PNO-IV-86-001A, on 860101,loss of Offsite Ac Power Experienced.Caused by Maloperation of Redundant Sys Used to Control Offsite Power Circuit Breakers.Tone Sys Circuit Problem Being Corrected by Licensee

PNO-IV-86-001A:on 860101,loss of Offsite Ac Power Experienced.Caused by Maloperation of Redundant Sys Used to Control Offsite Power Circuit Breakers.Tone Sys Circuit Problem Being Corrected by Licensee

ML20136E422
Person / Time
Site:	River Bend
Issue date:	01/03/1986
From:	Jaudon J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
References
PNO-IV-86-001A, PNO-IV-86-1A, NUDOCS 8601070008
Download: ML20136E422 (2)

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-  ? PRELIMINARY: NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PN0-IV-86-01A

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i y This' preliminary notification constitutes EARLY notice of events of POSSIBLE o safety or public interest significance. The information is as initially receive'd without verification or evaluation, and is basically all that is known by the Region IV staff on this date.

FACILITY:: Licensee Emergency Classification: '

Gulf States Utilities' Notification:of Unusual Event River Bend' Station . ' Alert St. Francisville, Louisiana- Site Area Emergency u Docket No.: 50-458 General Emergency X Not Applicable

SUBJECT:

UNSCHEDULED SHUTDOWN IN EXCESS OF TWO DAYS .

This updates-information'concerning the loss of offsite AC. power on. January 1,

-1986. .

The licensee believes that the trip of offsite" power was caused by maloperation of the redundant system used to control,offsite power circuit breakers; This' redundant system, called' the tone system, .uses fiber optics to transmit control signals. The licensee has found that, ~at either end of- the: ,~

control cable, radio frequency energy will actuate a trip signal. The licensee has also identified a circuit problem which resulted the inability of the' tone system to be reset after it tripped to offsite power (i.e., the reason offsite

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power was locked out until the tone' system was turned,off).' The tone system circuit problem is being corrected by the licensee.-

The other means of offsite circuit breaker control are two pilot wire

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systems. These are run in separate conduits ~in.a common cable trench. The cable trench is filled with concrete.

(cont,onpage2)

. CONTACT: J. P. Jaudon (FTS 728-8140)

DISTRIBUTION: I MAIL:

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, - Tests conducted January 2,1986, indicated.that radio frequency will causeia toneLsystem actuation with the radios used by 'the' security guards.' Security' i-

> tguards were in the vicinity of the tone system at the time that each.offsite *

. - power 1ine tripped.

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1 ,The. licensee!s investigation is' continuing and Region. IV-is monitoring it his

Teffort closely.

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