ACCELERATED D UTION DEMONSTP TION SYSTEMC

REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR.8912190264 DOC DATE. 89/12/15 NOTARIZED. NO DOCKET gFACIL:STN-50-529 Palo Verde Nuclear Station, Unit .2, Arizona Publi 05000529AUTH.NAME AUTHOR AFFILIATION

SHRIVER,T.D. Arizona Public Service Co. (formerly Arizona Nuclear PowerLEVINE,J.M. Arizona Public Service Co. (formerly Arizona Nuclear Power

RECIP.NAME RECIPIENT AFFILIATION

05000529

SUBJECT: LER 89-003-01:on 890216,reactor trip due to low steamgenerator level.

W/8 . ltr.DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.NOTES:Standardized plant.

RECIPIENTID CODE/NAME

PD5 LACHAN,T

INTERNAL: ACRS MICHELSONACRS WYLIEAEOD/DSP/TPABDEDRONRR/DET/EMEB9H3NRR/DLPQ/LHFB11NRR/DOEA/OEAB11NRR/DST/SELB 8DNRR/DST/SPLB8D1NUDOCS-ABSTRACTRES/DSIR/EIB

EXTERNAL EG&G WILLIAMSi SLPDRNSIC MAYS,GNUDOCS FULL TXT

NOTES:

COPIESLTTR ENCL1,1

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RECIPIENTID CODE/NAME

PD5 PDDAVIS,M.

ACRS MOELLER.AEOD/DOAAEOD/ROAB/DSPNRR/DET/ECMB 9HNRR/DET/ESGB 8DNRR/DLPQ/LPEB10NRR/DREP/PRPB11NRR/DST/SICB 7EN /DST/NRXB 8EREG FILE

~~L ST LOBBY WARDNRC PDRNSZC MURPHY,G.'"A

COPIESLTTR ENCL

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1 11 11 1

NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTEl CONTACT THE.DOCUMENT CONTROL DESk,ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAMEFROM DISTRIBUTION

FULL TEXT CONVERSION REQU1REDTOTAL, NUMBER OF COPIES REQUIRED: LTTR 40 ENCL 40'

ll

JAMES M. LEVINEVICE PRESIDENT

NUCLEAR PRODUCTIDM

Arizona Public Service CompanyPALO VERDE NUCLEAR GENERATING STATION

P.O. BOX 52034 ~ PHOENIX. ARIZONA85072-2034

192-00603-JML/TDS/RKRDecember 15, 1989

U. S. Nuclear Regulatory CommissionNRC Document Control DeskWashington, D.C. 20555

Dear Sirs:

Sub) ect: Palo Verde Nuclear 'Generating Station (PVNGS)Unit 2Docket No. STN 50-529 (License NPF-51)Licensee Event Report'89-003-01File: 89-020-404

Attached please find Supplement Number 1 to Licensee Event Report (LER) No.89-003-00 prepared and submitted pursuant to the requirements of 10CFR 50.73.This supplement is being provided to revise the corrective actions. A HumanPerformance Evaluation System (HPES) analysis is not being performed aspreviously stated. Based on the extensive corrective actions described inthis report the HPES was determined not to be required. In accordance with10CFR 50.73(d), we are herewith forwarding a copy of this 'report to theRegional Administrator of the Region V Office.

If you have any questions, please contact T. D. Shriver, Compliance Manager at(602) 393-2521.

Very truly yours,

JML/TDS/RKR/kj

Attachment

CC'. F. ConwayE. E. Van BruntJ. B. MartinT. J. PolichM. J. DavisA. C. GehrINPO Records Center

(all w/a)

p~g,S'~12190260

e'er g 21,PDR ADOCK O=LI8O5S pbc

NRC FORM 366(669)

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U.S, NUCLEAR REGULATORY COMMISSION

LICENSEE EVENT REPORT (LER)

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PAGE 3DOCKET NUMBER (2)

Palo Verde Unit 2TITLE (4)

o 5 o o o 52 9> oFl 5

Reactor Trip Due to Low Steam Generator Level

MONTH DAY YEAR

EVENT DATE ISI

YEAR

LER NUMBER (5)

AS SEQUENTIALNUMBER yT

REPORT DATE (7)

DAY YEARMONTHNUMBER

N/A

FACILITYNAMES DOCKET NUMBER(s)

0 5 0 0 0

OTHER FACILITIES INVOLVED (SI

0 2 1 6 89 8 9 0 0 3 01 12 1 5 8 9 N/A 0 5 0 0 0

OP E RATINGMODE (9) 1

POWERLEYEL

1 0 0

20.402 (b I

20.406( ~ l(1 )(il

20.405( ~ ) (I ) (9)

20.405( ~ I (I l(iiil

20.405(e) (I l(le)

20.406 (e) Ill(e)

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5(L36(c) (21

60.73(e) (2)(i)

50.73(el(2)(9)

50.73(e ) (2) (iiil

LICENSEE CONTACT FOR THIS LER (12)

60.73(el(2) (ie)

50.73(e)(2)(el

50.73(el(2) (eit)

60.73(el(2)Niiil(A)

50.73(e) (2)(eBII(B)

50.73( ~ I(2)(xl

THIS REPORT IS SUBMITTED PURSUANT TO THE RLQVIREMENTS OF 10 CFR ()t /Check one oi mote of the follonenp/ (11

73.71(b)

73.71(cl

OTHER /Specify tn Abtttecrbelow end ln TexL HRC Foim

Special Report2-SR-89-003

NAME

Timothy D. Shriver, Compliance Hanager.

