ML20210L866

Safety Evaluation Accepting License 60-day Response to GL 96-05, Periodic Verification of Design-Basis Capability of Safety-Related Movs

ML20210L866
Person / Time
Site:	Quad Cities
Issue date:	08/02/1999
From:	NRC (Affiliation Not Assigned)
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ML20210L839	List: ML20210L837 ML20210L866
References
GL-96-05, NUDOCS 9908100053
Download: ML20210L866 (9)

Text

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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2066M001

. . . . . ,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO LICENSEE'S RESPONSE TO GENERIC LETTER 96-05.

" PERIODIC VERIFICATION OF DESIGN-BASIS CAPABILITY OF SAFETY-RI LATED MOTOR-OPERATED VALVES" COMMONWEALTH EDISON COMPANY QUAD CITIES NUCLEAR POWER STATION. UNITS 1 AND 2 DOCKET NOS. 50-254 AND 50-265

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 engireering 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 cculd perform their safety functions under design-basis conditions.

Upon identification of the weaknesses in MOV performance, significant inductry 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 (SE) addresses the program developed by Commonwealth Edison Company (Comed, the licensee) to verify periodically the design-basis capability of safety-related MOVs at the Quad Cities Nuclear Power Station, Units 1 and 2.

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 Federal Regulations (10 CFR Part 50) states, in part, that structures, systems, and components ENCLOSURE 9908100053 990802 PDR ADOCK 05000254 P PDR

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

In response to concerns regarding MOV performance, 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 in!tially 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 89-10 program before plant startup or in accordance with the above schedule, whichever was later. 1

- 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 appropriate to assure l 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 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 severalindustry  !

and regulatory activities and programs related to maintaining long-term capability of safety- l related MOVs. For example, GL 96-05 discussed non-mandatory ASME Code Case OMN-1, 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 requiremene for MOV quarterly stroke-time testing with exercising l of safety-related MOVs at least once per operating cycle and periodic MOV diagnostic testing i l 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 l limitations. The NRC staff also noted in GL 96-05 that licensees remain bound by the i i

requirements in their code of record regarding MOV stroke-time testing, as supplemented by l relief requests approved by the NRC staff.

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

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 l l

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b. within 180 days from the date of GL 96-05, or upon notification to the NRC of completion of GL 89-10 (whichever is later), a written summary description of the l licensee's MOV periodic verification program. l The NRC staff is preparing an SE 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 capabi;ity of safety-related MOVs l (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 periodic verification program to obtain benefits from the sharing of information between licensees. The Joint Owners' Group (JOG) Program on MOV Periodic Verifica'. ion is described by BWROG in its Licensing Topical Report NEDC-32719, "BWR Owners' Group Program on Motor-Operated Valve (MOV) Periodic Verification," and described by WOG and CEOG in th separately submitted Topical Report MPR-1807, " Joint BWR, Westinghouse and Combustir Engineering Owners' Group Program on Motor Operated Valve (MOV) Periodic Verification.

The stated objectives of the JOG Program on MOV Perio<1ic Verification are (1) to provide an approach for licensees to use immediately in their GL 96-O' wograms, (2) to develop a basis for addressing the potential age-related increase in requireu :.1 rust 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 program 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 an SE dated February 27,1996, the NRC staff accepted the BWROG methodology for risk ranking MOVs in boiling water reactor nuclear plants with certain conditions and limitations. In the NRC SE (dsted 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

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J l Westinghouse-designed pressurized water reactor nuclear plants, WOG prepared Engineering l Report V-EC-1658, " Risk Ranking Approach for Motor-Operated Valves in Response to Generic l Letter 96-05." On April 14,1998, the NRC staff issued an SE accepting with certain conditions

! and limitations the WOG approach for ranking MOVs based on their risk significance.

Licensees not applicable to the BWROG or WOG methodologies need to justify their MOV risk-ranking approach individually.

The objectives of the JOG dynamic test program are to determine dsgradation 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 testing 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-yearinterval 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, 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.

