ML20206D695

Provides Update of Plans for VEGP MOV Periodic Verification Program Re GL 96-05, Periodic Verification of Design-Basis Capability of Safety-Related Movs

ML20206D695
Person / Time
Site:	Vogtle
Issue date:	04/28/1999
From:	Beasley J SOUTHERN NUCLEAR OPERATING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-96-05, GL-96-5, LCV-0904-D, LCV-904-D, NUDOCS 9905040204
Download: ML20206D695 (11)

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J. Bernie Beasley, Jr., P.E. ' Soutlwen Nuclear Vice President Operating Coenpany. lac..

Vogtle Project -

40 Inverness Center Parkway

' R0. Box 1295 Birmingharn. AlabamaiS201 l'

' Tel 205.992 7110 Fax 205 992.0403 SOUTHERN COMPANY Energy to Serve YourWorld"'

l April'28, '1999 LCV-0904-D Docket Nos. 50-424 50-425 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C,20555 1.adies and Gentlemen:

VOGTLE ELECTRIC GENERATING PLANT GENERIC LETTER 96-05 MOV PERIODIC VERIFICATION PROGRAM UPIET_E_.REGARDING JOG SUPPLEMENTAL SUBMITTAL The U. S. Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 96-05, " Periodic

'. Verification of Design Basis Capability of Safety-Related Motor-Operated Valves," on September 18,1996. As a response to GL 96-05, Southern Nuclear Operating Company (SNC) transmitted information to the NRC by letter LCV-0904-C, dated June 3,1998, describing

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' Vogtle Electric Generating Plant's (VEGP) intentions regarding the implementation of the Joint

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Owners Group (JOG) Program on motor-operated valve (MOV) Periodic Verification. This letter provides an update of SNC plans for the VEGP MOV periodic verification program. Also, NRC

' staff has indicated a need for more information on items related to the VEGP GL 96-05 program (this need was also discussed in the November 2,1998, teleconference with NRC in whien the p.g VEGP MOV program revisions were discussed). This lctter provides the response to the NRC

staff need fbr further information. The items and associated SNC responses are provided in the

- enclosure.

Should there be any questions in this regard, please contact this office.

Sincerely, 1

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Enclosure:

-VEGP MOV Program Information cc:

Southern Nuclear Operating Company Mr. J. T. Gasser Mr. M. Sheibani

. SNC Document Management U. S. Nuclear Regulatory Commission Mr. L.'A. Reyes, Regional Administrator Mr. R. R.' Assa, Project Manager, NRR I

Mr. J. Zeiler, Senior Resident Inspector, Vogtle i

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' ENCLOSURE -

VEGP MOV PROGRAM INFOR'MATION NRC REOUEST 1 in NRCInspection Report No. 50-424 & 425/97-04, the NRC stafclosed its review ofthe motor-operated valve (MOV) program implemented at Vogtle Electric Generating Plant (Vogtle) in response to Generic Letter (GL) 89-10, " Safety-Related Motor-Operated Yalve Testing and Surveillance. " In the inspection report, the NRC staffdiscussed certain aspects ofthe licensee 's MOVprogram to be addressed over the long term. For example, the inspectors noted that the licensee would (1) include an additional 5% bias margin to the target thrust settings qiall torque switch controlled rising-stem valves; (2) formally review the NRC's safety evaluation ofthe Electric Power Research Institute (EPRI) MO / Performance Prediction Model (PPM); (3) modify the Group AD-3 valves to increase their thrust output and review the thrust requirement:

to use more conservative assumptions; (4) increase the available marginsfor Group FG-1 valves; (5) revise the thrust requirementsfor Groups W-1A, W-2B,' and W-8 based on a review of available in-plant dynamic test data; (6) use industry test data or the EPRIMOYPPM tojustify I

the thrust requirementsfor valve Groups W-9, W-11, and W-12; (7) update its calculationsfor.

alllimit-switch-controlledMOVs with standard ACME threadstems to use a 0.18 stemfriction coeficient; and (8) dynamically test two 18" Fisher butterfly valves to ensure that all ofits 18" Fisher butterfly valves have adequate capability under design-basis conditions. The licensee should describe the actions taken to address the specific long-term aspects ofthe MOVprogram at Vogtle noted in the NRC inspection report.

