(FILES) Steam rises out of the Three Mile Island nuclear plant, with the operational plant run by Exelon Generation, south of Middletown, Pennsylvania, on March 26, 2019. The plant, site of the worst nuclear accident in US history, is to restart operations in a deal to sell power to Microsoft, Constellation Energy said on September 20, 2024. The firm announced the 20-year deal would involve the restart of the Unit 1 reactor, "which operated at industry-leading levels of safety and reliability for decades before being shut down for economic reasons exactly five years ago today." The Unit 1 reactor was not involved in the March 28, 1979, partial nuclear meltdown. (Photo by Andrew CABALLERO-REYNOLDS / AFP) (Photo by ANDREW CABALLERO-REYNOLDS/AFP via Getty Images)