ML13086A508

Proposed Relief Request 13-MN-001

ML13086A508
Person / Time
Site:	McGuire, Mcguire
Issue date:	03/28/2013
From:	Robert Pascarelli Plant Licensing Branch II
To:	Capps S Duke Energy Carolinas
Boska J NRR/DORL/LPL2-1 301-415-2901
References
TAC MF0576
Download: ML13086A508 (11)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 28,2013 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 1 - PROPOSED RELIEF REQUEST 13-MN-001 (TAC NO. MFOS76)

Dear Mr. Capps:

By letter dated January 9, 2013, as supplemented by letters dated January 31, 2013, and February 27,2013, Duke Energy Carolinas, LLC (the licensee) submitted a request, RR 13-MN-001, to the Nuclear Regulatory Commission (NRC) for the use of an alternative to certain requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code),Section XI, Appendix VIII, related to inservice inspection (lSI) of welds. RR 13-MN-001 was requested for the remainder of McGuire Nuclear Station, Unit 1 (McGuire 1), fourth 10-year lSI interval. Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Part SO, Section SO.SSa(g)(S)(iii), the licensee requested to use alternatives on the basis that complying with the specified requirement is impractical. Relief Request 13-MN-001 provides an alternative for the depth sizing of ultrasonic examination indications for the reactor coolant system hot leg and cold leg dissimilar metal welds when examined from the inner diameter surface.

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 leak-tightness and structural integrity of the piping and component segments identified in RR 13-MN-001, and that complying with the specified ASME Code,Section XI, Appendix VIII, requirements is impractical. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR SO.SSa(g)(6)(i), and is in compliance with the ASME Code's requirements.

Therefore, pursuant to 10 CFR SO.SSa(g)(6)(i), the NRC staff authorizes the licensee's proposed alternatives as described in RR 13-MN-001 for the duration of the McGuire 1 fourth 10-year lSI interval, currently scheduled to end on November 30, 2021.

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.

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. 50-369

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. 13-MN-001 REGARDING PROPOSED ALTERNATIVE REQUIREMENTS TO ASME CODE CASE N-695 DUKE ENERGY CAROLINAS, LLC MCGUIRE NUCLEAR STATION, UNIT 1 DOCKET NO. 50-369

1.0 INTRODUCTION

By letter dated January 9, 2013 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML13025A080), as supplemented by letters dated January 31, 2013, (ADAMS Accession No. ML13045A485) and February 27,2013, (ADAMS Accession No. ML13072A071), Duke Energy Carolinas, LLC. (Duke Energy, the licensee) submitted relief request (RR) 13-MN-001 to the U.S. Nuclear Regulatory Commission (NRC) staff for review and approval. The supplements dated January 31,2013, and February 27,2013, superseded Duke Energy's letter dated January 9,2013, in its entirety. Specifically, the licensee requested the use of an alternative to certain inservice inspection (lSI) requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code),Section XI, Appendix VIII, ASME Code Case N-695, "Qualification Requirements for Dissimilar Metal Piping Welds." ASME Code Case N-695 identifies depth sizing uncertainty qualification requirements for ultrasonic examinations conducted from the inside diameter (lD) of pipes (i.e., root mean square error (RMSE) not greater than 0.125 inches). The licensee has requested the use of an alternative to the ASME Code requirements pursuant to the regulation at Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section 50.55a(g)(5)(iii) on the basis that the code requirement is impractical. The proposed alternative to the ASME Code is for the remainder of the fourth 10-year lSI interval at McGuire Nuclear Station, Unit 1 (McGuire 1). RR 13-MN-001 provides an alternative for the depth sizing of ultrasonic examination indications for the reactor coolant system hot leg and cold leg dissimilar metal welds when examined from the inner diameter surface.

The ASME Code of record for the fourth 10-year interval lSI program for McGuire 1 is the ASME Code,Section XI, 1998 Edition through the 2000 Addenda. The fourth 10-year interval lSI for McGuire 1 is scheduled to end on November 30, 2021.

