ML19209B560

Forwards Interim Rept on Rosemont 510 Du Trip Units Drawing More Current than Planned,Causing Power Supplies to Be Inadequate.Corrective Action Is Expected to Be Completed by 800321

ML19209B560
Person / Time
Site:	Grand Gulf
Issue date:	10/02/1979
From:	Dale L MISSISSIPPI POWER & LIGHT CO.
To:	James O'Reilly
References
NUDOCS 7910100127
Download: ML19209B560 (2)

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. 'r MISSISSIPPI POWER & LIGHT COMPANY Helping Build Mississippi NM P. O . B O X 16 4 0. J A C K S O N . MISS:SSIPPI 3S205

• aC D u CTiO N OEPARTuEN' Of fice of Inspection & Enforcement October 2, 1979 U. S. Nuclear Regulatory Com.7ission Region II 101 Marie tta S treet, N.W., Suite 3100 Atlanta, Georgia 30303 Attention: Mr. J. P. O'Reilly, Director Dear Mr. O'Reilly- .

SUBJECT:

Grand Gulf Nuclear Stacion -

Bechtel Job No. 9%5 File 0260/0498/15 21 Interim Report for PRD-79/12 as Defined in 10 CFR 50.55 (e) -

AECM-79/110 Cn September 4, 1979, Mississippi Power & Light company notiGad Mr. V.

Brownlee of your office of a potentially reportable deficisney at ae Grand Gulf Nuclear Station construction site. The deficiency concerns th ? Rosemcunt 510 DU Trip Units drawing more current than originally specified ca .-ing the power supplies to be inadecuate. We have determined that this matt r is re-portable within the me *ning of 10 CFR 50. 55 (e). Details of the la est in-formation are described in the attached report.

Yours truly, L 1 Nuclear Project >bnager e J Re JDR:mic t

Attachment ,

cc: Mr. N. L. Stampley bec: Dr. D. C. ' ibt s Mr. R. B. McGehee Mr. Adrian Zeccaria Mr. T. B. Conner Mr . J . N. Wa rd Mr. D. M. Laka Mr. R. L. Scott Mr. Victor Stello, Jr., Dir g : Tilts COPY FOR Division of Inspection & Enrorcemen: Mr. W. L. .2il U. S. Nuclear Regulatory Commission Mr. J. P. 21cCaughy Washington, D. C. 20555 Mr. T. E.

• aves Mr. C . K. icCcy Mr. J. C. Fuller File Q

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M e mt e r W dale St ,t h U thitie s S'/s te m jjzj lIs~r q/g

A 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 DC master and slave trip units. The maximum current drain for the master and slave trip units exceed the original specifiec value. The current required by the gross f ailure 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 aich is part of the negative 4.7 volt power supply.

II. Safety Implicatica:

,Bechtel has reviewed the power sources for all the safety-rela,ted

• Rosemount Model 510 DU master and slave trip 11:s 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 power supplies P'l-JY-K600 A and B for Units 1 and 2 (Bailey Model 308094003) are not large enough to handle the larger maximum curre it drains specitied by Rosemount. All other power sources have adequate capacity to handle the larger current drains.

III. Corrective Action Taken:

Corrective action is expected to be completed 'ay March 21, 1983, and submitted to you in a final report.

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