ML20029E222
| ML20029E222 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 05/13/1994 |
| From: | Rhodes F WOLF CREEK NUCLEAR OPERATING CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| ET-94-0030, ET-94-30, GL-89-10, NUDOCS 9405170288 | |
| Download: ML20029E222 (2) | |
Text
i s
4 h
WOLF CREEK
' NUCLEAR OPERATING CORPORATION Forrest T. Rhodes Vice Preudent Engmeering May 13, 1994 I
ET 94-0030 U.
S.
Nuclear Regulatory Commission ATTN:
Document Control Desk Mail Station F1-137 Washington, D.
C.
20555
References:
1)
Letter WM 92-0204, dated December 29, 1992 to NRC from B.
D. Withers, WCNOC 2)
Letter WM 93-0032, dated February 25, 1993 to NRC from B.
D.
Withers, WCNOC 3)
Letter dated November 12, 1993 to WCNOC from NRC
Subject:
Docket No. 50-482:
Change to a Commitment Associated to Generic Letter 89-10, " Safety-Related Motor-Operated Valve Testing and Surveillance" Gentlemen:
This letter provides documentation of a change to a commitment that was made in references 1 and 2.
Wolf Creek Nuclear Operating Corporation (WCNOC) committed to refurbish or replace all motor operated valve (MOV) actuators, This letter also provides a change in program philosophy concerning differential pressure testing.
In the commitment documented in references 1 and 2, WCNOC stated:
" Additionally, WCNOC intends to refurbish / replace actuators on all valves in the WCNOC MOV Program prior to the completion of NRC Generic Letter 89-10."
2) will inspect or replace all stem nuts during refurbishment / replacement of actuators on all valves in the WCNOC MOV program prior to the completion of NRC Generic Letter 89-10."
However, since that time, the schedule for refurbishment or replacements has been revised to continue beyond - the committed WCNOC completion date of Decembe:
M, 1994, for Stage 1 of Generic Letter 89-10.
This is based upon a recent change in methodology with respect to the remaining MOVs to be evaluated under the WCNOC MOV program.
This change in methodology involves I
the use of conservative high margins.
High ~ margins are established when j
definite conservative minimum thrust / torque requirements can be determined and relatively large thrust / torque windows can be est.ablished. This approach does lho1 rre n s P O. Box 411/ Burlington KS 66839 / Phone: (316) 0644831 94OSi70288 940513 An EquM oportundy Empoyer MWC/ VET PDR ADOCK 05000482 1
P PDR
ET 94-0030 Page 2 of 3 not delete or eliminate refurbishment or replacements, but potentially extends the period in which this activity is performed.
The ' period of time before refurbish / replacement will be directly proportional to the amount of degradation margin that exists for each MOV.
MOVs with higher design differential pressures (approximately greater than 300 psid) will be refurbished and/or replaced prior to the completion date.
Along with the change in commitment, WCNOC has evaluated the application of full differential pressure testing for the valves remaining in the program.
Thia evaluation is the result of experience gained during the sixth refueling.
outage.
The - original prioritization of MOVs at WCNOC was determined based upon safety significance, high design basis differential pressure,'and other past known problem MOVs.
Duting the sixth refueling outage, the top 52 MOVs from this prioritization were chc en to be set-up and/or differential pressure tested in accordance with the Generic Letter.
Of these 52 MOVs, 42 were differential pressure tested.
The remaining MOVs were not ' differential pressure tested due to the impracticality of the testing, the oossibility of creating conditions detrimental to safety, or the possibility of damaging a component.
In addition, the test data from similar valves was found to be meaningless and the testing of other valves within the family would be futile.
These remaining MOVs are largely gate and butterfly valves with less safety significance and generally have much lower design basis differential pressure.
Based upon this fact and the information, data and the knowledge obtained from this past in plant testing, a change in methodology was initiated.
This revised methodology reduces the number of MOVs that will be subject to differential pressure testing on a case-by-case basis.
The changes involve eliminating differential pressure tests where high margins exist. This margin is based upon conservative factors built into the minimum required stem thrust values for the MOVs and the actual torque switch settings and/or the actuator capability.
This consersative philosophy will create large margins to excessively compensate for a combination of factors and degradation.
The minimum required stem thrusts will be based upon conservative disc and seat coefficients of friction as determined from WCNOC. specific data, EPRI testing, other industry testing and/or any other applicable sources of information.
Each actuator will be optimized to provide the maximum capability to increase I
the margin window.
This program philcacphy is considered in compliance with the Generic Letter 89-10 requirements and the preliminary draf t of Supplement 6 to the generic letter.
WCNOC will continue to:
- 1) maintain a sound basis for cperability,
- 2) test where practicable and when meaningful data will be obtained or when practical,
- 3) group MOVs for which testing is not practicable and not meaningful or practical, and test in a manner that provides adequate ccafidence in the capability to perform the design basis function,
- 4) static test each MOV and adjust it within conservative windows, and
- 5) justify alternate approaches to dynamic testing where sufficient intormation exists to demonstrate the validity of its approach.
, - -, =
-- ~ -. -
ET 94-0030 Page 3 of 3 From* this type of evaluation, MOVs not providing a high confidence margin will be differential pressure tested, if practicable and meaningful or practical, following the original methodology and process.
In either case, the same confidence level will exist in the ability of the MOV to perform its design basis function.
This submittal is being made in accordance with 10 - CFR 50.54 (f) and the reporting requirements of Generic Letter 89-10.
These changes were discussed with members of the NRC staff in a meeting held October 15, 1993 and' summarized in reference 3.
If you have any questions concerning these changes, please contact me at (316) 364-8831, extension 4002 or Mr. Kevin J.
1 Moles at extension 4565, Very truly_yours,
(
.. A / '/
7
/
4 Forrest T. Rhodes FTR/jra cc:
L.
J.
Callan (NRC)
G.
A. Pick (NRC)
W.
D.
Reckley (NRC)
T. Reis (NRC) i f
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