Massive tax cut sought for TMI, as Exelon says closed nuclear power station isn’t worth a dimeA year after the facility was de-activated, Exelon Generation Co. is seeking a massive property tax cut for its Three Mile Island nuclear power station. In fact, the company is arguing in an appeal filed in Dauphin County Court […]

Read More

Who’s paying to decommission Three Mile Island?

June 30, 2020
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As Three Mile Island Stops Generating Electricity, This PA Community Is Bracing For Change

September 28, 2019
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TMI shuts down, local officials predict economic hit

September 22, 2019
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Three Mile Island closes Friday

September 20, 2019
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Based on other closed plants, TMI decommissioning might be shortened

September 5, 2019
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Three Mile Island is closing. Now what?

August 21, 2019
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Farewell to Three Mile Island: A timeline of the plant’s history

August 19, 2019
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‘It Just Becomes Like a Ghost Town’: As Nuclear Plants Close in Record Numbers Across U.S., Small-Town School Districts Brace for Catastrophic Tax Losses

August 4, 2019
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‘Neighbors to a waste dump’: Public begs for earlier TMI decommissioning

August 4, 2019
Read More

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