2191 R0 XI.M36

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XI.M36 EXTERNAL SURFACES MONITORING OF MECHANICAL COMPONENTS

Program Description

The External Surfaces Monitoring of Mechanical Components program is based on system inspections and walkdowns. This program consists of periodic visual inspections of metallic, polymeric, and cementitious components, such as piping, piping components, ducting, ducting components; heating, ventilation, and air conditioning (HVAC) closure bolting; heat exchanger components, and seals. The program manages aging effects through visual inspection of external surfaces for evidence of loss of material, cracking, hardening or loss of strength, reduced thermal insulation resistance, loss of preload for HVAC closure bolting, and reduction of heat transfer due to fouling. When appropriate for the component and material (e.g., elastomers, flexible polymers, polyvinyl chloride), physical manipulation is used to augment visual inspection to confirm the absence of hardening or loss of strength, or reduction in impact strength. This program may also be used to manage cracking due to stress corrosion cracking (SCC) in aluminum and stainless steel (SS) components exposed to aqueous solutions and air environments containing halides.

Reduced thermal insulation resistance due to moisture intrusion, associated with insulation that is jacketed, is managed by visual inspection of the condition of the jacketing when the insulation has an intended function to reduce heat transfer from the insulated components. Outdoor insulated components, and indoor components exposed to condensation, have portions of the insulation inspected or removed, when applicable, to determine whether the exterior surface of the component is degrading or has the potential to degrade. Loss of material due to boric acid corrosion is managed by the Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report aging management program (AMP) XI.M10, “Boric Acid Corrosion.”

Evaluation and Technical Basis

1. Scope of Program: This program visually inspects the external surfaces of mechanical components. The program also inspects heat exchanger surfaces exposed to air for evidence of reduction of heat transfer due to fouling.

For situations where the similarity of the internal and external environments are such that the external surface condition is representative of the internal surface condition, external inspections of components may be credited for managing: (a) loss of material and cracking of internal surfaces for metallic and cementitious components, (b) loss of material, and cracking of internal surfaces for polymeric components, and (c) hardening or loss of strength of internal surfaces for elastomeric components. When credited, the program provides the basis to establish that the external and internal surface condition and environment are sufficiently similar.

Aging effects associated with underground piping and tanks that are below grade but are contained within a tunnel or vault such that they are in contact with air and are located where access for inspection is restricted, are managed by GALL-SLR Report AMP XI.M41, “Buried and Underground Piping and Tanks.” Aging effects associated with below grade components that are accessible during normal operations or refueling outages for which access is not restricted are managed by this program.

2. Preventive Actions: Depending on the material, components may be coated to mitigate corrosion by protecting the external surface of the component from environmental exposure. Inspections to verify the integrity of the insulation jacketing can limit or prevent water in-leakage in the insulation.

3. Parameters Monitored or Inspected: This program uses periodic plant system inspections and walkdowns to monitor for material degradation, accumulation of debris, and leakage. This program inspects components such as piping, piping components, ducting, seals, insulation jacketing, and air-side heat exchangers. For metallic components, coatings deterioration is an indicator of possible underlying degradation. Cementitious components are visually inspected for indications loss of material and cracking. Periodic visual or surface examinations are conducted if this program is being used to manage cracking in SS or aluminum components.

Examples of inspection parameters for metallic components include:

• Corrosion and surface imperfections (loss of material or cracking)
• Loss of wall thickness (loss of material)
• Flaking or oxide-coated surfaces (loss of material)
• Corrosion stains on thermal insulation (loss of material)
• Cracking, flaking, or blistering of protective coating (loss of coating integrity)
• Leakage for detection of cracks on the surfaces of SS and aluminum components exposed to air and aqueous solutions containing halides (cracking)
• Accumulation of debris on heat exchanger tube surfaces (reduction of heat transfer)

The aging effects for elastomeric and flexible polymeric components are monitored through a combination of visual inspection and manual or physical manipulation of the material. Manual or physical manipulation of the material includes touching, pressing on, flexing, bending, or otherwise manually interacting with the material. The purpose of the manual manipulation is to reveal changes in material properties, such as hardness, and to make the visual examination process more effective in identifying aging effects such as cracking. Flexing of polyvinyl chloride piping exposed directly to sunlight (i.e., not located in a structure restricting access to sunlight such as manholes, enclosures, and vaults or isolated from the environment by coatings) is conducted to detect potential reduction in impact strength as indicated by a crackling sound or surface cracks when flexed.

