Clinton Engineer Works

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Workers leaving the Manhattan Project's Y-12 plant at shift changing time, 1945

The Clinton Engineer Works (CEW) was the name of the Manhattan Project's production installation during World War II that produced the enriched uranium used in the bombing of Hiroshima in August 1945. It consisted of production facilities, utilities, and the town of Oak Ridge. It was in the eastern part of the 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 production facilities are mainly in Roane County although the northern part of the site in Anderson County. The Manhattan District Engineer. Kenneth Nichols, moved the Manhattan District headquarters from Manhattan to Oak Ridge in August 1943.

Construction workers 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. 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 peaked at 75,000 and the combined employment peak was 80,000. 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.

Site selection[edit]

Projected Site for Atomic Production Plants, 1942

On 25 June 1942, the Office of Scientific Research and Development (OSRD) S-1 Executive Committee deliberated on where the production facilities of the Manhattan Project should be located. Brigadier General Wilhelm D. Styer recommended that all the different manufacturing facilities be built at the same site in order to simplify security and construction. Such a site would require a substantial tract of land to accommodate both the facilities and housing for the thousands of workers. The plutonium processing plant needed to be 2 to 4 miles (3.2 to 6.4 km) from the site boundary and any other installation in case radioactive fission products escaped. While security and safety concerns suggested a remote site, it still needed to be near sources of labor, and accessible by road and rail transportation. A mild climate that allow construction to proceed throughout the year was desirable. Terrain separated by ridges would reduce the impact of accidental explosions, but they could not be so steep as to complicate construction. The substratum needed to be firm enough to provide good foundations, but not so rocky that it would hinder excavation work. It was estimated that the proposed plants would need access to 150,000 KW of electricity and 370,000 US gallons (1,400,000 l; 310,000 imp gal) of water per minute.[1][2][3] A War Department policy was that as a rule munitions facilities should not be located west of the Sierra or Cascade Ranges, east of the Appalachian Mountains, or within 200 miles (320 km) of the Canadian or Mexican borders.[4]

Several sites were considered in the Tennessee Valley, two in the Chicago area, one near the Shasta Dam in California, and some in Washington state, where some facilities were eventually established.[3] An OSRD team had selected the Knoxville, Tennessee, area in April 1942,[1] and in May Arthur Compton, the director of the Metallurgical Laboratory had met with Gordon R. Clapp, the General Manager of the Tennessee Valley Authority (TVA).[5] The Chief Engineer of the Manhattan District (MED), Colonel James C. Marshall, asked Colonel Leslie R. Groves, Jr. to undertake a study within the Army's Office of the Chief of Engineers. After receiving assurances that the TVA could supply the required quantity of electric power if given priority for procuring some needed equipment, Groves also concluded that the Knoxville area was suitable.[6] The only voice of dissent at 25 June meeting was Ernest O. Lawrence, who wanted the electromagnetic separation plant located much nearer to his Radiation Laboratory in California.[1] The Shasta Dam area remained under consideration for the electromagnetic plant until September, by which time Lawrence had dropped his objection.[7]

On 1 July, Marshall and his deputy, Lieutenant Colonel Kenneth Nichols, surveyed sites in the Knoxville area with representatives of the TVA and Stone & Webster, the designated construction contractor. No perfectly suitable site was found, and Marshall even ordered another survey of the Spokane, Washington, area.[2] At the time, the proposed nuclear reactor, gas centrifuge and gaseous diffusion technologies were still in the research stage, and the design of the plant was a long way off. The schedules, which called for construction work on the nuclear reactor to commence by 1 October 1942, the electromagnetic plant by 1 November, the centrifugal plant by 1 January 1943 and the gaseous diffusion plant by 1 March 1943, were quite unrealistic.[8] While work could not commence on the plants, a start could be made on the housing and administrative buildings. Stone & Webster therefore drew up a detailed report on the most promising site, about 12 miles (19 km) west of Knoxville.[2]

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.[9]

The site was located in Roane County and Anderson County, and lay roughly halfway between the two county seats of Kingston and Clinton.[10] Its major drawback was that a major road, Tennessee State Route 61 ran through it. Stone & Webster considered the possibility of re-routing the road.[7] The Ohio River Division (ORD) of the Corps of Engineers estimated that it would cost $4.25 million (equivalent to $61.34 million in 2015) to purchase the entire 83,000 acres (34,000 ha) site.[7]

