05000346/LER-1979-128-03, /03L-0:on 791210,during Emergency Ventilation Sys Test,Charcoal Filter Bank in Unit 1-1 Failed to Meet Efficiency Limit in Modes 1-4.Caused by Leakage Between Filter Plate & Assembly Due to Insufficient Gasket Pressure

/03L-0:on 791210,during Emergency Ventilation Sys Test,Charcoal Filter Bank in Unit 1-1 Failed to Meet Efficiency Limit in Modes 1-4.Caused by Leakage Between Filter Plate & Assembly Due to Insufficient Gasket Pressure

ML19211C766
Person / Time
Site:	Davis Besse
Issue date:	01/08/1980
From:	Bernard Thomas TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19211C763	List: 05000346/LER-1979-128, Forwards LER 79-128/03L-0 05000346/LER-1979-128-03, /03L-0:on 791210,during Emergency Ventilation Sys Test,Charcoal Filter Bank in Unit 1-1 Failed to Meet Efficiency Limit in Modes 1-4.Caused by Leakage Between Filter Plate & Assembly Due to Insufficient Gasket Pressure
References
LER-79-128-03L, LER-79-128-3L, NUDOCS 8001140462
Download: ML19211C766 (2)

LER-1979-128, /03L-0:on 791210,during Emergency Ventilation Sys Test,Charcoal Filter Bank in Unit 1-1 Failed to Meet Efficiency Limit in Modes 1-4.Caused by Leakage Between Filter Plate & Assembly Due to Insufficient Gasket Pressure

Event date:
Report date:
3461979128R03 - NRC Website

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L0 t> 1 DOCK E T ?.UMB EM EVENT DESCRIPTION AND FROBABLE CONSEQUENCES h l During the performance of ST 5067.02, Emergency Ventilation System (EVS) 18 Month or l

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l Special Test, the charcoal filter bank in EVS Unit 1-1 failed to meet the efficiency l

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l11mit as required by T.S. 3/4.6.5.1 while in Modes 1 thru 4.

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4 time of the finding, the station did not enter an action statement. This is being l

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j o 6 l reported to document a ec-ponent failure. There was no danger to the health and _

l safety of the public or station personnel. The redundant EVS Train 1-2 was operable l

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had it been required.

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h [The cause of the low filter efficiency was leakage between the filter plate and the i

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I g,17llUnder Maintenance Work Order 79-3756, the nuts holding the plate were torqued to 75 in-lbs.

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I liI41 l December 17, 1979.

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s TOLEDO EDISON COMPANY DAVIS-BESSE UUCLEAR POWER STATION UNIT ONE SUPPLE'4 ENTAL INFORMATION FOR LER MP-33-79-149 DATE OF EVENT: December 10, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE:

Emergency Ventilation System (EVS) 1-1 Charcoal Bank

1. 2 F19-1 C-2 leakage 4

Conditions Prior to Occurrence: The unit was in Mode 5, with Power (MWT) = 0, and Load (Gross MWE) = 0.

Description of Occurrence: While performing ST 5067.02, EVS 18 Month or Special Test, the charcoal filter bank in the EVS Unit 1-1 (F19-1, C2) failed to meet ST 5067.02 Acceptance Criteria 7.1 (i.e., the charcoal bank capable of removing 2L 99% of the halogenated hydrocarbon refrigerant test gas with 8000 cfm + 10% of air flow).

Since the station was in Mode 5 at the time of the event, the unit did not enter an action statement. This is being reported as documentation of a component failure.

Designation of Apparent Cause of Occurrence: The cause of the low filter efficiency was leakage located between the filter plate and assembly.

Leakage was due to in-sufficient plate / assembly pressure applied to the gaskets which may have been induced by normal vibration.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. The unit was in Mode 5, the redundant EVS Train 1-2 was operable, and there was no fuel in the spent fuel pool.

Corrective Action

The nuts of the filter cells were torqued under Maintenance Work Order 79-3756 on December 17, 1979.

This provided the necessary seal. On December 17, 1979, ST 5067.02 was performed successfully. A procedure change will be made to prevent similar occurrences by requiring that the nuts to the filter cells be torqued to 75 in-lbs and a light source leak test be performed following the removal and re-assembly of the filter. This ST 5067.02, EVS 18 Month or Special Test, is always used following any EVS work to ensure operability af ter maintenance.

Failure Data: There have been no previous similar reportable occurrences.

LER #79-128 1 7 4 0

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