05000010/LER-1977-040-03, /03L-0:on 771017,Channel 1 (RIC-281) Found to Trip at 132%.Caused by Instrument Drift.Trip Setpoint Readjusted to 115%.High Neutron Flux Monitor Testing Will Continue Monthly Per Dis 700-4,verifying Operability

/03L-0:on 771017,Channel 1 (RIC-281) Found to Trip at 132%.Caused by Instrument Drift.Trip Setpoint Readjusted to 115%.High Neutron Flux Monitor Testing Will Continue Monthly Per Dis 700-4,verifying Operability

ML19338E410
Person / Time
Site:	Dresden
Issue date:	11/03/1977
From:	Lindberg C COMMONWEALTH EDISON CO.
To:
Shared Package
ML19338E409	List: 05000010/LER-1977-040, Forwards LER 77-040/03L-0 05000010/LER-1977-040-03, /03L-0:on 771017,Channel 1 (RIC-281) Found to Trip at 132%.Caused by Instrument Drift.Trip Setpoint Readjusted to 115%.High Neutron Flux Monitor Testing Will Continue Monthly Per Dis 700-4,verifying Operability
References
LER-77-040-03L, LER-77-40-3L, NUDOCS 8009290533
Download: ML19338E410 (3)

LER-1977-040, /03L-0:on 771017,Channel 1 (RIC-281) Found to Trip at 132%.Caused by Instrument Drift.Trip Setpoint Readjusted to 115%.High Neutron Flux Monitor Testing Will Continue Monthly Per Dis 700-4,verifying Operability

Event date:
Report date:
0101977040R03 - NRC Website

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REPOHT DATE 60 EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES O'o j p l During monthly surveillance DIS 700-4 Channel #1 (RIC-281) found to trip at 132%.

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o,3 i ; Tech Spec table 3.1.1.c requires high neutron flux trip of </-123% of scale.

Safety l i o,4 ; g significance minimal because remaining two channels (#3,#5) of "A" trip channel were l IOlsl I perable within required tech spec range (T.S.3.1).

"B" trip channel unaffected.

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{ O l6 l l Previous occurrence reported under 50-010/77-3, 12, 13 and 31; 50-010/76-8 and 18.

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!3 l0l] Cause due to instrument drift. Trip setpoint readjusted to 115%.

High neut'ron lux l j- ;3j l monitors will continue to be tested monthly per DIS 700-4 to verify operabilitv. In I

,,,7, j addition, previous drift problems will be analyzed and a new setpoint determined to l

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ATTACHMENT TO LICENSEE EVENT REPORT 77-040/03L-0 COMMONWEALTH EDISON COMPANY (CWE)

DRESDEN UNIT 1 (ILDRS-1)

DOCKET # 050-0010 While performing high neutrop flux monthly surveillance DIS 700-4 Channel

1. 1 (RIC 281) was found to trip at 132%. Three high neutron flux instrument channels are provided for each trip system.

High Neutron Flux Instrument Channels #1, #3, #5 operate contacts in the "A" trip channel and Instrument Channe?.s #2, #4, #6 operate contacts in the "B" trip channel. Tech Spec 3.1 maintains that a minimum of two channels per trip channel must be oper-able. The inability of Channel #1 to trip at the designated limit did not pose any safety implications because the remaining two channels (Ch #3, 5) of the "A" trip channel remained operable. The "B" trip channel was unaf-fected. The micromicroammeter is manufactured by General Electric Catclogue No. 534E745G4.

Tech Spec Table 3.1.1.C require a High Neutron Flux Trip of < 123% of scale. The Dresden setpgint is 114 to 116% increasing.

This is a repetitive occurrence as reported under 50-010/1977-3,12,13 and 31; 50-010/1976-8 and 18.

The trip setpoint was readjusted to 115%. The rause was attributed to instrument drift. The trip setpoints will continue to be tested per monthly surveillance DIS 700-4 to verify operability below the 123% Tech Spec Iimit.

In addition, previous drif t problems will be analyzed and a new setpoint determined to eliminate recurrence.

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NRC Foru 195

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u.s. NUCLE AR R37ULATOnY C' 4tSSION DOCKE NUMBER r2 70) h=== [h

.~ NRC DISTRIBUTION FOR PART 50 DOCKET MATERI AL ANCIDENT REPORT FROM Co::Inonwealth Edison DATE OF DOCUMENT James G. Keppler 11/03/77 Morris, Illinois 60450 B. B. Stephenson CATE RECEIVCD l

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Licensee Event Report (R0 50-010/77 40/03L.0) on 10/17/77 concerning the inability of J

Channel #1 to trip at the designated limit,....

while performing high neutron flux monthly surveillance DIS 700 4.....

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PLANT NAME: Dresden Unit No.1 NOTE: IF PERSONNEL EXPOSURE IS INVOLVED SEND RJL-11/17/,77 DIRECTLY TO KREGER/J. COLLINS FOR ACTION /INFORMATION l 3 RANCH CHIEF:

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