S-50

S-50. It was a thermal diffusion plant constructed during World War II as part of the top-secret Manhattan Project. The facility was built at the Clinton Engineer Works in Oak Ridge to enrich uranium for the first atomic bomb. Its rapid deployment and operation provided crucial material that fed into other, larger enrichment processes, contributing directly to the Trinity test and the atomic bombings of Hiroshima and Nagasaki.

History

The concept for using thermal diffusion for isotope separation was pioneered by Philip Abelson at the Naval Research Laboratory. In early 1944, with the Y-12 electromagnetic plant struggling, Leslie Groves and J. Robert Oppenheimer sought additional methods to boost production of uranium-235. After a review by a committee including Richard C. Tolman and William D. Coolidge, George B. Kistiakowsky recommended immediate construction of a thermal diffusion plant. Authorization was given in June 1944, and the H. K. Ferguson Company was contracted to build the facility with extreme urgency on a site adjacent to the K-25 gaseous diffusion plant. The project faced intense pressure due to the ongoing Allied invasion of Normandy and fears that Nazi Germany was ahead in the German nuclear weapon project.

Design and operation

The plant's design was based directly on Abelson's experimental columns at the Philadelphia Navy Yard. The process exploited the Soret effect, where a temperature gradient in a liquid mixture causes isotopes to separate. The system consisted of 2,142 identical columns, each a triple-tube apparatus with a hot nickel inner tube and a cold copper outer tube, with uranium hexafluoride gas in the annulus. Steam from the nearby K-25 powerhouse, provided by the Tennessee Valley Authority, heated the inner tubes to approximately 285°C, while cooling water at around 65°C circulated around the outer tubes. This created the necessary thermal gradient, causing the lighter uranium-235 to concentrate near the hot surface and be drawn off as slightly enriched product.

Production and deployment

Construction began in July 1944 and was completed in an astonishing 90 days, with the first columns operating by September. Full operation was achieved by January 1945. The plant was not highly efficient on its own, enriching feed material from a natural abundance of 0.71% uranium-235 to only about 0.86%. However, its output, approximately 12 kilograms per month of this slightly enriched product, was fed as improved feed material into the Y-12 calutrons. This synergistic integration significantly increased the overall output and efficiency of the Oak Ridge enrichment cascade. The workforce, managed by H. K. Ferguson Company and supervised by the United States Army Corps of Engineers, operated the plant around the clock.

Role in the Manhattan Project

S-50 played a critical, if interim, role in the final push for uranium-235. Its product boosted the feed for the Alpha tracks at the Y-12 facility, effectively increasing their output by as much as 30%. This additional material was vital for meeting the production schedule for the Little Boy gun-type weapon. The enriched uranium from the combined Oak Ridge operations was used in the Trinity test device and ultimately in the bomb dropped on Hiroshima. The success of S-50 demonstrated the Manhattan Project's ability to rapidly deploy and integrate multiple, parallel technological solutions under immense pressure.

Post-war decommissioning

Operations at the plant ceased immediately following the surrender of Japan in September 1945. With the war over and more efficient gaseous diffusion technology proven at the K-25 plant, S-50 was deemed obsolete. The facility was permanently shut down, and decommissioning activities began shortly thereafter. The columns were drained and the plant was dismantled. The building was later repurposed for other research activities at what became the Oak Ridge National Laboratory. The site where S-50 stood is now part of the extensive East Tennessee Technology Park, with little remaining of the original thermal diffusion structures. Category:Manhattan Project Category:Nuclear history of the United States Category:Oak Ridge, Tennessee Category:Buildings and structures in Tennessee Category:1944 establishments in Tennessee