2191 R0 XI.S7

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XI.S7 INSPECTION OF WATER-CONTROL STRUCTURES ASSOCIATED WITH NUCLEAR POWER PLANTS

Program Description

This program describes an acceptable basis for developing an inservice inspection (ISI) and surveillance program for dams, slopes, canals, and other raw water-control structures associated with emergency cooling water systems or flood protection of nuclear power plants (NPPs). The program addresses age-related deterioration, degradation due to environmental conditions, and the effects of natural phenomena that may affect water-control structures. The program recognizes the importance of periodic monitoring and maintenance of water-control structures so that the consequences of age-related deterioration and degradation can be prevented or mitigated in a timely manner.

The U.S. Nuclear Regulatory Commission (US NRC) Regulatory Guide (RG) 1.127, Revision 1, "Inspection of Water-Control Structures Associated with Nuclear Power Plants," provides additional detailed guidance for an inspection program for water-control structures, including guidance on engineering data compilation, inspection activities, technical evaluation, inspection frequency, and the content of inspection reports. US NRC RG 1.127 delineates current US NRC practice in evaluating ISI programs for water-control structures.

An aging management program (AMP) addressing water-control structures, commensurate with the program elements described below, is expected regardless of whether a plant is committed to US NRC RG 1.127. Aging management of water-control structures and components (SCs) may be included in “Structures Monitoring” ( Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report AMP XI.S6); however, details pertaining to water-control structures, as described herein, should be explicitly incorporated and identified in GALL-SLR Report AMP XI.S6 program attributes if this approach is taken.

Attributes evaluated below do not include inspection of dams. For dam inspection and maintenance, programs under the regulatory jurisdiction of the Federal Energy Regulatory Commission (FERC) or the U.S. Army Corps of Engineers (USACE), continued through the subsequent period of extended operation, are adequate for the purpose of aging management. For programs not falling under the regulatory jurisdiction of FERC or the USACE the staff evaluates the effectiveness of the AMP based on compatibility to the common practices of the FERC and USACE programs.

Evaluation and Technical Basis

1. Scope of Program: The scope includes raw water-control structures associated with emergency cooling water systems or flood protection of NPPs. The water-control structures included in the program are concrete structures, embankment structures, spillway structures and outlet works, reservoirs, cooling water channels and canals, flood protection walls and gates, and intake and discharge structures. The scope of the program also includes structural steel, and structural bolting associated with water-control structures, steel or wood piles and sheeting required for the stability of embankments and channel slopes, and miscellaneous steel, such as sluice gates and trash racks.

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.

2. Preventive Action: This is a Condition Monitoring program. The program is augmented to include preventive actions to provide reasonable assurance that structural bolting integrity, 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 American Institute of Steel Construction (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 Connections (publication “Specification for Structural Joints Using High-Strength Bolts” need to be used).

3. Parameters Monitored or Inspected: US NRC RG 1.127 identifies parameters to be monitored and inspected for water-control structures.

Parameters to be monitored and inspected for concrete structures are those described in American Concrete Institute (ACI) 201.1R and ACI 349.3R. These include cracking, movements (e.g., settlement, heaving, and deflection), conditions at junctions with abutments and embankments, loss of material, increase in porosity and permeability, seepage, and leakage.

Parameters to be monitored and inspected for earthen embankment structures include settlement, depressions, sink holes, slope stability (e.g., irregularities in alignment and variances from originally constructed slopes), seepage, proper functioning of drainage systems, and degradation of slope protection features. Parameters monitored for channels and canals include erosion or degradation that may impose constraints on the function of the cooling system and present a potential hazard to the safety of the plant. Submerged emergency canals (e.g., artificially dredged canals at the river bed or the bottom of the reservoir) are monitored for sedimentation, debris, or instability of slopes that may impair the function of the canals under extreme low flow conditions.

Further details of parameters to be monitored and inspected for these and other water-control structures are specified in Section C of US NRC RG 1.127.

Steel components are monitored for 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 cracking.

Accessible sliding surfaces are monitored for indication of loss of material due to wear or corrosion, and accumulation of debris or dirt.

Wooden components are monitored for loss of material and change in material properties.

