PWSCC susceptibility of mill annealed alloy 600 in reactor coolant system water during the high pH operation

For the reduction of radiation source in the primary water system of a PWR, elevated pH operation to the pH value of 7.4 at 300 deg C is known to be effective. There is a need to verify the effect of elevated pH operation on materials integrity of PWR primary circuit, and a research program is under way to study and verify the optimum pH and/or Li concentration from the viewpoint of radiation source reduction and materials integrity. Constant extension rate testing (CERT) to investigate tHE PWSCC susceptibility for mill annealed Alloy 600 was performed under the various RCS water chemistry conditions. In this paper, PWSCC susceptibility of mill annealed Alloy 600 with the change of RCS water chemistry conditions will be discussed, and also the current status of the long term verification test to confirm the materials integrity of PWR primary system will be introduced. (authors). 3 figs., 1 tab., 3 refs