Constellation Energy Corp has confirmed an earlier than expected restart of the former Three Mile Island nuclear power plant in Pennsylvania.

Constellation, alongside Microsoft executives and local officials announced that the site, now known as the Crane Clean Energy Center “could restart as early as 2027, with the approval of an early interconnection request by grid operator PJM and significant progress made on hiring, reactor operator training and major equipment purchases.”

The former Three Mile Island power plant was at the centre of the worst nuclear accident in US history.

Nuclear power plant

On 28 March 1979, a partial nuclear meltdown occurred after an accident involving the the TMI-2 reactor, after a number of equipment failures.

Official cleanup measures of the TMI-2 reactor ended in 1993.

The plant’s TMI-1 reactor was restarted in 1985 (as it was not involved in the incident), but it was closed in 2019 due to operating losses.

Now Constellation has confirmed the TMI-1 reactor is expected to go back into service in 2027 as part of a September 2024 deal with Microsoft to power its data centres.

“Today we begin a new chapter for reliable, emissions-free nuclear energy, returning thousands of good jobs and billions in economic opportunities for Pennsylvania families and businesses,” said Joe Dominguez, Constellation president and CEO.

“With PJM’s action, Microsoft’s historic investment, and strong support from Governor Shapiro, elected officials and members of this community, we’re on track to make history ahead of schedule, helping America achieve energy independence, supercharge economic growth, and win the global AI race,” said Dominguez.

“My Administration has worked closely with Constellation and PJM on the Crane Clean Energy Center since 2023 in order to get this new generation online as quickly as possible, ensure the reliability of our grid, and cement the Commonwealth’s energy future,” said Governor Josh Shapiro. “This restart will safely take advantage of existing infrastructure while creating thousands of energy jobs and strengthening Pennsylvania’s legacy as a national energy leader.

“As Microsoft continues its path to become a carbon negative company, this agreement brings a significant supply of new, reliable, carbon-free electricity back to the PJM power grid,”added Bobby Hollis, VP of Energy, Microsoft. “This will help address the grids’ capacity and reliability needs in the regions we operate.”

Crane Clean Energy Center

Constellation said it continues to make strong progress toward the safe and efficient restart of the Crane Clean Energy Center.

The facility is now more than 64 percent staffed, with nearly 400 full-time employees on board and 58 additional hires with start dates in the coming weeks.

Significant technical milestones have also been reached, including the successful inspection of the plant’s diesel generator, steam generator, main generator, turbines, and other major systems.

An independent study found that Constellation’s $1.6 billion investment to restart the Crane Clean Energy Center is expected to:

• Create 3,400 direct and indirect jobs
• Add $16 billion to Pennsylvania’s GDP
• Generate more than $3 billion in state and federal tax revenue

Data centre power

Microsoft is not the only tech giant utilising nuclear power for its data centres, and Constellation’s 20-year power purchase agreement with Microsoft shows the need for nuclear to power big tech’s AI expansions.

Earlier this month Meta Platforms and Constellation had signed “a 20-year power purchase agreement (PPA) for the output of the Clinton Clean Energy Center to support Meta’s clean energy goals and operations in the region with 1,121 megawatts of emissions-free nuclear energy.”

Also earlier this month it was announced that Talen Energy would “provide carbon-free energy from Talen’s Susquehanna nuclear power plant (in Pennsylvania) to Amazon Web Services data centres in the region

In October 2024 AWS also signed three agreements on developing small modular reactors, which are an advanced kind of nuclear reactor with a smaller physical footprint, allowing them to be built closer to the grid. There are no SMRs in the US, at the moment.

Also in October 2024, Alphabet’s Google signed what it called the world’s first corporate agreement to buy power from multiple small modular nuclear reactors (SMRs).