ML19254F332
| ML19254F332 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 10/24/1979 |
| From: | Peoples D COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-79-13, NUDOCS 7911090068 | |
| Download: ML19254F332 (2) | |
Text
Commonwealth Edison One First National Plaza. Cmcago likno!s Address Reply to: Post Office Box 767 Chicago. Illinois 60690 October 24, 1979 Mr. James G. Keppler, Director Directorate of Inspection and Enforcement - Region III U.S. Nuclear Regulatory Commission Glen Ellyn, IL 60137
Subject:
Zion Station Units 1 and 2 Inspection of Feedwater System Piping Welds in accordance with IE Bulletin 79-13 NRC Docket Nos. 50-295/304
Dear Mr. Keppler:
As a result of the continuing evaluation of the previously reported linear indications detected in the feedwater nozzle welds at Zi.on Unit 1, we have interpreted the indications as. evidence of possible cracking in the weld prep counterbore-to-ramp angle areas, the same locations that showed linear indications on the original construction radiographs.
We have performed the radiography as required by I.E.
Bulletin 79-13 on all four Unit 1 feedwater nozzle welds.
Addi-tionally, we have made and evaluated radiographs with techniques more sensitive in detecting cracking in both the nozzle and pipe side weld prep ramp angles of these welds.
Supplementary ultra-sonic inves tigations have also been performed.
These examinations have detected linear indications on all four steam generator feed-water piping-to-nozzle joints on both sides of the welds.
We have also performed radiography on two piping welds upstream of each nozzle.
No evidence of cracking or unacceptable code disconti-nuities were found in any of these upstream piping welds.
The evidence from.these investigations have been compared to the original construction radiographs.
Also, Westinghouse per-sonnel familiar with other investigation results provided a com-parison of severity in relation to their experience at other plants.
Based on judgements of radiographic film density and ultrasonic examinations, we believe any possible cracking to be shallow in relation to the nozzle and pipe wall thickness of 1.218 inches, and not of sufficient depth to adversely effect piping integrity.
1301 225 JG or i
4 1979 7 911090 0 b S k
Commonwealth Edison NRC Docket Nos.
50-295/304 Mr. James G. Xeppler October 24, 1979 In pursuit of a final determination, we are in the process of removing the nozzle to elbow weld of Loop A Steam Generator in order to conduct metallurgical examinations.
This weld is judged to be representative of the indication deptha and is the most severe in terms of indication length (360o).
Results of these metallurgical examinations are' expected to be available by November 5,1979, and will be used as a basis for further judgement on the necessity to inspect Zion Unit 2.
The following facts provide our basis for continued aper-ation of Zion Unit 2 until the scheduled shutdown for inspection on December 2, 1979 1.
Original construction radiographs for Unit 2 showed fewer and less pronounced indications than the construction radiographs for Unit 1.
Zion 2 therefore began operation with fewer sites for crack initiation.
2.
Zion Unit 2 has not been in operation as long as Unit 1.
Since any cracking would be ex-pected to propagate at similar rates in both units, potential cracking in Unit 2 would be expected to be even shallower than that which exists in Unit 1.
Our evaluation based on the above evidence is that we do not anticipate a significant decrease in Unit 2 feedwater piping integrity.
We intend to continue power operation on Unit 2 until the scheduled shutdown on December 2, 1979, to perform the nozzle inspections required by I.E.Bulletin 79-13 Very truly yours,
/$48'F vd D. L. Peop es Director of Nuclear Licensing i301 226
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