Producing plutonium in useful quantities for the first time was a major part of the Manhattan Project during World War II that developed the first atomic bombs . The Fat Man bombs used in the Trinity nuclear test in July 1945 , and in the bombing of Nagasaki in August 1945 , had plutonium cores . Human radiation experiments studying plutonium were conducted without informed consent , and several criticality accidents , some lethal , occurred after the war . Disposal of plutonium waste from nuclear power plants and dismantled nuclear weapons built during the Cold War is a nuclear-proliferation and environmental concern . Other sources of plutonium in the environment are fallout from numerous above-ground nuclear tests , now banned
Trinity
Trinity (nuclear test)
Plutonium