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10 CFR 50.73.,

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PHILADELPHIA ELECTRIC COMPANY.

LIMERICK GE NC R ATING ST ATION

P. O. DO X A

S AN ATOG A PENNSYLV ANI A 19464

(#16) 337 1200 env.3000february 27, 1991

#.St .' " '." h .'." ' Docket No. 50-352License No. NPf-39. . . . . . . . . . . . . . . . . . . . . . . .

U.S. Nuclear Regulatory Commission'

Attn: Document Control DeskWashington, DC 20555

$UBJECT: Licensee Event ReportLimerick Generating 5tation - Unit 1

,

This LER reports an Engineered Safety feature actuation resulting f rom aspurious Divisicn 1 High Drywell Pressure (HDP) signal. The spurious HDP signaloccurred while an Instrumentation and Controls technician incorrectly restored apressure differential switch to operation.

Reference: Docket No. 50 352Report Number: 1 91-005Revision Number: 00Event Date: January 30, 1991Report Date: February ?7, 1991facility: Limerick Generating Station

P.O. Box A, Senatoga, PA 19464

This LER is being submitted pursuant to the requirements of 10 CfR50.73(a)(2)(iv).

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cc: T. T. Martin, Administrator, Region 1. USNRCT. J. Kenny, USNRC Senior Resident inspector, LGS

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,E ' ''' incorrect Restoration of a Pressure Differential Switch initiates a Spuricus HighDrywell Pressure Signal Causing an Engineered Safety Feature Actuation. ,,_

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On 1/30/91, during performance of a Surveillance Test (51) procedure, anInstrumentation and Controls (ILC) technician incorrectly restored a pressuredifferential switch (PDS) to operation causing a spurious Division 1 HighDrywell Pressure (HDP) signal. The spurious Division i HOP signal initiated anEngineered Safety feature (ESf) actuation, and various partial logic actuations.The ESF actuation and the partial logic actuations were immediately reset byOperations personnel. The actual consequences of this event were minimal. Had,

! this event occurred during an ope. tional condition in which the Reactorl

lPressure Vessel (RPV) pressure was below 455 psig, the potential for anunexpectedEmergencyCoreCoolingSystem(LCCS)injectionexisted. The primarycause of this event was proce t al non-compliance by an I&C technician. Asignificant contributino factor to the cause of this event was that the valvingsequence for restorin( the PDS is unusual and is reversed from the normal methodin which other PDM in the plant are restored. The !&C technicians involved inthis event were counseled regarding the requirement for strict proceduralcompliance. To prevent the recurrence of a similar event, the equalizing valvesforfour(4)subjectPOSSwillbeclosedandtheirrespectivevalvehandleswillbe removed. The associated ST procedures for these POSs will be revised toreflect this change. Until this corrective action is completed, warning labelshave been installed on the PDSs.

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Unit Conditions Prior to the Event:

Unit 1 Operational Condition was 1 (Power Operation) at 100% power icvel. Therewere no structures, systems or components out of service which contributed tothis event.

Description of the (vent:

On January 30, 1991, contractor employed Instrumentation and Controls (If,C)technicians were performing Surveillance Test (ST) Procedure S1-2-059-602-1," Channel A Calibration / functional Test of the Primary Containment Instrument Gasisolation on Low Differential Pressure." At 2202 hours, a technician opened theL0 side isolation valve to restore to operation pressure differential switchP05-59-106A(Ells:PDS)(seefigure1)whichresultedinaspuriousDivision1High Drywell Pressure (HDP) signal. The spurious HOP signal occurred whengreater than 1.68 psig was momentarily sensed by drywell pressure transmittersPT-42-lNOSOA, PT-42-1N094A, and PT-42-1N094E.

The spurious Division 1 HDP signal initiated the following Engineered SafetyFeature (ESF) actuation (Ells:JE),asdesigned.

o. A partial Group VIC (Primary Containment Sampling /Recombiner) PrimaryContainmentandReactorVesselisolationControlSystem(PCRVICS) actuation(Ells:JM) was generated by PT-42-lN050A. This resulted in the automaticclosure of SV-57-133, SV-57-183 and SV-57-191, three (3) Primary ContainmentH2/02CombustibleGasAnalyzer(CGA)(Ells:BB)samplelineisolationvalves.Thiscausedone(1)ofthetwo(2)operatingH2/02CGAstoisolateandrecirculate its air flow.

