MIDDLETOWN, Pa. (WHTM) – The clouds of steam that billowed over Three Mile Island for more than 40 years will slowly begin to fade Friday.
TMI Unit 1 will cease operation at noon, Exelon Generation spokesman Dave Marcheskie said.
Exelon announced in 2017 that it would shut down Three Mile Island unless the state stepped in with a financial rescue.
In May, the company announced was moving forward with the shutdown by Sept. 30, saying it was clear a state policy solution would not be enacted in time to reverse the “premature retirement” of the plant. TMI had a fuel purchasing deadline of June 1.
TMI Unit 1 is licensed to operate until 2034. The nuclear power plant has about 635 employees and contributes about $1 million to Londonderry Township in local real estate taxes.
Exelon in April filed decommissioning plans for TMI after the plant’s final shutdown.
In the federally required Post Shutdown Decommissioning Activities Report to the Nuclear Regulatory Commission, Exelon said used nuclear fuel will be transitioned into a spent fuel pool then moved to dry cask storage by the end of 2022.
Facility staffing will decrease in three phases from 675 to 50 full-time employees by 2022, and dismantling of the station’s cooling towers and other large components will begin in 2074, Exelon said.
Spent fuel pools are where spent fuel assemblies are kept under at least 20 feet of water to shield anyone near the pool from radiation. The assemblies are moved into the water pools from the reactor along the bottom of water canals so that the spent fuel is always shielded to protect workers, according to the NRC’s website.
Dry cask storage allows spent fuel that has already been cooled in the spent fuel pool for at least one year to be surrounded by inert gas inside a container. The containers, or casks, are typically steel cylinders either welded or bolted closed to confine the spent fuel, according to the NRC. Each cylinder is surrounded by additional steel, concrete, or other material to shield workers and the public from radiation.
TMI’s used nuclear fuel in dry cask storage will be protected in a hardened facility with multiple layers of structural, human and electronic security, Exelon said.
TMI’s Unit 2 has not operated since the 1979 accident that severely damaged the reactor core.