ML20207B662

SER Finding That Licensee Established Acceptable Program to Periodically Verify design-basis Capability of safety-related MOVs at TMI-1 & That Util Adequately Addressed Actions Required in GL 96-05

ML20207B662
Person / Time
Site:	Three Mile Island
Issue date:	05/27/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20207B659	List: ML20207B654 ML20207B662
References
GL-89-10, GL-96-05, GL-96-5, NUDOCS 9906020059
Download: ML20207B662 (8)

Text

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UNITED STATES g

j NUCLEAR REGULATORY COMMISSION e

f WASHINGTON, D.C. 20565-0001

.....,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION LICENSEE RESPONSE TO GENERIC LETTER 96-05. " PERIODIC VERIFICATION OF DESIGN-BASIS CAPABILITY OF SAFETY-RELATED MOTOR-OPERATED VALVES" THREE MILE ISLAND NUCLEAR STATION. UNIT 1 DOCKET NO. 50-289

1.0 INTRODUCTION

Many fluid systems at nuclear power plants depend on the successful operation of motor-operated valves (MOVs)in performing their safety functions. Several years ago, MOV operating experience and testing, and research programs sponsored by the nuclear industry and the U. S. Nuclear Regulatory Commission (NRC), revealed weaknesses in a wide range of activities (including design, qualification, testing, and maintenance) associated with the performance of MOVs in nuclear power plants. For example, some engineering analyses used in sizing and setting MOVs did not adequately predict the thrust and torque required to operate valves under their design-basis conditions. In addition, inservice tests of valve stroke time under zero differential-pressure and flow conditions did not ensure that MOVs could perform their safety functions under design-basis conditions.

Upon identification of the weaknesses in MOV performance, significant industry and regulatory activities were initiated to verify the design-basis capability of safety-related MOVs in nuclear power plants. After completion of these activities, nuclear power plant licensees began establishing long-term programs to maintain the design-basis capability of their safety-related MOVs. This safety evaluation addresses the program developed by GPU Nuclear, Inc.

(licensee) to periodically verify the design-basis capability of safety-related MOVs at the Three Mile Island Nuclear Station, Unit 1 (TMI-1).

2.0 REGULATORY REQUIREMENTS The NRC regulations require that MOVs important to safety be treated in a manner that provides assurance of their intended performance. Criterion 1 to Appendix A," General Design Criteria for Nuclear Power Plants," to Part 50 of Title 10 of the Code of FederalRegulations (10 CFR Part 50) states, in part, that structures, systems, and components important to safety shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed. The quality assurance program to be applied to safety-related components is described in Appendix B, " Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants," to 10 CFR Part 50. In Section l

50.55a of 10 CFR Part 50, the NRC requires licensees to establish inservice testing (IST) l programs in accordance with Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code.

9906020059 990527 PDR ADOCK 05000209 P

PDR Enclosure

2 In response to concems regarding MOV performance, the NRC staff issued Generic Letter (GL) 89-10 (June 28,1989), " Safety-Related Motor-Operated Valve Testing and Surveillance,"

which requested that nuclear power plant licensees and construction permit holders ensure the capability of MOVs in safety-related systems to perform their intended functions by reviewing MOV design bases, verifying MOV switch settings initially and periodically, testing MOVs under design-basis conditions where practicable, improving evaluations of MOV failures and necessary corrective action, and trending MOV problems. The staff requested that licensees complete the GL 89-10 program within approximately three refueling outages or 5 years from the issuance of the generic letter. Permit holders were requested to complete the GL 8910 program before plant startup or in accordance with the above schedule, whichever was later.

The NRC staff issued seven supplements to GL 89-10 that provided additional guidance and information on MOV program scope, design-basis reviews, switch settings, testing, periodic verification, trending, and schedule extensions. GL 89-10 and its supplements provided only limited guidance regarding MOV periodic verification and the measures appropriato to ensure preservation of design-basis capability. Consequently, the staff determined that additional guidance on the periodic verification of MOV design-basis capability should be prepared.

