ML20203P291

Special Rept 85-06,Suppl 1:on 850421,during Routine Preventive Maint on Switchgear Bus 3A,eight Defective Bolts Found.Addl Corrective Actions Include Implementing Controls for silicon-bronze Bolt Procurement & Installation Torque

ML20203P291
Person / Time
Site:	Rancho Seco
Issue date:	04/30/1986
From:	Reinaldo Rodriguez SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Martin J NRC OFFICE OF ADMINISTRATION (ADM), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
85-06-S01, 85-6-S1, 85-6-S2, RJR-86-167, NUDOCS 8605060522
Download: ML20203P291 (2)

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SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S Street. P.O. Box 15830. Sacramento CA 95852-1830,(916) 452-3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA 6

RJR 86-167 April 30,1986 J B MARTIN, REGIONAL ADMINISTRATOR REGION V 0FFICE OF INSPECTION AND ENFORCEMENT ATTN: DOCUMENT CONTROL DESK U S NUCLEAR REGULATORY COMMISSION WASEINGTON DC 20555 DOCKET NO. 50-312 LICENSE NO. DPR-54 SPECIAL REPORT NUMBER 85-06, SUPPLEMENT 1 The Sacramento Municipal Utility District hereby submits Supplement 1 to Special Report 85-06 which was dated June 6,1985.

Special Report 85-06 was provided to the NRC as an item of potential generic interest. As indicated in the Special Report, on April 21, 1985, during routine preventive maintenance on the 3A switchgear bus, eight (8) bolts connecting the incoming line to the breaker were identified as defective. These bolts were found with their heads nearly or cor.pletely sheared off.

In addition to the actions and evaluations provided in the original Special Report, two (2) additional corrective actions will be completed as a result of the Task Force effort. The corrective actions to prevent recurrence are to (1) implement controls for silicon-bronze bolt procurement and (2) to implement controls for silicon-bronze bolt installation torque.

Enclosed is the Task Force Memo (TS 85-1302 dated December 17, 1985) which represents the culmination of the Task Force effort. This memo is being provided in accordance with Sepcial Report 85-06, Item 2.

I e h re any questions regarding this issue, please contact Mr. Ron W.

dolo b i (916) 452-3211 at the Rancho Seco Nuclear Generating Station.

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R. J. IRI ASSISTAhT GEN MANAGFA NUCLEAR Attachments cc: Director, NRR 8605060522 860430 /

PDR S

ADOCK 05000312 PDR h Ig 1l now

a SACRAMENTO MUNICIPAL UTILITY DISTRICT

0FFICE MEMORANDUM TO

G. A. Coward DATE: December 17, 1985 TS 85-1302 C.Linkhart,J.Sullivan%

FROM'.

R h . White and R. Wichert suaJ2cT: SILICON BRONZE BOLTS FAILURES The analysis of the Failure of Silicon Bronze Bolts in the 3A bus is complete. Attached for your information are memoranda from C. Linkhart, J. Sullivan, R. White, and R. Wichert which form the basis for the recommendations below. The root cause of the Failures is apparently the use of Silicon Bronze Bolts which were torqued over their IGSCC stress limit. Additionally it should be'noted that the grain orientation of the failed bolts may have made their IGSCC stress limit lower than it would have been otherwise. The following recommendations are made in an effort to avoid similar failures:

1. Torquing of all hex-head bolts or capscrews over 1/4". diameter thread size used in electrical power distribution equipment shall be specified and shall be determined using calibrated torque wrenches during installation. This shall be applicable to all Class 1 installations and may be applied elsewhere at the direction of the Cognizant Engineer.

2. The use of these fasteners in Class 1 equipment with no specifi-cation and no inspection and no requirements for vendor qualifi-cation appears to be imprudent. General Requirement 5 of QAP 4, itself appears to be improper if the nature of service and conse-quences of failure are considered. General Requirement 5 of QAP 4 shall be deleted or revised to delete small fasteners.

Fasteners which, upon failure, would compromise the function of Class 1 equipment must, in the future, be at least Commercial Grade.

Attachments cc: Steve Crunk Bob Little John McColligan

,, Dan Muth .

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