ML13010A554

Proposed Relief Request 12-MN-002

ML13010A554
Person / Time
Site:	Mcguire, McGuire
Issue date:	01/14/2013
From:	Robert Pascarelli Plant Licensing Branch II
To:	Capps S Duke Energy Carolinas
Thompson J
References
12-MN-002, TAC ME7877
Download: ML13010A554 (9)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 January 14, 2013 Mr. Steven D. Capps Vice President McGuire Nuclear Station Duke Energy Carolinas, LLC 12700 Hagers Ferry Road Huntersville, NC 28078

SUBJECT:

MCGUIRE NUCLEAR STATION, UNIT 2, PROPOSED RELIEF REQUEST 12-MN-002 (TAC NO. ME7877)

Dear Mr. Capps:

By letter dated January 11, 2012, as supplemented by letters dated April 23, 2012, and December 6,2012, Duke Energy Carolinas, LLC (the licensee) submitted a relief request (RR) 12-MN-002, to the U.S. Nuclear Regulatory Commission (NRC) for review and approval.

The licensee requested relief from certain requirement of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, specifically related to inservice inspection (lSI) examination coverage of welds. RR 12-MN-002 is requested for the third 10-year lSI interval of the McGuire Nuclear Station, Unit 2, (McGuire 2) which commenced on March 1,2004 and will end on July 1S, 2014. Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Section SO.SSa(g)(S)(iii), the licensee has determined that conformance with the ASME Code,Section XI, requirements of examining 100 percent of volume of the piping weld identified in RR 12-MN-002, is impractical.

The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the proposed alternatives for weld lSI would provide reasonable assurance of the leak-tightness and structural integrity of the components identified in RR 12-MN-002, and that complying with the specified ASIVIE Code,Section XI, requirements is impractical. Therefore, pursuant to 10 CFR SO.SSa(g)(6)(i), the NRC staff grants the relief requested in RR 12-MN-002 for the duration of the McGuire 2 third 10-year lSI interval.

All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third party review by the Authorized Nuclear Inservice Inspector.

S. Capps -2 If you have any questions, please contact the Project Manager, Jon H. Thompson at 301-415-1119 or via e-mail at Jon.Thompson@nrc.gov.

Sincerely, Robert J. Pascarelli, Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-370

Enclosure:

Safety Evaluation cc w/encl: Distribution via ListServ

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST NO. 12-MN-002 REGARDING PROPOSED ALTERNATIVE TO WELD EXAMINATION REQUIREMENTS DUKE ENERGY CAROLINAS. LLC MCGUIRE NUCLEAR STATION. UNIT 2 DOCKET NO. SO-370

1.0 INTRODUCTION

By letter dated January 11, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12020A236), as supplemented by letters dated April 23, 2012 (ADAMS Accession No. ML12124A273), and December 6,2012 (ADAMS Accession No. ML 123S9A061), Duke Energy Carolinas, LLC (Duke Energy, the licensee) submitted relief request (RR) 12-MN-002 to the U.S. Nuclear Regulatory Commission (NRC) for review and approval. The licensee requested relief from certain inservice inspection (lSI) requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),

Section XI. Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR)

Section SO.SSa(g)(S)(iii), the licensee has determined that conformance with the ASME Code,Section XI, requirements of examining 100% of volume of the piping weld identified in RR 12-MN-002, is impractical. RR 12-MN-002 is requested for the third 1O-year lSI interval of the McGuire Nuclear Station, Unit 2 (McGuire 2), which commenced on March 1, 2004 and will end on July 1S, 2014.

2.0 REGULATORY EVALUATION

The regulation at 10 CFR SO.SSa(g)(4)(ii) states, in part, that "inservice examination of components ... must comply with the requirements of the latest edition and addenda of the

[ASME] Code incorporated by reference in paragraph (b) of this section [10 CFR SSa] 12 months before the start of the 120-month inspection interval (or the optional ASME Code cases listed in NRC Regulatory Guide [RG]1.147, Revision 16, when using Section XI. .. )."

