Nuclear

Three Mile Island nuclear plant is reopening to help power Microsoft data centers

Three Mile Island was shut down in 2019. Owner Exelon decided to end operations after a financial rescue package did not come from Pennsylvania legislators.
Three Mile Island nuclear plant is reopening to help power Microsoft data centers
Three Mile Island Nuclear Power Plant (Credit: DOE)

Pennsylvania’s Three Mile Island Unit 1 is getting a new lease on life with the help of new partner Microsoft.

Constellation announced the signing of a 20-year power purchase agreement with Microsoft that will pave the way for the launch of the Crane Clean Energy Center (CCEC) and restart of the 835 MW nuclear unit at Three Mile Island.

Under the agreement, Microsoft will purchase energy from the re-opened plant as part of its goal to help match the power its data centers in PJM use with carbon-free energy.

Three Mile Island was shut down in 2019. Owner Exelon decided to end operations after a financial rescue package did not come from Pennsylvania legislators.

In 1979, Three Mile Island was at the center of the worst nuclear power accident in U.S. history. The TMI Unit 2 reactor, located approximately 10 miles southeast of Harrisburg, Pa., operated for approximately six months before suffering reactor core damage on March 28, 1979. Subsequently, about 99% of the fuel and damaged reactor core material was removed and shipped to the Department of Energy’s Idaho National Laboratory, and in 1993 the plant was placed in a Post-Defueling Monitored Storage status.

No one was injured in the accident, but it left a lasting mark on the nation’s attitude toward nuclear power.

The Unit 1 reactor is located adjacent to TMI Unit 2, which is in the process of being decommissioned by its owner, Energy Solutions. TMI Unit 1 is a fully independent facility, and its long-term operation was not impacted by the Unit 2 accident, Constellation said.

To prepare for the restart, investments will be made to restore the plant, including the turbine, generator, main power transformer and cooling and control systems. Restarting a nuclear reactor requires U.S. Nuclear Regulatory Commission approval following a comprehensive safety and environmental review, as well as permits from relevant state and local agencies. Additionally, through a separate request, Constellation will pursue license renewal that will extend plant operations to at least 2054. The CCEC is expected to be online in 2028.

According to a recent statewide poll, conducted by Susquehanna Polling & Research and cited by Constellation, Pennsylvanians favor restarting the plant by a more than 2-1 margin. The same independent poll found that 70% of state residents support the continued use of nuclear energy as a source of carbon-free energy.

Constellation purchased TMI Unit 1, in 1999. Before it was retired for economic reasons in 2019, the plant had a generating capacity of 837 MW. In its last year of operation, the plant was producing electricity at maximum capacity 96.3% of the time. The plant had an annual payroll of about $60 million and employed more than 600 full-time workers, in addition to the roughly 1,000 craftspeople that supported the plant’s biennial refueling outages.

The plant will be renamed the Crane Clean Energy Center in honor of Chris Crane, who was CEO of Constellation’s former parent company. Crane, who passed away in April 2024, was an advocate for America’s commercial nuclear power industry. Crane helped build the Institute for Nuclear Power Operations (INPO) and served on the boards of the Nuclear Energy Institute (NEI) and the World Association of Nuclear Operators (WANO).

A group including Microsoft, BlackRock, Global Infrastructure Partners (GIP) and MGX this week announced the formation of the Global AI Infrastructure Investment Partnership (GAIIP) to make investments in data centers and the energy infrastructure to power them.

The partnership will initially seek to unlock $30 billion of private equity capital over time from investors, asset owners and corporate partners, which in turn would mobilize up to $100 billion in total investment potential when including debt financing.

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