ML19312E593

Third Interim Deficiency Rept Re Defective Topaz Inverters. Complete Corrective Action Plan Unresolved.Proposed GE Mods, Re Installation of Protective Filtering Devices on Inverter Input,Under Evaluation.Final Rept to Be Submitted by 800818

ML19312E593
Person / Time
Site:	Grand Gulf
Issue date:	05/15/1980
From:	Dale L MISSISSIPPI POWER & LIGHT CO.
To:
References
AECM-80-103, NUDOCS 8006050357
Download: ML19312E593 (2)

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MISSISSIPPI POWER & LIGH,T COMPANY Helping Build Mississippi P. O. B OX 16 4 0, J A C K S O N, MI S SIS SIP PI 3 9 2 d 5 encoucreo= osaanvus=, May 15, 1980 Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Region II --

101 Marietta Street, N.W., Suite 3100 -

Atlanta, Georgia 00303  ;

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ATTENTION: Mr. J. P. O'Reilly, Director -

SUBJECT:

Grand Gulf Nuclear Station Units 1 and 2 Docket Nos. 50-416/417 File 0260/15525/15526 PRD-79/17, Interim Report #3, Defective Topaz Inverters AECM-80/103

Dear Mr. O'Reilly:

On September 9, 1979, Mississippi Power & Light Company notified Mr. J. K. Rausch of your office of a Potentially Reportable Deficiency (PRD) at the Grand Gulf Nuclear St tion (GGNS) construction site. The deficiency concerns defective inverters manufactured by Topaz Electronics for equipment supplied by General Electric.

This deficiency was determined to be reportable under 10 CFR 50.55(e) and war reported as such in our letter to you, AECM-80/32, dated January 31, 1980.

General Electric has proposed modification to the inverters that will correct the deficiency noted. This modification is being evaluated at this time. Our corrective action plan is contingent on this evaluation.

We expect to provide our final report on this issue no later than August 18, 1980. Our interim report is attached.

Yours truly, L. F. Dale b Nuclear Project Manager JGC/JDR:lj J;14s

Attachment:

PRD-79/17 cc: Mr. N. L. Stampley Mr. Victor Stello, Jr., Director Mr. R. B. McGehee Division,of Inspectica & Enforcement Mr. T. B. Conner ,

U. S. Nuclear Regulatory Commission

- Washington, D. C. 20555 8006050 357 Member Middle south utilities system aeme e Wii% gen 6 64**6WW@"N* #

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4 s Attachment to AECM-80/103 s

INTERIM REPORT #3, PRD-79/17 -

I. Description of Deficiency This deficiency concerns the failure of inverters supplied by Topaz Electronics. They are used to supply essential divisional power from the rtation batteries to the ECCS transmitter / trip unit analog sensors. The failure is associated with transient disturbances such as those generated on the 125 VDC bus from switching relay coils. Blown fuses and failed SCR's have occurred as a result of the' transient. The affected model, designated GZ, is used in Grand Gulf Units 1 and 2.

II. Safety Implications At Grand Gulf, failure of these inverters could impair or prevent the functioning of the emergency core cooling system, and thus, represents the potential for adverse effects on plant safety. For this reason this condition is judged reportable under 10 CFR 50.55(e).

III. Corrective Actions The complete corrective action plan is as yet unresolved. General Electric has proposed modifications to the inverters that will correct this deficiency. The modification consists of the installation of protective filtering devices on the inverter input. This modification is currently under evaluation. This deficiency is being tracked under MP&L PRD-79/17. We expect to provide a final report, including approved corrective actions, no later than August 18, 1980.

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