Enclosure

- 2

2.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) "must meet the requirements, except design and access provisions and pre service examination requirements, set forth in Section XI of editions and addenda of the ASME [Boiler and Pressure Vessel] B&PV Code... to the extent practical within the limitations of design, geometry, and materials of construction of the components."

The regulation at 10 CFR 50.55a(g)(4)(ii) states, in part, that "inservice examination of components... must comply with the requirements of the latest edition and addenda of the Code incorporated by reference in paragraph (b) of this section [i. e., 10 CFR 55aJ 12 months before the start of the 120-month inspection interval (or the optional ASME Code cases listed in NRC Regulatory Guide [RGJ1.147, Revision 16, when using Section XI... )."

ASME Code Case N-695 is accepted for use in RG 1.147, Revision 16, which, is incorporated by reference in 10 CFR 50.55a(b).

The regulation at 10 CFR 50.55a(g)(5)(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 § 50.4, information to support the determinations.

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 in service 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 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 Description of Relief Request 13-MN-001 3.1.1 ASME Code Components Affected Class 1 Reactor Coolant System Reactor Pressure Vessel (RPV) Nozzle-to-Safe End Dissimilar Metal Welds Listed in the Table Below.

- 3 Description Size Inside diameter (10)

Nozzle-to-Safe End Weld No.

Inspection Plan Summary Number Code Case N-770-1 Inspection Item Cold Leg Nozzle 1A to Safe End Weld 27.5" 10 (Nom.)

1 RPV3-445A-SE M1.G5.3.0005 8

Cold Leg Nozzle 18 to Safe End Weld 27.5" 10 (Nom.)

1 RPV3-4458-SE M1.G5.3.0006 8

Cold Leg Nozzle 1 C to Safe End Weld Cold Leg Nozzle 10 to Safe End Weld Hot Leg Nozzle 1 A to Safe End Weld 27.5" 10 (Nom.)

27.5" 10 (Nom.)

29.0" 10 (Nom.)

1 RPV3-445C-SE 1 RPV3-445D-SE 1 RPV3-445E-SE M1.G5.3.0007 M1.G5.3.0008 M1.G5.3.0001 8

8 A-2

.~

1 Hot Leg Nozzle 1 8 to Safe End Weld 29.0" 10 (Nom.)

1 RPV3-445F-SE M1.G5.3.0002 A-2 Hot Leg Nozzle 1 C to Safe End Weld Hot Leg Nozzle 10 to Safe End Weld 29.0" 10 (Nom.)

1 RPV3-445G-SE 29.0" ID (N~m) !1RPV3-445H-SE j

M1.G5.3.0003 M1.G5.3.0004 A-2 A-2 3.1.2

Applicable Code Edition and Addenda

The Code of Record for the McGuire 1 fourth 10-year lSI interval is the ASME Code,Section XI, 1998 Edition through the 2000 Addenda. The licensee noted that use of this Code Edition and Addenda during Period 1 of the fourth lSI Interval was authorized via RR 10-MN-001 NRC safety evaluation dated March 3, 2011 (ADAMS Accession No. ML110550770).

In supplement to RR 13-MN-001 dated February 27,2012, the licensee clarified that the ASME Section XI Code of Record for periods 2 and 3 of the fourth lSI interval at Unit 1 shall be the same ASME Section XI Code of Record for the fourth lSI interval at Unit 2 (currently scheduled to start on July 15, 2014). The licensee stated that"... Unless 1 0 CFR 50.55a is revised to incorporate by reference a later Code Edition and Addenda sooner than 12 months prior to the

[McGuire] Unit 2 fourth interval start date, the latest ASME Code,Section XI Edition and Addenda incorporated by reference (the 2007 Edition with the 2008 addenda) shall be used for McGuire Unit 1 Periods 2 and 3 of the fourth inservice inspection interval... "

As stated above, the regulation at 1 0 CFR 50.55a(g)(4)(ii) states, in part, that "inservice examination of components... must comply with the requirements of the latest edition and addenda of the Code incorporated by reference in paragraph (b) of this section

[i. e., 10 CFR 55a] 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 licensee plans to submit its fourth lSI interval program for McGuire 2

- 4 at 12 months prior to July 15, 2014. The McGuire 2 fourth lSI interval program submittal will specify the Code of Record for Periods 2 and 3 of the fourth lSI interval at McGuire 1 and the Code of Record for the fourth lSI interval at McGuire 2.

