ML20084K794

AO 50-237/1974-46:on 740912,during steady-state Power,Leak Discovered in 2B Reactor Feed Pump Min Flow Line.Caused by Erosion of Min Flow Line Due to Leakage Past Normally Closed Min Flow Valve PCV-2-3201B.Patch Welded Over Leak

ML20084K794
Person / Time
Site:	Dresden
Issue date:	09/20/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084K796	List: ML20084K794 ML20084K812 ML20084K819
References
682-74, NUDOCS 8305190545
Download: ML20084K794 (2)

Text

TI ~. .. .

gy Ons First(

th Edison h Comm7 t . . Plaza. Chicago. Illinois p' y

A./jf] ' Address Nep)ly to:

Post Office Box 767

% ^$7 Chicago, Illinois 60690 BBS Ltr. #682-74 Dresden Nuclear Power Station R. R. #1 )

Morris, Illinois 60450 September 20, 1974 MMIl f n,.

s  % dR0 M -

Mr. James G. Kcppler, Regional Director 50-2'V n' I4 ' / ~/ I Directorate of Regulatory Operations-Ragion III U' b "'Y" ]

U. S. Atomic Energy Co::xnission U{A '

/ .1 ,W 799 Roosevelt Road ""~ 8/

Olen Ellyn, Illinois 60137 i

}

SUBJECT:

REPORT OF APMORMAL OCCURRENCE PER SECTIO'i 6.6.B OF THE TECHNICAL

_ SPECIFICATIONS.

2B REACTOR TEED PUMP MINIMUM FLO'.I LINE LEAK.

References:

1) Regulatory Guide 1.16 Rev. 1 Appendix A

2) Notification of Region III of AEC Regulatory Operations Telephone: Mr. F. Maura, 1450 hours0.0168 days <br />0.403 hours <br />0.0024 weeks <br />5.51725e-4 months <br /> on September 17, 1974 Telegram: Mr. J. Keppler,1552 hours0.018 days <br />0.431 hours <br />0.00257 weeks <br />5.90536e-4 months <br /> on September 17, 1974

3) Drawing Nunber: M-14 Report Number: 50-237/1974-46 Report Date: September 20, 1974 Occurrence Date: September 12, 1974 Facility: Decaden Nuclear Power Station, Morris, Illinois IDENTIFICATION OF OCCURRENCE At approximately 1510 hours0.0175 days <br />0.419 hours <br />0.0025 weeks <br />5.74555e-4 months <br /> on September 12, 1974, the Unic #2 NSO noted that the off-gas monitor indication decreased, condensor vacuum decreased, the flux-tilt monitor decreased, and off-gas air flow increased.

These changes are usually indications of increased air in-leckage to the main condenser. This condition represents an abnormal degradation of one of several boundaries designed to contain radioactive materials.

_ CONDITIONS PRIOR TO OCCURRENCE Prior to occurrence, the reactor was.in the run mode operating at a steady state power, 2250 MWt and 670 trn'e. Preparations were being made for a unit shutdown to investigate a leakage proble:n in the drywell.

DESCRIPTION OF OCCURRENCE A scarch was initiated for vacuum leaks during the shutdown and cooldown. On September 14, 1974, the Icak was discovered in the 2B reactor feed pump minimum flow line (2-3205B-6"-C). A similar leak occurred on August 23, 1974, on this line. The.fix at that time was to weld a patch on the leak. The leak this time occurred at the edge of the patch.

8305190545 740920 gDRADOCK 0500023 -

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• • • '* . James G. Keppir x ' Septcmb:r 20, 1974 O J l .

' ' DESIGNATION OF APPARENT CAUSE OF OCCURRENCE (other)

I - Apparent cause of the occurrence was erosion of the minimum flow line resulting from leakage past normally closed reactor feed pu=p

minimum flow valve PCV-2-3201B.

! ANALYSIS OF OCCURRENCE j The health and safety of the plant personnel and the public were not jeopardized as a result of this pin hole leak. During normal operation, this line is under vacuum conditions which indicated that Icakage would be into the line rather than out. Thus, the only water leakage would be

. during pump minimum flow conditions.

CORRECTIVE ACTIONS ne immediate corrective action was to weld a patch over the Icak.

In addition to the above action, a modification has been initiated to replace the section of line on all three minimum flow lines for Unit 2 and 3. The sections of pipe have been problem areas in the past due to the erosion created by the piping configuration. Rese carbon steel sections will be replaced with chrome-moly material which is more resistive to corrosion /crosion.

FAILURE DATA Previous failures occurred on June 12, 1973 and August 23, 1974.

In both cases, this scme section of piping was found to be croded. he corrective action was to weld a patch over the eroded area to prevent further leakage. The modification should solve this problem.

Sincerely, b'

. . Stephenson Superintendent BBS:lUH: sib e

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