Neutron Radiation:

The shielding of neutrons introduces several complications since of the huge range of energy which must be considered. On low energies (less than 0.1 MeV), low mass number materials, like as hydrogen in H2O, are best for slowing down neutrons. At those energies, the cross section for interaction along with hydrogen is high (around 20 barns), and the energy loss in a collision is high. Materials holding hydrogen are known as hydrogenous material, and their price as a neutron shield is determined through their hydrogen content. Water ranks high and is possibly the best neutron shield material along with the benefits of low cost, while it is a poor absorber of gamma radiation.

Water also gives a ready means for removing the heat produced through radiation absorption. On higher energies (10 MeV), the cross section for interaction along with hydrogen (1 barn) is not as effectual in slowing down neutrons. For offset this reduces in cross section along with increased neutron energy, materials within good inelastic scattering properties, like as iron, are used. Those materials cause a big modification in neutron energy after collision for high energy neutrons but have little effect on neutrons at lower energy, under 0.1 MeV.