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MOV Users Group January 2023 MOV Historical Perspective (Scarbrough)
	ML23018A089
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Issue date:	01/25/2023
From:	Thomas Scarbrough; NRC/NRR/DEX/EMIB
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Motor-Operated Valve Historical Perspective Thomas G. Scarbrough Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Motor-Operated Valve Users Group Meeting January 23-25, 2023 1

Topics

1. Past Motor-Operated Valve (MOV) Operating Experience and Issues

2. MOV Bulletin and Generic Letter Programs

3. MOV Regulations

4. ASME OM Code MOV Improvements

5. Lessons Learned from Power-Operated Valve (POV)

Inspections

6. Electric Power Research Institute (EPRI) 10 CFR Part 21 Letter dated August 17, 2022

7. Conclusions 2

1. Past MOV Operating Experience and Issues 3

Past MOV Operating Experience

NUREG-0660 included 1979 TMI-2 Accident Action Items II.E.4.2 (Containment) and II.E.6.1 (Valve Testing)

In 1980s, operating experience revealed weaknesses in design, qualification, maintenance, personnel training, and inservice testing (IST) for MOVs:

- Davis Besse Feedwater Failure (IN 85-50)

- Catawba Auxiliary Feedwater Failure (IN 89-61)

- Palisades PORV Block Valve Failure (AIT Nov. 1989)

Research programs by industry and NRC confirmed MOV design and qualification weaknesses.

NRC prepared NUREG-1352 and initiated regulatory action to address these weaknesses.

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Past MOV Issues

Underestimation of required valve thrust or torque from assumptions for differential pressure (DP), valve factors, butterfly valve torque coefficients, and unwedging.

Overestimation of motor actuator thrust or torque output from assumptions for actuator efficiency, degraded voltage effects, ambient temperature effects, stem friction, and load sensitive behavior.

Potential unpredictability of valve performance under high flow conditions.

Significant variation in MOV performance.

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Past MOV Issues (continued)

Deficiencies in MOV parts (e.g., torque and limit switches, motor shafts, pinion keys, valve yokes, and stem-disc connections).

Improper low voltage operation of motor brakes.

Inadequacies in some MOV diagnostic equipment in accurately measuring thrust and torque.

Gearbox and spring pack grease hardening.

Maintenance and training weaknesses.

Inadequate corrective action.

MOV magnesium rotor degradation.

Motor thermal overload issues.

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2. MOV Bulletin and Generic Letter Programs 7

Bulletin 85-03 Motor-Operated Valve Common Mode Failures During Plant Transients due to Improper Switch Settings

In response to MOV operating experience, Bulletin 85-03 requested licensees to test high-pressure safety-related MOVs under design-basis DP and flow conditions.

Supplement 1 clarified scope to all MOVs in specified systems and to address potential mispositioning.

Static testing primarily conducted.

Implementation results indicated about 8% of MOVs might not have operated under design-basis conditions.

Results supported development of GL 89-10 to expand scope to all safety-related MOVs.

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Generic Letter 89-10 Safety-Related Motor-Operated Valve Testing and Surveillance

Based on Bulletin 85-03 results, GL 89-10 requested licensees to verify design-basis capability of safety-related MOVs:

- Review MOV design bases

- Establish MOV switch settings

- Dynamically test MOVs where practicable

- Verify settings every 5 years and following maintenance

- Improve corrective action and trending MOV problems.

Licensees requested to complete GL 89-10 in 5 years or three refueling outages (RFOs).

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GL 89-10 Supplements Supplement 1 (June 13, 1990): Provided results of GL 89-10 workshops in fall 1989.

Supplement 2 (Aug. 3, 1990): Allowed additional time for incorporation of Supplement 1 into GL 89-10 programs.

Supplement 3 (Oct. 25, 1990): Accelerated review of isolation valves in high pressure coolant injection (HPCI),

reactor core isolation cooling (RCIC) system, and reactor water cleanup (RWCU) system in response to MOV tests.

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GL 89-10 Supplements Supplement 4 (Feb. 12, 1992): Deleted mispositioning from GL 89-10 scope for BWR plants.

Supplement 5 (June 28, 1993): Addressed MOV diagnostic equipment accuracy.

Supplement 6 (Mar. 8, 1994): Provided results of several GL 89-10 workshops including guidance on grouping and pressure locking.