Groves became the director of the Manhattan Project on 23 September, with the rank of brigadier general.[11] That afternoon, he took a train to Knoxville, where he met with Marshall.[12] After touring the site, Groves concluded that the site "was an even better choice than I had anticipated."[13] He called Colonel John J. O'Brien of the Corps of Engineers' Real Estate Branch, and told him to proceed with acquiring the land.[10] The site was initially known as the Kingston Demolition Range. It officially became the Clinton Engineer Works (CEW) in January 1943.[14] It was given the codename of Site X.[15] After the township was established in mid-1943, the name Oak Ridge was chosen for it from employee suggestions. It met with the Manhattan District's approval because "its rural connotation held outside curiosity to a minimum."[16] Oak Ridge then became the site's postal address; but the site itself was not officially renamed Oak Ridge until 1947.[17]

Land acquisition[edit]

War Department policy was that land should be acquired by direct purchase; but as time was short, it was decided to proceed immediately with condemnation.[18] This allowed access to the site for construction crews, provided faster compensation for the owners, and expedited the handling of property with defective titles. On 28 September 1942, the ORD Real Estate Branch opened a project office in Harriman with a staff of 54 surveyors, appraisers, lawyers and office workers. The ORD Real Estate Branch was quite busy at this time, as it was also acquiring land for the Dale Hollow Reservoir, so some staff were borrowed from the Federal Land Bank and the TVA.[19] The next day, Under Secretary of War Robert P. Patterson authorized the acquisition of 56,000 acres (23,000 ha) at an estimated cost of $3.5 million (equivalent to $50.52 million in 2015).[10] At the request of the ORD Real Estate Branch attorneys, the District Court for the Eastern District of Tennessee issued an order of possession on 6 October, effective the next day.[19] Recognizing the hardship that it would cause to the landowners, it restricted immediate exclusive possession to properties "essential to full and complete development of the project".[20]

A. L. Robinette, one of the farmers dispossessed by the compulsory acquisition of his land[21]

Over 1,000 families lived on the site on farms or in the hamlets of Elza, Robertsville and Scarboro.[10][22] The first that most heard about the acquisition was when a representative from the ORD showed up to inform them that their land was being acquired. Some returned home from work one day to find an eviction notice nailed to their door or to a tree in the yard. Most were given six weeks to leave, but some were given just two.[23] The government took possession of 13 tracts for immediate construction work on 20 November 1942. By May 1943, 742 declarations had been filed covering 53,334 acres (21,584 ha). Most residents were told to prepare to leave between 1 December 1942 and 15 January 1943. In cases where this would cause undue hardship, the MED allowed residents to stay beyond this date.[20] For some it was the third time that they had been evicted by the government, having previously been evicted for the Great Smoky Mountains National Park in the 1920s and the TVA's Norris Dam in the 1930s. Many expected that, like the TVA, the Army would provide assistance to help them relocate; but unlike the TVA, the Army had no mission to improve the area or the lot of the local people, and no funds for the purpose.[24][25] Tires were in short supply in wartime America,[24] and moving vehicles were hard to find.[25] Some residents had to leave behind possessions that they were unable to take with them.[23]

A delegation of landowners presented the ORD Real Estate Branch with a petition to protesting the acquisition of their property on 23 November 1942, and that night over 200 landowners held a meeting where they agreed to hire lawyers and appraisers to challenge the Federal government. Local newspapers and politicians were sympathetic to their cause. By the end of May 1943, agreements were reached covering 416 tracts totalling 21,742 acres (8,799 ha), but some landowners rejected the government's offers. The ORD Real Estate Branch invoked a procedure under Tennessee law that allowed for a jury of five citizens appointed by the Federal District Court to review the compensation offered. They handled five cases in which they proposed higher values than those of the ORD appraisers, but the landowners rejected them as well, so the Army discontinued the use of this method. In response to rising public criticism, O'Brien commissioned a review by the Department of Agriculture. It found that the appraisals had been fair and just, while farmers overestimated the size and productivity of their land.[26]

