ABSTRACT
Physicists all over the world were excited by the announcement in January 1939, by the German chemists Otto Hahn and Fritz Strassman, that the nucleus of the uranium atom produced barium when bombarded with neutrons. The uranium fuel used in the Hiroshima bomb came from that operation. Within another year the gaseous diffusion process at K-25, a backup gamble, was proven to be a workable process and, being a continuous rather than batch operation, it was much less expensive. Enriched uranium is a critical component in civilian nuclear power generation, naval power generation, and military nuclear weapons. The term separative work unit is used to quantify the output of the enriching plants and to describe the supply and demand for enriching service. Although the enrichment of uranium by calutrons was discontinued in 1946, 72 of the 1152 calutrons remained in operation for the separation of isotopes for research in medicine, agriculture, industry, and biology.
