ML19210C119

RO 79-13:on 790808,reanalysis of Switchyard Voltage Indicated That Present Setpoint for Bus Unloading Is Insufficient to Prevent Nuclear Svcs Busses from Decreasing Below 75% Rated Voltage.Undervoltage Relay Changed

ML19210C119
Person / Time
Site:	Rancho Seco
Issue date:	11/02/1979
From:	Reinaldo Rodriguez SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
RJR-79-486, TAC-10968, NUDOCS 7911130298
Download: ML19210C119 (1)

Text

ri tSMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT C 6201 S Street, Box 15830, Sacramento, California 95813; (916) 452 3211 RJR 79-486

. c.Ts November 2, 1979

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n Mr. R. H. Engelken Regional Director s _l, -

U. S. Nuclear Regulatory Commission 1990 N. California Boulevard Saito 702, Walnut Creek Walnut Creek, California 94596 Re: Operating License DPR-54 Docket No. 50-312 Reportable Occurrence 79-13

Dear :

Ir. Engelken:

In accordance with Technical Specifications for Rancho S._co Nuclear Generating Station, Section 6.9.4.1.h, the Sacramento :1unicipal Utility District is hereby reporting the following as Reportable Occurrence 79-13.

The District received a letter f rom Mr. William Gammill (NRC - Washington) on August 8, 1979, requesting an analysis of the Rancho Seco Switchyard voltage decreasing to 214 KV.

The re-analysis indicated that the present setpoint for b us - unloading is insuf ficient to prevent the Nuclear Service Busses from decreasing below 75% rated voltage as required by the FSAR.

The District proposes to set the undervoltage relay for the Nuclear Service Busses at 0.9 rated voltage and moving the Diesel Room Ventilator Fans from Loading Sequence from Block 2 and connecting the fans to Block 3.

This modification will prevent the voltage at the Safety Features equipment from decreasing below the minimum design operating voltage of 73% rated.

These modifications will be completed during the November 17, 1979 shutdown.

A complete report will be furnished to your office within the next 14 days.

This occurrence was reported to H. Canter, our "on-site" inspector, verbally on November 1, 1979.

Respec ully submitted,

)A s I

N s

s R.J.Rbdrigue%

1320 144 Manager, Nuclea Operations 1/'

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