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OGULF STATES UTILITIES COMPANY '

RIVER BEND STATION POST Of FICE DOX 120 ST FRANCISVILLt. LOUIStAN A 70775

ARE A CODE 504 635 6094 3 46 B65t

November 21 , 1990-RBG-3 4 0 51 -

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File Nos. G9.5, G9.25.1'.3

U.S. Nuclear Ibgulatory Omnission iDocumnt Control DeskWashington, D.C. 20555

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Gentlemen:

River Bend Station - Unit 1Docket No. 50-458

Pursuant 10CFR50.73,- please find enclosed Licensee EventReport No. 90-018, Revision 1 for River Bend Station - Unit 1.This supplemental report provides a revised schedule for-cmpleting the corrective action during the . fourth refuelingoutage instead of the third. Further discussion on this changeis provided in the LER.

Sincerely,

l %1. e 1- i'.Manager-OversightRiver Bend Nuclear Group

k /B8 fM NMect.IAE/PDG/flF2/$N/RCL/pg

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cc: U.S. Nuclear Regulatory Ccmrdssion611 Ryan Plaza Drive, Suite 1000 -|Arlington, TX 76011

NRC Pesident InspectorP.O. Box 1051St. Francisville, IA 70775 |

INPO' Records Center-1100 Circle'75 ParkwayAtlanta, GA 30339-3064

9011290119 901121 ~ ~ " ' ' 'PDR ADOCK 05000458 / -'\* PDC >

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NRC PORa 304 U.S. NUCLE A) 0.81ULAT AY COMMIS8 ION, APPIOVED OMO NO 315H104E APintS 4'30/92

ESTIMATED Su% DEN 9531 f tSPONtt 70 COMPLv TrTH TMis. .

LICENSEE EVENT REPORT (LER) EM&"lyiMo*No'',fo'.SoYN $lia'tYT7f t Alic'RIs' * '

o' AND RAPORTS MANAGEMENT SRANCH IP 6301, V $ NUCLE AR

PAPER 0 K Rt Y ON J 3 00 0 CisOF MANAGEMENT AND SUDGET,vva5MINGTON, DC 20603.

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f ACILITV NAME til 'DOCKt1 NUMetR (2) PAGE (33

RIVER BfND STATION o|5|01o|0|41518 1 |OF|0 l 4167 si les |

| Reactor Mater Sample Valve Isolation (ESP) due tc Blown Fuse |tytNT oaf t (Si LE R NVMBER (Si REPORT DATI 176 OTHE R f ACILif f t$ INVOLVED let

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At approximately 1540 hourt on 04/20/90 with the unit at 100 percentpower (Operational Conditirn 1),'an engineered safety feature (ESP)actuation occurred causing the reactor water sample containmentisolation valve, 1B33*AOVF019, to close. At the time of thediscovery, instrumentacion and control, (I&C) technicians werecompleting a surveillance test procedure (STP) for the reactor core

i isolation cooling / residual heat removal. (RCIC/RHR) system isolation,| RUR equipment area ambient temperature high monthly channel function.'

The ESF was caused by the failure of the fuse B21H-F076B whichde-energized the isolation logic of seven valves (four of which arecontainment isolation valves). The remaining six valves were alreadyin the closed position at the time of the event.

Corrective action consisted of replacing the fuse, resetting _theisolation and reopening the reactor water sample valve. As anenhancement and to prevent future isolations from going unnoticed, MR87-0576 has been approved for installation during RF-4 to provide onthe control room boards indication / annunciation for Division I and II_for NSSSS isolations. No further corrective action is necessary atthis time. The closure of this valve occurred as designed to preventleakage from the primary containment ic the event of an accident.Therefore, there was no adverse impact on the safe operation of the_ plant or to the health and safety of the public as a result of theseevents.

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N,.C Perm 864 16 696

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PORM306A. U.6, NUCL44.R LE 1ULATOR Y COMM40SIOle

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LICENSEE EVENT REPORT (LER) f,'';",^18,oavagNP,J'50,y,',,'Lc?'|'',7 ,*o',",,M,

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OP MANAGEMENT AND SUDQtT. w ASHINGT0*s. DC 20603.

P ACILITY NAMG Of DOCKti NUtGBERL2nLE A NUMBER 161 ,A00136

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RIVER BEND STATION o ]s j o | o | o 141518 9 10 Oll 012 0F 0 l401118- -TaxTm M . . wice-.anu nn

REPORTED CONDITION

At approximately 1540 on 04/20/90 with the unit at 100- percent power(Operational Condition 1), operations discovered an engineered safetyfeature (ESP) actuation which caused the reactor water samplecontainment isolation valve (*ISV*) 1B33*AOVF019 to automaticallyclose. The ESF was discovered when it was noticed 'that Division- 2residual heat removal (RHR) sample line valves (*SMV*) and reactorwater sample valve isolation logic lights-were,not illuminated. Atthe time of the discovery, instrumentation- and control (I&C)technicians were completing a surveillance test -procedure (STP); forthe reactor core isolation cooling (*BN*)/ residual heat-removal ( * BO * )(RCIC/RHR) system isolation, RHR equipment- area ambient temperaturehigh monthly chant.al functional. The ESF could have occurred anytime;after the verification of the isolation logic up-to the completion ofthe STP.

