ML070310367

Relief Request 07-GO-001

ML070310367
Person / Time
Site:	Catawba, McGuire
Issue date:	01/24/2007
From:	Rosalyn Jones Duke Energy Carolinas, Duke Energy Corp, Duke Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML070310367 (35)

Text

RONALD A. JONES SVP, Nuclear Operations PoTEnergyo Nuclear Generation Duke Energy Corporation 526 South Church St.

Charlotte, NC 28202 Mailing Address:

EC07H / PO Box 1006 Charlotte, NC 28201-1006 704 382 8149 704 382 6056 fax January 24, 2007 rajones@duke-energy.com U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Duke Power Company LLC d/b/a Duke Energy Carolinas, LLC (Duke)

McGuire Nuclear Station, Unit 1 Docket Number 50-369 Catawba Nuclear Station, Unit 2 Docket Number 50-414 Relief Request 07-GO-001 Pursuant to 10 CFR 50.55a(a)(3)(i), Duke hereby requests NRC approval to use alternatives to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI inservice inspection (ISI) requirements for McGuire Unit 1 and Catawba Unit 2. This proposed alternative approach is to support application of full structural weld overlays on various pressurizer nozzle-to-safe end welds and will provide an acceptable level of quality and safety.

Relief Request 06-GO-001 (a similar relief request), was submitted for all four McGuire and Catawba Units on July 27, 2006. Duke provided additional information to the NRC Staff on September 11, 2006 and September 27, 2006.

The September 27, 2006 submittal of Relief Request 06-GO-001 incorporated the requests for additional information and withdrew the portions of relief request related to McGuire Unit 1 and Catawba Unit 2 per the NRC's request.

Further clarification to the relief request was provided on November 16, 2006.

Duke received verbal approval from the NRC staff on September 28, 2006 for McGuire Unit 2 and on December 18, 2006 for Catawba Unit 1. Since there is still no standard industry approach for this type of relief request, Duke made the decision to proceed using the same approach that was successful for the McGuire and Catawba fall 2006 outages. This relief request reflects the same www. duke-energy. com

U. S. Nuclear Regulatory Commission January 24, 2007 Page 2 information submitted for Relief Request 06-GO-001, with changes made to reflect the applicable units.

This request is needed to support work during the following outages: McGuire Unit 1

- spring 2007 and Catawba Unit 2 - fall 2007.

The installation of the weld overlays will be conducted in accordance with the 1998 Edition through 2000 Addenda of ASME Code,Section XI, IWA-4000 and ASME approved Code Cases N-504-2 and N-638-1 with modifications as described in this request. These Code Cases are listed as conditionally acceptable for use in NRC Regulatory Guide 1.147, Revision 14. Additionally, Duke is required to implement Appendix VIII of the ASME Code,Section XI, 1998 Edition with the 2000 Addenda, which contains ultrasonic examination performance qualification requirements under Supplement 11 for a completed full structural weld overlay repair. In lieu of these ASME Code ultrasonic qualification requirements, Duke proposes to use the alternative qualification as administered by the Performance Demonstration Initiative (PDI) for the qualification of the ultrasonic examination of the full structural weld overlay repair, and the examination of the dissimilar metal welds. Use of the proposed alternative is based on the PDI approved techniques and procedures also described in this request. The detailed relief request is provided as Enclosure 1 to this letter. It contains a comprehensive set of criteria that outline the proposed McGuire Unit 1 and Catawba Unit 2 full structural weld overlays. The relief request provides alternatives and modifications to the ASME Code requirements and Code Cases N-504-2 and N-638-1 that Duke has determined will be necessary to perform this repair.

Duke requests approval of this relief request to support the McGuire Unit 1 spring 2007 and Catawba Unit 2 fall 2007 refueling outages. Approval is needed prior to March 10, 2007 to support the repair at McGuire.

This relief request contains the following regulatory commitments.

1. Prior to entry into Mode 4 from the McGuire Unit 1 spring 2007 refueling outage, a summary of the results of the stress analyses demonstrating that the preemptive full structural weld overlay will not hinder the components from performing their design function will be submitted to the NRC.

2. Prior to entry into Mode 4 from the Catawba Unit 2 fall 2007 refueling outage, a summary of the results of the stress analyses demonstrating that the preemptive full structural weld overlay will not hinder the components from performing their design function will be submitted to the NRC.

U. S. Nuclear Regulatory Commission January 24, 2007 Page 3

3. The following information will be submitted to the NRC within fourteen days of completion of the final UT on each unit included in this relief request. Also included in the results will be a discussion of any repairs to the overlay material and/or base metal and the reason for the repair.

• a listing of flaw indications detected

• the disposition of all indications using the standards of ASME Section XI, IWB-3514-2 and/or IWB-3514-3 criteria and, if possible,

• the type and nature of the indications If you have any questions or require additional information, please contact Mary Shiple at (704) 382-5880.

Si er ly, R aid A. Jones Enclosures

U. S. Nuclear Regulatory Commission January 24, 2007 Page 4 xc:

W. D. Travers, Region II Administrator U.S. Nuclear Regulatory Commission Sam Nunn Atlanta Federal Center, 23 T85 61 Forsyth St., SW Atlanta, GA 30303-8931 J. F. Stang, Jr., Senior Project Manager (CNS & MNS)

U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 H 4A Rockville, MD 20852-2738 J. B. Brady NRC Senior Resident Inspector McGuire Nuclear Station A. T. Sabisch NRC Senior Resident Inspector Catawba Nuclear Station

U. S. Nuclear Regulatory Commission January 24, 2007 Page 5 bxc:

R. L. Gill (ECO50)

C. J. Thomas (MG01 RC)

K. L. Crane (MG01 RC)

R. D. Hart (CN01RC)

L. J. Rudy (CN01RC)

J. M. Ferguson (CN01VP)

K. E. Nicholson (CN01 RC)

M. R. Hatley (MG05SE)

H. V. Dinh (MG05SE)

M. D. Hunt (MG05SE)

P. T. Vu (MG01RC)

M. A. Pyne (EC07C)

Ricky Branch (MG01 MM)

G. J. Underwood (EC05A)

D. H. Llewellyn (EC07C)

C. R. Frye (EC07C)

J. M. Shuping (EC07C)

W. 0. Callaway (CN03SE)

J. F. Bumgarner (CN03SE)

A. J. Hogge, Jr. (EC05A)

J. J. McArdle (EC05A)

R. K. Rhyne (EC05A)

T. B. Mc Curry (EC07C)

R. N. McGill (CN03PS)

J. F. Swan (MG01 MM)

North Carolina Municipal Power Agency Number 1 Saluda River Electric Cooperative, Inc.

