ML25206A070
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| ML25206A070 | |
| Person / Time | |
|---|---|
| Issue date: | 07/25/2025 |
| From: | Nicholas Hansing NRC/NRR/DEX/EMIB |
| To: | |
| References | |
| Download: ML25206A070 (1) | |
Text
NRC Staff Presentation 2025 ASME/NRC OM Symposium Nicholas J. Hansing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission 1
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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Safety Significant Check Valves 3
Safety Significant Check Valves
- Check valves are used in numerous safety applications in nuclear power plants.
- Many check valves were installed when the nuclear power plant was constructed and can be over 40 years old.
- Probabilistic risk assessments (PRAs) for nuclear power plants might not model all check valves in their evaluations of plant risk.
- Where included in risk evaluations, the check valve failure rates might be based on valves that have not experienced many years of aging.
- Potential common cause failure of entire safety systems by the failure of a single check valve might not be fully addressed by quantitative and qualitative safety studies for nuclear power plants.
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Check Valve Failure Examples
- IN 81-35, Check Valve Failures
- IN 82-08, Check Valve Failures on Diesel Generator Engine Cooling System
- IN 82-20, Check Valve Problems
- Bulletin 83-03, Check Valve Failures in Raw Water Cooling Systems of Diesel Generators
- IN 86-01, Failure of Main Feedwater Check Valves Causes Loss of Feedwater System Integrity and Water-Hammer Damage
- IN 88-70, Check Valve Inservice Testing Program Deficiencies 5
Additional Check Valve Failure Examples
- NUREG-1352 (1990), Action Plans for Motor-Operated Valves and Check Valves
- IN 2000-21, Detached Check Valve Disc Not Detected by Use of Acoustic and Magnetic Nonintrusive Test Techniques
- NRC Inspection Report 05000281/202004, December 30, 2020, (ML20365A007) describing check valve failure causing loss of Auxiliary Feedwater System.
- Industry has issued numerous studies of check valve failures.
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Guidance for Safety Significant Check Valves
- ASME OM Code requires quarterly exercising of check valves in the IST Program where practicable.
- ASME OM Code, Appendix II, allows implementation of a condition monitoring program with general provisions.
- ASME guidance for acceptable intrusive and non-intrusive methods for monitoring internal check valve wear could be used to update the ASME OM Code requirements to avoid adverse impacts from check valve failures.
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Guidance for Safety Significant Check Valves
- An ASME OM initiative to address high risk check valves was recently abandoned in part due to licensees' inability to identify that population of valves in question.
- The NRC staff believes a review of plant drawings can identify those valves where failure would challenge defense in depth (e.g.,
cause a loss of function of multiple trains)
- ASME guidance for acceptable intrusive and non-intrusive methods for monitoring internal check valve wear could be used to update the ASME OM Code requirements to avoid adverse impacts from check valve failures.
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QUESTIONS?
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