ML20029A825

LER 91-005-00:on 910130,pressure Differential Switch Restored Incorrectly,Causing Spurious Drywell Pressure Signal & ESF Actuation.Caused by Personnel Error.Personnel Counseled & Warning Labels added.W/910227 Ltr

ML20029A825
Person / Time
Site:	Limerick
Issue date:	02/27/1991
From:	Doering J, Madsen G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-005, LER-91-5, NUDOCS 9103040323
Download: ML20029A825 (7)

Text

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. 10 CFR 50.73 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.3000 february 27, 1991

1. .St .' " '." h .'." ' Docket No. 50-352

........................ License No. NPf-39 U.S. Nuclear Regulatory Commission '

Attn: Document Control Desk Washington, DC 20555

$UBJECT: Licensee Event Report Limerick Generating 5tation - Unit 1 ,

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

Reference:

Docket No. 50 352 Report Number: 1 91-005 Revision Number: 00 Event Date: January 30, 1991 Report Date: February ?7, 1991 facility: Limerick Generating Station P.O. Box A, Senatoga, PA 19464 This LER is being submitted pursuant to the requirements of 10 CfR 50.73(a)(2)(iv).

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Very truly yours,

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}{l,l. 0 %m DMS:rgs cc: T. T. Martin, Administrator, Region 1. USNRC T. J. Kenny, USNRC Senior Resident inspector, LGS 7,[g3Og{,g(( M g2 )

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

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On 1/30/91, during performance of a Surveillance Test (51) procedure, an Instrumentation and Controls (ILC) technician incorrectly restored a pressure differential switch (PDS) to operation causing a spurious Division 1 High Drywell Pressure (HDP) signal. The spurious Division i HOP signal initiated an Engineered Safety feature (ESf) actuation, and various partial logic actuations.

The ESF actuation and the partial logic actuations were immediately reset by Operations personnel. The actual consequences of this event were minimal. Had

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

Pressure Vessel (RPV) pressure was below 455 psig, the potential for an l unexpectedEmergencyCoreCoolingSystem(LCCS)injectionexisted. The primary cause of this event was proce t al non-compliance by an I&C technician. A significant contributino factor to the cause of this event was that the valving sequence for restorin( the PDS is unusual and is reversed from the normal method in which other PDM in the plant are restored. The !&C technicians involved in this event were counseled regarding the requirement for strict procedural compliance. To prevent the recurrence of a similar event, the equalizing valves forfour(4)subjectPOSSwillbeclosedandtheirrespectivevalvehandleswill be removed. The associated ST procedures for these POSs will be revised to reflect this change. Until this corrective action is completed, warning labels have been installed on the PDSs.

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o lo o 12 o' o it Unit Conditions Prior to the Event:

Unit 1 Operational Condition was 1 (Power Operation) at 100% power icvel. There were no structures, systems or components out of service which contributed to this 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 Gas isolation on Low Differential Pressure." At 2202 hours0.0255 days <br />0.612 hours <br />0.00364 weeks <br />8.37861e-4 months <br />, a technician opened the L0 side isolation valve to restore to operation pressure differential switch P05-59-106A(Ells:PDS)(seefigure1)whichresultedinaspuriousDivision1 High Drywell Pressure (HDP) signal. The spurious HOP signal occurred when greater than 1.68 psig was momentarily sensed by drywell pressure transmitters PT-42-lNOSOA, PT-42-1N094A, and PT-42-1N094E.

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

o. A partial Group VIC (Primary Containment Sampling /Recombiner) Primary ContainmentandReactorVesselisolationControlSystem(PCRVICS) actuation (Ells:JM) was generated by PT-42-lN050A. This resulted in the automatic closure of SV-57-133, SV-57-183 and SV-57-191, three (3) Primary Containment H2/02CombustibleGasAnalyzer(CGA)(Ells:BB)samplelineisolationvalves.

Thiscausedone(1)ofthetwo(2)operatingH2/02CGAstoisolateand recirculate its air flow.

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

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

o EmergencyCoreCoolingSystem(ECCS)partiallogicactuationsweregenerated by 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) actuations occurred due to the absence of a concurrent low Reactor Pressure vessel (RPV)pressuresignal(RPVpressurebelow455psig). l The ESF actuation, and the partial logic actuations were reset at approximately i 2205 hours0.0255 days <br />0.613 hours <br />0.00365 weeks <br />8.390025e-4 months <br /> by Operations personnel. A four (4) hour notification was made to the NRC at 0106 hours0.00123 days <br />0.0294 hours <br />1.752645e-4 weeks <br />4.0333e-5 months <br /> on January 31, 1991, in accordance with the requirements of 10CFR50.72(b)(2)(ii) since the event resulted in the automatic actuation of an ESF, This report is being submitted in accordance with the requirements of 10CFR50.73(a)(2)(iv).

