ML20086J528

AO 74-1:on 740709,intermediate-range Monitor Channel H Failed to Produce Downscale Trip.Caused by Amplifier & Attenuator Cicuit Board Generating Oscillation Whose Magnitude Prevented Channel from Responding Value Signal

ML20086J528
Person / Time
Site:	Peach Bottom
Issue date:	07/19/1974
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086J533	List: ML20086J528 ML20086J535
References
AO-74-1, NUDOCS 8401240061
Download: ML20086J528 (2)

Text

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(]A PHILADELPHIA ELECTRIC COMPANY 50-278 23O1 MARKET STREET PHILADELPHIA. PA.19101 (215) 8414ooo July 19,1974 j[D' t' .w Mr. A. Giambusso ,

Deputy Director of Reactor Projects M United States Atomic Energy Commission h'., MQggpQ Directorate of Licensing  %

Washington, DC 20545 7,, ga..:a

Subject:

Abnormal Occurre'nce s' * . fEK\h{

' ' ~

The following occurrence was reported to Mr. R. A. Feil, A.E.C.

Region 1 Regulatory Operations Office on July 10, 1974. . Written noti-fication was made to Mr. James P. O'Reilly, Region I Regulatory Opera-tions Office on July 10, 1974. In accordance with Section 6.7 2.A of the Technical Specifications. Aooendix A of DPR-56 for Unit 2 Peach GuiLun ALunis Funci 3iaLivo, tiic iviivwing repurL is being submittea to the Directorate of Licensing as an Abnormal Occurrence:

Reference:

License Number DPR-56 Technical Specification Table 3.2.C Report No. 50-278-74-1 Report Date: July 19,1974 Occurrence Date: July 9, 1974 Facility: Peach Bottom Atomic Power Station R.D. 1, Delta, Pennsylvania 17314 Identification of Occurrence:

Failure of IRM channel "H",to produce a Downscale Trip.

Conditions Prior to Occurrence:

Initial fuel loading was in progress with 68 fuel assemblies 7 loaded. , Li (

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Description of Occurrence: \

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l During a routine surveillance. test of the IRM system the.

j channel "H" IRM would not respond below 5% on the 125% scale when a 7 l simulated ciectrical signal was applied to its input. This malfunction l would render the IRM downscale rod block from channei "H" inoperable.

j .,.m.

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l 8401240061 740719 M PDR ADOCK 05000278 S PM

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O "Mr.,*A. Giambus so O July 19,1974 -

Page 2 The downscale trip is set at > 2 5% on the 125% scale.

Designation of Apparent Cause of Occurrence:

An investigation by the instrument technician revealed that the amplifier and attenuator circuit board was generating an oscillation whose magnitude prevented the channel electronics from responding to a low value signal such as 5% on the 125% scale.

Analysis of Occurrence: .

Due to the redundancy of the IRM channels (any one of the eight channels can produce a rod withdrawal block) and the immediate verification of the operability of the other seven channels, this occurrence has minimal safety implications.

• 1 Corrective Action:

a

)

A defective Zener diode was found to be the cause of the mal- f i

function. The diode was replaced, "in kind" and the IRM channel was returned to service.

Failure Data: -

o p. .. ; e4 f ailurn of tinis type.

Very truly yours, [

W /

M. . Cooney Ass t Gen' t Sup rintendent Generation Division cc: Mr. J. F. O'Reilly ,

Director, Region i United States Atomic Energy Commission 631 Park Avenue King of Prussia, PA 19406

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