ML19332F863

LER 89-056-00:on 891119,unexpected Nuclear Steam Supply Shutoff Sys Group Iii,Div 4 Isolation Initiated ESF Actuation.Caused by Defective read-set Selector Switch. Switch repositioned.W/891213 Ltr

ML19332F863
Person / Time
Site:	Limerick
Issue date:	12/13/1989
From:	Endriss C, Mccormick M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-056, LER-89-56, NUDOCS 8912190222
Download: ML19332F863 (5)

Text

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10 CFR 50.73 PHILADELPHIA ELECTRIC COMPANY LIMERICK GENER ATING ST ATION P, O. BOX A SAN ATOG A. PENNSYLV ANI A 19464 (216) 3271200 sat,2000 M. J. M cCOMMIC K. Ja. P.E.

6.....2^.".'.".'.'".".m..., December 13, 1989 '

Docket No. 50-352' License No. NPF-39  ;

U.S. Nuclear Regulatory Commission

,i Attn: Document Control Desk Washington, DC 20555

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SUBJECT:

Licensee Event Report Limerick Generating Station - Unit 1

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l' l- This LER reports an unexpected Reactor Water Cleanup System L isolation, an actuation of a portion of the Nuclear Steam Supply Shutoff system-(an Engineered Safety Feature), due to a defective selector switch on.a Riley Corp. temperature transmitter trip

. unit.-

-References. Docket No. 50-352-Report Number: 1-89-056 Revision Number: 00 i Event Date: Noveraber 19, 1989 '

Report Date: December 13, 1989 Facility: Limerick Generating Station ->

P.O. Box A, Sanatvga, PA 19464 1

This LER is being submitted pursuant to the-requirements of ,

10 CFR 50.73(a)(2)(iv)..  :

Very t uly yours, f

DMS:ch cc: W. T. Russell, Administrator, Region I, USNRC T. J. Kenny, USNRC Senior Resident Inspector, LGS 8912190222 891213 PDR ADOCK 05000352, h/

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, , i O'n November 19, 1989, at 0135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br />, a plant operator placed the -

" READ-SET" selector switch located on temperature transmitter

. trip unit, TTS-44-lN600M, to the " READ" position to obtain a temperature reading for the Reactor Water Cleanup (RWCU) 'lB' Non-Regenerative Beat Exchanger (NRHX) room area. Immediately'

- after the selector switch was placed to the " READ" position, an unexpec'ted Nuclear Steam Supply Shutoff System Group III,

, Division 4 isolation was initiated, an Engineered Safety Feature actuation. The isolation signal caused the RWCU Outboard Primary s Containment Isolation Valve to close, and the RWCU pumps then , J. ,

tripped on low flow. Instrumentation and Controls (I&C) ,

technicians repositioned the selector switch in order that the isolation signal could be reset by the Main Control Room operators. The BWCU system was out of service for nin'eteen minutes. The consequences of this event were minimal. The reactor water level and chemistry were not affected by the RWCU l system isolation. The RWCU system isolation was caused by a defective " READ-SET" celector switch on the 'lB' NRHX room area temperature transmitter trip unit. I&C technicians replaced the l temperature transmitter trip unit which had the defective selector switch. No other incidents have occurred as a result of a defective selector-switch on similar trip units. .

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Unit-Conditions Prior to the Event: -

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Operating Condition: 1.(Power Operations)

Power Levels- 100%. .-

l Description of the Event:

On November 19, 1989, at 0135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br />, the Reactor Water Cleanup .

(RWCU) system (EIIS CE) Outboard Primary Containment Isolation Valve (PCIV), HV-44-lF004, automatically isolated.

This .

isolation was due~to a Nuclear Steam Supply Shutof" System I (NSSSS) (EIIS:JM) isolation actuation, an Engineered Safety Feature (ESP), from a spurious trip of the Steam Leak Detection ,

(SLD) system (EIIS:IJ) isolation signal.

, During performance of the Unit 1. Daily Surveillance Test, a non-licensed. plant operator placed the " READ-SET" selector switch ,

'(EIIS:ES) located on Riley Corp. (Model No. 86APPGF-EG) ,

temperature transmitter trip.. unit (EIIS:TS), TTS-44-lN600M, to the:" READ" position to obtain a SLD system temperature reading-for the RWCU 'lD' Non-Regenerative Heat Exchanger (NRHX) room area. The~ Daily Surveillance Test requires the performance of channel checks on each isolation actuation instrumentation channel every shift (once every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />), to meet Technical Specifications (TS) Surveillance Requirement 4.3.2.1.

Immediately after the selector switch was placed to the " READ" position, an-unexpected NSSSS Group III, Division 4 isolation actuation occurred. The isolation signal caused RWCU valve HV-1 44-lF004 to close, and the RWCU pumps then t. ripped on low flow.

