On corrosion of materials for LMFBR in high temperature sodium

Deterioration of material caused by service in generally outside the scope of the ASME code applied for design of LMFBR is to consider. In this code, the rules do not provide methods to evaluate deterioration occurred in service as a result of corrosion, mass transfer phenomenon, radiation effects or other material stability and it is responsibility of the owner to select material. In this report, general corrosion and intergranular corrosion to be considered as initiation of crack are summarized. 1. Corrosion of the materials for LMFBR are affected by sodium temperature, flow rate, oxygen concentration. But, because of small rate of general corrosion, decrease of thickness due to corrosion are negligible for design. However, corrosion behavior of the fuel cladding tube under high heat flux are important from the point of view of the production of active corrosion products. 2. Intergranular corrosion of the materials in high temperature sodium are caused by selective leaching of the allowing element as nickel and chromium through the grain boundary. As it is considered that grain boundary strength is reduced by the intergranular corrosion, the study on the corrosion is important. (author)