ML19325F180

LER 89-024-00:on 891006,reactor Protection Sys Initiated Full Reactor Scram Signal.Caused by Output Signal for LPRM 40-33A Spiking High.Lprm Detector Placed in Bypass Position & Scram Signal reset.W/891106 Ltr

ML19325F180
Person / Time
Site:	Peach Bottom
Issue date:	11/06/1989
From:	Cribbe T, Danni Smith PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-024-01, LER-89-24-1, NUDOCS 8911150139
Download: ML19325F180 (4)

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! PHILADELPHIA ELECTRIC COMPANY dy; '. 1 .PEACll BUI'lOM AR)MIC POW 1.R STATION

' R. D.1, llox 208 -

.U o ' Delta, Itnnsylvania 17314 p aces sorrtm-ine ram t.m tw Excruimet - (717) 456-7014-

' D.' M. Smith

. Vice Priskient' {

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November 6, 1989 Docket No. 50-277

' Document Control Desk

. U. S. Nuclear Regulatory Commission Washington, DC 20555 SUBJ3iCT: Licensee Event Report Peach Bottom Atomic Power Station - Unit 2 This LER concerns a Local Power Range Monitor (LPRM) spiking upscale, causing a full reactor scram while'in hot shutdown.

Reference:

Docket No. 50-277' Report Number:- 2-89-024 .

Revision Number: 00 l Event.Date: 10/06/89 i Report Date: 11/06/89 r Facility: Peach Bottom Atomic Power Station RD 1. Box 208A, Dolta, PA 17314 ',

This LER is being submitted pursuant to the requirements of 10 CFR i 50.73(a)(2)(iv). 1 Sincerely, j 4

cc: J. J. Lyash, USHRC Senior Resident inspector W. T. Russell, USNRC, Region I i l

8911150139 691106 \

PDR ADOCK 05000277 it s S PDC .

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c Poem age U.S. NUCLPG 8,80ULATORY COMMIS$lON

APPROVED OMS LO 1190'JiO4 LICENSEE EVENT REPORT (LER) " ma ' * 8 ' '

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T. E. cribbe, Regulatory Engineer ,

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-(RTS) initiated a full Reactor Scram Signal. The full reactor scram was a result of a channel "B" RPS scram signal being received in conjunction with a channel "A" RPS scram signal already inserted. The "B" RPS scram signal was the result of a "D" Average Power Range Monitor (APRM) Hi-Hi Flux Signal caused by Local Power Range Monitor (LPRM)40-33A spiking upscale. The "A" channel half scram was inserted as a result of the "E" IntermeM ate Range Monitor (IRM) being inoperable and blocked in standby. Immediate corrective action was to bypassLPRM 40-33A. The "A" half scram signal was reset when the previously inoperable "E" IRM was repaired and returned to service. The proximate cause of this event was the output signal for the LPRM 40-33A spiking high. No actual safety consequences occurred as a result of this event. It is planned to perform an investigation of the cause of the spiking output of LPRM 40-33A. The results of this investigation and the resulting corrective actions will be reported in a supplement to this LER. There was one previous similar event.

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senv , . < , m ocr aanuon Requirements for the Report This repol't is required pursuant to 10 CFR 50.73(a)(2)(iv) because an LPRM spiking ,

tpscale resulted in an Engineering Safeguard feature Actuation (i.e., Reactor j Proter;tionSystem(Ells:JC)).

l Unit Status at Time of Event Unit 2 was in Hot Shutdown with reactor pressure 450 psig and reactor level at +22".

Unit 2 "A" RPS scram signal had previously been inserted as a result of less then the ]

required number of Intermediate Range Monitor (IRM) Detectors (EIIS:0ET) operable, j

Description of the Event l

At 1307 hours0.0151 days <br />0.363 hours <br />0.00216 weeks <br />4.973135e-4 months <br /> on 10/6/89 with Unit 2 in Hot Shutdown, the Reactor Protection System (RPS) initiated a full reactor (Ells:RCT) scram signal. The full reactor scram was a result of a channel "B" RPS scram signal being received in conjunction with a channel i

'A' RPS scram signal already inserted. The "B" RPS scram signal was a result of a  !

"0" Average Power Range Monitor (APRM) (Ells: MON) Hi-Hi flux Signal caused by LPRM i 40-33A spiking upscale. The "A" channel half scram was previously inserted as  !

required by Technical Specifications (less than the required number of IRMs l operable). No control rod movement occurred because all rods had previously been J inserted.

The "B" channel half scram was reset at 0350 hours0.00405 days <br />0.0972 hours <br />5.787037e-4 weeks <br />1.33175e-4 months <br /> when "D" APRM Hi-Hi Flux Trip Signal was reset by bypassing the 40-33A LPRM. The "A" channel half scram was reset i when the previously' inoperable "E" IRM was repaired and returned to service at 0445  ;

hours on 10/6/89.  !

Cause of the Event The proximate cause of this event was the output of the 40-33A LPRM spiking high. l The root cause of the spiking of the LPRM signal is under 1.westigation by ,

Philadelphia Electric Company and General Electric Company (LPRM supplier). '

Analysis of the Event No safety consequences occurred as a result of this event.

The scram signal occurred with the unit in Hot Shutdown. No actual control rod motion occurred as a result of this scram. Had the LPRM spike occurred during a reactor startup (Mode Switch in "startup") a full scram would not have occurred. Per Technical Specification requirements, no more than one IRM detector would have t'een bypassed, thus the "A" channel hElf scram would not have been present. Had the LPRM spike occurred during power operation (Run Mode) a full scram would not have occurred. Power level would have been above that which requires the IRM instruments to be operable. Therefore, the "A" channel half scram would not have been present.

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% ,,,,,. . . ., . . we - u nn Corrective Actions  !

The following immediate corrective action was taken: [

l LPRM detector 40-33A was placed in the bypass position at 0350 hours0.00405 days <br />0.0972 hours <br />5.787037e-4 weeks <br />1.33175e-4 months <br /> and the "B" l channel scram signal was reset. .

. The following corrective action is planned:

The cause of the spiking of LPRM de' tor 40-33A will be investigated. The results of this investigation and appropriate corrective actions will be provided in a [

supplement to this LER.

Previous Similar Events-  !

There has been one previous similar event reported in LER 02-89-16. This event also  !

involved the spiking of an LPRM in conjunction with an already present half scram inserted in the other RPS channel. The root cause of this event is under investigation and the appropriate corrective actions have not yet been identified.  !

Therefore, the corrective actions in LER 02-89-16 could not have been expected to  ;

prevent this event. '

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