ML20028A857

LER 82-135/03L-0:on 821021,div 1 ID18-N009B Reactor Bldg Ventilation Process Radiation Monitor Drifted High.Caused by Failed Geiger-Muller Tube Mfg by Lnd.Tube Replaced

ML20028A857
Person / Time
Site:	LaSalle
Issue date:	11/19/1982
From:	Kay D COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20028A849	List: ML20028A848 ML20028A857
References
LER-82-135-03L, LER-82-135-3L, NUDOCS 8211290143
Download: ML20028A857 (2)

Text

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10 121 l On October 21, 1982 the Division I, IDl8-N.009B moni tor was dri f ting high. LaSalle  ;

to tal I in,,,l utilizes two redundant reactor building ventilation process radiation systems. g g,,3, g Since the Division 11 reactor buildi'ng ventilation process radiation system was  ;

per ble t 11 times, plant safety was not affected by this event. A similar event ;

l0 l6 i i g,g,g, was reported in LER 82-010/03L-0 for the "B" Fuel Pool Vent Exhaust Radiation  ;

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,i,,l The' cause of this occurrence was a failed Geiger-Huller tube manufactured by LND. l The failed tube was replaced and the monitor declared operable on October 27, 1982. l l,,,,,l I I L1_u] I Fi'TT1 l ao 7 8 9 OTHER STATUS IS RY DESCOVERY DESCRIPTION STA  % POWER l

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Diane L. Kay E_____  %

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l. LER NUMBER: 82-135/03L-0

11. LASALLE COUNTY STATION: Unit 1 111. DOCKET NUMBER: 050-373 IV. EVENT DESCRIPTION: .

Technical Specification 3 3.2 requires a minimum of two reactor building ventilation process radiation moni tors per trip system to be operable.

On October 21, 1982 the Division I, IDl8-N009B moni tor was dri f ting high and was declared inoperable.

V. PROBABLE CONSEQUENCES OF THE OCCURRENCE:

LaSalle utilizes two redundant reactor building ventilation process

radiation systems. Since the Division ll reactor building ventilation process radiation system was operable at all times, plant safety was not affected by this event.

VI. CAUSE:

The cause of this occurrence was a failed Geiger-Mullet. tube manufactured by LND. A similar type event was reported in LER 82-010/03L-0 for the "B" Fue1 Pool Vent Exhaust Radiation Monitor.

Vll. CORRECTIVE ACTION:

The failed Geiger-Muller tube was replaced with a new tube manufactured by Amperax. The monitor was declared operable on October 27, 1982.

Additional replacement of other Geiger-Muller tubes is not deemed necessary at this time for the following reasons:

A. The failed tubes appeared to have an abnormally short li fe time.

The remaining tubes have been in operation for sometime (refer te LER 82-146/03L-0 also).

B. The failed tubes all failed in the conservative direction.

C. A tube failure is readily identified during Shif tly Channel Checks and/or monthly functional checks.

Prepared by: Diane L. Kay

. - _ .