TELEPHONE NUMBER

AREA CODE

6 02 39 3 — 25 21COMPLETE ONE LINE FOR EACH COMPONENT FAILURE OESCAIBEO IN THIS REPORT (13)

CAUSE SYSTFM COMPONENT MANUFACTUBER

REPORTABLE,,TO NPRDS ~&A'YSTEM

COMPONENTMANUFAC.

TVRER

WRRK4~Ã<

SUPPLEMENTAL REPORT EXPECTED (14)EXPECTS'0

SUBMISSIONDATE RSI

MONTH OAY YEAR

YES /lfyet, Cnmpfete EXPECTED St/SM/SS/DH DATE/ NO

AK appr'oximatety 595 (fat onVebNruary 16, 1989, Palo Verde Unit 2 was in Hode1 (POWER OPERATION) at approximately 100 percent power when a FeedwaterControl System (FWCS) malfunction resulted in a reactor trip due to low levelin Steam Generator (SG) number 1.

Immediately prior to the trip the Control Room staff observed both SG levelsdecreasing. Both master controller outputs were cycling full scale. SG

number 1 economizer valve was fully shut and SG number 2 economizer. valve was10 percent open. A Control Room Operator placed SG number 1 economizer valvein manual and inserted approximately 17 percent open demand when the reactortripped.

Immediately following the trip an Auxiliary Feedwater Actuation Signal wasinitiated. At approximately 0345 HST a Safety Injection Actuation Signal(SIAS)/Containment Isolation Actuation Signal (CIAS) was generated due to theovercooling of the Reactor Coolant System. SG number 1 level continued toincrease and at approximately 0347 HST a Hain Steam Isolation Signal -wasreceived and terminated the cooldown. The cause of the event was a smallamount of debris in the restrictor on the vertical relay within the economizervalve pneumatic positioner. Immediate corrective action taken was to replacethe pneumatic relays in both FWCS's.

This submittal also provides Special Report 2-SR-89-003 in accordance withTechnical Specification 3.5.2 ACTION b.

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FACILITYNAME (1) DOCKET NUMBER (2) LER NUMBER (6)

SII'O SEOUENTIALNUMSER 'Nl

REVISIONNUMSEVI

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Pal o Verde Uni t 2TEXT (IImove opooe b veevvded, Ivse Rddo'onol HRC Fovvtv 35SI('sl (12)

o s o o o 52 98 9 003 01 02 oF1 5

I. DESCRIPTION OF WHAT OCCURRED:

A. Initial Conditions:

B.

At approximately 0345 MST on February 16, 1989, Palo Verde Unit 2was in Mode 1 (POWER OPERATION) at approximately 100 percent powerwhen a Feedwater Control System (FWCS)(JB) malfunction resulted ina reactor (RCT)(AC) trip.Reportable Event Description (Including Dates and ApproximateTimes of Major Occurrences):

Event Classification: Any event or condition that resulted inmanual or automatic actuation of anyEngineered Safety Feature (ESF)(JE),including the Reactor Protection System(RPS)(JC).

At approximately 0345 HST on February 16,, 1989, Palo Verde Unit 2was operating in Mode 1 (POWER OPERATION) at approximately 100percent power when an FWCS malfunction resulted in a reactor tripon Low Steam Generator (SG)(AB) number 1 level and an AuxiliaryFeedwater Actuation Signal (AFAS)(BA) actuation. Subsequent to thetrip, number 1 SG was overfed using main feedwater resulting in aSafety Injection Actuation Signal (SIAS)(JE), Containment IsolationActuation Signal (CIAS)(JE), and Main Steam 'Isolation Signal(HSIS)(JE). A Notification of Unusual Event (NUE) was declared at0352 MST due to SIAS actuation and was terminated at 0449 MST whenthe SIAS was reset.

Prior to the event, on February 13, 1989 during Hain Turbine(TRB)(TA) Stop valve (V)(TA) testing, an FWCS transient occurred.The number 1 economizer valve (FCV)(SJ) started to close inresponse to the testing but subsequently appeared to stick atapproximately 35 percent open. The feedwater pump (FWP)(P)(SJ)speed increased to restore SG level. Manual control of the RB"

feedpump was used to gain control of feedwater flow. The SG levelfell to a low of approximately 5 percent narrow range (NR). OnceSG level was regained (approximately 55 percent NR), the operatorreturned feedpump speed to automatic control and took manualcontrol of the economizer valve. The valve subsequently respondedproperly. The secondary operator (utility, licensed) manuallystroked the valve approximately 10 to 15 percent open and closedfrom the 70 percent open position and then restored the valve toits normal position of approximately 85 percent open for 100percent power operation. With all components returned toautomatic, all systems functioned properly. During the transient,oscillations from 50 to 85 percent in the master controller output

