ML20084S051

AO 50-249/74-23 & 24:on 740726,during Insp Prior to Local Leak Rate Testing,Rubber Coated Valve Seat for AO-3-1601-21 & 22 Found Cracked.Caused by Liquid Nitrogen Reaching Both Valves.Valve AO-3-1601-21 Replaced & 22 Blank Flanged

ML20084S051
Person / Time
Site:	Dresden
Issue date:	08/01/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J Office of Nuclear Reactor Regulation
Shared Package
ML20084S054	List: ML20084S051 ML20084S076 ML20084S078
References
551-74, AO-50-249-74-23, AO-50-249-74-24, NUDOCS 8306160126
Download: ML20084S051 (2)

Text

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C:mm:m( Ith Edia:n Ons First Nati<y a! Ptara. Chicago. Illinois Address Rep y to: Post O!hce Box 767

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Chicago, tilinois 60590 BBS Ltr.9551-74 Dresden Nuclear Power Station

, R. R. #1 Morris, Illinois 60450

. August 1,1974 Mr. J. F. O' Leary, Director

• Directorate of Licensing -

U. S. Atomic Energy Co:anission Washington, D. C. 20545 SUBJECI: REFO*tT OF .1LENORFAL_ OCCURRENCE PER SECTION 6.6.B.l.a OF THE TECHNICAL SPECI?ICATIO:3.

EXCESSW2 LDKI.GE T'4RCUGH A0-3-1601-21 & 22.

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A j l

2) Notification of Region III of AEC Regulatory Operations l Telephone: Mr. F. Maura,1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br /> on July 28, 1974 and 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br /> on July 29, 1974.

Telegram: Mr. J. Keppler,1613 hours0.0187 days <br />0.448 hours <br />0.00267 weeks <br />6.137465e-4 months <br /> on July 26, 1974 l and 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br /> on July 29, 1974.

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Report liu=ber: 50-249/1974-23 & 24 rp. ,-

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Facility: Dresden Nuclear Power Station, Morris. Illinois x. l IDENTIFICATION 07 OCCUnRENCE Failure of primary containment due to leakage through A0-3-1601-21 t

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CONDITIONS PRIOh TO OCCURRENCE Prior to the occurrence, the unit was in the run mode and operating at an electrical 1 cad of about 380 magavatts. Thermal power at the tice of discovery was about 1300 megawatts. Local leak rate testing of the rubber seated vent valves was in progress.

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Mr. J. F. O' Leary ** lh August 1, 1974 DESCRIPTION OF OCCURRENCE During an inspection prior to conducting local leak rate testing of ,

the boundary forced by A0 valves 3-1601-21, 22, 55, and 56, the rubber coated '

valve seat for A0-3-1601-22 was found to be cracked. On further investigation, it wcs found that the A0-3-1601-21 valve also had a cracked rubber coated scat.

{Leakagethroughboththe 3-1601-22 and 21 valves were excessive,

_DESIG!nTION OF APPAREh*r CAUSE OF OCCURRENCE It is believed that the cause of the occurrence was due to liquid nitrogen reaching both valves. At the tile of the occurrence, the heating boiler for the c.ystem was chutdown. With heating steam unavailable, it ic possibic for liquid nitrogen to reach the boundary of the 3-1601-21, 22, 55, and 56 valves.

Al% LYSIS OF OCCUEFENCE During the occurrence the safety of the plant and public was not placed in jeopardy. Although primary centainment integrity had been lost, secondary containaent was ccmpletely functional and the str.edby gas cystem was operaticnal at the time of the occurrence. The line vac blank flanged to restore primary contniu=ent integrity itmediately following the discovery.

,C_C*tRECTIVE ACTION The innediate corrective action was to initiate an orderly plcnt shutdown. Follcwing shutdown, the 3-1001-21 valve was replaced and the 3-1601-22 velve was blank flangcd. Follcwins repairs, the piping section was leak tected and found to be within lbsits. To prevent this type of an occurrence in the future, the nitrogen system is being studied to determino

, a ceans of p:cventing liquid nitrogen from reaching the valves during a less of heating secca. In view of cumulative experience, the corrective action taken was satisfactory.

FAILURE DATA During the period of the occurrence on Unit 3, a similar failure occurred on Dresden Unit 2. During this occurrence, the 2-1601-21 and 22 valves were also daraged. Again it is believed that liquid nitregen recchad the valves on the unit startup which took place on June 14, 1974.

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