Extrapolation of creep strength by fracture energy for 316FR stainless steel at 823 K

823Kにおける316FR鋼のクリープ強度の外挿評価

永江 勇二 ; 浅山 泰 

Nagae, Yuji; Asayama, Tai

316FR stainless steel is to be used for a reactor vessel and internals for fast reactors, which the design life is 60 years and the operating temperature is 823 K. This paper describes an extrapolation approach by fracture energy for creep strength of allowable stress in time-dependent regime. Change in fracture energy is assumed to be expressed as a power-law function of time to failure and energy density rate. The energy density rate is calculated using initial stress, rupture elongation and time to rupture. It is important to evaluate a change in rupture elongation for extrapolation of creep-strength at 823 K. Time to rupture at 823 K is estimated and extrapolated based on the fracture energy approach. This paper shows the validity of extending to 60 years design using Larson-Miller parameter, compared with the estimation by the fracture energy approach.