NRC Fovvn 355A (54)9)

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FACILITYNAME (1)

Palo Verde Unit 2TEXT /I/mort 4/Not 6I rttoirtd. Vtt odd)dont//VRC Form 3664'4/ (17)

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for FWCS number 1 were observed. These oscillations in the mastercontroller would be expected for the transient induced in thesystem by the erratic operation of the number 1 economizer valve.The opportunity to learn from the transient on February 13, 1989was reduced because the Temporary Data Acquisition System(TDAS)(Ig) data was not reviewed. The Shift Technical Advisor(STA)(utility, non-licensed) did discuss the transient with theShift Supervisor (utility, licensed), but he inferred from thatconversation that there would be no need for the transient data andproceeded to reinitialize the data disk. This reinitialization isdone every 12 hours. When the data disk was reinitialized, thespecific behavior of the number 1 economizer valve in the February13, 1989 event was lost. Had this information been retained it mayhave aided in the troubleshooting. It was also noted that the STAwas not called immediately when the transient occurred.

After several discussions involving the Plant Hanager (utility,non-licensed), System Engineer (utility, non-licensed), andOperations Standard Advisor (utility non-licensed), a work requestwas generated to troubleshoot FWCS number 1. Troubleshooting theFWCS was made based on the following considerations:

1) There were no apparent problems maintaining SG level.

2) There were no apparent problems with the mastercontroller in automatic due to the observed stable FWCSconditions since the February 13, 1989 transient.

3) The decision was made to instrument both FWCSs andinitiate small perturbations by controller setpointchanges, stop valve testing or initiating rapid steamgenerator blowdowns during the troubleshooting to observesystem response.

Additionally, the decision was made not to perform any high riskPreventive Haintenance Tasks or initiate the scheduled high rate SGblowdown until the system was instrumented.

A work order was generated to perform the troubleshooting (measurethe input and output of the economizer valve signal characterizermodule, SCH) based on guidance by the System Engineer. The SystemEngineer would personally direct the troubleshooting work orderwhich would also require Shift Supervisor concurrence. It wouldalso require that the associated parameter (i.e. the economizervalve) be placed in manual when connecting the recorder to the SCH.

Through discussions with the System Engineer and the Instrument andControl (I&C) Supervisor (utility, non-licensed), it was decided to

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LER NUMBER (6)

SEQUENTIAL Mr REVOK>NNUMSE4 CC% NUMEE4

Palo Verde Unit 2TEXT /I/movp a»EP IJ Tuuut)ud, u44 Pddr'0'phu/IVRC Foun 366AB/(17)

o s o o o 52 9 8 9 00 3 —01 0 4 OF 1 5

utilize a standard four-channel Gould recorder fortroubleshooting. However, due to mechanical problems with therecorder, it could not be used. After further discussions betweenI&C personnel and the System Engineer it was determined to use aneight-channel digital recorder.

The digital system recorder was obtained from Heasuring and TestEquipment (HKTE) with prefabricated cables which included triaxialconnectors, coaxial wire, coaxial signal wire connector, andindividual wires for connection to the system.

At approximately 1830 HST on February 15, 1989, the eight-penDigital Recorder System was connected to the number 1 FWCS. Thedigital recorder has an internal circuit wherein the inner shieldsof the triax connectors are connected together. This is differentthan the standard four-channel recorder and was not recognized bythe System Engineer present or the ILC Technician (utility,non-licensed). This resulted in the SCH for SG number 1 economizervalve being shorted from input to output through the recorder.With a reasonably stable SG level, the internally cross-connectedrecorder had very little impact on the master controller output(i.e. the resulting program was very close to the requiredprogram). The System Engineer was present for the installation ofthe recorders as required by the work order.

The recorder was then connected to FWCS number 2. This resulted incross-connecting the inputs and outputs of both SCHs for SGs number1 and 2. The effect of tying the two FWCSs together was notobserved until the SG 2 economizer valve was returned to automaticcontrol. The Control Room Operator observed SG 2 level increasingabnormally and, at about 70 percent NR, placed the economizer valvein manual. By manually decreasing the controller output .he wasable to turn the level rise and return level to its normal range(55 percent NR). The recorder was then removed from FWCS number 2and the economizer valve controller was returned to automatic.Proper automatic SG level control of both FWCSs was observed.There was no abnormal response on number 1 FWCS.

The Shift Supervisor called the Operations Hanager (utility,licensed) and described the event. Based on the fact that therecorder had apparently functioned properly on number 1 FWCS theOperations Hanager directed the Shift Supervisor to consult theLead System Engineer (utility, non-licensed) and to leave therecorder installed in SG1 FWCS if the Lead System Engineerconcurred. The recorder had been .connected to FWCS number 1 forabout 9 hours prior to the event and the FWCSs appeared to befunctioning normally in the automatic mode during this time.