The regulation at 10 CFR SO.SSa(g)(S)(iii), states that "If the licensee has determined that conformance with a code requirement is impractical for its facility, the licensee shall notify the NRC and submit, as specified in [Section] SO.4, information to support the determinations.

Enclosure

-2 Determinations of impracticality in accordance with this section must be based on the demonstrated limitations experienced when attempting to comply with the code requirements during the inservice inspection interval for which the request is being submitted. Requests for relief made in accordance with this section must be submitted to the NRC no later than 12 months after the expiration of the initial or subsequent 120-month inspection interval for which relief is sought." .

The regulation at 10 CFR 50.55a(g}(6}(i), states that 'The Commission will evaluate determinations under paragraph (g){5) of this section that [ASME] code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility."

Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request and the NRC staff to grant the relief requested by the licensee. .

3.0 TECHNICAL EVALUATION

3.1 ASME Code Components Affected (As stated)

ASME Code Class: Class 2 Examination Category: R-A Item No.: R1.11 Component: Pipe to Pipe Weld System: The Chemical and Volume Control System (NV)

The component for which a relief is requested is listed below.

System / Weld 10 No. Dimensions Component Component (Item/Summary No.) Material Stainless Steel Pipes Pipe to Pipe Weld 2NV2 FW216-60 Nominal Pipe Size (NPS) SA 312ITP304 (M2.R1.11.0276) 2.0 inches Schedule 160 Thickness Weld Material 0.344 inch AWS Class ER308*

The subject weld was included in the McGuire [Nuclear Station], Unit 2, and risk informed (RI) -lSI program. The RI-ISI program was developed in accordance with Topical Report (TR) Westinghouse Owners Group (WOG) WCAP-14572, Rev. 1-NP-A, "WOG Application of Risk Informed Methods to Piping Inservice Inspection Topical Report," and authorized by the NRC dated June 12, 2002, ([ADAMS Accession No.] ML021480421) for the third 1O-year lSI interval.

-3 3.2. Applicable Code Edition and Addenda (As stated)

The code of record for the third 10-year lSI interval at McGuire [Nuclear Station], Unit 2, is the 1998 Edition through 2000 Addenda of the ASME Code,Section XI.

3.3 Applicable Code Requirement (As stated)

The ASME Code,Section XI, IWC-2500, Table IWC-2500-1, Examination Category C-F-1 and C-F-2, requires the lSI examinations (Le., volumetric and surface examination) of the weld during successive 120-month (10-year) intervals. As an alternative, McGuire [Nuclear Station], Unit 2, has adapted the RI-ISI program that was developed based on TR WCAP-14572, Rev. 1-NP-A, methodology, and authorized by the NRC dated June 12,2002. WCAP-14572, Rev. 1-NP-A, Supplement 2, Table 4.1-1, Examination Category R-A, Item No. R1.11, requires volumetric examination of the weld with coverage of 100% of volume C-D-E-F shown in Figure IWC-2500-7(a). As an alternative, McGuire [Nuclear Station], Unit 2, has adapted ASME Code Case N-460, "Alternative Examination Coverage for Class 1 and Class 2 Welds,Section XI, Division 1," for the third 10-year lSI interval. ASME Code Case N-460 allows a reduction in examination coverage on any Class 1 or Class 2 weld provided that the reduction in coverage for that weld is not less than 10% of the 100% coverage (i.e.,

essentially 100%). ASME Code Case N-460 has been accepted by Regulatory Guide (RG) 1.147, Rev. 16.

3.4 Licensee's Discussion of the Impracticality of Compliance (as stated)

The limitations were due to proximity of a permanent welded pipe support that did not allow complete scanning from the pipe side. Scanning requirements are described in 10 CFR 50.55a(b)(2)(xv)(A)(1).

The aggregate coverage was calculated to be 70.625% of the required examination volume. A 70° shear (S)-wave scan obtained 76.5% coverage in one axial direction (Scan 1-pipe). A 70° S-wave scan obtained 53.0% coverage in the other axial direction (Scan 2-pipe). A 45° S-wave scan and a 45° longitudinal (L)-wave scan obtained 76.5%

coverage in clockwise (CW) circumferential direction (Scan 3-CW). A 45° S-wave scan and a 45° L-wave scan obtained 76.5% coverage in counterclockwise (CCW) circumferential direction (Scan 4-CCW).

