The Amount of Plutonium in the Nagasaki Bomb. This glass ball is the exact size of the plutonium core in the bomb that destroyed Nagasaki. Plutonium is a man-made nuclear explosive; it is created inside all nuclear reactors when uranium is bombarded with neutrons. Some uranium atoms can absorb a neutron without fissioning; when that happens, they are transmuted into plutonium atoms. Plutonium has become the nuclear explosive of choice in the world’s nuclear arsenals. Nuclear power advocates also see plutonium as the fuel of the future, as a resurgence of nuclear power will make plutonium fuel a necessity when uranium supplies dwindle. Photo and text by Robert Del Tredici, Kansas City, Missouri. 22 September 1983.