NRC Form 366A (64)B)

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FACILITYNAME (I)

Palo Verde Unit 2TEXT /I/mt'Ptttit tPqvPtd, IItttddic/Imt/HRC Fomt JSSA'4/ (17)

DOCKET NUMBER (2)

o s o o o 5 2 9 8 9

LER NUMBER LS)

SEOUENTIAI.NUMBER

0 0 3

:D~r: REVISIONsC.. NUMBER

01 05

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Prior to the reactor trip on February 16, 1989 at approximately0345 HST, the Control Room received several alarms (ALH)(IB)including condensate pump (P)(SD) strainer (STR)(SD) Hi DP alarmsand FWCS Trouble alarms. The condensate pump strainer Hi DP alarmswere concurrent with the perturbation in the feedwater system whenthe number 1 economizer valve closed. The Secondary Operator(utility, licensed), Shift Supervisor (utility, licensed), andPrimary Operator (utility licensed) positioned themselves at HainControl Boards (CBD) B05 and B06 to evaluate the situation. TheSecondary Operator, Shift Supervisor, and Primary Operator observedboth SG levels decreasing rapidly with level in SG number 1

decreasing below NR indication. Both master controller outputswere observed to be cycling full scale with one to two secondintervals. The feed pumps and number 2 SG economizer control valvefollowed the oscillations of the number 1 SG FWCS but at a slowerrate due to FWCS lead/lag circuits and the physical abilities ofthe mechanical devices to respond to electronic signals.

Immediately prior to reactor trip, Control Room personnel observedcontinued decreasing levels in SG number 1, the SG number 1economizer valve was fully closed, and the SG number 2 economizervalve was 10 percent open. The Secondary Operator observed thatthe SG number 1 economizer control valve manual/auto controllerdemand signal was zero and prepared to open the number 1 SGeconomizer control valve manually in an attempt to restore SGnumber 1 level. The Secondary Operator took manual control of theSG number 1 economizer valve, and opened the valve to mitigate theunderfeed situation that was in progress.

While the Secondary Operator was attempting to manually open the SGnumber 1 economizer valve, the reactor tripped. This occurred 27seconds after the initial secondary disturbance was noted. At thetime of the trip, the Secondary Operator had manually inserted anapproximately 17 percent open demand signal to the number 1 SGeconomizer control valve. Three seconds after the trip, TDASindicated that the SG number 1 economizer control valve was 17percent open. The CRS diagnosed the initial event correctly andthe appropriate recovery procedure 42R0-2ZZ05, Loss of Feedwater,was implemented.

At approximately 0345 HST approximately 14 seconds after thereactor trip, an AFAS for SG number 1 was generated due to low lowSG number 1 level. The AFAS 1 was a result of SG level "shrink"from the reactor trip and from the excessive main feedwater flow.The AFAS signal was generated as designed and the AuxiliaryFeedwater system performed its intended function.

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Palo Verde Unit 2TEXT ///moro 44444 /4 roorrkod, V44 odd?)1444////IC For??I 3ÃA'4/ (Il)

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The Control Room Supervisor (CRS)(utility,, licensed) directed theControl Room Operators to monitor plant safety functions. TheSecondary Operator began his post trip safety function monitoringactions as required. The Secondary Operator .verified properresponse of the Auxiliary Feedwater System.

During the monitoring of the plant safety functions, the SecondaryOperator did not take actions to either restore the economizercontrol valve controller to auto or to manually close the valve toprevent the cooldown. The Shift Supervisor noted that the level inSG number 1 was increasing but was unaware that the SG number 1

economizer valve was not closed. When SG number 1 level was atapproximately 65 percent WR, the Shift Supervisor directed theSecondary Operator to throttle auxiliary feedwater flow to decreasesteam generator feedwater flow.

Following the reactor trip, number 1 SG level continued to increasedue to the number 1 SG economizer valve being'7 percent open. Thenumber 1 economizer valve 'being in manual defeated the Reactor TripOverride (RTO) automatic controls for the SG number 1 economizercontrol valve and the valve remained open. Normally fol.lowing areactor trip,, an RTO of the FWCS occurs to provide initial controlof the SG level and limit the Reactor Coolant System (RCS)(AB)cooldown. The RTO logic (which is a non-safety related system) isdesigned to cl'ose the economizer valves, set the Hain FeedwaterPump Turbines (HFWPTs) to minimum speed, and control downcomervalves to maintain SG level. When SG level increases above the RTOreset level, FWCS control is transferred to single element controlfor maintaining SG level.

As a result of the economizer valve in manual, the RTO logic wasdefeated and excessive feedwater occurred. The resultingoverfeeding of the SG caused a cooldown of the primary system. Atapproximately 0345 HST a SIAS/CIAS, was gener ated due toovercooling of the primary system.