In order to scan 100% of the ASME Code,Section XI, required volume of this weld, the permanent welded pipe support would have to be redesigned to allow scanning from both sides of the weld, which is impractical. The McGuire [Nuclear Station], Unit 2, lSI program allows the use of ASME Code Case N-460, which required essentially 100%

coverage of examination volume C-D-E-F. ASME Code Case N-460 has been accepted by RG 1.147, Rev. 16. The available coverage will not meet the criteria of this code case.

3.5. Proposed Alternative and Basis for Use (As stated)

No alternative examinations are planned for the weld during current inspection interval.

-4 The radiographic testing (RT) is not a desired option because the RT is limited in the ability to detect potential degradation mechanisms such as thermal fatigue cracking and stress corrosion crack (SCC) initiating at the pipe inside surface. Additionally, RT has not been qualified through performance demonstrations.

3.6 Justification for Grating Relief (As stated)

The ultrasonic testing (UT) of the weld was conducted using personnel, equipment, and procedures qualified in accordance with the ASME Code,Section XI, 1998 Edition through 2000 Addenda.

The system leakage test and the visual (VT-2) examinations in accordance with Table IWC-2500-1, Examination Category C-H, of the ASME Code,Section XI, were performed each inspection period to detect evidence of leakage. This examination provides additional assurance of pressure boundary integrity.

The reactor building normal sump monitoring provides additional assurance that, in the event that leakage did occur through this weld, it would be detected and proper action would be taken.

The weld and associated component have been examined to the maximum extent possible utilizing approved examination techniques and equipment. The combination of acceptable results for the coverage completed by the volumetric examination, the pressure testing and the VT-2 examinations, and the leakage monitoring provides a reasonable assurance of quality and safety.

3.7 Duration of Relief (As stated)

RR 12-MN-002 is applicable for duration of the third 10-year lSI interval which commenced on March 1, 2004 and will end on July 15, 2014.

4.0 NRC STAFF EVALUATION The ASME Code,Section XI, requires examining of 100% of volume, as shown in Figure IWC-2500-7(a) of Class 2 pipe weld. ASME Code Case N-460 allows a reduction in examination coverage on Class 2 welds, provided that the reduction in coverage for that weld is not less than 10% of the 100% coverage (I.e., essentially 100%). ASME Code Case N-460 has been accepted by RG 1.147, Rev. 16. The licensee requested relief from the above requirements on the basis of impracticality, due to limitations (i.e., proximity of a permanent welded pipe support that did not allow complete scanning from the pipe side). The NRC staff determined that the licensee obtained 70.6% coverage of the required examination volume.

The licensee performed the UT from outside diameter surface. The 70.6% coverage represents the aggregate coverage of all scans performed. (Section 3.4 of this safety evaluation describes the scans).

-S The NRC staff has determined that in order to effectively increase the examination coverage, the weld, the associated components, and the adjacent appurtenances would require design modifications. This would place a burden on the licensee. Thus, the NRC staff finds that the examination of essentially 100% of the required volume of the subject weld is impractical.

The ASME Code,Section XI, Appendix I, requires the UT examinations be qualified by performance demonstrations in accordance with Appendix VIII. In addition, the regulation at 10 CFR SO.SSa(b)(2)(xv), "Appendix VIII specimen set and qualification requirements," states provisions for implementation of Appendix VIII. In response to the NRC staff's request for additional information (RAI) dated April 23, 2012, the licensee clarified that the 1998 Edition through 2000 Addenda of the ASME Code,Section XI, Appendix VIII, Supplement 2, "Qualification Requirements for Wrought Austenitic Piping Welds," was used for the UT examinations.

The NRC staff finds that the licensee satisfied the requirements of Appendix I by following Appendix VIII performance demonstrations for the UT and satisfied the requirements of 10 CFR SO.SSa(b)(2)(xv) by using the 1998 Edition through 2000 Addenda of the ASME Code,Section XI, Appendix VIII.

