Three Mile Island nuclear power plant could be brought back online earlier than planned

The Three Mile Island (TMI) nuclear power plant, which is set to supply power to Microsoft’s data centers, could go online a year earlier than planned. TMI, specifically its Reactor 1, is slated to power Microsoft’s AI data centers in the region in the future. Constellation, the largest provider of nuclear energy in the U.S., has agreed to a 20-year power purchase agreement (PPA) with Microsoft, which was signed last September. Under this agreement, Microsoft will purchase the entire capacity of the reactor, which has an output of 837 megawatts.

The reactor, located near Harrisburg, Pennsylvania, was originally shut down in 2019 because it lacked the necessary subsidies to compete with cheaper energy alternatives. Constellation CEO Joe Dominguez admitted that the shutdown was a “mistake” but emphasized that they are now “looking to the future.” The project will be renamed the “Crane Clean Energy Center” after its recommissioning.

An ambitious schedule and considerable investments

The recommissioning of TMI Unit 1 is a demanding undertaking that requires extensive renovation work on the turbine, generator, transformer, as well as cooling and control systems. The estimated costs for this restart amount to approximately 1.6 billion US dollars. The power plant was originally scheduled to be commissioned in 2028.

However, at a press conference in June, Constellation CEO Joe Dominguez expressed confidence that the plant could be operational as early as 2027. This statement suggests that Constellation is exceeding the current schedule for the renovation work, which projects completion in 2028. Before the reactor can begin operation, it still requires approval from the U.S. Nuclear Regulatory Commission (NRC). Support from the regional grid operator PJM is also crucial; PJM has introduced a new fast-track procedure for grid connection, which is intended to accelerate the connection of the Crane Clean Energy Center.

The growing energy demand of data centers

The return of Three Mile Island Unit 1 is part of a growing trend where companies in the data center sector are seeking long-term nuclear energy supply contracts. This trend is driven by the seemingly insatiable energy demand of AI technologies. Microsoft is just one of several large technology companies that have focused on nuclear power as an energy source in recent years. For example, in June, Constellation signed another 20-year PPA with Meta for the entire output of its 1.1 gigawatt (GW) Clinton Clean Energy Center in Illinois, which is expected to begin operation in June 2027. Google is also relying on nuclear energy as part of its power supply and is investing in Small Modular Reactors (SMRs), which, however, will still require several years to reach mass production readiness. Meanwhile, little is heard about how companies are dealing with nuclear waste and the high construction costs. At least here, the US company Palantir is now trying to achieve cost reduction in the construction of nuclear power plants with the help of AI.