Piedmont Municipal Power Agency North Carolina Electric Membership Corporation MNS MasterFile MC-801.01 (MG01 DM)

CNS MasterFile CN-801.01 (CN04DM)

ONS MasterFile ON-801.01 (ON03DM)

ELL

Request No. 07-GO-001 Enclosure 1 ProposedAlternative In Accordance with 10 CFR 50.55a(a)(3)(i)

- Alternative Provides Acceptable Level of Quality and Safety -

Duke Energy Corporation McGuire Nuclear Station Unit 1 and Catawba Nuclear Station Unit 2 Request for Alternative 07-GO-001 CONTENTS 1.0 ASME CODE COMPONENTS AFFECTED .................................................................... 3 2.0 APPLICABLE CODE EDITION AND ADDENDA ......................................................... 5 3.0 APPLICABLE CODE REQUIREMENTS ........................................................................ 5 4.0 REASON FOR THE REQUEST ........................................................................................ 6 5.0 PROPOSED ALTERNATIVES AND BASIS FOR USE ................................................. 7 6.0 WELD OVERLAY DESIGN AND VERIFICATION .................................................... 32 7.0 DURATION OF THE PROPOSED ALTERNATIVES ................................................. 34 8.0 P RE C ED E N TS ........................................................................................................................ 35 9.0 RE F ERE N C ES ........................................................................................................................ 36 10.0 CO N CL U SIO N ........................................................................................................................ 38 A T TA C HM EN T 1 ......................................................................................................................................... 39 Figure Al Pressurizer Nozzle Weld Overlay (Typical) ........................................................................ 40 Table Al Modifications To Code Case N-504-2 and Corresponding Non-Mandatory Appendix Q R equ irem ents ............................................................................................................................ 41 Table A2 Alternatives to Appendix VIII, Supplement 11 ................................................................. 45 Table A3 M odifications to Code Case N-638-1 ................................................................................... 60 List of Figures Figure 5.1 Residual Stress Distribution from ASME White Paper (see Text) .......................................... 20 Figure 5.2 Calculated Residual Stress Distribution for McGuire and Catawba (see Text) ........................ 22 Figure 5.3 Phased array UT coverage for MNS/CNS Pressurizer Safety & Relief Nozzles ...................... 27 Figure 5.4 Phased array UT coverage for MNS/CNS Pressurizer Spray Nozzles ...................................... 29 Figure 5.5 Phased array UT coverage for MNS/CNS Pressurizer Surge Nozzles ...................................... 31 Page 1 of 30

Request No. 07-GO-001 Enclosure 1 1.0 ASME CODE COMPONENTS AFFECTED System: Reactor Coolant System Component Number:

rICn6U11LZL 3UIC iJLL*C ,iL)Nusmt c1IU LAS IIle/AIUIUllUy O8L-108 Weld/SS safe enIIU Pressurizer Spray nozzle to safe end 6"OD I PZR-W2SE LAS nozzle/Alloy 82-182 weld/SS safe end Pressurizer Relief nozzle to safe end 8" OD t1PZR-W3SE LAS nozzle/Alloy 82-182 weld/SS safe end IPressurizer Safety nozzle to safe end 8" OD 1PZR-W4ASE LAS nozzle/Alloy 82-182 weld/SS safe end Pressurizer Safety nozzle to safe end 9" OD IPZR-W4BSE LAS nozzle/Alloy 82-182 weld/SS safe end

[Pressuri RC Pipe zer Safety nozzle to safe end Surge safe end to pipe 8" OD 1PZR-W4CSE 114" Sch 1601NC1F3612 ILAS nozzle/Alloy 82-182 weld/SS safe end SS safe end/SS weld/SS pipe

[RC Pipe Spray safe endto Pipe 4" Sch 160 NC1F1746 SS safe end/SS weld/SS pipe IRC Pipe Relief safe end to Pipe 6" Sch 160 NC1F546 SS safe end/SS weld/SS pipe Safety safe end to Pipe 6"-SchI60 iNCiF542 SS safe end/SS weld/SS pipe IRC RC Pipe Pipe Safety safe end to Pipe 16"Sch160 -NC-F544 SS safe end/SS weld/SS pipe__

RC Pipe Safety safe end to Pipe 6"Sch-I60 NCIF1850 SS safe end/SS weld/SS pipe Catawba 1)ecript -n Pressurizer Surge nozzle to safe end 15" OD Size Weld Numnber 2PZR-W1SE Comment LAS nozzle/Alloy 82-182 weld/SS safe end Pressunizer Sprge nozzle to safe end 15" OD 2PZR-WSE LAS nozzle/Alloy 82-182 weld/SS safe end Pressurizer Spray nozzle to safe end 6" OD 2PZR-W2SE LAS nozzle/Alloy 82-182 weld/SS safe end Pressurizer Relief nozzle to safe end 8" OD 2PZR-W4CSE LAS nozzle/Alloy 82-182 weld/SS safe end Pressurizer Safety nozzle to safe end 8" OD 2PZR-W4ASE LAS nozzle/Alloy 82-182 weld/SS safe end Pressurizer Safety nozzle to safe end 8" OD 2PZR-W4BSE LAS nozzle/Alloy 82-182 weld/SS safe end Pressurizer Safety nozzle to safe end 8" OD 2PZR-W3SE LAS nozzle/Alloy 82-182 weld/SS safe end 14" Sch 160t2NC8-3SSsf en/S w dSSp e RCPipe Surge safe end to pipe RC Pipe Spray safe end to Pipe 4"Sch 160 ]2NC44-28 SS safe end/SS weld/SS pipe RC Pipe Relief safe end to Pipe 6" Sch 160 2NC1 17-7 SS safe end/SS weld/SS pipe RC Pipe Safety safe end to Pipe 6" Sch 160 12NC 119-1 SS safe end/SS weld/SS pipe RC Pipe Safety safe end to Pipe 6" Sch 160 2NC163-1 SS safe end/SS weld/SS pipe 6 1 2-4 -5 rRC Pipe Safety safe end to Pipe 6" Sch 160 i2NC 112-5 SS safe end/SS weld/SS pipe (1) LAS = SA-508Class 2 Grade 2 low alloy steel.

SS safe end = Type 316 austenitic stainless steel SS pipe = Type 304 austenitic stainless steel Page 2 of 30

Request No. 07-GO-001 Enclosure 1 Code Class: Class 1 Examination Category: McGuire - R-A (Risk- Informed)

Catawba - B-F; B-J Code Item Number: McGuire - R01.011 Catawba - B5.40; B9.11 2.0 APPLICABLE CODE EDITION AND ADDENDA Inservice Inspection:

ASME Boiler and Pressure Vessel Code,Section XI, 1998 Edition through 2000 Addenda -

McGuire Unit 1 & Catawba Unit 2 Design and Fabrication-ASME Boiler and Pressure Vessel Code,Section III, 1971 Edition through Winter 1971 Addenda

- McGuire Unit 1 ASME Boiler and Pressure Vessel Code,Section III, 1974 Edition through Summer 1974 Addenda - Catawba Unit 2 Duke Welding Program:

ASME Boiler and Pressure Vessel Code,Section III, 1989 Edition No Addenda - All units at all sites 3.0 APPLICABLE CODE REQUIREMENTS ASME Boiler and Pressure Vessel Code,Section XI, 1998 Edition through 2000 Addenda, Article IWA-4000, "Repair/Replacement Activities" ASME Boiler and Pressure Vessel Code,Section XI, 1998 Edition through 2000 Addenda, Appendix VIII, Supplement 11, "Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds" Code Case N-504-2 with requirements of ASME Code,Section XI, Nonmandatory Appendix Q, "Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments" Code Case N-638-1, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique" 4.0 REASON FOR THE REQUEST Dissimilar metal welds (DMW) made with nickel alloys 82 and 182 have been shown to be susceptible to primary water stress corrosion cracking (PWSCC) degradation in components such as the pressurizer that are subjected to higher operating temperatures. Structural weld overlays have been used for several years Page 3 of 30

Request No. 07-GO-001 Enclosure 1 on piping of both boiling water reactors and pressurized water reactors to arrest the growth of existing flaws while establishing a new structural pressure boundary. No evidence of PWSCC has been found in the welds of the McGuire or Catawba pressurizer; however, PWSCC is difficult to detect in DMW except when the inspection is performed in accordance with the stringent requirements of ASME Section XI, Appendix VIII. The DMW included in this request for relief have been evaluated and found not to meet the surface or geometric requirements of Appendix VIII. The feasibility of modifying the geometry to an acceptable configuration has not been established. Duke is proposing to take a proactive approach to apply a preemptive full structural weld overlay (PWOL) to the dissimilar metal welds of the pressurizer components listed in Section 1.0 of this request.