Additionally, the spurious HDP signal caused the following partial logicactuations to occur, as designed.

o AChannel'Al'ReactorProtectionSystem(RPS)(Ells:JC)halfscramactuation was generated by PT-42-lN050A.

o EmergencyCoreCoolingSystem(ECCS)partiallogicactuationsweregeneratedby PT-42-lN394A and PT-42-IN094E. No Residual Heat Removal (RHR) System(Ells:BO), Core Spray (CS) System (Ells:BM), Emergency Diesel Generator(EDGi (Ells:EK), or Automatic Depressurization System (ADS) actuationsoccurred due to the absence of a concurrent low Reactor Pressure vessel(RPV)pressuresignal(RPVpressurebelow455psig). |

The ESF actuation, and the partial logic actuations were reset at approximately i

2205 hours by Operations personnel. A four (4) hour notification was made tothe NRC at 0106 hours on January 31, 1991, in accordance with the requirementsof 10CFR50.72(b)(2)(ii) since the event resulted in the automatic actuation ofan ESF, This report is being submitted in accordance with the requirements of10CFR50.73(a)(2)(iv).

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Analysis of the Event:

The actual consequences of this event were minimal. All system actuations whichoccurred as a result of this event initiated as designed, and were immediatelyreset by Operations personnel. The redundant Primary Containment H2/02 CGA wasin operation during this event, and was monitoring the Primary Containmentatmosphere for H2/02 concentrations. No abnormal H2/02 concentrations were .

identified prior to, during, or following this event. There was no release ofradioactive material to the environment as a result of this event.

Had this event occurred during an operational condition in which the RPVpressure was below 455 psig, the potential for overfilling the RPV existed dueto an unexpected ECCS injection. In response to this type of transient.Operations personnel would have initic*ed Operational Transient (OT) Procedure,OT-110, '' Reactor High Level," which provides direction for mitigating anunexpected / unexplained rise in Reactor water level. Licensed operators receiverequalification training to review and practice responses to simulated planttransients of this type. The procedure, training, and operator actions wouldhave mitigated the consequ2nces of this type of event.

Cause of the Event:

The primary cause of this event was personnel error in that the I&C techniciansperforming the ST procedure failed to comply with the restoration section in theST procedure. The sections for testing and calibration of PDS-59-106A-in STprocedure ST-2-059-602-1 were satisfactorily completed and complied with by theI&C technicians; however, the section for the restoration of PDS-59-106A was notcomplied with by the l&C technicians.

-Additionally, the following contributing factors which lead to the cause of thisevent, are as follows,

o The valving sequence for restoring PDS-59-105A, PDS-59-1068 PDS-59-206A,and PDS-59-2068 is unusual and is reversed from the normal method in whichall other PDSs and transmitters in the plant are restored. Therefore, the' mind set' that the 1&C technicians had for normal restoration of PDSs andtransmitters in the plant affected how the 1&C technician manipulated thevalves for PDS-59-106A.

o There were no warning iabels on the four (4) PDSs discussed above. As aresult of a previous similar event reported in LER 1-90-025, warning labelswere to be added to the four (4) PD$s. These labels were to be used toalert I&C technicians of the PDSs unusual valving sequence. However, thelabels were not installed at the time this event occurred.

o The I&C technicians did not follow normal work practices and training.Normal work practice training instructs techniciat.s to work as a team untilan ST procedure is fully completed, and to use ' repeat backs' after actions

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in procedural steps of an ST are completed. During the restoration of PDS-,

) 59-106A,one(1)l&Ctechnicianwascleaninguptheworkareawhiletheother !&C technician was restoring the PDS. Therefore, the I&C techniciansdid not work together as a team during the restoration of the PDS, and no' repeat backs' were utilized..