SNC RESPONSE The above referenced eight aspects to be addressed long-term were identified as Issues No. I through 9, in letter LCV-0136-N, dated December 11,1997, Generic Letter 89-10 Close-Out

~ Inspection. The issues 1 through 9 also were addressed individually in the GL 89-10 closure in the NRC inspection report 50-424 & 425/98-06, dated September 10,1998. These issues were stated as resolved in the NRC inspection report, but additional considerations are described below where applicable.

Issues 1. 2. 3. 5. 6. 8. and 9: These issues were reviewed in the GL 89-10 close-out inspection and stated as resolved in the NRC inspection report. There are no additional follow-up actions that remain to be performed.

Issue 4: This issue was reviewed in the GL 89-10 close-out inspection and stated as.

resolved in the NRC inspection report and the additional actions remaining were noted in the discussion. Since that inspection report, the operators for valves 1HV-9380A and 1HV-9380B have been modified to provide additional opening margin in the recently completed Unit I refueling outage 1R8. This action completes this issue.

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o Issue 7i This issue was reviewed in the GL 89-10 close-out inspection and stated as resolved in the NRC inspection report. Follow-up actions that remained to be performed were the torque switch setting adjustments for vahes IHV-8716A and lHV-l 8804A to provide additional closing margin which were performed in IR8. The referenced adjustments for 2HV-8716A were performed in Unit 2 refueling outage 2R6.

This action completes this issue.

NRC REOUEST 2 In a letter datedJune 3,1998, the licensee updated its commitment to implement the Joint Owners Group'(JOG) Program on MOVPeriodic Verification in response to GL 96-05. The JOGprogram specifies that the methodology and discrimination criteriafor ranking MOVs

- according to their safety sigmficance are the responsibility ofeach participating licensee. The licensee stated in its letter that the Westinghouse Owners ' Group (WOG) methodologyfor ranking MOVs based on their safety sigmficance was being evaluatedfor use at Vogtle. Ifthe WOG MOV risk-ranking method as described in Engineering Report V-EC-1658-A (Revision 2, dated August 13,1998), " Risk Ranking Approachfor Motor-Operated Valves in Response to Generic Letter 96-05, " and the NRC safety evaluation dated April 14,1998, is not used, the l

licensee should describe the methodology usedfor risk ranking MOVs at Vogtle in more detail, including a description of(1) the process used to develop a sample list ofhigh-risk MOVsfrom other Westinghouseplants; and (2) how expertpanels were used to evaluate MOV risk sigmficance.

SNC RESPONSE In the June 3,1998 letter, VEGP stated that the intent is to prioritize valve test activities based on a combination ~of risk significance and deterministic considerations similar to the

' program described in the JOG topical report. In addition,it was stated that VEGP's objective is to adjust the static test frequency for individual MOVs to reflect the relative risk significance and available margin while continuing to provide adequate assurance that the MOV will be capable of performing its safety function. VEGP's active participation in the JOG dynamic test program was described, but it was stated that the static test program currently in place would continue to be utilized.

.VEGP intends to implement the Joint Owners Group (JOG) Program on MOV Periodic j

Verification and has determined that transition to the JOG interim static test program should be initiated. A factor in the transition is the VEGP probabilistic safety analysis (PSA) model which is currently being updated to incornorate recent changes in the VEGP plant and procedures. Additional revisions to the VEGP PSA are necessary to incorporate the specific WOG PSA methodology, and these additional revisions are planned for a subsequent

- update. Thus, VEGP will implement e two-step transition to the JOG progiam. The first step is a transition program which incorporates risk significance assessments and MOV margins. Depending on MOV risk significance and margin, some MOV test frequencies j

. may be' extended beyond five years but less than ten years. This transition approach will be 1

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lapplied to the 254 safety-related MOVs in the scope of the VEGP GLs 89-10 and 96-05 programs. The second step will be the final conversion to the MOV JOG program and will include the revised PSA model plus specific program revisions to align the VEGP MOV static testing program consistent with the JOG method.

