ML20235K687

Safety Evaluation Accepting Util Monitoring Sys for UHS as Proposed in

ML20235K687
Person / Time
Site:	River Bend
Issue date:	09/28/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20235K682	List: ML20235K679 ML20235K687
References
NUDOCS 8710050196
Download: ML20235K687 (2)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SAFETY EVALUATION REPORT RIVER BEND STATION, UNIT 1 DOCKET NO. 50-458 ADEQUACY OF ULTIMATE HEAT SINK TEMPERATURE MONITORING SYSTEM

1.0 INTRODUCTION

l By letter dated June 29, 1987, Gulf States Utilities Company (GSU), the licensee I for River Bend Station (RBS) submitted a description of a proposed temperature I monitoring system for the RBS Ultimate Heat Sink (VHS). This submittal was in l

) response to License Condition 2(C)(9) of Fecility Operating License NPF-47 and the requirement stated in Supplement 3 of the Safety Evaluation Report related to the operation of River Bend Station (NUREG-0989). Simply stated, the staff has requested that a monitoring system for the UHS acceptable to the staff, be installed at RBS prior to startup following the first refueling outage.

2.0 EVALUATION The proposed temperature monitoring system for the RBS UHS consists of two independent circuits. The overall philosophy of the approach is to provide one circuit to process temperatures within the expected high but narrow tempera-tures band and a second circuit capable of monitoring temperatures over a much wider range. The narrow range circuit consists of eight (8) Resistance Tempera-ture Detectors (RTDs) wired to a microprocessor. Four (4) RTOs wired to another microprocessor comprise the wider band circuit.

The narrow range system provides an averaged temperature within the ranges of 75 and 85 degrees F. To assure the widest possible temperature range, the wide range system can measure an averaged temperature from 0 to 100 degrees F.

This is f ar beyond any anticipated temperatures during the design life of the plant. The narrow range RTOs are mounted on two vertically mounted " wands" separated 180 degrees apart within the square cross sectional profile of the standby cooling tower basin. Each wand contains four RTDs located along 40 feet of water depth. The wide range RTDs are similarly located on two wands along the other two sides of the basin.

Indication of the averaged temperature of both temperature bands will be provided within the control room. The raceway system and equipment supports will be seismically qualified to prevent damage to the Category I UHS basin structure.

The number and location of the proposed RTDs are sufficient to assurc an accurate measured averaged temperature of the UHS. Additionally, the quality of the com- .

ponents and the fact that the major components will be seismically supported  !

assure that the system will remain functional during the anticipated period of {

use.

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3. 0 CONCLUSION On the basis of the above consideration, the staff concludes that the River Bend Station monitoring system for the UHS as proposed is acceptable. However, the license has not provided appropriate Technical Specifications for this system. Proposed TSs should be provided before the review of the system can be considered complete and the license condition satisfied.

Dated: September 28, 1987 Principal Contributor: J. Kudrick i

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