ML20137A515
| ML20137A515 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 03/17/1997 |
| From: | Muench R WOLF CREEK NUCLEAR OPERATING CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| ET-97-0024, ET-97-24, GL-96-05, GL-96-5, NUDOCS 9703200357 | |
| Download: ML20137A515 (7) | |
Text
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W4pLF CREEK NUCLEAR OPERATING CORPORATION 1
Richard A. Muench Vice President Engineering i
March 17, 1997 ET 97-0024 U.
S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-137 Washington, D. C.
20555
Reference:
Generic Letter 96-05, dated September 18, 1996 5
Subject:
Docket No. 50-482:
180 Day Response to Generic Letter 96-05,
- Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves" Gentlemen:
This letter transmits Wolf Creek Nuclear Operating Corporation's (WCNOC) 180 day response to Generic Letter 95-05,
- Periodic Verificatio. of Design-Basic Capability of Safety-Related Motor-Operated Valves." The attachment to this letter provides a written summary description of the safety-related motor-operated valve (MOV) periodic verification program established at WCNOC.
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If you should have any questions regarding this submittal, please contact me at (316) 364-8831, extension 4034, or Mr. Richard D.
Flannigan at extension 4500.
Very truly yours,
/
9703200357 970317 U1 PDR ADOCK 05000482 P
PDR Richard A. Muench RAM /jad Attachment cc:
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Richard A. Muench, of lawful' age, being first duly sworn upon oath says that he is Vice President Engineering of Wolf Creek Nuclear Operating Corporation; that he has read the foregoing document and knows the content thereof; that t
he has executed that same for and on behalf of said Corporation with full
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power and authority to do so; and that the' facts therein stated are true.and correct to the best of his knowledge, information and belief.
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By j
. Richard /h. Muench 4
Vice President j
Engineering i;
SUBSCRIBED and' sworn to before me this /
day of hitutc)t_, 1997.
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l' ANGELA E.WESSEL NotaryPubic Stateof Kansas My Appt Expres 0 7/d5/9 7 J /997 Expiration Date esa,-
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Attachment to ET 97-0024 Page 1 of 5 6
SUMMARY
DESCRIPTION WCNOC MOV PERIODIC VERIFICATION PROGRAM Introduction Generic Letter (GL) 96-05 requested licensees to establish a program, or to ensure the effectiveness of its current program, to verify on a periodic basis that safety-related motor-operated valves (MOVs) continue to be capable of performing their safety functions within the current licensing bases of the facility. The program should ensure that changes in required performance resulting from degradation can be properly identified and accounted for.
Addressees that have developed periodic verification programs in response to Generic Letter 89-10,
" Safety-Related Motor-Operated Valve Testing and Surveillance" should review those programs to determine whether any changes are appropriate in light of the information provided in GL 96-05.
GL 96-05 specifically requested all addressees to submit within 180 days from the date of the letter, or upon notification to NRC of completion of GL 89-10 (whichever is later), a written summary description of its MOV periodic verification program. The purpose of this submittal is to provide a summary description of the Wolf Creek Nuclear Operating Corporation (WCNOC) safety-related MOV periodic verification program as requested.
WCNOC Existing Periodic Verification procram WCNOC has developed a periodic verification program that provides confidence in the long-term capability of safety-related MOVs to perform their design-basis safety functions.
The program elements are documented in WCNOC Procedures, I-ENG-001,
' Motor Operated Valve Performance Monitoring" and AP 23D-001, " Motor Operated Valve Program." The existing periodic verification program employs a mix of static and dynamic diagnostic testing for Une purpose of quantifying potential degradation that can result in the increase in thrust or torque requirements to operate the valves and/or the decrease in output capability of the motor actuator.
The following provides a more detailed description of the WCNOC periodic verification program relative to the purpose and attributes of periodic static and dynamic diagnostic testing.
