Thin Man (nuclear bomb) Thin Man (nuclear bomb) "Thin Man" was the code name for a proposed plutonium gun-type nuclear bomb using plutonium-239 which the United States was developing during the Manhattan Project. They aborted its development when they discovered that the spontaneous fission rate of their nuclear reactor-bred plutonium was too high for use in a gun-type design, due to the high concentration of the isotope plutonium-240. In 1942, prior to the Army taking over wartime atomic research, Robert Oppenheimer held conferences in Chicago in June and Berkeley, California, in July at which various engineers and physicists discussed nuclear bomb design issues. A
Soviet atomic bomb project (including those now in Kazakhstan). The uranium for the Soviet nuclear weapons program came from mine production in the following countries, RDS-1, the first Soviet atomic test was internally code-named "First Lightning" ("Первая молния", or Pervaya Molniya) August 29, 1949, and was code-named by the Americans as "Joe 1". The design was very similar to the first US "Fat Man" plutonium bomb, using a TNT/hexogen implosion lens design. On September 24, 1951, the 38.3 kiloton device RDS-2 was tested based on a tritium "boosted" uranium implosion device with a levitated core. This test was code named "Joe 2" by the