ML19317G954
| ML19317G954 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 06/17/1976 |
| From: | Reinaldo Rodriguez SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Crews J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| 76-238, NUDOCS 8004020613 | |
| Download: ML19317G954 (4) | |
Text
FWRCTERu TO u.s. Nucti: AR cscutAT:RY coumSaloN DOCKET NUMSE R s
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50-312 NRC, DISTRIBUTION FOR PART 50 DOCKET MATERI AL TO:
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Mr. J. L. Crews Sacramento, California 6/17/76 Sacramento'Mynicipal' Utility Dist.
o47,,,ce,y g o R. J. Rodriguez 7/7/76 METTER ONOTORIZE D PROP INPUT FORM NUMBER OF COPfES RECEIVED i
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MUNCLASSIFIED one signed OcoPv DESCRIPTION ENCLOSURE Ltr. w/ attached drawing...~re recent teleph6ne conversation between.Mr. Dodds & R. Colombo of SMUD....concerning non-safety relate'd p
problema experienceB with Bergen-Patterson
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SACRAMENTO MUN TY DISTRICT O 6201 S Street, Box 15830, Sacramento, California 95813; (916) 452-3211 V/
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i June 17,1976
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Walnut Creek Plaza, Suite 202
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Walnut Creek, California 94596
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Re:
Rancho Seco Nuclear Generating Station Bergen-Patterson Hydraulic Snubbers
Dear Mr. Crews:
As requested by Mr. Dodds of your office in a recent telephone conversation with R. Colombo of SMUD, we are reporting on some non-safety related problems experienced with Bergen-Patterson Hydraulic Snubbers which may impact other plants having these units install'ed.
During normal surveillance, those snubber units which have low fluid levels are refilled to assure proper functioning. While refilling a Model HSSA-3 Bergen-Patterson Snubber, maintenance personnel discovered that fluid sprayed out of the overfill hole on the occumulator tube prior to injecting all of the fluid calcu-lated as necessary to fill the unit.
A subsequent inspection of the snubber by a SMUD Engineer and a Bergen-Patterson representative revealed that the overfill hole had been drilled 3/8 inch away from the proper location.
The accumulator tube on these units (see attached sketch) serves to accommodate the fluid volume displaced by the snubber piston rod.
The accumulator has a spring-loaded piston which travels in response to these fluid changes. With the snubber piston in the full retracted position, the accumulator piston is at full travel, at which point the overfill hole is supposed to be drilled. Any attempt to overfill the snubber with fluid will cause the accumulator piston to travel beyond the hole and fluid will spray out, maintaining proper fill.
The hole was misdrilled on our unit, causing the piston to pass the
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overfill hole prior to reaching full travel. The resultant loss of
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fluid reduced the margin of excess fluid in the unit and could have, if located far enough off location, resulted in deterioration of functioning capability.
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t J. L. Crews June 17, 1976 An analysis by the vendor determined that for our units (several other units were found to have misdrilled holes) sufficient reserve capacity existed to assure that the units operated within specifications.
Another problem that became evident during this investigation was the plugging of the overfill holes with paint.
Inspection showed that on several of the units the accumulator had been completely painted.
Since the overfill hole is only pinhole-sized, the painting completely plugged it.
This could permit overfilling the snubber if the calcula-tional method for filling recommended by the vendor was not followed.
We hope this information gained from experience with Bergen-Patterson Hydraulic Snubbers, Model HSSA-3, will be of value.
Respect u y,
'u \\ (g R. J.
driguez Manager, Nuclea' perations RJR:RWC: sal Attach.
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