Nuclear Fission and Nuclear Fusion
Nuclear fission: The splitting of a heavier atom like that of uranium – 235 into a number of fragments of much smaller mass, by suitable bombardment with sub-atomic particles with liberation of huge amount of energy is called Nuclear fission. Hahn and Startsman discovered that when uranium-235 is bombarded with neutrons, it splits up into two relatively lighter elements.
+ Huge amount of energy
Spallation reactions are similar to nuclear fission. However, they differ by the fact that they are brought by high energy bombarding particles or photons.
Elements capable of undergoing nuclear fission and their fission products. Among elements capable of undergoing nuclear fission, uranium is the most common. The natural uranium consists of three isotopes, namely , and . Of the three isomers of uranium, nuclear fission of and are more important. Uranium-238 undergoes fission by fast moving neutrons while undergoes fission by slow moving neutrons; of these two, fission is of much significance. Other examples are and .
Uranium-238, the most abundant (99.3%) isotope of uranium, although itself does not undergo nuclear fission, is converted into plutonium-239.
Which when bombarded with neutrons, undergo fission to emit three neutrons per plutonium nucleus. Such material like U-238 which themselves are non-fissible but can be converted into fissible material (Pu-239) are known as fertile materials.