ML22333A740

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NRC Presentation - ASME OM Code and Snubber Issues at Inservice Service Testing Owner Group (Istog) Final - Meeting December 5-6, 2022, in Clearwater, Fl
ML22333A740
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Issue date: 12/05/2022
From: Gurjendra Bedi
Office of Nuclear Reactor Regulation
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Download: ML22333A740 (28)
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ASME OM Code and Snubber Inservice Testing Program Inservice Testing Owners Group Meeting December 5-6, 2022 Gurjendra S. Bedi, PE Mechanical Engineering and Inservice Testing Branch Division of Engineering and External Hazards Office of Nuclear Reactor Regulation

Disclaimer

  • This presentation was prepared by staff of the U.S. Nuclear Regulatory Commission (NRC). It may present information that does not currently represent an agreed upon NRC staff position. NRC has neither approved nor disapproved the technical content.

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Topics for Discussion

  • Inservice Examination and Testing of Snubbers
  • ASME Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code:

Section IST (OM Code)

  • Snubber Program and Submittal Requirements
  • Service Life Monitoring
  • Use of Code Case OMN-13 and records of all the visual examination failures during this extended 10-year interval.

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Inservice Examination and Testing of Snubbers ASME BPV Code vs ASME OM Code

Background

  • ASME BPV Code,Section XI, 2005 Addenda and earlier editions and addenda, contained the snubber inservice examination and testing requirements.
  • ASME BPV Code,Section XI, 2006 Addenda through latest edition, do not contain the snubber inservice examination and testing requirements.
  • ASME OM Code, 1995 Edition through the latest edition, contain the snubber inservice examination and testing requirements.

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Inservice Examination and Testing of Snubbers ASME BPV Code vs ASME OM Code (cont.)

ASME BPV Code,Section XI, 2006 Addenda and later Editions, Figure 1300-1(f) - Boundary between Snubber (pin-to-pin) and support structure 5

Inservice Examination and Testing of Snubbers ASME BPV Code vs ASME OM Code (cont.)

Regulation

  • 10 CFR 50.55a(b)(3)(v)(B), Snubbers, Second provision, states, in part, that licensees must comply with the provisions for examining and testing snubbers in Subsection ISTD of the ASME OM Code when using the 2006 Addenda and later editions of Section XI of the ASME BPV Code.

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Inservice Examination and Testing of Snubbers ASME BPV Code vs ASME OM Code (cont.)

NRC Recommendation

  • If a plants Code of Record for inservice inspection (ISI) interval is ASME BPV Code,Section XI, 2006 Addenda or later, the licensee must use the applicable edition of the ASME OM Code for developing its snubber program.
  • Snubber program should be updated and aligned with the plants 10-year ISI or inservice testing (IST) program interval.
  • NUREG-1482, Guidelines for Inservice Testing at Nuclear Power Plants, Rev. 3, Appendix A, describes a method to align the snubber program with IST program.
  • Snubber program alignment with the ISI or IST 10-year interval should be clearly specified in the snubber program, along with start and end dates.

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Inservice Examination and Testing of Snubbers ASME BPV Code vs ASME OM Code (cont.)

NRC Recommendation

  • Originally the Snubber Program was aligned with ISI 10-year interval.
  • At this time, all plants should be using the ASME OM Code for snubbers.
  • Many licensees have aligned Snubber Program update to the IST 10-year program update. This change should be carefully evaluated. If realigning the update causes a schedule extension beyond the requirements of ASME OM Code, ISTA-3120, Inservice Examination and Test Interval, such extension must be authorized by NRC via an alternative to the Code requirements per 10 CFR 50.55a(z).
  • While using the ASME OM Code for inservice examination and testing of snubbers (pin-to-pin), the inspection of support structure and attachments must be performed by use of ASME BPV Code,Section XI.

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Snubber Program & Submittal Requirements

  • Major Difference between Pump & Valve 10-Year IST Program Interval Plan and Snubber 10-Year IST Program Interval Plan is as follows:
  • Pump & Valve 10-Year IST Program Interval Plan contains:
  • Pump Inservice Testing (ISTB-3000)
  • Valve Inservice Testing (ISTC-3000)
  • Snubber 10-Year IST Program Interval Plan contains ISTD-3000 including:
  • (1) Visual Examination;
  • (2) Functional Testing; and
  • (3) Service Life Monitoring.

