2191 R0 XI.S6

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XI.S6 STRUCTURES MONITORING

Program Description

Implementation of structures monitoring under Title 10 of the Code of Federal Regulations (10 CFR) 50.65 (the Maintenance Rule) is addressed in the U.S. Nuclear Regulatory Commission (US NRC) Regulatory Guide (RG) 1.160, and Nuclear Management and Resources Council 93-01. These two documents and supplemental guidance herein provide guidance for development of licensee-specific programs to monitor the condition of structures and structural components within the scope of the license renewal rule, such that there is no loss of structure or structural component intended function.

The structures monitoring program consists primarily of periodic visual inspections by personnel qualified to monitor structures and components (SCs) for applicable aging effects from degradation mechanisms, such as those described in the American Concrete Institute (ACI) Standards 349.3R, ACI 201.1R, and Structural Engineering Institute/American Society of Civil Engineers Standard (SEI/ASCE) 11.

Identified aging effects are evaluated by qualified personnel using criteria derived from industry codes and standards contained in the plant current licensing bases, including ACI 349.3R, ACI 318, SEI/ASCE 11, and the American Institute of Steel Construction (AISC) specifications, as applicable.

The program includes preventive actions to ensure structural bolting integrity. The program also includes periodic sampling and testing of groundwater and the need to assess the impact of any changes in its chemistry on below grade concrete structures.

Evaluation and Technical Basis

1. Scope of Program: The scope of the program includes all SCs, component supports, and structural commodities in the scope of license renewal that are not covered by other structural aging management programs (AMPs) (i.e., “ASME Section XI, Subsection IWE” ( Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report AMP XI.S1); “ASME Section XI, Subsection IWL” ( GALL-SLR Report AMP XI.S2); “ASME Section XI, Subsection IWF” ( GALL-SLR Report AMP XI.S3); “Masonry Walls” ( GALL-SLR Report AMP XI.S5); and US NRC RG 1.127, “Inspection of Water-Control Structures Associated with Nuclear Power Plants” ( GALL-SLR Report AMP XI.S7).

Examples of SCs and commodities in the scope of the program are concrete and steel structures, structural bolting, anchor bolts and embedments, component support members, steel edge supports and steel bracings associated with masonry walls, pipe whip restraints and jet impingement shields, transmission towers, panels and other enclosures, racks, sliding surfaces, sump and pool liners, electrical cable trays and conduits, trash racks associated with water control structures, electrical duct banks, manholes, doors, penetration seals, seismic joint filler and other elastomeric materials, and tube tracks.

If protective coatings are relied upon to manage the effects of aging for any structures included in the scope of this program, the program is to address protective coating monitoring and maintenance. Otherwise, coatings on structures within the scope of this program are inspected only as an indication of the condition of the underlying material.

The scope of this program includes periodic sampling and testing of groundwater. The scope may also include inspection of masonry walls and water-control structures provided all the attributes of “Masonry Walls” ( GALL-SLR Report AMP XI.S5) and “Inspection of Water-Control Structures Associated with Nuclear Power Plants” ( GALL-SLR Report AMP XI.S7) are incorporated in the attributes of this program.

2. Preventive Action: The Structures Monitoring program is primarily a condition monitoring program; however, the program includes preventive actions to provide reasonable assurance that structural bolting integrity is maintained, as discussed in Electric Power Research Institute (EPRI) documents (such as EPRI NP-5067(Archived) and TR-104213(Archived)), American Society for Testing and Materials (ASTM) standards, and AISC specifications, as applicable. The preventive actions emphasize proper selection of bolting material and lubricants, and appropriate installation torque or tension to prevent or minimize loss of bolting preload and cracking of high-strength bolting. If the structural bolting consists of ASTM A325 and/or ASTM A490 bolts (including respective equivalent twist-off type ASTM F1852 and/or ASTM F2280 bolts), the preventive actions for storage, lubricant selection, and bolting and coating material selection discussed in Section 2 of Research Council for Structural Connection publication “Specification for Structural Joints Using High-Strength Bolts,” need to be used.

