Structural materials for nuclear reactor primary coolant circuits

Purpose: To reduce the operators' exposure upon inspection work or the like by greatly decreasing the radioactivity accumulation amount at the surfaces in the structural materials for nuclear reactor primary coolant circuits. Constitution: Equipments and pipeways for BWR type reactors, feedwater systems, recycling systems and coolant circuits are made of stainless steels. Vapor deposited metal layers are formed at the surface of stainless steel structural materials in contact with coolants. Concentrates of metals not activated when intruded into the nuclear reactor or other non-activating isotope metals are used as the material for vapor deposition metals. Further, the thickness of the vapor deposition metal layers is properly determined depending on the structural materials on which the vapor deposition metal layers are formed. Since the formation of corrosion oxide films is greatly reduced, deposition of granular radioactive materials is decreased. Accordingly, the maintenance cost can greatly be decreased. (Takahashi, M.)