Chapter 8 - Diffusion in Nuclear Materials

Abstract

The phenomenon of diffusion plays a key role in the development, fabrication, operation, and irradiation of nuclear materials in a number of ways. Important processes pertaining to reactor environment, such as grain growth, sintering, recrystallization, creep and embrittlement are governed by the rate of diffusion of various species in nuclear materials. The present chapter deals with the diffusion behavior of different nuclear materials such as nuclear fuels, clad materials, and reactor structural materials. The data available on diffusion properties of these classes of materials have been reviewed. The fundamental aspects which are vital to the diffusion of different species in these materials have been brought out. Different mechanisms of diffusion involved and the influence of the defects and impurities present in the system have been discussed. The chapter examines the self-diffusion and impurity diffusion behavior in various U-, Pu-, and Th-based metallic and ceramic nuclear fuels and also outlines the difficulties encountered in conducting experiments to determine these properties. Also, the characteristics of diffusion coefficients and their temperature dependence in some of the technologically important metals and alloy systems, widely used in nuclear reactors, such as Al, Zr, Zircaloy, Zr–Nb alloys, stainless steels of various grades, and Ni-based superalloys has also been included.