XI.S5 (NUREG-2191 R0)
XI.S5 MASONRY WALLS
Program Description
The U.S. Nuclear Regulatory Commission (US NRC) Inspection and Enforcement Bulletin (IEB) 80-11, “Masonry Wall Design,” and US NRC Information Notice (IN) 87-67, “Lessons Learned from Regional Inspections of Licensee Actions in Response to IE Bulletin 80-11,” constitute an acceptable basis for a masonry wall aging management program (AMP). US NRC IEB 80-11 required (a) the identification of masonry walls in close proximity to or having attachments from safety-related systems or components and (b) the evaluation of design adequacy and construction practice. US NRC IN 87-67 recommended plant-specific condition monitoring of masonry walls and administrative controls to ensure that the evaluation basis developed in response to US NRC IEB 80-11 is not invalidated by: (a) deterioration of the masonry walls (e.g., new cracks not considered in the reevaluation), (b) physical plant changes such as installation of new safety related systems or components in close proximity to masonry walls, or (c) reclassification of systems or components from nonsafety-related to safety-related, provided appropriate evaluation is performed to account for such occurrences.
Important elements in the evaluation of many masonry walls during the US NRC IEB 80-11 program included: (a) installation of steel edge supports to provide a sound technical basis for boundary conditions used in seismic analysis and (b) installation of steel bracing to ensure stability or containment of unreinforced masonry walls during a seismic event. Consequently, in addition to the development of cracks in the masonry walls, loss of function of the structural steel supports and bracing would also invalidate the evaluation basis. The steel edge supports and steel bracings are considered component supports and aging effects are managed by the Structures Monitoring program ( Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report AMP XI.S6).
The program consists of periodic visual inspection of masonry walls within the scope of subsequent license renewal (SLR) to detect loss of material and cracking of masonry units and mortar. The aging effects that could impact masonry wall intended function or potentially invalidate its evaluation basis are entered into the corrective action process for further analysis, repair, or replacement.
Since the issuance of US NRC IEB 80-11 and US NRC IN 87-67, the US NRC promulgated Title 10 of the Code of Federal Regulations (10 CFR) 50.65, “Maintenance Rule.” For SLR, masonry walls may be inspected as part of GALL-SLR Report AMP XI.S6 conducted for the Maintenance Rule, provided the 10 attributes described below are incorporated in GALL-SLR Report AMP XI.S6. The aging effects on masonry walls that are considered fire barriers are managed by GALL-SLR Report AMP XI.M26, “Fire Protection.”
Evaluation and Technical Basis
- 1. Scope of Program: The scope includes all masonry walls identified as performing intended functions in accordance with 10 CFR 54.4. Masonry walls consist of solid or hollow concrete block, mortar, grout, steel bracing, reinforcing and supports. The aging effects on masonry walls that are considered fire barriers are also managed by GALL-SLR Report AMP XI.M26, Fire Protection, as well as being managed by this program. Aging effects on the steel elements of masonry walls are managed by GALL-SLR Report AMP XI.S6.
- 2. Preventive Action: This is a condition monitoring program and no specific preventive actions are required.
- 3. Parameters Monitored or Inspected: The primary parameters monitored are potential shrinkage and/or separation, cracking of masonry walls, cracking or loss of material at the mortar joints and gaps between the supports and masonry walls that could impact the intended function or potentially invalidate its evaluation basis.
- 4. Detection of Aging Effects: Visual examination of the masonry walls by qualified inspection personnel is sufficient. In general, masonry walls are inspected every 5 years. Provisions exist for more frequent inspections in areas where significant loss of material, cracking, or other signs of degradation are observed to provide reasonable assurance that there is no loss of intended function between inspections. In addition, masonry walls that are fire barriers are visually inspected in accordance with GALL-SLR Report AMP XI.M26. Steel elements of masonry walls are visually inspected under the scope of GALL-SLR Report AMP XI.S6.
