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The Manhattan Project Heritage Preservation Association, Inc. "Preserving, Exhibiting, Interpreting and Teaching the History of the Manhattan Project" |
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Manhattan Project History
Clinton Engineer Works (Oak Ridge)
Y-12 Plant (Page 1 of 3)
Electromagnetic Separation of Uranium 235
Operator: Tennessee Eastman Company (Kodak)
February 18, 1943
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Although the Lewis Committee report had placed gaseous diffusion ahead of the electromagnetic approach, many were still betting in early 1943 that Lawrence and his mass spectrograph would eventually predominate. Lawrence and his laboratory of mechanics at Berkeley continued to experiment with the giant 184-inch magnet, trying to reach a consensus on which shims, sources, and collectors to incorporate into the Y-12 design for the Oak Ridge plant. Research on magnet size and placement and beam resolution eventually led to a "racetrack" configuration of two magnets with forty-eight gaps containing two vacuum tanks each per building, with ten buildings being necessary to provide the 2,000 sources and collectors needed to separate 100 grams of uranium 235 daily. It was hoped that improvements in calutron design, or placing multiple sources and collectors in each tank, might increase efficiency and reduce the number of tanks and buildings required, but experimental results were inconclusive even as Stone & Webster of Boston, the Y-12 contractor, prepared to break ground. At a meeting of Groves, Lawrence, and John Lotz of Stone & Webster in Berkeley late in December 1942, Y-12 plans took shape. It was agreed that Stone & Webster would take over design and construction of a 500-tank facility, while Lawrence's laboratory would play a supporting role by supplying experimental data. By the time another summit conference on Y-12 took place in Berkeley on January 13 and 14, Groves had persuaded the Tennessee Eastman Company to sign on as plant operator and arranged for various parts of the electromagnetic equipment to be manufactured by the Westinghouse Electric Company, the Allis-Chalmers Manufacturing Company and the Chapman Valve Manufacturing Company. At the same time, General Electric agreed to provide electrical equipment. On January 14, after a day of presentations and a demonstration of the experimental tanks in the cyclotron building, Groves stunned the Y-12 contractors by insisting that the first racetrack of ninety-six tanks be in operation by July 1 and that 500 tanks be delivered by year's end. Given that each racetrack assembly was 122 feet long, 77 feet wide and 15 feet high; that the completed plant was to be the size of three, large two-story buildings; that tank design was still in flux; and that chemical extraction facilities also would have to be built, Groves' demands were little less than shocking. Nonetheless, Groves maintained that his schedule could be met. For the next two months Lawrence, the contractors, and the Army negotiated over the final design. While all involved could see possible improvements, there simply was not enough time to incorporate every suggested modification. Y-12 design was finalized at a March 17 meeting in Boston, with one major modification - the inclusion of a second stage of the electromagnetic process. The purpose of this second stage was to take the enriched uranium 235 derived from several runs of the first stage and use it as the "feed material" for a second stage of racetracks containing tanks approximately half the size of those in the first. Groves approved this arrangement and work began on both the Alpha (first-stage) and Beta (second-stage) tracks. Groundbreaking for the Alpha plant took place on February 18, 1943. Soon blueprints could not be produced fast enough to keep up with construction as Stone & Webster labored to meet Groves' deadline. The Beta facility was actually begun before formal authorization. While laborers were aggressively recruited, there was always a shortage of workers skilled enough to perform jobs according to the rigid specifications. (A further complication was that some tasks could be performed only by workers with special security clearances). Huge amounts of material had to be obtained (38 million board feet of lumber, for instance), and the magnets needed so much copper for windings that the Army had to borrow close to 15,000 tons of silver bullion from the United States Treasury to fabricate into strips and wind onto coils as a substitute for copper. Treasury silver was also used to manufacture the busbars that ran around the top of the racetracks. Replacing copper with silver solved the immediate problem of the magnets and busbars, but persistent shortages of electronic tubes, generators, regulators, and other equipment plagued the electromagnetic project and posed the most serious threat to Groves' deadline. Furthermore, last minute design changes continued to frustrate equipment manufacturers. Nonetheless, when Lawrence toured with Y-12 contractors in May of 1943, he was impressed by the scale of operations. Lawrence returned to Berkeley rededicated to the "awful job" of finishing the racetracks on time.
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