ML19354D834

LER 89-021-01:on 890922,ref Leg of Level Instrument Vented to Test Equipment,Causing False High Reactor Pressure Vessel Signal.Caused by Trip of Turbine Generator Resulting in Scram.Excess Flow Check Valve depressurized.W/900112 Ltr

ML19354D834
Person / Time
Site:	Oyster Creek
Issue date:	01/12/1990
From:	Fitzpatrick E, Godknecht M GENERAL PUBLIC UTILITIES CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-021, NUDOCS 9001220235
Download: ML19354D834 (4)

Text

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1 GPU Nuclear Corporation Nuclear.

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Forked River,New Jersey 087310388 1

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Writer's Direct Dial Number: ' '

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January 12, 1990  ;

i U.S. Nuclear Regulatory Commission >

Attn: -Document Control Desk j Washington, D.C.; 20555 i

. Dear Sir '

Subject:

. Oystier Creek Nuclear Generating Station.

Docket No'.' 50-219-Licensee Event Report;  ;

l This letter forwards one (1) copy of. Licensee Event Report (LER) No,'.89-021,  !

Revision 1.- This-revision provides additional.information which is indicated '

a by a bar in the right hand margin.. f Very truly yours, E.EE Fit trick j Vice-President and Director Oyster Creek $

EEF/BDeM(3)-LTRS/$c Enclosure

,- cca Mr. William T. Russell, Administrator Region i U.S. Nuclear Regulatory Commission i 475 Allendale Road King of Prusola, PA 19406 NRC Resident Inspector I. Oyster Creek Nuclear Generating Station

'Mr. Alexander Dromerick i U.S. Nuclear-Regulatory Commission ,

Mail Station P1-137 ,

Washington, DC 20555 i

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GPU Nucleat Corporation is a subsidiary of the GencialPublic Utilities Corporation L- ,.

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- LICENSEE EVENT REPORT (LER)

Ps.CILITY Naast til 00CRET NueEB4Rtil "W W I Ovrter creek Unit 1 0is1010l01 l l 1l0FlO!9 TITLI E41 Reactor Scram due to Turbine Trip as a Result of Personnel Error During Surveillance Test EVENT DATE (Si LER NUAGER 181 RSPORT DATE 17) OTMSR F ACILITIES INVOLVED ISI MONTH DAY YEAR YEAR A' MONTM DAY YEAR F ACILITV hAMit DOCKET NVMetRIS)

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l On September 22, 1989, at approximately 1418 hours0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.39549e-4 months <br />, mechanical test equipment was inadvertently left connected to one of the reactor pressure vessel (RPV) water level instruments after costing was complete. While being placed back in service, the reference leg of the instrument was vented to the test equipment causing a f alse high RPV water level cignal to be generated in all five level instruments attached to that common reference leg. The false high RPV water level caused a trip of the turbine generator which resulted in a reactor scram. The technician performing the-valve manipulation recognized the problem and closed the root valve. The cause of this event was personnel error since the test equipment was not removed as required by the surveillance procedure. This event had minimal safety significance because the Reactor Protection System is designed to protect the reactor from any turbine trip condition, and the excess flow check valves in the instrument line would have prevented any significant loss of coolant. All engineered safety features would have functioned normally due to redundant RPV level instrumentation. All instruments involved in this event were calibration checked to ensure no problems had resulted from the momentary depressurization. The technicians involved in this event were counseled.

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UCENSEE EVENT REP 2RT-(LER) TEXT CONTINUATION EMPIRES B/3146 9Acettiv feaadt H6 ooCRET NURSSR th Lin NUssetR tel PAGE W YEAR Nn '

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IThis event occurred on SeptemberI22,.1989, at'approximately 1418 hours0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.39549e-4 months <br />.

f IDENTIFICATION OF OCCURRENCE [

l While performing a surveillance on the reactor pressure vessel (RPV) level .

instrumentation (EIIS-JC-LT). mechanical test equipment was inadvertently left.

connected to one of the level instruments, contrary to procedure requirements, after tssting of that instrument was, complete. While the. instrument was betng placed back:

in service, the' reference leg of the instrument was vented to the installed tout squipment depressurizing that leg of the instrument loop and causing a highiRPV l water level signal to be generated in all five level instruments attached to that loop. The high RPV' water level signals caused a trip of the turbine generator (EIIS TA) which resulted in an anticipatory reactor scram on turbine'stop valve closure.

