XI.M21 (NUREG-1801 R0)
XI.M21 CLOSED-CYCLE COOLING WATER SYSTEM
Program Description
The program includes (a) preventive measures to minimize corrosion and (b) surveillance testing and inspection to monitor the effects of corrosion on the intended function of the component. The program relies on maintenance of system corrosion inhibitor concentrations within specified limits of Electric Power Research Institute [EPRI] TR-107396(Archived) to minimize corrosion. Surveillance testing and inspection in accordance with standards in EPRI TR-107396(Archived) for closed-cycle cooling water (CCCW) systems is performed to evaluate system and component performance. These measures will ensure that the CCCW system and components serviced by the CCCW system are performing their functions acceptably.
Evaluation and Technical Basis
- 1. Scope of Program: A CCCW system is defined as part of the service water system that is not subject to significant sources of contamination, in which water chemistry is controlled and in which heat is not directly rejected to a heat sink. The program described in this section applies only to such a system. If one or more of these conditions are not satisfied, the system is to be considered an open-cycle cooling water system. The staff notes that if the adequacy of cooling water chemistry control can not be confirmed, the system is treated as an open-cycle system as indicated in Action III of Generic Letter (GL) 89-13.
- 2. Preventive Actions: The program relies on the use of appropriate materials, lining, or coating to protect the underlying metal surfaces and maintenance of system corrosion inhibitor concentrations within specified limits of EPRI TR-107396(Archived) to minimize corrosion. The program includes monitoring and control of cooling water chemistry to minimize exposure to aggressive environments and application of corrosion inhibitor in the CCCW system to mitigate general, crevice, and pitting corrosion.
- 3. Parameters Monitored/Inspected: The aging management program (AMP) monitors the effects of corrosion by surveillance testing and inspection in accordance with standards in EPRI TR-107396(Archived) to evaluate system and component performance. For pumps, the parameters monitored include flow and discharge and suction pressures. For heat exchangers, the parameters monitored include flow, inlet and outlet temperatures, and differential pressure.
- 4. Detection of Aging Effects: Control of water chemistry does not preclude corrosion at locations of stagnant flow conditions or crevices. Degradation of a component due to corrosion would result in degradation of system or component performance. The extent and schedule of inspections and testing in accordance with EPRI TR-107396(Archived), assure detection of corrosion before the loss of intended function of the component. Performance and functional testing in accordance with EPRI TR-107396(Archived), ensures acceptable functioning of the CCCW system or components serviced by the CCCW system. For systems and components in continuous operation, performance adequacy is determined by monitoring data trends for evaluation of heat transfer fouling, pump wear characteristics, and branch flow changes. Components not in operation are periodically tested to ensure operability.
- 5. Monitoring and Trending: The frequency of sampling water chemistry varies and can occur on a continuous, daily, weekly, or as needed basis, as indicated by plant operating conditions. Per EPRI TR-107396(Archived), performance and functional tests are performed at least every 18 months to demonstrate system operability, and tests to evaluate heat removal capability of the system and degradation of system components are performed every five years. The testing intervals may be adjusted on the basis of the results of the reliability analysis, type of service, frequency of operation, or age of components and systems.
- 6. Acceptance Criteria: Corrosion inhibitor concentrations are maintained within the limits specified in the EPRI water chemistry guidelines for CCCW. System and component performance test results are evaluated in accordance with the guidelines of EPRI TR-107396(Archived). Acceptance criteria and tolerances are also based on system design parameters and functions.
- 7. Corrective Actions: Corrosion inhibitor concentrations outside the allowable limits are returned to the acceptable range within the time period specified in the EPRI water chemistry guidelines for CCCW. If the system or component fails to perform adequately, corrective actions are taken in accordance with EPRI TR-107396(Archived). As discussed in the appendix to this report, the staff finds the requirements of 10 CFR Part 50, Appendix B, acceptable in addressing corrective actions.
- 8. Confirmation Process: Site quality assurance (QA) procedures, review and approval processes, and administrative controls are implemented in accordance with the requirements of 10 CFR Part 50, Appendix B. As discussed in the appendix to this report, the staff finds the requirements of 10 CFR Part 50, Appendix B, acceptable in addressing the confirmation process and administrative controls.
- 9. Administrative Controls: See Item 8, above.
- 10. Operating Experience: Degradation of closed-cycle cooling water systems due to corrosion product buildup (US NRC Licensee Event Report [LER] 93-029-00) or through-wall cracks in supply lines (US NRC LER 91-019-00) has been observed in operating plants. Accordingly, operating experience demonstrates the need for this program.
References
EPRI TR-107396(Archived), Closed Cooling Water Chemistry Guidelines, Electric Power Research Institute, Palo Alto, CA, November 1997.
US NRC Generic Letter 89-13, Service Water System Problems Affecting Safety-Related Equipment, U.S. Nuclear Regulatory Commission, July 18, 1989.
US NRC Generic Letter 89-13, Supplement 1, Service Water System Problems Affecting Safety-Related Equipment, U.S. Nuclear Regulatory Commission, April 4, 1990.
US NRC Licensee Event Report LER #91-019-00, Loss of Containment Integrity due to Crack in Component Cooling Water Piping, October 26, 1991.
US NRC Licensee Event Report LER #93-029-00, Inoperable Check Valve in the Component Cooling System as a Result of a Build-Up of Corrosion Products between Valve Components, December 13, 1993.