ML20086J535

Telecopy AO 74-1:on 740709,intermediate Range Monitor Channel H Failed to Produce Downscale Trip.Caused by Amplifier & Alternator Circuit Board Generating Oscillation Whose Magnitude Prevented Channel from Responding Signal

ML20086J535
Person / Time
Site:	Peach Bottom
Issue date:	07/10/1974
From:	Ullrich W PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20086J533	List: ML20086J528 ML20086J535
References
AO-74-1, NUDOCS 8401240066
Download: ML20086J535 (2)

Text

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Mr. James P. O'Reilly, Director July 10, 1974 N b, y 3 7,, ggg I

United States Atomic Energy Coc:miesion Directorate of Regulatory Operations g--2. h j 631 Park Avenue King of Prussia, Penncylvania 19406

Subject:

Abnorm 1 Occurrence 24-Rour Notification Confirming R. S. Fleischmann's phone conversation with Mr. R. A. Feil, A.E.C. Region 1 Regulatory Operations Office on July 10, 1974.

Reference:

License Number DPR-56 ., ;

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f' Technical Specifiention Table 3 2.C Report No.: 50-278-74-1 -

Report Date: July 10, 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 Tiip.

Conditions Prior to Occurrence:

Initial fuel loading was in progrecs with 68 fuel assemblies loaded.

Description of Occurrence:

During a routine surveillance test of the IRM system, the Channel 'T' IRM would not respond below 5 on the 12% acale when a sic:ulated electrical cignal was applied to its input. This malfttnetion would render the IRM downscale rod block from Channel 'T' inoperable. The downecale trip is set at 3 2 5 on the 12% scale.

Designation of Apparent Cause of Occurrence:

An investigation by the instrument technician revealed that the amplifier and alternator circuit board was generating an oscillation whose magnitude prevented the channel electronics from responding to a low value signal such as % on the 12% scale.

Analysis of Occurrence:

Due to the redundnney of the IRM Channels (any one of the ei 6ht 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. ,

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Corrective Action:

The proble= of the undesirable oscillations is under investigation. As a te=porary measure, the downceale trip setpoint of Channel "H" was moved up to 6% on the 125% neale. This setting would allow operation of the down-scale trip when the instrument. does not respond below %.

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Very truly yours,

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l<' e-W. T. Ullrich Superintendent Peach Bottom Atomic Power Station.

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