On September 18,1996, the NRC staff issued GL 96-05, " Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves," requesting that each licensee establish a program, or ensure the effectiveness of its current program, to verify on a periodic basis that safety-related MOVs continue to be capable of performing their safety functions within the current licensing bases of the facility. In GL 96-05, the NRC staff summarized several industry and regulatory activities and programs related to maintaining long-term capability of safety-related MOVs. For example, GL 96-05 discussed non-mandatory ASME Code Case OMN-1," Alternative Rules for Preservice and Inservice Testing of Certain Electric Motor Operated Valve Assemblies in LWR Power Plants, OM Code 1995 Edition; Subsection ISTC,"

which allows the replacement of ASME Code requirements for MOV quarterly stroke-time testing with exercising of safety-related MOVs at least once per operating cycle and periodic MOV diagnostic testing on a frequency to be determined on the basis of margin and degradation rate. In GL 96-05, the NRC staff stated that the method in OMN-1 meets the intent of the generic letter with certain limitations. The NRC staff also noted in GL 96-05 that licensees remain bound by the requirements in their code of record regarding MOV stroke-time testing, as cupplemented by relief requests approved by the NRC staff.

In GL 96-05, licensees were requested to submit the following information to the NRC:

a.

within 60 days from the date of GL 96-05, a written response indicating whether or not the licensee would implement the requested actions; and b.

within 180 days from the date of GL 96-05, or upon notification to the NRC of completion of GL 89-10 (whichever was later), a written summary description of l

the licensee's MOV periodic verification program.

I The NRC staff is preparing safety evaluations on the response of each licensee to GL 96-05.

The NRC staff intends to rely to a significant extent on an industry initiative to identify valve age-related degradation which could adversely affect the design-basis capability of I

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' safety-related MOVs (described in Section 3.0) where a licensee commits to implement that industry program. The NRC staff will conduct inspections to verify the implementation of GL 96-05 programs at nuclear power plants as necessary.

3.0 JOINT OWNERS GROUP PROGRAM ON MOV PERIODIC VERIFICATION in response to GL 96-05, the Boiling Water Reactor Owners Group '(BWROG), Westinghouse Owners Group (WOG), and Combustion Engineering Owners Group (CEOG) jointly developed an MOV penodec verification program to obtain benefits from the sharing of information between hcensees. The Joint Owners Group (JOG) Program on MOV Periodic Verification is described by the BWROG in its Licensing Topical Report NEDC-32719, "BWR Owners' Group Program on Motor-Operated Valve (MOV) Periodic Verification," and described by the WOG i

I and the CEOG in their separately submitted Topical Report MPR-1807, " Joint BWR, Westinghouse and Combustion Engineering Owners' Group Program on Motor-Operated Valve (MOV) Periodic Verification." The stated objectives of the JOG Program on MOV

Periodec Venficatlon are (1) to provide an approach for licensees to use immediately in their GL 96-05 programs, (2) to develop a basis for addressing the potential age-related increase in required thrust or torque under dynamic conditions, and (3) to use the developed basis to confirm, or if necessary to modify, the applied approach. The specific elements of the JOG program are (1) providing an " interim" MOV periodic verification program for applicable licensees to use in response to GL 96-05, (2) conducting a dynamic testing program over the next 5 years to identify potential age-related increases in required thrust or torque to operate gate, globe, and butterfly valves under dynamic conditions, and (3) evaluating the information from the dynamic testing prcgram to confirm or modify the interim program assumptions.

