ML19209D115

Interim Deficiency Rept Re Trip Units Drawing More Current than Specified Causing Power Supplies to Be Inadequate. Corrective Action Will Be Complete by 800321

ML19209D115
Person / Time
Site:	Grand Gulf
Issue date:	10/02/1979
From:	MISSISSIPPI POWER & LIGHT CO.
To:
Shared Package
ML19209D111	List: ML19209D110 ML19209D115
References
NUDOCS 7910190419
Download: ML19209D115 (1)

Text

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, INTERIM REPORT FOR PRD 79/12 AS DEFINED IN 10 CFR 50.55(e)

1. Description of Deficiency:

Rosemount has identified a problem with their Model 510 DU master and slave trip units. The maximum current drain for the master and slave trip units exceed the original specified value. The current required by the .ross failure circuitry, which consists of the gross failure LED current and the silicon controlled rectifier (SCR) biasing current and the current required for the trip output LED, were not considered by Rosemount in the original specification. In addition, Rosemount has recently redesigned the trip units due to an increase in the supply current required to operate the 555 integrated circuit which is , art of the negative 4.7 volt power supply.

II. Safety Inplication:

Bechtel has reviewed the power sources for all the safety-ralated Rosemount Model 510 DU master and slave trip units to determine if the larger current drains would adversely affect the operation of the systems to which they are designated. As a result of this evaluation, it has been determined that po*7er supplies P41-JY-K600 A and B for Units 1 and 2 (Bailey Model 808094003) are not large e'nough to handle the larger maxidum current drains specified by

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Rosemount. All other power sources have adequate capacity to handle the larger current drains. ))[j 34[

III. Corrective Action Taken:

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Corrective action is expected to be completed by March 21, 1980, and submitted to you in a final report. d7 7 910190 t ,-1gg

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