PNO-V-85-029, on 850518 & 20,reactor Trip & Safety Injection Occurred Due to Loss of Vital Instrument Ac Power.Caused by Failure of Transformer in Vital Instrument Ac Inverter IY-13 & IY-12 Output Breaker Tripping Open

From kanterella
Jump to navigation Jump to search
PNO-V-85-029:on 850518 & 20,reactor Trip & Safety Injection Occurred Due to Loss of Vital Instrument Ac Power.Caused by Failure of Transformer in Vital Instrument Ac Inverter IY-13 & IY-12 Output Breaker Tripping Open
ML20128C292
Person / Time
Site: Diablo Canyon Pacific Gas & Electric icon.png
Issue date: 05/20/1985
From: Dodds R, Mendonca M
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
References
PNO-V-85-029, PNO-V-85-29, NUDOCS 8505280243
Download: ML20128C292 (1)


- _

i-PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE-PNO-V-85-29 Date: 05/20/85 (This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public

-intorest significance. The information presented is as initially received without verification cr evaluation and is basically all'that'is known by Region V staff on this date.

FACILITY: ' Pacific Gas & Electric Company Emergency Classification Diablo Canyon Unit 1. XX Notification of Unusual Event Docket No. 50-275 Alert San Luis Obispo County, California Site Area Emergency General Emergency Not Applicable

SUBJECT:

REACTOR TRIP AND SAFETY INJECTION EVENTS

- At 7:13 am (PDT) on May 18, 1985, and again at 5:20 am (PDT) on May 20, 1985, a reactor trip cnd safety injection occurred due to the loss of vital instrument AC power.

With the reactor plant at 100% power on May 18, 1985, the first event happened at 7:13 am when a transformer in vital instrument'AC inverter IY-13 failed. Subsequent loss of AC panel PY-13  !

resulted'in a reactor trip from false instrument indication of an open reactor coolant pump bruker. Almost immediately thereafter, a safety injection was initiated due to a false high storm line flow coincident with low steam pressure indication. An " Unusual Event" was

.diciared.- Plant conditions were stabilized in accordance with emergency operation procedures and the event terminated at 8:01 am. All safeguard systems operated appropriately except that

. Discel Generator 1-3 was manually _ shutdown af ter only 2 to 3 minutes when a belt broke on the cugine driven fuel oil pump. The reactor was started up and returned to power operation

.following repair and testing of'the failed inverter and-diesel generator at 5:30 am on M:y'19, 1985.

On May-20, 1985, at 5:20 am, another reactor trip and safety injection was experienced from 55% power'when vital instrument inverter IY-12 output breaker tripped open. With AC panel PY-12 de-energized, the reactor tripped once again from a false instrument indication of an opsn reactor coolant pump breaker. Safety injection initiated immediately due to a false high atsrm line flow coincident with low-low "TAVC" indication. Plant conditions were stabilized end all safeguard system operated acceptably. An " Unusual Event" was declared at 5:20 am and~

tsrainated at 5:49 am..

Tha-licensee has included this information in their daily report to the media and, as a rscult,-has been responding to media inquiries. Region V will also respond to inquiries.

CONTACT: R. T. Dodds M. Mendonca FTS'463-3720 (805) 595-2354 DISTRIBUTION

. H St. h9I MNBB Phillips!* E/W IE Willste NMSS Air Rights ail:

ADM:DMB Chnirman Pallidino EDO NRR DOT:Trans Comm. Zech PA .0IA RES MPA AEOD Only

~Comm. Bernthal Comm. Roberts ELD Comm. Asselstine Regions: k d'~2 2 /Sj/th7--J.*c2.g2r _. J,*o]

SECY- INPO 7.*J (- NSAC ACRS. Licensee: $1/ J (Reactor. Licensees) REGION V: FORM 211 CA PDR ResidentInspector1II7 (Revised 3/14/83)

~

, 8505280243 850520 ~~~)7 PDR ISnE .

0 g.

PNO-V-85-029 PDR-i