Constellation Energy and Microsoft have agreed to reopen the Three Mile Island Unit 1 nuclear reactor, adding a new source of carbon-free electricity to offset the power demands of Microsoft’s expanding network of data centers, Constellation announced Friday.
The 20-year purchase agreement would restore operations at the Three Mile Island plant, the site of the 1979 meltdown of Unit 2 in the worst nuclear accident in U.S. history. Unit 1 was closed in 2019 for economic reasons, Constellation said, principally competition from cheaper natural gas-fired and renewable power.
Constellation aims to have Three Mile Island Unit 1 ready to restart in 2028, after repairs and renovation of the plant’s turbine, generator, main power transformer, and cooling and control systems. It also needs approval from the Nuclear Regulatory Commission.
It will be renamed the Crane Clean Energy Center after Chris Crane, the late CEO of Constellation’s former parent company and a nuclear industry leader.
“Powering industries critical to our nation’s global economic and technological competitiveness, including data centers, requires an abundance of energy that is carbon-free and reliable every hour of the day, and nuclear power plants are the only energy source that can consistently deliver on that promise,” Constellation President and CEO Joe Dominguez said in a statement.
Bobby Hollis, Microsoft’s vice president for energy, called the agreement a “major milestone” as it tries to boost its computing power while still becoming “carbon negative.”
“Microsoft continues to collaborate with energy providers to develop carbon-free energy sources to help meet the grids’ capacity and reliability needs,” Hollis said.
The restart won support from Pennsylvania Gov. Josh Shapiro (D) and Bart Shellenhamer, the board of supervisors chair in Londonderry Township, Pennsylvania, where the plant is located. Both praised the jobs impact of reopening the plant, which employed more than 600 full-time workers with an annual payroll of about $60 million before closing five years ago, according to Constellation.
The agreement between Microsoft and Constellation to restart a large nuclear plant is another mark of the transformational changes that are rattling the electricity sector. Regional grid operators are wrestling with the challenges of maintaining the critical balance of power supply and demand as fossil fuel plants are replaced by carbon-free electricity sources.
Stress on electric grids is set to ramp up as artificial intelligence platforms require more computing power from digital data centers. The expected energy needs to fuel AI, cryptocurrency, car charging and U.S.-based manufacturing are leading to forecasts for sharply higher electricity demand.
Nuclear power remains contentious in some areas of the United States. Still, efforts to incentivize zero-carbon nuclear technology enjoys bipartisan support from the presidential candidates — Democrat Kamala Harris and Republican Donald Trump — along with the leadership of both parties in Congress.
But any nuclear revival comes with engineering challenges. The NRC recently announced its inspectors had found issues with steam-generating equipment at the Palisades nuclear reactor in Michigan. Florida-based Holtec International plans to restart the reactor with the help of a $1.5 billion conditional loan guarantee from the Department of Energy. It was closed two years ago.
The restart must pass a regulatory safety review. A Holtec spokesperson said the NRC’s concerns would not significantly affect the project’s budget or timetable.
