ML20136G181
| ML20136G181 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/13/1997 |
| From: | Reid D VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BVY-97-36, GL-96-05, GL-96-5, NUDOCS 9703170228 | |
| Download: ML20136G181 (6) | |
Text
VERMONT YANKEE NpCLEAR POWER CORPORATION Ferry Road, Brattleboro, VT 05301-7002 ENGINE RIN OFFICE j
580 MAIN STREET BOLTON MA 01740 (508)779-6711 March 13,1997 BVY 97-36 United States Nuclear Regulatory Commission ATTN: Document Control Desk j
Washington, DC 20555 4
References:
(a) License No. DPR-28 (Docket No. 50-271)
(b) USNRC Generic Letter 96-05, " Periodic Verification of Design-Basis Capability of i
Safety-Related Motor-Operated Valves," NVY 96-148, dated September 18,1996 (c) Letter, VYNPC to USNRC, BVY 96-143, dated November 15,1996 (d) Letter, VYNPC to USNRC, BVY 95-142, dated December 29,1995 (e) Letter, VYNPC to USNRC, BVY 96-63, dated May 9,1996
Subject:
Vermont Yankee 180-day Response to Generic Letter 96-0q In Reference (b) the NRC requested licensees to establish a program, or ensure the effectiveness of the 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 their facilities, in Reference (b) the NRC also requested that within 180 days from the date of this generic letter, or upon notification to the NRC of completion of Generic Letter 89-10 (whichever is later),
1 Vermont Yankee submit a written summary description of its MOV periodic verification program established in accordance with this generic letter. In References (d) and (e), Vermont Yankee
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notified the NRC of the completion of its Generic Letter 89-10 program. Therefore, the requested program description, provided in Attachment 1 to this letter, is being submitted within the requested 180 days.
We trust that the information provided is acceptable. However, should you have questions or require additional information, please contact this office.
Sincerely, i
VERMONT YANKEE NUCLEAR POWER CORPORATION 170000 Q-AcOS h Donald A. Reid Vice President, Operations I
9703170228 976313
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VERMONT YANXEE NUCLEAR POWER CORPORATION United States Nuclear Regulatory Commission March 13,1997 Page 2 of 2 i
Attachment
<l c: USNRC Region i Administrator USNRC Project Manager-VYNPS "NIOg '
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USNRC Resident Inspector-VYNPS 3 N f
NOTARY
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STATE OF VERMONT
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Then personally appeared before me, Donald A. Reid, who being duty sworn, did state tha MY t,
Operations, of Vermont Yankee Nuclear Power Corporation, that he is duly authorized to execu W he foregoing document in the name and on the behalf of Vermont Yankee Nuclear Power Corporation, and that the statements therein are true to the best of his knowledge and belief.
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s VERMONT YANKEE NUCLLAR POWER CORPORATION United States Nuclear Regulatory Commission March 13,1997 Page 1 of 4 Vermont Yankee 180-Day Response to NRC Generic Letter 96-05:
Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves CURRENT (GENERIC LETTER 89-10) MOV PROGRAM Design basis reviews and Static testing have been completed for all MOVs in Vermont Yankee's Generic Letter 89-10 program. In addition, thirty-nine dynamic tests have been completed on thirty-two MOVs. Setup and testing of the MOVs is performed in accordance with the schedule in Generic Letter 89-10 using state-of-the-art measurement equipment (e.g.
MOVATS TCC, Teledyne Smart Stems and Quick Stem Sensors). Vermont Yankee has implems.1ted Motor Control Center (MCC) based testing as an additional diagnostic and verification tool for AC valves. Vermont Yankee plans to utilize MCC-based testing as the primary testing diagnostic tool for AC and DC powered MOVs.
Vermont Yankee will use the current testing methods and frequencies as established by our current MOV (Generic Letter 89-10) program until the Periodic Verification Program described below is implemented for each applicable valve. As described in Reference (c), Vermont Yankee will have established its Periodic Verification Program by December 31,1997. Once it is established, the program will be phased into implementation for each applicable MOV in the program.
