Influencing factors for improving accuracy in prediction of stress corrosion crack growth rate in boiling water reactor operational condition -2 - The effect of single overload on SCC growth behavior

The effect of a single overload on SCC growth behavior was addressed in this study by SCC testing using a CDCB specimen and an ACPD technique under simulated BWR water. The ratio of the stress intensity factors K _OL/K_{SCC test}, i.e. that of the single overload, K _OL, divided by that of the SCC testing, K_SCC-test, is defined as a single overload level in this study. With this in mind, changes in ACPDs, i.e. those regarded as the SCC growth behaviors, were measured after single overload levels of 1.05, 1.10, 1.20 and 1.50 respectively were applied. Retardations of SCC growth behavior were observed at the single overload levels of 1.10, 1.20, and 1.50, since the ACPDRs were reduced following the application of single overload levels without significant variations in water quality factors, such as electric conductivity and the DO concentration in the simulated BWR water. Therefore, it emerged that applying single overload levels of 1.10, 1.20, and 1.50 reduced the SCC growth rate, since the ACPDR proportional to the SCC growth rate was reduced following the single overload application. The ACPDR after the single overloads were reduced by about 14, 59 and 66% at single overload levels of 1.10, 1.20 and 1.50, respectively.