- In response to NRC Item (1), above, a significant consideration in the assessment of safety significance of MOVs in the VEGP MOV testing program is the WOG list of typical MOVs of medium or high safety significance as stated in V-EC-1658-A, Risk Ranking Approach for Motor-Operated Valves in Response to Generic Letter 96-05, Revision 2. In most instances for VEGP, the applicable MOV assessment was consistent with the WOG list.

The differences with the WOG list are noted in Table 1, VEGP MOV Testing Program Differences, with the discussion of the basis for the difference provided with the MOV.

In response to NRC Item (2) above, in the transition program the risk significance assessments are determined using expert panel review which includes applying insights gained with respect to plant safety significance issues based on the current PSA. The MOV expert panel was selected with the membership including representatives from the maintenance, operations, engineering, and probabilistic safety analysis disciplinec. A majority of the panel membership had previous experience as. Maintenance Rule Expert Panel members which provided advance experience in detailed consideration of VEGP safety significance issues. The primary considerations in the expert panel's assessment of MOV safety significance are:

The applicable system safety significance per the VEGP probabilistic safety analysis model (PSA) and the contribution of the MOV to the achievement of the safety significant functions within the applicable system, Importance measures for the valves based on their active failure probabilities in the current VEGP PSA, using industry established threshold values for importance, The Westinghouse Owners Group (WOG) list of typical valves of high or medium safety

e-significance for Westinghouse plants, stated in V-EC-1658-A, Revision 2, and

. Significance for plant safety during shutdown operations.

The VEGP PSA used as a basis for the MOV program risk ranking safety significance is e

also used as the primary tool for risk assessment in the Maintenance Rule program.

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NRC REOUEST 3 The licensee 's updated commitment stated that Vogtle will continue to use its own MOVstatic diagnostic testprogram in lieu ofthe JOG interim MOVstatic diagnostic testprogram. The JOG MOV Periodic Verification Program consists of threephases: (1) the interim MOVstatic

- diagnostic testingprogram; (2) an MOVdynamic testingprogram over the next 5 years; and (3)

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the long-termperiodic testingprogram. The NRCstafconsiders a licensee's commitment to the JOdprogram to include all threephases unless otherwise specifled. Where a licensee that has l

committed to implement the JOGprogram proposes to implement a diferent approach, the licensee will be expected to notify the NRC and toprovidejustificationfor theproposed alternative approach. The licensee should clarify its commitment to the JOGprogram at Vogtle orjustify its interim static diagnostic testprogramfor those MOVs that will notfollow the JOG program recommendations.

SNC RESPONSE VEGP's intent is to implement the Joint Owners Group (JOG) Program on MOV Periodic Verification. The transition program is planned for implementation in 1999. VEGP plans for full conversion to the JOG interim static test program following completion of the necessary revisions to the VEGP PSA to incorporate the specific WOG PSA methodology.

Upon completion of the revisions to the VEGP PSA, a reevaluation of the risk ranking will be performed. -In addition to the targeted implementation of the interim MOV static diagnostic testing program, VEGP is an active participant in the MOV dynamic testing program with a significant portion of the valve dynamic tests assigned to VEGP completed.

The results from the JOG's comprehensive program for determining valve degradation issues will be closely monitored and reviewed for applicability to and incorporation in the

. VEGP MOV program.

The JOG methodology provides for MOV static testing frequency being determined in consideration of valve safety significance and MOV margins and in consideration of the additional elements provided in Jie NRC safety evaluations for the JOG documents:

MPR-1807, Joint BWR, Westinghouse and Combustion Engineering Owners' Group Program on Motor-Operated Valve (MOV) Periodic Verification VEGP transition approach, and, V-EC-1658-A, Risk Ranking Approach'for Motor-Operated Valves in Response to Generic Letter 96-05.

