XI.M24 (NUREG-1801 R0)
XI.M24 COMPRESSED AIR MONITORING
Program Description
The program consists of inspection, monitoring, and testing of the entire system, including (a) frequent leak testing of valves, piping, and other system components, especially those made of carbon steel; and (b) preventive monitoring that checks air quality at various locations in the system to ensure that oil, water, rust, dirt, and other contaminants are kept within the specified limits. The aging management program (AMP) provides for timely corrective actions to ensure that the system is operating within specified limits.
The AMP is based on results of the plant owners response to the U.S. Nuclear Regulatory Commission (US NRC) Generic Letter (GL) 88-14, augmented by previous US NRC Information Notices IN 81-38, IN 87-28, and IN 87-28 S1, and by the Institute of Nuclear Power Operations Significant Operating Experience Report (INPO SOER) 88-01. The US NRC GL 88-14, issued after several years of study of problems and failures of instrument air systems, recommends each holder of an operating license to perform an extensive design and operations review and verification of its instrument air system. The GL 88-14 also recommends the licensees to describe their program for maintaining proper instrument air quality. The AMP also incorporates provisions conforming to the guidance of the Electric Power Research Institute (EPRI) NP-7079(Archived), issued in 1990, to assist utilities in identifying and correcting system problems in the instrument air system and to enable them to maintain required industry safety standards. Subsequent to these initial actions by all plant licensees to implement an improved AMP, some utilities decided to replace their instrument air system with newer models and types of equipment. The EPRI then issued TR-108147(Archived), which addresses maintenance of the latest compressors and other instrument air system equipment currently in use at those plants. The American Society of Mechanical Engineers operations and maintenance standards and guides (ASME OM-S/G-1 998, Part 17) provides additional guidance to the maintenance of the instrument air system by offering recommended test methods, test intervals, parameters to be measured and evaluated, acceptance criteria, corrective actions, and records requirements.
Evaluation and Technical Basis
- 1. Scope of Program: The program manages the effects of corrosion and the presence of unacceptable levels of contaminants on the intended function of the compressed air system. The AMP includes frequent leak testing of valves, piping, and other system components, especially those made of carbon steel, and a preventive maintenance program to check air quality at several locations in the system.
- 2. Preventive Actions: The system air quality is monitored and maintained in accordance with the plant owner's testing and inspection plans, which are designed to ensure that the system and equipment meet specified operability requirements. These requirements are prepared from consideration of manufacturer's recommendations for individual components and guidelines based on ASME OM-S/G-1 998, Part 17; ISA-S7.0.01-1996; EPRI NP-7079(Archived); and EPRI TR-108147(Archived). The preventive maintenance program addresses various aspects of the inoperability of air-operated components due to corrosion and the presence of oil, water, rust, and other contaminants.
- 3. Parameters Monitored/Inspected: Inservice inspection (ISI) and testing is performed to verify proper air quality and confirm that maintenance practices, emergency procedures, and training are adequate to ensure that the intended function of the air system is maintained.
- 4. Detection of Aging Effects: Guidelines in EPRI NP-7079(Archived), EPRI TR-108147(Archived), and ASME OM-S/G-1 998, Part 17, ensure timely detection of degradation of the compressed air system function. Degradation of the piping and any equipment would become evident by observation of excessive corrosion, by the discovery of unacceptable leakage rates, and by failure of the system or any item of equipment to meet specified performance limits.
- 5. Monitoring and Trending: Effects of corrosion and the presence of contaminants are monitored by visual inspection and periodic system and component tests, including leak rate tests on the system and on individual items of equipment. These tests verify proper operation by comparing measured values of performance with specified performance limits. Test data are analyzed and compared to data from previous tests to provide for timely detection of aging effects.
- 6. Acceptance Criteria: Acceptance criteria is established for the system and for individual equipment that contain specific limits or acceptance ranges based on design basis conditions and/or equipment vendor specifications. The testing results are analyzed to verify that the design and performance of the system is in accordance with its intended function.
- 7. Corrective Actions: Corrective actions are taken if any parameters are out of acceptable ranges, such as moisture content in the system air. 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: The site corrective actions program, quality assurance (QA) procedures, site review and approval process, 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: Potentially significant safety-related problems pertaining to air systems have been documented in US NRC IN 81-38, IN 87-28, IN 87-28 S1 and license event report (LER) 50-237/94-005-3. Some of the systems that have been significantly degraded or have failed due to the problems in the air system include the decay heat removal, auxiliary feedwater, main steam isolation, containment isolation, and fuel pool seal system. As a result of US NRC GL 88-14 and consideration of INPO SOER 88-01, EPRI NP-7079(Archived), and EPRI TR-108147(Archived), performance of air systems has improved significantly.
References
ASME OM-S/G-1 998, Part 17, Performance Testing of Instrument Air Systems Information Notice Light-Water Reactor Power Plants, 1ISA-S7.0.1-1996, "Quality Standard for Instrument Air," American Society of Mechanical Engineers, New York, NY, 1998.
EPRI NP-7079(Archived), Instrument Air System: A Guide for Power Plant Maintenance Personnel, Electric Power Research Institute, Palo Alto, CA., December 1990.
EPRI/NMAC TR-108147(Archived), Compressor and Instrument Air System Maintenance Guide: Revision to NP-7079, Electric Power Research Institute, Palo Alto, CA., March 1998.
INPO SOER 88-01, Instrument Air System Failures, May 18, 1988.
US NRC Generic Letter 88-14, Instrument Air Supply Problems Affecting Safety-Related Equipment, U.S. Nuclear Regulatory Commission, August 8, 1988.
US NRC Information Notice 81-38, Potentially Significant Equipment Failures Resulting from Contamination of Air-Operated Systems, U.S. Nuclear Regulatory Commission, December 17, 1981.
US NRC Information Notice 87-28, Air Systems Problems at U.S. Light Water Reactors, U.S. Nuclear Regulatory Commission, June 22, 1987.
US NRC Information Notice 87-28, Supplement 1, Air Systems Problems at U.S. Light Water Reactors, U.S. Nuclear Regulatory Commission, December 28, 1987.
US NRC Licensee Event Report LER 50-237/94-005-3, Manual Reactor Scram due to Loss of Instrument Air Resulting from Air Receiver Pipe Failure Caused by Improper Installation of Threaded Pipe during Initial Construction,] U.S. Nuclear Regulatory Commission, April 23, 1997.