ML20113H533
| ML20113H533 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 07/31/1992 |
| From: | Horn G NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEIN-92-018, IEIN-92-18, NSD920810, NUDOCS 9208040247 | |
| Download: ML20113H533 (2) | |
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Gf NtRAL OFFICE
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O P O DOx 499. CoLUMDUS NE BRAbKA 6hfiO2 04#9 i
T Nebraska Public Power District
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Y memmem=wemmamummmtma em-e c m m.mumere m use u m NSD920810 July 31, 1992 U.S. Nuclear Regulatoty Commission Attention:
Docurnent Control Desk Vashington, DC 20555
Subject:
pollow-up letter on Corrective Measures for permanent Resolution of Restoration of Alternate Shutdown capability Cooper Nuclear Station 6RC Docket No. 50 298, DPR 46
Reference:
G. R. Ilorn Letter to USNRC dated July 8,1992 " Notification of plans to restore Alternate Shutdown Capability" Centlemen:
pursuant to discussions held with Mr. Roby Bevan, NRC project Manager for Cooper Nuclear Station (CNS) this letter iu a follov up to the reference. wherein the District notified the NRC that the Alternate Shutdown capability was declared inoperable following a review of NRC Infortnation Notice 9218.
The reference discussed that the possibility exists, in certain fire scenarios, for control circuit faults to occur in 19 rootor operated valves (MOV's) prior to the transfer of their control to the ASD panel.
The circuits for these valves must be modified to preclude the possibility of MOV damage as a result of a " hot short" post fire spurious actuation, to further assure expected operation in a environment.
The permanent resolution of this issue will be accomplished by modifications to the MOV control circuitry. The modifications will consist of " repositioning" the position lirait and torque switches in the control circuit so that these switches cannot be bypassed by a " hot short" phenornenon.
The potential for MOV damage which previously existed as a result of the " hot short" spurious actuation is eliminated, and MOV operation is not affected.
In addition, this modification will assure continued Alternate Shutdown Capability. The District is committed to cortplete these MOV control circuit modifications prior to the startup from the Spring 1993 refueling ot.tage presently scheduled to begin in March 1993.
Since the modifications involved in resolving this issue require access to MOV's for rewiring and cable pulls, the circuits must be de energized and in most instances their respective sys terns declered inoperable, performing these l
modifications during plant operation would require voluntarily entering Technical i
Specification LCO's with the resultant loss of system availability to correct a l
design deficiency for an extremely low probability event.
By irnpleme. ting the l
permanent corrective actions durir.g a plant shutdown, the systems can be worked on during plant conditions that do not require their availability to mitigate against plant accidents or transients or our defense in depth shutdown strategy.
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NSD920810 Page 2 of 2 The District will continue t o abide by the cotopensatory uteasures descr.! bed in the reference until the permanent resolution of this issue is cotopleted.
These interim measures, in conjunction with the plant's existing fire detection and suppression capabilities required by Technical Specifications and the extremely low probability of a fire occurring in those areta that would cause a loss of ASD capability, will maintain the required level of safety for continued operation of CNS through March 1993.
I If you have any questions, please call.
Sin orely,
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Horn N
ar Power Group Hanager CIUl/ cj a:hotshort cc:
U. l S. Nuclear Regulatory Commission Region IV Arlington TX NRC Sentor Resident Inspector Cooper Nuclear station
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