WASHINGTON (Reuters) -The Trump administration said on Tuesday it has loaned Constellation Energy Corp ( CEG ) $1 billion to restart its nuclear reactor at a Pennsylvania plant formerly known as Three Mile Island. 

Constellation signed a deal in late 2024 with Microsoft ( MSFT ) to restart the 835-megawatt reactor, which shut in 2019, and which would offset Microsoft's ( MSFT ) data center electricity use. The other unit at the plant, renamed the Crane Clean Energy Center, shut in 1979 after an accident that chilled the nuclear power industry.

U.S. power demand is now rising for the first time in two decades on technologies including artificial intelligence. Nuclear energy, which is virtually carbon-free, has become an option for technology companies with uninterrupted power needs and climate pledges. Critics point out that the U.S. has failed to find permanent storage for radioactive waste.  

Greg Beard, head of the Energy Department's Loan Programs Office, or LPO, said the restart would support the PJM regional grid. "This type of energy is important because it's large, stable, affordable base load power," Beard told reporters.

Constellation said the loan will help it lower the cost of financing and leverage private investment to restore power to the grid.  

The LPO has more than $250 billion in capital, and "a large portion of that we expect to be deployed to help reinvigorate the large-scale nuclear reactor development," Beard said. Energy Secretary Chris Wright said this month that the bulk of the LPO money would go to nuclear projects.    

Constellation in June had moved up the timeline to restart the reactor by about a year to 2027 after PJM fast-tracked its review process to connect the project to the grid. 

Constellation said it has hired hundreds of workers, completed infrastructure inspections and ordered major equipment for the reactor. It will need to revamp cooling towers, install a main power transformer among other equipment, and re-fuel before producing electricity.

It was the first time the LPO declared that a company had met all conditions for a loan and closed it at the same time, Beard said. Constellation is guaranteeing the loan, he said, and that loan structure would protect taxpayers if the project does not succeed.  

Constellation is an "investment-grade" established nuclear operator that could have gotten a bank loan without the government's help, Beard said. "But we want to show support for affordable, reliable, stable, secure energy in the U.S., as directed by President (Donald) Trump." 

The plant also needs U.S. Nuclear Regulatory Commission and water-related permitting, Constellation said this year.