. Following consideration of NRC staff comments, BWROG submitted Licensing Topical Report NEDC-32719 (Revision 2) describing the JOG program on July 30,1997. Similarly, CEOG and WOG submitted Topical Report MPR-1807 (Revision 2) describing the JOG program on l August 6 and 12,1997, respectively. On October 30,1997, the NRC staff issued an SE i 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 QUAD CITIES GL 96-05 PROGRAM i On November 13,1996, Comed submitted a 60-day response to GL 96-05 notifying the NRC i that it would implement the requested MOV periodic verification program. On March 15,1997, l the licensee submitted a 180-day response to GL 96-05 providing a summary description of the i MCV periodic verification program planned to be implemented at Quad Cities. In a letter dated August 24,1998, the licensee updated its commitment to GL 96-05. On April 12,1999, the licensee provided a response to a request for additional information regarding GL 96-05

- forwarded by the NRC staff on February 4,1999.

Ir; its submittal dated March 15,1997, the licensee described its MOV periodic verification program, including scope, existing and planned testing, capability margin, and implementation of the JOG program at Quad Cities. For example, the licensee will use the methodology l described in ASME Code Case OMN-1 for periodic verification of MOV design-basis capability, l The licensee also stated that dynamic testing of selected MOVs would be performed under its MOV periodic verification program. . In its submittal dated August 24,1998, the licensee

committed to continue its par 1icipation in the JOG program on MOV Periodic Verification as a member of the BWROG, and to implement the program elements described in the Topical-

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Report NEDC-32719 (Revision 2) describing the JOG program. The licensee also stated that it l would evaluate degradation for any safety-related MOVs not covered by the JOG program

'within the same time frame as the JOG program.

5.0 NRC STAFF EVALUATION The NRC staff has reviewed the information provided in the licensee's submittals describing the  !

l program to venfy periodically the design-basis capability of safety-related MOVs at Quad Cities in response to GL 96-05. NRC Inspection Report 50-254 & 265/96018 (IR 96018) provided the results of an inspection to evaluate the licensee's program to verify the design-basis capability )

t. of safety-related MOVs in response to GL 89-10. The staff closed the review of the GL 89-10 '

program in IR 96018 based on verification of the design-basis capability of safety-related MOVs

l. at Quad Cities. The NRC staff's evaluation of the licensee's response to GL 96-05 is described

! . below.

5.1 MOV Proaram Scope in GL 96-05, the NRC staff indicated that all safety-related MOVs covered by the GL 89-10 program should be considered in the development of the MOV periodic verification program.

l The staff noted that the program should consider safety-related MOVs that are assumed to be capable of retuming to their safety position when placed in a position that prevents their safety system (or train) from performing its safety function; and the system (or train) is not deciered inoperable when the MOVs are in their nonsafety position.

In IR 96018, the NRC staff reviewed the scope of the licensee's MOV program in response to GL 89-10 at Quad Cities and found that the licensee planned to remove several MOVs based on the following criteria: (1) lack of an active safety function; or (2) valve installed in an air duct

! system. The staff found that these scope changes were consistent with GL 89-10 and its

- supplements.

- In its letter dated November 13,1996, the licensee committed to implement the requested MOV

> periodic verification program at Quad Cities in response to GL 96-05 and did not take exception to the scope of the generic letter. The staff considers the licensee to have made adequate commitments regarding the scope of its MOV program. The licensee will be responsible for  ;

l Justifying any deviations from the recommended scope of GL 96-05 at Quad Cities.

5.2 MOV Assumptions and Methodoloaies '  !

! The NRC staff expects licensees to maintain the assumptions and methodologies used in the l f development of its MOV programs for the life of the plant (a concept commonly described as a l l- "living program"). For example, the design. basis of safety-related MOVs will need to be j maintained up to date, including consideration of any plant modificatbns or power uprate j conditions, in IR 96018, 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 Quad Cities. With certain long-term items discussed in the following section, the staff determined that the licensee had l-

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i-l adequatelyjustified the assumptions and methodologies used in its MOV program. IR 96018 and the licensee's letter dated April 12,1999, discussed ongoing activities, such as review of motor actuator output, to update MOV program assumptions and methodologies.

In its letter dated August 24,1998, the licensee described activities to support the basis for several MOV program assumptions. The licensee stated that, in some instances, MOV stems are lubricated between periodic verification tests which prevents the gathering of as-found test data for evaluating stem factor degradation. However, the licensee uses results from other as-left and as-found periodic verification tests to determine stem factor degradation for valves where as-found conditions were not obtained.. Further, the licensee stated that, if the valve  !

factor for a newly installed or overhauled MOV exceeds the grouping valve factor, a differential i pressure test for the applicable MOV will be accomplished within three refueling outages of the

_ l baseline differential pressure test regardless of apparent margin. '

The staff considers the licensee to have adequate processes in place to maintain the  ;

assumptions and methodologies used in its MOV program, including the design basis of its i safety-related MOVs.

