US Nuclear Regulatory Commission research for primary system integrity regulations

This report summarizes results of an experimental testing program focused on establishing the fatigue crack growth behavior of several commercial pressure vessel and piping steels typically used in light water reactors. Testing was done in a simulated boiling water reactor (BWR) primary water environment (1230 psig, 550/sup 0/F demineralized water). The data obtained were analyzed using linear elastic fracture mechanics principles and, in the case of the reactor pressure vessel alloy steel, compared to existing ASME design codes. The results show that crack growth rates are increased in this BWR water environment by decreasing the frequency of cyclic loading or increasing the mean load present during the load cycle. However, in the case of the pressure vessel alloy steel, these effects are moderated by transverse secondary microcracking, which is a manifestation of a crack tip chemistry interaction for this environment/material pair. This behavior is consistent with previous GE experience with in-service cracking in pressure vessel components, wherein analytic projections of cracking rates always tend to overpredict crack depths when compared to actual field observations. The results for the Type-304 stainless steel and the Inconel 600 establish threshold values on cyclic loading frequency for intergranular stress corrosion cracking behavior in thesemore » two material/environment pairs.« less

J.L. Yuen

Papers

Fatigue growth in piping and rpv steels in simulated BWR water environment