2191 R0 XI.E3B

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XI.E3B ELECTRICAL INSULATION FOR INACCESSIBLE INSTRUMENT AND CONTROL CABLES NOT SUBJECT TO 10 CFR 50.49 ENVIRONMENTAL QUALIFICATION REQUIREMENTS

Program Description

The purpose of the aging management program (AMP) is to provide reasonable assurance that the intended functions of inaccessible or underground instrument and control cables that are not subject to the environmental qualification (EQ) requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.49 are maintained consistent with the current licensing basis through the subsequent period of extended operation.

This AMP applies to underground (e.g., installed in buried conduit, embedded raceway, cable trenches, cable troughs, duct banks, vaults, manholes, or direct buried installations) instrumentation and control cables, including those designed for continuous wetting or submergence within the scope of subsequent license renewal (SLR) exposed to significant moisture. Significant moisture is defined as exposure to moisture that lasts more than 3 days that if left unmanaged, could potentially lead to a loss of intended function. Cable wetting or submergence that results from event driven occurrences and is mitigated by either automatic or passive drains is not considered significant moisture for the purposes of this AMP.

When an inaccessible instrument and control cable is exposed to wet, submerged, or other environments for which it was not designed, accelerated age degradation of the electrical insulation may occur. The degradation of the cable shield due to water intrusion may introduce electrical ground issues and noise into the circuit.

The risk contribution due to a failure of an inaccessible instrument and control cable may be limited due to system architecture. However, a common environmental aging stressor, such as submergence, represents an aging mechanism that if not anticipated in the design or mitigated in service, could have an adverse effect on performance of intended functions, or potentially lead to failure of the cable insulation system.

In this AMP, periodic actions are taken to prevent inaccessible instrumentation and control cables from being exposed to significant moisture.

Examples of periodic actions include inspecting for water accumulation in cable manholes, vaults, conduits, and removing water, as needed. Instrumentation and control cables accessible from manholes, vaults, or other underground raceways are visually inspected for cable surface abnormalities. However, these periodic actions may not be sufficient due to the inability to remove accumulated water trapped in the raceways. For example, water accumulation or submergence could occur from: (a) a duct bank conduit with low points in the routing, (b) raceway settling or cracking due to soil settling over a long period of time, (c) manholes and cable trench covers not being watertight, (d) raceway locations subject to a high water table (e.g., high seasonal cycles), and (e) potential wetting or submergence even when duct banks are sloped with the intention to minimize water accumulation.

Therefore, in addition to the above periodic actions, in-scope inaccessible and underground instrumentation and control cables subject to significant moisture are evaluated to determine whether testing is required. If required, initial testing is performed once on a sample population to determine the condition of the electrical insulation. One or more tests may be required due to cable type, application, and electrical insulation to determine the age degradation of the cable.

Inaccessible instrumentation and control cables designed for continuous wetting or submergence are also included in this. The need for additional tests and inspections is determined by the test/inspection results as well as industry and plant-specific operating experience (OE).

Testing of installed inservice inaccessible and underground instrumentation and control cables as part of an existing maintenance, calibration or surveillance program, testing of coupons, abandoned or removed cables, or inaccessible medium- or low-voltage power cables subjected to the same or bounding environment, inservice application, cable routing, construction, manufacturing and insulation material may be credited in lieu of or in combination with testing of installed inservice inaccessible instrumentation and control cables when testing is recommended in this AMP.

As stated in NUREG/CR–5643, “the major concern is that failures of deteriorated cable systems (cables and penetrations) might be induced during accident conditions.” Because the cables are not subject to the EQ requirements of 10 CFR 50.49, an AMP is required to manage the aging effects. This AMP provides reasonable assurance that insulation material for electrical cables will perform its intended function for the subsequent period of extended operation.

Evaluation and Technical Basis

1. Scope of Program: This AMP applies to underground (e.g., installed in buried conduit, embedded raceway, cable trenches, cable troughs, duct banks, vaults, manholes, or direct buried installations) instrumentation and control cables, including those designed for continuous wetting or submergence within the scope of SLR, exposed to significant moisture.

For this AMP, instrumentation cables are cables carrying either analog or digital signals such as coaxial cable, or cable comprised of twisted 16 or 18 American wire gauge (AWG) conductor shielded pairs rated 300V with an overall shield. Examples of control cables included in this AMP are multi-conductor 600V 12 or 14 AWG cables used to monitor or initiate control functions through indication, switches, limit switches, relays, contacts, etc.

