X-10

The unassuming building at Oak Ridge numbered X-10 housed the Graphite Reactor, the oldest nuclear reactor in the world. The Graphite Reactor was the world’s first powerful nuclear reactor which transformed uranium 238 into plutonium 239. The X-10 facilities also chemically separated the plutonium from the uranium. The Graphite Reactor was built in only eleven months, and it produced its first self-sustaining chain reaction on November 4, 1943. Less than two months later, it was yielding one-third ton of irradiated uranium a day, and in the early spring 1944 Oak Ridge scientists produced the world’s first grams of plutonium. The X-10 project served as the pilot plant for larger reactors and chemical facilities built at Hanford, Washington, in 1944. Its plutonium became the nuclear explosive used in the “Fat Man” bomb dropped on Nagasaki in 1945. X-10’s Graphite Reactor also produced the first electricity from nuclear energy and was the first reactor to be used for the study of the health hazards of radioactivity. Alvin Weinberg, former director of the Oak Ridge National Laboratory, observed: “the work that took place at the Graphite Reactor had ramifications for many fields of science,” such as modern mammalian radiation biology, nuclear power, and neutron diffraction. Also, “it was the first place where isotopes were produced for every science you can think of.” (1)

In the postwar years, the X-10 site, along with the Y-12 and K-25 complexes, evolved into Oak Ridge National Laboratory. The X-10 facility initially specialized in the design of nuclear reactors and later expanded into studies of other energy sources. The Y-12 plant became a center for precision machining, especially of nuclear weapon components. The K-25 Gaseous Diffusion Plant served as the model for additional similar plants built during the Cold War adjacent to the K-25 site and near Paducah, Kentucky, and Portsmouth, Ohio.

The Graphite Reactor at X-10 was shut down in 1963, after twenty years of use. It was listed as a National Historic Landmark in 1966, and is now open for public tours.