ML20248G358

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Responds to NRC Bulletin 88-010 Re Nonconforming molded-case Circuit Breakers.Breakers Not Traced to Mfg Removed from Warehouse to Preclude Use.Visual Insp of Nontraceable Breakers Will Be Performed as First Step
ML20248G358
Person / Time
Site: Rancho Seco
Issue date: 04/03/1989
From: Croley B
SACRAMENTO MUNICIPAL UTILITY DISTRICT
To: Knighton G
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
AGM-NTS-89-088, AGM-NTS-89-88, IEB-88-010, IEB-88-10, NUDOCS 8904130402
Download: ML20248G358 (2)


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i)SMUD- SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S Street, P.o. Box 16830, Sacramento CA 95852-1830,(916) 452 3211 l

AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA AGM/NTS89-088 April 3, 1989  !

l U. S. Nuclear Regulatory Commission Attn: Document Control Desk Hashington,.DC 20555 Docket No. 50-312 Rancho Seco Nuclear Generating Station License No. DPR-54 ,

i NRC BULLETIN NO. 88-10: NONCONFORMING MOLDED-CASE CIRCUIT BREAKERS Attention: George Knighton In response to the subject Bulletin, the District performed a review of the warehouse stock of Class 1 molded-case circuit breakers (MCCBs) to determine the extent of traceability to the circuit breaker manufacturer (CBM). The applicabl_e stock codes contain a total of ninety MCCBs,_ representing six manufacturers'and twelve suppliers. Of the ninety MCCBs in stock, forty-one have been traced to the manufacturer. In addition, eighteen of the non-traceable MCCBs are of riveted, single pole design with a purchase price of less than ten dollars. The remaining thirty-one MCCBs are of varying sizes, manufacturers, and suppliers.

The MCCBs which have not been traced to the manufacturer have been removed from the warehouse to preclude their issue for use. The District will perform a visual' inspection of these non-traceable breakers as an initial means of j determining the extent of questionable origin breakers at Rancho Seco. This inspection will be completed by April 30, 1989. Identification of refurbished breakers will result in the District re-evaluating the extent and schedule for other activities. Regardless of the results of this inspection, these breakers will not be returned to stock without returning the breaker to the original manufacturer for inspection and/or testing.

Rancho Seco procedures require testing of MCCBs prior to their installation as  !

replacements or modifications. This testing verifies that the breaker will -!

function as designed, and includes: 1

  • Visual examination for signs of degradation.
  • Exercising the breaker to ensure mechanical operability.
  • Meggaring the breaker to assess the insulation (dielectric) integrity.
  • Verification that the time-current trip, long-time delay trip, and instantaneous trip characteristics,*as applicable, for the breaker are  ;

as designed. g 8904130402 890403 PDa ADOCK 05000312 Q PDC f g RANCHO SECO NUCLEAR GENERATING STATloN D 1444o Twin Cities Road, Herald, CA 95638 9799;(209) 333-2935  ;

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George Knighton AGM/NTS89-088 The District has an extensive preventive maintenance program which includes MCCBs. One-third of the Class 1 MCCBs are to be inspected each refueling; thu;, each of the Class 1 MCCBs will be inspected every third refueling outage. Testing includes both long-time delay trip characteristics and insulation resistance checks.

Members of your staff with questions requiring additional information or clarification may contact Mr. Dave Swank at (209) 333-2935, extension 4920.

Sincerely, 1

Bob G. Croley Assistant General Manager i Nuclear Technical Services {

cc: J. B. Martin, NRC, Hainut Creek A. D'Angelo, NRC, Rancho Seco l

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