Studies of the effects resulting from exposure of materials to neutron bombardment in nuclear reactors can be made much more quantitative if the energy-level distribution of the neutrons is known. Such a distribution is commonly called a neutron spectrum. The neutron energies range from as low as 1 1010 MeV in the thermal-neutron region, to over 18 MeV in the fast region. This extremely wide range can be conveniently handled, however, using a system of 25 or even fewer groups each defining a precise energy range, with the neutron population within those energy bounds being tabulated as the neutron spectrum. |