ML20052G526

Forwards LER 82-008/03L-0.Detailed Event Analysis Submitted

ML20052G526
Person / Time
Site:	Cooper
Issue date:	05/06/1982
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Coolins J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20052G527	List: ML20052G526 ML20052G532
References
CNSS820238, NUDOCS 8205180437
Download: ML20052G526 (2)

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bN COOPER NUCLEAR STATION hahjJpras(a P@ic Power District _

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CNSS820238 May 6, 1982 Mr. John T. Collins, Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.2 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on April 15, 1982. A licensee event report form is also enclosed.

Report No.: 50-298-82-08 R]iE@

! "q TOW /0P Report Date: May 6, 1982 s occurrence Date: April 15, 1982 1 l pg(l2 g Facility: Cooper Nuclear Station 1; Brownville, Nebraska 68321 U- - #

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Identification of Occurrence:

A condition which may have resulted in operation in a degraded mode permitted by a limiting condition for operation established in Section 3.6.11.1 of the Technical Specifications.

Conditions Prior to Occurrence:

A snubber was installed in the drywell on 11-10-76 and was removed f rom the drywell on 6-2-81 during the refueling outage. It was being tested for certification by Wyle Laboratory to allow its reuse in the plant.

Description of Occurrence:

During diagnostic testing by Wyle Laboratory of several Eccific Scientific snubbers, a Model PSA-10 (Part No. 1801103-07), S/N 544, snubber exceeded the acceleration rate of 0.02g for the compression stroke.

Designation of Apparent Cause of Occurrence:

The apparent cause of this occurrence has been attributed to tne improper installation of the clutch spring in the snubber or by the installation of a defective clutch spring in the snubber by the Pacific Scientific Company during the manufacture of the snubber.

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Mr. John T. Collins j - May 6,L1982 Page 2.

i Analysis of Occurrence:

4 Snubber, S/N 544, was installed in the drywell on a main steam l

relief line in location VR-61-8-Z on 11-10-76 to replace a hydraulic 4 snubber. Snubber, S/N 544, was removed from the drywell on 6-2-81.

During diagnostic testing by Wyle Laboratory to recertify the unit, this snubber exceeded the acceleration rate of 0.02g for the compres-

.sion stroke and thus does not meet the design specification for-mechanical snubbers. Upon disassembly of the snubber, the clutch spring was found raised approximately 1/4 inch out of position in the inertia mass. This mis-positioned clutch spring would not allow the lower tang of the capstan spring to contact the clutch spring. During the compression stroke of the snubber, the capstan spring would not torque down around the mandrel and resist the

compression stroke of the unit. No activation or restraining j- action would occur during the compression stroke.

1 j The clutch spring in this snubber may have been incompletely instal-

• 1ed into place in the inertia mass during manufacture. It was also i noted, however, that the clutch spring did not have as great an i outward tension as a clutch spring from another snubber. Because 4

of this reduced outward spring tension, the clutch spring was not 1 fixed tightly in the inertia mass. Thus, from movement of the snubber and from vibration in the piping, the clutch spring may have slipped out of the inertia mass and resulted in the failure found during the certification testing.

t

! This mechanical snubber which was installed in drywell location VR-i 61-8-Z is designed to accommodate the thermal growth of the relief line during normal operation and to provide a restraint to pipe movement during transient and seismic events. This snubber did not provide a pipe support function during normal operation. There was 1 no record of seismic events during the time this snubber was installed.

This event is not repetitive and presents no adverse consequences ,

to public health and safety.

Corrective Action:

Snubber, S/N 544, has been. returned to Pacific Scientific Company for repair and certification. Seismic structure VR-61-8-Z was

, redesigned and a larger model mechanical snubber was installed as

part of-the

Mark I Containment Program during the 1981 Refueling Outage.

j Sincerely, i

L. C. Lessor

, Station Superintendent

!- Cooper Nuclear Station LCL:cg

. Attach.

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