Chadwick discovered neutron in 1932. Generally, neutrons are generated during radioactive chain reactions in a power reactor. Neutron is subatomic particle pres­ent in almost all nuclides (except normal hydrogen isotope or protium) with a mass of 1.67 x 10-27 kg and has no electrical charge.

Neutrons are classified based on their kinetic energies. Although there is no clear boundary between the categories, the following limits can be used as a useful guideline:

Cold neutrons (<0.003 eV), slow (thermal) neutrons (0.003-0.4 eV), slow (epithermal) neutrons (0.4-100 eV), intermediate neutrons (100eV-200keV), fast neutrons (200keV-10 MeV), high-energy (relativistic) neutrons (>10 MeV). Note: 1 eV = 1.6 x 10~19J.

Generally, thermal neutrons are associated with a kinetic energy of 0.025 eV that translates into a neutron speed of 2200 m s-1!

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