ML20137C386
| ML20137C386 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 03/18/1997 |
| From: | Drawbridge B NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-89-10, GL-96-05, GL-96-5, NYN-97030, NUDOCS 9703240239 | |
| Download: ML20137C386 (13) | |
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Nerth North Atlantic Energy Service Corporation P.O. Box 300
)I Atlaritic seahreet. sii o3874 (603) 474-9521 The Northeast Utilities System March 18,1997 Docket No. 50-443 NYN-97030 l
I United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Seabrook Station 180-Dav Resoonse to Generic Letter 96-05 North Atlantic Energy Service Corporation (North Atlantic) provides herein the 180-day response to !
Generic Letter (GL) 96-05, " Periodic Verification of Design-Basis Capability of Safety Related Motor .
Operated Valves". North Atlantic committed in the 60-day response to GL 96-05, dated November 15, i 1996, to establish a program to verify, on a periodic basis, that the GL 89-10 MOVs will continue to be ;
capable of performing their design function within the current licensing basis.
l Attached is North Atlantic's 180-day response to GL 96-05. The response contains a summary description of the Motor Operated Valve Periodic Verification Program. The summary describes both the existing GL 89-10 MOV Periodic Verification Program and the GL 96-05 MOV Periodic Verification Program, i Should you have any questions regarding this response, please contact Mr. Terry L. Harpster, Director of Licensing Services, at (603) 773-7765.
Very truly yours, NORTH 'nNTIC ENERG SERVICE CORP. i
_ m / fo *b c'e L. D8wbridge Director-Service i
cc: Hubert J. Miller, Region I Administrator if
_ Mr. Albert W. De Agazio, Sr. Project Manager Mr. John B. Macdonald, NRC Senior Resident inspector AO3 / '
9703240239 970310 g '
PDR ADOCK0500g3 appsppas.u.4 :
i STATE OF NEW 11AMPSHIRE Rockingham, ss. March I8,1996 Then personally appeared before me, the above-named Bruce L. Drawbridge, Director-Services,
-North Atlantic Energy Service Corporation that he is duly authorized to execute and file the foregoing information in the name and on the behalf of North Atlantic Energy Service Corporation and that the statements therein are true to the best of his knowledge and belief.
Susan J. MekNotary Public ,
My Commission Expires: December 22,1998
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EXECUTIVE
SUMMARY
Generic Letter (GL) 89-10," Safety Related Motor-Operated Valve Testing and Surveillance," was issued on June 28, 1989. Recommendation (d) of GL 89-10, requested licensees to prepare procedures to ensure that correct MOV switch settings are maintained throughout the life of the plant. In addition, Recommendation (j) stated that licensees should periodically verify MOV capability every 5 years or 3 refueling outages. In response to Recommendations (d) and (j), North Atlantic Energy Serv..,:
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Corporation (North Atlantic) developed the Motor-Operated Valve Periodic Verification Program. North Atlantic initially identified and completed baseline diagnostic testing on 118 MOVs during Refueling Outages (RF) 01-03. Initial baseline testing was the first phase of the GL 89-10 MOV Program. Upon i completion of the baseline testing, the 118 identified GL 89-10 MOVs were scheduled for the second !
phase of the GL 89-10 MOV Program, periodic testing. In RF 04, Nonh Atlantic completed the first i cycle of periodic verification testing. The second cycle of MOV periodic verification testing will be I
performed in RF 05, scheduled to commence on May 10,1997. ;
Generic Letter 96-05, " Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves" was issued on September 18,1996. Although similar to GL 89-10 and its supplements with respect to guidance regarding periodic verification, GL 96-05 provides more complete guidance for establishing a periodic verification program. GL 96-05 supersedes GL 89-10 and its supplements with regard to MOV periodic verification. GL 96-05 required utilities to submit a 60-day response to commit to the development of a verification program that meets the actions identified in GL 96-05. North Atlantic provided the 60-day GL 96-05 response on November 15,1996. GL 96-05 also required that within 180-days from the date of GL 96-05 (September 18, 1996) that licensees submit a written summary description of the MOV periodic verification program established in accordance with the requirements identified in GL 96-05. The enclosed report is Nonh Atlantic's 180-day response to GL 96-05.
