A nuclear reactor at Three Mile Island, the site of the worst-ever nuclear incident in the United States, is set to be activated for the first time in five years after its owners secured an exclusive deal with Microsoft to sell power to the tech giant. Microsoft wants a clean energy source to fuel its AI ambitions so it has turned to the Pennsylvania site with terms agreed on a 20-year plan, commencing in 2028 once essential upgrades have been completed at Three Mile Island. The project is supported by President Biden’s climate bill but is subject to final approval from the Nuclear Regulatory Commission. Microsoft believes the time is right to land this strategic resource, given the vast computational demands of AI development and deployment, including power-hungry data centers. On Friday, site owners Constellation Energy confirmed its Unit 1 reactor, shut down since 2019, will be the source of energy for the tech giant but stressed it was fully independent of the adjacent unit responsible for the high-profile incident five decades ago. U.S.