ML19337B642
| ML19337B642 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 10/02/1980 |
| From: | Trimble D ARKANSAS POWER & LIGHT CO. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| 1-090-21, 1-90-21, NUDOCS 8010080331 | |
| Download: ML19337B642 (2) | |
Text
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ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 UTTLE ROCK. ARKANSAS 72203 (501)371-4000 October 2, 1980 i-090-21 Director of Nuclear Reactor Regulation ATTN:
Mr. Robert W. Reid, Chief Operating Reactors Branch #4 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Subject:
Arkansas Nuclear One - Unit 1 Docket No. 50-313 License No. DPR-51 Fire Protection - SER Item 3.16 (File:
2040, 1510)
Gentlemen:
As required by the ANO-1 Fire Protection Safety Evaluation Report (Item 3.16), the following information is provided to describe the effects of fires involving associated circuits at ANO-1.
An evaluation was performed at ANO-1 with regard to fires degrading safe shutdown systems through associated circuits.
For this evaluation the following three systems were considered essential to accomplish safe shut-down assuming no concurrent accident with the fire and the loss of offsite power.
These assumptions are consistent with the ANO Fire Hazards Analysis and NRC criteria.
1.
High Pressure Injection 3.
Emergency Diesel Generators Under the SER definition of associated circuits (circuits connected to safety systems but perform non-safety functions) there are two routing configurations that could possibly cause concurrent destruction of redundant associated cir-cuits by fire -routing in adjacent raceway or a common raceway.
Neither con-figuration is precluded by the separation criteria for Class 1E circuits.
The failure modes of circuits are opea circuits, hot shorts, short circuits and grounds.
Hot shorts are defined as shorts which take place when con-ductors come into physical contact without operating an overcurrent pro-tective device.
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1-090-21 October 2, 1980 s
An open circuit in a non-safety cable, regardless of its routing, will not cause unacceptable consequences in a safety circuit.
For adjacent raceway routing, a hot short cannot occur between redundant associated cables due to physical separation.
A hot short to a cable which is not redundant will not degrade both channels of a safety system.
With redundant associated circuits routed in a common raceway, a hot short could develop between channels and possibly result in loss of control power or incorrect indication.
This made it necessary to identify redundant asso-ciated cables in common raceways and determine if degradation of the system could occur.
In our review of the safe shutdown systems, nine cases of redundant associ-ated circuits with common routing were identified.
In all nine cases, the associated circuits are electrically isolated from the Class 1E portion of the circuit by contacts.
The contact's control power is from sources that are electrically independent of the safe shutdown systems.
The review also showed that indicating lamp circuits are connected to Class 1E power sources and are treated as Class 1E circuits.
I The review and evaluation can be summarized with the following points:
1.
Open circuits do not have a degrading effect on the operability of safe shutdown systems.
2.
Hot shorts will not effect both channels of a system unless they are routed in the same common raceway.
In'all cases identified at ANO-1 where redundant safe shutdown associated cables were routed together in a common raceway, they were electrically isolated from the Class 1E portions of the system.
3.
Hot shorts involving Channel 1 associated and Channel 2 Class 1E re-dundant cables will not degrade both safety channels concorrently due to electrical isolation of the Channel 1 associated circuit from the Channel 1 and 2 Class 1E circuits.
4.
Short circuits or grounds may open circuit breaker or fuses but cannot affect safety related system control power because of the independence of power sources.
Therefore, the conclusion is that all anticipated failure modes of associated Class 1E circuits will not degrade the safe shutdown systems' operability or capability at ANO-1.
Very truly yours, bw e. @A David C.-Trimble Manager, Licensing DCT: RAB:DEJ:skm
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