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
History of the anti-nuclear movement where they were unable to sustain themselves. Radioactive fallout from nuclear weapons testing was first drawn to public attention in 1954 when a Hydrogen bomb test in the Pacific contaminated the crew of the Japanese fishing boat "Lucky Dragon". One of the fishermen died in Japan seven months later. The incident caused widespread concern around the world and "provided a decisive impetus for the emergence of the anti-nuclear weapons movement in many countries". The anti-nuclear weapons movement grew rapidly because for many people the atomic bomb "encapsulated the very worst direction in which society was moving". Peace movements emerged in