Oak Ridge Gaseous Diffusion Plant named a nuclear historic landmark

The American Nuclear Society recently announced the designation of three new nuclear historic landmarks: the Hot Fuel Examination Facility, the Neely Nuclear Research Center, and the Oak Ridge Gaseous Diffusion Plant K-25. Today's article, the final offering in a three-part series, will focus on the historical significance of the Oak Ridge Gaseous Diffusion Plant K-25.

Award details: ANS's Nuclear Historic Landmark Award memorializes sites and facilities where outstanding physical accomplishments that advanced the peaceful uses of nuclear energy have taken place. The award recognizes facilities that were in service at least 20 years ago.

The first nine landmarks (from Chicago Pile 1 to the Yankee nuclear power plant) were designated in 1985. As of 2025, including these newest recipients, ANS has recognized 101 sites as landmarks.

A brief history: Construction on K-25 began in summer 1943 as part of the Manhattan Project. By the time it entered operation in 1944, the building was three stories tall but a half a mile in length; it was the world's longest roofed building.

K-25 was used to separate lighter uranium-235 from heavier uranium-238 through more than 3,000 steps of gaseous diffusion, which involved the passage of uranium hexafluoride through pore-filled barriers at each step. While this process had been tested in smaller, laboratory settings, nothing like the scale of K-25 (which employed more than 10,000 workers) had ever been done.

Uranium separation was also performed at Oak Ridge's Y-12 and S-50 plants, which used electromagnetic separation and liquid thermal diffusion, respectively. K-25's gaseous diffusion method proved the cheapest and most efficient of the three. The uranium enriched at Oak Ridge was used for Little Boy, the first atomic bomb employed in warfare, which was dropped on Hiroshima, Japan, on August 6, 1945.

After the conclusion of World War II, K-25 continued producing enriched uranium for defense purposes through the first half of the Cold War and nuclear arms race, until President Lyndon B. Johnson gave an order to reduce the domestic production of enriched uranium in 1964. The plant entirely ceased production for non-defense purposes by 1987.

The land today: In 2013, Department of Energy contractors demolished the K-25 building as part of a broader effort starting in the early 2000s to cleanup the entirety of the former uranium enrichment complex. The land has been renamed the East Tennessee Technology Park. In all, the cleanup work has involved the removal of more than 500 deteriorating and contaminated buildings that could span the footprint of 225 football fields.

The DOE's Oak Ridge Office of Environmental Management has now transferred more than 1,800 acres of land from federal ownership for economic reuse at the ETTP. Today, the land contains more than 25 businesses, expected to generate 1,700 private sector jobs.