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
Meson bomb however, the Soviet Union became convinced that the United States had already developed the meson bomb, and devoted considerable resources to developing its own. In 1994, Russian physicist and chief constructor of nuclear weapons bureau KB-11 (Design Bureau No. 11, set up in 1946) Arkadiy Brish stated that their work on the meson bomb was prompted by intelligence. Even though physicists Yuliy Borisovich Khariton and Yakov Borisovich Zel'dovich agreed that the reports were nonsensical, the directors of the Soviet atomic bomb project decided to pursue this line of research, which resulted in several years of fruitless labor. Brish attributed this