The JOG interim MOV periodic verification program includes (1) continuation of MOV stroke-time testing required by the ASME Code IST program, and (2) performance of MOV static diagnostic testing on a frequency based on functional capability (age-related degradation margin over and above margin for GL 89-10 evaluated parameters) and safety significance. In implementing the interim MOV static diagnostic test program, licensees will rank MOVs within the scope of the JOG program according to their safety significance. The JOG program specifies that licensees need to justify their approach for risk ranking MOVs. In Topical Report NEDC-32264, " Application of Probabilistic Safety Assessment to Generic Letter 89-10 Implementation," the BWROG described a methodology to rank MOVs in GL 89-10 programs with respect to their relative importance to core-damage frequency and other considerations to be added by an expert panel. In a safety evaluation dated February 27,1996, the NRC staff accepted the BWROG methodology for risk ranking MOVs in boiling water reactor (BWR) nuclear plants with certain conditions and limitations. In the NRC safety evaluation dated October 30,1997, on the JOG Program on MOV Periodic Verification, the NRC staff indicated its view that the BWROG methodology for MOV risk ranking is appropriate for use in response to GL 96-05. With respect to Westinghouse-designed pressurized water reactor (PWR) nuclear plants, the WOG prepared Engineering Report V-EC-1658, " Risk Ranking Approach

' for Motor-Operated Valves in Response to Generic Letter 96-05." On. April 14,1998, the NRC staff issued a safety evaluation accepting with certain conditions and limitations the WOG approach for ranking MOVs based on their risk significance. Licensees not applicable to the j

BWROG or WOG methodologies need to justify their MOV risk-ranking approach individually,

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The objectives of the JOG dynamic test program are to determine degradation trends in dynamic thrust and torque, and to use dynamic test results to adjust the test frequency and method specified in the interim program if warranted. The JOG dynamic test program includes (1) identification of conditions and features which could potentially lead to MOV degradation, (2) definition and assignment of valves for dynamic testing, (3) testing valves three times over a 5-year interval with at least a 1-year interval between valve-specific tests according to a standard test specification, (4) evaluation of results of each test, and (5) evaluation of collective test results.

In the last phase of its program, the JOG will evaluate the test results to validate the assumptions in the interim program to establish a long-term MOV periodic verification program to be implemented by licensees. A feedback mechanism will be established to ensure timely sharing of MOV test results among licensees and to prompt individual licensees to adjust their own MOV periodic verification program, as appropriate.

j Following consideration of NRC staff comments, on July 30,1997, the BWROG submitted Licensing Topical Report NEDC-32719 (Revision 2) describing the JOG program. Similarly, the CEOG and the WOG submitted Topical Report MPR-1807 (Revision 2) describing the JOG program on August 6 and 12,1997, respectively. On October 30,1997, the NRC staff issued a safety evaluation to the BWROG, CEOG and WOG accepting the JOG program with certain conditions and limitations as an acceptable industry-wide response to GL 96-05 for valve age-related degradation.

4.0 TMI-1 GL 96-05 PROGRAM On November 15,1996, GPU Nuclear, Inc., submitted a 60-day response to GL 96-05 notifying the NRC that it intended to complete the actions requested by GL 96-05 for MOVs within the scope of the GL 89-10 program at TMI-1. On March 18,1997, the licensee submitted a 180-day response to GL 96-05 providing a summary description of the MOV periodic j

verification program planned to be implemented at TMI-1. In a submittal dated May 13,1998, the licensee updated its commitment to GL 96-05. On January 21,1999, the licensee provided a response to a request for additional information regarding GL 96-05 forwarded by the NRC staff on November 5,1998.

In its letter dated May 13,1998, the licensee stated that it plans to continue participating in the JOG Program on MOV Periodic Verification as described in Topical Report NEDC-32719 (Revision 2) in accordance with the applicable NRC safety evaluation. In its letter dated March 18,1997, the licensee described the implementation of the JOG program at TMI-1.

Although TMI-1 is a PWR nuclear plant designed by Babcock & Wilcox (B&W), the licensee stated that it is participating in the JOG program as a member of the BWROG (through its ownership of a separate BWR nuclear plant). With respect to its interim MOV static diagnostic test program, the licensee indicated that it had applied the BWROG methodology for ranking MOVs based on their safety significance as described in BWROG Topical Report NEDC-32264.

