ML20126A297

Safety Evaluation Accepting Design for Drywell Hydrogen Concentration & Suppression Pool Water Level,W/Respect to Reg Guide 1.97

ML20126A297
Person / Time
Site:	River Bend
Issue date:	12/16/1992
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20126A296	List: ML20126A293 ML20126A297
References
RTR-REGGD-01.097, RTR-REGGD-1.097 NUDOCS 9212180132
Download: ML20126A297 (2)

Text

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SUPPLEMENTAL SAFETY EVALUATION BY THE OFFICE OF yVCLEAR REACTOR REGULATION CONFORMANCE TO REGULATORY GUIDE 1.97 ,

GULF STATES UTILITIES COMPANY RIVER BEND STATION CNIT NO. 1 DDCKET NO. 50-458

1.0 INTRODUCTION

The NRC staff completed their review of the licensee's conformance to Regulatory Guide (RG) 1.97, Revision 3, and provided the safety evaluation to the licensee on June 30, 1986. We found the licensee's design acceptable with res)ect to conformance to RG 1.97, except for the instrumentation associated witi neutron flux monitoring.

Region IV conducted a RG 1.97 inspection, at reported by a letter dated July 30, 1990. By letters dated August 30, 1990, October 11, 1990, and March 28, 1991, the licensee requested us to reevaluate the issues concerning the instrumentation that monitors drywell hydrogen concentration and suppression pool water level.

2.0 EVAtVATION The staff has reviewed the licensee's submittals and concluded that the licensee either conforms to, or has adequately justified deviations from, the guidance of RG 1.97 for the instrumentation that monitors: (a) drywell hydrogen concentration, and (b) suppression pool water level.

(a) RG 1.97 recommends Category 1 drywell hydrogen concentration instrumentation with a range from 0 to.30 percent. The licensee has instrumentation that has dual ranges from O to 10 and 0 to 30 percent.

The instrumentation is normally in the standby configuration with the range set at 0 to 10 percent. The licensee states that this is adequate since they do not use an inerted containment and have alarms at 3.5 percent concentration. The licensee has also describet the hydrogen mixing system and hydrogen recombiners that will maintain the hydrogen concentration below 9 percent. Therefore, we find the use of the 0 to 10 percent drywell hydrogen concentration instrumentation acceptable.

(b) RG 1.97 recommends Category I suppression pool water level instrutaentation with a range from the bottom of the emergency core cooling system (ECCS) suction line to the top of the weir wall. The licensee previously documented instrumentation with a range from the safety relief valve discharge to the top of. the . liner. This instru-mentation was from -18 feet to +4 feet. The staff accepted this range in the June 30, 1986 safety-evaluation, based on the licensee's 9212180132 921216 PDR ADOCK 05000450 p PDR

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statements that' at suppression- pool layels below -18 feet the residual d heat removal:(RHR) pumps have inadsquate net po:ttivo suction head (NPSH) and exhibit vortex forea'clon. The onlytacti a below this lower bound is:to: add water to the suppression pool.

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-The instrumentation'that was actually: installed has a range of

-14.75 feet to +4 feet.- - This range-is conservative-from a NPSH point of.

view for ECCS pump operation and thus acceptable, g i

3.0 CONCLUSION

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Based on our review of the licensee's submittals, we find that the RiverLBend Station Unit No I design for drywell hydrogen concentration'and suppression

-pool water level is acceptable with respect to conformance to RG 1.97, Revision 3.

Principal. Contributor: 8. Marcus HICB/NRR Date: December 16, .1992 ..

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