05000346/LER-1979-129-03, /03L-0:on 791211,during Control Room Emergency Vent Sys 18-month Test ST 5076.02,charcoal Filter Bank in Unit 1-2 Failed to Meet Required Efficiency.Caused by Leak Between Filter Plate & Assembly.Plate Nuts Properly Torqued

/03L-0:on 791211,during Control Room Emergency Vent Sys 18-month Test ST 5076.02,charcoal Filter Bank in Unit 1-2 Failed to Meet Required Efficiency.Caused by Leak Between Filter Plate & Assembly.Plate Nuts Properly Torqued

ML19257B308
Person / Time
Site:	Davis Besse
Issue date:	01/08/1979
From:	Bernard Thomas TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19257B302	List: 05000346/LER-1979-129, Forwards LER 79-129/03L-0 05000346/LER-1979-129-03, /03L-0:on 791211,during Control Room Emergency Vent Sys 18-month Test ST 5076.02,charcoal Filter Bank in Unit 1-2 Failed to Meet Required Efficiency.Caused by Leak Between Filter Plate & Assembly.Plate Nuts Properly Torqued
References
LER-79-129-03L, LER-79-129-3L, NUDOCS 8001150546
Download: ML19257B308 (2)

LER-1979-129, /03L-0:on 791211,during Control Room Emergency Vent Sys 18-month Test ST 5076.02,charcoal Filter Bank in Unit 1-2 Failed to Meet Required Efficiency.Caused by Leak Between Filter Plate & Assembly.Plate Nuts Properly Torqued

Event date:
Report date:
3461979129R03 - NRC Website

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-150 DATE OF EVENT: December 11, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Control Room Emergency Ventilation System (EVS)

Train 1-2 Charcoal Bank F22-2 failed due to low efficiency 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 5076.02, Control Room EVS 18 Month Test, the charcoal filter bank in Control Room EVS Unit 1-2 failed to meet Surveil-lance Technical Specification 4.7.6.1.g which requires, during Modes 1 through 4, each unit remove ?_99% of the test gas while operating the system at a flow rate of 3300 cfm 10%.

Since the station was in Mode 5 at the time of the occurrence, the unit did not enter into an action statement.

This is being reported to document a component failure.

Designation of Apparent Cause of Occurrence: The cause of the filter low efficiency was leakage located between the filter plate and assembly. The cause of this leak-age was due to insufficient plate / assembly pressure applied to the gaskets which could 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 redundant Control Room EVS Train 1-1 was operable.

Corrective Action

The nuts of the filter cells were torqued under Maintenance Work Order 79-3755 on December 17, 1979. This provided the necessary seal. On December 17, 1979, ST 5076.02 was performed successfully. A procedure change will be made to prevent a similar occurrence 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 5076.02, Control Room EVS 18 Month Test, is always used following any Control Room EVS work to ensure operability after mainten-ance.

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

LER #79-129 1749 074