The licensee stated that it would modify the static test frequency for its GL 96-05 MOVs to the JOG interim test matrix starting with the Cycle 12 Refueling Outage (which was scheduled to i

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. begin in September 1997).. In a telephone _ conference on March 11,1999, the licensee indicated to the NRC staff that the JOG program is underway at TMI-1.

5.0 NRC STAFF EVALUATION The NRC staff has reviewed the information provided in the licensee's submittals describing the program to verify periodically the design-basis capability of safety-related MOVs at TMI-1 in response to GL 96-05. The staff also reviewed NRC Inspection Report (IR) 50-289/97-07 (dated July 23,1997) which provided the results of an inspection to evaluate the completion of the licensee's program to verify the design-basis capability of safety-related MOVs in response l'

to GL 89-10. The NRC staff closed the review of the GL 89-10 program at TMl-1 based on -

IR 97-07.and a June 17,1997, letter from the licensee. The NRC staff's evaluation of the '

licensee's response to GL 96-05 is described below.

5.1 MOV Program Scope

'In GL 96-05, the NRC staff indicated that all safety-related MOVs covered by the GL 89-10 j

program should be considered in the development of the MOV periodic verification program.

- The NRC staff noted that the program should also consider safety-related MOVs that ' re

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a assumed to be capable of returning to their safety position when placed in a position that l

prevents their safety system (or train) from performing its safety function; and the system (or i

train) is not declared inoperable when the MOVs are in their nonsafety position. In IR 97-07, the NRC staff found that the licensee's GL 89-10 program scope at TMI-1 was acceptable. In its letter dated November 15,1996, the licensee stated that the actions requested by GL 96-05 would be completed at TMI-1. In its letter dated March 18,1997, the licensee indicated that all MOVs in its GL 89-10 program would be included in the JOG periodic verification program at TMl-1.

The NRC staff considers the licensee to have made adequate commitments regarding the scope of its MOV program under GL 96-05.

5.2 MOV Assumptions and Methodologies

- The NRC staff expects licensees to maintain the assumptions and methodologies used in the development of its MOV programs for the life of the plant (a concept commonly described as a "living program"). - For example, the design basis of safety-related MOVs will need to be

- maintained up to date, including consideration of any plant modifications or power uprate conditions.-

In IR 97-07, the NRC staff reviewed the licensee's justification for the assumptions and methodologies used in the MOV program in response to GL 89-10 at TMI-1. With certain long-term items discussed in the following section, the staff determined that the licensee had

- adequately justified the assumptions and methodologies used in its MOV program. In its letter l

- dated January 21,1999, the licensee discussed ongoing activities to update its MOV program as necessary based on its evaluation of recent MOV information. The NRC staff considers the licensee to have adequate processes in place to maintain the assumptions and methodologies used in its MOV program.

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5.3' GL 89-10 Long-Term items When closing the NRC review of the GL 89d0 program at TMI-1, the NRC staff noted in l

IR 97-07 that the licensee had established plans for resolving several issues as described in its letter dated June 17,1997. These plans included modifications to provide additional margin in the capability of several MOVs to perform their design-basis functions. The licensee had l

previously described several action items regarding its MOV program in a letter to the NRC dated August 5,1996. In a letter dated December 31,1997, the licensee notified the NRC that it had completed the items specified in its earlier letter dated June 17,1997, with the exception of certain recommendations from the licensee's MOV Independent Review Team. In its letter l

dated January 21,1999, the licensee reported that those broad-based recommendations had been completedf The NRC staff prepared a safety evaluation dated January 22,1998, completing the NRC's review of the licensee's actions in response to GL 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves."

