ML18044A407
| ML18044A407 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 12/11/1979 |
| From: | Huston R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-79-13, NUDOCS 8001110031 | |
| Download: ML18044A407 (6) | |
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consumers Power company General Offices: 212 West Michigan Avenue, Jackson, Michigan 4g:201
- Area Code 517 788-0550 December 11, 1979 Mr James G Keppler Off ice of Inspection and Enforcement Region III US Nuclear Regulatory CoD1Dission 799 Roosevelt Road Glen Ellyn, IL 60137 DOCKET 50-255 - LICENSE DPR PALISADES PLANT - IE BULLETIN 79-13 Enclosed (Attachment 1) is Consumers Power Company's response to Item 6 of IE Bulletin 79-13.
Please note that this is a preliminary report.
This information was informally transmitted to the Office of Nuclear Reactor Regulation on October 25, 1979.
Rog Senior Licensing Engineer CC:
Director, Office of Nuclear Reactor Regulation Director, Office of Inspection & Enforcement Attachments (2)
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ATTACHMENT 1 Palisades Feedwater Pipe Investigation/Repair
PALISADES FEEDWATER PIPE INVESTIGATION/REPAIR INSPECTION During the Palisades Plant's scheduled refueling outage in September of 1979, Consumers Power Company inspected portions of the Plant's two feedwater lines as called for in IE Bulletin 79-13.
These inspections were conducted in accordance with letters to Mr J G Keppler dated July 13, 1979 and July 30, 1979.
In the course of conducting the weld examination using UT techniques, non-geometrical indications exceeding Code allowable levels were detected.
These areas were also examined by radiography and the presence of.cracking was confirmed.
Radiography was performed utilizing a pr9cedure developed by Westinghouse and used at a number of other PWR reactor sites for examination of feedwater line welds.
Radiographs were taken of the steam generator feedwater nozzle to transition piece weld (see Figure 1), transition piece to pipe weld and the welds at either end of the next two elbows proceeding away from the steam generator (Figure 2).
Indications of micro-and craze-cracking were found on all six welds on the feedwater line to Steam Generator B and on five of six welds on the line to Steam Generator A (the vertical side of the second elbow tested out satisfactorily).
In view of the results, four additional welds were examined on the line to B steam generator and two additional welds on the A steam generator were examined as indicated in Figure 2.
ANALYSIS OF INSPECTION RESULTS 1
Westinghouse and Combustion Engineering were asked to assist in the evaluation of the test results described previously.
The thru-wall dimension of flaws was checked and measured to be approximately 100 mils maximum (pipe wall =
0.750").
The experience noted in investigation of cracking at other plants was reviewed in detail.
Westinghouse and CE reviewed UT and RT results.
After examining the radiographs, Westinghouse offered the opinion that the flaw indications appeared to be typical of those found at other plants where shallow crack-like indications were present.
Both organizations concurred in the interpretation of the results.
Experience at other sites indicated that the cracking was found only on horizontal runs of piping.
This experience was borne out at Palisades, except the vertical leg of one elbow did reveal crack-like indications.
The indications at Palisades were not typically associated with the welds but occurred adjacent to welds, initiated on the ID and were circumferentially
oriented.
Some of the indications occurred at a geometrical discontinuity associated with a counterbore on the piping ID.
REPAIR AND REPLACEMENT Even though the indications did not seem to present a situation where piping failure was an imminent possibility, it was decided to replace the affected piping and fittings rather than experience the.additional expense and outages associated with continued periodic inspections and evaluations.
2 The piping and elbows are being replaced in the exact configuration as originally installed with minor exceptions.
The transition piece between the steam generator feedwater nozzle and piping is being ~eplac~d with a straight run of piping to eliminate one unnecessary weld and the elbows are being replaced with Schedule 80 thickness fittings rather than the original Schedule 60.
This is being done to accomplish an expanded wall thickness at the weld joints with respect to pipe wall. This expanded wall thickness is another minor design change accomplished to essentially eliminate stress concentration effects in the as-welded configuration.
The pipe and fitting material meets the requirements of the specification of the piping it replaces.
During the repair welding sequence, intermediate, tempering heat treatments at approximately S00°F will be performed on the steam generator nozzle prior to cooling for in-process radiography to minimize chances of cracking due to stresses and metallurgical effects imposed by welding.
Following post-weld stress relieving, completed pipe joints will be radiographed as a quality check and to provide a *baseline for future inservice inspections.
The repair is expected to be completed without deleterious effect on the present refueling outage schedule.
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