I Attachment to ET 97-0024 Page 2 of 5
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Periodic Static Diagnostic Testing Trending of static diagnostic test results provides adequate confidence j
of capturing and recording actuator output changes resulting from potential aging effects. Pursuant to commitments to Generic Letter 89-10, all cafety-related MOVs at Wolf Creek Generating Station (WCGS) j are scheduled for static diagnostic testing on a frequency not to exceed l
five years. Select static diagnostic test results are trended to detect any changes in critical MOV performance characteristics. Trend results, combined with other factors, such as, operating conditions, stroke frequency and maintenance history are considered and may result in 1
adjustments to static test frequencies, where appropriate. Probabilistic l
Safety Assessment (PSA) methods are currently not utilized as a basis for establishing or changing static test frequencies. Trending of static diagnostic test results provides adequate assurance that actuator degradation is readily identified. Trending results confirm that test frequencies are appropriate to ensure that component operability is maintained between scheduled testing.
The MOV program established at WCNOC to satisfy Generic Letter 89-10, accounts for potential valve and/or actuator degradation by including a
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specific degradation factor in MOV setup windows. The degradation margin I
(typically 10%) is available to accommodate potential valve and/or q
act.ua tor aging mechanisms. The degradation margin is in addition to other margin allowances such as diagnostic equipment accuracy, torque
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switch repeatability, rate-of-loading (load sensitive behavior), etc.
The degradation margin is also independent of the inherent conservatism associated with the design basis calculations. Design inputs that establish thrust or torque requirements, such as conservative maximum expected differential pressure calculations, worst case stem-to-stem nut friction coefficients (0.20), design packing friction loads and bounding disc / seat coefficients, yield additional margin to account for potential q
valve and/or actuator aging mechanisms. The WCNOC diagnostic testing i
philosophy also provides additional inherent margin to account for l
potential valve and/or actuator degradation. The torque switch settings j
f of the MOV are set as high in the setup window as practicable for torque-closed valves in order to optimize the margin available for i
potential degradation.
Q f
Periodic Dynamic Diagnostic Testing i
The thrust and torque required to operate a valve are highly dependent I
on the differential pressure, flow, and temperature of the medium across the valve disc..
These conditions are not present during static testing.
Dynamic testing can provide information on the thrust and torque l
requirements and any changes to those requirements resulting from potenti 1 aging effects. In response to GL 89-10, WCNOC committed to test a select sample of valves dynamically every five years to validate that assumed coefficients remain unchanged and/or the assumed values continue to be bounding. A representative sample of all WCGS MOVs was selected to provide a fair assessment of potential degradation among the 1
range in size and types of valves previously dynamically tested. Any adjustments in the scope and /er periodicity of dynamic testing will be j
evaluated based on results Iron the valves dynamically tested during the
Attachment to ET 97-0024 Page 3 of 5 first five year period. However, as a minimum, a sample of valves will be dynamically tested every five years, unless justified otherwise.
As discussed earlier, the WCNOC MOV program includes a specific degradation factor above the minimum required thrust and torque values.
The degradation margin is available to accommodate potential valve and/or actuator aging effects, including potential variances and/or j
increases in the disc / seat coefficient of friction.
General Information Dynamic testing will continue to be done when maintenance performed on an MOV potentially af fects the thrust or torque required to open or close the valve against design basis conditions, unless an engineering evaluation shows that it is not required.
Dynamic testing must be re-performed or an engineering evaluation made when a design change affects the previous test results.
WCNOC has submitted a relief request (Reference 8) for the Inservice Testing program to utilize ASME Code Case OMN-1 (Reference 7) as an alternative to existing component stroke time and position indication testing. This request is based upon the belief that the WCNOC periodic verification program is consistent with, and satisfies the requirements of, OMN-1 testing requirements. When approved by the NRC, WCNOC intends to incorporate this code case into the overall MOV periodic verification program.
Joint Owners Group (JOG) Periodic Verification Program In response to GL 96-05, the BWROG (BWR Owners Group) and WOG (Westinghouse Owners Group) initiated a collaborative effort to support the development of a standardized approach for establishing an MOV periodic verification program.
The cooperative program, referred to as the Joint Owners Group (JOG), has developed a basis for addressing the potential degradation of thrust or torque requirements under dynamic conditions based upon sharing of in-situ dynamic test data by all participating plants. The technical basis for the JOG periodic verification program is documented in Topical Report MPR-1807 titled,
" Joint BWR and Westinghouse Owners' Group Program on Motor-Operated Valve (MOV) Periodic Verification."