North Atlantic is a participant in the Joint BWR and Westinghouse Owner's Group (JOG) Program on Motor-Operated Valves Periodic Verification. The description of the JOG program is included in MPR-1807 and was transmitted to the NRC on March 3,1997 under Westinghouse Owners Group Letter No.
OG-97-018. As described in MPR-1807, the frequency of MOV periodic verification is determined on the valve's safety risk significance and the valve setup margin. North Atlantic plans to use the same risk and margin threshold values to determine MOV periodic verification frequencies. Attachment # 1 to this letter provides the JOG " Interim" Utility Program Verification Matrix that shows the relationship between valve safety risk significance and valve setup margin. The risk ranking of all GL 96-05 MOVs has initially been determined using an approach similar to the BWR Owners Group Risk Ranking Methodology. The risk ranking of all GL 96-05 MOVs will be further assessed using the Expert Panel concept that was initiated for the Maintenance Rule. It is anticipated that the Expert Panel's review of the GL 96-05 will be completed by the end of 1997.
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. Executive Summary (continued) i During RF 05, Nonh Atlantic anticipates statically testing 41 safety related MOVs using diagnostic test equipment and dynamically testing 10 MOVs. Six MOVs xill be both statically and dynamically tested.
The testing perfonned during RF 05 will be integrated into the GL 96-05 MOV Periodic Verification '
Program. In addition, North Atlantic anticipates testing the 300 assigned MOVs under dynamic ,
i conditions to support the commitment to the JOG Periodic Verification Program.
1 l The testing results obtained during RF 05 will support North Atlantic's continuing commitment to the i GL 89-10 MOV P:ogram, and provide information that will be used in the GL 96-05 Periodic Verification Program. Thi: will be the point where North Atlantic will start the transition from the GL- ;
8910 MOV Verification Program to the GL 96-05 MOV Verification Program. The GL 96-05 MOV i Periodic Verification Program will be fully implemented for the start of RF 06.
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ENCLOSURE TO NYN-97030 i
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North Atlantic Response to USNRC Generic Letter 96-05
" Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves" Purpose The purpose of this letter is to provide the North Atlantic Energy Service Corporation (North Atlantic) 180 day response to USNRC Generic Letter 96-05," Periodic Verification of Design- l Basis Capability of Safety-Related Motor-Operated Valves (MOVs)". This response provides the written summary descriptions of the Forth Atlantic Motor-Operated Valve Periodic l Verification Program. Summary descriptions of both the existing Generic Letter 89-10 MOV Periodic Verification Program and the Generic Letter 96-05 MOV Periodic Verification Program are provided. This letter also describes MOV periodic verification activities that are planned for Seabrook Station's fifth Refueling Outage which is currently scheduled to commente on May 10,1997.
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Background
USNRC Generic Letter (GL) 89-10, " Safety-Related Motor-Operated Valve Testing and Surveillance", was issued on June 28, 1989. GL 89-10 was issued because the USNRC recognized that nuclear power plant operating experience, salve performance problems and .
MOV research revealed that the focus of ASME stroke time and leak rate testing for MOVs was !
not sufficient in light of the design of the valves and the conditions under which the MOVs I function. GL 89-10 recommended that each licensed nuclear power plant establish a program to demonstrate that safety-related MOVs are capable of performing their design basis function (s).
The USNRC staff requested that licensees and 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. GL 89-10, Recommendation (d) requested licensees prepare procedures to ensure that correct MOV switch settings are maintained throughout the life of the plant. GL 89-10 stated that it may become necessary to adjust MOV switch settings because of wear or aging and that additional measures beyond stroke time testing should be taken to adequately verify that the switch settings ensure MOV operability. GL 89-10, Recommendation (j) stated that licensees should periodically verify MOV capability every 5 years or 3 refueling outages.
Discussion USNRC Generic Letter 96-05 was issued on September 18, 1996. This GL provides more complete guidance regarding periodic verification of safety-related MOVs and supersedes GL 89-10 and its supplements with regard to MOV periodic verification. Generic Letter 96-05
_ requested that licensees take the following actions:
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' Requested Action ;
i Each addressee of this generic letter is requested to establish a program, or to ensure the i effectiveness ofits 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 l l of the facility. The program should ensure that changes in required performance resulting from degradation (such as those caused by age) can be properly identified and accounted for.
