ML20009G633

LER 81-012/03L-0:on 810624,discovered safety-related Hydraulic Snubber on Atmospheric Dump Line B Was Broken at Rod Eye.Caused by Vibration.Snubber Repaired

ML20009G633
Person / Time
Site:	Oconee
Issue date:	07/24/1981
From:	Jackie Jones DUKE POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009G620	List: ML20009G619 ML20009G633
References
LER-81-012-03L-02, LER-81-12-3L-2, NUDOCS 8108040493
Download: ML20009G633 (2)

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,3;., iredundant train of the Main Steam atmospheric dump line was operable during ,

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t i t i s l and returned to service. Vibration tests were run. The snubber has been ,

( g ,g ipulled for functional testing as part of the 107. test requirement. ,

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DUKE POWER COMPANY OCONEE UNIT 1 Report Number: R0-269/81-12 Report Date: July 24, 1981 Occurrence Date: June 24, 1981 Facility: Oconee Unit 1, Seneca, South Carolina Identification of Occurrence: Hydraulic Snubber Inoperable Conditions Prior to occurrence: 90% FP Description of Occurrence: At approximately 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> on June 24, 1981, a safety-related hydraulic snubber on the Unit 1 "B" Main Steam atmospheric dump line was discovered to be broken at the rod eye, thus causing the snubber to be inoperable. This constitutes operation in a degraded mode per Technical Specification 3.14.2 and is thus reportable pursuant to Technical Specification 6.6.2.1.b(2).

Apparent Cause Of Occurrence: Apparently the pipe clamp vibrated below the parallel axis to the snubber resulting in an angle of less than 180 . The vibration of the pipe and the angle of the pipe clamo and rod eye to the snubber caused the threaded end of the rod eye to snap.

Analysis of Occurrence: The probability of occurrence of an earthquake is very low. Also the inoperability of the snubber only degraded one Main Steam atmospheric dump line. The redundant train of the Main Steam atmospheric dump line was operable during this event. All other snubbers and hangers on this line were operable. Hence, the Healch and Safety of the public was not affected during operaion or shutdown.

_ Corrective Action: The snubber was repaired and returned to service.

Nibration tests were run to determine the frequency and velocity of the vibration and the stress the snubbers / hangers are seeing. The snubber has been pulled for functional testing as part of the 10% tea

• requirement;.

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