Significant moisture is defined as exposure to moisture that lasts more than 3 days that if left unmanaged, could potentially lead to a loss of intended function. Cable wetting or submergence that results from event driven occurrences and is mitigated by either automatic or passive drains is not considered significant moisture for the purposes of this AMP.

In-scope inaccessible and underground instrumentation and control cable splices subjected to wetting or submergence are included within the scope of this program. Cables designed for continuous wetting or submergence also are included in this AMP. Additional tests and periodic visual inspections are determined by the test/inspection results and industry and plant-specific aging degradation OE with the applicable cable electrical insulation.

2. Preventive Actions: This is a condition monitoring program. However, periodic actions are taken to prevent inaccessible and underground instrumentation and control cables from being exposed to significant moisture, such as identifying and inspecting in-scope accessible cable conduit ends and cable manholes/vaults for water accumulation, and removing the water, as needed.

The inspection frequency for water accumulation in manholes/vaults is established and performed based on plant-specific OE with cable wetting or submergence. The inspections are performed periodically based on water accumulation over time. The periodic inspection occurs at least once annually with the first inspection for SLR completed prior to the subsequent period of extended operation. The annual inspection frequency is consistent with US NRC Inspection Manual, Attachment 71111.06, “Flood Protection Measures.”

Inspections for water accumulation are also performed after event-driven occurrences, such as heavy rain, rapid thawing of ice and snow, or flooding. Plant-specific parameters are established for the initiation of an event-driven inspection. Inspections include direct indication that cables are not submerged, and that cable/splices and cable support structures are intact. Dewatering systems (e.g., sump pumps and passive drains) and associated alarms are inspected and their operation verified periodically. The periodic inspection includes documentation that either automatic or passive drainage systems, or manual pumping of manholes or vaults is effective in preventing inaccessible cable exposure to significant moisture.

The aging management of the physical structure, including cable support structures and cable vaults or manholes, is managed by Generic Aging Lessons Learned Subsequent License Renewal (GALL-SLR) Report AMP XI.S6, “Structures Monitoring.”

3. Parameters Monitored or Inspected: Inspection for water accumulation in manholes/vaults is performed periodically based on plant-specific OE with water accumulation over time.

Inaccessible and underground instrumentation and control cables within the scope of SLR are periodically visually inspected to assess age degradation of the electrical insulation. Inaccessible and underground instrumentation and control cables found to be exposed to significant moisture are evaluated (e.g., a determination is made as to whether a periodic or one-time test is needed for condition monitoring of the cable insulation system). Cable installation systems that are known or subsequently found through either industry or plant-specific OE to degrade with continuous exposure to significant moisture (e.g., Vulkene and Raychem cross-linked polyethylene) are also tested to monitor cable electrical insulation degradation over time. The specific type of test(s) should be a proven technique capable of detecting reduced insulation resistance or degraded dielectric strength of the cable insulation system due to wetting or submergence.

Visual inspection of inaccessible and underground instrumentation and control cables also includes a determination as to whether other adverse environments exist. Cables subjected to these adverse environments are also evaluated for significant aging degradation of the cable insulation system.

4. Detection of Aging Effects: For inaccessible instrumentation and control cables exposed to significant moisture, visual inspection frequency is adjusted based on inspection and test results as well as plant-specific and industry OE. For inaccessible and underground instrumentation and control cables exposed to significant moisture where testing is required, a one-time test is performed. Visual inspection occurs at least once every 6 years and may be coordinated with the periodic inspection for water accumulation. This is an adequate period to monitor performance of instrumentation and control cables and take appropriate corrective actions since industry OE has shown that although a slow process, age degradation could be significant. Required testing and the initial visual inspection for SLR are to be completed prior to the subsequent period of extended operation.

Cables are periodically visually inspected for cable jacket surface abnormalities, such as: embrittlement, discoloration, cracking, melting, swelling, or surface contamination due to the aging mechanism and effects of significant moisture. The cable insulation visual inspection portion of the AMP uses the cable jacket material as representative of the aging effects experienced by the instrumentation and control cable electrical insulation. Age degradation of the cable jacket may indicate accelerated age degradation of the electrical insulation due to significant moisture or other aging mechanisms.

The specific type of test(s) determines, with reasonable assurance, in-scope inaccessible instrumentation, and control cable insulation age degradation. One or more tests may be required based on cable application, and electrical insulation material to determine the age degradation of the cable insulation.

Testing of installed inservice inaccessible instrumentation and control cables as part of an existing maintenance, calibration or surveillance program, testing of coupons, abandoned or removed cables, or inaccessible medium- or low-voltage power cables subjected to the same or bounding environment, inservice application, cable routing, manufacturing and insulation material may be credited in lieu of or in combination with testing of installed inservice inaccessible instrumentation and control cables when testing is required in this AMP.

