ML20246E550
| ML20246E550 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/23/1989 |
| From: | Michael Ray TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8908290183 | |
| Download: ML20246E550 (5) | |
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- TENNESSEE VALLEY ' AUTHORITY
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CHATTANOOGA.- TENNESSEE 37401 l
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?AUS 231989 U.S. Nuclear' Regulatory Commission 1 ATTN: Document Control Desk i
Washington, D.C.
20555 Gentlemen:
~In the Matter of
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Oocket Nos. 50-327 lj Tennessee Valley Authortty
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50-328 l
~SEQUOYAH NUCLEAR PLANT (SQN) - 10 CFR 50 - APPENDIX.R - FIRE PROTECTION j
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Reference:
. Letter from Steven D. Richardson to 0. D. Kingsley, Jr., dated l
December 30, 1988, "NRC Inspection Report Nos. 50-327/88-24 and 50-328/88-24" In response to the referenced letter. TVA is providing the long-term corrective actions for the 10 CFR 50, Appendix R, Interactions 114 and 120.
Interaction 114 identified cables associated with the Unit 2 pressurizer l
power-operated relief valve 2-PCV-68-340A and B train auxiliary power cable for block valve 2-FCV-68-332 as not meeting the separation requirements of 10 CFR 50, Appendix R, Section III.G.2.
Interaction 120 identified cables that could interact with the control cables for the volume' control tank outlet valves (FCV-62-132, 133) at multiple locations within the plant resulting in spurious closure, Spurious closure of either valve could cause loss of suction to the operating centrifugal charging pump. In-certain plant locations, a fire'could cause both a spurious volume cont'rol tank valve' closure and damage to the cables to the nonoperating centrifugal charging pump. A commitment was made in a letter from R. L. Gridley to NRC dated April 13, 1988, to implement long-term corrective action for this issue by the end of the Cycle 4' refueling outage for each respective unit. The present' commitment on this interaction for each unit is herein revised to specify the proposed resolution. contains background information and the proposed resolution for the interactions. contains TVA commitments.
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1 U.S. Nuclear. Regulatory Commission AUS 23 B89-stJyil-bE
- If you have any questions concerning this submittal, please telephone t-L-
M.:A. Cooper at'(615)~843-6651.
Very truly yours,-
TENNESSEE-VALLEY AUTHORITY h
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Mana r, Nuc1 thcensing-and Regulatory Affairs Enclosure ~s 1
cc (Enclosures):
Ms. S. C. Black, Assistant Director for Projects '.
TVA Projects Division..
U.S. Nuclear Regulatory Commission One White Flint,' North, 11555 Rockville Pike Rockville,' Maryland 20852 Mr. B. A.' Wils'on, Assistant Director for Inspecticn Programs -
TVA Projects Division U.S. Nuclear Regulatory Commission Region _II' 101 Marietta Street, NW, Suite 2900
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Atlanta, Georgia" 30323 NRC Resident Inspector
-Sequoyah Nuclear Plant
.2600 Igou Ferry Road
-Soddy-Daisy, Tennessee 37379 l
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ENCLOSURE-1 SEQUOYAH 10 CFR 50,' APPENDIX R INTERACTIONS 114 AND 120' Interaction 114'
.The 10 CFR 50, Appendix R reanalysis performed for SQN in 1984 identified-
-Interaction 114.
The' interaction involved the control circuit cable for the Unit 2. pressurizer power-operated relief valve-(P0kV).2-PCV-68-340A and the-train B auxiliary power cables required for the PORV's associated block valve l
(2-FCV-68-332). The location of.the interaction is the Unit-2 control rod drive (CRO) equipment room located on elevation 759 in.the auxiliary.
building. A fire at this location could cause spurious opening of the PORV and failure of the power cable to the associated block valve thereby creating a possible. uncontrolled reactor coolant system depressurization.
The original disposition of this interaction was'that no corrective action was needed because the PORV cable did not contain any of the required wire combinations.that would allow spurious opening of the PORV.
However, this analysis did not consider external (cable-to-cable) hot shorts as being credible.
