ML20043C028

LER 90-018-00:on 900420,ESF Actuation Occurred Causing Reactor Water Sample Containment Isolation Valve to Close. Caused by Failure of Fuse Which Deenergized Isolation Logic of Valves.Fuse replaced.W/900518 Ltr

ML20043C028
Person / Time
Site:	River Bend
Issue date:	05/19/1990
From:	England L, Odell W GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-018, LER-90-18, RBG-32864, NUDOCS 9006010212
Download: ML20043C028 (5)

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Astf A Cp(( Md CE mpo 3A$ ef $1 May 18,1990 RBG- 32864 File Nos. G9.5, G9.25.1.3 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Gentlemen:

River Bend Station - Unit 1 Docket No. 50-458 Please find enclosed Licensee Event Report No.90-018 for River Bend Station - Unit 1. This report is being submitted pursuant to 10CFR50.73.

Sincerely, W. H. Odell Manager-Oversight River Bend Nuclear Group M

TFP/r)G/RGW/ / B/pg cc: U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 NRC Resident Inspector P.O. Box 1051 St. Francisville, LA 70775 INP0 Records Center 1100 Circle 75 Parkway Atlanta, GA 30339-3064 gg6020212900339 s ADock osooo43g PDC

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At approximately 1540 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.8597e-4 months <br /> on 04/20/90 with the unit at 100 percent power (Operational Condition 1), an engineered safety feature (ESP) actuation occurred causing the reactor water sample containment isolation valve, IB33*AOVF019, to close. At the time of the discovery, instrumentation and control (I&C) technicians were completing a surveillance test procedure (STP) for the reactor core isolation cooling / residual heat removal (RCIC/RHR) system isolation, RHR equipment area ambient temperature high monthly channel function.

The ESP was caused by the failure of the fuse B21H-F076B which de-energized the isolation logic of seven valves (four of which are containment isolation valves). The remaining six valves were already in the closed position at the time of the event.

Corrective action consisted of replacing the fuse, resetting the isolation and reopening the reactor water sample valve. To prevent future isolations from going unnoticed, MR 87-0576 has been approved to be installed during RF-3 to provide indication / annunciation for Division I and II for NSSSS isolations. No further corrective action l

is necessary at this time.

1 The closure of this valve occurrod as designed to prevent leakage from the primary containment in 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 these events.

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verw . = w =m on REPORTED CONDITION At approximately 1540 on 04/20/90 with the unit at 100 percent power (Operational Condition 1), operations discovered an engineered safety.

feature (ESP) actuation which caused the reactor water sample containment isolation valve (*ISV*) 1833*AOVF019 to automatically close. The ESP was discovered when it was noticed that Division 2 residual heat removal (RHR) sample line valves (*SMV*) and reactor water sample valve isolation logic lights were not illuminated. At the time of the discovery, instrumentation and control (I&C)  !

technicians were completing a surveillance test procedure (STP) for the reactor core isolation cooling (*BN*) / residual heat removal (*BO*)

(RCIC/ Ri!R) system isolation, RHR equipment area ambient temperature high monthly channel functional. The ESP could have occurred anytime after the verification of the isolation logic up to the completion of the STP. >

This report is submitted pursuant to 10CPR50. 73 (a) (2) (iv) to document the ESP actuation. .

INVESTIGATION  ;

As a result of the investigation, it was determined that the ESP was caused by the failure of control power fuse (*FU*) B21H-F076B which

• l caused an isolation signal that de-energized the isolation logic, closing seven valves (four of which are containment isolation valves). . i Only the reactor water sai..ple valve (lB33*AOVF019) actuallv closed since the remaining six valves were already in the closed position at l the time of the event. ,

I&C technicians were in the process of completing the performance of STP-207-5255, "RCIC/RHR System Isolation, RHR Equipment Area Ambient .

Temperature High Monthly Channel Functional Test". Although the procedure did not require the verification of the RHR sample line l

valves and reactor water sample valves (isolation) light indication, they noticed that the lights were not illuminated just prior to the completion of the STP, The technicians had not noticed whether these lights were illuminated prior to starting the STP. However, these lights were not off per Operations Section Procedure OSP-0012, " Daily Log Report", which verifies the isolation logic every twelve hours usually after each shift change at 0600 and 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br />.

During the performance of the STP, a jumper was installed between the load side of the fuse and a relay coil (*CL*). This connection is made by using existing insulated clips (banana -jacks) to. keep the relay (*RLY*) energized during the test. The banana jacks were located in open areas of the panel and the surrounding metal located close to these areas was insulated. Also, there were no visible are marks to indicate that a jumper had possibly shorted. Based on the information available, it is not known at what time the fuse failed g'ea = .us o 4n.n. J  ;

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, ro, . ,= == e w m.w on nor what caused the failure. Contributing factors may include a possible power surge or a degraded fuse having reached its life expectancy. A thorough investigation was performed on the control logic process / alignment possibilities and fuse loading assignments to ensure the system is not overloading the protective devices.

The failed fuse (IB21H*F076B) subsequently interrupted Division II reactor protection system (RPS) power which provides control power to the isolation logic for six residual heat removal system valves and one reactor water sample valve. The residual heat removal system functions include shutdown cooling, suppression pool reject to radwaste and sample system containment isolation. Closure of these valves during system operation is detected by a loss of the associated functions, e.g., loss of shutdown cooling, suppression pool reject ,

flow or sample flow. The loss of reactor water sample can be detected by a low flow or a high/ low conductivity condition. A blown fuse results in a safety function actuation (isolation) and is detectable during system operations, or will be detected administrative 1y via i Operational Section Procedure, OSP-0012. The blown fuse resulted in l the isolation of IB33*AOVF019 valve only since the other valves are i normally closed during power operation.

A review of earlier LER submittals found one (LER 89-001 dated January 8, 1989) which meets the criteria of being similar to this event except that the failure occurred during the performance of a different STP (STP-058-4501). During the investigation of the past operating history of this fuse it was discovered that it had also failed on December 2, 1986 and that the failure was not documented as to the time or cause of the failure. As a result of those failures and to minimize future events of this type, alternate test connection  ;

points were specified in the STPs and use of banana jack type clips I was added to the procedure where alternate connection points are not feasible. Corrective action also included a procedural change to OSP-0012 to include verification of the isolation logic overy twelve hours.

CORRECTIVE ACTION Immediate corrective action consisted of replacing the fuse, resetting l the isolation logic and reopening the reactor water sample valve. To prevent future isolations from going unnoticed, MR 87-0576 has been

! approved to provide indication / annunciation for Division I and II for NSSSS isolations. This modification will be completed during RF-3, currently scheduled for September 1990. No further corrective action is necessary at this time, gaa-- . u i o.o . +... .= ..i  !

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l The isolation of.the reactor water sample containment isolation valve l occurred as designed to prevent leakage from the primary containment l in 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 this event.

NOTE Energy Industry Identification System Codes are identified in the text as (*XX*).

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