05000338/LER-1983-003-03, /03L-0:on 830122,during Mode 5,RHR Flow Was Lost for 4 Minutes.Caused by Failure of 15 Kv a Inverter to Ac Vital Bus 1-III,de-energizing Auxiliary Relay for Pressure Channel P-1403.Vital Bus 1-III & RHR Flow Restored

/03L-0:on 830122,during Mode 5,RHR Flow Was Lost for 4 Minutes.Caused by Failure of 15 Kv a Inverter to Ac Vital Bus 1-III,de-energizing Auxiliary Relay for Pressure Channel P-1403.Vital Bus 1-III & RHR Flow Restored

ML20028G654
Person / Time
Site:	North Anna
Issue date:	02/09/1983
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20028G650	List: 05000338/LER-1983-003, Forwards LER 83-003/03L-0 05000338/LER-1983-003-03, /03L-0:on 830122,during Mode 5,RHR Flow Was Lost for 4 Minutes.Caused by Failure of 15 Kv a Inverter to Ac Vital Bus 1-III,de-energizing Auxiliary Relay for Pressure Channel P-1403.Vital Bus 1-III & RHR Flow Restored
References
LER-83-003-03L-01, LER-83-3-3L-1, NUDOCS 8302170200
Download: ML20028G654 (2)

LER-1983-003, /03L-0:on 830122,during Mode 5,RHR Flow Was Lost for 4 Minutes.Caused by Failure of 15 Kv a Inverter to Ac Vital Bus 1-III,de-energizing Auxiliary Relay for Pressure Channel P-1403.Vital Bus 1-III & RHR Flow Restored

Event date:
Report date:
3381983003R03 - NRC Website

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s U.S. NUCLEAR RECULATORY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL. REQUIRED INFORMATION)

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LICENSEE CODE-LICENSE NUMBER LICENSE TYPE CAT 0/1/

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UC DOCKET NUMBER EVENT DATE REPORT DATE l

EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10)

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/ On January 22, 1983, with Unit 1 in Mode 5, Residual Heat Removal (RHR) flow was /

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/ lost for approximately four minutes.

Since the Reactor Coolant System tempera- /

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/ ture did not exceed that permitted by t'ne Action Statement-the public health and /

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/ safety were not affected. This event is contrary to T.S. 3.'4.1.3 and 3.7.9.2 and/

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/ reportable pursuant to T.S. 6.9.1.9.b.

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SYSTEM

CAUSE

CAUSE COMP.

VALVE j

CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE I

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SEQUENTIAL OCCURRENCE REPORT REVISION LER/R0 EVENT YEAR REPORT NO.

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

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

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/ This event was initiated when the 15KVA Inverter to AC Vital Bus 1-III failed

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/ thereby de-energizing an auxilary relay for Pressure Channel P-1403 (used for

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/ logic to close MHR suction valve). The de-energizing of the relay caused the RHR/

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/ suction valve to close. Vital Bus 1-III was restored, the RHR suction valve re- /

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/ opened and RHR flow restored.

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l FACILITY METHOD OF STATUS

% POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION (32).

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/0/0/0/ (29)

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ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY (35)

LOCATION OF RFLEASE (36)

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LOSS OF OR DAMAGE TO FACILITY TYPE

DESCRIPTION

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l NAME OF_ PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 e302170200 830209 PDR ADOCK 05000338 0

PDR

[~

Virginia Electric and Power Company t

l North Anna Power Station, Unit No. 1 Attachment: Page 1 of 1 Docket No.350-338 Report No. LER 83-003/03L-0

Description of Event

On January 22, 1983, with Unit 1 in Mode 5, the Residual Heat Removal (RHR) flow was lost for approximately four minutes when the RHR suction valve unexpectedly closed.

Probable Consequences of Occurrence Since any increase in Reactor Coolant System temperature was negligible and well within the limits of the Action Statement the public health and safety were not affected.

Cause of Event

\\

This event was initiated when Inverter 1-III failed thereby causing the 1-III 120 Volt AC Vital Bus to de-energized.

This occurrence resulted in de-energizing an auxiliary relay which provides for the logic to close RHR suction valve (MOV-1701) on an increasing Reactor Coolant System pressure (Wide Range Pressure Channel P-1403).

The inverter incident was determined to be caused by the failure of an SCR 4

i Board in the inverter.

i

Immediate Corrective Action

f Four minuces after losing power to Vital Bus 1-III the power to the bus was restored by shifting the load to the alternate power supply.

The RHR flow was restored after MOV-1701, suction valve to the RHR pumps, was reopened.

Subsequent action included replacement of the SCR i

Board in the inverter and the replacement of the power supply (in the l

Primary Plant Process Cabinet #7) card damaged as a result - of the I

inverter failing.

Scheduled Corrective Action No further action is scheduled.

Actions Taken to Prevent Recurrence l

No further actions are required since this occurrence is considered an isolated event.

Generic Implications There are no generic implications to this event.

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