Creep and Low Cycle Fatigue Behaviour of Fast Reactor Structural Materials

Low cycle fatigue and long-term creep properties, as well as compatibility with liquid sodium coolant, govern the choice of materials for out-of-core structural and steam generator components of sodium cooled fast reactors (SFRs). 316L(N) SS is preferred for all high temperature structural components while modified 9Cr-1Mo steel is preferred for the steam generator components for which resistance to stress corrosion cracking in steam is an additional requirement. A thorough understanding of the deformation, damage and fracture behavior of these materials helps to improve confidence in the design of the components and performance in service, and also to develop improved materials. The cyclic and creep deformation behavior have to be understood under complex stress conditions and in the liquid sodium, o erating environment. This paper highlights the creep, low cycle fatigue and creep-fatigue properties of current SFR materials in air and sodium environments, and discusses the studies underway to develop improved materials for future SFRs for longer design life.