VERMONT YANKEE MOV PERIODIC VERIFICATION PROGRAM Assurance of continued MOV capability will be established through a combination of static and dynamic diagnostic testing and periodic maintenance activities. The testing activities and verification interval for each MOV will be established based on the MOV's safety significance and reliability, including margin and operating conditions such as environmental and fluid conditions, and the results of the MOV Tracking and Trending Program. Periodic verification i
will provide reasonable assurance that in its current configuration each MOV will fulfill its design basis function, with adequate margin to accommodate any potential degradation over the next periodic verification interval. The data collected will be an input to the MOV Tracking And Trending Program which monitors MOV performano and potential degradation. Periodic 1
verification will be implemented and tracked with the overall plant schedule.
Vermont Yankee will use the methodology described in ASME Code Case OMN-1 and the considerations prodd in Generic Letter 96-05 in establishing our Periodic Verification Program. Details of Vermont Yankee's implementation of OMN-1 will be documented within the final Periodic Verification Program. Provided below is a general out!!ne of Vermont Yankee's implementation of the OMN-1 testing requirements.
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VERMONT YANKEE NUCLEAR POWER CORPORATlON United States Nuclear Regulatory Commission i
i Mar' h 13,1997 c
' Attachment 1
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Page 2 of 4,
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t Desian Basis Verification Test (Differential Pressure Testina) l
' The Vermont Yankee Periodic Verification Program will endorse the use of EPRI Performance 1:
Prediction Methodology (PPM) and differential pressure testing. Vermont Yankee is a i
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participant in the Joint Owners Group (JOG) differential pressure testing effort.
There are two basic reasons to perform periodic Differential Pressure (DP) tests:
- 1. To confirm low margin MOVs maintain an acceptable margin within normal variations in
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. performance.
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For low margin MOVs, Vermont Yankee will consider the results of the EPRI PPM in establishing minimum switch settings.' In accordance with our Periodic Verification Program differential pressure testing will be' performed if inservice testing indicates a i
f significant change in performance. It is anticipated that even small changes in performance, beyond expected normal variations, would be detected by inservice testing prior to loss of all margin.
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- 2. ; To monitor potential age-related changes for certain actuator and valve service environments.
For MOVs that are DP testable, with either the valve or the actuator in conditions where the environment or service conditions will degrade MOV performance, Vermont Yankee currently plans to implement DP testing for a representative MOV in that category to -
determine if degradation is taking place. Any significant performance degradation will be applied to all MOVs with those conditions, or additional testing will be done to determine the amount of degradation to each MOV Individual DP tests can confirm whether degradation is unique to an individual MOV or is a phenomenon common to all MOVs in j
those conditions.
Baseline Test (Preservice Test)
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Baseline testing is typically performed at the MOV using direct force and other measurement devices attached directly to the valve and actuator. Setup and testing of the MOVs is
, accomplished using state-of-tim art measurement equipment (e.g. MOVATS TTC, Teledyne Smart Stems and Quick Stem Sensors). MOVs with high reliability, primarily based on high margin, may utilize Motor Control Center (MCC) based methods to set switches via motor torque. Setpoints are established based on the requirements of the Component Design Basis Reviews and then adjusted during implementation for diagnostic equipment inaccuracies and torque switch repeatability. In addition, target windows are determined to provide additional setup margin for the MOV, where possible.
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s VERMONT YANKEE NUCLEAR POWER CORPORATION United States Nuclear Regulatory Commission March 13,1997 4
Page 3 of 4 1
Inservice Tes]
Inservice testing periodically monitors and confirms Baseline testing results and acquires 4
sufficient data to justify lengthening or shortening the Baseline test frequency. Inservice testing will be performed much more frequently than Baseline testing in order to promptly detect performance trends. Inservice testing will be done under static conditions using electrical data obtained at the MCC. Monitoring of electrical characteristics is an acceptable method of inservice testing to detect changes in MOV performance and overall health. Direct force measurement may be used on certain MOVs where testing from the MCC cannot be done. The test method utilized will be capable of determining changes in force output and detecting MOV degradation. When direct force measurement is also acquired, the inservice test could then also be considered a Baseline Test.