In response to the NRC staff's RAI dated April 23, 2012, the licensee stated that there were no defects found during the Construction Code-required RT examination, pre-service inspection, and subsequent lSI examinations. The NRC staff finds that the licensee sufficiently addressed the examination's history of the subject weld.

The NRC staff recognizes that for each inspection period the licensee has performed the required system leakage test and visual (VT-2) examinations in accordance with the ASME Code,Section XI, Table IWC-2S00-1, Examination Category C-H, to detect evidence of leakage.

In addition to the required examinations, the reactor building normal sump monitoring provides additional assurance that, in the event that leakage did occur through this weld, it would be detected and proper action would be taken.

The NRC staff recognizes that Table 4.1-1, Examination Category R-A, Item No. R1.11, in the TR WCAP-14S72, Rev. 1-NP-A, Supplement 2, classifies the subject weld to be prone to potential degradation by thermal fatigue. The NRC staff issued an RAI question requesting that the licensee discuss any supplemental inspection that has been performed on the volume not examined by UT In response to the NRC staff's RAI dated April 23, 2012, the licensee stated that the pressure test and the visual (VT-2) inspection were performed on the subject weld (Le.

weld 2NV2FW216-60) every 18 months or during the scheduled refueling outage. The last test was completed on April 2, 2011.

The NRC staff finds that the licensee has performed more frequent system leakage test and visual (VT 2) examinations on the subject weld than the ASME Code,Section XI, required each inspection period to provide reasonable assurance of structural integrity or leak tightness of the weld.

The NRC staff notes that when the RI-ISI program is established, the welds shall be selected such that the ASME Code-required examination coverage is achievable. The NRC staff issued an RAI question asking the licensee to discuss whether there were other welds with the same

- 6 risk-significance, subject to the same degradation mechanism, that could be examined and which achieved the required examination coverage. In a response sent by letter dated December 6, 2012, the licensee stated that there are other welds with the same risk significance, subject to the same degradation mechanism that could be examined. The licensee will evaluate the examination coverage for these other welds. A commitment was provided that during the next scheduled refueling outage in Spring 20M, another weld in the RI-ISI program with the same risk-significance and subject to the same degradation mechanism as the weld in this RR will be examined.

The NRC staff finds that the licensee's response is acceptable because the licensee is committed to examine another weld with the same risk-significance and degradation mechanism in an attempt to expand coverage. This may result in achieving essentially 100% coverage, but as a minimum w[l/ increase the total amount of weld examined for this particular degradation mechanism from this additional examination.

In summary, the NRC staff finds that the subject weld has been examined to the maximum extent possible in accordance with the McGuire 2, RI-ISI program utilizing qualified ultrasonic examination procedures, equipment, and personnel in accordance with the ASME Code,Section XI, Appendix VIII. The combination of acceptable results for the coverage completed by the volumetric examinations, the pressure testing, the visual (VT-2) examinations, and the leakage monitoring provide reasonable assurance of structural integrity or leak tightness of the subject weld, the associated components, and the system.

5.0 CONCLUSION

As set forth above, the NRC staff determines that it is impractical for the licensee to comply with the ASME Code,Section XI requirement. The NRC staff also determines that the extent of volumetric examination, in combination with the pressure testing, the visual (VT-2) examinations, and the leakage monitoring, provides reasonable assurance of structural integrity or leak tightness of the subject component. The NRC staff also determines that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Accordingly, the NRC staff concludes that the licensee has adequately addressed a" of the regulatory requirements set forth in 10 CFR 50.55a(g)(6)(i). Therefore, the NRC staff grants the relief requested in RR 12-MN-002 for McGuire 2 for the duration of the McGuire 2 third 1O-year lSI interval, which commenced on March 1, 2004 and will end on July 15,2014.

All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third party review by the Authorized Nuclear In service Inspector.

Principal Contributor: A. Rezai, NRR Date: January 14, 2013

S. Capps - 2 If you have any questions, please contact the Project Manager, Jon H. Thompson at 301-415-1119 or via e-mail at Jon.Thompson@nrc.gov.

Sincerely, IRA!

Robert J. Pascarelli, Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-370

Enclosure:

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