05000312/LER-1981-021, Forwards LER 81-021/03T-0.Detailed Event Analysis Also Submitted

Forwards LER 81-021/03T-0.Detailed Event Analysis Also Submitted

ML20003H968
Person / Time
Site:	Rancho Seco
Issue date:	05/01/1981
From:	Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20003H969	List: 05000312/LER-1981-021, Forwards LER 81-021/03T-0.Detailed Event Analysis Also Submitted 05000312/LER-1981-021-03, /03T-0:on 810402,BWST Valve SFV-25003 Failed to Open Electrically Due to Rounded Off Dogs on Worm Shaft Clutch Gear.Caused by Manual Operation of Valve.Worm Components Replaced.Design Changes Are Being Processed
References
NUDOCS 8105080251
Download: ML20003H968 (2)

LER-1981-021, Forwards LER 81-021/03T-0.Detailed Event Analysis Also Submitted

Event date:
Report date:
3121981021R00 - NRC Website

text

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SMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT C 6201 S Street, Bcx 15830, Sacramente, Cahfernia 95813; (916) 452-3211 v

May 1, 1981 6

O 9

R. H. ENGELKEN, DIRECTOR f. N 5 k(.O(()@

REGION V 0FFICE OF INSPECTION r. ENFORCEMENT [j

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U. 5. NUCLEAR REGULATORY COMMISSION 1990 NORTH CALIFORNIA BOULEVARD (9

M Y 0 71981 5,

WALNUT CREEK PLAZA, SUITE 202 WALNUT CREEK CA 9L596

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, [vd OPERATING LICENSE DPR-54

,o La DOCKET NO. 50-312 REPORTABLE OCCURRENCE 81-21 in accordance with Technical Specifications for Rancho Seco Nuclear Generating Station, Section 6.9.4.2.5, and Regulatory Guide 1.16, Revision s

4, Section C.2.b.2, the Sacramento Manicipal Utility District is hereby submitting a thirty-day report of Reportable Occurrence 81-21.

On April 2, 1981, in preparation for performing SP 203.05, Quarterly DHR Pump P-261A Surveillance and inservice Test, the BWST valve, SFV-25003, failed to open electrically. An investigation revealed that the motor was operating but the valve stem was not moving.

Disassembly of the valve operator revealed that the degs on the worm shaft clutch gear were rounded of f.

The worm shaf t clutch gear is part of the locking mecha-nism, which when engaged wi th the worm shaf t clutch, drives the shaf t via the motor.

The rounded dogs on the worm shaf t clutch gear allowed rotation of the worm shaft clutch gear against the worm shaft clutch without locking or engaging.

Similar occurrences in late 1977 and early 1980, reported to your office via LERs 77-12 and 80-17, resulted in the District contacting the vendor, Limitorque Corporation, concerning premature failure of these actuator components.

It was determined at that time that manual operation of the valves significantly increases the wear on the dogs. This failure mode of the locking mechanism will occur subsequent to a manual operation.

As a result, the District imposed a requirement to cycle the valve via the motor following manual operation of any safety features valve with a similar operator.

The valve, SFV-25003, had beer, manually operat ed to fill and vent the "B" 04R System just orior to the occurrence.

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Engelken May 1, 1981 As reported in LER 60-17, the vendor : hanged the caterial and heat treating process f'r the worm shaft clutch and clutch gear in the o

later part of 1978.

In 1980, the replacement components for this valve were thought to be of the new material and heat treating process.

However, as a result of this most recent occurrence it appears that only the worm shaft clutch and not the worm shaf t clutch gear was replaced with the ned mate ri al.

Both the worm shaf t clutch and worm shaf t clutch gear were replaced after this latest occurrence. The replacement components are of the original material. No components of the newer material were in stock.

Since premature failure is experienced es a direct result of manual operation, the original material components should prove satisfactory if manual operation is not performed. To delete the necessity for manual operation, design changes are being processed to modi fy the electrical circuitry to allcw " Jog capability" to the valve.

Since replacement of the components, partial opening of the valve (for i

filling and venting purposes) has been performed electrically via temporary jumpers and abnormal tags.

If necessary prior to completion of the design changes, temporary jumpers and abnormal tags can again be utilized to preclude any manual operation of the valve.

Eliminating.

manual operation entirely should prevent future similar occurrences.

The valve operator is a Limitorque Model SMB-2 (Serial No. 133814) j manufactured by Limitorque Corporation.

There were no plant transients nor power reductions associated with this event.

1 1

John J. Mattimoe Assistant General Manager and Chief Engineer cc:

l&E Washington (30)

MIPC (3)

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