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The actual consequences of this event were minimal. All system actuations which occurred as a result of this event initiated as designed, and were immediately reset by Operations personnel. The redundant Primary Containment H2/02 CGA was in operation during this event, and was monitoring the Primary Containment atmosphere for H2/02 concentrations. No abnormal H2/02 concentrations were .

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

Had this event occurred during an operational condition in which the RPV pressure was below 455 psig, the potential for overfilling the RPV existed due to 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 an unexpected / unexplained rise in Reactor water level. Licensed operators receive requalification training to review and practice responses to simulated plant transients of this type. The procedure, training, and operator actions would have 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 technicians performing the ST procedure failed to comply with the restoration section in the ST procedure. The sections for testing and calibration of PDS-59-106A-in ST procedure ST-2-059-602-1 were satisfactorily completed and complied with by the I&C technicians; however, the section for the restoration of PDS-59-106A was not complied with by the l&C technicians.

-Additionally, the following contributing factors which lead to the cause of this event, 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 which all other PDSs and transmitters in the plant are restored. Therefore, the

' mind set' that the 1&C technicians had for normal restoration of PDSs and transmitters in the plant affected how the 1&C technician manipulated the valves for PDS-59-106A.

o There were no warning iabels on the four (4) PDSs discussed above. As a result of a previous similar event reported in LER 1-90-025, warning labels were to be added to the four (4) PD$s. These labels were to be used to alert I&C technicians of the PDSs unusual valving sequence. However, the labels 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 until an ST procedure is fully completed, and to use ' repeat backs' after actions e

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

) 59-106A,one(1)l&Ctechnicianwascleaninguptheworkareawhilethe other !&C technician was restoring the PDS. Therefore, the I&C technicians did 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 LO sideisolationvalvesforPDS-59-106A(seefigure1)wereclosed,andthe equalizing valve was open. The H1 side to PDS-59-106A is connected to the PrimaryContainmentInstrumentGas(PC10)systemwhichwasinserviceoperating at'100 psig pressure. Just prior to the restoration section in the 51 ,

procedure, a CAUTION statement exists which alerts l&C technicians to follow the valving sequence for restoration of PDS-59-106A. In the restoration section of the ST procedure, the procedural steps direct the l&C technicians to restore PDS-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 valving i 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 up to the L0 side isolation valve to 100 psi. The equalizintj volve was then closed. Finally, the L0 side isolation valve was opened which released the pressurized air trapped between the equalizing valve an's the to side isolation valve down the instrument line such that PT-42-lN050A, PT-42-lN094A, and PT ,

IN094E momentarily sensed the high pressure and initiated the EST actuation.

Corrective Actions:

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

2. Warning labels to alert Ir.C technicians of the PD$s unusual valving sequence have 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 ,

technicians involved in this event will present " Lessons Learned" from this event at each meeting. These meetings are expected to be completed by March 23, 1991.

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

_ potential for an unexpected ECCS injection when the RPV pressure is below 455psig,theequalizingvalvesforthesefour(4)PDSswillbeclosedand their respective valve handles will be removed. All of the Unit I and 2 g...nu

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

specit.) valve manipulation is similar to other PDSs and transmitters existing in the plant that have had their equalizing valve handles removed.

ILC technicians are made aware of these special cases throu".h training, and through the proper valve sequencing that is included in the applicable procedures. This corrective action is expected to be completed and . .

implemented by April 1, 1991.

After this corrective action has been completed, the warning labels which were 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 Accident (LOCA)signalinitiatedbytheimpropervalvingrestorationofPDS~9-106A. As a result of LER 1-90-025, the ST procedures for ensuring that the sensing 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 refueling operations. These revisions incorporated caution statements to alert I&C technicians to follow the restoration valving sequence, and incorporated the.

correct valving sequence for restoration of the PDSs. The ST procedures for ensuring 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, the labeling 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 the correctvalvingrestorationsequenceforthefour(4)PDSspriortothe-event reported in LER 1-90-025. The warning labels were-not considered to be essential.in preventing a similar event since the monthly ST procedures for calibration and testing of these PDSs have been successfully and properly performed many times in the pa!.t by I&C technicians. However, had the warning labels discussed above been installed prior to the occurrence of this event

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

Tracking Codes: A2 failure to follow implementing procedures ,

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