ML20084R951

AO 50-249/74-28:on 740920,leakage Noted in Feedwater Line Pressure Tap 3-3241-12A.Caused by Crack in Weld.Pressure Tap No Longer Used

ML20084R951
Person / Time
Site:	Dresden
Issue date:	09/26/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084R954	List: ML20084R951 ML20084R956 ML20084R959
References
689-74, AO-50-249-74-28, NUDOCS 8306160084
Download: ML20084R951 (3)

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3 ono rust r jat Fina, crucap. mino,s Address hvy to: Post Othce Box 707 O

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Morris, niinois 60450g\fM'fA September 26, 1974 y CA i!; f [

Mr. James G. Koppler, Regional Director (s % 3;,4 ".

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U. S. Atomic Energy Conrnission

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G1en Ellyn, Illinoio 60137 , . ,,, t ' i

SUBJECT:

REPORT OF A1WORMAL OCCURRE1CE PER SIITION 6.6.B OF THE TECHNICAL SPIIIPICATIONS.

LE/dMGE IN FEEIT4ATER LINE PRESSURE TAP, UNIT 3.

References:

1) Regulatory Guido 1.16 Rev.1 Appendix A

2) Notification of Region III of M, Regulatory Operationa Tolophone: Mr. F. Maura, 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on September 21, 1974 Telegram: Mr. J. Keppler, 1245 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.737225e-4 months <br /> on September 23, 1974

3) Drawing Number M-347 (SiL)

Report Numbers 50-249/74-28 Report Dato: September 26, 1974 Occurrenco Date: Septetrbor 20, 1974 Facility: Drcoden Nuclear Power Station, Morris, Illinois IDD7PIFICATION OF OCCUR 3 DICE Leakago in foedwater line pressure tap, Unit 3.

CONDITIONS PRIOR TO OCCURRDICE Unit 3 was at a steady-state thermal power of 2222 K4t and an electrical load of 749 Im at the timo of the occurrenco.

DESCRIPPION O? OCCURRRCE

'At about 2010 hours0.0233 days <br />0.558 hours <br />0.00332 weeks <br />7.64805e-4 months <br /> on September 20, 1974, steam leakage and dropping water ucro noted on the fredwater line in the fecduater regulating valvo area.

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At 2020 hours0.0234 days <br />0.561 hours <br />0.00334 weeks <br />7.6861e-4 months <br /> on the same day, a load drop to shutdown at the rate of 100 We per hour was initiated. This drop had been scheduled previously for curveillance

- < testing unrelated to the present incident.

At 2022 hours0.0234 days <br />0.562 hours <br />0.00334 weeks <br />7.69371e-4 months <br />, the load drop rate was increased to 5 We per minuto as a j result of the present incident. .

At 2318 hours0.0268 days <br />0.644 hours <br />0.00383 weeks <br />8.81999e-4 months <br /> on September 20, 1974, Unit 3 was off system and locked in the shutdown mode.

Normal contamination control methods were utilized for this relatively small leak.

DESIGNATION OP APPAREN'P CAUSE OF OCCURRENCE (Equipnent Failure)

The junction point of pressure tap 3-3241-12A, a 3/4-inch line, with the 24-inch feedwater regulating valve inlet manifold, was cracked at the weld and leaking.

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ANALYSIS OF OCCURRENCE The leak as it exicted at the time of discovery posed only a local contamina-tion problem, with no appreciable effect on reactor operation. No damage to surrounding equipIlent occurred, and no unusual radiation exposures resulted.

The total leakage amounted to about six gallona of primary feedwater, which, bcing downstrema of the condensate domineralizers, has an activity of less than 10-7 Cutics per gallon (groso beta-gan=a),

i Had the leak developed before discovery into a i\tll breakaway of the pressure tap, the contamination problem in the vicinity of the leak would have been more sovere, but due to the relatively small size of the line, no danger to safe reactor operation or adequate core cooling would have cxisted. No danger to public or plant personnel existed at any time.

The junction wold that was leaking was probably strained during the severe vibrations that occurred in the Unit 3 feedwater system on June 23, 1974 (See Incident I12-3-74-20). All of the joints and welds in the 24-inch foodwater piping were checked by magnetic particle testing following that incident, but the 3/4-inch joint of the pressure tap was not checked.

CORRECTIVE ACTION The pressur#!e.ap involved, originally connected to a feedwater low preocure switch, is no longer used. Thus, the tap line was completely disconnected, and the jtuiction point capped and welded. Tho weld bead was magnetic particle tested for integrity.

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/ September 26, 1974

)I Mr. James G. Ksppl J  ;

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i In addition, the 3241-12B pressure tap line, also no longer used, was dio-i

. connected, and the junction capped, welded, and tested, to alleviate any similar failure in the future. . I These two taps are the only ones (of the many feedwater line taps) that are in the vicinity where severe vibrations occurred on June 23, 1974. (see ,

" Analysis of Occurrence" above).

PAILURE DATA' The failure occurred at the socket-welded joint between tho 3-3201 feedwater line (24-inch diamoter, of schedule 120 A 106 Grade B steel) and the 3-3241-12A pressure tap lino (3/4-inch diameter, of A-105 Grado II steel). See Reference 3 Sincere {y;,_

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B. B. Stephenson Superintendent BBStdo L.. -

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