Gamma-ray shielding material

Purpose: To provide γ-ray shielding materials which can be used without reducing the heat resistivity even at high temperature and, which are particularly suitable for the primary main coolant recycling pumps in FBR type reactors. Constitution: The shielding materials according to this invention are constituted by layering a plurality of high melting metal materials at a low specific gravity each formed into a spherical shape and including therein low melting metal materials at a high specific gravity. Since the shielding materials can be retained in the spherical shape by the high melting outer metals and point-to-point contact between each of the layered shielding materials can be maintained even under a high temperature, γ-ray shielding effect can be increased by the inner metal of a high specific gravity without reducing the heat resistivity. (Kamimura, M.)