The landowners turned to their local Congressman, John Jennings, Jr. On 1 February 1943, Jennings introduced a resolution in the House of Representatives calling for a committee to investigate the values offered to the landowners. He also complained to Patterson about how buildings and facilities were being demolished by the MED. On 9 July 1943, Andrew J. May, the chairman of the House Committee on Military Affairs, appointed an investigating subcommittee chaired by Clifford Davis, who selected Dewey Short and John Sparkman as its other members. Public hearings were held in Clinton on 11 August 1943, and in Kingston the following day. Its report, presented in December 1943, made a number of specific recommendations concerning the Corps of Engineers' land acquisition process, but neither Congress nor the War Department moved to provide any additional compensation for the landowners.[27]

A notice to landowners that their land is now in the possession of the federal government and they must vacate the premises

In July 1943, Groves prepared to issue Public Proclamation No. 2, declaring the site a military exclusion area. He asked Marshall to present it to the Governor of Tennessee, Prentice Cooper. Marshall, in turn, delegated the task to the area engineer, Major Thomas T. Crenshaw, who sent a junior officer, Captain George B. Leonard.[28][29][30] Cooper was unimpressed. He told Leonard that had not been informed about the purpose of the CEW, that the Army had kicked the farmers off their land, and had not compensated the counties for the roads and bridges, which would now be closed. In his opinion it was a "an experiment in socialism",[29] a New Deal project being undertaken in the name of the war effort. Instead of reading the proclamation, he tore it up and threw it in the waste paper basket.[29] Marshall went to Nashville to apologize to Cooper, who refused to talk to him. Nichols, who succeeded Marshall as chief engineer of the Manhattan District, met Cooper on 31 July 1943,[31] and offered compensation in the form of Federal financing for road improvements.[30] Cooper accepted an offer from Nichols to visit the CEW, which he did on 3 November 1943.[32]

Nichols and Cooper came to an agreement about the Solway Bridge. Although it was in Knox County, Anderson County had contributed $27,000 (equivalent to $390,000 in 2015) towards its construction. It was still paying off the bonds, but now the bridge was usable only by CEW workers. Nichols negotiated a deal by which Knox County was paid $25,000 annually (equivalent to $361,000 in 2015) for the bridge, of which $6,000 (equivalent to $87,000 in 2015) was to be used to maintain the access road. Judge Thomas L. Seeber then threatened to close the Edgemoor Bridge unless Anderson County was similarly compensated. An agreement was reached under which Anderson County received $10,000 (equivalent to $144,000 in 2015) for the bridge and $200 per month (equivalent to $3,000 in 2015). Knox County did not keep its side of the bargain. Heavy traffic tore up the road, and it failed after torrential rains in 1944. The Army was forced to spend $5,000 (equivalent to $72,000 in 2015) per month on road works in Knox County.[32][33]

Additional parcels of land were acquired during 1943 and 1944 for access roads, a railway spur and security purposes. This brought the total amount acquired to about 58,900 acres (23,800 ha).[19] The Harriman office closed on 10 June 1944, but reopened on 1 September 1944 to deal with the additional parcels. The last of the acquisitions was not complete until 1 March 1945.[34] The final cost of the land acquired was around $2.6 million (equivalent to $37.53 million in 2015), about $47 an acre.[35]


Contour map of the Oak Ridge area. There is a river to the south, while the township is in the north.
Oak Ridge. The Y-12 electromagnetic separation plant is in the upper right. The K-25 and K-27 gaseous diffusion plants are in the lower left, near the S-50 thermal diffusion plant. The X-10 is in the lower center.

X-10 graphite reactor[edit]

Main article: X-10 Graphite Reactor
Five girls scouts in uniform. Two adult women in scout uniform watch over them. Behind them is a barbed wire fence, and in the background is an industrial building with a tall smoke stack.
Girl scouts visit X-10. When the girl scout troop was formed in wartime Oak Ridge, girls were listed as coming from the Knoxville Girl Scout office, and were registered by their first names only to safeguard their fathers' identities.[36]

On February 2, 1943, DuPont began construction of the plutonium semiworks,[37] on an isolated 112-acre (0.5 km2) site in the Bethel Valley about 10 miles (16 km) southwest of Oak Ridge. Intended as a pilot plant for the larger production facilities at the Hanford Site, it included the air-cooled graphite-moderated X-10 Graphite Reactor There was also a chemical separation plant, a research laboratories, waste storage area, training facility for Hanford staff, and administrative and support facilities that included a laundry, cafeteria, first aid center and fire station. Because of the subsequent decision to construct water-cooled reactors at Hanford, only the chemical separation plant operated as a true pilot.[38][39] The facility was known as the Clinton Laboratories, and was operated by University of Chicago as part of the Metallurgical Laboratory project.[40]

