ML19319B820

RO NP-33-77-70:on 770822,hydraulic Snubbers SR17 & SR11 Found Close to End of Piston Travel.Caused by Oversight in Design.Piston Design Temp Settings Not Changed When Support Position changed.1.5 Inch Shim Added to Support

ML19319B820
Person / Time
Site:	Davis Besse
Issue date:	09/16/1977
From:	David Brown, Lingenfelter J TOLEDO EDISON CO.
To:
Shared Package
ML19319B710	List: ML19319B709 ML19319B820
References
NUDOCS 8001270281
Download: ML19319B820 (3)

Text

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LICENSEE EVENT REPORT

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EvtNT of SCReptioN g

r ;as Hydraulic Snubbers SR17 and SR11 were found very close to the end of theirj g ; piston travel. The snubbers were disconnected to allow for the addition %;

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g L tatement S of Technical Specification 3.'.7.1. (NP-33-77-70)  ;

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? to in 12 17 43 44 as sa Caust DESCRsPf ton l The cause of Hydraulic Snubbers SR17 and SRll reaching their =aximum l

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s TOLEDO EDISh1 COP?ANY DAVIS-BESSE UNIT ONE NL'CL /.a :'CWER STATION SUPPLEMENTAL INFORMATION FOR :.ER NP-33-77-70 4

DATE OF EVENT: August 22, 1977 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRE' ICE: Main Steam Line 1-l' Hydraulic Snubbers SR17 and SRll were rendered inoperable.

o Conditions Prior to Occurrence: The plant was in Mode 2, with Power (MWT) = 0, and Load (MWE) = 0.

J Description of Occurrence: On August 9, 1977, at approxi=ately 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br />, during a review of all hydraulic snubbers to check "as built" conditions, construction

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i management found hydraulic snubber SR17 on the Main Steam Line 1-1 to be at or very nearly at the end of its piston travel. This may have made the hydraulic snubber inoperable.

On August 10, 1977, hydraulic snubber SRll on Main Steam Line 1-1 was also found to

\ be very close to the end of the piston travel. At 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on August 22, 1977, seismic hydraulic snubbers SRll and SR17 were disconnected (to allow for addition of shims) rendering the two hydraulic snubbers inoperable.

The above actions placed the station in the Action Statement of Technical Specifica-tion 3.7.7.1 which requires all nuclear safety related hydraulic snubbers to be operable in Mode 2. i Designation of Aeparent Cause of Occurrence: The apparent cause of hydraulic snub-bers SR11 and SR17 reaching their maximum stroke has been attributed to oversight in design. When a change in the position of the hydraulic snubber support was =ade, design personnel failed to change the piston design hot and cold settings. The supports were changed due to interferences with other items in the area.

I Analvsis of Occurrence: There was no threat to the health and safety of the public or to station personnel. Hydraulic snubbers SRll and SR17 are seismic hydraulic j snubbers which are only required for a seismic event. There was not a seismic event during the time when the hydraulic snubbers were inoperable.

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I TOLEDO EDISON COMPANY DAVIS-BESSE UNIT CNE "UCLEAR PCWER STATION SUPPLEMENTAL INFPRMATION FOR LER NP-33-77-70 PAGE 2 Corrective Action: The pins for hydraulic snubbers SR11 and SR17 were removed and the threaded eyelet of the piston was screwed out approximately 1/4 inch which

allowed the hydraulic snubbers to have an additional 1/4 inch piston travel. This temporary fix would allot- the hydraulic snubbers to be operable in case of a seis-mic event. The pins were removed without euch effort which indicated that the hydraulic snubber and pipe were not in a bind. The pins were re-inserted after the adjustment of the threaded rod ends, and hydraulic snubbers were declared operable at 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on August 10, 1977. ,

I A permanent fix was made to hydrsulic snubbers Sall and SR17 by installing a lh inch shim to the support which changed the hydraulic snubber piston rod to a mid-stroke position. The piston rod eyelet was returned to its original position.

j Repositioning the piston rod to the midstroke position allows for adequate ther=al growth without the hydraulic snubber reaching the end of its travel. The hydraulic snubbers were declared operable at 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br /> on August 23, 1977, removing the station from the Action Statement of Technical Specification 3.7.7.1. All hydrau-

lic snubbers have been checked to ensure there is adequate piston travel. The problem with the hydraulic snubber SR11 was found during the checkout of all hydraulic snubbers.

Failure Data: There hav.: been no previous failures with hydraulic snubbers SRll and SR17. A previous fe'. lure with hydraulic snubber GC3-7-H4 having no hydraulic fluid was reported on Lra NP-33-77-19.

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