Hanford’s C Reactor was built in the late 1940s and early 1950s, and started operations in 1952. It was the sixth reactor built at Hanford and ran for 16 years before being shut down in 1969.
C Reactor was the first of Hanford’s nine plutonium production reactors to be placed in Interim Safe Storage, commonly referred to as cocooned. Reactor cocooning was designed to keep the reactor in a safe configuration for 75 years to allow the radiation levels to decay to a point where the reactor could be dismantled and disposed of on Hanford’s Central Plateau. C Reactor was cocooned in 1998, which showed the promise of several new technologies aimed at reducing worker exposure to radiation, lowering costs associated with these older reactors, and accelerating the cleanup mission.
As C Reactor was the first reactor to be cocooned at Hanford, it was also the first to undergo a five-year annual “check-up.” All reactors that are cocooned are entered by radiation technicians once every five years to confirm that no contamination is leaving the sealed reactor core, and that nothing is entering the building from the outside. C Reactor passed both its five-year check-up in 2003, as well as its ten-year check-up in 2008.
If the cocoon continues to prevent contamination from leaking out of C Reactor while also keeping anything outside the reactor from entering it, the cocoon could be in place for up to 75 years.
The area where C Reactor sits is adjacent to the B Reactor in Hanford’s 100 Area. While the B Reactor is being preserved as a National Historic Landmark, C Reactor’s burial grounds have been remediated, its support and auxiliary buildings have been demolished and removed, and all that remains of the facility is the reactor core inside the sealed cocoon.