PNO-V-86-023, on 860426,ESF Load Sequencer for Train a Emergency Diesel Generator Inoperable.Caused by Broken Conductor in Relay Wire Discovered in Late 1985 But Mistakenly Considered Unimportant Grounding Path

PNO-V-86-023:on 860426,ESF Load Sequencer for Train a Emergency Diesel Generator Inoperable.Caused by Broken Conductor in Relay Wire Discovered in Late 1985 But Mistakenly Considered Unimportant Grounding Path

ML20203N883
Person / Time
Site:	Palo Verde
Issue date:	04/29/1986
From:	Miller L, Zimmerman R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
References
PNO-V-86-023, PNO-V-86-23, NUDOCS 8605060176
Download: ML20203N883 (1)

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PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-V-86-23 Date: 04/29/86 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information presented is as initially received without verification or evaluation and is basically all that is known by Region V staff on this date.

FACILITY: Arizona Nuclear Power Project Eme.rgency Classification Palo Verde Unit 2 Notification of Unusual Event DOCKET No. 50-529 Alert Site Area Emergency General Emergency X Not Applicable

SUBJECT:

INOPERABILITY OF EMERGENCY DIESEL GENERATOR TRAIN 'A' LOAD SEQUENCER On April 26, 1986, the licensee discovered that the engineered safety features load ssquencer for the Train 'A' Emergency Diesel Generator (EDG) was inoperable due to a broken conductor in a relay wire. This open circuit would have prevented the Train 'A' EDG output breaker from closing onto the 4160 volt emergency bus, if called upon, by a loss of offsite power.

Preliminary information from the licensee indicates that the wire conductor was discovered to be broken by the licensee in late 1985 prior to low power licensing. However, the function of the wire was mistakenly believed to be an unimportant alternate grounding path. Consequently, it appears that repair of the condition did not receive priority attention by the licensee, and the EDG may have been inoperable from late 1985 to the present.

Pelo Verde Unit 2 is in Mode 3. The Senior Resident Inspector and his staff are following up to confirm this information and assess its significance.

This information is current as of 9:03 am, PDT, on April 29, 1986.

CONTACT: R. Zimmerman, Sr. Resident Inspector L. Miller (602) 386-5760 (415) 943-3869 DISTRIBUTION H St. MNBB Phillips E/W Willste Air Rights 31 55EMail:

Chairman Palladino EDO NRR IE NMSS ADM:DMB Comm. Zech OIA DOT:Trans Only PA RES Comm. Bernthal MPA AEOD Comm. Roberts ELD Comm. Asselstine Regions:

SECY INP08.*f(. NSAC g:J'/

ACRS Licensee: # 1 '/ /

CA (Reactor Licensees) REGION V: FORM 211 PDR Resident Inspector __ (Revised 3/14/83) 8605060176 860429 PDR ILE

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