05000322/LER-1987-009

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LER 87-009-01:on 870203,full Reactor Trip Occurred Due to Perturbation in Ref Leg.Caused by Spurious Low Level Reactor Pressure Vessel Water Level Signal.Existing Level & Pressure Transmitters Replaced W/Newer Models
ML20055C496
Person / Time
Site: Shoreham File:Long Island Lighting Company icon.png
Issue date: 05/16/1990
From: Schnaars G
LONG ISLAND LIGHTING CO.
To:
Shared Package
ML20055C491 List:
References
LER-87-009, LER-87-9, NUDOCS 9005240067
Download: ML20055C496 (4)
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LER-2087-009,
Event date:
Report date:
3222087009R00 - NRC Website
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text

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$v8Vi$3 TON Yt$ 199 res, compiers txPEC110 Sv04*ISSION DA ttl NO l l l ASSTAACT (Wr to f e00 speces d e eooro=# mere'r t,Presa sme e spece tyPewrerrea haes> Del On_ February 3, 1987 at 1555, a full reactor trip occurred due to a

' perturbation in the reference leg while an Instrument and Controls (I&C) technician was valving in a level transmitter. The plant was -

J in Operational Condition 4 (Cold Shutdown) with the mode switch in ohutdown and all rods inserted in the core. After maintenance had been performed on it, a technician was preparing to valve l 1B21*LT155A back into service. Using extreme caution, due to  :

recurring problems (refer to LERs85-006, 017, 020, 042,86-014, 1 021) with the reference and variable legs, the technician opened up the isolation valve causing a hydraulic oscillation in the line, i This action caused a momentary false low level signal, resulting in a full reactor trip. Operators verified the signal to be false and reset the trip. - Because of the recurring events, the event was anticipated and therefore deemed not reportable at the time, i However after a more careful review of the procedure used, on April 27, 1987, Plant Management determined that it was not part of a preplanned sequence and therefore reportable. The NRC was notified at this time per 10CFR50.72. This Supplemental Report is being i submitted to inform the Commission of the status of corrective I actions taken for this event. 1 2

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1 IDENTIFICATIOH__OF_THE EVENT l t

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-Full-Reactor Protection System (RPS) [JC) actuation due to l pertubation in reference leg caused by I&C technician valving in a

~ level transmitter, i

Event Date: 4/27/87 Report Date: S/16/90  :

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CONDITIQHS_ PRIOR'TO THE EYEHI t

Operational Condition 4 (Cold Shutdown)

ModerSwitch - Shutdown RPV Pressure.= 0'psig RPV Temperature = 114 Degrees F i All rods inserted in the core.

L' DESCRIPTION OF THE EVENT lj On-February 3, 1987 at 1344, a full RPS actuation occurred while an I&C technician was valving in a level transmitter (1B21*LT-155A) to

- the reference leg. The instrument had just been repaired under a L -Maintenance Work Request (an MWR) and was in the process of returning:the. instrument to service per. approved Station Procedure.

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1 41.012.02 (Reactor Vessel Reference Leg Instrument Removal and Return to Service).- The technician was fully aware of the potential for:a-reference les " bump" and a possible RPS actuation and was using extreme caution. Nevertheless, when he opened the isolation <

valve to. place the instrument back into service, a full RPS actuation occurred due to a spurious low RPV water level signal.

- Operators verified the signal as false, performed the Emergency Shutdown procedure (SP 29.010.01) and reset the trip.

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~When the actuation occurred, it was determined at the time that the svent was anticipated and therefore, not reportable per 10CFR50.72 and 73. . However, on April 23, 1987 the Plant review of Operations Committee (ROC) suggested that a more detailed investigation of the procedure was. warranted to determine if the " anticipated" actuation- .;

was part of a' pre planned sequence of events.

_On April'27, 1987 at 1100, it was determined by Plant Management that although the RPS actuation was anticipated and numerous caution ,

O statements were located in the return to service procedure (SP 41.012.02), it was not part of the preplanned procedu're and ,

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~therefore was reportable as an ESF actuation. At 1247, the NRC was notified.per 10CFR50.72. This Supplemental Report is being submitted to inform the Commission of the status of corrective '

actions taken for this event. .

CAUSE'OF THE EVENT The-perturbation in the reference leg occurred during the valve

. manipulations necessary to return.the instrument to service. The

cause is believed to be a combination of: 1. The ability of-these instrument sensing lines to transmit hydraulic transients, 2. The censitivity of these reactor level transmitters, and 3. .The l-

' grouping of both RPS logics on common sensing lines. The technician f involved was adequately trained and qualified to perform this work.

He was aware of the sensitivity of the reference leg instruments from direct. experience, required reading and discussions-at section meetings covering similar incidents and level instrumentation training established as a result of earlier incidents.

. ANALYSIS OF THE EVENT This event resulted in an unplanned actuation of the Reactor Protection System and is reportable per 10CFR50.73(a)(2)(iv). There .I is no safety significance to the event. The section in the procedure being used to return the instrument to service can only be  ;

performed while the plant is shutdown. The RPS operated as designed and operators carried out all required actions.

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0 l1 0l 4 0F 0l4 Ts<tn .-.. = - we w am,wnn CORRECTIVE AQIlGHS Because of the frequent number of incidents involving valving in of instruments to the reference and variable legs, it was decided to expedite a modification (SM 88-023) that was originally scheduled for implementation during the first refueling outage. This modification involves the replacement of existing level and pressure transmitters with newer ones. The new transmitters have a greater dampening effect and thus will be less susceptible to hydraulic oscillations produced when returning these instruments to service.

Implementation of this modification has been deferred indefinitely due to the New York - LILCO Shoreham Settlement Agreement.

ADDITIONAL _lHEQRMATION

a. Manuf.acturer_and_mndel_ number _cL.f. ailed _ component _Lal None
b. LEE _ numbers of orevious_similar__ events 3 LER 85-006, 017, 020, 042 ,

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86-014, 021 88-012 l l'

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i l N EC Ferm 306A (649)

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