. Addressees that have developed periodic verification programs in response to Generic Letter ;
L 89-10 should review those programs to determine whether any changes are appropriate in j
! light of the information in this generic letter. ;
I I Required Response -!
Within 180 days from the date of this generic letter, or upon notification to NRC of i completion of GL 89-10 (whichever is later), the addressee shall submit a written summary l L
description of its MOV periodic verification program established in accordance with the
- Requested Actions paragraph.
t North Atlantic notified the N_RC ofits completion of GL 89-10 on January 15,1996, thus the !
required response is to be submitted within 180 days of the date of the generic letter.
L Summary Description of the North Atlantic MotooOperated Valve Periodic Verification Program l i i
- l. 1.0 Scope l
I The North Atlantic MOV periodic verification program established to meet the recommendations ' ;
i of USNRC Generic Letter 96-05," Periodic Verification of Design-Basis Capability of Safety- l Related Motor-Operated Valves" consists of the same motor-operated valve population that is in !
the scope of the GL 89-10 MOV Program. This includes the safety-related motor-operated valves that are assumed capable of returning to their safety position when placed in a position
! - that prevents their safety system from performing its safety function when the system is not declared inoperable when the MOVs are in their non-safety position. This last criteria includes i those MOVs that may be placed in their non-safety position during surveillance testing and are
! assumed to be operable in that position. Presently, there are 114 safety-related MOVs in North i Atlantic's GL 89-10 Program. As part of the Generic Letter 89-10 Program, North Atlantic j intends to remove valves from the program that were originally included solely due to valve mispositioning. Therefore, due to this and other factors the scope of valves in the GL 96-05 periodic verification program may change in the future. Any changes to the program, either additions or subtractions, will be justified by 10 CFR 50.59 evaluations.
L 2.0 - Summary of Current GL 89 10 Periodic Verification Program
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2.1 - Existing GL 89-10 MOV Periodic Verification Test Program -
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In accordance with Recommendation (j) of Generic Letter 89-10, North Atlantic is performing
- ' periodic verification diagnostic testing of safety-related MOVs on a three reseling outage l
[ frequency. North Atlantic had plans to modify the periodic testing frequency using a !
deterministic approach which would factor in specific valve setup or valve operating parameters l
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l and include results of the North Atlantic specific PRA evaluation of the valve's safety risk significance. North Atlantic completed baseline diagnostic testing on the 118 MOVs initially in the Generic Letter 89-10 program during Refueling Outages (RF) 01-03. RF 04 was the l beginning of the periodic verification sequence for motor-operated valves (collection of the second set of test data for approximately one-third of the GL 89-10 valves). North Atlantic's
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long term periodic verification program was based both on static testing of all valves and limited dynamic testing of selected valves performed to assure the adequacy of the static test program.
As identified in NRC inspection Report 96-011 dated 3/7/97, to support North Atlantic's stem coefficient of friction assumption, fifteen additional dynamic tests are scheduled to be performed during RF 05 and 06.
North Atlantic typically uses static diagnostic testing to fulfill the periodic verification commitment to GL 89-10. Test acceptance criteria have been established to demonstrate that motor-operated valve operational readiness under design basis conditions is maintained. Valve operability is determined based on the test results meeting the acceptance criteria. The acceptance criteria have been established using conservative thrust values and will be updated to account for rate ofloading which will account for differences between static and dynamic thrust requirements. The thrust acceptance criteria includes margin for change of the packing load and accounts for torque switch repeatability and diagnostic test equipment inaccuracy. Based on the results of the as-left test, new operational margin values are determined.
North Atlantic performs dynamic testing of safety-related MOVs in accordance with differential l
pressure test procedures. Testing is typically performed under maximum achievable differential '
pressure conditions. Following testing, the test results are extrapolated to design basis conditions and adjusted to account for instrument inaccuracies. Dynamic test margin is then calculated. The test results are then evaluated to assure that valve operability is maintained prior to declaring the valve operable. Actual Rate of Loading is accounted for in the dynamic test evaluation.
