Development of 2012 edition of JSME code for design and construction of fast reactors, 5; Creep-fatigue evaluation method for 316FR stainless steel

Nagae, Yuji ; Takaya, Shigeru  ; Asayama, Tai 

The most important failure mode to be prevented in the design is creep-fatigue at elevated temperatures in fast reactors. 316FR stainless steel is a candidate material for the reactor vessel and internal structures. Development of the procedure for evaluating creep-fatigue life is essential. The method for evaluating creep-fatigue life implemented in the Japan Society Mechanical Engineers code is based on the time fraction rule for austenitic stainless steel such as SUS304. Necessary equations such as fatigue curve and creep rupture curve for calculation of creep-fatigue life are evaluated, and the predicted creep-fatigue life by using the time fraction rule in 316FR stainless steel is compared with experimental data. The longest time to failure is about 100,000 h for evaluating creep-fatigue life. Fatigue curve, creep rupture curve, stress-strain curve and creep strain curve are provided for calculating creep-fatigue life. The creep-fatigue life is predicted within a factor of 2 even the test condition of the longest time to failure. Furthermore, comparison with the ductility exhaustion method was done to investigate the conservatism of the proposed method. Finally, the procedure based on the time fraction rule for evaluation of creep-fatigue life is proposed in 316FR stainless steel.