THE NAVY AND 
THERMAL DIFFUSION
Oak Ridge: Clinton (1944)
Events: The Uranium Path to the
Bomb, 1942-1944

As problems with both Y-12 and K-25 reached crisis proportions in spring and summer 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 Leslie Groves, who, in fact, was not up-to-date on the state of Navy efforts when he received a letter on the subject from Robert Oppenheimer late in April 1944.

Oppenheimer informed Groves that the thermal diffusion experiments of Philip Abelson (right) at the Philadelphia Naval Yard deserved a closer look.  Abelson was building a plant to produce enriched uranium to be completed in 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 for Y-12 until problems with K-25 could be resolved.  

The liquid thermal diffusion process had been evaluated in 1940 by the Uranium Committee when Abelson was conducting experiments at the National Bureau of Standards.  In 1941, he moved to the Naval Research Laboratory, where there was more support for his work.  During summer 1942, Vannevar Bush and James 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 Naval Yard, where construction began in January 1944.  

Groves immediately saw the value of Oppenheimer's suggestion and sent a group to Philadelphia to visit Abelson’s plant.  A quick analysis demonstrated that a thermal diffusion plant could be built at Oak Ridge and placed in operation by early 1945.  The steam needed in the convection columns was already at hand in the form of the almost completed K-25 power plant.  It would be a relatively simple matter 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, H. K. Ferguson Company of Cleveland, just ninety days from September 27 to bring a 2,142-column plant on line (Abelson's plant contained 100 columns).  There was no time to waste as "Happy Valley" braced itself for a new influx of workers sent to build the S-50 Thermal Diffusion Plant (right).  Even with an operational S-50, however, it was still not possible to say for sure whether enough enriched uranium could be produced in time to create a bomb before the end of the war.  

To view the next "event" of the Manhattan Project, proceed to "1942-1944: The Plutonium Path to the Bomb."