ML19327B496

LER 89-021-00:on 890922,false High Reactor Pressure Vessel Water Level Caused Turbine Generator Trip & Reactor Scram. Caused by Personnel Not Following Surveillance Procedure.All Involved Instruments Calibr checked.W/891023 Ltr

ML19327B496
Person / Time
Site:	Oyster Creek
Issue date:	09/23/1989
From:	Fitzpatrick E, Godknecht M GENERAL PUBLIC UTILITIES CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-021, LER-89-21, NUDOCS 8910310313
Download: ML19327B496 (4)

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GPU Numiser Corporation g Post Office Box 388 Route 9 South Forked River, New Jersey 087310388

' 609 971 4000 ,

Wnter's Direct Dial Number: j October 23, 1989 j i

t U.s. Nuclear Regulatory Conunission  ;

Document Control Desk  ;

Washington, DC 20555 Dear Sir i i

r Subjects Oyster Creek Nuclear Generating Station .

Docket No. 50-219 '

Licensee Event Report i

This' letter forwards one (1) copy of Licensee Event Report (LER)  ;

No.89-021. ,

Very truly yours, I I

E.E. Fitspatrick fl * /0 f.23 f$ 9

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• Vice President G Director i Oyster Creek i

'EEF/BDEM:jc j Enclosure  ;

i ces Mr. William T. Russell .;

Region-I $

U.S. Nuclear Regulatory Couunission t 475 Allendale Road King of Prussia, PA 19406 f Mr. Alexander W.' Dromerick U.S. Nuclear Regulatory Connission f Washington, DC 20555 j n

NRC Resident Inspector '

oyster Creek Nuclear Generating Station i

8910310313 89o923 j gDR ADOCK osco3 9 GPU Nuclear Corporation is a subsidiary of General Public Utilites Corporation Yl (

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aseenae,a -.. = ... _ . . - ., i e 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 testing was complete. While being placed back in service, the reference leg of the instrument was vented to the test equipment causing a false high RPV water level signal 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 )

t'urbine generator which resulted in a reactor scram. The technician performing the )

valve manipulation recognized the problem and closed the root valve. The cause of l 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 l 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 )

i prevented any significant loss of coolant. All engineered safety features would I have functioned normally due to redundant RPV level instrumentation. All l instruments involved in this event were calibration checked to ensure no problems j had resulted from the momentary depressurization. The technicians involved in this j event were ec+unseled. l l

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mas s am amm e nne. na samme mw amm mpw nn DATE OF OCCURRENCE l This event occurred on september 22, 1989, at approximately 1418 hours0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.39549e-4 months <br />.

IDENTIFICATION.0F OCCURRENCE I While performing a surveillance on the reactor pressure vessel (RPV) level instramentation (EIIS-JC-LT), mechanical test equipment was inadvertently left  ;

connected to one of the level instruments, contrary to procedure requirements, after  ;

testing of that instrument was complete. While the instrument was being placed back in service, the reference leg of the instrument.was vented to the installed test .

equipment depressurizing that leg of the instrument loop and causing a high RPV  ;

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, i This event is considered reportable under 10CFR50.73(a)(2)(iv). j CONDITIONS PRlQR TO OCCURRENCE t

The reactor was at 99.6% power, with a generator load of approximately 636 megawatts

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electric. ,

DESCREPTION 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  ;

i to the installed test equipment. All five instruments sensed a falso 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 i the turbine stop valves. Because reactor power was greater than 40%, an -

anticipatory scram signal was generated by the closure of the turbine stop valves. l Hearing the sound of high pressure being vented, the IGC Technician performing the valve manipulation recognized the problem and closed the root valve. The IEC '

Technicians then notified the Control Room of what had happened during the }

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surveillance.

APPARENT CAUSE OF OCCURRERQg ,

The cause of this event has been determined to be personnel error. The IEC .

Technicians failed to perform the steps as required by the surveillance procedure.

Because the test equipment was not removed and test plugs were not reinstallsd, the reference leg of five RPV water level instruments was vented to the test equipment, setting up a falso RPV high water condition in those five instruments. High level signals from 2 of the 5 instruments resulted in a turbine trip and subsequent reactor scram.

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MALYSIS OF OCCURRENCE AND SAFETY RIGNIFICANCE The protective circuitry of both the Reactor Protection System and the turbine  !

generator responded as designed during this event. The excess flow check valves in the instrument line that was depressurized would have prevented any significant loss of coolant even if the I&c technician had not recognized the problem and inunediately i closed the instrument root valve he was opening. I

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This event is determined to have minimal safety significance because a turbine trip 1 from 100% power is within the design of the Reactor Protection system (E!!S-JC) and I

( the instrument line excess flow check valves would have prevented any significant i 'hos of coolant even if the technician had not immediately closed the root valve. )

The Engineered Safety Features (EIIS-JE) receiving signals from the affected RPV  ;

leve.1 instrumentation would have functioned normally because of the redundant level instraments sensing RPV level via different instrument reference legs.

CORRECTIVE ACTION j

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

l' 2. The excess flow check valve for the instrument line depressurized was verified l to be open.

3. The two I&c technicians involved in this incident have been counseled and this  ;

l' event report will be made required reading for all I&c technicians.  ;

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l SIMILAR EVENTS

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( LER 87-45 SGTS Initiation Due to Water Accumulation in AOG System.

) LER 88-08 SGTS Initiation by Procedural Noncompliances. 1 l

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