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Snubber Program & Submittal Requirements (cont.)

Background

  • NRC staff observed that some of the licensees do not submit their snubber program to NRC.
  • Some licensees only submit the deleted Technical Specification (TS) pages containing snubber testing requirements without the applicable edition of the ASME OM Code requirements.
  • Some 10-year interval ISI or IST programs simply state that the snubber test plan (and/or snubber program) is being developed under snubber programs without providing additional information in the submittal.

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Snubber Program & Submittal Requirements (cont.)

Regulation

  • Snubber Program (inservice examination, testing and service life monitoring) plan is required to be submitted to the NRC
  • For ASME OM Code 2020 Edition and later, ISTA-3200 was modified and no longer requires submittal of the snubber program. Therefore, this requirement is incorporated directly in 10 CFR 50.55a(f)(7)
  • Regulatory Issue Summary (RIS) 2010-06, Inservice Inspection and Testing Requirements of Dynamic Restraints (Snubbers) 11

Snubber Program & Submittal Requirements (cont.)

==

Description:==

  • Whether the snubber program is developed as part of the ISI program under ASME BPV Section XI or as part of the IST program under ASME OM, licensees are required by 10 CFR 50.55a to submit the program to the NRC.
  • ASME OM Code, Division 1, Nonmandatory Appendix A, Preparation of Test Plans, and the Supplement to Nonmandatory Appendix A, provide guidelines for Snubber Program Plans.
  • NUREG-1482, Revision 3, Appendix A, provides guidance for snubber inservice examination and testing.

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Snubber Program & Submittal Requirements (cont.)

  • As specified in ASME OM Code, Division 1, Nonmandatory Appendix A, and NUREG-1482, Revision 3, Appendix A, the following items should be specified in the submitted Snubber Program:
  • Code of Record used for Snubber Program.
  • Start and End dates of the applicable 10-year ISI or IST Program interval for which Snubber Program is developed.
  • Snubber Program details, whether the snubber program is submitted as part of the 10-year ISI Program, the 10-year IST Program, or as a standalone submittal.
  • Snubber Program is based on the applicable ASME Code, not the plants Technical Specifications (TS) or Technical Requirement Manual (TRM).

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Snubber Program & Submittal Requirements (cont.)

  • (1) Visual Examination (ISTD-4200);
  • (2) Functional Testing (ISTD-5200); and
  • (3) Service Life Monitoring (ISTD-6000).
  • Use of 10% plan or 37 snubber plan (ISTD-5260)

Snubber Program & Submittal Requirements (cont.)

  • When developing the Snubber Program for a multi-plant fleet, licensees should include:
  • Applicable 10-year ISI or IST intervals including start and end dates for all plants.
  • Specific editions & addenda of ASME OM Code used for each plant.
  • Use of 10% plan or 37 snubber plan specified for all plants, separately if different.

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Service Life Monitoring (SLM) Program for Snubbers

Background

  • ASME OM Code, Subsection ISTD, requires that all snubbers in the scope shall meet the requirements for (1) visual examination (paragraph ISTD-4200); (2) functional testing (paragraph ISTD-5200); and (3) SLM (paragraph ISTD-6000).
  • ISTD-6100 requires that initial snubber service life shall be predicted based on manufacturers recommendation or design review. Methods for predicting service life are provided in ASME OM Code, Nonmandatory Appendix F, Dynamic Restraints (Snubbers)

Service Life Monitoring Methods.

  • ISTD-6200 requires that the service life for each location where a snubber is installed shall be reevaluated at least once each fuel cycle. Reevaluation shall be based on examination, maintenance, performance, and operating service-life history data associated with representative snubbers that have been in service in the plant, as well as other information related to service life.

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SLM Program for Snubbers (cont.)

  • SLM requires that the service life of each snubber shall be established and recorded every refueling outage. If the indicated service life will be exceeded prior to the next scheduled snubber service life review, the snubber service life shall be reevaluated, or the snubber shall be replaced or reconditioned so as to extend its service life beyond the date of the next scheduled service life review.

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SLM Program for Snubbers (cont.)

Issues

  • While developing the snubber program, some licensees are not implementing SLM as described in the OM Code, Subsection ISTD, and are only implementing (1) visual examination and (2) functional testing requirements.
  • Some licensees are not evaluating the service life of snubbers every refueling outage as required by the OM Code, ISTD-6000.
  • Some licensees update snubber programs to refer to plant procedures for snubber examinations and testing without providing references to the applicable SLM section of the OM Code, ISTD-6000.

