By the beginning of 1945 Soviet intelligence had a clear general picture of the Manhattan project. In February 1945 V. Merkulov, the People’s Commissar of State Security, wrote to Beria that research by leading British and American scientists had shown that an atomic bomb was feasible, and that there were two main problems to be solved in making it: production of the necessary quantity of fissionable material – uranium-235 or plutonium; and the design of the bomb. An isotope separation plant was being built in Tennessee, and plutonium was being produced at Hanford, in the state of Washington.
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