Evaluation of environmental fatigue life for light water reactor components

The existing fatigue design procedures for LWR components do not define the effects of the reactor coolant environment. Recent laboratory data suggested that environmental effects may invalidate the Code fatigue curves. This paper summarizes fatigue evaluation procedures and evaluation results of typical components in Japanese LWRs, taking environmental effects into consideration. Environmental fatigue correction factors have been developed by Higuchi and Iida as a function of strain rate, temperature and dissolved oxygen content, based on laboratory test data. However, these factors are applicable only under conditions where the environmental parameters are constant. In this paper, the factors were modified so as to be applied to conditions where the environmental parameters are variable as is the case with actual LWRs. This paper also presents calculations of fatigue usage for the BWR reactor pressure vessel nozzle and the PWR steam generator nozzle, using the modified correction factors in order to evaluate the environmental effects