ML20084R630

RO 50-249/75-07:on 750216,drywell Snubber Insp Revealed That One Bergen-Patterson Snubber on HPCI Steam Supply Line Lost All Hyraulic Fluid.Caused by Missing O-rings & Leaking Zirc Fitting.Fittings Will Be Checked for Leakage

ML20084R630
Person / Time
Site:	Dresden
Issue date:	03/03/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084R621	List: ML20084R619 ML20084R623 ML20084R626 ML20084R630
References
127-75, RO-50-249-75-07, RO-50-249-75-7, NUDOCS 8306150255
Download: ML20084R630 (2)

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Accress Reply to: Pom Off ce Box 767 e

W Chicago, til:ncis 60690 BBS Ltr. #127-75 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 March 3, 1975 Mr. Jcmes G. Keppler, Regional Director Directorate of Regulatory Operations-Region III U. S. Nuclear Regulatory Cor:::nission 799 Roosevelt Road Glen Ellyn, Illinoi's 60137

SUBJECT:

REPORT OF UNUSUAL EVDTP PER SETION 6.6.C OF THE TECM!ICAL SPECIFICATIONS FAILURE OF IHDRAULIC PIPE SUI'PP2SSOR Ecference 1.

Regulatory Guide 1.16 Rev. 2 Appendix A 2.

Kotification of Region III of U. S. Nuclear Re6ulatory Counission Telephone: Fr. P. Johnson,1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> on February 18, 1975 Telegram: Mr. J. Keppler, 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> on February 18, 9 75 Report Nu:nber: 50-249/75-7 hcport Date: March 3, 1975 pQ l

w Occurrence Date: February 16, 1975 d

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s; IDDTPIFICATION OF OCCURRENCE Pailure of a unit 3 drywell hydraulic pipe suppressor, q

SY CONDITION PRICR TO OCCURRE!CE

. Dresden Station' Unit 3 came off line on February 14, 1975 and went to the cold shutdown condition in order to check the core spray system per IE Eulletin 75-01.

Since the unit was to be shutdown for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and the previous inspection occured nore than 30 days prior to February 14, 1975, a pipe suppressor inspection was perforned.

DESCRIPTION OF OCCURRECE

During the week end of February 14, 1975 a drywell snubber inspection was perforced on Unit 3 The inspection revealed that one Bergen-Patterson snubber on the HFCI steem supply line had lost all its hydraulic fluid.

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Mr. Jam;g O. Ksppler March 3, 1975 o'

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v DESIGNATION OF APPARE!? CAUSE OF OCCURRD'CE (Equip::ent Failure)

On disassembly of the failed snubber the following discrepancies were found.

1) Two "0" rings were missing from the check valve assembly and its associated tubing.

2) The zire fitting used to add hyraulic fluid to the snubber was found to leak through.

It is believed that the missing "C" rings were not installed during the snubbers last overhaul which was in April of 1974. The failure of the zirc' fitting is believed *,o be the primary cause of the loss of hydraulic fluid. The location of the snubber whc.1 instal--

led in the drywell would place the zire fitting at the bottom of the accuzm.tlator.

In this position all the hydraulic fluid would drain from the accumulator.

ANALYSIS OF OCCURRD!CE The failure of the hydraulic cnubber did not place the safety of the plant or public in jeopardy. The failure of one hydraulic enubber on a particular line does neccsearily adversely affect the ability of a system to function following a siesmic event. In cddition, all other safety systems were operational during the failure of the hydraulic anubber.

_ CORRECTIVE ACTICN In regards to the missing "0" rings it was discovered that the present repair and over-haul procedure did not list them on the check off sheet. A new procedure has been written and vill become effective by March 15, 1975. Concerning the failure of the zire fitting, the fittings will be checked for leaksge following any addition of hydraulic fluid.

I'AILURE DATA The Bergen-Patterson hydraulic anubbers have had a history of failures associated with their uso in the drywell area.

Sincerely, h / i s. % %

B/B.

tephenson Superintendent BBS TEL:smp File /AEC D

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