ML022810255
| ML022810255 | |
| Person / Time | |
|---|---|
| Issue date: | 10/08/2002 |
| From: | Bateman W NRC/NRR/DE/EMCB |
| To: | Marion A Nuclear Energy Institute |
| References | |
| Download: ML022810255 (3) | |
Text
October 8, 2002 Mr. Alexander Marion, Director Engineering Department Nuclear Generator Division Nuclear Energy Institute 1776 I Street N.W. Suite 400 Washington D.C. 20006-3708
Subject:
EXCLUSION OF FRENCH DATA FROM THE STEAM GENERATOR DEGRADATION SPECIFIC MANAGEMENT DATABASE
Dear Mr. Marion:
On February 21, 2002, NEI representatives met with the NRC staff to propose several improvements in the leak rate methodology for the steam generator tube outside diameter stress corrosion cracking (ODSCC) alternate repair criteria. One of the proposed improvements was to exclude the French pulled tube data from the ODSCC database. The current ODSCC database consists of steam generator tube data from domestic and French nuclear power plants and is used in the steam generator tube integrity assessment as a part of the voltage-based alternate repair criteria for degraded tubes. By a letter dated July 25, 2002, NEI submitted for NRC staff review the proposed exclusion criterion. By a letter dated August 14, 2002, the NRC staff requested additional information from NEI and on October 4, 2002, NEI responded to the staffs request.
On the basis of statistical analyses, NEI showed that there is a statistical difference between the French and domestic data and that the French data and domestic data do not appear to come from the same population. The statistical difference is supported by the physical differences in crack morphology. Physically, the French indications tend to be of high bobbin voltage with short throughwall lengths whereas the domestic indications that are in the high voltage range have longer throughwall lengths. Also, the high voltage French indications had no leakage whereas all domestic high voltage indications show leakage. NEI concluded that the high voltage, non-leaking indications in the French data are the major contributor to the differences between French and domestic data. After reviewing the information submitted by NEI, the NRC staff concludes that the French data may be excluded from the ODSCC database because NEI has provided sufficient technical information to demonstrate that the French data are physically and statistically different from the domestic data.
It should be noted that whenever the ODSCC database is updated, NEI will perform confirmatory analyses to demonstrate that the French data remain statistically and physically different from the domestic data.
Mr. Alexander Marion 2
If you have any questions, please contact Louise Lund (301-415-3248) or John Tsao (301-415-2702) of my staff.
Sincerely,
/RA/
William H. Bateman, Chief Materials and Chemical Engineering Branch Division of Engineering Office of Nuclear Reactor Regulation cc: J. Riley, NEI
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EMCB:DE NAME JTsao:jct KKarwoski:kjk Llund:cbk for all WBateman:whb DATE 10/ 8 /02 10/ 8 /02 10/ 8 /02 10/ 8 /02