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SLM Program for Snubbers (cont.)

Discussion

  • SLM is the key element of the snubber program along with (1) visual examination and (2) functional testing requirements as specified by ASME OM Code, Subsection ISTD.
  • SLM requires that service life of each installed snubber shall be reevaluated once each fuel cycle. Reevaluation shall be based on the vendors recommendation, examination, maintenance, performance, and operating service-life history data associated with representative snubbers that have been in service in nuclear power plants.

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SLM Program for Snubbers (cont.)

  • During 2014 visual examination of snubbers at five nuclear power plants refueling outages, a large number of mechanical snubbers were failed.
  • Most of these mechanical snubber failures were determined to be caused by grease degradation, such as: (1) oil separation from grease; (2) dried or caked grease; (3) excessive grease; (4) sticky and tacky grease; and (5) hardened or missing grease.
  • A well-planned SLM program for snubbers would have minimized or eliminated the number of snubber failures due to degradation of grease.
  • SLM would be able to detect failures due to leakage of the hydraulic snubbers.

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SLM Program for Snubbers (cont.)

  • The SLM program is the primary instrument for assuring continued reliability of a snubber population at a plant because
  • Snubber visual examination is only performed once 24 months or 48 months (ISTD-4200) or 10 years (if Code Case OMN-13 is used)
  • Snubber functional testing is based on small samples (10% or 37 snubbers) every refueling outage (ISTD-5200).
  • ASME OM Code, Division 1, Nonmandatory Appendix F, provides detailed guidelines for SLM.
  • Licensees are responsible for establishing, maintaining, and implementing an SLM program for all snubbers within the scope of the IST program.

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Use of Code Case OMN-13 and Visual Examination Frequency Issue:

  • Some licensees are not meeting the frequency provisions for snubber visual examination specified in Code Case OMN-13.

Requirements:

  • Code Case OMN-13, Section 3.7(a), Frequency of Examinations, specifies that All snubbers within the scope of Subsection ISTD shall be examined and evaluated per this Code Case at least once every 10 yr.
  • ASME OM Code, Subsection ISTA, General Requirements, paragraph ISTA-3170, Inservice Examination and Test Frequency Grace, provision for extended frequency does not apply to snubber visual examination and testing in Subsection ISTD.

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Use of Code Case OMN-13 and Visual Examination Frequency (cont.)

Guidelines:

  • While using Code Case OMN-13, the licensee needs to schedule the visual examination of all snubbers in their scope such that visual examination interval shall not exceed 10 years.
  • While using Code Case OMN-13 without proper planning during previous outage, if the licensee has come to an outage and finds the interval will exceed to 10 years. In this case, the licensee would need to request an alternative to exceed the 10-year maximum interval.

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Use of Code Case OMN-13 and Record of All Visual Examination Failures during the extended 10-year interval Issue:

  • NRC staff learned that while implementing Code Case OMN-13, some plants are not keeping records of their failures of snubber visual examinations and failures discovered during maintenance, snubber replacement, water hammer events, reservoir fluid level low, walkdowns, and service life monitoring during the 10-year extension.

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Use of Code Case OMN-13 and Record of All Visual Examination Failures during the extended 10-year interval (cont.)

Requirements:

  • Code Case OMN-13, Revision 2, Section 3.7(b), states, that if at any time during an examination interval the cumulative number of unacceptable snubbers exceeds the applicable value from Column B in Table ISTD-4252-1, Visual Examination Table, the current examination interval shall end, and all remaining examinations must be completed within the current fuel cycle.

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Use of Code Case OMN-13 and Record of All Visual Examination Failures during the extended 10-year interval (cont.)

Guidelines:

  • Examples of the cumulative number of unacceptable visual exam failures found during the 10-year extension:
  • Visual Examination
  • Maintenance
  • Any Walkdowns
  • Due to low fluid level
  • Testing If at any time, the total number of cumulative unacceptable visual exams for snubbers exceeds the applicable value from Column B in Table ISTD-4252-1, the current examination interval (10-year) shall end. For more details, see Notes of Table ISTD-4252-1.

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Conclusions

  • Licensees who believe that some of the items discussed in this presentation are applicable to their nuclear power plants may wish to review their current snubber program for any appropriate action.

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