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Projects & Facilities

C Reactor

Image of the C Reactor - circa 2022
Photo of the C Reactor circa 2022.


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.

In 1998 C Reactor became the first of Hanford’s nine plutonium production reactors to be placed in Interim Safe Storage, commonly referred to as “cocooning.” Reactor cocooning is designed to keep the reactor in a safe configuration to allow the radiation levels to decay to a point where the reactor can be safely dismantled and disposed of on Hanford’s Central Plateau. The cocooning showed the promise of several new technologies aimed at reducing worker exposure to radiation, lowering costs associated with Hanford’s older reactors, and accelerating the Hanford cleanup mission.

C Reactor was also the first reactor to undergo a “check-up" after it had been cocooned. All reactors that are cocooned are entered by radiation technicians once every 10 years to confirm that no contamination is escaping the sealed reactor core, and that nothing is entering the building from the outside. If the cocoon performs as intended, it could be in place for up to 75 years.

C Reactor sits adjacent to B Reactor in Hanford’s 100 Area. While the B Reactor is preserved as a National Historic Landmark, C Reactor’s waste burial grounds have been remediated, its support and auxiliary buildings have been removed, and all that remains of the facility is the deactivated reactor core inside the sealed cocoon.

Last Updated 10/26/2023 8:32 AM