Creep-Fatigue Evaluation Methodologies and Related Issues for Japan Sodium Cooled Fast Reactor (JSFR)

This paper describes the main topics on creep-fatigue evaluation methodologies for the Japan Sodium Cooled Fast Reactor (JSFR). JSFR's operating temperature is 550C and design life is 60 years with key technologies in terms of creep-fatigue being the adoption of new materials, 316FR and Mod.9Cr-1Mo steel, and the development of evaluation methodologies for those materials: 316FR is low-carbon nitrogen-added 316 steel which has superior creep properties and will be used for the reactor vessel and internal structures. Mod.9Cr-1Mo steel will be applied to most of the coolant systems including primary piping, intermediate heat exchangers, secondary piping and steam generators. Creep-fatigue evaluation methodologies for those materials are being developed concentrating on capturing long-term materials behavior and strength so that the evaluation of 60-year design is justified, and simplified evaluation methods for strain ranges and stress relaxation behaviors applicable to JSFR structures which have various configurations and loading conditions are also being developed. The results of R&D will be incorporated in a JSME (Japan Society of Mechanical Engineers) code for the design and construction of fast reactors.