ML19319B758

RO NP-33-77-34:on 770731,emergency Ventilation Sys 1-1 Declared Inoperable.Caused by Incorrectly Set Pressure Controller PDC 5000.Controller Setpoint Corrected & Tape Removed from Atmospheric Vent.Ventilation Restored to Svc

ML19319B758
Person / Time
Site:	Davis Besse
Issue date:	08/25/1977
From:	George T, Lingenfelter J TOLEDO EDISON CO.
To:
Shared Package
ML19319B649	List: ML19319B648 ML19319B758
References
NUDOCS 8001270221
Download: ML19319B758 (2)

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, TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-33-77-34 DATE OF EVENT: July 31, 1977 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: E=ergency Ventilation System 1-1 declared inoperable. Entry into Action Statement of Technical Specification 3.6.5.1.

Conditions Prior to Occurrence: The plant was in Mode 3, with Power (MWT) = 0 and Load (MWE) = 0.

Description of Occurrence: At 0555 hours0.00642 days <br />0.154 hours <br />9.176587e-4 weeks <br />2.111775e-4 months <br /> on July 31, 1977, it was discovered that the annulus differ,ential pressure was indicated to be +7 inches of water as read on Pressure Differential Indicator PDI 5000. Annulus Differential Pressure Indicator PDI 5014 was reading 0 inches of water. Since there was no actual differential pressure in the annulus, Differential Pressure Transmitter PDT 5000 was determined to be inoperable. Through further investigation, it was also dis-covered that Pressure Differential Controller PDC 5000 was set at +8.6 inches of water instead of being at the proper setpoint of .75 inches of water. Ihese instruments being inoperable caused E=ergency Ventilation Syste= l-1 to be

['~' inoperable and placed the Station in the Action State =ent of Technical jecifica-tion 3.6.5.1.

Designation of Apparent Cause of Occurrence: After a work order was initiated, it was discovered that the atmospheric pressure tap to the pressure transmitter PDT 5000 had been taped over during the painting of the outside walls of the Auxiliary Building by construction personnel. The pressure controller, PDC 5000 had been set to the incorrect setpoint by unknown personnel. The setpoint thumb-wheel is accessible from the outside of the pressure differential controller.

Analvsis of Occurrence: Since initial criticality had not yet been attained, there was no possibility of an accident occurring that would require this system.

Also, Emergency Ventilation System 1-2 was still operable aad available if an accident had occurred. Therefore, there was no threat to the health and safety of the public or to Station personnel.

. Corrective Action: I= mediately after discovery, the pressure controller (PDC 5000) was reset to the correct setpoint of .75 inches of water. The tape was removed from the tap on the pressure transmitter, and PDT 5000 was restored to service at 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> on August 2, 1977. These actions restored Emergency Ventilation System 1-1 to operable condition and removed the Station from the Action Statecent of g Technical Specification 3.6.5.1. To prevent recurrence, the pressure controllers j and the pressure caps have been tagged to prevent personnel from changi ; set-points or covering the taps.

Failure Data: No previous similar events have occurred.

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