The SIAS/CIAS setpoints are selected to assure adequate makeup ofRCS coolant in the event of a loss of RCS inventory. Thevolumetric decrease in the RCS liquid, due to the cool'ing, resultsin a pressure reduction similar in nature to a loss of inventory.The'High Pressure Safety Injection (HPSI)(Bg) pumps responded asrequired. The design response for SIAS at high pressure is for theHPSI pumps to inject .as they did in this event. The HPSI pumpsstarted due to the SIAS and responded properly to inject water intothe RCS to restore RCS pressure and pressurizer level. The SafetyInjection (SI) system, as well as charging pumps, repressurized theRCS. The SIAS actuat'ion was verified to have occurred per designduring the resetting of the SIAS actuation. The CIAS-also was

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FACILITYNAME (1) DOCKET NUMBER (2) LER NUMBER (6)

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Palo Verde Unit 2TEXT (IImsm FAPCS JI TPSSPsd, IIJp Pddicensl iVRC %%dmI 36643) ((2)

o s o o o 5 2 9 89 —0 03 01 07 OF 1 5

verified to have provided containment isolation per design.

With the number 1 SG economizer valve still in manual, overridingthe RTO trip logic, the SG continued to fill: At approximately0347 HST, an HSIS was received at 91 percent NR in SG number 1.The HSIS isolated main feedwater which terminated the RCS cooldown.

At approximately 0352 HST on February 16, 1989, the ShiftSupervisor declared a Notification of Unusual Event (NUE). The NUEwas declared pursuant to EPIP-02 (Emergency Classification) as aresult of the initiation of a SIAS on low pressurizer pressure. Atapproximately 0400 HST on February 16, 1989 the appropriate stateand local agencies were notified via the Notification and AlertNetwork (NAN). The Nuclear Regulatory Commission (NRC) OperationsCenter was notified at approximately 0444 HST on February 16,1989. The actions of EPIP-02 were performed in a timely manner.Stable conditions were achieved and the NUE was terminated at 0449HST on February 16, 1989.. The NUE was reported in Special Report2-SR-89-002.

The STA was notified and responded to the control room. The CRSdid not direct the STA to perform Appendix BB per 42EP-2ZZ01,Emergency Operation. This was contrary to an approved procedure.Consequently, Appendix BB was not performed. Normally the Duty STAwill initiate Appendix BB following a reactor trip without CRSdirection.

The control room staff stabilized the plant and directed effortstowards resetting ESFAS actuations per the appropriate procedures.

Following plant stabilization, the STA completed an EventNotification Worksheet which was reviewed by the Shift Supervisor .A notification to the NRC via the Emergency Notification System(ENS) phone was made by the STA. Initial observations by theControl Room staff indicated that there was a problem with theactuation of the RAR Essential Chiller following the SIAS. Theinitial notification via the ENS stated that all ESF equipmentoperated correctly. Based on the information available at the timeof the call, the information relayed to the NRC by the STA was notaccurate (i.e. that the chiller did not appear to automaticallystart as designed). A follow-up call was made by Compl.iance(utility, non-licensed) to the NRC via the 'ENS phone stating that"the RAH Essential Chiller did not start automatically. However, acontrol room operator manually started the RAR Essential Chillersuccessfully." Subsequent evaluation has determined that the RAR

Essential Chiller did function as designed in that the automaticstart was concurrent with the operator's attempt to manually startthe RAH Essential Chiller.

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Palo Verde Unit 2TEXT ///moro Ersso /s rrrr((rd, osr rdd4/oor/ HRC %%dnn 36643/ (I2)

o s o o o 5 2 9 89 —00 3 0 1 0 8 »15

C.

During the course of the event, the RCP Vibration readings requiredto be taken at 0400 were missed. A review was made of the on-lineBently-Nevada vibration monitoring data during the time frame thatthe readings were missed and no abnormalities were noted in RCPvibration. The control room staff's work load at the time of themissed readings was the major cause of the deficiency.

Status of structures, systems, or components that were inoperable atthe start of the event that contributed to the event:

Not applicable - no structures, systems, or components wereinoperable at the start of the event that contributed to the event.

D. Cause of each component or system failure, if known:

Not applicable - there were no component or system failures.

E. Failure mode, mechanism, and effect of each failed component, ifknown:

F.

Not applicable - no failed components were involved.

For failures of components with multiple functions, list of systemsor secondary functions that were also affected:

Not applicable - no fai-led components were involved.

For failures that rendered a train of a safety system inoperable,estimated time elapsed from the discovery of the failure until thetrain was returned to service:

H.

Not applicable - no safety systems were rendered inoperable.

Method of discovery of each component or system failure orprocedural error:

The Primary Operator was unsuccessful in shutting down theEssential Chiller on the first attempt because of proceduralinadequacy in Emergency Procedure 42EP-21ZOI. The procedure didnot provide sufficient guidance to ensure that all required actionswere taken prior to securing the essential chillers. In this case,the diesel generators must be shutdown prior to securing theessential chiller.

NRC Form 366A (64)9)

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NRC FORM 366A(64)9)

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FACILITYNAME (1) DOCKET NUMBER (2) LER NUMBER (6I PAGE (3)

Palo Verde Unit 2TEXT ii/moto tpooo it roOuirod, oto oddiobno////IC Form 3654'4/ (17)

I. Cause of Event:

o s o o o 5 2 9

YEAR 4/4

8 9

SEOVENTIALNVM66>I

0 0 3

?r,ij t>EVISION4m NVM 64

01 09 OF 1 5

Reactor Trip

The cause of the reactor trip and AFAS was a malfunction of thenumber 1 steam generator economizer valve. Debris in the pneumaticpositioner of the number 1 SG economizer valve initiated theerratic behavior of the FWCS. This was also the cause of thetransient encountered on February 13, 1989. A small amount ofdebris, approximately 10 mils in diameter (by microscopicexamination), was present in the restrictor on the vertical relaywithin the Fisher Pneumatic Positioner Model 3570 on the SG 81economizer valve. This would have prevented the valve fromoperating properly. The manufacturer concurs .in this evaluation.

