ML21222A133
| ML21222A133 | |
| Person / Time | |
|---|---|
| Issue date: | 08/10/2021 |
| From: | Michael Farnan NRC/NRR/DEX/EMIB |
| To: | |
| Michael F Farnan 301-415-1486 | |
| References | |
| Download: ML21222A133 (17) | |
Text
Nuclear Industry Check Valve Regulatory Activities Michael F. Farnan Mechanical Engineering and Inservice Testing Branch Division of Engineering & External Hazards Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission NIC Virtual Meeting August 2021 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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Current NRC Activities
- 10 CFR 50.55a Rulemaking
- Summary of Key Issues on Power Operated Valve (POV)
Inspections (IN 21-01)
- Surry White Finding 3
50.55a Rulemaking
- Proposed rulemaking for ASME OM Code 2020 Edition published on March 26, 2021 (86 FR 16087) with a 60 day comment period
- Final rule is scheduled to be published in the spring of 2022
- Final rule takes effect 30 days after being published in the Federal Register 4
50.55a Rulemaking - Impact on CV
- Add 10 CFR 50.55a(f)(7) to require nuclear power plant applicants and licensees to submit their IST Plans and interim IST Plan updates related to pumps and valves, and IST Plans and interim Plan updates related to snubber examination and testing to the NRC.
- Consideration of proposed relaxation of the interval for position indication testing required in ISTC-3700 for valves that are not susceptible to stem-disk separation.
(similar to ASME OM Code Case OMN-28) 5
Design Bases Assurance Inspection (Programs) for Power-Operated Valves 2020 Inspection Findings 15
POV Inspection Findings 2020
- A total of 18 sites / 30 plants inspected in 2020
- Inspection at each site focused on a select 8 - 12 POVs including
- MOVs
- AOVs
- HOVs
- SOVs
- squib valves
- Many inspections were conducted using remote means due to COVID-19.
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POV Inspection Findings 2020
- Many remote inspections conducted walkdowns onsite, or used resident inspectors as proxy in conducting walkdowns.
- Early communications between NRC inspectors and licensee staff were instrumental in focusing the inspection on safety significant and risk-informed valve samples.
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POV Inspection Findings 2020
- 8 Green Non-Cited Violations (NCVs) identified.
- Multiple minor and licensee identified violations
- Many licensee identified violations were found using experience from first two POV inspections
- Findings were collated into 14 high level event categories and presented at a public meeting held on December 8, 2020.
- Findings were presented to public via Information Notice 2021-01 9
POV Inspection Findings 2020 Summary
- Many findings were due to lack of attention to detail
- Changes in risk values that affect test intervals were not being updated in programs that apply risk
- Changes to commitments without applying the commitment change process which includes notification to NRC staff
- Incorrect parameters used in calculations such as friction values, temperatures, pressures, and flows. Also errors in parameters found when plants updated to new software program
- Several instances of changes to design calculations did not translate new acceptance criteria into test procedures
- Diagnostic sensor placed in the wrong position (above anti-rotation device) causing as-found data to be incorrect.
- Licensees not evaluating tested data (e.g., measured valve factor (VF) greater than design, and stem factor not evaluated for change).
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POV Inspection Findings 2020 Summary
- Many findings were due to lack of attention to detail (contd)
- Used JOG threshold valve friction value in design calculation even after tested value much greater
- Some licensees did not provide additional attention to the qualified life of POVs installed in their nuclear power plants
- Some licensees did not properly implement the guidance provided by the Boiling Water Reactor Owners Group (BWROG) when assessing the susceptibility for separation of the stem-disk connection in Anchor/Darling double-disk gate (DDG) valves
- Licensees need to justify their POV preventive maintenance schedules based on vendor recommendations and their own plant experience (e.g., MOVs in high temperature area may need more frequent stem lube PM, MOVs in non-normal position may need additional attention such as limit switch cover facing down may experience grease intrusion) 11
POV Inspection Findings 2020 Summary
- Some licensees were using JOG test data to justify valve capability of performing its safety function without performing a dynamic test
- During development of JOG program plan, industry specified to NRC staff that the program plan was intended to determine degradation over time, and that valve friction threshold values were not intended to be used to justify a valve with no additional dynamic testing.
- Applying method to valves that were not covered by EPRI PPM
- Extending the limits of the PPM (e.g., stainless steel materials can be subject to galling above 150 degrees F).
- EPRI PPM report states for the PPM to remain valid, end users must ensure that the internals remain in good condition 12
Surry White Finding
- Surveillance AFW crosstie capability test 11/20/2019 failed due to TDAFWP discharge check valve stuck open
- Check valve stuck open caused the TDAFWP to rotate backwards
- Partially diverted flow rendered all three auxiliary feedwater pumps unable to provide FSAR minimum required flow to the steam generators.
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Surry White Finding - Valve History
- Commercial operation in 1973
- Valve failed leak test in 1987. Valve was lapped and returned to service
- Valve lapped again in 1989, 1991, and replaced in 1993
- 1995 PM established to periodically open and inspect.
Work package noted that a condition monitoring (CM) program could replace this PM in future.
- 2005 expert panel convened to develop CM plan
- Industry data was reviewed for specific model valve
- Expert panel recommends only a leak test needed for CM task 14
Surry White Finding - Appendix II Requirements
- The Owner shall perform an analysis of the test and maintenance history of a valve or group of valves in order to establish the basis for specifying inservice testing, examination, and preventive maintenance activities. The analysis shall include the following:
- Identify any common failure or maintenance patterns
- Analyze these patterns to determine their significance and identify potential failure mechanisms 15
Surry White Finding - Valve Failure
- Valve experienced excessive wear
- The circular holes in the swing arm assembly that the hinge pin connects were no longer round but oblong
- Shoulders on the disk and mating surfaces were also worn
- The oblong holes allowed the disk to be lower than normal and eventually hung up on the valve internals leaving the disk partially open instead of closed.
- Valve failure on a common header rendered all three auxiliary feedwater pumps incapable of meeting the minimum required flow to the steam generators.
- TDAFWP rotating backwards caused damage to the pump bearings and the turbine 16
QUESTIONS?
Future Questions Michael.Farnan@nrc.gov 301-415-1486 17