4. Detection of Aging Effects: Inspection of water-control structures is conducted under the direction of qualified engineers experienced in the investigation, design, construction, and operation of these types of facilities. Qualifications of inspection and evaluation personnel specified in ACI 349.3R are acceptable for reinforced concrete water control structures. Visual inspections are primarily used to detect degradation of water-control structures. In some cases, instruments have been installed to measure the behavior of water-control structures. Available records and readings of installed instruments are to be reviewed to detect any unusual performance or distress that may be indicative of degradation. Periodic inspections are to be performed at least once every 5 years. This interval has been shown to be adequate to detect degradation of water-control structures before a loss of an intended function. The program includes provisions for increased inspection frequency based on an evaluation of the observed degradation. The program also includes provisions for special inspections immediately following the occurrence of significant natural phenomena, such as large floods, earthquakes, hurricanes, tornadoes, or intense local rainfalls. The responsible engineer for this program evaluates raw water and groundwater chemistry that is sampled from a location that is representative of the water 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).

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 program addresses detection of aging affects for inaccessible, below-grade, and submerged concrete structural elements. For plants with nonaggressive raw water and groundwater/soil [pH > 5.5, chlorides < 500 parts per million (ppm), and sulfates < 1,500 ppm], the program includes (a) evaluation of 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) examination of representative samples of the exposed portions of the below-grade concrete when excavated for any reason. Submerged concrete structures may be inspected during periods of low tide or when dewatered. Plant-specific justification is provided in the subsequent license renewal application for the acceptability of submerged concrete if inspections do not occur within the 5 year interval. Areas covered by silt, vegetation, or marine growth are not considered inaccessible and are cleaned and inspected in accordance with the standard inspection frequency.

For plants with aggressive raw water (pH < 5.5, chlorides > 500 ppm, or sulfates > 1,500 ppm) or groundwater/soil and/or where the structural elements have experienced degradation, a plant-specific AMP accounting for the extent of the degradation experienced is implemented to manage aging during the subsequent period of extended operation. The plant-specific AMP may include evaluations, destructive testing, and/or focused inspections of accessible (leading indicator) or below-grade, inaccessible structural elements exposed to aggressive raw water or groundwater/soil on an interval not to exceed 5 years, and submerged structural elements are visually inspected (e.g., dewatering, divers) at least once every 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 exceeding 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: The quantitative “second-tier” evaluation criteria provided in Chapter 5 of ACI 349.3R are acceptable for concrete. 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. Acceptance criteria for earthen structures, such as canals and embankments, are consistent with programs falling within the regulatory jurisdiction of the FERC or the USACE. Loose bolts and nuts, and degradation of piles and sheeting are accepted by engineering evaluation or subject to corrective actions. Engineering evaluation is documented and based on codes, specifications, and standards such as AISC specifications, Structural Engineering Institute/American Society of Civil Engineers Standard 11-99, “Guideline for Structural Condition Assessment of Existing Buildings,” and those referenced in the plant’s current licensing basis.

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.

When inspection findings indicate that significant changes have occurred, the conditions are to be evaluated. This includes a technical assessment of the causes of distress or abnormal conditions, an evaluation of the behavior or movement of the structure, and recommendations for remedial or mitigating measures. 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: Degradation of water-control structures has been detected, through US NRC RG 1.127 programs, at a number of nuclear power plants, and, in some cases, it has required remedial action. US NRC NUREG–1522, “Assessment of Inservice Conditions of Safety-Related Nuclear Plant Structures” described instances and corrective actions of severely degraded steel and concrete components at the intake structure and pump house of coastal plants. Other degradation described in the NUREG include appreciable leakage from the spillway gates, concrete cracking, corrosion of spillway bridge beam seats of a plant dam and cooling canal, and appreciable differential settlement of the outfall structure of another. No loss of intended functions has resulted from these occurrences. Therefore, it can be concluded that the inspections implemented in accordance with the guidance in US NRC RG 1.127 have been successful in detecting significant degradation before loss of intended function occurs.

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.

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 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. 2010.

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.

US NRC. NUREG–1522, “Assessment of Inservice Conditions of Safety-Related Nuclear Plant Structures.” Agencywide Documents Access and Management System (ADAMS) Accession No. ML06510407. Washington, DC: U.S. Nuclear Regulatory Commission. June 1995.

_____. 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 1.160, “Monitoring the Effectiveness of Maintenance at Nuclear Power Plants.” ADAMS Accession No. ML12216A016. Washington, DC: U.S. Nuclear Regulatory Commission. 1993.

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

Aging Management Program

Electric Power Research Institute

Quality Assurance

US NRC regulatory guide

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