MATERIALS INTEGRITY UNDER ELEVATED pH CONTROL OF RCS WATER FOR THE REDUCTION OF RADIATION SOURCE

摘要

For the reduction of radiation source in the primary water system of a PWR, elevated pH operation to the pH value of 7.3 at 285°C is known to be effective. Research program is under way to study and verify the optimum pH and Li concentration from the viewpoint of radiation source reduction and materials integrity. PWSCC susceptibility for mill annealed Alloy 600 was studied by constant extension rate testing under the various RCS water chemistry conditions, and a PWSCC iso-susceptibility diagram on boron and lithium diagram was obtained. Long term verification tests were performed for structural materials in RCS using various types of SCC specimens. According to the results of verification tests, no detrimental effect on materials integrity was observed for elevated pH operation.