ML19351D650

LER 80-080/03L-0:on 800908,power to 120-volt Ac Vital Bus 1-IV Was Lost.Caused by Supply Break for Inverter,Which Supplies Power to Vital Bus 1-IV,in Open Position.Power Restored Via Installed Transformer

ML19351D650
Person / Time
Site:	North Anna
Issue date:	10/07/1980
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19351D646	List: ML19351D644 ML19351D650
References
LER-80-080-03L, LER-80-80-3L, NUDOCS 8010140423
Download: ML19351D650 (2)

Text

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LEAR REGULATORY COMMISSIoy

/% LICENSEE EVENT REPORT 4

CONTROL BLOCK / / / / / / / (1) (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

/0/1/ /V/A/N/A/S/1/ (2) /0/0/-/0/0/0/0/0/-/0/0/ (3) /4/1/1/1/1 (4) / / / (5)

LICENSEE CODE LICENSE NUMBER LICENSE TYPE CAT

!!! /L/ (6) /0/5/0/0/0/3/3/8/ (7) /0/9/0/8/8/0/ (8) /3 /n/n/7/n /n/ (9)

DOCKET NUMBER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10) 1

/0/2/ / On September 8,1980, with the Unit at 100% power, power to the 120 Volt A.C. /

/0/3/ / Vital Bus 1-IV was lost contrarv to T.S. 3.8.2.1 and reportable by /

/0/4/ / T.S. 6.9.1.9.b. The incident is not generic. Since redundant instrumentation /

/0/5/ / was available, the health and safety of the general public were not affected. /

-/0/6/ / /

2

/0/7/ / /

/0/8/ / /

SYSTEM CAUSE CAUSE COMP. VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

/0/9/ /E/B/ (11) /X/ (12) /Z/ (13) /G/E/N/E/R/A/ (14) /F/ (15) /Z/ (16)

SEQUENTIAL OCCURRENCE REPORT REVISION

^

LER/R0 EVENT YEAR REPORT NO. CODE TYPE NO.

(17) REPORT NUMBER /8/0/ /-/ /0/8/0/ /\/ /0/3/ /L/ /0/ /_1/

ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP. COMPONENT TAKEN ACTION ON PLANT METHOD HOURS SUBMITTED FORM SUB. SUPPLIER MANUFACTURER

/X/ (18) /Z/ (19) /B/ (20) /C/ (21) /0/0/0/6/ (22) /Y/ (23) /N/ (24) /A/ (25) /S/2/5/0/ (26)

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

/1/0/ / ThesupplybreaEerfortheinverterwhichsuppliespowertoVitalBusIVwas /

/1/1/ / found in the "Open" position. How the breaker became "Open" could not be /

/1/2/ / determined. Power to tha Vital Bus was restored via the installed transformer./

j /1/3/ / Power supply to the Vital Bus was later switched to the inverter. /

i /1/4/ / /

~

FACILITY METHOD OF STATUS  % POWER OTHER STATUS DISCOERY DESCRMION (32)

/1/5/ [Ef_(28) /1/0/0/ (29) / NA / (30) DISC 0ERY/

/A/ (31) Operator Observation /

i ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY (35) LOCATION OF RELEASE (36)

/1/6/ /ZL (33) /Z/ (34) / NA / / NA /

PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION (39)

, /1/7/ /0/0/0/ (37) /Z/ (38) / NA /

PERSONNEL INJURIES NUMBER DESCRIPTION (41)

/1/3/ /0/0/0/ (40) / NA /

LOSS OF OR DAMAGE TO FACILITY TYPE DESCRIPTION 3)

/1/9/ -/Z/ (42) / NA /

PUBLICITY ISSUED DESCRIPTION (45) NRC_USE ONLY

/2/0/ /V[(44) / NA ._./////////////

NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 8 01 014o gz3

Virginia Electric and Power Company North Anna Power Station, Unit 1

Attachment:

Page 1 of 1 Docker No. 50-338 Report No. LER 80-080/03L-0 Description of Event On September 8, 1980, with the Unit at 100% power, power to the 120 Volt AC Vital Bus 1-IV was lost. The loss of Vital Bus 1-IV caused the "A" steam generator (S/G) feedwater flow signal to go to zero which caused the feed reg. valve for "A" S/G to open. This reduced flow to "B" and "C" S/G's. The reactor tripped due to steam flow /feedwater flow mismatch with low S/G level in "C" steam generator. Loss of a vital bus is contrary to T.S. 3.8.2.1 and reportable by T.S. 6.9.1.9.b.

Probable Consequences of Occurrence Other vital busses were powering redundant instrumentation and protection systems. In addition, protection systems powered by Vital lus IV fail to a tripped condition and power was restored to Vital Bus IV within 5 minutes after being lost. Therefore the health and safety of the public were not affected.

Cause of Event The cause of the loss of Vital Bus 1-IV was the opening of the supply breaker to the inverter for Vital Bus 1-IV. It could not be determined how the supply breaker became open but the switch was in the "0 PEN" rather than the " TRIPPED" position. Cable pulling was in progress in the vicinity of the inverter at the time of the loss of the Vital Bus. Although it is possible for cable to have fallen on the inverter breaker and opened it, the electrician who was pulling the cable did not 4

think that the cable had come in contact with the switch.

Immediate Corrective Action Power supply to Vital Bus 1-IV was switched to the installed 480/120 Volt A.C. transformer which restored vital bus power. This was performed within 5 minutes of the loss of the vital bus. After verification by an electrician and an operator that the inverter was in a non-tripped condition with no apparent faults, the inverter was re-energized and loaded with Vital Bus 1-IV.

Scheduled Corrective Action 1 Since the occurrence is non-repetitive, no scheduled corrective

, action is required.

Actions Taken to Prevent Reccurrence None required.

Generic Implications None

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