Three Mile Island, site of 1979 nuclear reactor accident, reopening to power AI

Three Mile Island, the shuttered Pennsylvania nuclear power plant that was the site of a 1979 reactor accident that remains the worst commercial nuclear power plant accident in U.S. history, is reopening to generate power for artificial intelligence.

Constellation Energy will restart Three Mile Island Unit 1, one of the facility's pressurized water reactors, for the launch of the Crane Clean Energy Center, which will generate nuclear energy purchased by Microsoft to power the company's AI data center, the companies announced on Friday.

Under the agreement between the two companies, Microsoft will purchase energy from the plant as part of its goal to help power its data centers with carbon-free energy.

"This agreement is a major milestone in Microsoft's efforts to help decarbonize the grid in support of our commitment to become carbon negative. Microsoft continues to collaborate with energy providers to develop carbon-free energy sources to help meet the grids' capacity and reliability needs," said Microsoft Vice President of Energy Bobby Hollis in a statement.

The power purchase agreement "makes sense" because it ensures a stable revenue source for the power plant while providing 24/7 emission-free electricity for the data center, Jacopo Buongiorno, professor of nuclear science and engineering at the Massachusetts Institute of Technology (MIT), told ABC News.

The move is also "further confirmation" of the economic and environmental value of using existing nuclear power plants to meet decarbonization goals in the U.S., Buongiorno said.

"Since building a new nuclear power plant can be so time consuming and expensive, extending the license of current plants or refurbishing and restarting those that have been recently shutdown is a very attractive proposition," Buongiorno said via email.

The Crane Clean Energy Center (CCEC) is expected to create 3,400 direct and indirect jobs and add more than 800 megawatts of carbon-free electricity to the grid, according to a study commissioned by the Pennsylvania Building & Construction Trades Council.

"The CCEC will support thousands of family-sustaining jobs for decades to come," said Rob Bair, president of the Pennsylvania State Building and Construction Trades Council, in a statement. "It will help make Pennsylvania a leader in attracting and retaining the types of reliable, clean energy jobs that will define the future."

Three Mile Island, located on the Susquehanna River near Harrisburg, Pennsylvania, was shuttered in 2019 for economic reasons, according to Constellation Energy. Owner Exelon Corp said in 2017 that the closing was due to lack of financial rescue from the state.

On March 28, 1979, the Unit 2 reactor core at the Three Mile Island plant partially melted down when equipment malfunctions, compounded by human operator errors, caused a water pump failure that resulted in a loss of coolant to the reactor, according to the U.S. Nuclear Regulatory Commission.

The Unit 1 reactor is adjacent to Unit 2, which was shut down after the 1979 accident and is in the process of being decommissioned by its owner, Energy Solutions, according to Constellation Energy.

Public support for the restart of Three Mile Island is strong, with residents favoring it by a more than 2-1 margin, as long as funding for the restart doesn't require increased taxes or electricity rates, according to a recent poll conducted by Susquehanna Polling & Research.

The nuclear energy industry plays a "critical role" in providing safe and reliable carbon-free energy, Pennsylvania Gov. Josh Shapiro said in a statement.

"My Administration will continue to work to cut energy costs and ensure the reliability of our energy grid so that Pennsylvanians can have access to affordable power made right here in Pennsylvania for years to come – and the Crane Clean Energy Center will help us achieve those goals," Shapiro said.