( The closure of the turbine stop valves also caused a reactor pressure spike of 1077 p2ig which resulted in the following safety system actuations: ' Initiation of both isolation condensers (EIIS-BL) and electromatic relief valves (EMRV) A,B,D and E (EIIS-JERV) and an automatic trip of the reactor recirculation pumps-(EIIS-ADP).

The turbine trip also resulted in an automatic start of the emergency diesel gsnsrators (EIIS-EKDG). All safety systems / components-operated as designed. This l svent is considered' reportable under.10CFn50.73(a)(2)(iv).

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CONDITIONS PRIOR TO OCCURRENCE The reactor was at 99.6% power, with a generator load of approximately 636 megawatts electric. i DESCRIPTION OF OCCURRENCE While performing a Reactor High/ Low Level Instrument Test and Calibration surveillance, two instrument and control-(I&C) technicians missed-a step in the procedure while returning an instrument to service. .The missed step required that the installed test equipment be removed and the test plugs be reinstalled on the instrument. When the instrument reference leg root valve was= opened in accordance with the procedure, the reference leg of this and four other instruments was vented to the installed test equipment. All-five instruments sensed.a false high water level condition due to the differential pressure set up by this event. This false high RPV water level condition energized the turbine generator' trip circuit closing ths turbine stop valves. Because reactor power was greater than 40%, an anticipatory scram signal was generated by the closure of the turbine stop valves. '

H*aring the sound of high pressure being vented, the I&C Technician performing the -

valve manipulation recognized the problem and closed the root valve. The I&C Tschnicians then notified the Control Room of what had happened during the surveillance.

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vinten . .M w anca anna m m KPPARENT CAUSE OF OCCURRENCE i

The cause of this event has been determined to be personnel error. .The I&C  :

Tschnicians failed to perform the steps as required-by the surveillance procedure. j Bicause the test equipment.was not removed and test plugs were not reinutalled, the ,

reference leg of.five RPV water level instruments was vented to the test equipment, cstting up a false RPV high water condition in those five instruments. High level ,

signals from 2 of the 5 instruments resulted in a turbine: trip and subsequent .

l reactor scram.

l l ANALYSIS OF OCCURRENCE AND SAFETY SIGNIFICANCE +

The protective circuitry of both the Reactor Protection System and the turbine.

gznerator responded as designed during this event. The excess. flow check valves in.

the instrument line that was depressurized would have prevented any significant loss" l

of coolant even if the I&C technician had not recognized the problem.and immediately ,

closed the instrument root valve he was opening.

This event is determined to have m'inimal safety significance because a. turbine trip .r from 100% power is within the design of the Reactor Protection system (EIIS-JC) and the instrument line excess flow check. valves would have prevented any significant loss of coolant even if the technician had not immediately closed the root valve.

The Engineered Safety Features (EIIScJE) receiving signals from the affected RPV level instrumentation would have-functioned normally because of the redundant' level instruments sensing RPV level via different instrument reference legs.

CORRECTIVE ACTION

1. The surveillanco was completed satisfactorily and all five instruments involved in this event were calibration checked to ensure no problems had resulted'from the momentary depressurization.

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2. The exceos flow check valve for the instrument line depressurized was verified.

to be open.

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3. The two I&C technicians involved in this incident have been counseled and this event report will be made required reading for all I&C technicians.

l SIMILAR EVENTS l LER 87-45 SGTS Initiation Due to Water Accumulation in AOG System.

LER 88-08 SGTS Initiation by Procedural Noncompliances. ,

I g oa n

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