WCNOC is an active member of the JOG and will participate in JOG activities, including sharing of dynamic test data and other activities as appropriate to ensure that our program implements the best industry practices. All JOG recommendations relative to periodic verification program adjustments based upon review and analysis of dynamic test results will be incorporated into the WCNOC periodic verification program as appropriate. Additionally, it is expected that the WCNOC periodic verification program and associated procedures will be updated upon consideration of future industry lessons learned such as those resulting from the future NRC Safety Evaluation Repcrt documenting the review of the JOG Topical Report.
Attachment to ET 97-0024 Page 4 of 5 i
Transition to JOG Periodic Verification Procram j
WCNOC will adopt the JOG MOV periodic verification program as a continued means of assuring preservation of design basis capability. The JOG program benefits WCNOC and the entire industry as it serves as a forum for sharing and exchanging information for the purpose of providing a generic type industry solution. The JOG methodology implements a combined margin-based and risk-
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based approach to periodic static testing and a shared approach to dynamic testing to address the potential for increased thrust or torque requirements for MOVs. The approach of performing both static and dynamic diagnostic j
testing provides reasonable assurance that MOV performance degradation is readily identified and reasonable assurance that the test intervals are appropriate to ensure that component operability is maintained during the entire duration of the test cycle.
Transition of the existing periodic verification program to the JOG periodic j
verification program at WCNOC will be accomplished upon completion and/or revision of program documents required to implement the JOG program. The specific implementation date will be dictated by completion of the site-specific risk ranking process of safety-related MOVs. The process will rank safety-related MOVs with respect to their relative importance to core damage frequency, including appropriate considerations regarding other consequences to be added by an expert panel. The existing periodic verification program as detailed earlier will continue to be applied to WCGS MOVs until such time that transition to the JOG periodic verification program is possible.
Prior to, and subsequent to formal transition to the JOG periodic verification program, WCNOC will continue to participate in the JOG program and will j
dynamically test the assigned valves and provide the test results to the JOG.
Criteria established in accordance with the JOG periodic verification program will be used to select the MOV candidates. WCNOC will be responsible for the
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evaluation of dynamic test data obtained on-site in accordance with established procedures. If necessary, corrective actions will be taken in accordance with WCNOC procedures. WCNOC will review JOG recommendations and, test results as necessary and will incorporate the results of the review into the periodic verification program and the MOV program as appropriate.
Summary WCNOC has developed a periodic verification program that provides confidence in the long-term capability of safety-related MOVs to continue to be capable of performing their safety functions within the current licensing bases of the facility. The existing periodic verification program employs a mix of static and dynamic diagnostic testing for the purpose of quantifying potential degradation that can result in (1) the increase in thrust or torque requirements to operate the valves and (2) the decrease in output capability of the motor actuator.
WCNOC is a member of the JOG and will continue active participation in JOG activities, including sharing of test data and other activities as appropriate to ensure that our program implements the best industry practices. Transition of the existing periodic verification program to the JOG periodic verification program at WCNOC will be accomplished upon completion and/or revision of program documents required to implement the JOG program. The existing periodic
Attachment to ET 97-0024 Pa.ge 5 of 5
' verification program will continue to be applied to WCGS MOVs until such time that transition to the JOG periodic verification program is possible.
References The list of references provided here were either used in the preparation of this submittal or have been referenced in the body of this document.
(1) Generic Letter 96-05, " Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves", dated September 18, 1996.
(2) Letter ET 96-0093, dated November 13, 1996, to USNRC from R. A. Muench, WCNOC.
(3) Generic Letter 89-10, " Safety-Related Motor-Operated Valve Testing and Surveillance", dated June 28, 1989.
(4) Letter, dated March 22, 1995, to N.
S.
Carns, WCNOC, from T.
P.
- Gwynn, USNRC,
Subject:
NRC Inspection Report 50-482/95-04.
(5) Letter WM 95-0087, dated May 19, 1995, to USNRC from N.
S.
Carns, WCNOC.
(6) Letter, dated July 21, 1995, to N.
S.
Carns, WCNOC, f rom T.
P.
- Gwynn, USNRC, S'd
- t: NRC Inspection Report 50-482/95.04.
(7) ASME Code Case OMN-1, Titled " Alternative Rules for Preservice and Inservice Testing of Certain Electric Motor-Operated Valve Assemblies in LWR Power Plants".
(8) Letter ET 97-00002, dated January 28, 1997, to USNRC f rom R.
A.
- Muench, WCNOC.