05000272/LER-1979-054, Forwards LER 79-054/01X-2

Forwards LER 79-054/01X-2

ML18085A926
Person / Time
Site:	Salem
Issue date:	02/19/1981
From:	Uderitz R Public Service Enterprise Group
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML18085A927	List: 05000272/LER-1979-054, Forwards LER 79-054/01X-2 05000272/LER-1979-054-01, /01X-2:on 790824,three Snubbers on Main Feedwater Line 14 Found Unable to Rotate Around Spherical Rod End Bearings.Lead Screw & Traveling Nut Assembly Failed Due to Excessive Force.Cause Undetermined
References
NUDOCS 8102270677
Download: ML18085A926 (3)

LER-1979-054, Forwards LER 79-054/01X-2

Event date:
Report date:
2721979054R00 - NRC Website

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~r. Boyce H. Grier Director of USNRC February 19, 1981 Of£ice of Inspection and Enforcement Region 1 631 Park Avenue King of Prussia, Pennsylvania 19406

Dear Mr. Grier:

LICENSE NO. DPR-70 DOCKET NO. 50-272 REPORTABLE OCCURRENCE 79-54/0lX-2 SUPPLEMENTAL REPORT Pursuant to the requirements of Salem Generating Station Unit No. 1 Technical Specifications, Section 6.9.1, we are submitting supple-mental Licensee Event Report for Reportable Occurrence 79-54/0lX-2.

Sincerely yours,

~~~~~

R. A. Uderit-e;--*

General Manager -

Nuclear Production CC:

Director, Office of Inspection and Enforcement (30 copies)

Director, Office_ of Management Information and Program Control (3 copies)

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Report Number:

79-54/0lX-2 Report Date:

February 19, 1981 Occurrence Date:

8/24/79 Facility:

Salem Generating Station, Unit 1 Public Service Electric and Gas Company Hancocks Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE:

No. 14 Stearn Generator Feedwater Line Snubber Failures CONDITIONS PRIOR TO OCCURRENCE:

Mode 5 -

Cold Shutdown DESCRIPTION OF OCCURRENCE:

While performing a safety wire inspection of No. 1 unit pipe snubbers as a followup to NRC Inspection 50-311/79-19, three (3) snubbers on No. 14 Main Feedwater line were found unable to rotate around their spherical rod end bearings.

The snubbers were removed and inspection revealed that the lead screw and traveling nut assembly that trans-lates linear to rotational motion had failed.

The snubbers no longer provided seismic shock restraint under this condition.

These snubbers are directly upstream of the nuclear Class II piping boundary and are included in the stress calculations for the seismic analysis of the nuclear portion of the main feedwater piping.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

PSE&G discussed the damaged snubbers with a representative of the snubber manufacturer to determine the cause of the failure.

Failure of the snubbers appears to be the result of a force applied to the snubbers many times greater than their design load.

The force was either an extreme shock load or occurred when the snubber was in the fully retracted condition.

The exact cause and magnitude of the force has not been determined.

ANALYSIS OF OCCURRENCE:

These snubbers were included in 'the thermal stress calculations for the seismic safety analysis of the nuclear portion of the main feed-wat~r piping.

Stress calculations indicated that the increase in stress in the piping is small and remains well below the allowable stress limit.

Seismic stresses would not be affected as the snubbers would be locked under that condition.

LER 79-54/0lX-2 2 -

February 19, 1981

CORRECTIVE ACTION

The failed snubbers were replaced in kind.

Snubbers on No. 11, 12 and 13 Main Feedwater lines were inspected and found satisfactory.

Visual examination of the weld joints of this section of the piping revealed no defects.

PSE&G arranged* for the PSE&G Research Corporation to install instrumentation to measure and record the acceleration and linear displacement of the piping at the snubber locations.

The snubbers were instrumented with displacement transducers and accelerometers with the data monitored for several weeks.

During the testing, the unit was operating under normal conditions which included several startups and trips.

The data showed that there was no excessive vibration or displacement during a trip.

When the graphs did show activity, station personnel indicated that no testing or load changes were in progress, which would produce the vibration.

During the test period, the station experienced problems with valve 14BF19 and inspected it.

The valve had considerable vertical vibration which may have increased the snubber vibration.

The snubbers vibration frequency was approximately four cycles/second.

These tests were conducted during the period December 29, 1979 through January 24, 1980.

FAILURE DATA:

Pacific Scientific Company Model PSA-3 Prepared By W. J. Steele SORC Meeting No.

81-05