ML20216F596
| ML20216F596 | |
| Person / Time | |
|---|---|
| Issue date: | 04/09/1998 |
| From: | Wen P NRC (Affiliation Not Assigned) |
| To: | NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9804170127 | |
| Download: ML20216F596 (3) | |
Text
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April 9,1998 NOTE T0:
FILE FROM:
Peter C. Wen. Project Manager /
C' Generic Issues and Environmental Projects Branch Division of Reactor Program Management
SUBJECT:
TELEPHONE CONFERENCE CALL.BETWEEN NRC AND NEl ON MARCH 19, 1998
REFERENCE:
NRC letter to NEI, " Proposed Data Exclusion Criteria and Adjustment of Measured Leak Rate for Tube R28C41 (Plant S)," Dated February 26, 1998.
The purpose of this note is to document the telephone conversation between the NRC and NEI representative regarding the referenced subject.
The telephone conference report is attached.
Background:
To address the steam generator tube repairing issue, the NEI submitted EPRI Report, " Steam Generator Tubing Outside Diameter Stress Corrosion Cracking at Tube Support Plates Database for Alternate Repair Limits," (NP 7480-L-V2-R2),
Volume 2. for staff review.
In the-referenced letter, the staff indicated that it needed~ additional information to complete the review. The telephone-conference call was held as a result of NEI's response to staff's request for additional information.
Attachment:
As stated Distributiorn
/ Central File PDR F. Akstulewicz E. Sullivan
- p. Rush (0-7D4)
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a iP From:
"Keating. Robert F." <keatinrf@ westinghouse.com>
To:
"Srikantiah, Kanti" <gsrikant@epri.com>, TAP <pitt..
Date:
3/20/98 9:19am
Subject:
ODSCC Data Exclusion Criteria Telephone Conference Report - 3/19/97 $
Purpose:
Discuss NRC RAls on Data Exclusion Criteria and Leak Rate Adjustments
Participants:
R. Keating and T. Pitterle (W)
K. Srikantiah (EPRI)
C. Callaway (NEI)
P. Rush (NRC)
Reference:
NRC letter, " Proposed Data Exclusion Criteria and Adjustment of Measured Leak Rate for Tube R28C41 (Plant S)," T. Essig (NRC) to D. Modeen (NE!), February 26,1998.
Messrs. Callaway, Srikantiah, Pitterle and Keating called Mr. Rush to discuss information provided in the reference letter.
- " Data Exclusion Criteria ~
Criterion 3b:
The reference indicated that the NRC did not concur with EPRI exclusion criterion 3b. Phil explained that he had reviewed similar versions of the criterion and the staffs previous positions on it. He concluded that the current version of the criterion was not substantively different from previous versions. Hence, the staffs position that the criterion relied too heavily on statistical arguments relative to expectations, i.e., in essence relied only on the measured value of the
)
leak rate being abnormaly low and not the causes for the low leak rate.
Westinghouse noted that the criterion had a second part which related the change in leak rate from normal operation to SLB conditions. In addition to the statistical requirement on the magnitude of the leak rate relative to expectation, the SLB leak rate had to be less than 10%
greater than the normal operation leak rate. If the leak rates are that close during the test, it is implied that something is amiss with the testing. This knowledge indicates that the SLB result would be artificially low and shouldn't be used in ll a correlations.
The conclusion of the discussion was that Criterion 3b will be removed j
from the upcoming EPRI database submittal (and, of course, it will not be applied).
Criterion 3a:
1 The reference indicated that the NRC concurred with the physical and statistical basis for the establishment of Criterion 3a, with the exception that the EPRI prcposed one-sided prediction interval of 95%
for determining eligibility be increased to a 99% one-sided prediction interval.
NEl, EPRI, and Westinghouse concurred w@ the NRC 3 commendatica. The database update document will reflect the c hange in criterion 3a. The application of the criterion will result in omihing the data from the leak tests of MB-598-3 and MB-604-2 from the leak rate correlation analysis for 3/4" diameter tubes. It was also noted that no data from 7/8" diameter tubee wot/.; be eliminated using the 3a criterion.
[ Afterthought: This does.n affect the consideration of the specimens
o o
relative to probability of leak.]
- Leak Rate Adjustment ***
The background for this discussion is that the leak rate testing of the R28C41 tube specimen from Plant S was not successful. The indication was considered by the staff, and the industry, to be too significant to omit from the database, so the leak rate was calculated from the geometry of the crack and included in the database as a test result.
For the original calculation of the leak rate from the R28C41 specimen, using the computer code CRACKFLO, the total length of the crack after an attempted burst test was considered. The CRACKFLO cciculation is based on verifying theoretical considerations using empirical data and considers the potential for effective extension / opening of the crack during a SLB event. Hence, the use of the total measured length results in a calculated leak rate length greater than the actual crack length after attempting the burst testing. The most recent calculation of the leak rate was based on using the measured throughwall length that existed prior to the attempted burst test. This is based on the corrosion length of the crack. The resulting leak rate was calculated to be 1250 lph versus the original calculation of 2496 lph. It was noted that the calculation assumes the entire length to be throughwall with no intemalligaments. Hence, the calculation is consersative relative to the potential effect of intemal ligaments.
It was concluded that the leak rate value of 1250 lph will be used in the correlation analysis for 3/4" diameter tubes. A comprehensive response to the staffs questions will be included in the database submittal.
if you have any comments or questions regarding this information please contact me at the return email address or at (724) 722-5086.
R. F. Keating Equipment Design & Regulatory Engineering CC:
RFK <keatintf@ westinghouse.com>
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