The Manhattan District engineer, Colonel Kenneth Nichols, placed Major John J. Moran in charge of production at K-25. Production commenced in February 1945, and the first product was shipped to the calutrons in March. By April, the gaseous diffusion plant was producing 1.1 percent product. It was then decided that instead of processing uranium hexafluoride feed from the Harshaw Chemical Company, the gaseous diffusion plant would take the product of the S-50 thermal diffusion plant, with an average enrichment of about 0.85 percent. Product enrichment continued to improve, as more stages came online and performed better than anticipated. In June product was being enriched to 7percent; by September it was 23 percent. The S-50 plant ceased operation on 9September, and Kellex transferred the last unit to Union Carbide on 11 September 1945. Highly enriched uranium was used in the Little Boy atomic bomb used in the bombing of Hiroshima on 6August 1945.