XI.M24 (NUREG-2191 R0)
XI.M24 COMPRESSED AIR MONITORING
Program Description
The purpose of the compressed air monitoring program is to provide reasonable assurance of the integrity of the compressed air system downstream of the instrument air dryers. The program consists of monitoring moisture content, corrosion, and performance of the compressed air system. This includes (a) preventive monitoring of water (moisture) and other potentially corrosive contaminants to keep within the specified limits; and (b) opportunistic inspection of components for indications of loss of material due to corrosion.
This aging management program (AMP) does not change the applicant’s docketed response to U.S. Nuclear Regulatory Commission (US NRC) Generic Letter (GL) 88-14 for the rest of its operations. The AMP also incorporates the air quality provisions provided in the guidance of the Electric Power Research Institute (EPRI) TR-108147(Archived). The American Society of Mechanical Engineers (ASME) operations and maintenance standards and guides (ASME OM-2012, Division 2, Part 28) provides additional guidance for maintenance of the instrument air system by offering recommended test methods, test intervals, parameters to be measured and evaluated, and records requirements.
Evaluation and Technical Basis
- 1. Scope of Program: The program manages the aging effects of loss of material due to corrosion in compressed air system components located downstream of the compressed air system air dryers, or for components exposed to an internal gas environment (e.g., nitrogen-filled accumulators). Aging effects associated with components located upstream of the air dryers, or those exposed to an air environment that is not subject to the preventive actions of this program, are managed by Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report AMP XI.M38, “Inspection of Internal Surfaces in Miscellaneous Piping and Ducting Components.”
- 2. Preventive Actions: For the purposes of aging management, moisture and other corrosive contaminants in the system’s air are maintained below specified limits to provide reasonable assurance that the system and components maintain their intended functions. These limits are prepared from consideration of the manufacturer’s recommendations for individual components and guidelines based on ASME OM-2012, Division 2, Part 28; ANSI/ISA-7.0.01-1996; and EPRI TR–108147(Archived).
- 3. Parameters Monitored or Inspected: Periodic air samples are taken and analyzed for moisture content and corrosive contaminants. Opportunistic visual inspections of accessible internal surfaces are performed for signs of corrosion and abnormal corrosion products that might indicate a loss of material within the system.
- 4. Detection of Aging Effects: The program periodically samples and tests the air in the compressed system in accordance with industry standards (i.e., ANSI/ISA-7.0.01-1996). Compressed air systems have in-line dew point instrumentation that either continuously monitors using an automatic alarm system or is checked at least daily to determine whether moisture content is within the recommended range. Additionally, opportunistic visual inspections of component internal surfaces exposed to an air-dry environment are performed for signs of loss of material due to corrosion. Guidance for inspection frequency and inspection methods of these components is provided in standards or documents such as ASME OM-2012, Division 2, Part 28.
- Inspections and tests are performed by personnel qualified in accordance with site procedures and programs to perform the specified task.
- 5. Monitoring and Trending: If daily readings of system dew points are taken, they are recorded and trended. Air quality analysis results are reviewed to determine if alert levels or limits have been reached or exceeded. This review also checks for unusual trends. ASME OM-2012, Division 2, Part 28, provides guidance for monitoring and trending data. The effects of corrosion are monitored by visual inspection. Test data are analyzed and compared to data from previous tests to provide for the timely detection of aging effects on passive components.
- 6. Acceptance Criteria: Acceptance criteria for air quality moisture limits are established based on accepted industry standards, such as American National Standards Institute/International Society of Automation (ANSI/ISA)-7.0.01-1996. Internal surfaces do not show signs of corrosion (general, pitting, and crevice) that could indicate the potential loss of function of the component. Suppliers’ certifications can be used to demonstrate that bottled gases meet acceptable quality standards.
- 7. Corrective Actions: Results that do not meet the acceptance criteria are addressed in the applicant’s corrective action program under those specific portions of the quality assurance (QA) program that are used to meet Criterion XVI, “Corrective Action,” of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix B. Appendix A of the Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report describes how an applicant may apply its 10 CFR Part 50, Appendix B, QA program to fulfill the corrective actions element of this AMP for both safety-related and nonsafety-related structures and components (SCs) within the scope of this program.
