A power company is planning to restart a dormant nuclear reactor at Pennsylvania's Three Mile Island nuclear generating station to help meet the power demands of high-tech data centers.Constellation Energy announced Friday it planned to bring the Unit 1 reactor at Three Mile Island back into operation and keep it running for decades.Microsoft has signed a 20-year agreement to buy power from Constellation's operation. It plans to use the energy to make its data centers in the region more environmentally friendly.TMI-1 was not damaged in the accident that damaged the power station in March of 1979.But the partial meltdown of TMI-2, the second reactor on the site, was the most serious nuclear accident in the history of U.S. commercial nuclear power. The reactor core overheated when its feed water pumps failed.The incident contributed to a nationwide slowdown in new reactor construction and caused regulators to tighten safety requirements on nuclear power. The undamaged TMI-1 was kept offline until 1985, then shut down again in 2019 because it was not economically feasible to keep the plant running.Now, Constellation is planning to invest to bring TMI-1's systems back up to operating readiness, which will involve overhauls of the reactor's cooling systems, turbines and power transformers.RELATED STORY | Three Mile Island's Nuclear LegacyOfficials hope the restart will power not just data centers, but local economies as well."Before it was prematurely shuttered due to poor economics, this plant was among the safest and most reliable nuclear plants on the grid, and we look forward to bringing it back with a new name and a renewed mission to serve as an economic engine for Pennsylvania," said Constellation's CEO Joe Dominguez.Restarting the reactor will still be subject to local and federal approvals. The reactor would go back into service in 2028 and continue to provide power through at least 2054, Constellation said.