In this event, after the PDS-59-106A was tested and calibrated, the H1 and LOsideisolationvalvesforPDS-59-106A(seefigure1)wereclosed,andtheequalizing valve was open. The H1 side to PDS-59-106A is connected to thePrimaryContainmentInstrumentGas(PC10)systemwhichwasinserviceoperatingat'100 psig pressure. Just prior to the restoration section in the 51 ,

procedure, a CAUTION statement exists which alerts l&C technicians to follow thevalving sequence for restoration of PDS-59-106A. In the restoration section of '

the ST procedure, the procedural steps direct the l&C technicians to restorePDS-59-106A by opening the L0 side isolation valve first, closing the equalizing

. valve second, and finally opening the H1 side isolation valve last. While one' (1)I&Ctechnicianwascleaninguptheworkarea,theotherl&Ctechnician,

i! having the ' mind set' to restore the PDS to operation using the normal valvingi sequence for restoring PDSs and transmitters in the plant, proceeded to restore

PDS-59-106A without the use of the ST procedure. The technician opened the HI;

side isolation valve to PDS-59-106A first, pressurizing thr,t instrument line upto the L0 side isolation valve to 100 psi. The equalizintj volve was thenclosed. Finally, the L0 side isolation valve was opened which released thepressurized air trapped between the equalizing valve an's the to side isolationvalve down the instrument line such that PT-42-lN050A, PT-42-lN094A, and PT-42-IN094E momentarily sensed the high pressure and initiated the EST actuation.,

Corrective Actions:

1. :The !&C technicians involved in this event were counseled regarding properwork practices'and the requirement for strict procedural compliance.

2. Warning labels to alert Ir.C technicians of the PD$s unusual valving sequencehave been installed on the four (4) POSs.

3.- This event will be discussed at the'next series of 1&C foreman Team Meetings-with emphasis placed on the need for procedural compliance. The I&C

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technicians involved in this event will present " Lessons Learned" from thisevent at each meeting. These meetings are expected to be completed by March23, 1991.

-4. ~P05 59-106A, PDS-59-1068.-PDS-59-206A, and PDS-S9-206B are the only PDSs inthe plant which have a restoration valving sequence that is reversed fromthe normal method-in which all other PDSs and transmitters in the plant arerestored. To prevent the recurrence of a similar-event, and to preclude the

_ potential for an unexpected ECCS injection when the RPV pressure is below455psig,theequalizingvalvesforthesefour(4)PDSswillbeclosedandtheir respective valve handles will be removed. All of the Unit I and 2

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; procedures which isolate and restort these PD$s will be revised to removethe actions which require the manipulation of-the equalizing valves. This

; specit.) valve manipulation is similar to other PDSs and transmittersexisting in the plant that have had their equalizing valve handles removed.ILC technicians are made aware of these special cases throu".h training, andthrough the proper valve sequencing that is included in the applicableprocedures. This corrective action is expected to be completed and .- -

implemented by April 1, 1991..

'After this corrective action has been completed, the warning labels whichwere installed on the PDS$ will no longer be necessary and will be removed.

Previous Similar Occurrences:,

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. LER 1-90-025 reported ESF actuations resulting from a spurious Loss of Coolant.

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Accident (LOCA)signalinitiatedbytheimpropervalvingrestorationofPDS~9-106A. As a result of LER 1-90-025, the ST procedures for ensuring that thesensing ilnes are clean for PDS-59-106A PDS-59 1068, PDS-59-206A, and PDS-69

! 206B were revised. These ST procedures are only performed during refuelingoperations. These revisions incorporated caution statements to alert I&Ctechnicians to follow the restoration valving sequence, and incorporated the.correct valving sequence for restoration of the PDSs. The ST procedures forensuring that.the sensing lines are clean do not test or calibrate the PDS$.Additionally, warning labels were to be added to the four-(4) PDSs; however, thelabeling was not completed at the time this event being reported occurred.

-All of the ST procedures which test or calibrate the PDSs (including ST-2-059-602-1 being reported in this event) contained the caution statements and thecorrectvalvingrestorationsequenceforthefour(4)PDSspriortothe-event'

reported in LER 1-90-025. The warning labels were-not considered to beessential.in preventing a similar event since the monthly ST procedures forcalibration and testing of these PDSs have been successfully and properlyperformed many times in the pa!.t by I&C technicians. However, had the warninglabels discussed above been installed prior to the occurrence of this event

; being reported, the spurious HDP signal caused by procedural non-compliance mayhave been prevented.

Tracking Codes: A2 failure to follow implementing procedures,

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