NL-12-0498, Response to NRC RAI Dated February 23, 2012 Regarding Proposed Relief Request FNP-ISI-RR-01

Response to NRC RAI Dated February 23, 2012 Regarding Proposed Relief Request FNP-ISI-RR-01

ML12072A233
Person / Time
Site:	Farley
Issue date:	03/09/2012
From:	Ajluni M Southern Nuclear Operating Co, Southern Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-12-0498
Download: ML12072A233 (8)

Text

Mark J. Ajiuni, P.E. Southern Nuclear Nuclear Licensing Director Operating Company, Inc.

40 Inverness Center Parkway Post Office Box 1295 Birmingham, Alabama 35201 Tel 205.992.7673 Fax 205.992.7885 March 9, 2012 SOUTHERN COMPANY Docket Nos.: 50-348 NL-12-0498 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Joseph M. Farley Nuclear Plant - Unit 1 Response to NRC RAI Dated February 23, 2012 Reqarding Proposed Relief Request FNP-ISI-RR-01 Ladies and Gentlemen:

By letter dated March 28, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML110871951), Southern Nuclear Operating Company (SNC) submitted a request for relief for Joseph M. Farley Nuclear Plant, Unit 1, that would allow the use of an alternate depth-sizing qualification for volumetric examinations of the reactor pressure vessel nozzle-to-safe end dissimilar metal welds from the inside surface. The U.S. Nuclear Regulatory Commission staff (NRC) issued a Request for Additional Information (RAI) by letter dated July 14, 2011 (ADAMS Accession No. ML11173A047), and SNC responded by letter dated August 11, 2011 (ADAMS Accession No. ML112232241). The NRC considered this issue further and found that additional information is needed to continue the review of this relief request. A second RAI was sent to SNC in letter dated February 23, 2012 (ADAMS Accession No. ML12048B330). The SNC responses to the second RAI are provided in the Enclosure.

The NRC commitments contained in this letter are provided as a table in . If you have any questions, please contact Jack Stringfellow at (205) 992-7037.

Sincerely, M. J. Ajluni Nuclear Licensing Director MJA/RMJ ALI -7

U. S. Nuclear Regulatory Commission NL-12-0498 Page 2

Enclosures:

1. Response to NRC RAI Dated February 23, 2012 Regarding Proposed Relief Request FNP-ISI-RR-01

2. List of Regulatory Commitments cc: Southern Nuclear Operatingq Company Mr. S. E. Kuczynski, Chairman, President & CEO Mr. D. G. Bost, Executive Vice President & Chief Nuclear Officer Mr. T. A. Lynch, Vice President - Farley Mr. B. L. Ivey, Vice President - Regulatory Affairs Mr. B. J. Adams, Vice President - Fleet Operations RTYPE: CFA04.054 U. S. Nuclear Regulatory Commission Mr. V. M. McCree, Regional Administrator Mr. R. E. Martin, NRR Project Manager - Farley Mr. E. L. Crowe, Senior Resident Inspector - Farley

Joseph M. Farley Nuclear Plant - Unit 1 Response to NRC RAI Dated February 23, 2012 Regarding Proposed Relief Request FNP-ISI-RR-01 Enclosure I Response to NRC RAI Dated February 23, 2012 Regarding Proposed Relief Request FNP-ISI-RR-01

Enclosure to NL-12-0498 Response to NRC RAI Dated February 23, 2012 Regarding Proposed Relief Request FNP-ISI-RR-01 NRC Position related to RMS Error Adjustment:

If twice the RMS error is not to be added to the depth of the measured flaw, the NRC staff requests that the licensee commit in their RAI response that flaw evaluations of any flaws found in the inspections covered by this relief request, FNP-ISI-RR-01 be submitted to the NRC for review and approval prior to reactor startup. When submitting the evaluation, in addition to the typical information provided in a flaw evaluation, the following additional information (described below) will need to be included.

SNC Response to NRC Position related to RMS Error Adiustment:

Southern Nuclear Operating Company (SNC) does not intend to use the staff proposed root mean square (RMS) error adjustment. SNC believes that the proposed adjustment is overly conservative. The RMS error adjustment requested in FNP-ISI-RR-01, when combined with the margins required for evaluating flaws, provides reasonable assurance of the continued structural integrity of the subject welds. SNC understands that an industry assessment regarding this issue is forthcoming and has reviewed the statistical results. While these results support the basis for the requested RMS error adjustment proposed in FNP-ISI-RR-01, the staff has not approved the assessment at this time. In lieu of using the staff proposed RMS error adjustment, SNC commits that flaw evaluations of any flaw found in the inspections covered by relief request FNP-ISI-01 will be submitted to the NRC for review and approval prior to Unit 1 Cycle 25 reactor startup, except as noted in the following responses.

NRC Additional Information Request No. I related to Measured Flaw Size:

The measured flaw size(s).

SNC Response to NRC Request No. 1 for Measured Flaw Size:

If flaws are found, the measured flaw size, as determined by Ultrasonic Testing (UT), will be included in the evaluation.

NRC Additional Information Request No. 2 related to RMS Error Adjustment Details:

The RMS error that was added to the measured flaw size and how the RMS error was established. The RMS depth-sizing error for the personnel conducting the examination. The licensee may propose a smaller addition (less than twice the RMS error) to the flaw depth. A smaller addition to the flaw depth will need to be technically justified, which should include, as a minimum, a demonstration that the welds are easier to inspect than the Performance Demonstration Initiative Supplement 10 ID specimens (e.g. no probe lift-off, less than 1/32 inch surface waviness) in the area near the flaw and the area used for depth-sizing. Smooth ID surfaces and other factors will be taken into account by NRC staff when reviewing the flaw evaluation.