. The VEGP program for transition to the JOG program uses as its basis in determining valve

' test frequencies valve safety significance as determined by expert panel review, MOV margins, and elements provided in the above referenced NRC safety evaluations.

The' discussion in LCV-0904-C, dated June 3,1998, regarding VEGP's intentions for the MOV JOG static testing program is superseded by the revised intentions stated in this

- response to NRC Request 3.

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,. NRG REOUEST 4

' In a letter dated March 12,1997, the licensee stated that new diagnostic technologies that monitor MOVperformance at the motor control center (MCC) may be used, as appropriate. The licensee should briefly describe itsplansfor the use oftest datafrom the motor control center (MCC) including (1) correlation ofthe new MCC test data to existing directforce measurements; (2) interpretation ofchanges in MCC test data to changes in MOV thrust and torqueperformance; (3) consideration ofsystem accuracies andsensitivities to MOV

-degradationfor both output and operatingperformance requirements; and (4) validation of -

MOVoperability using MCC testing.

SNC RESPONSE In the March 12,1997 letter, LCV-0904-B, VEGP stated it has procured a Motor Power Monitor (MPM) test system from Liberty Technology and that the system was being evaluated for use at VEGP and may be integrated into the periodic verification program, as appropriate, based on each individual valve's relative risk significance and available margin.

To date, the MPM system has not been applied in the periodic verification program, therefore, the above requested data is not available. Evaluations continue on use of the system at VEGP, though no specific plans for application of the system in the periodic verification program have been developed. Answers to the above questions will be provided to the NRC prior to application of this methodology utilized at VEGP.

_N_RC REOUEST 5 i

The JOGprogramfocuses on thepotential age-related increase in the thmst or torque required

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to operate valves under their design-basis conditions. In the NRCsafety evaluation dated October 30,1997, on the JOGprogram, the NRC staffspecifled that licensees are responsible for addressing the thrust or torque delivered by the MOV motor actuator and its potential

~ degradation. The licensee should describe theplan at Vogtlefor ensuring adequate AC and DC MOV motor actuator output capability; including consideration ofrecent guidance in Limitorque Technical Update 98-01 and its Supplement 1.

SNC RESPONSE The VEGP MOV testing program provides for comprehensive review of test results, i

including review of motor actuator output (e.g. motor current and torque) and stem factor, This procedurally documented review is conducted to confirm acceptable results (e.g. torque and thrust delivered is above requirements), confirm continued operability of the valve, and assess trends of valve and actuator performance, including specific assessment of stem i

factor. The post-test comprehensive review ensures early detection of trends of valve j

performance degradation.-

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7 VEGP has addressed the issues contained in TU 98-01. The actuator output torque was re-

' evaluated using specific validated engineering data based on actual Commonwealth Edison Company and industry test data. The available motor torque and operator efficiency in the VEGP calculations were revised based on this validated engineering data. As a result of this change to the calculation, several valves had lowcr than desirable margin and modifications to the motor pinion gear ratio were recommended. These modifications have been completed. Reviews with respect to the 66:1 worm gear ratio were subsequently conducted after TU 98-01, Supplement 1, was received and no physical modifications are required for any of the 254 safety-related MOVs in the scope of the VEGP GLs 89-10 and 96-05 programs.

A significant element of the program providing for long-term monitoring for valve degradation is VEGP's participation in the MOV JOG dynamic valve testing program. The results from the JOG's comprehensive program for determining valve degradation issues will be closely monitored and reviewed for applicability to and incorporation in the VEGP MOV program.