Currently, there are no comprehensive criteria for a licensee to apply a full structural weld overlay to DMW constructed of Alloy 82/182 weld material. Neither the latest NRC approved edition nor the edition of ASME Section XI used for the McGuire and Catawba Units 1 & 2 repair/replacement program, contains the needed requirements for this type of repair. Repair/replacement activities associated with a full structural weld overlay repair of this type are required to address the materials, welding parameters, ALARA concerns, operational constraints, examination techniques, and procedure requirements. Similar nozzle-to-safe end weld overlays have been applied to other plants since 1986 with no problems identified.

5.0 PROPOSED ALTERNATIVES AND BASIS FOR USE Pursuant to 10CFR 50.55a(a)(3)(i), an alternative to the requirements listed in Section 3.0 above is requested on the basis that the proposed alternative will provide an acceptable level of quality and safety. , Tables Al, A2, and A3, included as a part of this request for relief, provides details of relief requested from each of these requirements.

A full structural PWOL is proposed for each of the pressurizer welds identified in Section 1.0 above. The overlays will extend around the full circumference of the nozzle-to-safe end and safe end to piping welds, as illustrated in Figure Al in Attachment 1. The stainless steel weld connecting the pipe to the safe end is included due to the close proximity to the dissimilar metal weld and the need to provide a length of overlay adequate to assure that adequate volumetric coverage for non-destructive examination will be obtained. All the stainless steel safe end to RCS piping welds were made with filler material conforming to AWS class E308 or ER308 for chemistry as required by ASME Section III, subsection NB-2000. The full structural weld overlays are sized to satisfy tho ASME Code,Section III requirements without crediting the existing welds.

The proposed weld overlay design is consistent with the requirements of ASME Code Case N-504-2 and Section XI, Nonmandatory Appendix Q with the modifications noted in Table Al in Attachment 1. The provisions of Appendix Q must be met as a condition of acceptance of the Code Case by NRC Regulatory Guide 1.147, Revision 14. The specific thickness and length are computed according to the guidance provided in Code Case N-504-2 and Appendix Q. The overlay will completely cover the Alloy 82/182 and adjacent stainless steel welds with alloy 52M/52MS material that is highly resistant to PWSCC.

The length of the full structural weld overlay is sized for inspection of the volume shown in Appendix Q, Fig Q-4300-1. This volume extends '1/2-inchbeyond the susceptible weld and includes the outer 25% of Page 4 of 30

Request No. 07-GO-001 Enclosure 1 the original wall thickness. The length of the PWOL is extended and blended into the low alloy steel nozzle outer diameter taper to permit ultrasonic testing (UT) of the weld and to minimize stress concentration on the nozzle outer diameter. The outside diameter of the nozzle is larger than that of the adjacent component; therefore, the PWOL thickness on the component is increased to allow a smooth transition surface for UT. The final structural weld overlay length and thickness after taking into consideration the UT requirements will exceed the length required for a full structural weld overlay repair in accordance with Case N-504-2 and Appendix Q.

Appendix Q, Section 4000 requires ultrasonic procedures and personnel to be qualified in accordance with ASME Code,Section XI, Appendix VIII. Ultrasonic examination of the completed PWOL will be accomplished in accordance with Section XI, Appendix VIII, Supplement 11, with alternatives to comply with the Performance Demonstration Initiative (PDI) program as shown in Table A2 in Attachment 1.

Implementation of Section XI, Subsection, IWA-4540(a)(2) for a system leakage test requires performance of NDE in accordance with the methods and acceptance criteria of the applicable Subsection of the 1992 or later Edition of ASME Section III. These requirements were formerly included in Code Case N-416-2 that is not listed within the current ISI Program Plan for McGuire and Catawba. The requirements of Code Case N-416-2 were incorporated into Section XI and are implemented in ASME Boiler and Pressure Vessel Code Section XI 1998 Edition through 2000 Addenda applicable to the third inspection interval for each of the units for which relief is requested. As an alternative to the Section XI NDE requirements, Duke will follow the NDE requirements of Appendix Q for the required NDE. The bases for these alternatives are shown as needed in Table Al in Attachment 1.

The PWOL will be applied over portions of the low alloy steel (LAS) nozzles. The Construction Code requires post-weld heat treatment after welding. As an alternative to post-weld heat treatment, the overlay will be implemented in accordance with Code Case N-638-1 with the modifications noted in Table A3 in Attachment 1. Code Case N-638.-1 was conditionally approved for generic use in NRC Regulatory Guide 1.147, Revision 14, and was developed for welding similar and dissimilar metals using the ambient temperature machine GTAW temper bead technique. This Code Case specifies a limit of 100 square inches for the surface area of temper bead weld over the ferritic material. The weld surface areas over ferritic material for the subject weld overlays are expected to be approximately 120 square inches, 55 square inches, and 33 square inches, for the surge line nozzles, safety and relief line nozzles, and spray line nozzles, respectively.

An ASME white paper describes the technical justification for allowing increased overlay areas up to 500 square inches. This white paper was also submitted to the NRC as a part of a relief request by Constellation Energy Generation Group (Adams Accession Number, ML060240110). The white paper indicates the original limit of 100 square inches in Code Case N-638-1 was an arbitrary limit and goes on to justify the application of overlays up to 500 square inches on ferritic low alloy steel. The white paper cites evaluations of a 12 inch diameter nozzle weld overlay to demonstrate adequate tempering of the weld heat affected zone (Section 2a of the white paper), residual stress evaluations demonstrating acceptable residual stresses in weld overlays ranging from 100 to 500 square inches (Section 2b of the white paper), and service history in which weld repairs exceeding 100 square inches were NRC approved and applied to DMW nozzles in several BWRs and three PWRs (Section 3c of the white paper). Some of the cited repairs are greater than 15 years old, and have been inspected several times with no evidence of Page 5 of 30

Request No. 07-GO-001 Enclosure 1 any continued degradation. The revised limit far exceeds the estimated 120 square inches to be applied to the McGuire and Catawba surge nozzles and so provides a conservative basis for application of the proposed PWOL.

There are three potential technical concerns that the 100 square inches limitation may have been intended to prevent: residual stresses, tempering of the weld heat affected zone (HAZ), and the possible (but unlikely) development of delayed hydrogen cracking in the underlying ferritic base material. These potential concerns are addressed below:

(a) Residual Stresses - An EPRI sponsored analyses [Ref 7] of an overlay that just equaled 100 square inches coverage over the ferritic steel base metal was performed. Two axisymmetric finite element models were created, one with the 100 square inches weld overlay and the other with the weld overlay extended on the nozzle side until it blended into the nozzle taper surface (approximately 126 square inches). Figure 5.1 shows the post overlay residual stress on the nozzle inside surface for both models. It is seen that the extended overlay configuration did not significantly alter the residual stress results, and if anything, made the axial stresses even more compressive.