The cable testing portion of the AMP utilizes sampling. The following factors are considered in the development of the electrical insulation sample: temperature, voltage, cable type, and construction including the electrical insulation composition. A sample of 20 percent with a maximum sample of 25 constitutes a representative cable sample size. The basis for the methodology and sample used is documented. If an unacceptable condition or situation is identified in the selected sample, a determination is made as to whether the same condition or situation is applicable to other inaccessible instrumentation and control cables not tested and whether the tested sample population should be expanded. The applicant’s corrective action program is used to evaluate test or visual inspection results that did not meet acceptance criteria and determine appropriate corrective action (e.g., additional visual inspections or testing).

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. However, condition monitoring cable tests and inspection results that utilize the same visual or test methods that are trendable and repeatable provide additional information on the rate of cable insulation degradation.

6. Acceptance Criteria: An unacceptable indication is defined as a noted condition or situation that, if left unmanaged, could potentially lead to a loss of intended function.

The acceptance criteria for each test or inspection are determined by the specific type of test performed and the specific cable tested. Acceptance criteria for water accumulation inspections are defined by the direct indication that cable support structures are intact and cables are not subject to significant moisture. Dewatering systems (e.g., sump pumps and drains) and associated alarms are inspected and their operation verified.

Visual inspection results show that instrumentation and control cable jacket material are free from unacceptable surface abnormalities that indicate excessive cable insulation aging degradation.

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.

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: 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.

EPRI. EPRI TR–109619, “Guideline for the Management of Adverse Localized Equipment Environments.” Palo Alto, California: Electric Power Research Institute. June 1999.

IEEE. IEEE Standard 1205-2014, “IEEE Guide for Assessing, Monitoring, and Mitigating Aging Effects on Electrical Equipment Used in Nuclear Power Generating Stations and Other Nuclear Facilities.” New York, New York: Institute of Electrical and Electronics Engineers. 2014.

US NRC. Generic Letter 2007-01, “Inaccessible or Underground Power Cable Failures that Disable Accident Mitigation Systems or Cause Plant Transients.” Agencywide Documents Access and Management System (ADAMS) Accession No. ML070360665. Washington, DC: U.S. Nuclear Regulatory Commission. February 7, 2007.

_____. Information Notice 1986-49, “Age/Environment Induces Electrical Cable Failures.” ADAMS Accession No. ML031220698. Washington, DC: U.S. Nuclear Regulatory Commission. June 16, 1986.

_____. Information Notice 2002-12, “Submerged Safety-Related Electrical Cables.” ADAMS Accession No. ML020790238. Washington, DC: U.S. Nuclear Regulatory Commission. March 31, 2002.

_____. Information Notice 2010-26, “Submerged Electrical Cables.” ADAMS Accession No. ML102800456. Washington, DC: U.S. Nuclear Regulatory Commission. December 2, 2010.

_____. Inspection Manual, Attachment 71111.01, “Adverse Weather Protection.” ADAMS Accession No. ML14334A684. Washington, DC: U.S. Nuclear Regulatory Commission. January 1, 2016.

_____. [Inspection Manual, Attachment 71111.06, “Flood Protection Measures.” ADAMS Accession No. ML15140A133. Washington, DC: U.S. Nuclear Regulatory Commission. January 1, 2016.

_____. NUREG/CR–7000, “Essential Elements of an Electric Cable Condition Monitoring Program.” ADAMS Accession No. ML100540050. Washington, DC: U.S. Nuclear Regulatory Commission. January 31, 2010.

_____. Regulatory Guide 1.211, “Qualification of Safety-Related Cables and Field Splices for Nuclear Power Plants.” Revision 0. ADAMS Accession No. ML082530205. Washington, DC: U.S. Nuclear Regulatory Commission. April 1, 2009.

_____. Regulatory Guide 1.218, “Condition Monitoring Techniques for Electric Cables Used in Nuclear Power Plants.” Revision 0. ADAMS Accession No. ML1035310458. Washington, DC: U.S. Nuclear Regulatory Commission. April 30, 2012.

Aging Management Program

Environmental Qualification - A process for ensuring that equipment will be capable of withstanding the ambient conditions that could exist when the specific function to be performed by the equipment is actually called upon to be performed under accident conditions.

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.

Operating Experience

US NRC regulatory guide

United States of America

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

Quality Assurance

Electric Power Research 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