3. Parameters Monitored or Inspected: For each structure/aging effect combination, the specific parameters monitored or inspected depend on the particular SC or commodity. Parameters monitored or inspected are commensurate with industry codes, standards, and guidelines and also consider industry and plant-specific operating experience (OE). ACI 349.3R and SEI/ASCE 11 provide an acceptable basis for selection of parameters to be monitored or inspected for concrete and steel structural elements and for steel liners, joints, coatings, and waterproofing membranes (if applicable).

For concrete structures, parameters monitored include loss of material, cracking, increase in porosity and permeability, loss of strength, and reduction in concrete anchor capacity due to local concrete degradation. Steel SCs are monitored for loss of material due to corrosion. Structural steel bracing and edge supports associated with masonry walls are inspected for deflection or distortion, loose bolts, and loss of material due to corrosion. Painted or coated areas are examined for signs of distress that could indicate degradation of the underlying material.

Bolting within the scope of the program is monitored for loss of material, loose bolts, missing or loose nuts, and other conditions indicative of loss of preload. In addition, concrete around anchor bolts is monitored for degradation.

Accessible sliding surfaces are monitored for indication of significant loss of material due to wear or corrosion, and for accumulation of debris or dirt. Elastomeric vibration isolators, structural sealants, and seismic joint fillers are monitored for cracking, loss of material, and hardening. Groundwater chemistry (pH, chlorides, and sulfates) is monitored periodically to assess its impact, if any, on below-grade concrete structures. If through-wall leakage or groundwater infiltration is identified, leakage volumes and chemistry are monitored and trended for signs of concrete or steel reinforcement degradation.

If necessary for managing settlement and erosion of porous concrete subfoundations, the continued functionality of a site dewatering system is monitored.

4. Detection of Aging Effects: Structures are monitored under this program using periodic visual inspection of each structure/aging effect combination by a qualified inspector to ensure that aging degradation will be detected and quantified before there is loss of intended function. It may be necessary to enhance or supplement visual inspections with nondestructive examination, destructive testing and/or analytical methods, based on the conditions observed or the parameter being monitored. Visual inspection of elastomeric elements is supplemented by tactile inspection to detect hardening if the intended function is suspect.

The inspection frequency depends on safety significance and the condition of the structure as specified in US NRC RG 1.160. In general, all structures are monitored on an interval not to exceed 5 years. The program includes provisions for more frequent inspections based on an evaluation of the observed degradation. The responsible engineer for this program evaluates groundwater chemistry that is sampled from a location that is representative of the groundwater in contact with structures within the scope of subsequent license renewal. This can be done on an interval not to exceed 5 years as long as the evaluation accounts for seasonal variations (e.g., quarterly monitoring every 5th year). Inspector qualifications should be consistent with industry guidelines and standards and guidelines for implementing the requirements of 10 CFR 50.65. Qualifications of inspection and evaluation personnel specified in ACI 349.3R are acceptable for inspection of concrete structures.

Indications of groundwater infiltration or through-concrete leakage are assessed for aging effects. This may include engineering evaluation, more frequent inspections, or destructive testing of affected concrete to validate existing concrete properties, including concrete pH levels. When leakage volumes allow, assessments may include analysis of the leakage pH, along with mineral, chloride, sulfate and iron content in the water.

The structures monitoring program addresses detection of aging affects for inaccessible, below-grade concrete structural elements. For plants with nonaggressive groundwater/soil (pH > 5.5, chlorides < 500 ppm, and sulfates <1,500 ppm), the program recommends: (a) evaluating the acceptability of inaccessible areas when conditions exist in accessible areas that could indicate the presence of, or result in, degradation to such inaccessible areas and (b) examining representative samples of the exposed portions of the below-grade concrete, when excavated for any reason.