The Feedwater nozzle configuration modeled in [Ref 7] was roughly similar to the MNS and CNS surge nozzles; however, it is not necessary to rely on this similarity since nozzle specific residual stress analyses are being conducted as part of the Duke PWOL project. The resulting post-overlay inside surface residual stress distributions for the MNS/CNS surge nozzles are shown in Figure 5.2. It is seen from this figure that the MNS/CNS surge nozzle weld overlay design, with its approximately 120 square inches coverage over the ferritic steel base metal, creates favorable compressive residual stresses on the inside surface of the nozzle.

(b) HAZ Tempering -Reference [8] presents results of a bimetallic weld overlay mockup of a 12 inch diameter, SA-508 Class 2 low alloy steel nozzle. The overlay applied to this nozzle covered approximately 119 square inches of the low alloy steel nozzle (about the same as the MNS/CNS surge nozzle overlay). Microstructure and microhardness measurements were performed on the HAZ of this overlay, as well as mechanical property tests (Charpy and Tensile) of a groove weld in the same nozzle with similar coverage area. The mechanical property results verified that the weld overlay repair did not degrade the strength or toughness of the low alloy steel HAZ. Microstructure and microhardness results demonstrated adequate tempering of the material, such that hydrogen embrittlement would not be expected. This demonstration was conducted on a weld overlay geometry with essentially identical low alloy steel (LAS) coverage as the MNS/CN3 surge nozzle overlay.

(c) Delayed Hydrogen Cracking - Inspections of the above described mockup, as well as extensive inspections of temper bead weld overlays in mockups and in the field, have been performed, of overlays with LAS coverages ranging from less than 10 square inches up to and including 325 square inches.

These have shown that hydrogen induced cracking has not been a problem with repairs produced by the automatic GTAW temper bead process. The process is by its nature a low hydrogen process, and diffusion of hydrogen is very rapid for low alloy steels. Nonetheless, the post weld soaks specified in the Code are intended as post hydrogen bake outs permitting NDE after the repair has returned to ambient temperature. N-638, since it does not impose the post weld bake, requires a 48-hour hold time prior to NDE, to verify that the unlikely event of hydrogen induced cold cracking has not occurred. The Duke Page 6 of 30

Request No. 07-GO-001 Enclosure 1 weld overlay procedure will conform to the 48-hour hold time requirement prior to performing NDE.

Furthermore, the metallurgical aspects discussed above are independent of the surface area of the repair but related to parameters of the qualified welding procedure.

Finally, it is important to note that the above theoretical arguments and empirical data have been verified in practice by extensive field experience with temper bead weld overlays, with LAS coverage ranging from less than 10 square inches up to and including 325 square inches. Table 5.1 below provides a partial list of such applications. It is seen from this table that the original DMW weld overlay was applied over 20 years ago, and WOLs with LAS coverage in the 100 square inches range have been in service for 5 to 15 years. Several overlays have been applied with LAS coverage significantly greater than the 100 square inches. Relief requests for these large overlays have been previously approved. These overlays have been examined with PDI qualified techniques, in some cases multiple times, and none have shown any signs of new cracking or growth of existing cracks.

Temperature monitoring required by Code Case N-638-1 will be performed using temporarily attached or contact pyrometers and manual data recording in lieu of thermocouples and recording equipment required by IWA-4610(a) of Section XI. The thermocouple pyrometers proposed for use are calibrated in accordance with the suppliers QA program approved by Duke and will provide temperature information equivalent to that obtained from weld attached thermocouples. Control of interpass temperature as required by N-638-1 will be met by the proposed technique. This exception has been permitted by the NRC in the past (see precedent 6 in Para. 8.0 below). As described in Table A3 in Attachment 1, use of pyrometers will provide acceptable temperature monitoring for application of the PWOL.

In addition to the ultrasonic examination of a 1.5T band of material on each end of the weld, the conditional approval of Code Case N-638-1 imposes a condition that the ultrasonic examination be qualified on samples using construction type flaws and that the acceptance criteria be in accordance with NB-5330 of Section III of the ASME Boiler and Pressure Vessel Code. In lieu of this requirement, Duke proposes to use a PDI qualified ultrasonic examination procedure that is designed and qualified to examine the entire volume of the overlay weld as well as the region of the P3 material containing the weld HAZ and a volume of unaffected base material beyond the HAZ (see Figures 5.3, 5.4 and 5.5)

Code Case N-63 8-1 addresses the use of the temper bead welding technique including those welds made in deep cavities in ferritic material. In the case of weld overlays to be applied at MINS/CNS, this technique will be used to apply a non-ferritic overlay to the P3 ferritic nozzle base material adjacent to the dissimilar metal weld (DMW). In addition to verifying the soundness of the weld, a purpose of these examinations is to assure that delayed cracking that may be caused by hydrogen introduced during the temper bead welding process is not present. In the unlikely event that this type of cracking does occur, it would be initiated on the surface on which the welding is actually performed or in the HAZ immediately adjacent to the weld. The most appropriate technique to detect surface cracking is the surface examination technique that Duke will perform on the weld overlay and the adjacent base material in a band at least 1.5 times the thickness of the base material on either side of the overlay. As shown in Figures 5.3, 5.4 and 5.5, a significant fraction of the 1.5T band will be included in the proposed PDI inspection. The combined UT and surface inspection will cover 100% of the area susceptible to weld induced defects. While it would be possible with additional expenditure of time and equipment to extend the examination volume to a larger extent on either side of the weld overlay, it would not be possible with Page 7 of 30

Request No. 07-GO-001 Enclosure 1 current technology to ultrasonically inspect 100% of the volume within 1.5 times the thickness of the base material because of geometric considerations. Inspection of an increased volume would result in increased dose to inspection personnel without a compensating increase in safety or quality because there is no plausible mechanism for formation of new flaws or propagation of existing flaws into the region.

That is, any expanded inspection would be performed on material that would not otherwise be inspected as part of an ASME Section XI or ASME Section III required weld examination. The overlay volume is small relative to the volume of the underlying pipe and does not present the same concerns as those related to welds in deep cavities contemplated by the requirements of Code Case N-638-1. Therefore, the examinations tailored for overlay inspection and required by Code Case N-504-2 and Appendix Q as modified in the request for relief provide full assurance that the weld and adjoining base material are fully capable of performing their intended function.

ASME Section XI pre-service acceptance standards, as specified in Appendix Q, are the appropriate standards for pre-service ultrasonic examinations of weld overlay repairs to nuclear plant components.

These standards are consistent with the highly sensitive ultrasonic examination procedures being used, which are qualified in accordance with ASME Section XI, Appendix VHI, Supplement XI, as implemented via the EPRI Performance Demonstration Initiative (PDI). The post-repair inspection volume includes the full thickness of the weld overlay plus 25% of the underlying base metal/weldment thickness. The specimen sets for PDI qualification of weld overlay examinations include construction type flaws in the overlays in addition to simulated service flaws in the underlying base metal and weldment. Therefore, use of PDI-qualified personnel and procedures will result in the reliable detection of construction type flaws.