Supplement 7 (Jan. 24, 1996): Deleted mispositioning from GL 89-10 scope for PWR plants.

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GL 89-10 Activities

NRC staff conducted inspections using Temporary Instruction (TI) 2515/109 to evaluate GL 89-10 program development, implementation, and completion.

NRC closed out GL 89-10 typically through inspections.

GL 89-10 implementation involved several million dollars at each NPP.

Following implementation, Boiling Water Reactor Owners Group (BWROG) reported at a public meeting an acceptable cost/benefit analysis based on resolution of numerous MOV deficiencies by GL 89-10 programs.

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Generic Letter 95-07 Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves

Pressure locking (PL) of flexwedge gate valve or parallel disc gate valve occurs when pressurized fluid in bonnet prevents valve opening.

Thermal binding (TB) of flexwedge or solid wedge gate valve caused by mechanical interference between valve disc and seat.

In response to PL/TB operating experience, GL 95-07 requested licensees to address potential PL/TB of power-operated gate valves.

NRC reviewed licensee submittals and prepared safety evaluation (SE) for each NPP.

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Generic Letter 96-05 Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves

To address long-term MOV capability, GL 96-05 requested licensees to develop programs to periodically verify MOV design-basis capability.

98 reactor units committed to implement Joint Owners Group (JOG) Program on MOV Periodic Verification.

Callaway, Fort Calhoun, Palisades, and San Onofre 2/3 reviewed separately.

SE prepared based on submittals and commitments.

Sample GL 96-05 inspections conducted at Callaway, Palisades, Peach Bottom, San Onofre, Seabrook, Saint Lucie, Summer, Turkey Point, and Vermont Yankee.

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3. MOV Regulations 15

NRC Regulations

10 CFR Part 50, Appendix A, General Design Criteria (GDC)

10 CFR Part 50, Appendix B, Quality Assurance (QA) criteria

10 CFR 50.49 - Electrical Equipment Environmental Qualification

10 CFR 50.55a - ASME OM Code IST requirements and regulatory conditions

10 CFR 50.69 - Risk-informed treatment approach

10 CFR Part 50, Appendix S - Seismic Qualification 16

10 CFR 50.55a (as of January 25, 2023)

ASME OM Code, 1995 Edition up to 2020 Edition, incorporated by reference with conditions.

50.55a(b)(3) includes conditions:

i. ASME Standard NQA-1 acceptable where supplemented by Appendix B of 10 CFR Part 50 as necessary ii. Periodic verification of MOV design-basis capability required, and Appendix III to OM Code acceptable with conditions iii. New Reactors:

Periodic verification of POV design-basis capability

Check valve bi-directional testing

Flow-induced vibration monitoring

Regulatory Treatment of Non-Safety Systems (RTNSS) iv. Appendix II check valve condition monitoring

v. Subsection ISTD for snubbers 17

10 CFR 50.55a (continued)

(b)(3) continued:

vi. Manual valve 2-year exercise interval vii. Reserved viii. Use of Subsection ISTE requires 50.55a(z) alternative for 2017 and earlier editions ix. Use of Subsection ISTF (2012 Edition) requires Appendix V

x. Reserved xi. Valve position indication supplemented beginning with OM Code, 2012 Edition. ASME OM Code Case OMN-28 accepted without conditions for valves with stem-disk connections not susceptible to separation. Extension of implementation date for initial supplemental valve position verification to next available opportunity may be justified where not later than next plant shutdown.

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10 CFR 50.55a (continued)

(f)(4) requires that pumps and valves within scope of ASME OM Code meet IST requirements set forth in ASME OM Code. IST requirements for pumps and valves within scope of ASME OM Code but not classified as ASME BPV Code Class 1, 2, or 3 may be satisfied by an augmented IST program without prior NRC approval provided basis for deviations from ASME OM Code demonstrates acceptable level of quality and safety, or implementing Code provisions would result in hardship or unusual difficulty without compensating increase in level of quality and safety, where documented and available for NRC review.

(f)(4)(i) and (ii) requires latest OM Code incorporated by reference 18 months before fuel load for initial 10-year IST interval and 18 months before successive IST intervals.

