Empirical equations of crack growth rates of neutron irradiated stainless steel under simulated BWR core conditions

Kasahara, Shigeki; Fukuya, Koji*; Chimi, Yasuhiro; Fujii, Katsuhiko*; Hata, Kuniki 

Disposition curves of crack growth rates (CGR) of stainless steel in appropriate consideration of IASCC are necessary for structural integrity assessment of reactor internals of BWRs. This paper describes empirical equations development of CGR (da/dt), as functions of stress intensity factors (K) and neutron dose (F) to contribute to improvement of the structural integrity assessment. Development started from a formula of da/dt=MK, and on the assumption that "M" and "n" tend to be saturated with increasing F. Datasets for fitting were prepared consisting of CGR, F and K from the results of PIE under simulated NWC conditions. Data fitting with least square method was applied to the datasets to obtain the equation. The results from the empirical equation were compared with the measured crack growth data, and validity of the equations were discussed from the viewpoints of statistical analysis.