In IR 97-07, the NRC staff found that the licensee had established an adequate MOV trending program as recommended in GL 89-10 for the engineering and maintenance organizations. In its letter dated June 17,1997, the licensee indicated that, in addition to its other trending i

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. activities, it would revise its maintenance procedures to ensure that any work on valve internals would be evaluated for any potential effect on stem thrust requirements with appropriate consideration of the need for post-maintenance dynamic testing. In its letter dated January 21, 1999, the licensee indicated it would perform additional qualitative and quantitative trending including periodic MOV static diagnostic testing and preventive maintenance activities, such as periodic stem lubrication, actuator gearcase grease inspection, and actuator refurbishment.

. In IR 97-07, the NRC staff concluded that, with actions planned in the licensee's letter dated June 17,1997, the licensee had demonstrated the design-basis capability of the safety-related MOVs at TMI-1 Based on the licensee's submittals and discussions, the NRC staff considers the completed and ongoing long-term GL 89-10 actions at TMI-1 to be acceptable.

5.4 JOG Program on MOV Periodic Verification l

1 In its letter dated May 13,1998, the licensee updated its commitment to implement the JOG Program on MOV Periodic Verification as described in Topical Report NEDC-32719 I

(Revision 2) in accordance with the NRC safety evaluation dated October 30,1997. The licensee's commitment to implement the JOG program includes (1) the JOG interim static diagnostic test program, (2) the JOG 5-year dynamic test program, and (3) the JOG long-term periodic test program. The NRC staff considers the commitments by the licensee to implement

' the JOG program at TMI-1 to be an acceptable response to GL 96-05 for valve age-related

' degradation. Where the licensee proposes to implement an approach at TMI-1 different from the JOG program, the licensee will be expected to notify the NRC and to provide justification for the proposed attemative approach.

in its letter dated March 18,1997, the licensee stated that its interim MOV static diagnostic test program is consistent with the JOG program with the test frequency based on MOV safety significance and performance margin. The licensee ranked its MOVs using the methodology l

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. described in BWROG Topical Report NEDC-32264. In its letter dated January 21,1999, the licensee further described the ranking of the TMI-1 MOVs according to their importance to safety using engineering judgement (Expert Panel) and the TMl-1 Probabilistic Risk Assessment (PRA) Levels 1 and 2. The licensee indicated that the TMl-1 MOVs were ranked by Fussel-Vesely importance (FVI) with Risk Achievement Worth (RAW) used to provide additional insights to help the Expert Panel focus on MOVs having low FVI and high RAW values. The licensee also performed a sensitivity study by setting all MOVs at a high failure rate which resulted in some MOVs being re-categorized from low to medium risk categories.

The licensee reported that the Expert Panel ranked the applicable MOVs not modeled in the PRA. Further, the Expert Panel reviewed the PRA ranking results and re-categorized seven MOVs from low to medium risk categories. The licensee compared the MOV risk rankings at TMI-1 to other B&W plants to provide additional confidence in the reliability of the TMI-1 MOV risk-ranking methodology. In the telephone conference on March 11,1999, the licensee described specific aspects of MOV risk rankings at TMI-1 and their bases. The NRC staff considers the licensee's methodology for risk ranking of MOVs at TMI-1 to be acceptable.

The JOG program is intended to address most gate, globe, and butterfly valves used in safety-related applications in the nuclear power plants of participating licensees. The JOG indicates that each licensee is responsible for addressing any MOVs outside the scope of applicability of the JOG program. In the NRC's safety evaluation dated October 30,1997, the NRC staff specified that licensees implementing the JOG program must determine any MOVs outside the scope of the JOG program (including service conditions) and justify a separate program for periodic verification of the design-basis capability of those MOVs. The NRC staff expects significant information to be obtained on the performance and potential degradation of safety-related MOVs during the interim static diagnostic test program and the JOG dynamic test program. As the test results are evaluated, the JOG might include or exclude additional MOVs with respect to the scope of its program. Although the test information from the MOVs in the JOG dynamic test program might not be adequate to establish a long-term periodic verification program for each MOV outside the scope of the JOG program, sufficient information should be obtained from the JOG dynamic test program to identify any immediate safety concem for potential valve age-related degradation during the interim period of the JOG program. Therefore, the NRC staff considers it acceptable for the licensee to apply its interim static diagnostic test program to GL 96-05 MOVs that might be found to be outside the scope of the JOG program with the feedback of information during the JOG dynamic test program.