The NRC notes that period 2 of the fourth lSI interval at McGuire 1 is scheduled to start at about the same time as the fourth lSI interval at McGuire 2, i.e., on or about July 15, 2014. The NRC staff finds that the licensee will use the 2007 edition and the 2008 addenda as the Code of Record for periods 2 and 3 of the fourth lSI interval at McGuire 1, unless 10 CFR 50.55a incorporates by reference a later edition and addenda (e.g., the 2009 addenda and 2010 edition) of the ASME Code sooner than 12 months prior to July 15, 2014. The NRC staff finds that the Code of Record for Periods 2 and 3 at McGuire 1 satisfies the requirements contained in 10 CFR 50.55a(g}(4)(ii) and, therefore, is acceptable.

The regulation at 10 CFR 50.55a(g}(6)(ii)(F)(1) requires that "licensees of existing, operating pressurized-water reactors as of July 21, 2011 shall implement the requirements of ASME Code Case N-770-1 ["Alternative Examination Requirements and Acceptance Standards for Class 1 Pressurized Water Reactor (PWR) Piping and Vessel Nozzle Butt Welds Fabricated With UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of listed Mitigation Activities,Section XI, Division 1"], subject to the conditions specified in paragraphs (g)(6)(ii)(F)(2) through (g)(6)(ii)(F)(10 ) of this section, by the first refueling outage after August 22, 2011."

The Fourth lSI Interval Program for McGuire 1 includes use of ASME Code Case N-695, "Qualification Requirements for Dissimilar Metal Piping Welds,Section XI, Division 1," which has been approved for use in RG 1.147, Rev. 16, Table 1, "Acceptable Section XI Code Cases".

3.1.3 Applicable Code Requirements Code Case N-770-1, Table 1, Footnote (4), applies to volumetric examination of Inspection Items A-2 and B, and requires that "Ultrasonic volumetric examination shall be used and shall meet the applicable requirements of Appendix VIII." Appendix VIII, Supplement 10, Paragraph 3.2(b), requires that examination procedures, equipment, and personnel are qualified for depth sizing when the RMSE of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.125 inches (3.2 mm).

The licensee noted that volumetric examinations of the RPV nozzle-to-safe end dissimilar metal welds are also required to be performed in accordance with the ASME Code,Section XI, Appendix VIII, as required by 10 CFR 50.55a(b}(2)(xv) and 10 CFR 50. 55a(b)(2)(xvi). Code Case N-695 provides alternatives to the requirements of Appendix VIII, Supplement 10, but paragraph 3.3(c) of this code case requires that examination procedures, equipment, and personnel are qualified for depth-sizing when the RMSE of the flaw depth measurements, as compared to the true flaw depths, do not exceed 0.125 inches (3 mm). Code Case N-695 has been accepted by the NRC without condition and is listed in Table 1 of Regulatory Guide 1.147, Rev. 16.

- 5 3.1 A

Reason for Request

In section 4.0, "Impracticality of Compliance," of RR 13-MN-001, the licensee stated the following as the reason for its request:

Since 2002, the nuclear power industry has attempted to qualify personnel and procedures for depth-sizing examinations performed from the inside surface of dissimilar metal and austenitic stainless steel butt welds in PWR piping. As of November 26,2012, no domestic or international vendor has met the applicable RMSE requirement of ASME Section X1 Appendix VIII, Supplement 10, or the alternative qualification requirements of ASME Code Case N-695, as applicable.

The examination vendor that Duke Energy intends to use for performing these examinations has an RMSE of 0.189 inch.