The X-10 Graphite Reactor was the world's second artificial nuclear reactor after Enrico Fermi's Chicago Pile-1, and was the first reactor designed and built for continuous operation.[41] It consisted of a huge block 24 feet (7.3 m) long on each side, of nuclear graphite cubes, weighing around 1,500 long tons (1,500 t), surrounded by 7 feet (2.1 m) of high-density concrete as a radiation shield.[38] There were 36 horizontal rows of 35 holes. Behind each was a metal channel into which uranium fuel slugs could be inserted.[42] The cooling system was driven by three large electric fans.[43]

Construction work on the reactor had to wait until DuPont had completed the design. Excavation commenced on April 27, 1943. A large pocket of soft clay was soon discovered, requiring additional foundations.[44] Further delays occurred due to wartime difficulties in procuring building materials. There was also an acute shortage of common and skilled labor, and the contractor had only three-quarters of the required workforce. This was aggravated by high turnover and absenteeism, mainly the result of poor accommodation and consequent difficulties in commuting. The township of Oak Ridge was still under construction, and barracks were built to house workers. Special arrangements with individual workers increased their morale and reduced turnover. Finally, there was unusually heavy rainfall, with 9.3 inches (240 mm) falling in July 1943, more than twice the average of 4.3 inches (110 mm).[38][45]

The 700 tons of graphite blocks were purchased from National Carbon. The construction crews began stacking it in September 1943. Cast uranium billets came from Metal Hydrides, Mallinckrodt and other suppliers. These were extruded into cylindrical slugs, and canned by Alcoa, which started production on June 14, 1943. General Electric and the Metallurgical Laboratory developed a new welding technique. The new equipment was installed in the production line at Alcoa in October 1943.[46] Supervised by Compton, Whitaker and Fermi, the reactor went critical on 4 November 1943 with about 30 long tons (30 t) of uranium. A week later the load was increased to 36 long tons (37 t), raising its power generation to 500 kW, and by the end of the month the first 500 milligrams (0.018 oz) of plutonium was created.[47] Modifications over time raised the power to 4,000 kW in July 1944.[48]

Construction commenced on the pilot separation plant before a chemical process for separating plutonium from uranium had been selected. Not until May 1943 would DuPont managers decide to use the Bismuth-phosphate process.[49] The plant consisted of six cells, separated from each other and the control room by thick concrete walls. The equipment was operated from the control room by remote control.[40] Construction work was completed on 26 November 1943,[50] but the plant could not operate until the reactor started producing irradiated uranium slugs.[38] The first batch was received on 20 December 1943, allowing the first plutonium to be produced in early 1944.[51] By February, the reactor was irradiating a a ton of uranium every three days, and 500 mg of plutonium had been produced. Over the next five months, the efficiency of the separation process was improved, with the percentage of plutonium recovered increasing from 40 to 90 percent. X-10 operated as a plutonium production plant until January 1945, when it was turned over to research activities. By this time, 299 batches of irradiated slugs had been processed.[48]

In September 1942, Compton asked a physicist, Martin D. Whitaker, to form the nucleus of an operating staff for X-10.[48] Whitaker became director of the Clinton Laboratories.[44] The first permanent operating staff arrived at X-10 from the Metallurgical Laboratory in Chicago in April 1944, by which time DuPont began transferring its technicians to the site. They were augmented by one hundred technicians in uniform from the Army's Special Engineer Detachment. By March 1944, there were some 1,500 people working at X-10.[48]

Additions including a radioisotope building, a steam plant, and related structures commenced in April 1946 in order to support the laboratory's peacetime educational and research missions. All work was completed by December 1946. The additions added another $1,009,000 to the cost of construction at X-10, and brought the total cost to $13,041,000.[40] Operational costs added another $22,250,000.[42]

Y-12 electromagnetic separation plant[edit]

Electromagnetic isotope separation was developed by Lawrence at the University of California Radiation Laboratory. This method employed devices known as calutrons, a hybrid of the standard laboratory mass spectrometer and cyclotron. The name was derived from the words "California", "university" and "cyclotron".[52] In the electromagnetic separation process, a magnetic field deflected charged uranium particles according to mass.[53] The process was neither scientifically elegant nor industrially efficient.[54] Compared with a gaseous diffusion plant or a nuclear reactor, an electromagnetic separation plant would consume more scarce materials, require more manpower to operate, and cost more to build. Nonetheless, the process was approved because it was based on proven technology and therefore represented less risk. Moreover, it could be built in stages, and rapidly reach industrial capacity.[52]

