Thermal Shielding

in nuclear engineering, means for protecting the external parts of a reactor—for example, concrete components of biological shielding, which cannot withstand great increases in temperature—from heat-generating radiation emitted by the reactor core. Thermal shielding is created by a layer of heat-resistant material, such as steel, cast iron, or sand, which reduces the neutron and gamma-ray fluxes to levels at which no great temperature gradients, and consequently no mechanical stresses, are created in the shielded parts. Thermal shielding is mounted near the core, behind the reflector, and may be specially cooled. In certain types of reactors the walls of the reactor vessel are used as thermal shielding.