ML20236M958

Part 21 Rept 7 Re Cracks & Chipping Discovered on Bus Bar Insulators Mounted on Power Conversion Products,Inc. Initially Reported on 870708.Damaged Insulators Replaced. Ref Drawings Revised

ML20236M958
Person / Time
Site:	Rancho Seco
Issue date:	07/20/1987
From:	Andognini G SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
REF-PT21-87, REF-PT21-87-158-000 7, GCA-87-337, PT21-87-158, PT21-87-158-000, NUDOCS 8708110310
Download: ML20236M958 (2)

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SACRAMENTO MUNICIPAL UTILITY DISTRICT O P. O. Box 15830, Sacramento CA 95852-1830,(916) 452-3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA

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GCA 87-337.  !

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5h 5 l a w =R U. S. Nuclear Regulatory Commission O~N $ ,

Attn:

Region V J. B. Martin, Regional Administrator <> g I

Office of Inspection and Enforcement a 1450 Maria Lane, Suite 210 co l l

Halnut Creek, CA 94596 l

CXKET NO. 50-312 RANCHO SECO NUCLEAR GENERATING STATION

' LICENSE NO. DPR-54 10 CFR 21 REPORT NO. 07, CRACKED AND CHIPPED INSULATORS DISCOVERED ON REGULATING TRANSFORMERS l

Dear Mr. Martin:

In accordance with 10 CFR 21(b)(2), the Sacramento Municipal Utility District hereby submits a written report documenting the notification made by Mr. R. Colombo of the District to Mr. L. Miller of Region V N.uclear Regulatory Commission (NRC) on July 8, 1987.

-The notification concerns the cracks and chipping discovered on bus bar insulators mounted on the Power Conversion Products Inc. Regulated Dry-Type Transformers, 30 KVA design, Model No. RTF-480/120-30.

On May 1, 1987, a Nonconforming Report (NCR) was initiated by plant personnel to document cracks and chipping on the bus bar insulators for TB2-1 and TB2-2

. located in transformers X31A2, X3182, X31C2 and X3102. The disposition of the NCR indicated the damage was caused by overtightening of the insulator support bolts during assembly.

The damaged insulators were replaced with new ones supplied by Power

. Conservation Products Inc. Power Conversion Products Inc., the equipment manufacturer, has determined the maximum torque to be applied to the insulator support bolts was 30 in lbs. The work was completed on June 2, 1987.

Additionally, the reference drawings are being revised to add a note to identify the maximum allowable torque value for the insulator support bolts.

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' RANCHO SECO NUCLEAR GENERATING STATION O 1444o Twin Cities Road, Herald, CA 95638 9799;(209) 333-2935

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GCA 87-337 L  ?- J'.B. Martin L JUL 2 01987 The cracks and chipping ~of the insulators have the potential to ground fault

'the vital 120V AC buses in the Auxiliary Building. This condition was detected during the installation.of the static transfer switches during the current outage. The Regulating Transformers have not been released to Operations.

The Plant Review Committee (PRC) reviewed the NCR recommending a 10 CFR 21 Report' be submitted in accordance with 10 CFR 21.3(d)(1).

Power Conservation Products Inc. are best qualified to provide to the NRC a listing of facilities that have been supplied the Regulating Transformers, Model RTF-480/120-30.

If there are any questions concerning this report, please contact Mr. Ron Colombo at (916) 452-3211, extension 4235.

Sincerely, RYOff**

Gi Carl Andognini Chief Executive Officer, Nuclear cc: A. D'Angelo l G. Kalman J. Taylor-(3)

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