ML20115H396
| ML20115H396 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 07/15/1996 |
| From: | Dennis Morey SOUTHERN NUCLEAR OPERATING CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9607230100 | |
| Download: ML20115H396 (4) | |
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Southem Nucber Oper: ting Company Poet Once Box 1295 Birminghtm, Alibima 35201 T& phons (205) 868-5131 Southern Nudear Operating Company oev. uor.y Vice President Farley Project the Southern electHC System July 15,1996 Docket No.: 50-364 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington,DC 20555 Joseph M. Farley Nuclear Plant - Unit 2 Steam Generator F* Technical Specification Arnendment Ladies and Gentlemen:
1 By letter dated April 22,1996, and supplemented by letter dated May 3,1996, Southern Nuclear Operating Company requested an amendment to the current F* technical specification for Farley Unit 2.
During recent discussions with the NRC Staff, Southern Nuclear was requested to prwide a methodology for determining the oddy current NDE measurement uncertainty to be used in conjunction with F*. 'Ihe requested ekadalogy is attached Should Southern Nuclear plan to signi6cantly deviate from this methodology the NRC staff will be notified.
If there are any questions, please advise.
Respectfully submitted, 31tVt Dave Morey Sworn to andsubscribed before me this /Yday of aOn 1996 HsEb di
" horaryrubric '
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My Commission Expires: Am A Y. /99 ')
G REM / cit:NDEMETH. doc 9607230100 960715 Attachment PDR ADOCK 05000364 P
PDR cc: Mr. S. D. Ebneter, Region II Administrator
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Mr. B. L. Siegel, NRR Senior Project Manager KD0 Mr. T. M. Ross, FNP Sr. Resident Inspector I
Dr. D. E. Williamson, State Department ofPublic Health
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Mr. T. A. Reed, NRR - Materials and Chemical Engineering Branch
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Attachment l
Methodology for the Determination of NDE Measurement Uncertainty
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O ATTACHMENT l
Methodology for the Determination of NDE Measurement Uncertainty j
t Backaround Various NDE techniques which support alternate repair criteria require the measurement of the position or inclination of a detected flaw. The alternate repair criteria typically cite a structurally based flaw length, position or inclination requirement and then allow for an NDE measurement uncertainty. As the applied NDE techniques change, there arises a need to i
determine the NDE uncertainty. Changes in the applied techniques may involve a change in i
any essential variable which may affect the NDE measurement. Thus, a methodology which may be generically applied to the determination of the NDE measurement uncertainty is j
required. The methodology must define the essential variables relative to NDE measurements, test a sample of steam generator tubes, and recommend a logic for the determination of the i
NDE errorinvolved.
i Essential Variables There ve a number of essential variables which can affect the position, length or inclination i
measurements applied to a flaw. Essential variables which should be considered include:
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Probe Type The probe type being used for a specific measurement can affect the l
error associated with the measurement. A specific coil configuration may have a specific error based upon field spread, presence or lack of shielding or coil spacing.
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Probe Delivery The delivery system consists of the probe pusher, the probe pusher System motor controller and the probe delivery conduit. Variations in the type i
of probe pusher and controller could result in differences in the j
precision and accuracy of the probe speed. The length and type of the conduit may affect the passage of the probe and may lead to some l
variations in speed.
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Direction oftest The direction of the test may affect how probe speed varies in the vicinity of geometric changes such as an expansion transition.
i Probe Speed The probe speed may affect the NDE error where the region ofinterest is near the beginning or end of the test, or where, in the case of rotating probes, the pitch of the test may be affected.
Sampling Rate The sample rate, in conjunction with the maximum probe speed, may affect the NDE uncertainty.
The degree to which some of these contribute to the NDE error may be determined to be negligible. In such a case, this should be documented.
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Attachment Methodology for Determination of NDE Measurement Uncertainty Samples The samples selected for testing should be representative of the types of measurements to be made. These may be simulations with variations in the dimensions to be measured: flaw position, flaw length and /or flaw inclination. The simulations should include the expected prominent features which may affect the NDE accuracy (for example: rolled expansions). If the testing is to verify the NDE uncertainties for a specific alternate repair criteria, such as F*
or L*, the samples should include samples with artificial flaw dimensions which range from
" acceptable" to " repairable". A single sample could be used to obtain multiple measurements.
The use of simulations allows for accurate dimensions to be measured by another means (such as replication) for comparison with the NDE measurements.
Methodolony of Testine Testing of the samples should be performed under conditions which are prototypic of the field.
i The samples will be installed as part of a steam generator mock-up and the probe delivery system (s) used should be of the types used in the generator. The lengths of conduit used between the probe pusher and the tubesheet should cover the range typically used. Testing should be performed at the axial and rotational translation speeds used in the field. The ranges of essential variable for the test shall be documented. Each sample would be tested multiple
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times in order to establish a range of measurements for that sample, j
i The measurements obtained for the population of samples tested would be used to determine the range and average of the NDE uncertainty for each measurement type. Provided a significant number of measurements are made, a confidence band may be established on the J
measurement uncertainty. The measurement uncertainties shall be documented along with the essential test variables. The applicability of the NDE uncertainty shall normally be over the demonstrated range of variables. There may be exceptions to this where a variable can be demonstrated to have negligible effect, or that the change in variable would result in a lesser j
uncertainty. In the case where a variable change would be expected to result in a smaller NDE uncertainty (for example the addition of a probe tensioning device), the larger uncertainty may be applied without any additional qualification.
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