The isolation was accompanied by a."Div 4 Steam Leak Det Sys Hi Temp"' annunciator. alarm in the Main Control Room (MCR) as y expected..

_ MCR operators then notified the shift Instrumentation and Controls (I&C) technicians of the RWCU system isolation event.

Upon investigation, I&C technicians discovered that the selector switch was defective.- The technicians repositioned the selector switch in order that the isolation signal could be reset by the MCR operators. I&C also performed the calibration functional test for the trip unit and verified that the trip unit would perform its design function if required.. -

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The MCR operators then reset the isolation signal at 0145 hours0.00168 days <br />0.0403 hours <br />2.397487e-4 weeks <br />5.51725e-5 months <br />, y in accordance with General Plant (GP) procedure GP-8, " Primary j and Secondary Containment Isolation Verification and Reset," and ,

the RWCU system was returned to service at 0154 hours0.00178 days <br />0.0428 hours <br />2.546296e-4 weeks <br />5.8597e-5 months <br />. The RWCU system was out of service for nineteen (19) minutes.

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0l5l6 0l 0 0l 3 cF 0 14 ven s. m.w aac a-a mna v on A'four hour notification was made to the NRC'on November 19, at 0402. hours, in accordance with the requirements of 10 CFR 50.72 (b)(2)(ii) since the event resulted in the automatic actuation of (

an ESF. Accordingly, this event is being reported in accordance with the. requirements of 10 CFR 50.73 (a)(2)(iv).

Consequences of the Event:

The consequences of this event were minimal. There was no release of radioactive material to the environment as a result of i this event. The RWCU system isolated, as designed, when the '

defective selector switch initiated a NSSSS Group III, Division 4 isolation signal. Additionally, the reactor water level and chemistry were not affected by-the RWCU system isolation. l l

In the event the outboard RWCU system isolation valve failed to

'close on an actual high NRHX room area temperature, the redundant j

' channel inboard isolation valve would have closed to isolate the  ;

system. l Cause of the Event:

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The RWCU system isolation was caused by a defective " READ-SET" selector switch on the SLD system 'lB' NRHX room area transmitter trip unit.- When the selector switch was placed to the " READ" position, the trip unit circuitry was de-energized which initiated a RWCU outboard isolation.

Corrective Actions:

The I&C technicians repositioned the selector switch in order that the isolation signal could be reset by the MCR operators, and performed the calibration functional test to verify that the trip unit would-perform its design function if required. A "Do .

Not Operate" tag wan placed on the selector switch, and the MCR operators were instructed to notify I&C when temperature readings from the trip unit were to be taken until the selector switch was q repaired. The MCR operators then reset the isolation signal using GP-8 at 0145 hours0.00168 days <br />0.0403 hours <br />2.397487e-4 weeks <br />5.51725e-5 months <br />, and the RWCU system was returned to ,

service at 0154 hours0.00178 days <br />0.0428 hours <br />2.546296e-4 weeks <br />5.8597e-5 months <br />, g.,.a..

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0l 0 01 4 0F 0 l4 vent . . a sm aac e mna v on Actions Taken to Prevent Recurrence:

On November 20, 1989 at 1310 hours0.0152 days <br />0.364 hours <br />0.00217 weeks <br />4.98455e-4 months <br />, I&C technicians replaced temperature transmitter trip unit, TTS-44-lN600M, which had the defective selector switch.

There are approximately eighty six (86) Unit 1 Riley Corp.

temperature transmitter trip units with " READ-SET" selector switches being operated daily by plant operators. Each selector switch _is operated over ninety (90) times per month. No other incidents have occurred as a result of a defective selector switch on the Unit 1 Riley trip units. There have been no trip units previously replaced due to a broken or defective selector switch. Additionally, the Riley temperature transmitter trip unit in question was installed in SLD system on April 12, 1989, and is not the_ original Riley trip unit that was installed during the Unit 1 construction phase. There are identical Riley trip units which have been in operation since Unit I start-up

'(approximately six (6) years), with-no selector switch problems.

Therefore this event is considered to be an isolated occurrence.

Additionally, the Riley temperature transmitter. trip' unit with

.the defective _ selector. switch will be sent to_Riley Corp. for a ,

failure cause analysis, i

Previous Similar Occurrences:

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! There are no previous similar-occurrences, however, LER's 84-12, 26, 34, 35, 36; 85-01, 25, 27, 35, 55; 86-13, and 87-052 reported isolations of the RWCU system resulting from a design deficiency of the Riley Corp. temperature transmitter trip unit circuitry.

There was not a design deficiency in the selector switch portion of the trip unit. Therefore, the design change performed for the l

previous events could not have prevented the occurrence of this event.

Tracking Codes: X Other, unexpected failure '

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