ML20098A954

Provides Addl Info Re Fire Protection Sys Necessary to Close Outstanding Item 13 of Byron Ser.Lower Cable Spreading Rooms Will Be Modified

ML20098A954
Person / Time
Site:	Byron, Braidwood, 05000000
Issue date:	09/19/1984
From:	Tramm T COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
9203N, NUDOCS 8409250333
Download: ML20098A954 (5)

Text

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N Commonwealth Edison

) one First NItional Plata. Chicago Ilhnois

( C ] Address Reply to: Post Office Box 767

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/ Chicago, Illinois 60690 September 19, 1984 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 Sub ject :

Byron _ Generating Station Units 1 and 2 Braidwood Generating Station Units 1 and 2 Fire Protection NRC Docket Nos. 50-454/c55 and 50-456/457 References (a):

May 5, 1982 letter from T. A. Tramm to H. R. Denton.

(b):

October 5, 1982 letter from B. J. Youngblood to L. O. DelGeorge.

(c):

January 6, 1983 letter from T. R. Tramm to H. R. Denton.

(d):

June 17, 1983 letter from T. R. Tramm to H. R. Denton.

Dear Mr. Denton:

This letter provides additional information regarding fire protection systems at Byron and Braidwood stations.

NRC review of this information is necessary to close Outstanding Item 13 of the Byron SER.

In references (a) and (d) Commonwealth Edison provided information to resolve NRC concerns documented in section 9.5.1.5 ef the

. Byron SER regarding fire suppression systems for the Byron /Braidwood cable spreading rooms.

At the time the SER was prepared, the NRC Staff felt-that water suppression systems were needed in the cable screading rooms.. Gas suppression systems were already being installed.

Through discussions with the NRC Staff, we understood that the justifications provided and changes described in references (a) and (d) were adequate to justify this deviatior, from NRC fire protection guidelines.

Recently, it has come to our attention that the NRC's acceptance of the. automatic;CO2 suppressions systems in the lower cable spreading rooms was based, in part, on an understanding that there were separate, manually actuated CO2 systems in these areas.

The-automatic CO2 systems f.

in the lower spreading rooms do have provisions'for manual actuation but completely redundant and separate manual systems have not been provided.

To resolve this discrepancy we propose to modify the lower cable spreading-8409250333 840919 q

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2-September 19, 1984 li.-R. Denton 4

room. fire protection systems as described in Attacnment A to this letter.

' Additional manually actuated control valves would be installed to provide redundant flow paths.. With these modifications, fire suppression system operation is assured, even when single active failures are assumed.

These

' changes, - in ' con junction with. other Byron /Braidwood fire protection features provide more than adequate protection against fires in the lower cable spreading rooms.

If the NRC Staff determines that the Byron /Braidwood lower cable spreading room fire suppression systems are acceptable with the modifica-tions described here, those modifications will be implemented prior to fuel-load.on_all units except Byron 1.

The Byron 1 changes would be made

- within approximately two months of receipt of NRC approval.

Please direct further questiont regarding this matter to this office.-

One signed original and fi' teen copies of this letter are provided for NRC review.

Very truly yours, f $s T. R. Tramm Nuclear Licensing Administrator 1m 4

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ATTACHMENT A-

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-PROPOSED MODIFICATIONS TO LOWER CABLE SPREADING' ROOMS C09 SYSTEM

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LAs presently designed, the Byron /Braidwood CO2 suppression

' system l consists of a single 10 ton storage tank, a single tank discharge valve and. header, and individual zone discharge valves and piping for

'eachDhazard1 zone.- For the lower cable spreading rooms each hazard zone has#a~;large.(lil/2" to.4") initial discharge pipe with zone discharge Evalveland^a smaller-(3/4"sto 1") extended discharge pipe with its own

~ sdischarge valve. :The zone discharge. piping is sized on the basis of room

~ size.

This is shown diagrammatically on the attached Figure 1, in which

the-existing system is shown in solid lines.

'The;existingLtank and zone discharge valves-have three modes of actuat' ion:

1)-they ca'n be automatically _ actuated upon actuation of the

hazard zoneLdetection sy' tem;; 2):.they can be manually actuated from local s

.pushbutton'. stations.(two per hazard zone); and 3) they-can be manually actuated by operating a lever on the electromanual pilot-control (EMPC),

one-of whichEis'provided'for each tank and zone discharge valve.

The

first:two modes are accomplished' electrically, and will result in a E

normaludischarge. cycle which.will automatically terminate after a preset Ltime interval. :The-last mode of.. operation will result in continuous

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Edisch'argefof.theisystem until either the valve is manually closed or the

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JC02 supply 11s. exhausted.

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1The1 existing system, a: standard Cardox system, is adequate to

< protect theLrooms: involved.

However,.in' order to address a staff concern land' expedite licensing'of Byron. Unit 1, the following. modification is

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n(proposed'-to increase the-reliability of the system by providing redundancy ifor/activeLsystem components.

This modification-will also be applied.to Byron' Unit _2 and:both Braidwood Units.

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LThe active-components in the. system are the tank and zone

1. it; discharge 1 valves.- We propose:to provide redundant tank'and zone discharge f

Svalvesias' represented on Figure.1 byLthe dashed. lines.

The new. valves-

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'and. associated. equipment will be.U.L.111sted.

The modifications will be implemented iniaccordance with NFPA 12.

A-redundant zone discharge valve (is;providedLfor the initial discharge line-only.. Redundant extended

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- dischargefvalves are not required-because the capacity of the~ storage

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,1 tank 11s.'suchithat multiple-shot capacity.is provided for1even the largest N

= hazard, zones,fproviding7 adequate redundancy for the zone discharge! valves.

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3 'The new' tank. discharge valve will have two modes of operation:

.1) it-will have manual pushbuttons located near each lower cable spreading room which.'it protects which will electrically operate its EMPC;.and 2)

'it can be manually actuated by a lever on the EMPC.

The new zone

-discharge-valves will only be operable by a manual lever on the EMPC,

.since they will be' located near the hazard zones which they protect.

These new-valves'are expected to be used only in the event of failure of the normal tank or zone discharge valves.

-The. Pre-Fire Plan strategies willL be modified to include the use of this additional backup capability ifHrequired.

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These proposed modifications have been reviewed and endorsed by qualified fire protection engineers'who have agreed that these modifica-

-tions: represent an acceptable additional backup capability.

If these modifications are approved by the staff, they will be implemented on Byron 1~within approximately two months from the date when approval is received.

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