The number 1 economizer valve exhibited erratic pneumatic relayoperation during testing conducted after the event. 18C personnelobserved that the valve initially opened nominally, but as the opendemand incr eased the valve slowly drifted closed by itself (i .e.the valve closed fully with a 75 percent open demand).

The debris was evaluated in an attempt to determine its source.The debris appearance was not that of "desiccant" but looked to berepresentative of a metal particle. The overall instrument airsystem is currently under monitoring activities associated withgeneric letter 88-14 and has been demonstrated to meet ANSIstandards for instrument air system. Further analysis of thedebris can not be performed as the particle was lost due,presumably, to normal air movements during the examination process.

Additionally, the inlet filter on the pneumatic regulator for thenumber 1 SG economizer valve was examined and no indications ofcontaminants were identified. This regulator is on a branch lineimmediately before the number 1 SG economizer valve positioner.

Other investigations of the FWCSs (calibration checks, physicalinspection, and testing) found no deficiencies. Testing was alsoperformed on the FWCSs Reactor Trip Override (RTO)(JB) circuitwhich verified proper operation.

The event was compounded by improper installation of the recorderleads due to a personnel error on the part of the II)C Technician(utility, non-licensed) and the System Engineer (utility,non-licensed). The leads cross-connected the input to the outputof the SCH as described in Section I.B. The improper installationof the recorder equipment compounded the February 16, 1989transient by rendering the number 1 FWCS master controller ouputinoperable during a portion of the event. During subsequent

NR C Form 366A (669)

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NRC FORM 366A(64)9)

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FACILITYNAME (11

Palo Verde Unit 2TEXT /ifmoro g»or is rtqrrdtd. Irto Ed'/orm/IYRC Form 36SE'4/ (17)

DOCKET NUMBER (2)

o s o o o 5 2 9 8 9

LER NUMBER (6)

SR+ SEQUENTIALO?~6 NUMSER

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. 366 REVISION@>6 NUMSER

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PAGE (3)

10oF

testing with the digital recorder connected across the economizervalve SCH (i.e., input to output shorted) and with representativeinput values, it was found that the master control output would"clamp" to zero. The "clamping" would remain in place until aninterruption of either the input or output of the master controloccurred.

The number 1 economizer valve slowly closing caused both FWCS

master controller outputs to oscillate in an attempt to controllevel. During this period, the number 1 FWCS master controlleroutput reached an output value low enough to cause the recorder to"clamp" the output to zero. Since the number 1 FWCS mastercontroller was "clamped", the number 1 economizer valve received azero signal and number 1 HFWP was controlled by the number 2 FWCS

master controller. An auctioneer circuit for the HFWP selects thehighest signal for either the number 1 or 2 FWCS master controller(except during RTO).

SG number 2 feedwater flow increased (due to increased feedpressure) as number 1 economizer valve .closed. FWCS number 2responded by reducing both feedwater pump speeds and repositioningnumber 2 economizer valve. The number 2 FWCS master controllerresponded properly to this event by controlling pump speed andnumber 2 economizer valve position to maintain SG number 2 level.

CIAS/CIAS and HSIS

The cause of the SIAS/CIAS and HSIS was an overfeeding to thenumber 1 SG due to the number 1 economizer valve being left inmanual at 17 percent open and the excessive feedwater headerpressure due the "8" HFWP being in manual at a high speed setting(5450 rpm vice approximately 3800 rpm for this condition). The R8"

HFWPT controller was transferred to manual just prior to thereactor trip. Hembers of both operating crews, the offgoing andthe oncoming, were interviewed in an attempt to determine when

'8'FWP

was placed in manual. None of the individuals interviewedcould recall placing the pump speed controller in manual.

PVNGS determined that the pump went to manual 8 seconds prior tothe reactor trip. As indicated by the TDAS plots, the pump speedwas tracking feedwater control system demand until 8 seconds priorto the trip.Several different items were investigated to see if there was anyother mechanism that could have caused the HFWP to shift tomanual. The only mechanism identified would be a momentary loss ofpower on the shift during the fast bus transfer. It is

concluded'hat

a loss of power did not occur based on the fact that the same

NRC Form 366A (Er69)

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NRC FORM 566A(669)

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FACILITYNAME ()) DOCKET NUMBER (2) LER NUMBER (6)

(OP SEQI/ENTIAL Pigi?4 NUMBER

AEVISlONNUMFFR

PAGE (3)

Pal o Verde Uni t 2TEXT ///ovvo g»co/4 /POvt)od. v» odde'ono/P//IC Form 36643/ (IT)

o s o o o 5 2 9 89 —00 3 01 11 » 1 5

power supply is shared by both feed pumps and the 'A'FWP stayedin automatic. In addition, the manual/auto controller will notrevert to manual unless power is lost for greater than 1 second.PVNGS has concluded that the manual pushbutton was inadvertentlydepressed at the time indicated.