3.1.5 Proposed Alternative and Basis for Use In Section 5.0, "Proposed Alternative and Basis for Use," of RR 13-MN-001, the licensee stated the following as the proposed alternative and basis for use:

Duke Energy proposes to use the following alternative for flaw depth sizing when dissimilar metal welds are examined from the inside surface:

1. Examinations shall be performed using ultrasonic testing (UT) techniques that are qualified for flaw detection and length sizing using procedures, personnel and equipment qualified by demonstration in all aspects except depth sizing.

2. A correction factor of the RMSE - 0.125 inches shall be added to the depths of any measured flaws. The correction factor shall be applied to the most critical location on the flaw in relation to surface proximity.

3. Eddy Current examinations shall be used to confirm whether any detected flaws are surface-breaking.

4. If any inner diameter (10) surface-breaking flaws are detected, or if any flaw is detected and measured as 50% through-wall depth or greater, Duke Energy shall repair the indications or shall perform flaw evaluations and shall submit the evaluations to the NRC for review and approval prior to reactor startup.

These flaw evaluations shall include the following:

a. Information concerning the mechanism which caused the flaw.

b. Information concerning the surface roughness/profile in the area of the pipe/weld required to perform the examination, and an estimate of the percentage of potential surface areas with UT probe "lift-off."

- 6 All other ASME Code,Section XI, requirements for which relief was not specifically requested apply, including the third party review by the Authorized Nuclear Inservice Inspector.

Because compliance with the applicable requirements is impractical, this request is submitted pursuant to 10 CFR 50.55a(g)(5)(iii). Duke Energy believes that the proposed alternative provides reasonable assurance that flaws detected during examination will be sufficiently sized to disposition in accordance with acceptance standards of ASME Code Case N-770-1.

3.1.6 Duration of Proposed Alternative In Section 6.0, "Duration of Proposed Alternative," of RR 13-MN-001, the licensee stated the following:

The proposed alternative to the ASME Code is applicable for the remainder of the fourth 10-year Inservice Inspection Interval at McGuire Nuclear Station, Unit 1, which began on December 1,2011 and is currently scheduled to end on November 30, 2021.

3.2

NRC Staff Evaluation

As described above, the licensee has requested relief from the requirements of ASME Code,Section XI, Appendix VIII, Supplement 10, and Code Case N-695. Code Case N-695 requires that procedures used to inspect welds from the inside surface of the pipe be qualified by performance demonstration. The acceptance criterion in Code Case N-695 specifies that the RMSE of the examination procedures shall not be greater than 0.125 inches.

The NRC staff has confirmed that since 2002, the industry has not been able to satisfy the RMSE acceptance criterion of less than 0.125 inches to qualify the UT inspection procedures for flaw depth sizing performed from the inside surface of a pipe. The NRC staff finds that this inability to qualify inside surface UT inspection techniques in accordance with ASME Code Case N-695 constitutes an impracticality as described in 10 CFR 50.55a(g)(5)(iii).

To address the issue of increased potential for under sizing of flaws by inside surface UT inspection procedures which do not meet the ASME Code Case N-695 acceptance criterion, the NRC staff, in July 2012, in conjunction with personnel from the Performance Demonstration Initiative, examined the proprietary UT examination data set compiled from all attempts to date to qualify inside surface UT inspection procedures to the acceptance criterion contained in ASME Code Case N-695. Based on this examination the NRC staff concluded that:

(a) For flaw depths less than 50% pipe wall thickness, a flaw could be appropriately depth sized if a correction factor is added to the measured flaw depth such that the adjusted flaw depth is equal to the measured flaw depth plus the difference between the vendor RMSE and 0.125 inches (procedure qualification RMSE - 0.125).

(b) For flaw depths greater than 50% wall thickness, the variability of sizing errors was sufficiently large that no single mathematic flaw size adjustment formula was

- 7 sufficient to provide reasonable assurance of appropriate flaw depth sizing. As a result, the NRC staff finds it necessary to evaluate the flaws that have depth greater than 50% through wall on a case-by-case basis.

