The operator of the Three Mile Island nuclear power plant will reopen the facility to generate electricity for Microsoft Corp. data centers.

Constellation Energy Generation LLC, the largest renewable energy producer in the U.S., announced the initiative today. The company will supply power from Three Mile Island to Microsoft under a newly signed 20-year contract. Before reopening the plant, Constellation will carry out wide-ranging renovations and secure fresh regulatory approvals.

The company plans to supply Microsoft with power from the Three Mile Island plant’s Unit 1 reactor. Unit 2, a reactor housed in an immediately adjacent facility, experienced a partial nuclear meltdown in 1979. The incident was the worst nuclear power plant accident in U.S. history.

The Unit 1 reactor earmarked for Microsoft was not affected by the accident. The system continued operating until 2019, when Constellation retired it “prematurely for economic reasons.” The company’s new 20-year deal with Microsoft will see the facility that houses Unit 1 reopen as the Crane Clean Energy Center. 

“This agreement is a major milestone in Microsoft’s efforts to help decarbonize the grid in support of our commitment to become carbon negative,” said Bobby Hollis, Microsoft’s vice president of energy. “Microsoft continues to collaborate with energy providers to develop carbon-free energy sources to help meet the grids’ capacity and reliability needs.”

According to Bloomberg, Constellation will spend $1.6 billion to renovate the Three Mile Island plant. The company plans to upgrade the facility’s cooling and control systems as well as its turbine, generator and main power transformer. The upgrade will be followed by a safety and environmental review.

Before it reopens, the Crane Clean Energy Center will have to be approved by the U.S. Nuclear Regulatory Commission. Constellation will also require permits from state and local agencies. The reopening is expected to be supported by tax credits and other federal subsidies from the Inflation Reduction Act.

Constellation plans to bring the plant online in 2028. The facility is expected to generate 835,000 megawatts of electricity, which is enough to power more than 800,000 homes. Constellation hopes to operate it through at least 2054.

The plant will help Microsoft meet the growing power requirements of its cloud data centers. The facilities’ rising electricity usage is driven in part by the large number of graphics processing units that they host. Microsoft reportedly hopes to deploy 1.4 million GPUs in its data center network by year’s end.

It’s estimated that Nvidia Corp.’s H100 graphics card, which was its flagship data center chip until last year, consumes more than 3,700 kilowatt-hours of electricity per year. That’s equivalent to a low double-digit percentage of a typical home’s annual power usage. The successor to the H100, the Blackwell B200, consumes even more power.

Alongside Nvidia chips, Microsoft is deploying internally designed artificial intelligence chips in its data centers. The company uses liquid cooling technology to dissipate the heat generated by those processors. Microsoft has developed custom cooling systems, dubbed sidekicks by its engineers, that can attach directly to a server rack and circulate cold liquid through the hardware inside. 

Photo: Constellation Energy