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Manhattan Project History

Clinton Engineer Works (Oak Ridge)

S-50 Plant

Liquid Thermal Diffusion Separation of Uranium 235

Operator:  Union Carbide Company

September 27, 1944



     As problems with both Y-12 and K-25 reached crisis proportions in the spring and summer of 1944, the Manhattan Project received help from an unexpected source - the United States Navy.  President Roosevelt had instructed that the atomic bomb effort be an Army program and that the Navy be excluded from deliberations.  Navy research on atomic power, conducted primarily for submarines, received no direct aid from Groves, who, in fact, was not up-to-date on the state of navy efforts when he received a letter on the subject from Oppenheimer in April 1944.

     Oppenheimer informed Groves that Philip Abelson's experiments on thermal diffusion at the Philadelphia Navy Yard deserved a closer look.  Abelson was building a plant to produce enriched uranium to be completed by early July 1944.  It might be possible, Oppenheimer thought, to help Abelson complete and expand his plant and use its slightly enriched product as feed material for Y-12 until the problems plaguing K-25 could be resolved.

     The liquid thermal diffusion process had been evaluated as early as 1940 by the Uranium Committee, when Abelson was still with the National Bureau of Standards.  In 1941 he moved his research to the Naval Research Laboratory, where there was more support for his work.  During the summer of 1942 Bush and Conant received reports about Abelson's research but concluded that it would take too long for the thermal diffusion process to make a major contribution to the bomb effort, especially since the electromagnetic and pile projects were making satisfactory progress.  After a visit with Abelson in January 1943, Bush encouraged the Navy to increase its support of thermal diffusion.  A thorough review of Abelson's project early in 1943, however, concluded that thermal diffusion work should be expanded but should not be considered as a replacement for gaseous diffusion, which was better understood theoretically.  Abelson continued his work independently of the Manhattan Project.  He obtained authorization to build a new plant at the Philadelphia Navy Yard, where construction began in January 1944. 

(Webmaster's Note:  The Navy, and specifically the Philadelphia Navy Yard, was chosen by Abelson because of their experience dealing with huge ship boilers which produced steam.  Steam was the essential source of heat required for the liquid thermal diffusion process.)

     Groves immediately saw the value of Oppenheimer's suggestion and sent a group to Philadelphia to visit Abelson's facility.  A quick analysis demonstrated that a thermal diffusion plant could indeed be built at Oak Ridge and placed in operation by early 1945.  The steam required in the convection columns was already at hand in the form of the almost completed K-25 powerplant (The largest in the world).  It would be relatively simple to provide steam to the thermal diffusion plant and produce enriched uranium, while providing electricity for the K-25 plant when it was finished.  Groves gave the contractor, the H. K. Ferguson Company of Cleveland, just ninety days from September 27 to bring a 2,142 column plant on line (In comparison, Abelson's plant in Philadelphia contained 100 columns).  There was no time to waste as Happy Valley in Oak Ridge braced itself for a new influx of 10,000 workers.




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