ML13025A080

Relief Request 13-MN-001

ML13025A080
Person / Time
Site:	McGuire
Issue date:	01/09/2013
From:	Capps S Duke Energy Carolinas, Duke Energy Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RR 13-MN-001
Download: ML13025A080 (7)

Text

PkDuke Vice President STEVEN D. CAPPS t Energy, McGuire Nuclear Station Duke Energy MGO1VP /12700 Hagers Ferry Rd.

Huntersville, NC 28078 980-875-4805 980-875-4809 fax Steven. Capps@duke-energy.com January 9, 2013 10 CFR 50.55a U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

SUBJECT:

. Duke Energy Carolinas; LLC (Duke Energy)

McGuire Nuclear Station Unit 1 Docket Number 50-369 Relief Request 13-MN-001 Pursuant to 10 CFR 50.55a(g)(5)(iii), Duke Energy hereby submits Relief Request (RR) 13-MN-001 requesting approval for use of an alternative depth-sizing qualification for volumetric examinations of the reactor vessel hot leg and cold leg nozzle-to-safe end dissimilar metal welds performed from the inside surface.

The basis for the proposed RR for McGuire Unit I is provided in the enclosure to this letter.

Duke Energy requests approval of this RR by March 20, 2013 to support inspections scheduled during the McGuire Unit 1, 2013 spring refueling outage. A similar RR was approved for use at McGuire Unit 2 in an NRC letter dated September 24, 2012.

Ifyou have any questions or require additional information, please contact P. T. Vu at (980) 875-4302.

Sincerely, Steven D. Capps Enclosure www. duke-energy. com

U. S. Nuclear Regulatory Commission January 9, 2013 Page 2 xc:

V. M. McCree, Region II Administrator U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, GA 30303-1257 J. H. Thompson, Project Manager U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 G9A Rockville, MD 20852-2738 J. Zeiler NRC Senior Resident Inspector McGuire Nuclear Station

Enclosure Duke Energy Carolinas, LLC McGuire Nuclear Station, Unit 1 Relief Request Serial No. 13-MN-001 Relief Request for Alternative Depth Sizing Criteria, Submitted Pursuant to 10 CFR 50.55a(g)(5)(iii)

Relief Request 13-MN-001 Page 2 of 5

1.0 ASME Code Components Affected

Class 1 Reactor Coolant System (NC) Reactor Vessel Nozzle-to-Safe End Dissimilar Metal Welds Listed in Table 1 Below.

Table I Description Size Nozzle-to-Safe Inspection Code Case End Weld No. Plan Summary N-770-1 Number Inspection Item Cold Leg Nozzle 1A 27.5" ID (Nom.) 1RPV3-445A-SE M1.G5.3.0005 B to Safe End Weld Cold Leg Nozzle 1B 27.5" ID (Nom.) 1RPV3-445B-SE Ml.G5.3.0006 B to Safe End Weld Cold Leg Nozzle 1C 27.5" ID (Nom.) 1RPV3-445C-SE Ml.G5.3.0007 B to Safe End Weld Cold Leg Nozzle 1D 27.5" ID (Nom.) 1RPV3-445D-SE M1.G5.3.0008 B to Safe End Weld Hot Leg Nozzle 1A 29.0" ID (Nom.) 1RPV3-445E-SE MI.G5.3.0001 A-2 to Safe End Weld Hot Leg Nozzle 1B 29.0" ID (Nom.) 1RPV3-445F-SE M1.G5.3.0002 A-2 to Safe End Weld Hot Leg Nozzle 1C 29.0" ID (Nom.) 1RPV3-445G-SE M1.G5.3.0003 A-2 to Safe End Weld Hot Leg Nozzle 1D 29.0" ID (Nom.) 1RPV3-445H-SE Ml .G5.3.0004 A-2 to Safe End Weld Component materials and nozzle weld configurations are shown in Figure 1.

Relief Request 13-MN-001 Page 3 of 5 End to Nozzle Weld O.D. Cladding (Alloy 82)

Safe End O.D. Cladding (312 SS)

L Nozzle I.D. Cladding (SS)

Safe End I.D. Cladding (312 SS) --/

/--Safe End to Nozzle Weld I.D. Cladding (Alloy 82)

Figure 1 Inlet/Outlet - to - Safe End Welds (Not to Scale) 2.0 ADDlicable Code Edition and Addenda 2.1 ASME Boiler and Pressure Vessel Code, Section Xl, 1998 Edition through the 2000 Addenda.

