ML24327A055
| ML24327A055 | |
| Person / Time | |
|---|---|
| Issue date: | 11/22/2024 |
| From: | Thomas Scarbrough NRC/NRR/DEX/EMIB |
| To: | |
| References | |
| Download: ML24327A055 (1) | |
Text
NRC Staff Presentation on ASME OM Code Case OMN-28 Thomas G. Scarbrough Division of Engineering and External Hazards Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Inservice Testing Owners Group Meeting December 2024 1
2 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.
Topics
- NRC Regulatory Conditions
- EPRI Report on Valve Stem-Disk Connections
- NRC Safety Evaluation
- Summary 3
ASME OM Code Subsection ISTC ISTC-3700 (2022 Edition) states:
Valves with remote position indicators shall be observed locally at least once every 2 yr to verify that valve operation is accurately indicated. Where practicable, this local observation should be supplemented by other indications such as use of flow meters or other suitable instrumentation to verify obturator position. These observations need not be concurrent. Where local observation is not possible, other indications shall be used for verification of valve operation. Position verification for active MOVs shall be tested in accordance with Division 1, Mandatory Appendix III.
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ASME OM Code Appendix III and IV ASME OM Code, Mandatory Appendix III, Preservice and Inservice Testing of Active Electric Motor-Operated Valve Assemblies in Water-Cooled Reactor Nuclear Power Plants, Section III-3300, Inservice Test, paragraph (e) states:
Remote position indication shall be verified locally during inservice testing or maintenance activities.
ASME OM Code, Mandatory Appendix IV, Preservice and Inservice Testing of Active Pneumatically Operated Valve Assemblies in Nuclear Reactor Power Plants, Section IV-3400, Inservice Testing, paragraph (e), requires for each AOV:
Position verification testing, for valves with remote position indicators, in accordance with ISTC-3700, as applicable 5
- For 2012 Edition and later, licensees must verify valve operation is accurately indicated by supplementing valve position indicating lights with other indications, such as flow meters or other suitable instrumentation to provide assurance of proper obturator position for valves with remote position indication within the scope of Subsection ISTC including its mandatory appendices and their verification methods and frequencies.
- For valves not susceptible to stem-disk separation, licensees may implement OMN-28.
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(continued)
Where plant conditions make it impractical to perform the initial ISTC-3700 test as supplemented by (b)(3)(xi) by the date 2 years following the previously performed ISTC-3700 test, a licensee may justify an extension of this initial supplemental valve position verification provided the ISTC-3700 test as supplemented by (b)(3)(xi) is performed at the next available opportunity and no later than the next plant shutdown.
One-time extension of ISTC-3700 test schedule as supplemented by (b)(3)(xi) is acceptable provided licensee has available for NRC review documented justification based on information obtained over previous 5 years of structural integrity of stem-disk connection for applicable valves.
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(continued)
Licensee's justification could be based on, for example, verification of valve stem-disk connection through appropriate weak link analysis, appropriate disk motion confirmed during diagnostic testing, or allowance and cessation of flow through the valves.
Licensee's justification must provide reasonable assurance that the remote indicating lights accurately reveal the position of the valve obturator until the next ISTC-3700 test as supplemented by (b)(3)(xi) is performed.
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Code Case OMN-28, Alternative to ISTC-3700 Scope includes stem-disk separation non-susceptible valves with remote position indication.
Non-susceptible categorization requires documented justification including internal design, service conditions, applications and evaluation of connection using plant and industry experience, and vendor recommendations.
Valve position testing includes observation of evidence of valve operation, local observation where practicable, and stem-disk separation evaluation documented and available for review.
Active valves: Observation once every 12 years.
Passive valves: Observation when stroked or every 12 years, whichever greater.
If connection fails, then outside OMN-28 scope until corrective action meets categorization requirements.
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EPRI Report on Valve Stem-Disk Connections EPRI Technical Report 3002019621, Susceptibility of Valve Applications to Failure of the Stem-to-Disk Connection, Revision A, September 2020, (ML22200A297 Public), Non-Proprietary Version Report reviews valve stem-to-disk connection designs, and plant operating experience with those designs, to evaluate susceptibility to stem-to-disk separation under different operating conditions.
Report discusses verification methods to provide a direct indication that the stem-to-disk connection is intact for various valve types.