The ASME Section XI flaw acceptance standards are based on fracture mechanics principles that evaluate the potential effect of flaw indications on the safe operation of a component. ASME Section III ultrasonic standards, on the other hand, are derived from radiographic standards in earlier construction codes and tend to be workmanship-based, addressing flaws occurring in the original construction process that are likely to be detected by radiography. The ASME Section III acceptance criteria do not allow the presence of any cracks or crack-like indications, regardless of their size, and are geared more towards construction-type welds. Many indications that are detectable by PDI qualified ultrasonic techniques, and thus require evaluation, would not be detected by the radiographic examinations required by the original construction Code or Section III. It is therefore not reasonable, nor technically logical, to reject such indications based on out-dated, workmanship-based standards when found by much more sensitive examination techniques that are not required by the construction Codes.

The Section XI pre-service examination standards were developed for exactly the above-stated reasons, and consider the materials in which the flaw indications are detected, the orientation and size of the indications, and ultimately their potential structural impact on the component. They are the logical choice for evaluation of potential flaw indications in post-overlay examinations, in which unnecessary repairs to the overlays would result in additional personnel radiation exposure without a compensating increase in safety and quality, and could potentially degrade the effectiveness of the overlays by affecting the favorable residual stress field that they produce.

Acceptance of ultrasonic indications in weld overlay repairs using Section XI acceptance criteria has been approved by NRC in past weld overlay applications (e.g. References 9, 10). The following Page 8 of 30

Request No. 07-GO-001 Enclosure 1 information will be submitted to the NRC within fourteen days of completion of the final UT on each unit included in this relief request. Also included in the results will be a discussion of any repairs to the overlay material and/or base metal and the reason for the repair.

" a listing of flaw indications detected'

" the disposition of all indications using the standards of ASME Section XI, IWB-3514-2 and/or IWB-3514-3 criteria and, if possible,

• the type and nature of theindications2 Subsequent Inservice examination of the structural weld overlays on pressurizer will be in accordance with ASME Section XI, Appendix Q, Q-4300 In summary, this letter requests relief from portions of the applicable ASME Code and Code Cases approved for use by the NRC. There are no new or different approaches in this overlay design that are considered first of a kind or inconsistent with previous applications. The overlay is designed as a full structural overlay in accordance with ASME Code Case N-504-2 and Section XI, Nonmandatory Appendix Q.

'The recording criteria of the ultrasonic examination procedure to be used for the examination of the McGuire and Catawba pressurizer overlays (SI-UT-126 Rev.0) requires that all suspected flaw indications, regardless of amplitude, be investigated to the extent necessary to provide accurate characterization, identity, and location.

Additionally, the procedure requires that all indications, regardless of amplitude, that cannot be clearly attributed to the geometry of the overlay configuration be considered flaw indications.

2 The ultrasonic examination procedure states that all suspected flaw indications should be plotted on a cross sectional drawing of the weld and that the plots should accurately identify the specific origin of the reflector.

Page 9 of 30

\,

Request No. 07-GO-001 Enclosure 1 Residual Axial Stress Along Inside Wall 5

Length of 100 in-2 Weld Overlay 0

U)-10 15

-20

-25 ÷ 100 in^2

-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 Axial Distance (Y) From Weld Centerline (in)

Residual Hoop Stress Along Inside Wall

. 0 Length of 10 in'2 Weld Overlay

-5

-10 U)

-15

--

0-10,i A,':"

0 -20 0

-2 5

-30 Extended," ,i,

-7 a-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 Axial Distance (Y) From Weld Centerline (in)..

Figure 5.1 Residual Stress Distribution from ASME White Paper (see Text)

Page 10 of 30

Request No. 07-GO-001 Enclosure 1 McGuire/Catawba Pressurizer Surge Nozzle ID Surface Axial Residual Stress Nozzle (LAS)

I

.......0.. ..... . . .

-1.0 -1.2 -1.4 -1.6 -1.8 -, .0

. -20

• . .... . ...

. ......... ..

......................................

........................

a

-- 30 cn

- -40 0 Post-WOL4-70F

-50

-'- Post-WOL4-650F

-- 60 .... .... ......

........ S... ....

- -70 Distance from ID Weld Repair Centerline (in)

McGuirelCatawba Pressurizer Surge Nozzle ID Surface Hoop Residual Stress U,

Distance from ID Weld Repair Centerline (in)

Figure 5.2 Calculated Residual Stress Distribution for McGuire and Catawba (see Text)

Page 11 of 30

Request No. 07-GO-001 Enclosure 1 Table 5.1-Representative Dissimilar Metal Weld Overlay Experience Nozzle Diameter Approx. LAS Date Plant Component (in) Coverage (in2 )

December 2006 Catawba Unit I Spray nozzle 6 33 Safety/relief nozzles 8 55 Surge nozzle 15 120 October 2006 Oconee Unit 1 Spray nozzle 4.5 30 Safety/relief nozzles 4.5 30 PZR surge nozzle 11.5 125 Hot leg surge nozzle 11.5 70 September 2006 McGuire Unit 2 Spray nozzle 6 33 Safety/relief nozzles 8 55 Surge nozzle 15 120 April 2006 Davis Besse Cold leg drain nozzle 4 16 February 2006 SONGS Unit 2 PZR spray nozzle 8 50 safety/relief nozzles 6 28 November 2005 Kuosheng Unit 2 Recirculation outlet 22 250 nozzle April 2004 Susquehanna Unit 1 Recirc. inlet nozzle 12 100 Recirc. outlet nozzle 28 325 November 2003 TMI Unit 1 Surge line nozzle 11.5 75 October 2003 Pilgrim Core spray nozzle 10 50 CRD return nozzle 5 20 October 2002 Peach Bottom Units 2 Core spray nozzle 10 50

&3 Recirc. outlet nozzle 28 325 CRD return nozzle 5 20 October 2002 Oyster Creek Recirc. outlet nozzle 26 285 December 1999 Duane Arnold Recirc. inlet nozzle 12 100 June 1999 Perry Feedwater nozzle 12 100 June 1998 Nine Mile Point Unit Feedwater nozzle 12 100 2

March 1996 Brunswick Units 1 & Feedwater nozzle 12 100 2

February 1996 Hatch Unit 1 Recirc. inlet nozzle 12 100 January 1991 River Bend Feedwater nozzle 12 100 March 1986 Vermont Yankee Core spray nozzle 10 50 Page 12 of 30

Request No. 07-GO-00l Enclosure 1 V ~

Dashed lines indicate ISI I I inspection volume 1 Overlay and Overlay heat affected zone will be inspected except in cross hatched volume.

Dimensions shown are typical. Coverage not shown at austenitic end.

Figure 5.3 Phased array UT coverage for MNS/CNS Pressurizer Safety & Relief Nozzles.

Page 13 of 30

Request No. 07-GO-001 Enclosure 1 Overlay and Overlay heat affected zone will be inspected except in cross hatched volume.

Dimensions shown are typical. Coverage not shown at austenitic end.

Figure 5.4 Phased array UT coverage for MNS/CNS Pressurizer Spray Nozzles.

Page 14 of 30

Request No. 07-GO-001 Enclosure 1 Overlay and Overlay heat affected zone will be inspected except in cross hatched volume.

Dimensions shown are typical. Coverage not i*

shown at austenitic end.

