Clinton Engineer Works

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Workers leaving the Manhattan Project's Y-12 plant at shift changing time, 1945 (US government photo by Ed Westcott)

The Clinton Engineer Works (CEW) was the Army name for the Manhattan Project production facility in World War II for enriched uranium (Uranium 235) used in the Little Boy atomic bomb dropped on Hiroshima in 1945, and would have produced enough enriched uranium for a second Little Boy gun-type bomb by December 1945.[1] The secret “semiworks” plant is on Oak Ridge in the eastern part of the U.S. state of Tennessee, about 18 miles (29 km) west of Knoxville, and was named after the town of Clinton, Tennessee, 8 miles (13 km) to the north. The plants are mainly in Roane County with the northern part of the site in Anderson County.

The construction workers for the K-25 and other plants were housed in a community known as Happy Valley. Built by the Army in 1943, the temporary Happy Valley community housed 15,000 people in trailer homes.[2]

The town of Oak Ridge was established to house the production staff. The operating force peaked at 50,000 workers just after the end of the war. The construction labour force peak was 75,000 and the combined employment peak was 80,000.[3] Developed by the federal government as a segregated community, black residents lived only in an area known as Gamble Valley, in government-built "hutments" (one-room shacks) on the south side of what is now Tuskegee Drive.

Ken Nichols the MED Deputy District Engineer from June 1942 and District Engineer from August 1943 was responsible for the Clinton and Hanford production “semiworks”, and their houses were of a higher quality than those approved by Groves at Los Alamos.[4] He moved the Manhattan District headquarters from Manhattan, New York to CEW in August 1943.[5] In 1954 Nichols transferred responsibility for coordinating supply of feed materials for both Oak Ridge and Hanford to Oak Ridge from New York, as with only two plants "the need for coordination had essentially been eliminated (but) as usual in government operations, no one wanted to take the onus of telling employees they no longer are needed."[6]


Map of Clinton Engineer Works sites

A survey team from the engineering company Stone & Webster had already scouted a site for the production plants, and recommended several sites in the Knoxville, Tennessee area, an isolated area where the Tennessee Valley Authority could supply ample electric power and the rivers could provide cooling water for the reactors. Site X or the Oak Ridge site, selected by James Marshall and Nichols in June 1942 had:[7]

... all the necessary requirements for the future atomic plants; an isolated area with plenty of electric power, abundant water supply, almost no population, good access by road and train, and a mild climate that permitted outdoor work the year round.
This portion of the quiet rural area was called Black Oak Ridge and was the northernmost of five principal oak- and pine-covered ridges around the meandering Clinch River. It was a verdant, beautiful countryside with rolling hills covered with dogwood and full of partridge and deer. To the east were the Great Smoky Mountains, to the west the peaks of the Cumberland Mountains.

Marshall had delayed purchase of the site until at least the chain reaction was proven, but on taking over Groves immediately (19 September) approved purchase of the 52,000 acres of land required. On 23 September the newly promoted Groves impressed Secretary of War Stimson and others at his first meeting with them by leaving early to catch the train to Tennessee to "inspect Site X."[8]

Postwar, on 19 March 1949, the residential and commercial portion of Oak Ridge, known as the "townsite," was opened to public access, and access to the AEC facilities was controlled by three gatehouses which replaced the seven wartime gates: Blair Gate to Harriman, Oliver Springs Gate, Elza Gate to Clinton, Edgemoor Gate to Clinton, Solway Gate to Knoxville, White Wing Gate to Lenoir City and Gallaher Gate to Kingston.


The K-25 powerhouse (foreground) and the S-50 plant were located adjacent to the Clinch River.

Three of the four major wartime facilities are still standing today:

  • K-25; where uranium was enriched by the gaseous diffusion process until 1985, was subsequently decommissioned and decontaminated. A coal-fired power station (235 MVA) was included for reliability and to provide variable frequency, although most electric power came from the TVA.[9]
  • Y-12; originally used for electromagnetic separation of uranium, was shut down in 1947, but is still in use for nuclear weapons processing and materials storage. A production facility for the hydrogen bomb exploded in Operation Castle in 1954 was hastily installed in 1952.[10]
  • X-10 is now the site of the Oak Ridge National Laboratory. The original building is now a National Historic Landmark. The test graphite reactor which produced the first significant amounts of plutonium was superseded by the Hanford Engineer Works.
  • The S-50 liquid thermal diffusion plant was demolished soon after the war.


The three uranium enrichment plants had different capabilities:

  • the K-25 gaseous diffusion plant could raise the enrichment from 0.7 to 36%.
  • the Y-12 electromagnetic separation plant had two different alpha stages, one more advanced. The alpha stages could raise it from 0.7% to 15 to 20%. The beta stage could raise it from 20 to 36% to an enrichment suitable for weapons.
  • the S-50 liquid thermal diffusion plant could raise the enrichment from 0.7 to 0.9%

Nichols realised in autumn 1944 that coordinating the use of the three plants would be much more difficult than anticipated. Initially it was planned to feed 1.1% material from K-25 into the Y-12 alpha stages, and as sufficient sections of K-25 were completed use them to produce 20% or higher enriched material to feed into the Y-12 beta stages. But a considerable equilibrium time was necessary to move from 1.1 to 20%.

In early September he appointed a production control committee, headed by A. V. (Pete) Peterson (a reserve officer, and his wife’s sister’s husband). Peterson’s staff tried various combinations, using mechanical calculating machines, and decided that the S-50 production should be fed to K-25 rather than Y-12, which was done in April 1945. The charts also showed that the proposed top stages for K-25 should be abandoned, as should Lawrence’s recommendation to add more alpha stages to the Y-12 plant. Groves accepted their proposal to add more base units to the gaseous-diffusion plant (K-27 not K-25) and one more beta stage track for Y-12. These additions were estimated to cost $100 million, with completion in February 1946.[11]

Because the enriched uranium was shipped out discreetly by courier in a suitcase, there was a local rumour that the secret CEW project must be a failure or a boondoggle. Many of the local residents and workers observed that thousands of railroad cars were carrying supplies into the CEW but no one had ever seen anything shipped out.[12]

Other wartime facilities[edit]

External links[edit]


  1. ^ Nichols p 175
  2. ^ "Manhattan Project Signature Facilities". Retrieved 2 March 2008. 
  3. ^ Nichols p. 157
  4. ^ Nichols p. 59
  5. ^ Nichols p. 115
  6. ^ Nichols pp. 332-333
  7. ^ Grouef p. 23
  8. ^ Rhodes pp. 427-428
  9. ^ Nichols pp. 93-94
  10. ^ Nichols p 333
  11. ^ Nichols pp. 159-161
  12. ^ Nichols p 162