The world’s second full-scale nuclear reactor was the D Reactor, which was built in the early 1940s and went operational in December 1944. D Reactor ran through June of 1967 and was ultimately cocooned in 2004.
D Reactor is unique in a couple of ways. First, the reactor’s control room is the property of the Smithsonian Institution in Washington, D.C., and has occasionally been part of an exhibit and placed on display at the museum. Second, the D Reactor’s early days of operation weren’t as smooth as operators would have liked.
D Reactor had only been operational for a few years when scientists detected a problem with the reactor operations. They were so concerned that D Reactor would fail that they built another reactor, called the DR Reactor, right next door. By October 1950, DR (which stands for D-Replacement) Reactor went online as the fifth plutonium production reactor at Hanford.
At about the same time, the problems associated with the D Reactor were solved, and both D and DR Reactors ran side-by-side into the mid-1960s when they were shut down. Since then, both reactors have been cocooned (DR in 2002, D in 2004). D Reactor was one of the Site’s longest-serving facilities with 22 years of service, while DR Reactor was online for the shortest amount of time, only 14 years.