- 5. Monitoring and Trending: Condition monitoring for evidence of shrinkage and/or separation and cracking of masonry is achieved by periodic examination. Where practical, identified degradation is projected until the next scheduled inspection. Results are evaluated against acceptance criteria to confirm that the timing of subsequent inspections will maintain the components’ intended functions throughout the subsequent period of extended operation based on the projected rate of degradation. Inspection results are documented and compared to previous inspections to identify changes or trends in the condition of masonry walls. Crack widths and lengths, and gaps between supports and masonry walls, that approach or exceed acceptance criteria are measured and assessed for trends. Degradation detected from monitoring is evaluated. The use of photographs or surveys is encouraged and photographic records may be used to document and trend the type, severity, extent and progression of degradation.
- 6. Acceptance Criteria: For each masonry wall, observed degradation (e.g., shrinkage and/or separation, cracking of masonry walls, cracking or loss of material at the mortar joints and gaps between the supports and masonry walls) are assessed against the evaluation basis to confirm that the degradation has not invalidated the original evaluation assumptions or impacted the capability to perform the intended functions. Further evaluation is conducted to determine if corrective action is required when the degradation is determined to impact the intended function of the wall or invalidate its evaluation basis. Degraded conditions that exceed acceptance criteria and are accepted without repair or other corrective actions are technically justified or supported by engineering evaluation.
- 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 10 CFR 50, Appendix B. Appendix A of the GALL-SLR Report describes how an applicant may apply its 10 CFR 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.
- If any projected inspection results will not meet acceptance criteria prior to the next scheduled inspection, inspection frequencies are adjusted as determined by the site’s corrective action program.
- A corrective action option is to develop a new analysis or evaluation basis that accounts for the degraded condition of the wall (i.e., acceptance by further evaluation). Other alternatives include repair or replacing the degraded wall.
- 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 50, Appendix B. Appendix A of the GALL-SLR Report describes how an applicant may apply its 10 CFR 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 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 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: Since 1980, masonry walls that perform an intended function have been systematically identified through licensee programs in response to US NRC IEB 80-11, US NRC Generic Letter 87-02, and 10 CFR 50.48. US NRC IN 87-67 documented lessons learned from the US NRC IEB 80-11 program and provided recommendations for administrative controls and periodic inspection to provide reasonable assurance that the evaluation basis for each safety-significant masonry wall is maintained. NUREG–1522 documents instances of observed cracks and other deterioration of masonry-wall joints at nuclear power plants. Whether conducted as a stand-alone program or as a part of structures monitoring, a masonry wall AMP that incorporates the recommendations delineated in US NRC IN 87-67 provides reasonable assurance that the intended functions of all masonry walls within the scope of license renewal are maintained for the subsequent period of extended operation.
- 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.
10 CFR 50.48, “Fire Protection.” Washington, DC: U.S. Nuclear Regulatory Commission. 2016.
10 CFR 50.65, “Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants.” Washington, DC: U.S. Nuclear Regulatory Commission. 2016.
10 CFR 54.4, “Scope.” Washington, DC: U.S. Nuclear Regulatory Commission. 2016.
US NRC. Generic Letter 87-02, “Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors, Unresolved Safety Issue (USI) A-46.” Agencywide Documents Access and Management System (ADAMS) Accession No. ML031150371. Washington, DC: U.S. Nuclear Regulatory Commission. February 1987.
_____. IE Bulletin 80-11, “Masonry Wall Design.” Washington, DC: U.S. Nuclear Regulatory Commission. May 1980.
_____. Information Notice 87-67, “Lessons Learned from Regional Inspections of Licensee Actions in Response to IE Bulletin 80-11.” Washington, DC: U.S. Nuclear Regulatory Commission. December 1987.
_____. NUREG–1522, “Assessment of Inservice Condition of Safety-Related Nuclear Power Plant Structures.” ADAMS Accession No. ML06510407. Washington, DC: U.S. Nuclear Regulatory Commission. June 1995.