- Corrective actions are taken if any parameters, such as moisture content in the system air, are out of acceptable ranges, or if corrosion is identified on internal surfaces.
- 8. Confirmation Process: The confirmation process is addressed through those specific portions of the QA program that are used to meet Criterion XVI, “Corrective Action,” of 10 CFR Part 50, Appendix B. Appendix A of the GALL-SLR Report describes how an applicant may apply its 10 CFR Part 50, Appendix B, QA program to fulfill the confirmation process element of this AMP for both safety-related and nonsafety-related SCs within the scope of this program.
- 9. Administrative Controls: Administrative controls are addressed through the QA program that is used to meet the requirements of 10 CFR Part 50, Appendix B, associated with managing the effects of aging. Appendix A of the GALL-SLR Report describes how an applicant may apply its 10 CFR Part 50, Appendix B, QA program to fulfill the administrative controls element of this AMP for both safety-related and nonsafety-related SCs within the scope of this program.
- 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, Supplement 1; and Licensee Event Report 237/94-005-3. Some of the systems that have been significantly degraded or that 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 systems. In 2008, one plant incurred an unplanned reactor trip from a failure of a mechanical joint in the instrument air system (US NRC IN 2008-06). Nevertheless, as a result of US NRC GL 88-14 and consideration of INPO SOER 88-01 and EPRI TR–108147(Archived), performance of air systems has improved significantly.
- The program is informed and enhanced when necessary through the systematic and ongoing review of both plant-specific and industry operating experience including research and development such that the effectiveness of the AMP is evaluated consistent with the discussion in Appendix B of the GALL-SLR Report.
References
10 CFR Part 50, Appendix B, “Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants.” Washington, DC: U.S. Nuclear Regulatory Commission. 2016.
ANSI. ANSI/ISA-7.0.01-1996, “Quality Standard for Instrument Air.” Washington, DC: American National Standards Institute. 1996.
ASME. ASME OM-2012, “Performance Testing of Instrument Air Systems in Light-Water Reactor Power Plants.” Division 2, Part 28. New York, New York: American Society of Mechanical Engineers. 2012.
EPRI. EPRI TR–108147(Archived), “Compressor and Instrument Air System Maintenance Guide: Revision to NP-7079.” Palo Alto, California: Electric Power Research Institute. March 1998.
INPO. INPO Significant Operating Experience Report 88-01, “Instrument Air System Failures.” Atlanta, Georgia: Institute of Nuclear Power Operations. May 1988.
Licensee Event Report 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.” https://lersearch.inl.gov/LERSearchCriteria.aspx. April 3, 1997.
US NRC. Generic Letter 88-14, “Instrument Air Supply Problems Affecting Safety-Related Components.” Agencywide Documents Access and Management System (ADAMS) Accession No. ML031130440. Washington, DC: U.S. Nuclear Regulatory Commission. August 8, 1988.
_____. Information Notice 81-38, “Potentially Significant Components Failures Resulting from Contamination of Air-Operated Systems.” ADAMS Accession No. ML 8107230040. Washington, DC: U.S. Nuclear Regulatory Commission. December 17, 1981.
_____. Information Notice 87-28, “Air Systems Problems at U.S. Light Water Reactors.” ADAMS Accession No. ML031130569. Washington, DC: U.S. Nuclear Regulatory Commission. June 22, 1987.
_____. Information Notice 87-28, “Air Systems Problems at U.S. Light Water Reactors.” Supplement 1. ADAMS Accession No. ML031130670. Washington, DC: U.S. Nuclear Regulatory Commission. December 28, 1987.
_____. Information Notice 2008-06, “Instrument Air System Failure Resulting In Manual Reactor Trip.” ADAMS Accession No. ML073540243. Washington, DC: U.S. Nuclear Regulatory Commission. April 10, 2008.