05000289/LER-1981-002-03, /03L-0:on 810130,three Snubbers Failed to Lock Up as Required by Tech Spec.Caused by Worn Piston Ring Seals & Springs W/Excessive Spring Constants.Snubber Seals,Pistons, Valve Blocks & Weight Springs Replaced

/03L-0:on 810130,three Snubbers Failed to Lock Up as Required by Tech Spec.Caused by Worn Piston Ring Seals & Springs W/Excessive Spring Constants.Snubber Seals,Pistons, Valve Blocks & Weight Springs Replaced

ML20003C616
Person / Time
Site:	Crane
Issue date:	03/02/1981
From:	Mitchell D METROPOLITAN EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20003C613	List: 05000289/LER-1981-002, Forwards LER 81-002/03L-0 05000289/LER-1981-002-03, /03L-0:on 810130,three Snubbers Failed to Lock Up as Required by Tech Spec.Caused by Worn Piston Ring Seals & Springs W/Excessive Spring Constants.Snubber Seals,Pistons, Valve Blocks & Weight Springs Replaced
References
LER-81-002-03L, LER-81-2-3L, NUDOCS 8103060591
Download: ML20003C616 (3)

LER-1981-002, /03L-0:on 810130,three Snubbers Failed to Lock Up as Required by Tech Spec.Caused by Worn Piston Ring Seals & Springs W/Excessive Spring Constants.Snubber Seals,Pistons, Valve Blocks & Weight Springs Replaced

Event date:
Report date:
2891981002R03 - NRC Website

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Attachmtnt 1 L1L 061

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EVENT DESCRIPT1oN ANo mMo0 ASLE CONSEQUENCE during the refueling interval surveillance y

l While in the cold shutdown condit I o 12 l This g, testing of snubbers, it was determined that 3 failed to lockup as requred.

I o i 4 I I was a violation of Specification' 4.17.4 and is reportable per 6.9.2.B(2).

There l l c i s i I have been neither seismic events or severe transients to affect the piping nor l

I o i61 ! have sientficant occurrences taken olace as a result of the failed snubbers.

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NARRATIVE

REPOR-Llt 061 TMI-1 LER 81-02/3L-0 l

I.

Current Activities at the Time of Occurrence Functional Testing of hydraulic snubbers in accordance with Surveillance Procedure 1303-9.9 in progress.

Snubb.:- RC-19 failed on January 30, 1981, due to a f ailure to lockup in both tension and compression direction.

Snubber DH-32 failed on February 6,1981, due to a f ailure to lockup in both tension and compression direction. Snubber RC-22 failed on February 20 4

1981, due to a failure to lockup in both tension and compression direction.

II.

Leading Circumstances While performing testing of hydraulic snubbers in accordance with SP1303-9.9, RC-19, DH-32 and RC-22 f ailed to lockup as required.

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III. Description

The Unit.has been in extended cold shutdown conditions since April, 1979.

The snubbers failed during refueling interval functional testing which was being performed to satisfy Technical Specification 4.17.4 require-ments. Since the failed snubbers were not functional tested rabsequent to the March,1979 heatup, the exact time of the failure is unknown.

Therefore, this item is considered reportable under Technical Spec-ification 6.9.2.B.(2).

IV.

Resultant Events Since there has been no earthquake or severe transient which would have caused unrestrained pipe motion under dynamic loading during the March, 1979 heatup or subsequent to then, there are no significant occurrences which l

have taken place as a result of these snubber f ailures.

j V.

Previous Events of a Similar Nature During 1979, snubber RC-19 also f ailed to lockup af ter it was visually discovered to have a broken sight glass. Snubber NSE-151 f ailed to lockup i

4 in July, 1980. LER 80-14/3L was submitted describing that occurrence.

VI.

Root Cause RC-19 failure is attributed to worn piston rirgs seals in the snubber cylinder. DH-32 f ailure is attributed to springs in the snubber valve r

block having too high a spring constant to allow lockup of the snubber.

RC-22 failure is attributed to worn piston *ings seals within the snubber cylinder.

VII.

Imnediate Corrective Action RC-19 snubber was rebuilt using spare replacement parts and new seals.

The springs in valve block were also replaced with lighter weight springs to obtain activation velocities within the specified range for compression and tension lockup.

Springs in DH-32 valve block were replaced with lighter a

weight springs.

s Narrative Report LER 81-02/3L Page 2 i

VII.

I= mediate Corrective Action Cc.t'd RC-22 was completely overhauled with new piston 'O'-ring seals, new valve i

block and lighter valve block springs.

All three snubbers were retested satisfactorily and reinstalled in the plant. Additional snubbers will be tested to comply with Technical Specification 4.17.4 requirements.

VIII. Lone Ter= Corrective Action j

Since all three snubbers were of the sane manuf acturer, all saf ety-related snubbers of that manuf acturer are scheduled for removal and functional testing to assure their operability for plant startup.

IX.

Co=conent Failure Data Basic Engineers - BE 411 Hydraulic Shock and Sway Suppressor - 1h" x 5" stroke.

Mark No. RC-19 Basic Engineers - BE 411 Hydraulic Shock and Sway Suppressor - 3/4" x 5" stroke.

Mark No. DH-32 Basic Engineers - BE-410 Hydraulic Shock and Sway Suppressor - 3/4" x 5" stroke.

Mark No. RC-22 I