ABSTRACT
Breeder reactors need fast neutrons for breeding and fission. Water is not suitable for the cooling of the fuel elements. The high density of energy requires a coolant with a very good thermal conductivity. Corrosion by flowing sodium is caused by the solubility of metals in the liquid metal or by chemical reactions of constituents of materials with impurities in the sodium. The reactions may cause the formation of more or less adherent layers or the loss of the reaction products due to solution or spalling off by the flowing liquid. Since the core components – fuel-element clads, wrapper tubes, distance holders, etc. – are exposed to the coolant at the highest temperature level, their materials tend to lose constituents to the flowing sodium. The uptake of carbon influences the microstructure, since carbides precipitate in the region of the highest concentrations.