(f)(7) requires that IST Program Plans for pumps, valves, and snubbers be submitted to the NRC per 10 CFR 50.4 within 90 days of implementation for each 120-month IST Program interval.

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10 CFR 50.55a(b)(3)(ii)

(as of January 25, 2023)

Licensees must comply with MOV testing provisions in ASME OM Code, and establish a program to ensure that MOVs continue to capable of performing design basis safety functions.

Licensees implementing Appendix III shall:

(A) Evaluate adequacy of MOV diagnostic test intervals not later than 5 years or 3 RFOs from initial implementation.

(B) Ensure that potential increase in CDF and LERF is acceptably small when extending exercise intervals for high risk MOVs.

(C) Categorize MOVs using OMN-3 or accepted risk-ranking method.

(D) Verify that stroke time of MOVs specified in plant Tech Specs satisfies plant safety analysis assumptions when exercising.

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4. MOV Improvements in ASME OM Code 21

ASME OM Code, Appendix III Preservice and Inservice Testing of Active Electric Motor-Operated Valve Assemblies in Light-Water Reactor Power Plants

Establishes requirements for Preservice Testing (PST) and IST to assess operational readiness of active MOVs.

Design Basis Verification Test is one-time test-based method to verify MOV capability to meet safety-related design-basis requirements.

PST as near as practicable to subsequent IST.

Exercise once per refueling cycle not to exceed 24 months.

Additional exercising for MOVs with high-risk significance, adverse environments, or abnormal characteristics.

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ASME OM Code, Appendix III (continued)

Diagnostic IST to assess changes in MOV functional margin not to exceed 10-year interval.

Risk-informed provisions for High Safety Significant Component (HSSC) and Low Safety Significant Component (LSSC) MOVs.

Following diagnostic IST, declare MOV inoperable if functional margin does not meet acceptance criteria.

MOV test interval shall be set such that MOV functional margin does not decrease below acceptance criteria.

In addition to test data and results, test information shall document abnormal MOV operation.

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ASME Code Case OMN-26

ASME OM Code Case OMN-26, Alternate Risk-Informed and Margin-Based Rules for Inservice Testing of Motor-Operated Valves, allows extension of maximum MOV diagnostic test interval beyond 10 years specified in Appendix III.

Code Case OMN-26 based on risk-informed approach for HSSC and LSSC MOVs, and experience with JOG test intervals.

Code Case OMN-26 accepted in Revision 4 to Regulatory Guide 1.192 as incorporated by reference in 10 CFR 50.55a without conditions.

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5. Lessons Learned from Power-Operated Valve (POV)

Inspections 25

POV Inspection Program

On July 26, 2019, NRC issued Inspection Procedure (IP) 71111.21N.02, Design-Basis Capability of Power-Operated Valves Under 10 CFR 50.55a Requirements

Inspection objective is to assess the reliability, functional capability, and design-basis of risk-important power-operated valves (POVs) at nuclear power plants.

Training provided for inspectors in NRC Region offices.

POV inspections began in January 2020 and completed at the end of 2022.

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POV Inspection Approach

POV inspections focus on sample selection, scope, design, testing, and maintenance and corrective actions.

POV inspections at each site include a sample of 8 to 12 POVs including:

- Motor-Operated Valves (MOVs)

- Air-Operated Valves (AOVs)

- Hydraulic-Operated Valves (HOVs)

- Solenoid-Operated Valves (SOVs)

- Pyrotechnic-Operated (Squib) Valves

Some inspections relied on partial remote means due to COVID-19 limitations.

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POV Region Panels

Draft findings from each POV inspection were presented to an NRC staff panel consisting of representatives from each NRC Region office and headquarters.

POV Region Panel discussed each POV inspection finding in comparison to findings from previous POV inspections.

Review by POV Region Panel provided consistency of NRC staff technical positions during POV inspections across the NRC Regions.

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POV Inspection Results

POV inspections identified several Green Non-Cited Violations (NCVs) and numerous minor and licensee identified violations.

At a virtual public meeting on December 8, 2020, NRC staff discussed lessons learned from the POV inspections up to that time.

14 categories of lessons learned from POV inspections are presented in NRC Information Notice (IN) 2021-01 (May 6, 2021), Lessons Learned from U.S. Nuclear Regulatory Commission Inspections of Design-Basis Capability of Power-Operated Valves at Nuclear Power Plants.