The original disposition of Interaction 114'was determined to be inadequate during NRC inspection-327, 328/88-24 and 88-37. As a result, TVA implemented an hourly roving fire watch patrol as an interim solution. The following provides the recommended long-term resolution.
The proposed resolution of Interaction 114 is to relocate the control power cable for PORV 2-PCV-68-340A from its present cable tray in the CRD equipment room to a dedicated. conduit thereby eliminating any possibility of spurious operation. This modification will be completed by the end of the Unit 2 Cycle 4 refueling outage.
This interaction only exists on Unit 2.
Interaction 120 Interaction 120 was also identified as part of the 1984 10 CFR 50, Appendix R,
. reevaluation. -The interaction involves fire-induced fault conditions that could cause spurious closure of the volume control tank (VCT) outlet-valves (FCV-62-132/133).
These valves are located in series, and therefore, spurious closure of either valve because of fire could cause loss of suction to the operating centrifugal charging pump (CCP) and the pump itself.
In addition, this interaction discusses fire in other identified areas of the plant that could cause both spurious VCT valve closure and cause damage to the nonoperating CCP circuits resulting in potential loss of charging capability.
.The original disposition of this interaction consisted of operator action to remove power from the valves and to switch over to the refueling water storage tank (RWST) for CCP suction if fire was confirmed in various areas of the auxiliary building.
This disposition also stated that external (cahle-to-cable) faults were not considered credible.
This disposition was also determined to be inadequate during NRC inspection
~327, 328/88-24.
TVA could not provide adequate assurance to guarantee that, if the valves closed and the nonoperating CCP was also damaged by fire, the operating pump could be shut off before sustaining damage.
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. In a letter from TVA to NRC dated April 13, 1988, TVA provided additional
- Information on Interaction 120, regarding cable-to-cable fault conditions, and a commitment to resolve Interaction 120 by the end of the Cycle _4 refueling outage for each respective unit.
NRC accepted use of an hourly roving fire watch for affected areas as an interim resolution.
Addition of stem-mounted limit switches on the VCT outlet valves designed to open the redundant train RWST outlet valve is proposed as the resolution for Interaction 120.
The proposed limit switches will be installed in such a
' manner that, when a VCT valve begins to close, a signal to the opposite train RWST valve will cause the RWST valve.to begin opening..The placement of the limit switch on the valve will be such as to ensure that adequate suction is maintained to the operating CCP.
Utilization of stem-mounted limit switch interlock circuits between the VCT outlet valves (FCV-62-132/133) and the motor control centers (MCC) for the RWST valves (FCV-62-135/136) will be protected in accordance with 10 CFR 50, Appendix R, Section II.G.2 requirements. This protection will extend from immediately outside the VCT room on elevation 690 of the auxiliary building to each RWST outlet valve MCC located on elevation 749 in the auxiliary building.
Although a fire originating in the VCT room could cause spurious VCT valve closure, a fire at this location will not damage the nonoperating CCP.
If a fire starts in this room resulting in spurious VCT valve closure, a suction path from the RHST-will be manually aligned, and the nonoperating CCP will be started.thereby reestablishing charging.
The probability of spurious (nonfire) transfer from the VCT to the RWST is significantly less with the stem-mounted limit switches than with a pressure switch because the limit switches will be a function of actual valve stem movement instead of pressure that could fluctuate.
The proposed modification will be completed by the end of the Cycle 4 refueling outage for each respective unit in accordance with the existing commitment pertaining to this interaction, which is hereby revised to reference the proposed resolution for Interaction 120.
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<;s LIST-OF COMMITMENTS i
- 1..TVA will resolve SQN Appendix R,' Interaction 114, by the end of the' Unit 2 Cycle l4 refueling outage by relocating the contro1' power cable for PORV PCV-68-340A from its present cable tray in the CRD equipment room-to a dedicated conduit..
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TVA will' resolve SQN Appendix R, Interaction 120,~by adding 1.imit switches r
to the VCT outlet. valves (FCV-62-132, 133) Interlocking the valves with-the opposite train RHST outlet valve to prevent loss of charging capability because of fire by the end'of the Cycle 4 refueling outage for-
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each respective' unit.
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