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For other uses, see K25 (disambiguation).
The K-25 building of the Oak Ridge Gaseous Diffusion Plant aerial view, looking southeast. The mile-long [half-mile? - see 'History', para 2] building, in the shape of a "U" was completely demolished by the end of 2013.

K-25 is a former uranium enrichment facility of the Manhattan Project which used the gaseous diffusion method. The plant was located in Oak Ridge, Tennessee, on the southwestern end of the Oak Ridge Reservation. "K-25" was the name of the first and largest building and also the name of the larger complex, after other "K-" buildings were added.


The code name "K-25" was a combination of the "K" from the Kellex Corporation, the initial contractors of the plant, and "25," a World War II-era code designation for uranium-235 (element 92, atomic mass 235).[1][2]

Work on the facility began in June 1943 and was completed in early 1945 employing 12,000 workers and costing $512 million (equivalent to $6.7 billion in today dollars[3]). The U-shaped K-25 building measured half a mile by 1,000 feet (300 m) – over 2,000,000 square feet (190,000 m2). 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 nearby, 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.[4]

In the post-war years, additional uranium enrichment facilities were built adjacent to K-25 forming a complex officially known as the Oak Ridge Gaseous Diffusion Plant and commonly called the "K-25 site". Uranium enrichment operations at the K-25 site ceased in 1987.[5] This entire site is now called the East Tennessee Technology Park.


The gaseous diffusion method enriches uranium by separating uranium-235 from uranium-238. Based on the principle that molecules of a lighter isotope would pass through a porous barrier more readily than molecules of a heavier one, gaseous diffusion of uranium hexafluoride produced a gas increasingly rich in uranium-235 as the heavier uranium-238 was separated out in a system of cascades. As it produced minute amounts of final product compared to the total amount of uranium in the plant, gaseous diffusion required a massive facility to house the thousands of cascades and consumed enormous amounts of electric power. Uranium hexafluoride is highly corrosive, and the recently developed plastic teflon was used to coat the valves and seals that came in contact with the gas.

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 8 miles (13 km) 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 gaseous diffusion facilities and those at Paducah, Kentucky and Portsmouth, Ohio.[5] Today, uranium isotope separation is preferably done by the much more energy-efficient ultra centrifuge process.

Closure and demolition[edit]

Demolition of K-25 in progress in April 2012

The United States Department of Energy initially contracted with Bechtel Jacobs to dismantle and demolish the K-25 facility.[6] The contract with Bechtel Jacobs ended in August 2011. Since then demolition work has been performed by DOE's current Environmental Management contractor, URS | CH2M Hill Oak Ridge (UCOR).[7] Complete demolition of the K-25 facility is expected to be completed by July 2014.[8] As of January 23, 2013, demolition of the north and west wings was complete, with only a small portion of the east wing remaining (6 units out of 24 on the east wing).[9] The final section of the east wing was brought down on December 19, 2013. Debris from the site will be removed into 2014.[10]

See also[edit]

Notes and references[edit]

  1. ^ "Response to letter from Mr. Gus Robinson to General Nichols, providing information relating to Site designations and Site codes for Manhattan District facilities., 10/17/1949", digitized and online as ARC Identifier 281585 at National Archives Archival Research Catalog.
  2. ^ R.P. Prince and A. Milton Stanley (2000). "What Does K-25 Stand For? Deciphering the Origins of the Manhattan Project Code Names in Oak Ridge". The Journal of East Tennessee History (72): 83. 
  3. ^ Consumer Price Index (estimate) 1800–. Federal Reserve Bank of Minneapolis. Retrieved November 10, 2015.
  4. ^ "Manhattan Project Signature Facilities". atomicarchive.com. Retrieved 2 March 2008. 
  5. ^ a b "K-25 tour attracts international visitors". oakridger.com. Retrieved 2 March 2008. [dead link]
  6. ^ "DOE and Bechtel Jacobs sign $1.48B cleanup contract". Retrieved 2009-02-14. 
  7. ^ East Tennessee Technology Park Fact Sheet. DOE Oak Ridge Environmental Management Program. Retrieved August 29, 2013
  8. ^ "Oak Ridge Finds Ways to Remove K-25 Faster, Cheaper". www.energy.gov. February 1, 2012. Retrieved August 29, 2013.
  9. ^ "Oak Ridge EM Program Completes K-25 North End Demolition". www.energy.gov. January 23, 2013. Retrieved August 29, 2013.
  10. ^ Oak Ridge Today [1] Retrieved January 19, 2014.

External links[edit]

Coordinates: 35°55′56″N 84°23′42″W / 35.93222°N 84.39500°W / 35.93222; -84.39500