ML20040F773
| ML20040F773 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 01/21/1982 |
| From: | Parker W DUKE POWER CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8202100290 | |
| Download: ML20040F773 (3) | |
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Vict Parsiormt Tre.tewoNg; Anta 704 Straw Pooouction 373-4083 January 21, 1982 Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 Re: Catawba Nuclear Station Units 1 & 2 Docket Nos. 50-413 and -414
Dear Mr. O'Reilly:
Pursuant to 10.CFR 50,55e, please find attached Significant Deficiency Report SD 413-414/81-33.
Ver truly yours,
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William O. Parker, Jr RWO/php Attachment cc: Director Mr. Robert Guild, Esq.
Office of Inspection and Enforcement Attorney-at-Law U. S. Nuclear Regulatory Commission 314 Pall Mall Washington, D. C. 20555 Columbia, South Carolina 29201 P. K. VanDoorn Palmetto Alliance NRC R(sident Inspector 213515 Devine Street Catawba Nuclear Station Columbia, South Carolina 29205 Pt CD 0
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s DUKE POWER COMPAhT CATAWEA NUCLEAR STATION REPORT NO:
SD 413-414/81-33 REPORT DATE: January 21, 1982 FACILITY:
Catawba Nuclear Station - Units 1 and 2 IDENTIFICATION OF DEFICIENCY:
Circumferential butt welds between piping components specified to be " flush" do not meet the ASME Code flush weld requirements of Table NB-3683.2-1, footnote (2)(a).
INITIAL REPORT:
On December 22, 1981, A. Ignatonis, NRC Region II, Atlanta, Georgia, was notified of this deficiency by W. O. Henry, D. L. Rehn, J. N. Underwood and R. W. Lonsall of Duke Power Company, Charlotte, N. C.
COMPONENT AND/OR SUPPLIER:
Flush welds performed by Duke Power on several Class 1 lines inside contain-ment.
DESCRIPTION OF DEFICIENCY:
It was reported that butt welds 2NC46-4 and 2NC49-8 do not meet the ASME Code criteria for being " flush" as specified in Table NB-3683.2-1, footnote (2)(a).
Specifically, the requirement that the finished contour of the weld shall not exceed a 7 slope had not been satisfied at the weld I.D.
In reviewing this nonconformance, it was determined that Construction Procedure CP-328 for flush welds may, in actual use, not provide sufficient direction to assure that the weld contour on the I.D. is s 7. On this basis, it is not certain whether other butt welds specified to be flush actually meet the same 7 l
contour requirement. The impact associated with this lies in the stress l
analyses used to demonstrate code compliance for these welds. Because they use the lower stress indices applicable to flush welds, the current adequacy of these calculations is now in question.
ANALYSIS OF SAFETY IMPLICATIONS:
The structural integrity of the affected piping systems is demonstrated by meeting the requirements of the ASME Code,Section III, Paragraph NB-3600.
These requirements are intended to assure gross structural strength as well as to prevent local fatique failure from cyclic loading conditions. For welds specified to be " flush", the lower stress indices permitted by the Code were utilized in the detailed stress calculations required to show code compliance. If the higher "as-welded" indices were employed in these calcula-tions, the result would be a reduction in the safety factor against possible fatigue failure. There would be no impact on the analyses used to determine and/or verify the gross structural strength of the piping or the overall system
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, response. The detailed stress calculations required by the Code also form input to the pipe rupture analyses necessary to meet the requirements of General Design Criteria 4, " Environmental and Missile Design Basis." By reducing the safety factor against fatigue failure (i.e., raising secondary and peak stresses), new break locations may be introduced into the pipe rupture analysis. As a result, postulated break locations may shift away from areas where designed protection was previously required.
CORRECTIVE ACTION:
Within Duke Power, the use of flush welds has been very limited compared to the total number of butt welds utilized.
Currently, there are approximately 185 flush welds specified for both Catawba Units 1 & 2.
Not all of them have been installed. Flush welds appear on various Class 1 lines inside contain-ment. The majority are on small 2 to 3 inch piping. The structural analysis associated with the subject welds has been recently completed, and is currently underway or is scheduled to'begin in the next 12 months.
To determine the effect of switching from flush weld to as-welded indices, a conservative, worst case engineering assessment was performed. This effort considered all affected stress calculations sufficiently complete at this time. For Catawba Unit 1 essentially 100 percent of the subject Code analyses and approximately 50 percent of the pipe rupture analyses were considered.
For Catawba Unit 2, approximately 30 percent of the Code and none of the pipe rupture work were available for consideration. The results of this assessment indicated that all flush welds that have been analyzed could be qualified as as-welded welds. Also, in the pipe rupture area, no significant impact was determined.
In response to the current situation concerning flush welds, all affected piping design drawings will be revised to indicate that the flush welds specified should not be regarded as meeting the requirements of Table NB-3683.2-1, footnote (2)(a) of the ASME Code.
(Because this weld is, in reality, superior to an as-welded weld, Duke Power would like to retain their known i
location for possible future use.) All calculations currently complete will be revised to reflect either the as-welded stress indices or weld indices determined in accordance with paragraph NB-3681(c) of the ASME Code. Similarly, l
l calculations that are presently underway or scheduled will be performed using the as-welded indices or weld indices determined in accordance with paragraph NB-3681(c) of the ASME Code. These corrective measures complete the necessary actions with regard to the subject deficiency at Catawba Units 1 & 2.
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