Note: Use of this Code Edition and Addenda during Period 1 of the 4th Inservice Inspection Interval was authorized via Relief Request Serial #10-MN-001 (ADAMS Accession No. ML110550770). During Periods 2 and 3 of the 4th Inservice Inspection Interval, the applicable Section XI Code of Record shall be determined as specified in this Relief Request.

2.2 ASME Code Case N-770-1, Alternative Examination Requirements and Acceptance Standards for Class 1 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. Use of this Case is required by 10 CFR 50.55a(g)(6)(ii)(F).

2.3 The 4th Inservice Inspection Interval Program for Unit 1 includes ASME Code Case N-695, Qualification Requirements for Dissimilar Metal Piping Welds, Section Xl, Division 1, which has been approved for use in Regulatory Guide 1.147, Rev. 16, Table 1- "Acceptable Section Xl Code Cases".

Relief Request 13-MN-001 Page 4 of 5 3.0 Applicable Code Requirements 3.1 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 RMS error of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.125 in. (3.2 mm)."

Note that volumetric examinations of the Reactor Vessel nozzle-to-safe end dissimilar metal welds are also required to be performed in accordance with Section Xl, Appendix VIII, as required by 10 CFR 50.55a(b)(2)(xv) and 10 CFR 50.55a(b)(2)(xvi).

3.2 Code Case N-695 provides alternatives to the requirements of Appendix VIII, Supplement 10, but paragraph 3.3(c) of this case requires that "Examination procedures, equipment, and personnel are qualified for depth-sizing when the RMS error of the flaw depth measurements, as compared to the true flaw depths, do not exceed 0.125 in. (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.

4.0 Impracticality of Compliance 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 root mean square (RMS) error requirement of ASME Section Xl 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 not been able to meet the applicable RMS error requirement.

5.0 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 (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. Flaw(s) detected and measured as less than 50% through-wall in depth shall be adjusted by adding a correction factor of the RMS Error - 0.125 inches to the depths of any measured flaws.

3. Flaw(s) detected and measured as 50% through-wall depth or greater, and which are to remain in-service without mitigation or repair, shall be adjusted by adding a correction factor of twice the RMS error to the depth of any measured flaw, unless Duke Energy submits the flaw evaluations to the NRC for review and approval prior to reactor startup.

4. If any inner diameter surface-breaking flaws are detected, Duke Energy shall repair the indications or shall perform flaw evaluations and shall submit the evaluations to the NRC for review. These flaw evaluations shall include the following:

Relief Request 13-MN-001 Page 5 of 5

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'.

The proposed alternative is consistent with that previously authorized for McGuire Unit 2 in Relief Request Serial #12-MN-003 (ADAMS Accession No. ML12258A363) and is more conservative than the industry developed alternative documented in Reference 8.6.

All other ASME Code, Section Xl, 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.

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

7.0 Related Industry Relief Requests A similar request was approved for use at McGuire Nuclear Station, Unit 2 in NRC letter dated September 24, 2012 (ADAMS Accession No. ML12258A363).

8.0 References 8.1 1998 Edition through 2000 Addenda, ASME Code, Section Xl, "Rules for Inservice Inspection of Nuclear Power Plant Components."

8.2 1998 Edition through 2000 Addenda, ASME Code, Section Xl, Appendix VIII, Supplement 10.

8.3 ASME Code Case N-695, Qualification Requirements for Dissimilar Metal Piping Welds, Section Xl, Division 1.

8.4 ASME Code Case N-770-1, Alternative Examination Requirements and Acceptance Standards for Class 1 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 Xl, Division 1.

8.5 EPRI Policy/Procedure Directive 03-01: Criteria for Issuing Documentation of Depth Sizing Errors That Exceed the 0.125-inch RMS Appendix Vill Criteria.

8.6 EPRI Materials Reliability Program Letter MRP 2012-046, dated November 26, 2012,

Subject:

Assessment of Effect of the Depth-Sizing Uncertainty for Ultrasonic Examinations from ID Surface of Large-Bore Alloy 82/182 and Austenitic Stainless Steel Butt Welds in PWR Primary System Piping, Revision 1.