05000346/LER-1977-094-03, /03L-0:on 771116,emergency Ventilation Sys Dampers Pdv 5014A & B Failed to Modulate Correctly to Draw Down Annulus.Caused by Defective Pressure Differential Controller.Dampers Replaced & Sys Retested

/03L-0:on 771116,emergency Ventilation Sys Dampers Pdv 5014A & B Failed to Modulate Correctly to Draw Down Annulus.Caused by Defective Pressure Differential Controller.Dampers Replaced & Sys Retested

ML19326A484
Person / Time
Site:	Davis Besse
Issue date:	12/13/1977
From:	Alten B TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19326A483	List: 05000346/LER-1977-094, Forwards LER 77-094/03L-0 05000346/LER-1977-094-03, /03L-0:on 771116,emergency Ventilation Sys Dampers Pdv 5014A & B Failed to Modulate Correctly to Draw Down Annulus.Caused by Defective Pressure Differential Controller.Dampers Replaced & Sys Retested
References
LER-77-094-03L, LER-77-94-3L, NUDOCS 8002040654
Download: ML19326A484 (2)

LER-1977-094, /03L-0:on 771116,emergency Ventilation Sys Dampers Pdv 5014A & B Failed to Modulate Correctly to Draw Down Annulus.Caused by Defective Pressure Differential Controller.Dampers Replaced & Sys Retested

Event date:
Report date:
3461977094R03 - NRC Website

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03 kVE*.iCATE 14 75 RE!PCRT OATE JJ EVE'JT DESC!iPT6CN AND PRCSA8d COf.3ECUENCES h jo!:; l0n 11/16/77, during the pe formance or ST 5067.01, Emergency Ventilation System (EVS) i it was found that dampers PDV 5014A and B (on EVS Train 2) were not 3 } l Monthly Test,

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.3 CAUSE DESCRIPTION AND COPRETlVE ACTICNS h Ii60llThe pressure differcatial :entroller (PDC 5014) which controls damners PDV 5014A and i

Ii!ii iB was found to be defetiv3.

PDC 5014 was replaced and the svstem retested.

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lii2j l Train 2 was declared C,yerr. ale at 1015 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.862075e-4 months <br /> an November 22, 1977, thus removine the l i I 31 i station from the Action Statement of Technical Specification 3.6.5.1.

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DATE OF EVENT:

November 16, 1977

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l FACILITY:

Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENC2:

E=ergency 'leutilation System Train 1-2 pressure differential controller malfunction.

Conditions Prior to Occurrence: The plant was in Mode 1, with Power (MWT) = 1108 and Load (MWE) = 398.

Description of Occurrence: On November 16, 1977, Surveillance Test ST 5067.01,

" Emergency Ventilation System Monthly Test" was performed and the differential pressure was within specifications.

It was found, however, that dampers PDV 5014A and B were not modulating correctly to draw down the annulus.

Since #2 Emergency Ventilation System (EVS) Train could not serve its intended safety function, r/2 EVS Train was declared. inoperable at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> on November 16, 1977.

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hThis placed the station in the Action Statement of Technical Specification 3.6.5.1

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/which requires two operable EVS Trains in Mode 1.

An Instrument and Control Work Order (No. 749) was issued to investigate the reason for dampers PDV 5014A and B not modulating properly.

Designation of Apparent Cause of Occurrence: The pressure differential controller (PDC 5014) was then re=oved and a bench check performed. The controller was found to be heat sensitive and would fail intermittently when it was at operating temp-erature.

A new controller (PDC 5014) was installed and energized for more than twelve hours prior to re-performing Surveillance Test ST 5067.01.

EVS Train 2 then functioned properly and was declared operable at 1015 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.862075e-4 months <br /> on November 22, 1977. This removed the station from the Action Statement of Technical Specifica-tion 3.6.5.1.

Analysis of Occurrence: There was no danger to the health and safety of the public

' or to station personnel. The system was inoperable; however, it would not affect the operation of EVS Train 1-1 which would still draw down the annulus to the -0.75 inches of water setpoint if an accident requiring the EVS had occurred.

Corrective Action

The pressure differential controller (PDC 5014) was found to fail intermittently when it was at operating temperature.

Since it was not possi-ble to determine what component was responsible, the entire contraller was replaced.

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Failure Data:

There was one previous occurrence.

EVS Train 2 dampers PDV 5014A and l

B failed to modulate properly on October 19, 1977 (see LER NP-33-77-82).

Since the i

problem was found to be in PDC 5014, and it has been replaced, this occurrence should not recur.