Examples of inspection parameters for elastomers and polymers include:

• Surface cracking, crazing, scuffing, and dimensional change (e.g., “ballooning” and “necking”)
• Loss of thickness
• Discoloration (evidence of a potential change in material properties that could be indicative of polymeric degradation)
• Exposure of internal reinforcement for reinforced elastomers
• Hardening as evidenced by a loss of suppleness during manipulation where the component and material are appropriate to manipulation

Examples of inspection parameters for cementitious materials include:

• Spalling
• Scaling
• Cracking

4. Detection of Aging Effects: This program manages the aging effects of loss of material, cracking, hardening or loss of strength, reduced thermal insulation resistance, loss of preload for HVAC closure bolting, and reduction of heat transfer due to fouling using visual inspections. In addition, physical manipulation is used to manage hardening or loss of strength and reduction in impact strength. For coated surfaces, confirmation of the integrity of the coating is an effective method for managing the effects of corrosion on the metallic surface.

Inspections are performed by personnel qualified in accordance with site procedures and programs to perform the specified task. When required by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), inspections are conducted in accordance with the applicable code requirements. Non-ASME Code inspections and tests follow site procedures that include inspection parameters for items such as lighting, distance, offset, surface coverage, and presence of protective coatings. The inspections are capable of detecting age-related degradation and, with the exception of examinations to detect cracking in SS or aluminum components, are performed at a frequency not to exceed one refueling cycle. This frequency accommodates inspections of components that may be in locations normally accessible only during outages (e.g., high dose areas). Surfaces that are not readily visible during plant operations and refueling outages are inspected when they are made accessible and at such intervals that would ensure the components’ intended functions are maintained.

Periodic visual inspections or surface examinations are conducted on SS and aluminum components to manage cracking every 10 years during the subsequent period of extended operation when applicable (e.g., see Standard Review Plan for Review of Subsequent License Renewal Applications for Nuclear Power Plants (SRP-SLR) Sections 3.2.2.2.4 and 3.2.2.2.8). One or more of the following three options may be used to implement the periodic visual inspections or surface examinations:

• Surface examination conducted in accordance with plant-specific procedures.
• ASME Code Section XI VT-1 inspections (including those inspections conducted on non-ASME Code components).
• Visual inspections may be conducted where it has been analytically demonstrated that surface cracks can be detected by leakage prior to a crack challenging the structural integrity or intended function of the component. The subsequent license renewal application (SLRA) includes an overview of the analytical method, input variables, assumptions, basis for use of bounding analyses, and results.

When using this option, cracks can be detected in gas-filled systems by methods such as, but not limited to: (a) for diesel exhaust piping, detecting staining on external surfaces of components; (b) for accumulators and piping connecting the accumulators to components, monitoring and trending accumulator pressures or refill frequency; and (c) soap bubble testing when systems are pressurized. The SLRA includes the specific methods used.

Surface examinations or VT-1 examinations are conducted on 20 percent of the surface area unless the component is measured in linear feet, such as piping. Alternatively, any combination of 1-foot length sections and components can be used to meet the recommended extent of 25 inspections. The provisions of GALL-SLR Report AMP XI.M38 to conduct inspections in a more severe environment and combination of air environments may be incorporated for these inspections.

In some instances, thermal insulation (e.g., calcium silicate) has been included in-scope to reduce heat transfer from components because absent the insulation, the thermal effects could affect a function described in Title 10 of the Code of Federal Regulations (10 CFR) 54.4(a). When metallic jacketing has been used, it is acceptable to conduct external visual inspections of the jacketing in order to detect damage to the jacketing that would permit in leakage of moisture as long as the jacketing has been installed in accordance with plant-specific procedures that include configuration features such as minimum overlap, location of seams, etc. If plant-specific procedures do not include these features, an alternative inspection methodology should be proposed.

