ML20207P176
| ML20207P176 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 01/12/1987 |
| From: | Johnson I COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8701150181 | |
| Download: ML20207P176 (6) | |
Text
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00AMRSAWesNh Edson 3 One First Nabonel Rese, Chcago, innois Address Hoply to: Post omes Box is7 CNoego,IGinois80000 0767 January 12, 1987 Mr. Harold R. Denton U.S. Nuclear Regulatory Comunission office of Nuclear Reactor Regulation Washington, DC. 20555
Subject:
Quad Cities Units 1 and 2 Request for Appendix R Rxemption NRC Docket Nos. 50-254 and 50-265
Reference:
Letter from I.M. Johnson to H.R. Denton dated December 30, 1986
Dear Mr. Denton:
The above referenced letter provided additional information in response to your staff's questions on the Quad Cities Appendix R program as it pertains to hot shutdown repairs to defeat high impedance faults. The letter indicated that an exemption to Appendix R would be necessary in order to allow the use of fuse pulling as a repair for the purposes of Appendix R.
We are now transmitting to you, for your use, three copies of the proposed Appendix R exemption request for hot shutdown repairs.
If you have any questions regarding this matter, please contact this office.
Very truly yours, I. M. J ns Nuclear Licensi Administrator l
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Attachments 1: Quad Cities Units 1 and 2, New Appendix R Rremption Request for Hot Shutdown Repairs 1
l cc:
T. Rotella - NRR NRC Regional Administrator - Region III j
NRC Resident Inspector - Quad Cities 0
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OUAD CITIES 1&2 TABLE OF CONTENTS PAGE APPENDIX R EXEMPTION REQUEST FOR HOT SHUTDOWN 9.0 9.0-3 REPAIRS JUSTIFICATION FOR REMOVAL OF CONTROL POWER' TO 9.1 9.1-1 DEFEAT HIGH IMPEDANCE FAULTS 9.3-1 9.1.1. Discussion 9.1-2 9.1.2 Conclusion 1
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QUAD CITIES 1&2 9.0 APPENDIX R EXEMPTION REQUEST FOR HOT SHUTDOWN REPAIRS
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Per the provision of 10 CFR 50.12, Commonwealth Edison Company (CECO) request exemption from the requirement of Section III.G.1 of Appendix R that one train of systems needed for hot shutdown be free of fire danage, in so far as this is interpreted as disallowing the use of repairs to implement hot shutdown (SECY-83-269,Section1.2.1). CECO specifically requests that an exemption be granted.
1)
To allow the pulling of closing fuses to defeat high impedance faults.
Section Justification For 9.1 Removal of Control Power to Defeat High' Impedance Faults Justification for these exemption requests is provided in the following section.
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9.0-1 O
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QUAD CITIES 1&2 h
9.1 J_l)STIFICATION FOR REMOVAL OF CONTROL POWER TO DEFEAT HIGH IMPEDANCE FAULTS 9.1.1 Discussion Common power source concerns were addressed in the safe' shutdown analysis.
All of the safe shutdown loads on a given bus are known to be free of fire-induced faults whenever that bus is called upon to power safe _ shutdown loads.
The non-safe shutdown loads that are also connected to the essential buses were not analyzed to determine if a high impedance fault could cause a tripping of the feed breakers.
The safe shutdown procedures address high linpedance f aults on non-safe shutdown loads by instructing the operator to trip all such loads.
Af ter tripping these loads an additional manual action of pulling the control power fuses is specified as a precaution-against spurious closure of electrically-operated breakers.
When a breaker at a motor control center (MCC) is tripped, no further action O
is needed to prevent snur4ous ciosure.
The seme is true for menueiiy-opereted breakers at the 480V switchgear buses (13, 19, 28 and 29).
When an electrically-operated breaker at 4kV or 480V switchgear bus is tripped, spurious closure remains possible until 125V dc control circuit fuses are pulled.
These fuses are rated 15 amperes or less, and the actual load currents.are considerably less therefore no personal safety equipment is needed.
In each of the 430V switchgear buses, the control circuit fuses for all breakers on the bus are housed in a single fuse compartment.
Each breaker's fuses are mounted in a plug-in fuse block that is equipped with a handle for fast, safe removal.
The control circuit fases for each 4kV breaker are mounted in similar plug-in blocks, and are located in the relay compartment directly above the affected breaker.
Separate fuses are used for the closing circuit and the tripping circuit; only the closing circuit fuse block needs to be removed.
9.1-1
QUAD CITIES 1&2
)
The operators routinely rack out 480V and 4kV buses prior to working on the step in racking out a breaker is the removal of the equipment.
The first Removal of the fuses precludes spurious closure and makes it closing fuse.
unnecessary to rack out the breakers.
The time necessary for removal of these fuses is being considered in the manpower requirements for the sa e shutdown r
procedures.
The tripping of unwanted 480V loads needs to be performed only for shutdown paths that use the affected unit's own power train.
The addition of an isolation switch on the non-safe shutdown loads wou increase the operator safety or decrease the time necessary to perform this Some safety related equipment will be disabled by the removal of operation.
these fuses, however this operation as it is incorporated in the safe shutdown procedures follows the require:nents set forth in 10 CFR 50.54(X).
The pulling of fuses is considered a repair for the purpose.of; Appendix'iR_
therefore an exemption to Appendix R is n ece s s ary "~f oF~the' 'iis'E' '~o f~ t h i c -
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7_c procedure to achieve and maintain hot shutdown.
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- d 9.1.2 Conclusion Based on this analysis, the intent of Appendix R requirements are met:also, safe shutdownlofEth[
the pulling of the closing fuses would not affect The justification for renoval of these fuse is summarized -as.follows:
plant.
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The operation needs only to be done for electrically operated breakers at
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i 1) tne 4kV and 430V essential switchgears.
This procedure will only be used to guard against possible high impedance-2) f aults for a fire involving two plant areas.
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3)
The fases are easily identified and removed.
9.1-2
QUAD CITIES 1&2 O
- 4) The operation is familiar to the operators.
All equipment necessary for these operations is in the proximity of the 5) equipment of intended use and is kept under periodic surveillance.
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-,-e 9.1-3
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