05000312/LER-1980-014, Forwards LER 80-014/03L-0

Forwards LER 80-014/03L-0

ML20126B690
Person / Time
Site:	Rancho Seco
Issue date:	03/11/1980
From:	Walbridge W SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML20126B692	List: 05000312/LER-1980-014, Forwards LER 80-014/03L-0
References
NUDOCS 8003180566
Download: ML20126B690 (2)

LER-2080-014, Forwards LER 80-014/03L-0

Event date:
Report date:
3122080014R00 - NRC Website

text

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z- , O ~.: M D StCRAMENTO f/UNICIPAL UTILITY DISTRICT C E201 5 Street. Box 1230. Sacrarnento, Caritarrn 9213. (91E) 452 321T  ;

i March 11, 1980  ;

i

. l Mr. R. H. Engelken, Di' rector  ;

l Region V office of Inspection and Enforcccent l U. S. Nuclear Regulatory Commission l 1990 North California Boulevard Walnut Creek Plaza, Suite 202 Walnut Creek, California 94596 l Re: Operating License DPR-54 Docket No. 50-312 Reportabic occurrence 80-14

)

Dear !fr. Engelken:

l In accordanc'c with Technical Specifications for Rancho Seco Nuclear Generat ng Station, Section 6.9.4.2c and Regulatory Guide 1.16, Revision 4, ,

1 Sectiot C.2.b(3), the Sacramento Municipal Utility District is hereby submitting a thirty-day report of Reportable Occurrence 60-14.

The third refueling shutdown for Rancho Seco began January 14, 1980.

In accordance with Technical Specifications Section 4.2, an inservice examina-tion of the reactor vessel was perforned. The District contracted the NSSS vendor, Babcock and Wilcox, to perform the inspection. The inspection consisted ,

of an ultrasonic and visual inspection of the reactor vessel utilizing 35h"s' ARIS (Automated Reactor Inspection System) equipment. The ARIS equipment utilizes a large 3,000 pound block for calibrating the inspection head. During the inspection, this calibration block rests on the vessel flange on special .

guide studs.

On February 19, following the inspection and renoval of the ARIS equipnent, the calibration block vas being lif ted, via the small hook ofDuring the polar cranc, for decontamination and removal f ron the transfer canal.

this evolution,'while louering the block, the crane shifted without operator action f ren sicu speed to f ast speed. The crane operator immediately hit the coergency stop, preventing further louering of the block. The operator then continued louering the block into the canal (for rinsing) and then raised the block approxicately 10 feet above the canal. Shortly thercafter, the wire rope sling cou'pling the block to the small hook separated and the block dropped.

The block dropped into the Fuel Transfer Canal and came to rest on the reactor seal plate. In hitting the seal plate, the block sheared off one of the shield plate studs and nut./ This resulted in a 7 to 8 gpm leak which operations personnel stopped by lowering the water 1cvel to below the vessel flange. Once the fransfer canal was dry, a heavier duty cable was hooked to the calibration block and the block was moved to the cast end of the transfer canal.

1 i

800318DSTo6 AN ELECTRIC 5,Y S T. E M S E RVIN G ,M O R E T H A, N ', 6 '0,0 , 0 0 0 IN T il t ilEART Of C All f 0 R N I A

Mr. R. H. Engelken Page 2 March 11, 1980 In investigating the wire rope sling, it was determined that the eye of the sling, attached to the block, separated approximately midway in the eye.

The cause of the failure is theorized to be strands of the sling breaking on the emergency stop and the rest of the strands failing due to increased load shortly thereafter.

As a result *.of this occurrence, specific actions were taken. These included:

1. Restricting use of the polar crane until the slow-fast speed problem was  !

resolved. A factory representative f rom the crane manufacturer arrived at the site and the problem was resolved. Continued use of the polar crane was authorized February 25.

2. Babcock and Wilcox has been requested to investigate the incident. The failed sling has been sent to them to determine whether the cabic was of the appropriate size for its use and to examine the failure area to determine I why the sling failed.

3. Specific individuals were assigned as flagmen for crane operators to direct all crane movements in the reactor building. These individuals were required '

to attend a training session covering:

a) District-approved rigging practices in accordance with the Administrative

-Procedure AP.5, Rancho Seco Safety llanual.

b) Restrictions placed on polar crane operation in accordance with the Maintenance Procedure !!.31, Operation of the R.B. Polar Crane and FTC Auxiliary Holst, and T;chnical Specifications 3.11. *' l The combination of Babcock & Wilcox's analysis of the sling failure and training specific individuals to determire the rigging and path of the load should prevent recurrence of a similar incident.

l Since the plant was shut down for refueling, there were no power reductions nor plant transients associated with this event.

\

Respectfullysubmittepi Wm. C. Walbridge General Manager l

WCW:HH: jim '

cs: Director, MIPC (3) ,

Director, I6E (30) ,

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