This report is submitted pursuant to 10CFR50.73 (a) (2) (iv) to document.the ESF actuation.

INVESTIGATION

As a result of the investigation, it was determined that the' ESF 'was'

caused by the failure of control power fuse (*FU*) B21H-F076B which *caused an isolation signal that de-energized the ' isolation logic,closing seven valves (four of which are containment' isolation ~ valves).Only the reactor water sample valve (lB33*AOVF019). actually closedsince the remaining six valves were already in the closed position atthe time of the event.

I&C technicians were in the process of completing the performance ofSTP-207-5255, "RCIC/RHR System Isolation, RHR Equipment Area Ambient. Temperature High Mont'hly Channel Functional Test". Although theprocedure did not require the verification of'the RHR sample linevalves and reactor water sample valves (isolation)- light indication,they noticed that the lights were not illuminated just prior-to thecompletion of the STP. The technicians had not noticed whether theselights were illuminated prior to starting the STP. However, theselights were not off per Operations Section Procedure OSP-0012, " DailyLog Report", which verifies the isolation logic every twelve hoursusually after each shift change at 0600 and 1800 hours.

During the performance of the STP, a jumper was installed between theload side of the fuse and.a relay coil'(*CL*). This connection.ismade by using existing insulated clips (banana- jacks) to- keep therelay ( *RLY * ) energized during the test. The banana jacks werelocated-in open areas of the panel and the surrounding metal locatedclose to these areas was insulated. Also, there were no visible arcmarks to indicate that a jumper had possibly shorted. Based on the

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0 MANAQtMtNT AND DV0GET w ASHINGTON. DC 20603.

FACILITY NAME m 00CKtT NUMStR (2l L84 NUM9tn (ep PA04 (31

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RIVER BEND STATION 0 |S |0 |0 |01415| 8 910 0|118 0| 1 Ol 3 0F 014-- --rixv ,, M . , ,. M we i anw,nm

information available, it is not known at what time _ the fuse. failednor what caused the failure. Contributing factors may include apossible power surge or a degraded fuse having - reached its lifeexpectancy. A thorough investigation was performed on the controllogic process / alignment possibilities and fuse loading-assignments toensure the system is not overloading the protective' devices.

The failed fuse (IB21H*F076B) subsequently interrupted Division IIreactor protection system (RPS) power which provides control power' to !the isolation logic for six residual heat removal system valves andone reactor water sample valve. The -residual heat removal systemfunctions include shutdown cooling, suppression pool reject toradwaste and sample system containment isolation. Closure of these i

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valves during system operation is' detected by a loss of the associatedfunctions, e.g., loss of shutdown cooling, suppression pool . rejectflow or sample flow. The loss of reactor water sample can be detectedby a low flow or a high/ low conductivity condition. A blown fuseresults in a safety function actuation (isolation) and is detectableduring system operations, or will be- detected administratively via iOperational Section Procedure, OSP-0012. The blown c:se resulted in 'the isolation of 1B33*AOVF019 valve only since the other valves arenormally closed during power operation.

A review of earlier LER submittals found one (LER 89-001 dated January8, 1989) which almost meets 'ao criteria of being similar to this-event except that the failure occurred during the performance of adifferent STP (STP-058-4501). During the investigation of the pastoperating history of this~ fuse it was discovered that it had alsofailed on December 2, 1986 and that the' failure was not documented asto the time or cause of the failure. As a result of those failuresand to minimize future events of this type, alternate test connection-points were specifie.d in the'STPs and use of banana jack type clips 1was added to the procedure where alternate connection points are notfeasible. Corrective action also included a procedural. change toOSP-0012 to include verification of the isolation logic every twelvehours.

CORRECTIVE ACTION

Immediate corrective action consisted of replacing the fuse, resettingthe isolation logic and reopening the reactor water sample valve. As

enhancement and to prevent future isolations from going unnoticed,anHMR 87-0576 has been approved to locate indication / annunciation forDivision I and Il NSSSS isolations on the-control room boards asopposed to the back panels. This modification- will be completedduring RF-4, currently scheduled for March, 1992. In the interim(during performance of OSP-0012, " Daily Log Report") operations

1personnel will continue to verify that the isolation status lights on-control room back panels are illuminated. No further corrective actionis necessary at this time. i'

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FACILITY NAME {11 DOCKET NUMBERtal LEA NUMSG A (6) . PA04 (31

uma - " d.m^ ' "A".W

Oll 014 0F 0|4 .RIVER BEND STATION o |s j o j o j o 141518 910 01118 ---I tXT f# mwe ausse 4 suvused, ese assusaef N#C #wm W W (171

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SAFETY ASSESSMENT .i

The isolation of the reactor water sample containment isolation. valve-occurred as designed to prevent leakage from the primary . containment

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in the event of an accident. Therefore, there was no adve'rse impact_'

on the safe operation of the plant or to the health and safety of. thepublic as a result of-this. event.

NOTE: Energy Industry Identification System Codes are identified inthe text as .(*XX*).

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CIC Penn 308A IS491

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