' 5.3 GL 89-10 Lona-Term items When evaluating the GL 89-10 program at Quad Cities, the NRC staff discussed in IR 96018 several items of the licensee's MOV program to be addressed over the long term. In its letter dated April 12,1999, the licensee reported on the status of those long-term GL 89-10 items.

For example, the licensee completed margin improvement actions for several low margin MOVs. Additional margin improvement efforts are planned for upcoming refueling outages.

The licensee continues to monitor industry sources, including the JOG MOV dynamic test i program, for additional information needed to justify valve factors for Anchor / Darling double-disc gate valves that must operate under high temperature conditions, and for large Crane flex-wedge gate valves that are currently set-up based on best available data provided by the i Electric Power Research Institute MOV Performance Prediction Methodology. The licensee revised its MOV program to address load sensitive behavior effects in the open direction. The licensee's program documents were. revised to specify a review of current MOV switch settings -

if thrust windows are revised.

The NRC staff completed the review of the licensee's actions in response to GL 95-07, j 1" Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," in an SE dated November 20,1998. 1 in IR 96018, the NRC staff summarized its review of the qualitative and quantitative aspects of the licensee's program for trending MOV performance at Quad Cities. For example, the licensee maintains databases of major and minor failures, baseline diagnostic test results, and MOV problems that have been identified from in-plant and industry sources. The licensee periodically evaluates available information to identify potential MOV failures before they occur, and to prevent repetition of previous MOV failures.

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In IR 96018, the NRC staff concluded that the licensee had demonstrated the design-basis

. capability of its safety-related MOVs at Quad Cities. With the licensee's ongoing MOV activities and trending program, no outstanding issues regarding the licensee's GL 89-10 program L remain at Quad Cities.

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! 5.4 JOG Prooram on MOV Periodic Verification l In its letter dated August 24,1998, the licensee updated its commitment to implement the JOG l Program on MOV Periodic Verification as described in Topical Report MPR-1807 (Revision 2).

l The licensee's commitment to implement the JOG program includes (1) the JOG interim static l

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 licensee's commitment to include all three phases of the JOG program and that the licensee is responsible for reviewing and implementing the limitations and conditions discussed in the NRC's SE dated October 30,1997, in applying the JOG program. This includes coordinating and feeding back test information j obtained from the JOG dynamic testing program. The staff considers the commitments by the licensee to implement the JOG program at Quad Cities to be an acceptable response to GL 96-05 for valve age-related degradation. If the licensee proposes to implement an approach at Quad Cities different from the JOG program, the licensee will be expected to notify j the NRC and to provide justification for the proposed attemative approach.

In its letter dated March 15,1997, the licensee noted that interim MOV static diagnostic testing

under the JOG program would be performed on a test frequency based on the safety

[ significance and available margin of each GL 96-05 MOV. The licensee indicated that the MOV ranking process at Quad Cities matched the approach presented in the BWROG Topical Report NEDC-32264. In its letter dated August 24,1998, the licensee indicated that margin requirements and static diagnostic test frequencies were consistent with the JOG -

l recommendations. The licensee is expected to address the conditions and limitations in the ,

1 NRC SE dated February 27,1996, which accepted Topical Report NEDC-32264, when J

! implementing the BWROG MOV risk-ranking methodology.

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The licensee's program at Quad Cities to verify periodically the design-basis capability of L  : safety-related MOVs will implement the provisions of ASME Code Case OMN-1 with certain L clarifications described in the licensee's March 15,1997, letter in response to GL 96-05. The licensee will use the OMN-1 methodology to satisfy GL 96-05, with clarifications such as (1) testing is scheduled according to the intervals specified in the JOG MOV program, (2) motor actuator torque capability of AC-powered MOVs is based on the Comed method previously accepted by the NRC staff, (3) the margin between MOV capability and operating requirements is based en stem thrust, (4) stem factor may be determined from stem thrust and measured  ;

torque or tested spring pack displacement, and (5) stem lubrication may be performed in some l instances between verification tests. In addition to OMN-1, the licensee will continue to perform stroke-time tests of MOVs in accordance with its IST program. As discussed in GL 96-05, the NRC staff considers it acceptable to apply ASME Code Case OMN-1 in verifying periodically

-_ the design-basis capability of safety-related MOVs. The licensee's MOV program satisfies the

. limitations regarding the use of ASME Code Case OMN-1 in meeting the intent of GL 96-05,  ;

- such as evaluating data over the first 5 years to support long test intervals. Based on the l

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. review of the licensee's GL 96-05 submittals, the staff considers the identified clarifications to OMN-1 to be justified.

