ML20029B134

LER 90-033-01:on 901104,RWCU Sys Isolation Occurred While Performing Plant Mod to Power Supply Wiring in Control Room Panel 1H13-P642.Caused by Removal of Terminal Screw.Power Supply reterminated.W/910226 Ltr

ML20029B134
Person / Time
Site:	River Bend
Issue date:	02/26/1991
From:	England L, Odell W GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-033, LER-90-33, RBG-34-538, NUDOCS 9103050476
Download: ML20029B134 (4)

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GULF STATES UTILITIE'S C O h1E*A N Y

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t. n ; n w e, .< aw Pebruary 26, 1991 12c- 34,538 Pile 165. G9.5, G9.25.1.3 U.S. thclear Dcgulatory Cannission Docunent Control Iesk Washington, D.C. 20555 Gentiment River Ibnd Staticri - Unit I tocket !Jo._50_-458 Plealm find enclosed Supplcsmnt I to Licensee Pvont Igort ib.90-033 for River Ibnd Station - Unit 1. This supplmental report in nulmitted to provido a status of CSU'n evaluation of the I:ngineering/ Maintenance Planning res;onsibility and interface.

Sincerely, Y.1. Icl51 Kmager - Oversight River Wnd tiuclear Group h$ $

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/pj cc U.S.11uclear Regulatory Cumtioni n 611 Ryan Plaza Drive, Duite 1000 Arlington, 7% 76011 NRC Ibsident Inspector P.O. Icx 1051 St. Francisville, IA 70775 INPO Decords Center 1100 circic 75 Parkway Atlanta, G4 30339-3064 Mr. C. R. Oterg htblic Utility Otmnission of Texas 7800 Shoal Creek Blvd., Suito 400 tbrth Austin, TX 78757 -

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On 11/04/90 _at 1140 with the unit in Operational Condition 5

-(Refueling), an isolation of the reactor water cleanup system (RWCU) occurred. The isolation occurred while performing plant modifications to power supply wiring 11. control room panel 1H13-P642. The power supply circuit in this panel provides power to several systems including the leak detection svatem (LDS) and the RWCU system and is daisy-chained from one component to another. The modification involved de-terminating and re-terminating power supply leads on several LDS components, and when the first de-termination was made, power was lost to the RWCU system through the daisy-chain. Since the safety related components of the RWCU system fall to a safe position upon a loss of power, an isolation resulted. This isolation constitutes an engineered safety feature (ESP) actuation; therefore, this event is reportable pursuant to 10CPR50.73 (a) (2) (iv) .

The RWCU isolation occurred es designed and was restored following re-termination of the lead. Therefore, this event did not' adversely affect the health and safety:of the public. At the . direction of the Plant Manager, a task force has been formed to establish a program to resolve engineering /mainte.tance planning interface issues. Following conclusion of the task force effort, this LER will he revised by April 1, 1991 to provide the results of GSU's evaluation and the root cause of this event, u.co m wsm

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REPORTED CONDITION on 11/04/90 at 1140 with the unit in Operational Condition S I (Refueling), an isolation of the reactor water cleanup system (RWCU)

(*CE*) occurred. The isolation occurred while performing plant modifications to power supply viring in control room panel (*PL*) ,

1H13-P642. The power supply idrcuit in this panel provides power to several systems including the leak detection system (LD3) and the RWCU '

system (*CE*) and is daisy-chained from one component to another. Ce modification involved de-terminating and re-terminating power supp/,

leads on several LDS components, and when the first de-termination was made, power was lost to the RWCU system through the daisy-chain.

Since the safety related components of the RWCU system f all to a safe pooltion upon a loss of power, an isolation resulted. This isolation constitutes an- angineered safety feature (ESP) actuations therefore, this event is reportable pursuant to 10CFR50.73 (a) (2) (iv) .

JllVESTIGATION Modification Requert (MR) 87-0837, field change rotice (FCN) I required the addition / deletion of vetious wiring terminations in 11113 *PNLP64 2 (*PL*) to replace the existing -leak dttoction system drywell unit cooler condensate leak-off line flow transmitter instrumentation loop. During the performance of this work, the work instructions provided in FCN -1 required that o r..s of- two wires >

currently terminated on fuse'1E31A-F78-1 be removed and another wire addedi When the terminal screw was removed at this termination point, control power-for all downstream instrument loops was lost which .

caused an RWCU isolation due to power failure. These instrument loops are designed to fail safe on a loss of control power. ,

The work instructions given in MR 87-0837 FCN 1 provide 3. complete list of steps necessary to accomplish the wiring changes shown within the MR.- However, precautionary steps were not provided to warn of

- potential isolations associated with the addition / deletion of power cupply wiring.

• A review of previous reports has identified two similar events. LER 89-016 reported isolations of valves (*ISV*) IDER*AOV126 and IDPR*AOV101 during a modification in panel (*PL*) 1H13*P852. An engineering analysia completeu prior to the implementation of the modification (to install an emergency. operating procedure actuation switch) did not reveal the potential _for_ relay 3D-2-11SCB0.4 to react before relay 3B-IISCB04 when the AC daisy chain neutral for the Division II BOP loss of coolant accident (LOCA) initiation circuit was re-established. LER 90-035 reported a loss of shutdown cooling when a -

cable (*CBL3*) was disconnected from control room panel (*PL*) ,

1H13-P692. The system engineer prepared a cable-effects list for a N$C Form 3A6A (549n

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modification. This was caused by the system engineer not recognizing that the removal of the cable would result in the isolation of valve IE12*MOVT009.

_ CORRECTIVE ACTION At the time of the isolation, the Shift Supervisor ordered the maintenance personnel to re-terminate the power supply lead. With pow r restored, the Shift Supervisor ; cid the isolation signal and the RWCU (*CE*) system wan returned to operation.

Design Engineering implemented specific precautionary stops directly into the field work instructions of the modification package to prevent adda.tional occurrences. These additional work instructiono were then incorporated into the maintenance job plan.

GSU continues to evaluate the engineering / maintenance planning responsibility and interface to identify corrective actions designed to reduce the potential for similar events. At the direction of the Plant Manager, a task force compriseu of representatives from System Engineering, Maintenance Pinnning, Design Engineering and Operations has been established. The purpose of this task force is to establish a program for in-line review of modification requests prior to release for field work in order to prevent ESP actuations, operability problems and construction problems. Upon conclusion of its evaluation, the task force will report its fladings to the Plant Manager. A supplement to this LER will be provided by Apri.t 1, 1991 to report the results of GSU's tvaluation and the root cause of this event.

SAFETY ASSESSMENT The FWCU isolation occurred as designed and was rentored following re-termination of the lead. Therefore, this event did not adversely affect the health and safaty of the public.

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

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