In response to the initial transient, both feedwater pumps followedthe demand signal from FWCS number 2. During RTO, the control forthe HFWP is shifted to its applicable FWCS master controller versusgoing through the auctioneering circuit. After the trip, the

'A'FWP

speed decreased to 3670 rpm as designed due to the RTO logic.However, the 'B'FWP remained at high speed as a result of beingin manual.

Both FWCSs entered the RTO mode. FWCS number 1 master controllerwas still "clamped" low at this time. FWCS number 2 mastercontroller functioned as required; however, the 'B'FWP was inmanual and remained at high speed as designed. The number 2downcomer valve immediately responded to the RTO by opening due tothe average RCS temperature being above the setpoint andsubsequently responded properly thereafter. The economizer valvewent closed as designed.

FWCS number 1 master controller output was "clamped" at the onsetof the transient but became Runclamped" as the FWCS number 1 cameout of RTO when SG number 1 level increased to 52 percent prior tothe HSIS. At that time, resetting RTO caused the master controlleroutput to control the number 1 downcomer valve as, designed.

Transient information was provided to I&C Engineering for anindependent assessment. Additionally, the vendor design engineer(contractor, non-licensed) for the FWCS and a vendor system designengineer (contractor, non-licensed) were involved in the analysisat PVNGS. The vendor of the FWCS electronic modules was alsoconsulted.

The economizer valve left approximately 17 percent open and the'B'FWPcontroller in manual added to the severity of the cooldown

transient and subsequently caused an HSIS actuation to occur whichfurther complicated recovery operations. This was a cognitivepersonnel error in that the control room personnel did notrecognize actual plant conditions and was contrary to proceduralguidance.

There were no unusual characteristics of the work location (i.e.Control Room) except the addition of various alarms whichannunciated and the rapid pace of events which occurred. However,simulator training and emergency procedures are adequate to provide

NR C Form 366A (689)

!5 4l

!IRC FORM 366A(669) ~

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TEXT CONTINUATION

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RECORDS'ND

REPORTS MANAGEMENTBRANCH (P430). U.S. NUCLEARREGULATORY COMMISSION; WASHINGTON, DC 20555, AND TOTHE PAPERWORK REDUCTION PROJECT (315001041. OFFICEOF MANAGEMENTAND BUDGET. WASHINGTON. DC 20503.

FACILITYNAME (1)

Palo Verde Unit 2

TEXT /I/more Spree ir rEII/'rrd. err rdd/r/orM/HRC FINm 3664 4/ (12)

DOCKET NUMBER (2)

o so o o 52 9 89

LER NUMBER (6)

(NN SEQUENTIALMPZ NUMBER

,— 00 3

'' REVISIONA< NUMSER

—0 1

PAGE (3)

12 oF1 5

operators with experience to compensate for these conditions.

During recovery operations an auxiliary feed flow indicatorindicated less than the expected flow rate. Further testingdetermined that the auxiliary feedwater- flow instrumentationfunctioned properly through the performance of the loop calibrationand the performance of a pump run test. The auxiliary feed flowindicator (AFB-FI-41B) was calibrated, minor problems were noted inthe as found calibration.

The auxiliary feedwater flow loop converts a delta-p signal into aflow signal through the use of a Square-root extractor. With theexisting plant configuration, the Square-root extractor does notallow the instrument to function below approximately 10 percent ofthe range of the instrument (0-2000 gpm) or below 200 gpm. It isconcluded that the reason for the apparent lack of flow indicationfor 2JAFB-FT41B was that the flow was below the threshold of theSquare-root extractor.

J. Safety System Response:

The following safety systems actuated automatically as a result ofthe event.1) Emergency Diesel Generators (DG) (EK) Train RAR and RB",2) Essential Spray Pond Systems (BS) Train RA" and RB",3) Essential Chillers (KH) Train RAR and "B",4) Essential Cooling Water (BI) Train RAR and RB",5) Condensate Transfer Pumps (KA) Trains RA" and "B",6) Essential Auxiliary Feedwater (BA) Trains "A" and RB",7) HPSI Trains RAR and 'B",8) Low Pressure Safety Injection (BP). Trains RAR and RB",9) Containment Spray (BE) Trains RAR,and RB", and10) HSIS

K. Failed Component Information:

Not applicable - no failed components were involved.

II. ASSESSHENT OF THE SAFETY CONSEQUENCES AND IHPLICATIONS OF THIS EVENT:

The economizer valve was inadvertently left in manual and openapproximately 17 percent which contributed to a 47 degree cooldown ofthe primary system. This exceeded the cooldown limit of TechnicalSpecification 3.4.8. 1, and an engineering evaluation was performed inaccordance with the ACTION requirement. The evaluation determined thatthere were no adverse effects on the structural integrity, of the RCS andthe RCS remains acceptable for continued operation. A review of theFSAR shows that during the cooldown event of February 16, 1989, the

NRC Form 366A (669)

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FACILITYNAME (1) DOCKET NUMBER (2l LER NUMBER (6)

SEQUENWALNUMSER

REVISIONNUMSER

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Palo Verde Unit 2TEXT (I/moro Eooco (I nqvied. o44 oddroooo) iVRC Fomr 3654'4) (17)

o s o o o 52 9 8 9 0 0 3 01 1 3 1 5

plant was bounded by the analysis conducted for the Hain Steam LineBreak event.