2.2 Refueling Outage 05 MOV Periodic Verification RF 05 is currently scheduled to commence on May 10,1997. Scheduled MOV diagnostic testing during RF 05 consists of both static and dynamic testing as part of North Atlantic's Generic Letter 89-10 MOV Program. The testing conducted in RF 05 will be the second cycle of periodic verification testing for the GL 89-10 MOVs. North Atlantic anticipates statically testing 41 safety related MOVs using diagnostic test equipment and dynamically testing 10 MOVs. Six MOVs will be both statically and dynamically t'sted. The dynamic test results are extrapolated to design basis differential pressure conditions and are adjusted to account for instrument inaccuracies. Dynamic test margin is then calculated. The test results are then evaluated to assure that valve operability is maintained prior to declaring the valve operable. The testing i performed during RF 05 will be integrated into the GL 96-05 MOV Periodic Verification Program Credit for testing will be taken when test frequencies are identified as part of the GL 96-05 MOV Periodic Verification Program.
Additional diagnostic testing will be perfermed, if required, following corrective maintenance, in accordance with the Post Maintenance Test Guidelines. This requirement meets established policies for the GL 89-10 MOVs.
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- l North Atlantic anticipates testing the Joint Owners Group (JOG) assigned motor-operated valves under dynamic conditions to support the JOG Periodic Verification Program. It is anticipated ,
that North Atlantic will be assigned two valves and will be required to perform three dynamic i tests over a five year period as part of the JOG Periodic Verification Program.
2.3 Generic Letter 89-10 Margin Detennination 2.3.1 Margin for Gate and Globe Valves 2.3.1.1 Based on Static Testing l For valves that close using torque switch control, close margin is determined by taking the as tested static thrust value at torque switch trip and accounting for diagnostic test equipment ]
instrument inaccuracies, torque switch repeatability, and subtracting the calculated required I thrust for close operation. The calculated, required thrust for close operation includes a factor for rate ofloading.
l For valves that close under limit switch control, close margin is determined by subtracting the !
- calculated required thrust from the actuator derated thrust output capability.
Open margin is determined similar to close margin for valves that close using limit switch control. Open margin is determined by subtracting the calculated required thrust from the 3 actuator derated thrust output capability. !
2.3.1.2 Based on Dynamic Testing For valves that close using torque switch control, close margin is determined by taking the difference between the thrust value at torque switch trip and the extrapolated thrust value at either hard seat contact or prior to hard seat contact (if greater). Appropriate adjustments to margin are made for diagnostic test equipment inaccuracy, differential pressure and line pressure instrumentation uncertainties and torque switch repeatability. Rate of Loading is included in the margin determination by using the lesser of the thrust at torque switch trip from static test results or the dynamic test.
For valves that close under limit switch control, close margin is determined taking the difference between the actuator derated thrust output capability and the accuracy adjusted (higher),
extrapolated thrust. Appropriate adjustments to margin are made for diagnostic test equipment inaccuracy, differential pressure and line pressure instrumentation uncertainties.
Open margin is determined similar to close margin for valves that close using limit switch control. Open margin is determined taking the difference between the actuator derated thrust output capability and the accuracy adjusted, (higher), extrapolated thrust.
2.3.2 Margin for Butterfly Valves 2.3.2.1 Based on Static Testing Open and close margin for balanced disk butterfly valves is determined by the difference between the calculated actuator output capability at the torque switch trip setpoint, adjusted for 4
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torque switch repeatability, and a calculated dynamic peak torque value. Dynamic testing performed on Fisher 24" balanced disk butterfly valves installed in the Service Water (SW) system demonstrated that the peak torque is not proportional to the differential pressure at time of flow initiation or flow cutoff. The peak static torque is used to calculate a peak dynamic torque based on the ratio of peak static torque to peak dynamic torque for tested butterfly valves.
All non-balanced disk butterfly valves have been dynamically tested.
2.3.2.2 Based on Dynamic Testing Open and close margin for balanced disk butterfly valves is determined by the difference between the calculated actuator capability at the torque switch trip setpoint, adjusted for torque switch repeatability, and the dynamic peak torque value. The dynamic peak torque value was adjusted for the difference between actual test conditions and design conditions and reduced by an instrument uncertainty value. Based on the testing referenced in 2.3.2.1 above, peak torque's for valves tested at less than design conditions are scaled based on the ratio of peak static torque to peak dynamic torque for tested butterfly valves.
