The Energy stored in the nucleus of an Atom and released through fission, fusion, or Radioactivity . In fission processes, a fissionable nucleus absorbs a Neutron , becomes unstable, and splits into two nearly equal nuclei. In fusion processes, two nuclei combine to form a single, heavier nucleus.
Fission occurs for very heavy nuclei, while fusion occurs for the lightest nuclei.
Nuclear fission was discovered in 1938 by Hahn, Otto and Fritz Strassman, and was explained in 1939 by Lise Meitner and Otto Frisch. Fission energy can be obtained by bombarding the fissionable Isotope Uranium -235 with slow neutrons in order to split it. Because this reaction releases an average of 2.5 neutrons, a chain reaction is possible, provided at least one neutron per fission is captured by another nucleus and causes a second fission. In a Nuclear Reactor , where the chain reaction is controlled, the number must be exactly 1 in order to maintain a steady reaction rate. Moreover, the fuel for fusion reactors, deuterium, is readily available in large amounts.