ML20045G351
| ML20045G351 | |
| Person / Time | |
|---|---|
| Site: | Mcguire, Catawba, McGuire  |
| Issue date: | 07/01/1993 |
| From: | Tuckman M DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9307130228 | |
| Download: ML20045G351 (3) | |
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DukeMer Company M S Tucuwv PO Box 1006 Senior Vice President Charlotte, NC28201-1006 Nuclear Generation (704)382-22000Wice (704)38243G0 Fax
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DUKEPOWER July 1,1993 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 2.0555
Subject:
McGuire Nuclear Station Units 1 and 2 Docket Nos. 50-369,370 Catawba Nuclear Station Unit 1 Docket No. 50-413 Use of ASME Code Case N-10 The purpose of this letter is to request approval in accordance with'10 CFR 50.55a(a)(3) of ASME Code case N-10, Time of Examination for Class 1,2, and 3 Section III Vessels, in the fabrication process for the replacemeat team generators for McGuire Units 1 and 2 and Catawba Unit 1. The inability to use Code Case N-10 will cause a significant impact on the ability to meet the schedule necessary for the steam generator replacement outages.
The new Steam Generators are being fabricated to the 1986 Edition of ASME Section III.
The content of Code Case N-10 has been incorporated into ASME Section III Article NB-5000, paragraph NB 5120 (a)(2),1986 Edition (1986 Addenda). Due to the physical shape and internal structuring (within the steam generator), Babcock & Wilcox uses both ultrasonics and radiography to assure the freedom of defects in the pressure boundary welds.
The use of Code Case N-10 has the following advantages:
- 1. The radiographic and ultrasonic techniques are complementary. Defects which because of their size and orientation may not be detectable by radiography are detected by the ultrasonic method.
- 2. Since the Section XI in-service examination is performed by ultrasonics (due to inaccessibility of welds for radiography) the use of ultrasonics to Section III acceptance criteria during fabrication reduces the number of recordable indications that may be found during in-service examinations. This reduces the time and radiation exposure to examination personnel.
i 120008 DR ADOCK 05000369 PDR 4..
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1 U. S. Nuclear Regulatory Cormnission -
July 1,1993 Page 2
- 3. The inspection program for the replacement steam generators includes the following:
RT to Section III criteria before PWHT UT to Section III criteria before PWHT UT to Sections III criteria after each PWHT UT to Section XI criteria after hydrostatic test This will result in superior weld quality to welds examined to minimum Section III requirements. There is a very high confidence level that the ultrasonic inspection, used -
after (and prior to) post weld heat treatment, detects discontinuities that may occur due to the heat treatment cycle Code Case N-10 was approved for use for several years before being incorporated into the ASME 1986 Edition,86 Addenda. This, along with the fact that the content of Code Case N-10 has been incorporated into the current version of the ASME Code, caused our supplier (BWI) to take credit for the alternate examination the Code Case allows in their schedule.
Duke Power is requesting approval by July 15,1993.
Very truly yours, MM.. E. ekcV -
rw M. S. Tuckman
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U.S. Nuclear Regulatory Commission July 1,1993
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S. D. Ebneter Regional Administrator R. E Martin, ONRR V. Nerses, ONRR R. J. Freudenberger Senior Resident Inspector (CNS)
P. K. Van Doorn Senior Resident Inspector (MNS)
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