Open and close margin for non-balanced disk butterfly valves is determined by the difference between the calculated actuator capability at the torque switch trip setpoint, adjusted for torque switch repeatability, and the dynamic peak torque extrapolated to design conditions and reduced by an instrument uncerta.nty value.
3.0 Generic Letter 96-05 Periodic Verification Program 3.1 Joint Owners Group MOV Periodic Verification Program North Atlantic is a participant in the Joint BWR and Westinghouse Owner's Group (JOG)
Program on Motor-Operated Valves Periodic Verification. The description of this program is included in MPR-1807. Revision 0," Joint BWR and Westinghouse Owners' Group Program on Motor-Operated Valve (MOV) Periodic Verification" which was transmitted to the USNRC under Westinghouse Owners Group Letter No. OG-97-018 dated March 3,1997.
North Atlantic plans to transition into full implementation of the JOG Periodic Verification Program by the start of the sixth refueling outage, which is tentatively scheduled for the Fall of 1998. As discussed above, during the fifth refueling outage, which starts in May of 1997, existing scheduled periodic verification testing to meet USNRC GL 89-10 commitments will continue. The long term GL 96-05, MOV Periodic Verification Program (Refueling Outage 06 and beyond) description is summarized below. As described in MPR-1807, the frequency of MOV periodic verification is determined based on the valve's safety risk significance and the valve's setup margin. North Atlantic plans to use the same risk and margin threshold values identified in MPR-1807 to determine MOV periodic verification testing frequencies. North Atlantic will perform additional dynamic testing to justify the assumed stem / stem-nut friction coefficient during Refueling Outage 06.
In addition to static testing, as part of the GL 96-05 Program, limited dynamic testing on selected valves may be performed to assure the adequacy of the required thrust / torque values established in the applicable calculations. Following completion of the dynamic tests, the data will be 5
immediately reviewed for valve operability considerations. Test results will be reviewed to determine any generic impact on similar valves in the dynamic test group. Any detrimental impact identified will be applied to all valves in the test group if warranted.
Summary descriptions of North Atlantic's Risk Ranking Methodology and Margin Determination are provided below.
3.2 North Atlantic Risk Ranking Methodology In support of periodic testing of MOVs, North Atlantic conducted an evaluation of the risk !
significance of each MOV. The MOV risk ranking was developed based on a methodology that ;
is similar to the BWR Owners Group MOV Risk Ranking Methodology, reference NEDC-32264-A, " Application of Probabilistic Safety Assessment to Generic Letter 89-10 Implementation" The intent of the PRA review was to support prioritization of Generic Letter l 89-10 testing. This review focused upon two items relative to MOV performance in light of Generic Letter 89-10 concerns.
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- 1. MOVs that are not required to be repositioned, and i
- 2. MOVs that must actuate (open/close) to perform their safety function.
With respect to the first item, a review of each MOV included in the GL 89-10 program was conducted. Those MOVs which were included within the MOV program solely on the basis of j the position changeable issue were determined to be oflow risk significance. This is consistent i with the work conducted by Brookhaven National Labs for the NRC in regards to PWRs. I With respect to the remaining scope of MOVs (i.e. item 2) a risk significance evaluation was conducted. This evaluation consisted of a review of each MOV, its relevant safety function (s) and those of the system (s) it supports. In addition, design and operating conditions were reviewed and identification of those MOVs modeled in the Seabrook Station Probabilistic Risk Assessment (PRA). I 1
For those MOVs not modeled in the PRA, an assessment was made as to the appropriateness of the MOV not being quantified within the PRA given the GL 89-10 concerns. These MOVs are l categorized as low risk significance, it was felt, after this review, that changes to the PRA to incorporate additional MOVs into the PRA were not necessary.
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For those MOVs modeled in the PRA, an assessment was made as to the appropriateness of the {
. existing modeling of these MOVs in the PRA. Issues addressed by this review included: i e
l potential failure modes versus the failure modes modeled in the PRA,
- e failure rates given Generic Letter 89-10 concerns,
. valve design differential pressure, e- inter versus intrasystem common cause issues, 4 e- impacts on initiating event modeling,
- .- model completeness, e external events, and
- e containment performance ,
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j Based upon the above review, the PRA was requantified to obtain an MOV risk ranking. This
] quantitative risk ranking was subsequently adjusted to address additional issues, including ;
shutdown risk (qualitative assessment using the Shutdown PRA Model). i 4 - .