Component surfaces that are insulated and exposed to condensation (because the in-scope component is operated below the dew point), and insulated outdoor components, (aging effects associated with corrosion under insulation for outdoor tanks may be managed by this AMP or GALL-SLR Report AMP XI.M29, “Outdoor and Large Atmospheric Metallic Storage Tanks”) are periodically inspected every 10 years during the subsequent period of extended operation. For all outdoor components and any indoor components exposed to condensation (because the in-scope component is operated below the dew point), inspections are conducted of each material type (e.g., steel, SS, copper alloy, aluminum) and environment (e.g., air outdoor, air accompanied by leakage) where condensation or moisture on the surfaces of the component could occur routinely or seasonally. In some instances, significant moisture can accumulate under insulation during high humidity seasons, even in conditioned air. A minimum of 20 percent of the in-scope piping length, or 20 percent of the surface area for components whose configuration does not conform to a 1-foot axial length determination (e.g., valve, accumulator, tank) is inspected after the insulation is removed. Alternatively, any combination of a minimum of twenty-five 1-foot axial length sections and components for each material type is inspected. Inspection locations should focus on the bounding or lead components most susceptible to aging because of time in service, severity of operating conditions (e.g., amount of time that condensate would be present on the external surfaces of the component), and lowest design margin. Inspections for cracking due to SCC in aluminum components need not be conducted if it has been determined that SCC is not an applicable aging effect, see SRP-SLR Sections 3.2.2.2.8, 3.3.2.2.8, or 3.4.2.2.7. The following are alternatives to removing insulation after the initial inspection:

1. Subsequent inspections may consist of examination of the exterior surface of the insulation with sufficient acuity to detect indications of damage to the jacketing or protective outer layer (if the protective outer layer is waterproof) of the insulation when the results of the initial inspections meet the following criteria:
   1. No loss of material due to general, pitting, or crevice corrosion beyond that which could have been present during initial construction is observed during the first set of inspections, and
   2. No evidence of SCC is observed during the first set of inspections.
   If: (a) the external visual inspections of the insulation reveal damage to the exterior surface of the insulation or jacketing, (b) there is evidence of water intrusion through the insulation (e.g., water seepage through insulation seams/joints), or (c) the protective outer layer (where jacketing is not installed) is not waterproof, periodic inspections under the insulation should continue as conducted for the initial inspection.
2. Removal of tightly adhering insulation that is impermeable to moisture is not required unless there is evidence of damage to the moisture barrier. If the moisture barrier is intact, the likelihood of corrosion under insulation is low for tightly adhering insulation. Tightly adhering insulation is considered to be a separate population from the remainder of insulation installed on in-scope components. The entire population of in-scope piping that has tightly adhering insulation is visually inspected for damage to the moisture barrier with the same frequency as for other types of insulation inspections. These inspections are not credited towards the inspection quantities for other types of insulation.

Visual inspection will identify indirect indicators of elastomer and flexible polymer hardening or loss of strength, including the presence of surface cracking, crazing, discoloration, and, for elastomers with internal reinforcement, the exposure of reinforcing fibers, mesh, or underlying metal. Visual inspections cover 100 percent of accessible component surfaces. Visual inspection will identify direct indicators of loss of material due to wear to include dimension change, scuffing, and, for flexible polymeric materials with internal reinforcement, the exposure of reinforcing fibers, mesh, or underlying metal. Manual or physical manipulation can be used to augment visual inspection to confirm the absence of hardening or loss of strength for elastomers and flexible polymeric materials (e.g., heating, ventilation, and air conditioning flexible connectors) where appropriate. The sample size for manipulation is at least 10 percent of available surface area.