For plants with aggressive groundwater/soil (pH < 5.5, chlorides > 500 ppm, or sulfates > 1,500 ppm) and/or where the concrete structural elements have experienced degradation, a plant-specific AMP accounting for the extent of the degradation experienced should be implemented to manage the concrete aging during the subsequent period of extended operation. The plant-specific AMP may include evaluations, destructive testing, and/or focused inspections of representative accessible (leading indicator) or below-grade, inaccessible concrete structural elements exposed to aggressive groundwater/soil, on an interval not to exceed 5 years.

5. Monitoring and Trending: Results of periodic inspections are documented and compared to previous results to identify changes from prior inspections. 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. Quantitative measurements and qualitative information are recorded and trended for findings that exceed the acceptance criteria described in Element 6 for all applicable parameters monitored or inspected. 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.

Quantitative baseline inspection data should be established per the acceptance criteria described herein prior to the subsequent period of extended operation. Previously performed inspections that were conducted using comparable acceptance criteria specified herein are acceptable in lieu of performing a new baseline inspection.

6. Acceptance Criteria: Inspection results are evaluated by qualified engineering personnel based on acceptance criteria selected for each structure/aging effect to ensure that the need for corrective actions is identified before loss of intended functions. The criteria are derived from applicable codes and standards that include but are not limited to ACI 349.3R, ACI 318, SEI/ASCE 11, or the relevant AISC specifications and consider industry and plant OE. The criteria are directed at the identification and evaluation of degradation that may affect the ability of the structure or component to perform its intended function. Justified quantitative acceptance criteria are used whenever applicable. Acceptance criteria for concrete surfaces based on the “second-tier” evaluation criteria provided in Chapter 5 of ACI 349.3R are acceptable. Applicants who elect to use plant-specific criteria for concrete structures should describe the criteria and provide a technical basis for deviations from those in ACI 349.3R. Loose bolts and nuts are not acceptable unless accepted by engineering evaluation. Structural sealants are acceptable if the observed loss of material, cracking, and hardening will not result in loss of sealing. Elastomeric vibration isolation elements are acceptable if there is no loss of material, cracking, or hardening that could lead to the reduction or loss of isolation function. Acceptance criteria for sliding surfaces are (a) no indications of excessive loss of material due to corrosion or wear and (b) no debris or dirt that could restrict or prevent sliding of the surfaces as required by design. The structures monitoring program is to contain sufficient detail on acceptance criteria to conclude that this program attribute is satisfied.

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 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.

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: NUREG–1522 documents the results of a survey sponsored in 1992 by the Office of Nuclear Reactor Regulation to obtain information on the types of distress in the concrete and steel SCs, the type of repairs performed, and the durability of the repairs. Licensees who responded to the survey reported cracking, scaling, and leaching of concrete structures. The degradation was attributed to drying shrinkage, freeze-thaw, and abrasion. The NUREG also describes the results of US NRC staff inspections at six plants. The staff observed concrete degradation, corrosion of component support members and anchor bolts, cracks and other deterioration of masonry walls, and groundwater leakage and seepage into underground structures. Information Notice (IN) 2011-20 discusses an instance of groundwater infiltration leading to alkali-silica reaction degradation in below-grade concrete structures, while IN 2004-05 and IN 2006-13 discusses instances of through-wall water leakage from spent fuel pools. NUREG/CR–7111 provides a summary of aging effects of safety-related concrete structures. Many license renewal applicants have found it necessary to enhance their Structures Monitoring program to ensure that the aging effects of SCs in the scope of 10 CFR Part 54.4 are adequately managed during the subsequent period of extended operation. There is reasonable assurance that implementation of the structures monitoring program described above will be effective in managing the aging of the in-scope SC supports through the period of subsequent license renewal. The program is informed and enhanced when necessary through the systematic and ongoing review of both plant-specific and industry OE 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 50.65, “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.