When appropriate, inservice testing will be done during plant operation without removing the MOV from service. Each MOV will be evaluated to determine the appropriate plant condition for inservice tests. To provide current information on MOV performance, each MOV will be inservice tested each plant operating cycle except that MOVs with high reliability, primarily based on high margin, will be tested every two operating cycles initially. The Ba. One test period, developed through a matrix of relative risk and reliability, will be lengthev 3 or shortened based on the results and trend of the inservice tests. Evaluation crib ca will bo developed to ensure exceptional performance can be identified.
MOV Exercisina Exercising frequencies will be established based on the individual MOV relative risk and i
reliability. Each MOV within the Vermont Yankee Periodic Verification Program will be exerciseo at least once per operating cycle.
Establishina Test Frecuency Relative Risk The test period between baseline tests shall be initially determined by weighing relative risk versus reliability. MOVs with high reliability and low relative risk would therefore be tested less
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frequently tnan a high risk low reliability MOV.
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IPE-calculated risk "importance" is used as a starting basis for establisinng the relative risk of an MOV. IPE importance reflects the change in calculated Core Damage Frequency that would occur if an MOV were to fail for all IPE accident sequences. Importance values are calculated f 3r failures of single MOVs as well as for failures of " sister" MOVs together. The results are used to classify each MOV's importance as High, Medium or Low based on industry and NRC guidelines.
l Reliability To establish an MOV's reliability, categories are established based on qualitative performance factors, such as available force margin, operating environment, expert panel reviews and inservice test trending. Factors such as poor test performance, high normal ambient temperature and/or extreme service conditions (High Energy Line Break (HELB) isolation] can
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!1 VERMONT YANKEE NUCLEAR POWER CORPORATION United States Nuclear Regulatory Commission
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March 13,1997 I
Page 4 of 4 each reduce reliability. Therefore, using this process, a " Medium" reliability MOV located in the Steam Tunnel, that is a proven marginal performer, and required to isolate a HELB will be moved into the " Low" reliability category to account for these type of unquantifiable challenges.
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- Conversely, MOVs proven to be consistently good performers by inservice tests, may be l
candidates for increasing their reliability ranking.
1-The primary reliability influence will be margin. Margin is the difference between the required 3
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- force to overcome design basis conditions and the available delivery force from the motor l
operator For MOVs with differential pressure testing data, the required force to overcome
- design conditions may be much less than the calculated minimum required switch setting.
Also, MOVs may have design features that allow delivered forces to be well above minimum.
I switch settings. These features will be considered in establishing an MOV's margin. Margin can also change due to maintenance activities or age rehr d phenomenon, so the actual i
margin will be evaluated and adjusted if required, after Post Maintenance, inservice or Baseline testing.
- Margin is initially established by Baseline testing with direct force measurement equipment; however, indirect force measurement may be used for high margin MOVs. 'A matrix of MOV reliability versus relative risk will be developed to establish the initial Baseline test period.
Joint Owners Group (JOG) Periodic Verificatior Proaram Vermont Yankee supports the Joint Owners Group (JOG) Periodic Verification Program which includes, primarily, periodic DP testing of selected valves and providing the test results to the JOG. Vermont Yankee will review the JOG recommendations and, if necessary, the test
' results on which they were based. Vermont Yankee willincorporate the results of this review
-into our Periodic Verification Program.
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IST Proaram In Reference (b), the NRC stated that "the staff would consider a periodic verification program that provides an acceptable level of quality and safety as an alternative to the current IST requirements for stroke-time testing and could authorize such an attemative upon application by a licensee pursuant to the provisions of 10 CFR 50.55a(a)(3)(i)." Once the Periodic Verification Program has been established, Vermont Yankee will review the benefits of this option.
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