Constellation says it will restart Three Mile Island Unit 1 this decade

Constellation on Friday announced it plans to restart the Three Mile Island Unit 1 nuclear reactor in Londonderry Township, Pa., by 2028 and extend its operating license through “at least” 2054.

Constellation announced the plan in a press release, in which it also said it has signed a 20-year power purchase agreement with Microsoft Corp., under which the Redmond, Wash., software titan will buy energy from the reopened plant.

Three Mile Island 1 will also be renamed the Crane Clean Energy Center, Constellation said in the release, after the late Christopher Crane, former president and CEO of Exelon, who died in April.

Three Mile Island Unit 1 shut down in 2019 and is separate from Three Mile Island Unit 2, which shut down in 1979 after a partial core meltdown.

Citing the economic inviability of the plant, Constellation shut Three Mile Island Unit 1 down in 2019 and put it into decommissioning on Sept. 26 of that year. Among the state and federal regulatory approvals the company will need to restart the plant is permission from the Nuclear Regulatory Commission to move the plant out of decommissioning.

Holtec International is attempting a similar regulatory reversal with NRC to reopen the Palisades Nuclear Generating Station in Michigan. The commission has accepted Holtec’s application for regulatory relief in February and has said it could finish reviewing the application in May.

At Three Mile Island, Constellation had planned a passive approach to decommissioning: keeping the reactor in long-term storage, or SAFESTOR, until 2079 so that radioactivity levels would drop substantially before the company began taking apart the plant. 

In the interim, Constellation said in a 2023 decommissioning status report, the company would have had to spend about $122 million to manage Three Mile Island Unit 1’s spent fuel through 2041, more than 30 years before the heavy lifting of decommissioning would have started.

Overall, Constellation estimated, it would have cost more than $1 billion to completely decommission Three Mile Island Unit 1.