ML20217P567
| ML20217P567 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/06/1998 |
| From: | Rainsberry J SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-97-05, GL-97-5, NUDOCS 9803100331 | |
| Download: ML20217P567 (4) | |
Text
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. !F EDISON
' ' " '". ' Plant Licensing Manager An wl50N 1[I1 RN AllpNAl* Company 1
i March 6, 1998 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C.
20555-0001
Subject:
NRC Generic Letter 97-05: Steam Generator Tube Inspection Techniques
)
San Onofre Nuclear Generating Station Units 2 and 3 j
Gentlemen:
This letter provides the information requested in Generic Letter (GL) 97-05,
" Steam Generator Tube Inspection Techniques." Steam generator tubes with indications may reain in service based on sizing at San Onofre Units 2 and 3.
Therefore, a description of the nondestructive examination method used and the technical basis for acceptability are provided. The information in this response represents current San Onofre Units 2 and 3 steam generator inspection practice and follows the suggested template developed by the i
Nuclear Energy Institute (NEI).
The Required Information to rc:; pond to GL 97-05 and the responses for San Onofre Units 2 and 3 are the following:
Generic Letter 97-05, Item 1: "Whether it is practice to leave steam gt...rator tubes with indications in service based on sizing."
Response
It is the practice at San Onofre to leave in service steam generator tubes
{)3 with " wear" indications which can be sized at less than the Technical Specification value of 4% of the tube wall thickness. The San Onofre Units 2 I
and 3 steam generators were designed by Combustion Engineering, and the commonly used "model designation" is "3410 Megawatt Thermal." The tubing 1
outside diameter dimension is 0.75 inches, and the tubing wall thickness is 0.048 inches (nominal).
9803100331 980306 PDR A90CK 05000361 P
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Document Control Desk Generic Letter 97-05, Item 2: "If the response to Item 1 is affirmative, those Licensees should submit a written report that includes, for each type of indication, a description of the associated nondestructive examination method being used and the technical basis for the acceptability of the technique used."
Response
Introduction The Electric Power Research Institute (EPRI) provides relevant industry guidance. Appendix H " Performance Demonstration for Eddy Current Examination," of the EPRI "PWR Steam Generator Examination Guidelines, Revisions 3 through 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 intergranular attack / stress corrosion cracking (IGA / SCC), primary-side SCC, and impingement damage for qualification.
1 For qualification purposes, test samp11s are used to evaluate detection and sizing capabilitics. While pulled to 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 y
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 tce Appendix H qualification process.
The procedures developed in accordance with Appendix H specify the essential variables. These essential variables are associated with an individual j
instrument, probe, cable, or particular on-site equipment configurations.
Additionally, certain techniques have undergone testing and review to quantify sizing performance. The sizing data set includes the detection data set for the technique with additional requirements for number and composition of the grading units.
j i
Sizina Techniaue l
l i
l At San Onofre a sizing technique for wear flaws is used during steam generator inspections to leave tubes with flaws in service. The basis for application of this sizing technique is the conduct of the examinations under the San Orofre Quality Assurance Program following the requirements of Technical
d Document Control Desk-Specifications 3.4.13.2, 5.5.2.11, and 5.7.2.c, and Sections XI and V of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel
' Code, 1989 Edition. Additional support for sizing wear flaws is provided by the EPRI Appendix H qualification data sets.
For wear, which can typically occur at eggcrate tube supports, diagonal straps, and vertical straps, sizing is determined using the 400/100 Kilohertz differential raix of the bobbin probe. A calibration curve for amplitude j
vertical maximum is determined based on the applicable standards replicating the damage mechanism type. The calibration curve reptesents the full range of expected depths. This sizing qualification is based on 81 sample points,
]
Samples ranged in depth from 4% to 78% through wall depth.
1 If you have any questions or would like additional information on this j
subject, please let me know.
Very truly yours, s
J. L. Rainsberry l
l
, Document Control Desk State of California Co'inty of San Diego ue M. [MbJ,
On m a A c A le, \\4 Fr before me, personally appeared
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O AMIAAa personally known to me to be the person whose name is subscribed to the within instrument and acknowledged to me that he executed the same in his authorized capacity, and that by his signature on the instrument the person, or the entity upon behalf of which the person acted, executed the instrument.
WITNESS my hand and official seal.
commwane usases m m ets u n u met my pee-causes I.
4 sontx.oo couer n:e,m rnwauernsu s
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Signature L LUo N.
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Enclosure cc:
E. W. Herschoff, Regional Administrator, NRC Region IV K. E. Perkins, Jr., Director, Walnut Creek Field Office, NRC Region IV J. A. Sloan, NRC Senior Resident Inspector, San Onofre Units 2 & 3 M. B. Fields, NRC Project Manager, San Onofre Units 2 and 3 1