A long corridor with many consoles with dials and switches, attended by women seated on high stools.
Operators at their calutron control panels at Y-12. Gladys Owens, the woman seated in the foreground, did not know what she had been involved with until seeing this photo in a public tour of the facility fifty years later.[55]

Responsibility for the design and construction of the electromagnetic separation plant, which came to be called Y-12, was assigned to Stone & Webster by the S-1 Committee in June 1942. The design called for five first-stage processing units, known as Alpha racetracks, and two units for final processing, known as Beta racetracks. In September 1943 Groves authorized construction of four more racetracks, known as Alpha II. Construction began in February 1943.[56]

When the plant was started up for testing on schedule in October, the 14-ton vacuum tanks crept out of alignment because of the power of the magnets, and had to be fastened more securely. A more serious problem arose when the magnetic coils started shorting out. In December Groves ordered a magnet to be broken open, and handfuls of rust were found inside. Groves then ordered the racetracks to be torn down and the magnets sent back to the factory to be cleaned. A pickling plant was established on-site to clean the pipes and fittings.[54] The second Alpha I was not operational until the end of January 1944, the first Beta and first and third Alpha I's came online in March, and the fourth Alpha I was operational in April. The four Alpha II racetracks were completed between July and October 1944.[57]

Tennessee Eastman was hired to manage Y-12 on the usual cost plus fixed fee basis, with a fee of $22,500 per month plus $7,500 per racetrack for the first seven racetracks and $4,000 per additional racetrack.[58] The calutrons were initially operated by scientists from Berkeley to remove bugs and achieve a reasonable operating rate. They were then turned over to trained Tennessee Eastman operators who had only a high school education. Nichols compared unit production data, and pointed out to Lawrence that the young "hillbilly" girl operators were outperforming his PhDs. They agreed to a production race and Lawrence lost, a morale boost for the Tennessee Eastman workers and supervisors. The girls were "trained like soldiers not to reason why", while "the scientists could not refrain from time-consuming investigation of the cause of even minor fluctuations of the dials."[59]

Y-12 initially enriched the uranium-235 content to between 13% and 15%, and shipped the first few hundred grams of this to Los Alamos in March 1944. Only 1 part in 5,825 of the uranium feed emerged as final product. Much of the rest was splattered over equipment in the process. Strenuous recovery efforts helped raise production to 10% of the uranium-235 feed by January 1945. In February the Alpha racetracks began receiving slightly enriched (1.4%) feed from the new S-50 thermal diffusion plant. The next month it received enhanced (5%) feed from the K-25 gaseous diffusion plant. By April K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.[60]

The Alpha tracks began to suspended operations on September 4, 1945, and ceased operation completely on September 22. The last two Beta tracks went into full operation in November and December 1945, processing feed from K-25 and the new K-27.[61] By May 1946, studies suggested that the gaseous plants could fully enrich the uranium by themselves without accidentally creating a critical mass.[62] After a trial showed this was the case, Groves ordered all but one Beta track at Y-12 to be shut down in December 1946.[63] Y-12 remained 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.[64]

K-25 gaseous diffusion plant[edit]

The most promising but also the most challenging method of isotope separation was gaseous diffusion. Graham's law states that the rate of effusion of a gas is inversely proportional to the square root of its molecular mass, so in a box containing a semi-permeable membrane and a mixture of two gases, the lighter molecules will pass out of the container more rapidly than the heavier molecules. The gas leaving the container is somewhat enriched in the lighter molecules, while the residual gas is somewhat depleted. The idea was that such boxes could be formed into a cascade of pumps and membranes, with each successive stage containing a slightly more enriched mixture. Research into the process was carried out at Columbia University by a group that included Harold Urey, Karl P. Cohen and John R. Dunning.[65]

