ML20084S867
| ML20084S867 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 06/03/1971 |
| From: | Haueter R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084S870 | List: |
| References | |
| NUDOCS 8306200027 | |
| Download: ML20084S867 (2) | |
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9 General Othces 212 West MsChegan Avenue. Jackson, Michigan 49201. Area Code 517 788 05S0 June 3, 1971 9
Dr. P. A. Morris, Director Re:
Docket 50-255 D'. vision of Reactor Licensing License No DPR-20 United States Atomic Energy Commission Washington, DC 20545 Ihar Dr. Morris:
Att:
Mr. D. J. Skovholt This letter is written to apprise you of a recent difficulty with a component cooling water heat exchanger (E-54A) at the Palisades Plant. At the time this difficulty was detected, the early steps in the procedure for the initial approach to criticality were in progress with the primary coolant system at 260 F and 415 psia with 1910 ppm of boron in the coolant.
A low-level alam on the component cooling water surge tank and continued loss of water (following the tank refill) indicated a leak in the system. An inspection of all related systems disclosed the lack of external leakage.
Isolation of the E-54A heat exchanger stopped the loss of liquid, indicating the failure of a tube or tubes.
Sequence of Events May 22, 1971 - Initiated primary system heatup for the initial approach to criticality.
May 23, 1971, 1150 - Preparation completed for critical approach with system conditions of 260 F, 415 psia, refueling concentration of boron and a bubble was formed in the pressurizer.
May 23, 1971, 1415 - Low-level alarm on the component cooling water surge tank. Opened manual supply valve and filled tank to 70%.
May 23, 1971, 1430 - Toured facility to locate leak after tank level again went to 5%, requiring a second refill. No external leaks were located.
p May 23, 1971, 1500 - Isolated the component cooling water side u
of the E-54A heat exchanger.
May 24, 1971 - Water boxes removed from the heat exchanger for inspection and repairs.
Three tube leaks evident. The tubes were found to be broken off at the first baffle away from the inlet end tube sheet.
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June 3, 1971 Cause of Incident The tube failure was found to be in the same area as the earlier failures found during preoperational testing approximately a year ago.
) The problem is felt to be one of induced vibration caused by excessive
[ velocity over the tubes adjacent to the edges of the impact baffle at the shell side inlet nozzle.
_ Corrective Action The three leaking tubes will be repaired in the same manner as those repaired in May of 1970; namely, (1) the tube ends are drilled out to one-inch depth from the tube sheet face, (2) a 7/16-inch diameter steel bar is inserted the full length of the tube, (3) tube ends are plugged with an aluminum bronze tapered plug, and (4) the plug is welded to the tube sheet overlay by tungsten inert gas velding.
In order to limit the number of potential forced outages of the heat exchanger in the future, approximately forty (40) tubes in the area adjacent to those tubes which have failed will also be plugged.
It is planned to plug tubes in the second heat exchanger in a similar manner prior to the power test program to reduce the probability of induced vibration tube failures in that unit.
Conclusion The plugging of tube adjacent to the failed tubes should sig-nificantly reduce the probability of future tube failures in the units.
Since sufficient heat transfer area exists in the remaining 1,980 tubes, the plugging of the 40 tubes in the critical flow area vill not affect the calebility of the heat exchanger to perform its design functions.
Yours very truly, Robert L. Haueter (Signed)
RBS/ map Robert L. Haueter Electric Production Superintendent -
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