ML19211C745

LER 79-129/03L-0:on 791211,during Control Room Emergency Ventilation Sys 18-month Test,Charcoal Filter Bank in Unit 1-2 Failed to Meet Efficiency Required Per Tech Specs. Caused by Leakage Between Filter Plate & Assembly

ML19211C745
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
ML19211C743	List: ML19211C742 ML19211C745
References
LER-79-129-03L, LER-79-129-3L, NUDOCS 8001140391
Download: ML19211C745 (2)

Text

U. S. NUCLE AR REGULATORY COYMISSION NRC FORM OG6 (7 77)

LICENSEE EVENT REPORT CO,N TROL BLOCK:

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CON'T l0lil EVENT DATE 14 75 REPORT D ATE c3 7 8 60 Gl DOC 8.ET NUVd E R 6d t,J EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h o 2 lOn December 12, 1979 during the performance of ST 5076.02. Control Room Emernencv I o 3 IVcntilation System (EVS) 18 Month Test, the charcoal filter bank in EVS Unit 1-2 1 o 4 l failed to meet the required efficiency as listed in Technical Specification 4.7.6.1. l l Tis] l Being in Mode 5 at the time of the occurrence, the station did not enter an action l o G l statement. This is being reported to document a component failure. There was nO I o 7 l danger to the health and safety of the public or station personnel. The redundant I i

o 8 l train was operable had it been required. (NP-33-79-150)

SYSTEM CAUSE CAUSE COMP. VALVE CODE CODE SUDCODE COMPONENT CODE SUBCODE SUBCODE 7

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l33B lgl34 Cl@ l ZlQ l36Zl@ [0 l0 l0 k [ 41 YQ l YlQ 43 l@ lB 44 l0 l7 l5 l@ 47 33 3/ 40 42 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS i o lThe cause of the low filter efficiency was leakage between the filter plate and the

[TTT1 l assembly. This leakage was due to insuf ficient pressure applied to the casket. Underl

, ., l Maintenance Work Order 79-3755, the nuts holding the plate to the assembiv were  !

, , torqued to 75 in-lbs. The unit then successfully met the requirements of ST 5076.02 ii14[ l on December 17, 1979. 80 I

7 8 9 A S  % POV.E R OTHER STATUS blSCO RY DISCOVERY DESCRIPTION l

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DVR 79-196 NAME OF PREPARER Bradley S. Thomas PHONE: -2M-20, M . q

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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

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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 char' coal 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 2.99% 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 1779-129 .