5. Monitoring and Trending: 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. For sampling-based inspections, results are evaluated against acceptance criteria to confirm that the sampling bases (e.g., selection, size, frequency) will maintain the components’ intended functions throughout the subsequent period of extended operation based on the projected rate and extent of degradation.

6. Acceptance Criteria: For each component and aging effect combination, the acceptance criteria are defined to ensure that the need for corrective actions will be identified before loss of intended functions. Acceptance criteria are developed from plant-specific design standards and procedural requirements, current licensing basis (CLB), industry codes or standards (e.g., ASME Code Section III, ANSI/ASME B31.1), and engineering evaluation. Acceptance criteria, which permit degradation, are based on maintaining the intended function(s) under all CLB design loads. The evaluation projects the degree of observed degradation to the end of the subsequent period of extended operation or the next scheduled inspection, whichever is shorter. Where practical, acceptance criteria are quantitative (e.g., minimum wall thickness, percent shrinkage allowed in an elastomeric seal). Where qualitative acceptance criteria are used, the criteria are clear enough to reasonably ensure that a singular decision is derived based on the observed condition of the systems, structures, and components. For example, cracks are absent in rigid polymers, the flexibility of an elastomeric sealant is sufficient to ensure that it will properly adhere to surfaces. Electric Power Research Institute technical reports 1007933, “Aging Assessment Field Guide,” and 1009743, “Aging Identification and Assessment Checklist,” provide general guidance for evaluation of materials and criteria for their acceptance when performing visual/tactile inspections.

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.

For the sampling-based inspections to detect cracking in aluminum and stainless steel components, additional inspections are conducted if one of the inspections does not meet acceptance criteria due to current or projected degradation (i.e., trending) unless the cause of the aging effect for each applicable material and environment is corrected by repair or replacement for all components constructed of the same material and exposed to the same environment. The number of increased inspections is determined in accordance with the site’s corrective action process; however, there are no fewer than five additional inspections for each inspection that did not meet acceptance criteria, or 20 percent of each applicable material, environment, and aging effect combination is inspected, whichever is less. The additional inspections are completed within the interval (i.e., 10-year inspection interval) in which the original inspection was conducted. If subsequent inspections do not meet acceptance criteria, an extent of condition and extent of cause analysis is conducted to determine the further extent of inspections. Additional samples are inspected for any recurring degradation to ensure corrective actions appropriately address the associated causes. At multi-unit sites, the additional inspections include inspections at all of the units with the same material, environment, and aging effect combination.

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: External surface inspections through system inspections and walkdowns have been in effect at many utilities since the mid-1990s in support of the Maintenance Rule (10 CFR 50.65) and have proven effective in maintaining the material condition of plant systems. The elements that comprise these inspections (e.g., the scope of the inspections and inspection techniques) are consistent with industry practice.

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 50.65, “Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants.” Washington, DC: U.S. Nuclear Regulatory Commission. 2016.

10 CFR 54.4(a), “Scope.” Washington, DC: U.S. Nuclear Regulatory Commission. 2016.

EPRI. Technical Report 1009743, “Aging Identification and Assessment Checklist.” Palo Alto, California: Electric Power Research Institute. August 2004.

_____. Technical Report 1007933, “Aging Assessment Field Guide.” Palo Alto, California: Electric Power Research Institute. December 2003.

INPO. Good Practice TS-413, “Use of System Engineers.” INPO 85-033. Washington, DC: Institute of Nuclear Power Operations. May 1988.

Stress Corrosion Cracking

American Society of Mechanical Engineers

Subsequent License Renewal - The extension of the original license from 40 years to 60 years is known as License Renewal. Extensions of the license beyond 60 years are known as Subsequent License Renewal.

Subsequent License Renewal Application - The document submitted by the plant licensee under 10 CFR 54 to extend the operating license of the plant beyond 60 years in 20 year increments. 10 CR 54 has no limits on the number of license extensions that can be approved for a plant.

Current Licensing Basis - 10 CFR 54.3 under references

Quality Assurance

Electric Power Research Institute

Institute of Nuclear Power Operations