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IN 2021-01 POV Inspection Lessons Learned

1. Ensure IST Programs are fully consistent with ASME OM Code, such as addressing all POV safety functions, and maintaining POV risk rankings up to date.

2. Address ASME OM Code, Appendix III, requirement for mix of static and dynamic testing.

3. Follow NRC-accepted commitment change process (e.g.,

JOG MOV Periodic Verification Program does not include test interval grace periods).

4. Properly determine POV operating requirements and actuator capability, including parameters used in calculations such as friction values, temperature, pressure, and flow.

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IN 2021-01 POV Inspection Lessons Learned

5. JOG Program determined potential for degradation of valve friction coefficients, but did not establish valve friction database (i.e., JOG program evaluated change in friction coefficients rather than actual coefficients).

6. Establish methods to periodically demonstrate design-basis capability of JOG Class D valves.

7. Address conditions for EPRI MOV Performance Prediction Methodology (PPM) applicability, such as maintaining valve in good internal condition. See NUREG-1482 (Revision 3).

8. Properly justify increasing Limitorque actuator thrust ratings. See IN 92-83.

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IN 2021-01 POV Inspection Lessons Learned

9. Properly conduct POV testing and adequately evaluate results to demonstrate POV can perform its safety function.

a) Properly translate test acceptance criteria from design calculations to test procedures (e.g., measured static thrust greater than allowed in design calculations) b) Verify diagnostic equipment installed and operating properly c) Evaluate test data for full valve stroke d) Verify required parameters are within acceptable range e) Determine if test data exceed JOG threshold values f) Address potential variation of data from single test g) Justify reliance on static diagnostic testing h) Periodic evaluation of thermal overload devices i) Prepare monitoring reports in accordance with plant procedures 32

IN 2021-01 POV Inspection Lessons Learned

10. Provide assurance that MOVs set on limit control under static conditions will fully close under dynamic conditions.

11. Provide assurance of qualified life of POVs if extended.

12. Properly implement guidance provided by Boiling Water Reactor Owners Group (BWROG) for assessing susceptibility of separation of stem-disk connection in Anchor/Darling double-disk gate valves (see IN 2017-03).

13. Implement 10 CFR 50.55a(b)(3)(xi) for supplemental valve position indication when conducting testing for ISTC-3700 in ASME OM Code (2012 or later edition).

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IN 2021-01 POV Inspection Lessons Learned

14. Justify POV preventive maintenance schedules based on vendor recommendations and plant experience (e.g.,

MOVs in high temperature areas might need more frequent stem lubrication, and MOVs in non-normal positions might need additional attention, such as limit switch cover facing down might experience grease intrusion).

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2021 POV Inspection Lessons Learned

At a public meeting with the BWROG on December 7, 2021, the NRC staff presented lessons learned from the POV inspections conducted since the preparation of IN 2021-01 up to the fall of 2021.

The following slides indicate the lessons learned from POV inspections conducted in the 2021 time period as presented at the December 2021 BWROG meeting.

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2021 POV Inspection Lessons Learned

Evaluation of possible consequences of drilling a hole in valve disk when preventing pressure locking

JOG program schedule does not include grace periods so commitment change process needed

Monitoring torque limits when operating a valve by its manual handwheel

Ensuring leak rate requirements met for MOVs with long closing torque switch bypass

Improper reliance on one-time stall torque limits for actuator margin calculations

Determination of stem lube degradation factor for ball-screw stem nut 36

2021 POV Inspection Lessons Learned

Identification and correction of degraded magnesium MOV motor rotors

Consideration of gate valve unwedging force

Modification of JOG program schedule commitments

10 CFR 50.59 evaluations for valve pressure locking modifications

Evaluation of MOVs with design-basis safety functions to throttle flow

Potential for improper stroke time calculations that rely on computer data

Updating POV surveillance program following Probabilistic Risk Assessment (PRA) update 37

2021 POV Inspection Lessons Learned

Response to EPRI MOV PPM Type 1 warnings

Verification that installed POVs match calculation assumptions

Maintaining EPRI MOV PPM long-term applicability

Monitoring of industry data for valves where EPRI MOV PPM is used as the best available information

Verification and Validation of POV software

Removal of valves from 10 CFR Part 50, Appendix J Program without adequate technical justification 38