ML20084N905

AO 50-249/75-32:on 750721,clamp Bolt Keeper Tack Welds on Jet Pumps 6 & 17 Failed.Caused by Poor Tack Welding.Clamp Bolt Keepers Rewelded & Successfully Retested

ML20084N905
Person / Time
Site:	Dresden
Issue date:	07/31/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084N908	List: ML20084N905 ML20084N911
References
461-75, NUDOCS 8306090108
Download: ML20084N905 (2)

Text

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. Comm ealth Edison '

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Addr;ss ly to: Post Offics Box 767

• (,, Chicago, Ilknois 60690 EBS Ltr. #461-75 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 July 31, 1975 .

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l  % Q? :, i-Mr. Ja=es G. Keppler, Regional. Director d[U Ehj.[l'Yf (I Directorate of Regulatory Operation-Region III z 9

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U. S. Nuclear Regulatory Corrission $k _

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799 Roosevelt Road h,s 4,y yf Glen Ellyn, Illinois 60137 jp ,,

SUBJECT:

REPOR? 0F AENORVAL OCCURRENCE PER SECTION 6.6.A OF THE TECHNICAL _ . . l.

SPECIFICATICNS FAILUBE CF RESTRAI?ER CIJa'P EOLT *'EEPER ON JET P'&'PS

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A

2) Notification of Region III of U. S. Nuclear Regulatory Conmission Telephone: Mr. P. Johnson, 0S20 hours on July 22, 1975 Telegram: Mr. J. Keppler, 1120 hours0.013 days <br />0.311 hours <br />0.00185 weeks <br />4.2616e-4 months <br /> on July 22, 1975

3) Drawing Number GE Drw #729E434 Report Number: 50-249/75-32 Report Date: July 31, 1975 Occurrence Date: July 2-1, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois IDENTIFICATION OF OCCURR9?CE The clamp bolt keeper tack welds on jet pumps #6 and #17 failed.

CONDITIONS PRIOR TO OCCURRE'!CE l

Unit-3 was shut down for refueling.

bO' DESCRIPTION OF OCCURREN'CE

/ .do At approximately 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on July 21, 1975, d'uring restrainer keeper 1 testing of the Unit-3 Jet pumps it was noted that ceieral tack welds had " parted on th2 outboard clamp bolt keepers for #6 and #17 jet pu=ps. A visual examination by underwater television had revealed no visible defects on either jet pump keeper; however, during the lift test, which ascertains the resilience of keeper and weld, the welds bioke.

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'Mr., James G. K;pplj U July 31, 1975 DESIGNATION OF APPARENT CAUSE OF OCCUitRENCE (Improper Installation)

The apparent cause of both keeper failures is poor tack welding. Properly made, the welds would normally hold the keeper. securely to the jet pump restrainer. .

ANALYSIS OF OCCURRENCE Failure of both inboard and outboard clamp bolt keepers could conceivably allow the clamp bolts to back out of the jet pu=p triedge and restrainer assembly. A double failure of this nature occurring during reactor operation would result in increased vibration of the jet pp and might ultimately lead to separation of the jet pump body at the slip fitting between the mixer and diffuser sections.

The tack weld failures were induced by the artificial vibration of the lift testing. The jet pumps were securely fastened by means of the inboard clamp bolts, both of which were tested satisfactorily. In any event, the routine '

daily surveillance of jet pump flow characteristics would detect any such discrepancy and the reactor,would be shut down within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

The loss of a jet pump during operation has been analyzed as an acceptable condition by the Quad Cities station; their evaluation is applicable to Dresden. Plant personnel and the public were not endangered by this occurrence.

C CORRECTIVE ACTION Clamp bolt keepers for jet pumps #6 and #17 were rewelded and successfully retested. These jet pumps will be inspected during the next major refueling cutage to verify the integrity of the tack welds.

FAILURE DATA There have been no previously reported failures of this nature at Dresden.

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