- will be re-ranked using a methodology similar to the one described'above. Re-ranking will account for any changes to the PRA model since the previous evaluation.
1-The risk ranking of all GL 96-05 MOVs will be assessed using the Expert Panel Concept that
- was initiated for the Maintenance Rule. The overall risk ranking for all program MOVs will be
- reviewed. Other operational and maintenance insights will be considered in the review and the j existing risk rankings will be adjusted as appropriate. The Expert Panel review will be j completed to support implementation of the GL 96-05 Program. It is anticipated that the Expert - ,
4 Panel will be completed by the end of 1997. l i
3.3 Margin Determination j
- Generic Letter 96-05 states that "the staff believes that various approaches can be taken by
- licensees to establish a periodic verification program that provides confidence in the long-term ;
. capability of MOVs to perform their design-basis safety functions. With each approach, the 1 licensee should address potential degradation that can result in (1) the increase in thrust or torque j i - requirements to operate the valves and (2) the decrease in the motor output capability of the ;
motor actuator." Generic Letter 96-05 requests that the MOV Periodic Verification Program j
. " ensure that changes in required performance resulting from degradation (such as those caused by age) can be properly identified and accounted for".
As part of implementing the JOG Periodic Verification Program-the NRC requires that all ;
adjustments for margin degradation are considered in the licensee's program. North Atlantic will determine an available margin value for each GL 96-05 MOV. Available margin will be determined as described in Section 2.3 above and will be modified to account for potential stem -
lubrication degradation. Margin degradation for spring pack relaxation will also be considered for inclusion into the total available margin. Margin for seat degradation for butterfly valves will '
also be considered. Ilowever, stem lubrication degradation is not required to be considered for butterfly valves.
. In summary, margin for gate and globe valves will consider the following: diagnostic test I equipment inaccuracy, torque switch repeatability (if appropriate), rate of loading, spring pack .
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l relaxation and stem lube degradation. Margin for butterfly valves will consider diagnostic test {
equipment inaccuracy, torque switch repeatability, spring pack relaxation and seat degradation, i Using this approach, the margin calculation will account for all potential degradation's. The ;
remaining available margin will be used to determine periodic verification testing frequency as described in MPR-1807, Revision 0.
l As part of North Atlantic's MOV Preventive Maintenance Program, safety-related MOV stems !
are cleaned and relubricated on a two refueling outage frequency. Stem lubrication degradation I will be assumed for the periods between relubrication of the stem. Stem lubrication is considered to degrade over each of the two cycles.
Valve operability will be determined based on diagnostic test results meeting the appropriate i acceptance criteria. Using the results from diagnostic testing , new available margin values will !
be determined and schedule adjustments, if required, will he made based on the available margin i and the valve risk ranking.
3.4 GL 96-05 Test Frequencies As stated in the JOG Periodic Verification Testing Program, North Atlantic will statically test its safety-related motor-operated valves in accordance with the JOG " Interim" Utility PV Program Matrix as shown in Attachment #1. Based on the valve's risk signi6cance and its available i margin, periodic testing may be as long as 6 refueling outages or as short as one refueling outage. Additionally, North Atlantic will consider the operating history of each MOV, its )
application and environment when determining the appropriate static diagnostic test frequency.
North Atlantic will schedule periodic verification for each valve into its appropriate test frequency.
North Atlantic will review diagnostic test results after each refueling outage to determine if adjustments to the test frequency are warranted. Establishment of adequate testing frequencies, ;
periodically monitoring test results and making program adjustments as required will assure that adequate margin is available to provide assurance that there is a high level of confidence that each MOV remains operable over its periodic test frequency.
Generic Letter 96-05 allows up to ten years in between a test interval based on current knowledge and experience. GL 96-05 further states that the " licensee should evaluate information obtained during valve testing during the first five year or three refueling outage time period to validate assumptions made in justifying the longer test interval." North Atlantic considers the review of diagnostic test data as described above, as meeting the intent of justifying test frequencies longer than five years or three refueling outages.