Figure 5.5 Phased array UT coverage for M7NS/CNS Pressurizer Surge Nozzles Page 15 of 30

Request No. 07-GO-001 Enclosure 1 6.0 WELD OVERLAY DESIGN AND VERIFICATION The design of these weld overlays incorporates the requirements of ASME Code Case N-504-2, and Code Case N-638-1, with modifications as described above in Section 5.0 and in the attached tables. The weld overlays will be demonstrated to be long-term repairs and mitigation of PWSCC based on analyses that will be completed before plant restart. The fundamental design basis for full structural weld overlays is to maintain the original safety margins of the welds, with no credit taken for the underlying PWSCC susceptible weldments. The design basis flaw for the purpose of structural sizing of the overlay is assumed to be 360 degrees and 100% through the original wall thickness of the DMW. For the crack growth analysis the initial flaw size is assumed to be 360 degrees and 75% through the original wall thickness. The 75% through-wall assumption is selected based upon the PDI-qualified inspection of the overlay at the conclusion of the weld overlay process, which includes the outer 25% of the original weld.

If flaws are detected in the post-overlay inspection, they will be evaluated in accordance with the requirements of Code Case N-504-2 and Appendix Q. Analyses are performed to demonstrate that the overlay designs meet the requirements of ASME Code,Section XI, IWB-3640, in addition to the structural requirements of ASME Code Case N-504-2 for full structural weld overlays. No credit is taken for the diluted first layer of the overlays over the PWSCC susceptible weldments. Each required analysis will be bounding for the two units included in this request for relief. Following is a listing of the analyses and verifications that will be performed.

1. Nozzle specific stress analyses will be performed to establish a residual stress profile in the nozzle. Severe ID weld repairs have been assumed that effectively bound any actual weld repairs to the nozzle. The weld overlay is subsequently applied to simulate the final residual stress profile. Post weld overlay residual stresses at normal operating conditions will then be shown to result in beneficial compressive stresses on the inside surface of the components, further assuring that crack growth into the overlay is highly unlikely.

2. Fracture mechanics analyses will also be performed to predict crack growth, assuming that cracks exist that are equal to or greater than the thresholds of the NDE techniques to be used on the nozzles. Potential crack growth will be evaluated due to PWSCC as well as due to fatigue crack growth in the original DMW. The crack growth analyses will consider all design loads and transients, plus the post weld overlay residual stress distributions, and will demonstrate that cracks will not grow beyond the original DMW thickness for the time period until the next scheduled inservice inspection.

3. The analyses will demonstrate that application of the weld overlays does not impact the conclusions of the existing nozzle Stress Reports. ASME Code,Section III stress and fatigue criteria will be met, as spelled out in ASME Code Case N-504-2.

4. Shrinkage will be measured during the overlay application. Shrinkage stresses at other locations in the piping systems arising from the weld overlays will be demonstrated not to have an adverse effect on the systems. Clearances of affected support and restraints will be checked after the overlay repair, and will be reset within the design ranges as required.

5. The total added weight on the piping systems due to the overlays will be evaluated for potential impact on piping system stresses and dynamic characteristics.

6. The as-built dimensions of the weld overlays will be measured and evaluated to demonstrate that they equal or exceed the minimum design dimensions of the overlays.

Page 16 of 30

Request No. 07-GO-001 Enclosure 1 Summaries of the results of the analyses listed in items 1 through 3 above will be submitted to the NRC prior to entry into mode 4. Items 4 through 6 will be completed prior to entry into mode 4 but will not be submitted for review. The data of the latter three items will be available for review by the NRC resident or field inspectors if needed.

7.0 DURATION OF THE PROPOSED ALTERNATIVES These full structural weld overlays will be installed during the third inservice inspection interval for each of the units covered by this Relief Request.

Catawba Unit 2 third interval: Beginl0/15/2005 End 8/19/2016 McGuire Unit 1 third interval: Begin 12/1/2001 End 12/1/2011 These overlays will remain in place for the design life of the repair that is defined by the evaluation required in paragraph (g) of Code Case N-504-2 and corresponding requirements in Nonmandatory Appendix Q.

8.0 PRECEDENTS

1. Letter from Richard J. Laufer, NRC, to Christopher M. Crane, AmerGen, "Three Mile Island Nuclear Station, Unit 1 (TMI-1) Request for Relief from Flaw Removal, Heat Treatment, and Nondestructive Examination Requirements for the Third 10-year Inservice Inspection (ISI)

Interval (TAC.No. MC1201)," Accession Number ML041670510, dated July 21, 2004.

2. Letter from Richard J. Laufer, NRC, to Bryce L. Shriver, PPL Susquehanna, "Susquehanna Steam Electric Station, Unit 1 - Relief from American Society of Mechanical Engineers, Boiler and Pressure Vessel Code (ASME Code),Section XI, Appendix VIII, Supplement 11, Requirements and Code Cases N-504-2 and N-638 Requirements (TAC Nos. MC2450, MC2451 and MC2594)," Accession Number ML051220568, dated June 22, 2005.

3. Letter from L. Raghavan, NRC, to Mano K. Nazar, I&M, "Donald C. Cook Nuclear Plant, Unit 1

- Alternative to Repair Requirements of Section XI of the American Society of Mechanical Engineers Code (TAC No. MC0675 1)," Accession Number ML051720006, dated June 27, 2005.

4. Letter from Richard J. Laufer, NRC, to George Vanderheyden, Calvert Cliffs, "Calvert Cliffs Nuclear Power Plant, Unit No. 2 - Relief Request for Use Weld Overlay and Associated Alternative Inspection Techniques (TAC Nos. MC6219 and MC6220)," Accession Number ML051930316, dated July 20, 2005.

5. Letter from Darrell J. Roberts, NRC, to David A. Christian Dominion Nuclear Connecticut, Inc.,

"Millstone Power Station, Unit No. 3 - Issuance of Relief from Code Requirements (TAC No.

MC8609)," Accession Number ML053260012, dated January 20, 2006.

6. Southern California Edison's San Onofre Unit 2, verbal authorization given on March 23, 2006.

7. First Energy's Davis Besse Unit 1, verbal authorization given on April 5, 2006.

8. Duke Energy Corporation, Request for Relief 06-ON-004, for Oconee Unit 1, verbal authorization given on October 30, 2006.

Page 17 of 30

Request No. 07-GO-00 1 Enclosure 1

9. Duke Energy Corporation, Request for Relief 06-GO-001, for McGuire Unit 2, verbal authorization given on September 28, 2006.

10. Duke Energy Corporation, Request for Relief 06-GO-001, for Catawba Unit 1, verbal authorization given on December 18, 2006.

9.0 REFERENCES

(1) ASME Code,Section XI, 1998 Edition through 2000 Addenda, Article IWA-4000.

(2) ASME Code,Section XI, 1998 Edition through 2000 Addenda, Mandatory Appendix VIII, Supplement 11.

(3) ASME Code Case N-504-2, Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping,Section XI, Division 1, March 12, 1997.

(4) ASME Code Section XI, through 2005 Addenda, Nonmandatory Appendix Q, Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments.

(5) ASME Code Case N-638-1, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,Section XI, Division 1 , February 13, 2003.

(6) Calvert Cliffs, Units 1 & 2 - ASME Section XI Relief Request to Use Weld Overlay &

Associated Alternative Techniques, Accession Number ML060240110, dated January 18, 2006.

(7) "Justification for the Removal of the 100 Square Inch Limitation for Ambient Temperature Temper Bead Welding on P-3 Material", EPRI-NP- 1011898, February 2005.

(8) "Inconel Weld-Overlay Repair for Low-Alloy Steel Nozzle to Safe-End Joint", EPRI NP-7085-D, January 1991.

