ML20056D676

Safety Evaluation Concluding That Interior Masonry Walls May Be Downgraded to non-fire Related

ML20056D676
Person / Time
Site:	Brunswick
Issue date:	07/28/1993
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20056D674	List: ML20056D673 ML20056D676
References
NUDOCS 9308170310
Download: ML20056D676 (2)

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.i E NUCLEAR REGULATORY COMMISSION l 5 If WASHINGTON. D.C. 20606 0001 .

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION -l REGARDING A REVISION TO A FIRE PROTECTION PROGRAM' COMMITMENT CAROLINA POWER & LIGHT COMPANY  !

i BRUNSWICK STEAM ELECTRIC PLANT. UNITS 1 AND 2  ;

i DOCKET NOS. 50-325 AND 50-324 l

1.0 INTRODUCTION

f By letter dated March 9,1993, Carolina Powar & Light Company (the licensee or j

, CP&L) proposed a revision to a fire protection progra.m commitment at CP&L's t Brunswick Steam Electric Plant, Units 1 and 2 (BSEP). For both units,.CP&L r has proposed to downgrade the three-hour rated masonry block walls in the  !

control building cable access ways (separating fire areas CB-Ola/b, CB-02a/b,  ;

CB-12a/b and CB-13a/b) to non-rated walls. The downgrading of the block walls  :

would allow the removal of the rated fire doors presently . installed in these  ;

walls.

l The walls separating fire areas CB-Ola/b, CB-02a/b, CB-12a/b and CB-13a/b were ,

originally designed to provide a separation between the electrical cables  :

supporting the normal shutdown trains. The staff's November 22,_1977, fire l protection Safety Evaluation (SE) documented that CP&L would install these t walls to ensure that a single fire would not involve redundant safe shutdown  !

trains. The licensee's analysis submitted by letter dated November 8,1977, j included an analysis of the remote shutdown capability for the cable spreading  ;

and control rooms, but did not identify the cable vaults as a separate area;  ;

these areas were enveloped in the one analysis. In the staff's Supplement I  !

to the fire protection SE, dated April 1979, the staff recognized.that CP&L's  :

proposed alternative shutdown capability for the cable spreading and control. j room would allow the plant to be brought to cold shutdown condition.

2.0 EVALUATION i

Section III.G of Appendix R to 10 CFR Part 50 requires that one train of  !

cables and equipment necessary to achieve and maintain safe shutdown must be ,

maintained free of fire damage by one of several means. In a letter dated i May 2, 1983, CP&L sought an exemption to Section III.G.3 on an alternative shutdown capability and associated circuits from the specific requirement to i have a fixed fire suppression system in the cable access ways. In providing  ;

justification for this exemption, CP&L took no credit for the internal block i walls. Accordingly, in granting this exemption, the staff did not. credit the- ,

fire barriers inside the cable access ways. j l

I 9308170310 930728 DR ADDCK 0500 .

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. The licensee submitted an Alternate Shutdown Capability Assessment Report to the staff on April 24, 1984, that defir.ed the cable vaults as one fire area for each unit. The report confirmed that alternate shutdown was required for the cable vault and the control room areas. As stated in the 1984 Alternative Shutdown Capability Assessment Report, the Fire Hazards Analysis, detailed in Section 9.5.1.5 of the Updated Final Safety Analysis Report describes each unit's cable access way as a single fire area composed of four fire zones.

Section III.G of Appendix R to 10 CFR Part 50 requires an alternative shutdown capability independent of the fire area of concern for the case where means are not available to maintain one train of cables and equipment necessary to achieve and maintain safe shutdown free from fire damage.

CP&L has completed an analysis for specific tornado loading situations and found that sufficient differential pressures could be developed across the wall to cause damage and possibly effect equipment in the access ways. The downgrading of the block walls would allow the removal of the rated fire doors presently installed in the walls. Removal of the fire doors would allow the tornado induced pressures to equalize across the walls.

3.0 CONCLUSION

The downgrading of the block walls would allow the removal of the rated fire doors presently installed in these walls. Removal of these doors would provide a vent path to stabilize pressure across the block walls during a-tornado event. The NRC staff has reviewed the information provided and finds that, based on the alternative shutdown capability, the interior masonry walls may be downgraded to non-fire rated.

Principal Contributt s: P. D. Milano C. E. Carpenter Date: July 28, 1993

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