Report does not recommend supplemental verification intervals, but provides information that may be useful in selecting an interval.
Report covers valve stem-to-disk connection designs used in typical power-operated valves (POVs) and manually operated valves.
Report does not specifically address check valves or relief valves.
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NRC Safety Evaluation SE issued 5-4-2022 (Package ML22042A000) found TR acceptable for referencing in licensing applications for nuclear power plants to the extent specified and under limitations in the TR and SE.
EPRI TR used INPO IRIS database to identify valve stem-to-disk failures over a period of 43 years from 1977 through 2019 with 226 failures identified by searching several key words.
NRC staff searched INPO IRIS database for additional valve failures, which yielded many more failures and/or near-miss events.
NRC staff concluded that EPRI TR represents a comprehensive study on the failure rate of various valve designs.
Based on its evaluation, NRC staff found the use of EPRI TR, with the conditions in the SE, to be acceptable as part of implementation of Code Case OMN-28.
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SE Conditions EPRI TR acceptable to implement operating experience provisions of Code Case OMN-28 with conditions discussed in SE as summarized:
- 1. Application of TR is acceptable to determine that a valve is not susceptible to stem-to-disk separation if a documented engineering evaluation of operating experience justifies the conclusion, in accordance with the NRC staff evaluation of each valve design in SE sections 3.3.1 through 3.3.11, and is available for NRC inspection and audit, with the additional conditions below.
- 2. For a valve design that relies on a weld to secure the stem-to-disk connection and operates under high vibration conditions, application of TR is acceptable to determine that the valve is not susceptible to stem-to-disk separation if the documented engineering evaluation called for by Condition 1 includes additional justification for relying on the welded connection.
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SE Conditions (continued)
- 3. Application is acceptable to determine that a bolted valve is not susceptible to stem-to-disk separation if the documented engineering evaluation called for by Condition 1 includes an assessment of the effects of vibration on internal connection components.
- 4. Application is acceptable to determine that a butterfly valve that has a pinned connection is not susceptible to stem-to-disk separation if documented engineering evaluation called for by Condition 1 assesses lessons learned from operating experience for such valves concerning system conditions, including but not limited to vibration and valve operation, and justifies reliance on any PM measures, including but not limited to disassembly, inspection, and refurbishment, to demonstrate that the valve is not susceptible to stem-to-disk separation.
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SE Conditions (continued)
- 5. For each valve without extensive operating experience information (e.g., a hermetically sealed valve), the valve may be classified as not susceptible to stem-disk separation if the documented engineering evaluation of the valve called for by Condition 1 assesses the specific valve designs susceptibility to stem-disk separation.
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Applications of OMN-28
- OMN-28 together with the EPRI TR and NRC SE can be used to support implementation of ISTC-3700 to provide confidence in the integrity of the stem-disk connection of particular valve designs.
- OMN-28 may be applied where diagnostic test data for MOVs required in Appendix III and AOVs required in Appendix IV are not sufficient to justify the integrity of the stem-disk connection.
- OMN-28 may also be applied for other valve types to provide confidence in the integrity of the stem-disk connection.
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Summary EPRI TR is acceptable in implementing Code Case OMN-28 with conditions discussed in NRC Safety Evaluation.
Based on SE findings, each licensee must have a documented engineering evaluation of operating experience for its applicable POVs including EPRI TR information, NRC SE information, and other operating experience identified by the licensee.
A licensee is only responsible for addressing operating experience for POVs for which OMN-28 will be applied at its nuclear power plant.
OMN-28 and EPRI TR as accepted in the NRC SE could be helpful in meeting ASME OM Code, Appendix III, paragraph III-3300(e) for MOVs, and Appendix IV, paragraph IV-3400(e) for AOVs.
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QUESTIONS?
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Acronyms AOV: Air-Operated Valve or Pneumatically Operated Valve ASME: American Society of Mechanical Engineers CFR: Code of Federal Regulations EPRI: Electric Power Research Institute INPO: Institute of Nuclear Power Operations IRIS: International Research Integration System IST: Inservice Testing MOV: Motor-Operated Valve NRC: U.S. Nuclear Regulatory Commission OM: Operation and Maintenance PM: Preventive Maintenance POV: Power-Operated Valve RG: Regulatory Guide SE: Safety Evaluation TR: Technical Report YR: Year 18