To address the measurement uncertainty in flaw depth sizing when examining welds from the inside surface and to provide reasonable assurance of the structural integrity of examined welds, the NRC staff determines that the following compensatory measures shall be applied to any proposed alternative examination:

(1) Examine the welds under consideration using a UT technique which is qualified for flaw detection and length sizing.

(2) For flaw(s) with measured depth of less than 50% of the wall thickness, the depth shall be adjusted by adding the measured flaw depth to the difference between the procedure qualification RMSE and 0.125 inches (i.e., Procedure RMSE - 0.125).

(3) For flaw(s) with measured depth of greater than 50% of the wall thickness, either the degraded weld needs to be repaired in accordance with the ASME Code, or, a flaw evaluation needs be submitted to the NRC staff for review and approval prior to reactor startup. In addition, the flaw depth analyzed in the flaw evaluation shall also be adjusted by adding the measured flaw depth to the difference between the procedure qualification RMSE and 0.125 inches (i.e., Procedure RMSE - 0.125).

(4) In addition to information normally contained in flaw evaluations in accordance with the ASME Code, Section Xl, IW8-3600, the submitted flaw evaluation shall include:

(a) information concerning the degradation mechanism which caused the crack, (b) information concerning the surface roughness and/or profile in the area of the examined pipe and/or weld, and (c) information concerning areas in which the UT probe may "lift off' from the surface of the pipe and/or weld.

(5) Perform eddy current examination(s) to confirm whether a flaw is connected to the inside surface of the pipe and/or weld, if the flaw is located close to the inside surface of the pipe (e.g., the proximity rule of ASME Code,Section XI, IWA-331 0).

The NRC staff finds that the proposed alternative in RR 13-MN-001 does satisfy the above compensatory measures. Therefore, the NRC staff determines that the proposed alternative to the RMSE acceptance criterion of ASME Code Case N-695 will not significantly challenge the structural integrity or leak tightness of the subject welds.

As noted above, the licensee, in Section 5.0 of RR 13-MN-001, specified that if a subsurface (embedded) flaw is detected, "The correction factor shall be applied to the most critical location on the flaw in relation to surface proximity." The licensee also stated in this section that "Eddy Current examinations shall be used to confirm whether any detected flaws are surface breaking."

The NRC staff finds that the licensee is conservative in adding the correction factor to the embedded crack tip that is closer to the surface. This addition would make the flaw reach the

- 8 surface in less time and, thus, may require the licensee to perform additional examinations such as the eddy current examination which the licensee has committed to perform. Therefore, the NRC staff finds that the licensee's proposed correction factor application and eddy current examination for the embedded flaw are acceptable because these two measures will characterize the embedded flaw appropriately.

In summary, the NRC staff finds that the proposed alternative is acceptable because it is consistent with the NRC staff's position on (1) incorporation of the correction factor into the flaw depth when examining the subject welds from the inside surface of the pipe, and (2) repairing the flaw or submitting a flaw evaluation to the NRC for review and approval prior to reactor startup if any flaw is detected and measured as 50% through-wall depth or greater.

4.0 CONCLUSION

As set forth above, the NRC staff finds that the licensee will follow the NRC staff guidance for compensatory measures when dis positioning flaws detected in the subject welds. The NRC staff determines that granting RR 13-MN-001 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 all of the regulatory requirements set forth in 10 CFR 50.55a(g)(6)(i), and is in compliance with the ASME Code's requirements. Therefore, the NRC staff authorizes the licensee's proposed alternative as described in RR 13-MN-001 for the duration of the McGuire 1 fourth 10-year lSI interval, currently scheduled to end on November 30,2021.

All other ASM E 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: J. Tsao, NRR Date: March 28,2013

S. Capps

-2 If you have any questions, please contact the Project Manager, Jon H. Thompson at 301-415-1119 orvia e-mail at jon.thompson@nrc.gov.

Sincerely, IRN Robert J. Pascarelli, Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-369

Enclosure:

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