One of original houses overlooks the construction of K-25

In November 1942 the Military Policy Committee approved the construction of a 600-stage gaseous diffusion plant.[66] On 14 December, M. W. Kellogg accepted an offer to construct the plant, which was codenamed K-25. A cost plus fixed fee contract was negotiated, eventually totaling $2.5 million. A separate corporate entity called Kellex was created for the project, headed by Percival C. Keith, one of Kellogg's vice presidents.[67] The process faced formidable technical difficulties. The highly corrosive gas uranium hexafluoride would have to be used, as no substitute could be found, and the motors and pumps would have to be vacuum tight and enclosed in inert gas. The biggest problem was the design of the barrier, which would have to be strong, porous and resistant to corrosion by uranium hexafluoride. The best choice for this seemed to be nickel. Edward Adler and Edward Norris created a mesh barrier from electroplated nickel. A six-stage pilot plant was built at Columbia to test the process, but the Norris-Adler prototype proved to be too brittle. A rival barrier was developed from powdered nickel by Kellex, the Bell Telephone Laboratories and the Bakelite Corporation. In January 1944, Groves ordered the Kellex barrier into production.[68][69]

Kellex's design for K-25 called for a four-story 0.5-mile (0.80 km) long U-shaped structure containing 54 contiguous buildings. These were divided into nine sections. Within these were cells of six stages. The cells could be operated independently, or consecutively within a section. Similarly, the sections could be operated separately or as part of a single cascade. A survey party began construction by marking out the 500-acre (2.0 km2) site in May 1943. Work on the main building began in October 1943, and the six-stage pilot plant was ready for operation on 17 April 1944. In 1945 Groves canceled the upper stages of the plant, directing Kellex to instead design and build a 540-stage side feed unit, which became known as K-27. Kellex transferred the last unit to the operating contractor, Union Carbide and Carbon, on 11 September 1945. The total cost, including the K-27 plant completed after the war, came to $480 million.[70]

The production plant commenced operation in February 1945, and as cascade after cascade came online, the quality of the product increased. By April 1945, K-25 had attained a 1.1% enrichment and the output of the S-50 thermal diffusion plant began being used as feed. Some product produced the next month reached nearly 7% enrichment. In August, the last of the 2,892 stages commenced operation. K-25 and K-27 achieved their full potential in the early postwar period, when they eclipsed the other production plants and became the prototypes for a new generation of plants.[71] Uranium was enriched by the K-25 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.[72]

S-50 liquid thermal diffusion plant[edit]

The thermal diffusion process was based on Sydney Chapman and David Enskog's theory, which explained that when a mixed gas passes through a temperature gradient, the heavier one tends to concentrate at the cold end and the lighter one at the warm end. Since hot gases tend to rise and cool ones tend to fall, this can be used as a means of isotope separation. This process was first demonstrated by H. Clusius and G. Dickel in Germany in 1938.[73] It was developed by US Navy scientists, but was not one of the enrichment technologies initially selected for use in the Manhattan Project. This was primarily due to doubts about its technical feasibility, but the inter-service rivalry between the Army and Navy also played a part.[74]

A factory with three smoking chimneys on a river bend, viewed from above
The S-50 plant is the dark building to the upper left behind the Oak Ridge powerhouse (with smoke stacks).

The Naval Research Laboratory continued the research under Philip Abelson's direction, but there was little contact with the Manhattan Project until April 1944, when Captain William S. Parsons, the naval officer who was in charge of ordnance development at Los Alamos, brought Robert Oppenheimer, the director there, news of encouraging progress in the Navy's experiments on thermal diffusion. Oppenheimer wrote to Groves suggesting that the output of a thermal diffusion plant could be fed into Y-12. Groves set up a committee consisting of Warren K. Lewis, Eger Murphree and Richard Tolman to investigate the idea, and they estimated that a thermal diffusion plant costing $3.5 million could enrich 50 kilograms (110 lb) of uranium per week to nearly 0.9% uranium-235. Groves approved its construction on 24 June 1944.[75]

Groves contracted with the H. K. Ferguson Company of Cleveland, Ohio, to build the thermal diffusion plant, which was designated S-50. Groves' advisers, Karl Cohen and W. I. Thompson from Standard Oil,[76] estimated that it would take six months to build. Groves gave Ferguson just four. Plans called for the installation of 2,142 48-foot-tall (15 m) diffusion columns arranged in 21 racks. Inside each column were three concentric tubes. Steam, obtained from the nearby K-25 powerhouse at a pressure of 100 pounds per square inch (690 kPa) and temperature of 545 °F (285 °C), flowed downward through the innermost 1.25-inch (32 mm) nickel pipe, while water at 155 °F (68 °C) flowed upward through the outermost iron pipe. Isotope separation occurred in the uranium hexafluoride gas between the nickel and copper pipes.[77]

