ML19326A564

RO NP-33-77-24:on 770716,steam Generator 1 Channel 1 Level of Steam & Feedwater Rupture Control Sys Inoperable.Caused by Defective Design in Power Supply to Instrumentation. Defective Power Supply Replaced

ML19326A564
Person / Time
Site:	Davis Besse
Issue date:	08/10/1977
From:	Lingenfelter J TOLEDO EDISON CO.
To:
Shared Package
ML19326A533	List: ML19326A532 ML19326A564
References
NUDOCS 8002040737
Download: ML19326A564 (2)

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>Qlae Steam Generator 1, Channel 1 Level (LSLL SP9B8) of the Steam knd Feed- J i so

@laswater Ruoture Control System Instrument Channels was inoperhble. -

The l g ; channel was tripped. This is not a repetitive occurrence. so gles (NP-33-77-24) w 7 89 l so 8L 1

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TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NGCLEAR POWER STATION

/g \- SUPPLEMENTAL INFORMATION FOR LER NP-33-77-E 5  !

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DATE OF EVENT: July 16, 1977 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCUFRENCE:

One of the Steam Feedwater Rupture Control System Instrument Channels, Steam Generator 1 Level. Channel 1 (LSLL S?9B8) was in-operable. '

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

Description of Occurrence:

On both 2340 hours0.0271 days <br />0.65 hours <br />0.00387 weeks <br />8.9037e-4 months <br /> on July 16, 1977 and 0120 hours0.00139 days <br />0.0333 hours <br />1.984127e-4 weeks <br />4.566e-5 months <br /> on July 17, 1977, Steam and Feedwater Rupture Control System (SFRCS) Steam Generator 1,_ Channel 1 Level (LSLL SP938) was found to be inoperable. Power supply to the channel was lost for both occurrences which tripped the :hannel.

Instrument and Control (I&C) technicians checked a fuse in the 24 volt power ~

supply, time. found it to be satisfactory, and returned it to the power supply each When the technicians replaced the fuse, power was restorea to the. channel.

The station, during the two periods ~ of loss of power supply to Steam Generator 1,

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Channel 1 Level (LSLL CP9B8), was placed in Action Statement 13 of Technical Specification 3.3.2.2.

This Action Statement applies to Mode 3, Ho.t Standby, which the station was in at the time.

t Designation of Apparent Cause of Occurrence:

The' cause of the occurrence was a design problem in the power supply. The power supply was returned to the manu-facturer, Sorenson (a division of Raytheon). A design change was made to the 24 volt power supply at Sorenson, and it was returned to the station. The altered power supply was then installed in the cabinet and the channel was declared operable at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> on July 23, 1977.

Analysis of Occurrence:

lost, Since the channel tripped.when the power supply was and there were three other channels still available, there was no danger to the health and safety of the public or station personnel.

_ Corrective Action:

on the morning of July The23,defective 1977.

power supply was replaced and declared operable Shutdown, and Technical Specification 3.3.2.2 was not applicable.The plant was,

, changes were also completed on all the other power supplies (7) in the Steam andSimilar desi Feedwater Rupture Control Sys. tem by 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> on July 23, 1977.

g- _ Failure Data: No previous similar events have occurred.

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