The Effect of Aging on the PWR Chemical and Volume Control System

摘要

The effect of aging on the PWR Chemical and Volume Control System (CVCS) has been evaluated. Since this system provides many normal and emergency operating functions, it is important to understand the effect of aging to detect and correct these instances before failure. A detailed review of the NPRDS and LER data bases, in conjunction with a review of industry and regulatory experience and research, indicate that age-related failures have occurred. These failures resulted in significant effects on plant operation, including reactivity excursions, and pressurizer level transients. A representative plant of each PWR NSSS design was visited to obtain specific information on system inspection, surveillance, and monitoring. The majority of these inspections are performed in accordance with ASME Section XI, 10CFR 50 Appendix J, and technical specification requirements. The plants visited used Reliability Centered Maintenance techniques to ensure adequate surveillance and monitoring. A parametric study was performed to assess the effect of system aging on Core Damage Frequency (CDF). Since the majority of this system's functions are not safety-related, the impact of failures is not normally assessed in PRAs. However, the High Pressure Injection system is, and this system uses many of the same components that are included in the CVCS boundaries. The results of this study indicated that human errors and motor-operated valve failures were primary contributors to an increased CDF.