ML20084R645

RO 50-249/75-04:on 750107,pin Hole Leak Discovered in Reactor Feed Pump 3B Min Flow Line to Condenser.Caused by Swirl Being Created by Velocity Change Through off-set Reducer.Failed Section of Pipe Isolated & Repaired

ML20084R645
Person / Time
Site:	Dresden
Issue date:	01/17/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
39-75, RO-50-249-75-04, RO-50-249-75-4, NUDOCS 8306150268
Download: ML20084R645 (2)

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l R. R. #1 Morris, Illinois 60450 January 17, 1975 Mr. James G. Keppler, Regional Director Directorate of Regulatory Operations-Region III U. S. Atomic Energy Co:::nisssion 799 Roosevelt Road Glen Ellyn, Illinois 60137

SUBJECT:

REFORT OF AE:0RMAL OCCURRE'JCE PER SECTION 6.6.A OF THE TECHNICAL SPmIF_IS ATTMS REiLCT0h PEED FU7P MIIGGI FIFJ LINE LEAK

References:

1) Regulatory Guide 1.16 Rev. 1 Appendix A

2) Notification of Region III of AEC Regulatory Operations Telephone: P. Johnson, 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on January 8, 1975 Telegram: Mr. James G. Kcppler, 1555 hours0.018 days <br />0.432 hours <br />0.00257 weeks <br />5.916775e-4 months <br /> on January 8, 1975

3) Dresden Station Drawings M-347 and M-370 Report Number: 50-249/1975-4 Report Date: January 17, 1975 Occurrence Date: January 7, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois /

IDENTIFICATION CF OCCURREICE Pin hole leak in 33 reactor feed pump ninicra flow line to condenser. This occurrence represents an. abnormal., degradation of a boundarydes,igned to contain radioa'ctive reatorial.

CONDITION PRIOR TO OCCURRENCE Prior to the occurrence the unit was in the process of heating up. The mode switch was in the startup position and reactor pressure was about 475 pais.

8306150268 750117 PDR ADOCK 05000249 S PDR 721 M.V . o 3973

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,,Mrs' James G. K ppler fl /3 January .17,1975 v U DESCRIPTION OP OCCURENCE On January 7, 1975 at about 1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br /> a pin hole leak was detected in J the 3B reactor feed pump minimum flow line to the condenser. The leak j was discovered while the 3B reactor feed p p was in service. The leak I I

occurred at a six inch to a three inch reducer on the pumpside of the main condenser isolation valve.

DISIGNATION OF APPARENT CAUSE OF OCCURRENCE (Design Error)

The failure of the pipe was due to a 'avirl being created by a velocity change through the off-set reducer. The swirling action caused the pipe in the area of the reducer to erode at a rate greater than that considered in the original design.

ANALYSIS OF OCCURRENCE The failure of the 3B reactor feed p ps minimum flow line to the condenser did not place the safety of the plant or public in jeopardy. At the time of the failure only one feed pump was required. With both the 3A and the.30 fecd puraps available for operation, unit startup vas continued. In addition, all safety core cooling systems were operational at the time of the failure.

CORRECTIVE ACTION The imaediate corrective action taken was to isolate the failed section of pipe and to patch the leak. Additional corrective action will be taken during the next unit refueling outage when the mild steel portion of the line will be replaced with a chrome-moly section to reduce erosion (Modification M12-3-74-164).

FAILURE DATA Failures of this type have occurred in the past and a modification has been submitted to replace the minimum flow lines of the feed pumps in the arca of reducers during the next refueling outage.

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, gb B. B. Stephenson

] Superintendent BBS:TEL:smp File /AEC s ,

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