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Enclosure to NL-12-0498 Response to NRC RAI Dated February 23, 2012 Regarding Proposed Relief Request FNP-ISI-RR-01 SNC Response to NRC Request No. 2 related to Proposed RMS Error Adjustment:

The obtained procedure RMS sizing error provided in this relief request is a more appropriate value to use for an evaluation of a flaw through-wall measurement. Providing the RMS value for a single analyst does not provide additional assurance on the accuracy of the measurement.

Each analyst, while not qualified in accordance with Supplement 10, has demonstrated a capability of sizing to the same secondary acceptance criteria that is used to judge the procedure's performance. Additionally, the data obtained to provide a through-wall depth measurement of reported flaws in the field is encoded and stored digitally. The data is essentially portable and can be sent easily to various analysts for concurrent flaw through-wall measurement evaluation. Subsequently, the reported size of a flaw is not determined by a single analyst; the data is reviewed by several analysts and potentially outside consultants prior to supplying a final through-wall measurement determination used in the flaw analysis.

In addition, the individual depth sizing error performance is not provided to the utility or the vendor by the administrator of the qualification program. What is provided is the RMS error for the procedure and a list of candidates who have met or exceeded the procedure's RMS error performance value. It is SNC's understanding that the individual performance information could be made available to the staff directly via the EPRI Performance Demonstration Initiative (PDI) administrator, provided confidentiality controls are maintained; however, it is not in the best interest of the industry to have the individual results disclosed to a utility, its vendor, or the public, as it could compromise the integrity of the qualification program.

In order to provide additional comparative information of the Joseph M. Farley Nuclear Plant (FNP) dissimilar metal welds (DMWs) to be examined to the mockup welds, under which the Supplement 10 qualification is conducted, the following was obtained from the PDI administrator:

Procedures and personnel are qualified on realistic mock-ups that contain both field weld and shop weld configurations. The shop weld configurations contain an 82/182 dissimilar metal weld (Supplement 10) connecting a stainless steel-clad ferritic nozzle forging to a stainless steel safe-end, which is then joined using austenitic metal material to either a wrought austenitic pipe or a cast austenitic elbow (Supplement 2 weld). The field weld configurations do not have safe-ends and connect the stainless steel-clad nozzle forging directly to either a wrought austenitic pipe or a cast austenitic elbow (Supplement 10 weld) using 82/182 weld material. The Supplement 2 and Supplement 10 field welds contain the most aggressive geometry and are considered the most challenging; however the location of these welds with relation to the relativity smooth shop weld also provide challenges to the techniques. There are a total of six welds included in the PDI qualifications. Four of these welds are field welds (two dissimilar metal welds and two Supplement 2 welds) with similar geometric conditions and two dissimilar metal weld shop welds, one with a relatively long safe-end and the other with short safe-end that brings the geometry from the field weld into the scan area.

Since the majority of the sample set is comprised of flaws that are contained in field weld configurations that have similar material and geometric conditions the grading approach currently defined in the 2008 Addenda of Appendix VIII, CC-696 and the PDI qualification program continues to be technically appropriate. Separating Supplement 2 measurements from the measurements made on similar weld configuration using the exact same E1-2

Enclosure to NL-12-0498 Response to NRC RAI Dated February 23, 2012 Regarding Proposed Relief Request FNP-ISI-RR-01 techniques makes the evaluation more granular and reduces the overall confidence in the capabilities of the technique.

Given that one-third of the six total Supplement 2 and 10 PDI qualification welds and one-half of the four total Supplement 10 PDI qualification welds are comparable to the FNP configuration, it is reasonable to conclude that sizing flaws in the DMWs for which this relief request was submitted are less challenging than sizing flaws in the combinations of geometries demonstrated in the PDI mockups.

In summary, SNC believes that the proposed adjustment to the depth size measurement can be technically justified for the range of conceivable flaws.

NRC Additional Information Request No. 3 related to Eddy Current Testing:

Ifthe procedure uses eddy current, the determination by eddy current ifthe flaw is or is not surface breaking.

SNC Response to NRC Request No. 3 related to Eddy Current Testing:

SNC will perform the required evaluations to determine if the flaw(s) are surface breaking or not.

In the case of the examinations planned for spring 2012, the contracted examination vendor will deploy eddy current in order to make these determinations.

NRC Additional Information Request No. 4 related to Inner Diameter Profile of the Examination Area:

The inner diameter profile of the weld, pipe, nozzle, and safe end (as applicable) in the region at and surrounding the transducer locations used to depth size the flaw.

SNC Response to NRC Request No. 4 related to Inner Diameter Profile of the Examination Area:

If a flaw is detected and depth sizing is required, this information will be collected and provided with the evaluation.

NRC Additional Information Request No. 5 related to the Flaw Degradation Mechanism:

The suspected flaw degradation mechanism and the process used to determine the degradation mechanism.

SNC Response to NRC Request No. 5 related to the Flaw Degradation Mechanism:

The initial nondestructive examination (NDE) data coupled with additional data collected will be used to aid in this determination and will be provided.

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Joseph M. Farley Nuclear Plant - Unit I Response to NRC RAI Dated February 23, 2012 Regarding Proposed Relief Request FNP-ISI-RR-01 Enclosure 2 List of Regulatory Commitments

List of Regulatory Commitments The following table identifies those actions committed by Southern Nuclear Operating Company in this document for Farley Nuclear Plant. Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments.

Commitment Due Date / Event SNC commits that flaw evaluations of detected flaws Prior to Unit 1 determined to be connected to the piping inner diameter Cycle 25 reactor surface during the examinations covered by relief request FNP- startup ISI-01 will be submitted to the NRC for review and approval, except as described in NL-12-0498.

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