ACI. ACI Standard 201.1R-08, “Guide for Conducting a Visual Inspection of Concrete in Service.” Farmington Hills, Michigan: American Concrete Institute. 2008.

_____. ACI Standard 318-95, “Building Code Requirements for Reinforced Concrete and Commentary.” Farmington Hills, Michigan: American Concrete Institute. 1995.

_____. ACI Standard 349.3R-02, “Evaluation of Existing Nuclear Safety-Related Concrete Structures.” Farmington Hills, Michigan: American Concrete Institute. 2002.

AISC. “AISC Specification for Steel Buildings.” Chicago, Illinois: American Institute of Steel Construction, Inc. 2005.

ASCE. SEI/ASCE 11-99, “Guideline for Structural Condition Assessment of Existing Buildings.” Reston, Virginia: American Society of Civil Engineers. 2000.

EPRI. EPRI NP-5067(Archived), “Good Bolting Practices, A Reference Manual for Nuclear Power Plant Maintenance Personnel.” Volume 1: Large Bolt Manual, 1987; Volume 2: Small Bolts and Threaded Fasteners. Palo Alto, California: Electric Power Research Institute. 1990.

_____. EPRI TR–104213(Archived), “Bolted Joint Maintenance & Application Guide.” Palo Alto, California: Electric Power Research Institute. December 1995.

NEI. NUMARC 93-01, “Industry Guideline for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants.” Revision 4A. Agencywide Documents Access and Management System (ADAMS) Accession No. ML11116A198. Washington, DC: Nuclear Energy Institute. 2011.

US NRC. Information Notice 2004-05, “Spent Fuel Pool Leakage to Onsite Groundwater.” Washington, DC: U.S. Nuclear Regulatory Commission. March 2004.

_____. Information Notice 2006-13, “Groundwater Contamination due to Undetected Leakage of Radioactive Water.” Washington, DC: U.S. Nuclear Regulatory Commission. July 2006.

_____. Information Notice 2011-20, “Concrete Degradation by Alkali-Silica Reaction.” Washington, DC: U.S. Nuclear Regulatory Commission. November 2011.

_____. NUREG–1522, “Assessment of Inservice Condition of Safety-Related Nuclear Power Plant Structures.” Washington, DC: U.S. Nuclear Regulatory Commission. June 1995.

_____. NUREG/CR–7111, “A Summary of Aging Effects and Their Management in Reactor Spent Fuel Pools, Refueling Cavities, Tori, and Safety-Related Concrete Structures.” ADAMS Accession No. ML12047A184. Washington, DC: U.S. Nuclear Regulatory Commission. January 2012.

_____. Regulatory Guide 1.127, “Inspection of Water-Control Structures Associated With Nuclear Power Plants.” Revision 1. ADAMS Accession No. ML003739392. Washington, DC: U.S. Nuclear Regulatory Commission. 1978.

_____. Regulatory Guide 1.142, “Safety-Related Concrete Structures for Nuclear Power Plants (Other than Reactor Vessels and Containments).” Revision 2. ADAMS Accession No. ML013100274. Washington, DC: U.S. Nuclear Regulatory Commission. 1997.

_____. Regulatory Guide 1.160, “Monitoring the Effectiveness of Maintenance at Nuclear Power Plants.” ADAMS Accession No. ML1136100898. Revision 3. Washington, DC: U.S. Nuclear Regulatory Commission. 2012.

RCSC. “Specification for Structural Joints Using High-Strength Bolts.” Chicago, Illinois. Research Council on Structural Connections. August 2014.

United States of America

Nuclear Regulatory Commission - The US federal government agency that regulates nuclear power plants

American Society of Mechanical Engineers

Electric Power Research Institute

Operating Experience

Quality Assurance

US NRC regulatory guide

Nuclear Energy Institute

Agency wide Documents Access and Management System - The official recordkeeping system, through which the U.S. Nuclear Regulatory Commission (US NRC) provides access to the "libraries" or collections of publicly available documents