ML20217P580
| ML20217P580 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 03/03/1998 |
| From: | Mccoy C SOUTHERN NUCLEAR OPERATING CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-97-05, GL-97-5, LCV-1174, NUDOCS 9803100336 | |
| Download: ML20217P580 (4) | |
Text
C. K.McCoy Southern Naclear Vice President 0 prating Company, lac.
Vegtle Projstt 40 inverness Center Parkway P0. Box 1295 Birmingharn. Alabama 35201 Tel 205.992.7122 Fax 205 992.0403 SOUTHERN COMPANY Energyto Sm eYourWorld*
March 3, 1998 LCV-1174 Docket Nos.: 50-424 and 50-425 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington D. C. 20555-0001 Ladies and Gentlemen:
VOGTLE ELECTRIC GENERATING PLANT 90-DAY RESPONSE TO GENERIC LETTER 97-05, i
STEAM GENERATOR TUBE INSPECTION TECHNIOUES By Generic Letter 97-05, datcd December 17,1997, the Nuclear Regulatory Commissior.
(NRC) requested information relating to steam generator tube inspection techniques.
Specifically, the NRC questioned whether it is Vogtle Electric Generating Plant's (VEGP) practice to leave steam generator tubes in service with indications based upon sizing. If so, a list of the types ofindication along with a description and technical basis for the nondestructive examination inethod used should be provided. Provided as an attachment to this letter is the specific information requested by G.L. 97-05.
Mr. C. K. McCoy states that he is a vice president of Southern Nuclear Operating Company and is authorized to execute this oath on behalf of Southem Nuclear Operating Company and that, to the best of his knowledge and belief, the facts set forth in this letter and attachment are true.
SOUTHERN NUCLEAR OPERATING COMPANY By:
C. K. McCoy
/I8f Sworn to and subscribed before me this day of LI dA C L
,1998.
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NORMS U. S. Nuclear Regulatory Commission
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Mr. L. A. Reyes, Regional Administrator Mr. D. H. Jaffe, Licensing Project Manager, NRR Mr. J. Zeiler, Senior Resident Inspector, Vogtle State of Georgia Mr. L. C. Barrett, Commissioner, Department of Natural Resources 1
l 1
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LCV-1174
"~
r ATTACHMENT i
Vogtle Electric Generating Plant Response to Generic Letter 97-05 1
1)
Is it the practice at Vogtle Electric Generating Plant (VEGP) to leave steam generator tubes with indications in service based on sizing?
At VEGP steam generator tube indications which are sized and found to be less than the limits stated in the technical specification are left in service.
2)
If the response to item (1) is affirmative, submit a written report that includes, for each type ofindication, a description of the associated nondestructive examination method being used and the technical basis for the acceptability of the technique used.
1 The nuclear power industry recently voted to adopt an initiative requiring each utility to meet the intent of the guidance provided in NEI 97-06, Steam Generator Program Guidelines, no later than the first refueling outage starting after January 1,1999. As discussed in NEI 97-06, each utility is required to follow the inspection guidelines cor.tained in the latest revision of the EPRI PWR Steam Generator Examination i
Guidelines.
)
Appendix H, Performance Demonstration for Eddy Current Examination, of the PWR Steam Generator Examination Guidelines: Revision 5, provides guidance on the qualification of steam generator tubing examination techniques and equipment used to detect and size flaws. Damage mechanisms are divided into the following categories: thinning, pitting, wear, outside diameter IGA / SCC, primary-side SCC, and impingement damage for qualification.
For qualification purposes, test samples are used to evaluate detection and sizing capabilities. While pulled tube samples are preferred, fabricated samples may be used. If fabricated test samples are used, the samples are verified to produce signals similar to those being observed in the field in terms of signal characteristics, signal amplitude, and signal-to-noise ratio. Samples are examined to determine the actual through wall defect measurements as part of the Appendix H qualification process.
The procedures developed in accordance with Appendix H specify the essential' variables for each procedure. These essential variables are associated with an individual instrument, probe, cable, or particular on-site equipment configurations.
Additionally, certain techniques have undergone testing and review to quantify sizing performance. The sizing data sets includes the detection data set for the technique with additional requirements for number and composition of the grading units.
ATTACHMENT l
Vogtle Electric Generating Plant Response to Generic Letter 97-05 SIZING TECHNIQUES At VEGP the following sizing techniques are used during steam generator inspections to leave flaws in service. The basis for application of these sizing techniques is the conduct of the examinations under the VEGP Quality Assurance Program following the requirements of Section XI and V of the ASME Code,1989 Edition and Regulatory Guide 1.83. Additional support for sizing degradation-specific mechanisms is provided by the EPRI Appendix H qualification data sets.
WEAR For wear at tube support plates and anti-vibration bars, sizing is accomplished using the 630/160 differential mix of the bobbin probe. A calibration curve for maximum vertical voltage amplitude is determined based on the 0%,20%, and 40% holes on the calibration standard.
This sizing qualification is based on 64 sample data points. The samples ranged in depth from 4% to 78% through wall depth. This database has been reviewed to ensure that application of the sizing procedure is consistent with the steam generator conditions at VEGP. Therefore, the sizing procedure for wear is site-qualified for VEGP in accordance with paragraph 6.2.4 of the PWR Steam Generator Examination Guidelines: Revision 5.
MANUFACTURING PURNISH MARKS Manufacturing burnish marks (MBM) signals in thermally treated Alloy 600 tubing have been shown by comparative analysis to remain unchanged while in service; therefore, MBM's are not sized at VEGP. MBM's are dispositioned in accordance with Appei.mx F Category VII of the PWR Steam Generator Examination Guidelines,~ Rev.5. The 160 kHz absolute frequency is used for detection and recording these signals. A history review back to the base-line examination is performed on these signals to ensure that they have not changed during plant operations. An eddy current database is utilized in recording and tracking all MBM's. !