(9) Safety Evaluation .by the Office of Nuclear Reactor Regulation related to Three Mile Island Nuclear Station, Unit 1 (TMI-1) Request for Relief from Flaw Removal, Heat Treatment and Non-Destructive Examination (NDE) Requirements for the Third 10-Year Inservice Inspection (ISI) Interval, Amergen Energy Company, LLC Docket No. 50-289, July 21, 2004.

(10) Safety Evaluation by the Office of Nuclear Reactor Regulation Inservice Inspection Program Relief Request ISIR-17, Donald C. Cook Nuclear Plant, Unit 1 (DCCNP-1), Indiana Michigan Power, Docket No. 50-315, February 10, 2006.

10.0 CONCLUSION

Duke concludes that the alternative repair approach described above presents an acceptable level of quality and safety to satisfy the requirements of 10 CFR 50.55a(a)(3)(i). The approach described in this relief request includes evaluation of available operating experience related to previously NRC approved applications of overlays to DMW.

Page 18 of 30

Request No. 07-GO-001 Enclosure 1 ATTACHMENT 1 CONTENTS Figure Al Pressurizer Nozzle Weld Overlay (Typical)

Table Al Modifications to Code Case N-504-2 and Corresponding Non-Mandatory Appendix Q Requirements Table A2 Alternatives to Appendix VIII, Supplement 11 Table A3 Modifications to Code Case N-638-1 Page 19 of 30

Request No. 07-GO-001 Enclosure 1

.SA-533 GrA CI 2 or 2a PZR. HEAD, FORGING SA-508 CL.2 SAFETY NOZZLE FORGING

-ALLOY 52M WELD OVERLAY SA-403 Gr WP304

'ATTACHED PIPING ALLOY 82/182, WELD/BUTTER SA-182 Cr F316L SAFE END Figure Al Pressurizer Nozzle Weld Overlay (Typical)

Page 20 of 30

Request No. 07-GO-001 Enclosure 1 Table Al Modifications To Code Case N-504-2 andfCorresponding Non-Mandatory Appendix Q Requirements Code Case N-504-2 Modification/Basis Modification. Code Case N-504-2 will be used for weld overlay repairs to the ferritic (P3) and nickel alloy (F43/P43) base material as well as the Reply: It is the opinion of the Committee that, in lieu of the requirements of austenitic stainless steel (P8) base material.

IWA-4120 in Editions and Addenda up to and including the 1989 Edition Basis: Code Case N-504-2 is acceptedfor use along with Nonmandatory with the 1990 Addenda, in IWA-4170(b) in the 1989 Edition with the 1991 Appendix Q in the currentNRC Regulatory Guide 1.147 Rev. 14. For the Addenda up to and including the 1995 Edition, and in IWA-44 10 in the 1995 weld overlay of the identified welds at McGuire and Catawba Units I & 2 Edition with the 1995 Addenda and later Editions and Addenda, defect in the base materialwill beferritic material (P3) with existing nickel alloy weld austenitic stainless steel piping may be reduced to a flaw of acceptable size metal (F43/P43)to which an austeniticstainlesssteel (P8)safe end is in accordance with .WB-3640 from the 1983 Edition with the Winter 1985 welded. Industry operationalexperience has shown that PWSCC in Alloy Addenda, or later Editions and Addenda, by deposition of weld 82/182 will blunt at the interface with stainless steel base metal, ferritic base reinforcement (weld overlay) on the outside surface of the pipe, provided the metal, orAlloy 52/52M/52MS weld metal. The 360°structuralweld overlay following requirements are met. [Essentially same as Scope of will control growth in any PWSCC crack and maintain weld integrity. The Appendix Q]: weld overlay will induce compressive stress in the weld, thus impeding growth of any reasonably shallow cracks. Furthermore,the overlay will be sized to meet all structuralrequirementsindependent of the existing weld.

Modification. In lieu of austenitic stainless steel filler material, the reinforcement weld metal will be a nickel alloy.

Basis: The weld metal used may be ERNiCrFe-7A (Alloy 52M, UNS N06054) or ERNiCrFe-7(Alloy 52 UNS N06052). This weld metai is assignedF43 by ASME per Code Case 2142-2. The requirements ofASME Section Ill, NB-2400 will be applied to allfillermaterial. The chromium content ofAlloy 52M/MS is 28-31.5%, identicalto that ofAlloy 52. The main difference in (b) Reinforcement weld metal shall be low carbon (0.035% max.) austenitic Alloy 52 vs. Alloy 52M/MS is a higher Niobium content (0.5-1 %). The stainless steel applied 3600 around the circumference of the pipe, and shall be difference in chemical composition between Alloy 52 and Alloy 52M/MS deposited in accordance with a qualified welding procedure specification improves the weld-ability of the materialandpins the grain boundariesthus identified in the Repair Program. [Same as Q-2000(a)I preventing separationbetween the grainsand hot tearingduring weld puddle solidification. These filler materialswere selectedfor their improved resistance to PWSCC. Alloys 52 and 52M/MS contain about 30% chromium that imparts excellent corrosionresistance. The existing Alloy 82/182 weld and the Alloy 52M/52MS overlay are nickel base and have ductileproperties and toughness similar to austeniticstainless steelpiping welds at pressurized water reactoroperatingtemperature. These filler materials are suitablefor welding over the ferritic nozzle, Alloy 82/182 weld, and the austenitic Page 21 of'30

Request No. 07-GO-001 Enclosure 1 Table Al Modifications To Code Case N-504-2 and Corresponding Non-Mandatory Appendix Q Requirements Code Case N-504-2 Modification/Basis stainless steel safe end orpipe components.

(e) The weld reinforcement shall consist of a minimum of two weld layers having as-deposited delta ferrite content of at least 7.5 FN. The first layer of Modification: Delta ferrite (FN) measurements will not be performed for weld metal with delta ferrite content of least 7.5 FN shall constitute the first weld overlay repairs made of Alloy 52/52M/52MS weld metal.

layer of the weld reinforcement design thickness. Alternatively, first layers Basis: Welds ofAlloy52/52M/52MS are 100% austenitic and contain no of at least 5 FN may be acceptable based on evaluation. [Same as Q- deltaferrite due to the high nickel composition (approximately60% nickel).

2000(d)]

Modification: If a flaw or evidence of a flaw is observed, in lieu of hydrostatic testing, a system leakage test and an ultrasonic examination (UT)

Pressure Testing of the weld overlay will be performed consistent with ASME IWA-(h) The completed repair shall be pressure tested in accordance with IWA- 4540(a)(2), as modified by Nonmandatory Appendix Q.

5000. If the flaw penetrated the original pressure boundary prior to welding, Basis: Application of IWA-4540(a)(2)for a system leakage test in lieu of a or if any evidence of a flaw penetrating the pressure boundary is observed system hydrostatic test requiresperformanceof NDE in accordance with the or faw i an evdene eneratng ofa te pessre oundry s osered, methods and acceptance criteriaof the applicableSubsection of the 1992 during the welding operation, a system hydrostatic test shall be performed in Edition of ASME Section IlL ASME Section III Subsection NB Article 5000 accordance with IWA-5000. If the system pressure boundary has not been penetrated, a system leakage, inservice, or functional test shall be performed for Examination does not address the structuralweld overlay type in accordance with IWA-5000. configuration. The NDE requirements ofNonmandatoryAppendix Q will be followedfor the requiredNDE in lieu ofASME Section III. Code Case N-504-2 and NonmandatoryAppendix Q provide appropriateexamination requirements including examination volume, acceptance criteria,and examination methods per Appendix VIII.

