ML19319D809
| ML19319D809 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 10/31/1977 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| Shared Package | |
| ML19319D789 | List:
|
| References | |
| NUDOCS 8003250803 | |
| Download: ML19319D809 (2) | |
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SALRAMENTO MUNICIPAL UTILITY DISTRICT C 6201 S Street. Box 15830, Sacramento, Califomia 95313; (916) 452 3211 October 31, 1977
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Director of Regulatory Operations i;
g ATTN:
Mr. R. H. Engelken Q
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NRC Ope. rations Office, J -
1 Region V
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1990 N. California Boulevard
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Walnut Creek Plaza, Suite 202 Ualnut Creek, California 94596 Re: Operating License DPR-54
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Docket No. 50-312 Reportable Occurrence 77-12
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Dear Mr. Engelken:
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In accordance with Technical Specifications for Rancho Seco Nuclear Generating Station, Section 6.9.1 and Regulatory Guide 1.16, Revision 4
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Section C.2.b.2, tha Nm 77-12.)atoMunicipalUtilityDistrictisherebyreporting
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the following as On October 1,1977, during Core II refueling shutdown, an attempt was made to open one of the valves isolating the Borated Water Storage Tank (BWST) from the Decay Heat Pump suction. The operation in progress involved filling ge the primary side of Steam Generator "A".
The valve would not open on signal from the Control Room and an investigation revealed that the motor was operating but the valve stem was not moving.
It was verified that the redundant BWST isolation valve was operable.
The motor operator on i-he nonfunctioning valve (SFV-25003) was disassembled in an attempt to locate the source of the trouble. The clutch assembly on the
=otor drive showed severe wear, including displacement of several small parts such as set screws and nylon inserts.
In this operator a part known as the worm shaf t clutch acts as the locking mechanism for driving the shaf t either by the manual handwheel or by the motor. The dogs on the vom shaf t clutch and the worm shaf t clutch gear were rounded off significantly and it is postulated that this was the cause of the valve not opening. The dogs were suffficiently worn to allow rotation of the worm shaf t clutch gear against the worm shaft clutch without locking
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and the resulting vibration could have caused the set screws to back out, which would have separated the worm shaf t clutch gear from the motor.
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J 8003250
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l R. H. Engelken October 31, 1977 The District has contacted the vendor and an investigation is progressing to determine what the actual cause and resolution of the failure might be.
The
- motor operator is a Limitorque Model SMB-2 (Serial No. 133814). It will be d
repaired to return the valve to operable status. If the results of the investi-
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gation indicate that further corrective action is required to prevent recurrence of this problem, a followup report will be filed.
There was no plant transient or shutdown resulting from this occurrence.
Respectfully submitted, N-J. J. Mattimoe k
n Assistant General Manager and Chief Engineer
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'JJM: RWC: sal Enclosure cs: Director, MIPC (3) l Director, IE (30) h I
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