3.5 GL 96-05 Program Adjustments North Atlantic will make adjustments to the GL 96-05 Periodic Verification Program, as appropriate, based on the results of periodic reviews / analysis of the JOG test results and JOG recommendations. Program adjustments (frequency changes) may also be made based on North Atlantic's review of test data after each outage as described above. North Atlantic will address any NRC assessment issues that may affect the Periodic Verification Program and make program adjustments determined to be appropriate.
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- 3.6 EPRI MOV Performance Prediction Methodology (PPM) I 1 The EPRI MOV Performance Prediction Program describes a methodology developed to predict
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l dynamic thrust and torque requirements for gate, globe and butterfly valves without performing ;
! ' dynamic tests.' Generic L,etter 96-05 states that "the staff would find it acceptable if a licensee l' applied the EPRI methodology ( in accordance with this generic letter and the conditions and
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i limitations contained in the NRC staff's safety evaluation ) in establishing a program for periodic l
)_ verification of design basis capability." '
s North Atlantic has supponed the development of the EPRI MOV_. Performance Prediction
,. . MethodologyJ At this time, Seabrook has not used the EPRI PPM to determine required thrusts l 1 and torque's for its safety-related MOVs. The reamn the PPM was not used was that North !
Atlantic's valve setup criteria was established prior to :he isuance of the PPM. North Atlantic test results have shown'the'overall adequacy of valve setup. However, North Atlantic may use !
the PPM in the future to assess the adequacy of selected MOVs.
. 3.7 In-Service Testing of MOVs {
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. GL 96-05 states that "the staff would consider a periodic verification program that provides an
[1 acceptable level of quality and safety as an alternative to the current in-Service Testing (IST) requirements for stroke time testing and could authorize such an alternative". North Atlantic ,
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routinely stroke tests safety-related motor-operated valves in accordance with the North Atlantic
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l IST Surveillance Program. North Atlantic plans to evaluate using the GL 96-05 Periodic-
-Verification Program, following its implementation, in conjunction with exercise stroke testing, in lieu of stroke time testing. ASME Code Case OMN-1 as referenced in GL 96-05 will be evaluated for use at Seabrook. Nonh Atlantic recognizes any departure from its current approved IST Program would require a program relief request.
. Conclusion The MOV . Periodic Verification Program established at North Atlantic meets the )
recommendations of Generic Letter 96-05. North Atlantic is a participant in the= JOG MOV Periodic Verification Program. North Atlantic will use safety risk significance, available set up margin, consider the operating history of each MOV, the MOV application and its environment when determining the appropriate static diagnostic test frequency. Known degradation's will be included in determining available margin. Test acceptance criteria are established to verify the acceptability of diagnostic testing.
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{- North Atlantic plans to continue its existing GL 89-10 periodic verification program for i Refueling Outage 05 scheduled to begin in May 1997. The GL 96-05 MOV Periodic Verification Program will be fully implemented for the start of Refueling Outage 06. Full implementation means that periodic verification testing meets the guidelines provided in MPR-1807. Valve testing frequency will be based on the criteria established in MPR-1807.
I Additional dynamic testing will be performed in RF 06 to furtherjustify North Atlantic's valve :
stem friction coefficient.
i i North Atlantic's Periodic Verification Program, as described above, establishes adequate testing frequencies, periodically monitors test results and makes program adjustments as required to assure that adequate margin is available.to provide assurance that there is a high level of !
confidence that each MOV remains operable over its periodic test frequency.
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! ATTACIDIENT 1 l
i l " Interim" Utility PV Program Criteria for Frequency of Static Testing Risk .
H 1 cycle 2 cycles 3 cycles
" 2 cycles 4 cycles 6 cycles
- 3 cycles 6 cycles
- 6 cycles
- Low Medium High MOV Margin
'Not te exceed 10 years based on either 1-1/2 or 2 year operating cycle.
Where:
Low Margin = < 5% Margin represents values Medium Margin = > 5% - < 10% for valve internal age-High Margin = > 10% related degradation only Low Risk = Owners' Group / l Medium Risk = Utility Specific High Risk =
,