Microsoft has committed to buying the electricity from a long-dormant nuclear reactor, betting that atomic power can help feed the enormous appetite of its artificial-intelligence data centers. The plant at the center of the arrangement is Unit 1 of the former Three Mile Island station in Pennsylvania, which stopped generating power in 2019 for economic reasons and has sat idle since. Under a long-term deal, the reactor’s owner plans to refurbish the unit and bring it back onto the grid, an unusual step in an industry that has never before restarted a commercial reactor that was shut down and slated for decommissioning in the United States.
Reviving Three Mile Island Unit 1
The reactor is owned by Constellation Energy, which has said it will invest heavily to refurbish the turbine, generator, cooling systems and other equipment so the roughly 835-megawatt unit can resume operation. The company has renamed the site the Christopher M. Crane Clean Energy Center, after a former chief executive, and now lists it among its facilities under regulatory review at the Nuclear Regulatory Commission. Unit 1 is physically separate from the plant’s Unit 2, the reactor that suffered a partial meltdown in 1979 and has been permanently closed for decades. Constellation has emphasized that Unit 1 operated safely and reliably until its economic shutdown, which the company says makes reviving it more straightforward than building new capacity.
A long-term deal built around AI power demand
The restart is anchored by a 20-year power purchase agreement with Microsoft, which has pledged to buy the plant’s output to match the electricity its operations consume. The tech company, according to the plant’s owner, is turning to nuclear power as data centers running AI models drive up demand for round-the-clock, carbon-free electricity. Data centers are among the fastest-growing sources of power consumption. The International Energy Agency has projected in its electricity analysis that global demand from data centers, AI and cryptocurrency could rise sharply over the second half of the decade, straining grids in regions where server farms cluster. Nuclear plants appeal to large technology buyers because they run at high output nearly all the time, unlike wind and solar, which vary with weather and time of day.
Where the restart stands with regulators
Bringing a retired reactor back is not a simple matter of flipping a switch. Constellation must clear a series of federal reviews, including license amendments and an environmental assessment, before it can load fuel and generate power again. Regulators have been working through those steps, with staff issuing a draft finding that the restart would have no significant environmental impact and moving toward a decision on the necessary approvals. As reporting on the project has detailed, the company has accelerated its target and now aims to have the plant back in service around 2027, ahead of an earlier 2028 estimate, provided the regulatory milestones are met. The company also secured arrangements to connect the revived unit to the regional transmission system.
What the revival means for the grid and the region
Beyond the corporate arrangement, the restart carries weight for Pennsylvania and the wider mid-Atlantic grid. Bringing an 835-megawatt reactor back online adds a substantial block of always-on, carbon-free electricity to a region where demand has been rising and some older fossil-fueled plants have retired. Constellation has said the project would create hundreds of permanent jobs and thousands of temporary construction positions, along with tax revenue for the surrounding community, while the reactor’s output flows into the regional transmission network that serves millions of customers. Because the electricity feeds the shared grid rather than a private wire, the plant effectively frees up other supply even as Microsoft pays for power equal to its own consumption. Grid operators have warned for several years that the rapid buildout of data centers, electric vehicles and electrified heating could outpace new generation, and reviving an existing nuclear unit is one way to add capacity without the long timelines of building a plant from the ground up. Whether the model spreads will depend on how smoothly this first attempt clears its regulatory and engineering hurdles.
What the deal signals for nuclear power
The Three Mile Island revival has drawn attention because it points to a possible new lifeline for existing nuclear plants at a moment when electricity demand is climbing after years of relatively flat growth. Reopening a mothballed reactor is cheaper and faster than constructing one from scratch, and the model of pairing a single large customer with a dedicated generator has prompted other technology firms to explore similar arrangements, from restarting old plants to backing next-generation reactor designs. Supporters argue that nuclear power offers steady, low-carbon electricity that can underpin energy-hungry computing without adding greenhouse gases. Critics raise concerns about cost, long-term waste storage and whether scarce clean power should be reserved for a single corporate buyer rather than the broader grid. What is clear is that the surge in computing demand has given a fresh commercial rationale to a technology that had been in slow retreat, and the outcome at the Pennsylvania site is being watched closely as a test of whether that rationale holds.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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