Work commenced on 9 July 1944, and S-50 began partial operation in September. Ferguson operated the plant through a subsidiary known as Fercleve. The plant produced just 10.5 pounds (4.8 kg) of 0.852% uranium-235 in October. Leaks limited production and forced shutdowns over the next few months, but in June 1945 it produced 12,730 pounds (5,770 kg).[78] By March 1945, all 21 production racks were operating. Initially the output of S-50 was fed into Y-12, but starting in March 1945 all three enrichment processes were run in series. S-50 became the first stage, enriching from 0.71% to 0.89%. This material was fed into the gaseous diffusion process in the K-25 plant, which produced a product enriched to about 23%. This was, in turn, fed into Y-12.[79]

In early September Nichols appointed a production control committee, headed by Major A. V. (Pete) Peterson. 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 K-27 gaseous-diffusion plant and one more beta stage track for Y-12. These additions were estimated to cost $100 million, with completion in February 1946.[80] Soon after Japan surrendered in August 1945, Peterson recommended that S-50 be shut down. The Manhattan District ordered this on September 4, 1945. The last uranium hexafluoride was sent to K-25, and the plant had ceased operation by September 9, 1945.[81] S-50 was completely demolished in 1946.[82]


A hutment at Oak Ridge. Each of these 16-by-16-foot (4.9 by 4.9 m) temporary structures provided accommodation for five workers

Planning for a "Government village" to house the workers at the Clinton Engineering Works began in June 1942. Because the site was remote, it would be more convenient and secure for the workers to live on the site.[83] The gentle slopes of Black Oak Ridge, from which the new town of Oak Ridge got its name, were selected as a suitable location.[84] Brigadier General Lucius D. Clay, the deputy chief of staff of the United States Army Services of Supply for requirements reminded Marshall that there was a wartime limit of $7,500 per capita for individual quarters, but Groves, Nichols and Marshall saw no prospect of the kind of workers they needed being willing to live in substandard accommodation. The first plan, submitted by Stone and Webster on October 26, 1942, was for a residential community of 13,000 people.[85]

As Stone and Webster began work on the production facilities, it became clear that building the township as well would be beyond its capacity. The Army therefore engaged the architectural and engineering firm Skidmore, Owings & Merrill to design and build the township. The John B. Pierce Foundation were brought in as a consultant.[84][85] This first phase of construction became known the East Town. It included some 3,000 family dwellings, an administrative centre, three shopping centres, three grade schools for 500 children each and a high school for 500, recreation buildings, men's and women's dormitories, cafeterias, a medical services building and a 50-bed hospital. This work was completed in early 1944.[86][87]

The Army presence at Oak Ridge increased in August 1943 when Nichols replaced Marshall as head of the Manhattan Engineer District. One of his first tasks was to move the district headquarters to Oak Ridge although the name of the district did not change.[88] In September 1943 the administration of community facilities was outsourced to Turner Construction Company through a subsidiary, the Roane-Anderson Company.[89] Roane-Anderson did not take over everything at once. A phased takeover started with Laundry No. 1 on 17 October 1943. Transportation and garbage collection soon followed. It assumed responsibility for water and sewage in November, and electricity in January 1944. The number of Roane-Anderson workers peaked at around 10,500 in February 1945, including concessionaires and subcontractors. Thereafter, numbers declined to 2,905 direct employees and 3,663 concessionaires and subcontractors when the Manhattan Project ended on 31 December 1946.[90]

White and colored privies at the X-10 plant

This coincided with the second phase of construction, which began in the fall of 1943, and continued into the late summer of 1944. Plans now called for a town of 42,000 people.[86][87]

The population of Oak Ridge soon expanded well beyond the initial plans, and peaked at 75,000 in May 1945, by which time 82,000 people were employed at the Clinton Engineer Works,[91] and 10,000 by Roane-Anderson.[89]


Further information: Y-12 National Security Complex

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 Atomic Energy Commission 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.

Other wartime facilities[edit]


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Coordinates: 36°0′48″N 84°15′45″W / 36.01333°N 84.26250°W / 36.01333; -84.26250 (Oak Ridge)