K-25

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Oak Ridge K-25 Plant

The K-25 plant, located on the southwestern end of the Oak Ridge reservation, used the gaseous diffusion method to enrich uranium by separating uranium-235 from uranium-238. Based on the well-known principle that molecules of a lighter isotope would pass through a porous barrier more readily than molecules of a heavier one, gaseous diffusion produced through myriads of repetitions a gas increasingly rich in uranium-235 as the heavier uranium-238 was separated out in a system of cascades. Although producing minute amounts of final product measured in grams, gaseous diffusion required a massive facility to house the thousands of cascades and consumed enormous amounts of electric power.

Begun in June 1943 and completed in early 1945 at a cost of $512 million, the K-25 plant employed 12,000 workers. The U-shaped K-25 building measures half a mile by 1,000 feet (over 2,000,000 sq. ft. (609,600 m²) and is larger than The Pentagon, and at the time was the biggest building in the world. Construction began before completion of the design for the process. Due to construction needs at K-25 and elsewhere on the reservation, the town of Oak Ridge, originally designed for 13,000 people, grew to 50,000 by summer 1944. The people needed for the construction of K-25 lived near by, in a community that came to be known as Happy Valley. Built by the Army in 1943, Happy Valley was a temporary community that housed 15,000 people in trailer homes. ^[1]

Gaseous diffusion was one of three isotope separation processes that provided uranium-235 for the Hiroshima weapon (Little Boy) - the other two being electromagnetic separation and liquid thermal diffusion. All of the plants were located on the Oak Ridge reservation. The Y-12 electromagnetic separation plant was located about eight miles northeast of the K-25 plant. The S-50 liquid thermal diffusion plant, using convection to separate the isotopes in thousands of tall columns, was built next to the K-25 power plant, which provided the necessary steam. Much less efficient than K-25, the S-50 plant was torn down after the war. Gaseous diffusion was the only uranium enrichment process used during the Cold War. K-25 was the prototype for later Oak Ridge plants and those at Paducah, Kentucky and Portsmouth, Ohio. Uranium enrichment operations at K-25 ceased in 1987.^[2]