ML19319E091
| ML19319E091 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 07/28/1972 |
| From: | Reinmuth G US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Henderson J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML19319E080 | List: |
| References | |
| NUDOCS 8003310600 | |
| Download: ML19319E091 (2) | |
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UNITED STATES
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ATOMIC ENERGY COMMISSION 5
- WASHINGTON. D.C. 20545
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JUL 2 81972 J. B. Henderson, Chief Reactor Construction Branch, R0 RANCHO SECO PIPE BUTT WELD IMPERFECTIONS (CDR-NO. 7)
We have reviewed the Bechtel status report of May 30, 1972, submitted by SMUD describing investigations and proposed resolution on the piping butt weld imperfections found at the Rancho Seco facility.
Mr. Collins has also reviewed Bechtels investigation program uhich included radiography, welding and uetallurgical studies of field production, field test and laboratory test welds.
Results of the program were discussed during an earlier visit to Bechtel San Francisco Offices on May 2, 1972. From these activities we offer the following comments and recommendations:
1.
We concur that, in this case, dark line densities exhibited on radiographs due to pipe concentricity mismatch could mask adverse defects. The repair to all butt weld pipe joints of safety related systems shown by such radiography evidence appears to be an appropriate corrective action.
Since these repairs will necessarily require modification of existing procedures, now apparently inadequate, it is recommended that the welding, inspection,and related QA documentation be reviewed in detail by the RO inspector to assure satisfactory repairs where effected.
2.
Based on'the information available, we question the Bechtel premise. that butt welds whose radiographs show light density lines contain " minor imperfections" which meet the applicable code and thus are not subject to repair consideration.
It should be noted that the metallographic correlations (fig. 1, 3, 4) exhibit a strong possibility that zones of incomplete fusion exist.
In this regard, we note that Bechtel is committed to a combined analytical and physical testing program to evaluate the effects of minor imperfections on the structural integrity of affected butt welds and to make the results of this study available for regulatory review.
The' TAB will review the licensees final report on this matter when received.
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J. B. Henderson,.
We wish to point out that even though an evaluation is made and found acceptable by the AEC, the AS;E Code /USAS Standard rules do not address or accept evaluation in lieu of repair.
Therefore, the licensee would continue to be in technical violation of the code unless relief is - sought through a code case ruling.
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We note the report addresses certain remedial measures being taken in the field pipe welding program to preclude recurrence of this problem. It is recommended that an on going site review be made of the Technical and QA corrective actions to assure its effective implementation.
J lac mu G. W. Reinmuth, Chief Technical Assistance Branch, RO cc:
F. E. Kruesi P. A. Morris LL.,D. Thornburg R. H.'Engelken J. G. Keppler G
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