stated it would cost $1.2 billion over nearly 60 years to completely decommission Unit 1. Unit 1 closed on September 20, 2019. In 2022, Unit 1 was transferred to Constellation Energy following separation from Exelon. Unit 2 was also transferred to TriArtisan ES Partners, LLC - following their acquisition of EnergySolutions. Decommissioning Following the TMI-2 accident in 1979, approximately 99% of the fuel and damaged core debris was removed from the reactor vessel and associated systems and shipped to the Idaho National Laboratory near Idaho Falls, Idaho. Since 1993, when the initial cleanup of the plant was completed, TMI-2 has been in a condition known as Post Defueling Monitored Storage (PDMS) and is under constant monitoring to ensure the plant's safety and stability. The cost of decommissioning a closed nuclear reactor and related structures at Three Mile Island is estimated at $918 million. Seismic risk The Nuclear Regulatory Commission's estimate of the risk each year of an earthquake intense enough to cause core damage to the reactor at Three Mile Island was 1 in 25,000, according to an NRC study published in August 2010. See also Chernobyl disaster Fukushima Daiichi nuclear disaster Notes References External links Three Mile Island page on the operator's website Three Mile Island – Three Mile Island Alert Energy infrastructure completed in 1974 Energy infrastructure completed in 1978 Nuclear power plants in Pennsylvania Three Mile Island accident Buildings and structures in Dauphin County, Pennsylvania Towers in Pennsylvania Nuclear power stations using pressurized water reactors Susquehanna River FirstEnergy 1974 establishments in Pennsylvania Former nuclear power stations in the United States