All safety systems required to operate performed as designed. The eventdid,not result in any challenges to fission product barriers or resultin any releases of radioactive materials. Therefore, there were nosafety consequences or implications as a result of this event. Thisevent did not adversely affect the safe operation of the plant or thehealth or safety of the public.

I I I. CORRECTIVE ACTIONS:

A. Immediate:

The pneumatic relays were replaced in both Feedwater ControlSystems.

B. Action to Prevent Recurrence:

Controls have been adopted requiring the labeling of test equipmentleads, e.g. labeling the leads as (+) and (-) rather than relyingon the assumption of polarity based on work practices which varyamong disciplines.

Guidance has been provided to the Shift Supervisors emphasizing theimportance of contacting the STA for any transient.

The STA section has developed guidance for STAs with respect toTDAS reinitialization so that transient data is retained foranalysis. This will ensure that TDAS data is preserved whenrequired.

The existing work control troubleshooting procedures for work oncomponents critical for power operation have been revised toidentify critical components requiring higher management reviewbefore troubleshooting activities can begin. In addition theprocedure has been revised to require the use of the EquipmentInstruction Hanuals (EIH) prior to using unfamiliar electronic testequipment or using testing equipment in unfamiliar applications toinsure proper application, use, and to identify any peculiaritiesassociated with the equipment operation.

The digital recorders and isolation amplifiers have been hard wiredtogether eliminating the accessible connections on the recorder.The only accessible input connections are on the isolationamplifier.

An investigation, determined that there is a problem with the

NRC Form 366A (689)

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FACILITYNAME (1) DOCKET NUMBER (2) LER NUMBER (6)

SEQUENTIAL ?AWNVMSSII

REVISIONNVM FII

PAGE (3)

Palo Verde Unit 2TEXT /llmare «woe /4 rer)vtred, vee eddro'oael/VRC Form 3SI/A3/ (17)

o s o o o 52 989 0 03 01 14 OF1 5

availability of Equipment Instruction Hanuals for test equipment.A task force has been formed to review this problem. The taskforce is expected to complete its review and provide recommendedcorrecti,ve actions by January 2, 1990. These recommendations areexpected to be implemented by Harch 30, 1990.

Control Room personnel in Units 1, 2, and 3 have reviewed a summaryof this event with emphasis on team skills and implications ofmanual operations following reactor trip events.

An Operation Plant Guideline has been issued regarding when it isacceptable, desirable, and necessary to transfer system controllersto manual. This guideline is applicable to all major controlsystems.

The crew involved was removed from shift to perform the following:

Perform a self critique

Participate in the Post Trip Review Report (PTRR)investigation

Assist in the determination of corrective actions includingrequired crew upgrades and/or procedural enhancements

The SS involved has discussed management expectationsregarding this event with the Plant Director and OperationsHanager.

The crew participated in several simulator scenarios withspecial emphasis on the following:

CommunicationsTeam WorkPlant AwarenessProcedural Compliance

An evaluation determined the Auxiliary feedwater flow could beraised to 250 gpm. Procedures have been revised to include thisflow rate.

The STA involved was counseled on the requirement for performingAppendix BB of 42EP-2ZZOl. All STAs were briefed on therequirements to perform Appendix BB of 42EP-2ZZ01.

An Instruction Change Request to 42EP-2ZZ01 has been initiated toprovide additional guidance for securing the essential chillers.

NRC FomI 366A (SBS)

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.REGULATORY COMMISSION. WASHINGTON. DC 20555. AND TOTHE PAPERWORK REDUCTION PROJECT (31504))04). OFFICEOF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITYNAME (1I DOCKET NUMBER 12) LER NUMBER (6)

SEQUENTIALNUMBER

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Palo Verde Unit 2

TEXT /I/mort tttct /t toII/)td. Btt tdd4'oot//VRC Form 356A'4/ (12)

o s o o o 52 989 0 0 3 0 1 1 5 OF 1 5

All the STAs have been instructed to verify and understand allrelated plant information to ensure complete and accurate.information is provided to the NRC.

IV. PREVIOUS SIMILAR EVENTS:.

There have been no previous similar occurrences reported pursuant toIOCFR50.73.

There have be'en previous reactor trips reported as a result of low .SG

level. However, none of the previous reactor trips were attributable tothe same root cause described in Section I. I. Therefore none of theprevious corrective actions would have been expected to prevent thisevent.

V. ADDITIIONAL INFORMATION:

There have been 4 total accumulated actuation cycles of the EmergencyCore Cooling System to date. This report satisfies the requirements ofTechnical Specification 3.5.2 ACTION b.

NR C FomI 366A (689)

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