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l TABLE 1 VOGTLE MOV TESTING PROGRAM DIFFERENCES ITEM FROM JOG GENERAL LIST OF TYPICAL MOVS OF MEDIUM BASIS FOR DIFFERENCES BETWEEN VEGP OR HIGH SAFETY SIGNIFICANCE ASSESSMENT AND WOG LIST 1

Refueling Water Storage Tank (RWST) to These MOVs were assessed as low safety significance for containment spray pump suction VEGP based on the PSA low importance of the containment spray (CS) system, which is low because of VEGP's large dry containment. Two additional considerations are:

Emergency procedure guidance requires that the CS pumps be stopped if the RWST Empty alarm energizes, and The close function to prevent,adioactive release through e

the RWST is redundant to closure of a check valve in the flow path.

I Containment sump to containment spray These MOVs were assessed as low safety significance for pump suction VEGP based on the PSA low importance of the CS system, which is low because of VEGP's large dry containment.

Residual Heat Removal (RHR) pump to One normally open MOV associated with this function was Centrifugal Charging (CC) pump and/or assessed as low safety significance for VEGP because this valve Safety Injection (SI) pump suction is maintained open and realignment is not required for Emergency Core Cooling System (ECCS) injection or recirculation. The other valves which are required to open to perform me nnaion are assessed as high safety significance.

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5 TABLE 1 VOGTLE MOV TESTING PROGRAM DIFFERENCES (continued)

ITEM FROM JOG GENERAL LIST OF TYPICAL MOVS OF MEDIUM BASIS FOP DIFFERENCES BETWEEN VEGP OR HIGH SAFETY SIGNIFICANCE ASSESSMENT AND WOG LIST SI pump miniflow recirculation These MOVs were assessed as low safety significance for VEGP based on the PSA low importance of the safety injection (intermediate head) subsystem of ECCS, which is low because of the redundancy of the centrifugal charging pumps (high head)

ECCS subsystem. Two additional considerations are:

• The MOVs are redundant isolation of the miniflow i

flowpath, and The close function to prevent radioactive release through the RWST is interlocked with the RHR pump to centrifugal charging pump and SI pump suction MOVs which provides assurar.ee the containment sump inventory will not be allowed into the RWST when the miniflow valves are open.

1 Service water to auxiliary feedwater These MOVs were assessed as low safety significance because (AFW) water source the VEGP has MOVs with this function only for the second, completely redundant condensate storage tank (CST). The AFW water source for each VEGP unit is two completely redundant CSTs. One is required operable by Technical Specifications to satisfy safety analysis assumptions, with the second being completely redundant and available to place into service if needed to support AFW. The suction flowpath for the CST normally aligned to support AFW pump start and injection into the steam generators only has a manual isolation valve.

The suction flowpath for the redundant CST is equipped with an MOV. Repositioning of the redundant CST MOVs is only required if the CST inventory injected by AFW exceeds safety analysis assumptions and it becomes necessary to place the second CSTin service.

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• VOGTLE MOV TESTING PROGRAM DIFFERENCES (continued) l ITEM FROM JOG GENERAL LIST l

OF TYPICAL MOVS OF MEDIUM BASIS FOR DIFFERENCES BETWEEN VEGP t

OR HIGH SAFETY SIGNITiCANCE ASSESSMENT AND WOG LIST Service water nonessential isolation The service water nonessential loads for VEGP that are isolated are the reactor cavity cooler and the auxiliary containment cooler. The MOVs that isolate these loads were assessed as low safety significance because the supply and return isolation for these nonessential loads are redundant with respect to termination of flow to nonessential loads. These nonessential loads are seismically qualified for the VEGP design basis seismic event and the service water pressure boundary in the I

nonessential loads is safety related.

Component cooling water nonessential This MOV function is not applicable to VEGP because there are isolation no MOVs with this function installed at VEGP.

Component cooling water to RHR heat This MOV function is not applicable to VEGP because there are exchangers no MOVs with this function installed at VEGP.

Containment spray pump discharge to These MOVs were assessed as low safety significance for spray headers VEGP based on the PSA low importance of the CS system, which is low because of VEGP's large dry containment.

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