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 I applicability of the JOG program. In the NRC SE dated October 30,1997, the NRC staff

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specifies 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 penodic verification of the design-basis capability of those MOVs. The NRC staff recognizes j that the JOG has selected a broad range of MOVs and conditions for the dynamic testing program. Consequently, 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. In its submittal dated August 24,1998, the

, licensee stated that it would evaluate valve degradation for any safety-related MOVs at Quad l Cities not covered by the JOG program within the same time frame as the JOG program. The 1 NRC staff considers it acceptable for the licensee to ' apply its interim static diagnostic test - i program to GL 96-05 MOVs that currently might be outside the scope of the JOG program with  !

the feedback of information from the JOG dynamic test program to those MOVs. Upon  !

completion of the JOG dynamic test program and development of the JOG long-term MOV -l periodic verification criteria, the licensee will be expected to establish a long-term MOV periodic l 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. I j

5.5 ' Motor Actuator Outout '

l The JOG program focuses on the potential age-related increase in the thrust or torque required i to operate valves under their design-basis conditions. In the NRC SE dated October 30,1997, on the JOG program, the NRC staff specifies that licensees are responsible for addressing the  !

thrust or torque delivered by the MOV mocor actuator and its potential degradation. Although  !

the JOG does not plan to evaluate degradation of motor actuator output, significant information on the output of motor actuators will be obtained through the interim MOV static diagnostic test L _ program and the JOG dynamic test program. j in its letter dated April 12,1999, the licensee indicated that it uses a combination of periodic static testing, preventative maintenance, and data analysis in accordance with established site procedures and programs to assure adequate actuator output capability for safety-related

- MOVs at Quad Cities to perform their design-basis functions. For example, the licensee performs preventative maintenance and inspections to minimize the degradation of MOV actuator output. The licensee's MOV periodic verification program includes evaluation of as-found and as-left static baseline test results to monitor stem lubricant degradation. The j:

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l licensee's setup method include margins for variations in stem factor, load sensitive behavior, and gearbox efficiency. 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.

In Technical Update 98-01 and its Supplement 1, Limitorque Corporation provided updated I guidince for predicting the torque output of its AC-powered motor actuators. As discussed in its letter dated April 12,1999, the licensee uses its own method for determining motor gearing capability for AC-powered motor actuators that is based on a comprehensive motor and actuator test program. As noted in NRC inspection reports, the NRC staff has accepted the use of the Comed methodology for estimating MOV motor-actuator output capability, based on test J l data obtained by the licensee. Comed will be expected to assess any changes in its methodology that might be necessary as a result of the Limitorque updated guidance.

l In its letter dated July 17,1998, forwarding Technical Update 98-01, Limitorque indicates that a future technical update will be issued to address the application of DC powered MOVs. In its letter dated April 12,1999, the licensee notes that the BWROG has initiated an effort to l evaluate DC-powered motor capability and that Quad Cities will incorporate the BWROG i DC-powered MOV methodology when completed.

The NRC staff considers the licensee has established sufficient means to monitor MOV motor j actuator output and its potential degradation.

6.0 CON'CLUSION On the basis of this evaluation, the staff finds that the licensee has established an acceptable program to verify periodically the design-basis capability of the safety-related MOVs at Quad l ' Cities. Therefore, the staff concludes that the licensee has adequately addressed the actions l_ requested in GL 96-05. T he staff may conduct inspections to verify the implementation of the MOV periodic verification program is in accordance with the licensee's commitments; this NRC SE; the NRC SE dated October 30,1997, on the JOG Program on MOV Periodic Verification; and the NRC SE dated February 27,1990, on the BWROG methodology for ranking MOVs by

. their safety significance. l Principal Contributor: T. Scarbrough, NRR i S. Tingen, NRR  ;

Date: August 2,1999 l