05000339/LER-1981-052-03, /03L-0:on 810619,nuclear Instrumentation Channel N-35 Observed to Be Reading Low & Erratic W/Unit Recovering from Turbine Trip.Caused by Failure of High Voltage Power Supply.Power Supply Replaced

/03L-0:on 810619,nuclear Instrumentation Channel N-35 Observed to Be Reading Low & Erratic W/Unit Recovering from Turbine Trip.Caused by Failure of High Voltage Power Supply.Power Supply Replaced

ML20009F512
Person / Time
Site:	North Anna
Issue date:	07/13/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009F507	List: 05000339/LER-1981-052, Forwards LER 81-052/03L-0 05000339/LER-1981-052-03, /03L-0:on 810619,nuclear Instrumentation Channel N-35 Observed to Be Reading Low & Erratic W/Unit Recovering from Turbine Trip.Caused by Failure of High Voltage Power Supply.Power Supply Replaced
References
LER-81-052-03L, LER-81-52-3L, NUDOCS 8107310254
Download: ML20009F512 (2)

LER-1981-052, /03L-0:on 810619,nuclear Instrumentation Channel N-35 Observed to Be Reading Low & Erratic W/Unit Recovering from Turbine Trip.Caused by Failure of High Voltage Power Supply.Power Supply Replaced

Event date:
Report date:
3391981052R03 - NRC Website

text

U.S. NUCLEAR REGULATORY COMMISSION s

LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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LICENSEE CODE LICENSE NUMBER LICENSE TYPE CAT

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

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/ On June 19, 1981, with Unit II recovering fr:m a turbine trip - reactor trip at /

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/ 100% power, theNuclearInstrumentationChhnnelN-35wasobservedtobereading /

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/ low and erratically as neutron flux decreased subsequent to the reactor trip.

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/ Since another operable intermediate range channel was providing redundant flux

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/ indication, the public health and safety were not affected. This event report-

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

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SYSTEM

CAUSE

CAUSE COMP.

VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

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

CODE TYPE 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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/ The cause for the failure of the Intermediate Range Nuclear Instrumentation

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/ Channel was due to a failure of a high voltage pot er supply.

The power supply

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/ was replaced, tested and the channel restored to service.

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FACILITY METHOD OF l

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/ Trip Recovery /

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Operator Observation

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ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY (35)

LOCATION OF RELEASE (36)

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LZ/ (34)

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PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION (39)

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PERSONNEL INJURIES NUMBER DESCRIPTION (41)

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LOSS OF OR DAMAGE TO FACILITY (43)

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$7$h4 !okhS9 o

W. R. CARTWRIGHT PHONE (703) 894-5151 l

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Virginia Electric and Power Company North Anna Power Station, Unit #2

Attachment:

Page 1 of I Docket No. 50-339 s,

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Report No. LER 81-052/03L,0,

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Description of Event

On June 19, 1981, with Unit II recovering from a turbine trip-reactor trip caused by a failed main transformer, the nuclear instrumentation channel N-35 was reading low and erratically as neutron flux levels decreased towards the source range levels.

This inoperable neutron flux intermediate range is contrary to T.S. 3.3.1.1 and repartable' pursuant to T.S. 6.9.1.9.b.

Probable Consequences of Occurrence i

Since a redundant intermediate range channel was continuously available for flux indication, and two source range channels were available within minutes after the reactor trip, the public health

' and safety were not affected.

Cause of Event

C The, cause for the intermediate range channel to read low and erratically was due to a failed high voltage power supply. The reason for the power supply failing is unknown.

Immediate Corrective Action

s w

The immediate action was to monitor the operable intermediate

, range channel and to replace the failed power supply as soon as possible.

t s Scheduled Corrective Action No scheduled corrective action required.

Actions Taken to Prevent Recurrence No further action required.

Generic Implications There are no generic implications to this event.

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