Upon completion of the JOG dynamic test program and development of the JOG long-term MOV periodic verification criteria, the licensee will be expected to establish a long-term MOV periodic verification program for those MOVs outside the scope of the JOG program by applying information from the JOG program or additional dynamic tests, as necessary.

5.5 Motor Actuator Output The JOG program focuses on the potential age-related increase in the thrust or torque required l

to operate valves under their design-basis conditions. In the NRC's safety evaluation dated l

October 30,1997, on the JOG program, the NRC staff specified that licensees are l

responsible for addressing the thrust or torque delivered by the MOV motor actuator and its potential degradation. Although the JOG does not plan to evaluate degradation of motor

9 8-actuator output, significant information on the output of motor actuators will be obtained through the interim MOV static diagnostic test program and the JOG dynamic test program.

In its letter dated January 21,1999, the licensee stated that, in addressing the potential degradation of MOV actuator delivered thrust or torque, TMI-1 was undertaking the following actions: (1) periodic static diagnostic testing of MOVs to confirm MOV capability and proper control switch settings; (2) appropriate preventative maintenance activities such as periodic stem lubrication, actuator gearcase grease inspection, and actuator refurbishment to provide reasonable confidence of proper actuator performance; (3) as-found static test data sampling of MOVs spanning different valve types and environments to confirm degradation assumptions for stem friction coefficients; (4) application of appropriate margins to account for potential actuator degradations such as stem lubrication degradation, spring pack relaxation, and rate of loading (ROL); (5) use of a bounding ROL value from the Electric Power Research Institute (EPRI)

MOV Performance Prediction Methodology for all program MOVs (unless different values are appropriately justified); and (6) as-found test data collection for some MOV differential-pressure dynamic tests to monitor for degradation of dynamic friction factors. The NRC staff notes that several parameters can be obtained during MOV static and dynamic testing to help identify motor actuator output degradation when opening and closing the valve including, as applicable, capability margin, thrust and torque at control switch trip, stem friction coefficient, load sensitive behavior, and motor current. Further, plant-specific and JOG test information can provide support for the licensee's plan for monitoring MOV motor actuator output and its potential degradation. The licensee also stated that it would keep apprized of the latest information concerning MOV performance from varicus industry organizations.

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in its letter dated January 21,1999, the licensee stated that it had evaluated the capability of j

ac-powered MOVs in its MOV program in response to Limitorque Technical Update 98-01 and had confirmed that these MOVs remain capable of performing their design-basis functions. The licensee reported that it is applying the methodology developed by the Commonwealth Edison Company (Comed) where applicable or using the method described in Limitorque Technical j

Update 98-01. The licensee will be expected to incorporate any changes in the Comed methodology that might result from the Limitorque updated guidance. In Supplement 1 to 1

Technical Update 98-01, Limitorque noted that a future technical update would be issued to address de-powered MOV applications. In its January 21,1999, letter, the licensee stated that there are no de-powered MOVs in its MOV program.

The NRC staff considers the licensee to be establishing sufficient means to monitor MOV motor actuator output and its potential degradation.

6.0 CONCLUSION

On the basis of this evaluation, the NRC staff finds that the licensee has established an l

acceptable program to periodically verify the design-basis capability of the safety-related MOVs j

at TMI-1. Therefore, the staff concludes that the licensee has adequately addressed the actions requested in GL 96-05. The NRC staff may conduct inspections at TMI-1 to verify the implementation of the MOV periodic verification program is in accordance with the licensee's commitments; this NRC safety evaluation; and the NRC's safety evaluation dated October 30, 1997, on the JOG Program on MOV Periodic Verification.

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Principal Contributor: T. Scarbrough, NRR l

l Date: May 27, 1999

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