Theoretical Analysis of Corrosion by Liquid Sodium and Sodium-Potassium Alloys

Abstract

Sodium and its alloys such as sodium-potassium (NaK) have been used or considered as coolants in nuclear reactors, including space reactor systems. One potentially serious problem of using a liquid metal/alloy as a coolant is its corrosive effect on its container materials. In the present study, an analytical model has been developed to analyze the corrosion/deposition rates of steels exposed to flowing NaK and Na. In this model, the diffusion of steel constituents in the solid and the transport of the corrosion products in the liquid are coupled at the liquid/solid interface. The model can be used to predict the steel constituent distributions in the corrosion layer as well as recession of the solid walls. Both isothermal and non-isothermal cases are considered. It is expected that the theoretical model can serve as a tool for structure material selection and for the design of the structural components in a liquid metal reactor.