05000346/LER-1979-056-03, /03L-0 on 790501:excesssive Leakage Found Through Containment Isolation Valve NN236.Caused by Either Dirt on Valve Seating Surface or Slipped Actuator Linkage.Valve Cleaned & Recalibr

/03L-0 on 790501:excesssive Leakage Found Through Containment Isolation Valve NN236.Caused by Either Dirt on Valve Seating Surface or Slipped Actuator Linkage.Valve Cleaned & Recalibr

ML19269D551
Person / Time
Site:	Davis Besse
Issue date:	05/29/1979
From:	Rohrer E TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19269D549	List: 05000346/LER-1979-056, Forwards LER 79-056/03L-0 05000346/LER-1979-056-03, /03L-0 on 790501:excesssive Leakage Found Through Containment Isolation Valve NN236.Caused by Either Dirt on Valve Seating Surface or Slipped Actuator Linkage.Valve Cleaned & Recalibr
References
LER-79-056-03L, LER-79-56-3L, NUDOCS 7906040239
Download: ML19269D551 (2)

LER-1979-056, /03L-0 on 790501:excesssive Leakage Found Through Containment Isolation Valve NN236.Caused by Either Dirt on Valve Seating Surface or Slipped Actuator Linkage.Valve Cleaned & Recalibr

Event date:
Report date:
3461979056R03 - NRC Website

text

U.S. NUCLEAR REGULATORY COMMISSION NRC FORM J66 (7 77)

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8 60 61 DOCK ET NUMBE R 68 63 EVENT DATE 14 75 REPORT DATE 80 EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h o 2 At 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on 5/1/79, excessive leakage was found through Containment Isolation I

gg l Valve NN236. This is part of the nitrogen supply line through penetration P44B.

l lST 5061.02 confirmed the leaking. Being in Mode 5, the unit did not enter the Action l o 4 l Statement of T.S. 3.6.1.2, which requi es all isolation valves be operable in Modes 1 l o s 0 6 l2, 3, and 4.

This occurrence is being reported as documentation of a component f ailurij.

The l l There was no danger to the health and saf ety of the public or station personnel.

o 7 0 a l redundant isolation valves of this penetration were operable.

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS l t l 0 l l The cause was either a slight amount of dirt on the valve seating surface or a slippedl the valve from seating fully. Under MWO 79-1859,j J g l actuator linkage which would prevent l the valve was disassembled and cleaned. The actuator linkage was adjusted and recali-

, 2 brated, and was retested successfully and declared operable on May 7, 1979.

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DVR 7 9-069 NAME OF PREPARER

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-57 DATE OF EVENT: May 1, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Containment Isolatian Valve NN 236 failed leak rate test.

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

Description of Occurrence:

At 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on May 1, 1979 during the performance of Containment Vessel Local Leak Rate Surveillance Test ST 5061.02, excessive leakage was found through Containment Isolation valve im 236. This is part of the nitrogen supply line through penetration P44B. Technical Specification 3.6.1.2 requires all isolation valves to be within the leak rate 'imits when in Modes 1, 2, 3, and 4.

Being in Mode 5, the unit did not enter an Action Statement. This occurrence is being reported as documentation of a component failure.

Designation of Apparent Cause of Occurrence: The cause of the occurrence was at first thought to be due to a damaged valve seat. The valve was disassembled, but no valve seat damage was discovered. The cause was either a slight amount of dirt on the valve seating surf ace or a slipped actuator linkage which would prevent the valve from seating fully.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. The redundant isolation valves of penetration P44B are NN 58 and NN 55 which were operable during this time and would have provided isola-tion.

Corrective Action

Under Maintenance Work Order 79-1854, the valve was disassembled, the seat cleaned and reassembled by maintenance personnel. No significant valv seat damage was found.

Instrument and Control personnel recalibrated the pneumatic valve operator, cycled the valve, and found it seated properly. The valve was re-tested and found to be within the allowable leak rate.

It was declared operable Monday, May 7, 1979.

Failure Data:

There have been no previous failures of this type valve operator.

LER #79-056 2 2 5 9 a_. 2 3