Page 22 of 30

Request No.07-GO-001 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 Appendix Viii of Section XI cannot be used for NDE of a structural weld overlay repair. Relief is requested to use the PDI program implementation of Appendix VIII. A detailed comparison of Appendix V1ll and PDI requirements is summarized below.

Relief is requested to allow closer spacing of flaws provided the flaws do not interfere with detection or discrimination of other discontinuities.

The specimens used for qualification to the Tni-party (NRC/BWROG/EPRI) agreement have a flaw population density greater than allowed by current Code requirements. These samples have been used successfully for all previous qualifications under the Tri-party agreement program. To facilitate their use and provide continuity from the Tri-party agreement program to Supplement 11, the PDI program has merged the Tri-party test specimens into their structural weld overlay program.

SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR PDI PROGRAM:

FULL STRUCTURAL OVERLAID WROUGHT AUSTENITIC The Proposed Alternative to Supplement 11 Requirements PIPING WELDS 10 SPECIMEN REQUIREMENTS 1.1 General. The specimen set shall conform to the following requirements.

(b) The specimen set shall consist of at least three specimens having different nominal pipe diameters minimumandmaximumnominal and pipe overlay anddiameters thicknesses.. Theyhey overayhhic shall shal include iath the n Alternative: (b) The specimen set shall include specimens with overlays not thicker than 0.1 inch more than the minimum thickness, nor thinner than 0.25 procedure is applicable. Pipe diameters within a range of 0.9 to 1.5 times a nominal diameter shall be considered equivalent. If the procedure is applicable procedure is applicable.

to pipe diameters of 24 inch or larger, the specimen set must include at least proedueTi Basis: appicable.

To avoid confusion, the overlay thickness tolerance contained in the one specimen 24 inch or larger but need not include the maximum diameter. last sentence was reworded and the phrase "and the remaindershall be The specimen set must include at least one specimen with overlay thickness alternativeflaws'"was added to the next to last sentence in paragraph1.1 (d) within -0.1 inch to +0.25 inch of the maximum nominal overlay thickness for which the procedure is applicable.

(d) Flaw Conditions Alternative: (1) ... must be in or... intentional overlay fabrication flaws shall (1) Base metal flaws. All flaws must be cracks in or near the - butt weld heat- not interfere with ultrasonic detection or characterization of the base metal affected zone, open to the inside surface, and extending at least 75% through flaws. Specimens containing intergranular stress corrosion cracking shall be the base metal wall. Flaws may extend 100% through the base metal and into used when available. At least 70% of the flaws in the detection and sizing tests the overlay material; in this case, intentional overlay fabrication flaws shall shall be cracks and the remainder shall be altemative flaws. Alternative flaw not interfere with ultrasonic detection or characterization of the cracking. mechanisms, if used, shall provide crack-like reflective characteristics and Specimens containing IGSCC shall be used when available, shall be limited by the following:

I (a) The use of alternative flaws shall be limited to when the implantation of Page 23 of 30

Request No. 07-GO-00 1 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR PDI PROGRAM:

FULL STRUCTURAL OVERLAID WROUGHT AUSTENITIC The Proposed Alternative to Supplement 11 Requirements PIPING WELDS cracks produces spurious reflectors that are uncharacteristic of actual flaws.

(b) Flaws shall be semi elliptical with a tip width of less than or equal to 0.002 inches.

Basis: This paragraphrequires that all base metalflaws be cracks.

Implanting a crack requiresexcavation of the base material on at least one side of theflaw. While this may be satisfactoryfor ferritic materials,it does not produce a useable axialflaw in austeniticmaterials because the sound beam, which normallypasses only through base material,must now travel through weld material on at least one side, producingan unrealisticflaw response. To resolve this issue, the PDIprogram revised this paragraphto allow use of alternativeflaw mechanisms under controlled conditions.For example, alternativeflaws shall be limited to when implantation of cracks precludes obtaining an effective ultrasonicresponse,flaws shall be semi elliptical with a tip width of less than or equal to 0. 002 inches, and at least 70% of the flaws in the detection and sizing test shall be cracks and the remaindershall be alternativeflaws. To avoid confusion, the overlay thickness tolerancecontainedin paragraph1.1 (b) last sentence, was rewordedand the phrase "and the remaindershall be alternativeflaws" was added to the next to last sentence. Paragraph1.1(d)(1) includes the statement that intentionaloverlayfabricationflaws shall not interfere with ultrasonic detection or characterizationof the base metalflaws.

(e) Detection Specimens Alternative: (1) At least 20% but less than 40% of the base metal flaws shall be oriented within +/-20' of the pipe axial direction. The remainder shall be oriented circumferentially. Flaws shall not be open to any surface to which the candidate has physical or visual access.

(1) At least 20% but less than 40% of the flaws shall be oriented within +/-200 Basis: The requirementfor axially orientedoverlay fabricationflaws was of the pipe axial direction. The remainder shall be oriented circumferentially.

excludedfrom the PDIProgram as an improbable scenario. Weld overlays Flaws shall not be open to any surface to which the candidate has physical or are typically appliedusing automated GTA W techniques with the filler metal.

visual access. The rules of IWA-3300 shall be used to determine whether applied in a circumferentialdirection. Because resultantfabricationinduced closely spaced flaws should be treated as single or multiple flaws.

discontinuitieswould also be expected to have major dimensions oriented in the circumferentialdirection axial overlayfabricationflaws are unrealistic.

The requirementfor using IWA-3300forproximityflaw evaluation was excluded; instead indicationswill be sized based on their individual merits.

Page 24 of 30

Request No. 07-GO-001 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR PDI PROGRAM:

FULL STRUCTURAL OVERLAID WROUGHT AUSTENITIC The Proposed Alternative to Supplement 11 Requirements PIPING WELDS Alternative: (2) Specimens shall be divided into base metal and overlay fabrication grading units. Each specimen shall contain one or both types of (2) Specimens shall be divided into base and overlay grading units. Each grading units. Flaws shall not interfere with ultrasonic detection or specimen shall contain one or both types of grading units. characterization of other flaws.

Basis: Inclusion of "metal" and 'fabrication"provides clarification.Flaw identification is improved by ensuringflaws are not masked by otherflaws.

Alternative: (a)(1) A base metal grading unit includes the overlay material and the outer 25% of the original overlaid weld. The base metal grading unit shall extend circumferentially for at least 1 inch and shall start at the weld centerline and be wide enough in the axial direction to encompass one half of (a)(1) A base grading unit shall include at least 3 inch of the length of the the original weld crown and a minimum of 0.50" of the adjacent base material.

overlaid weld. The base grading unit includes the outer 25% of the overlaid Basis: The phrase "andbase metal on both sides,"was inadvertently included weld and base metal on both sides. The base grading unit shall not include the in the descriptionof a base metal grading unit, The PDIprogram intentionally inner 75% of the overlaid weld and base metal overlay material, or base metal excludes this requirementbecause some of the qualificationsamples include to-overlay interface, flaws on both sides of the weld. To avoid confusion several instances of the term "cracks" or "cracking" were changed to the term 'flaws" because of the use of alternativeFlaw mechanisms. Modified to requirethat a base metal gradingunit include at least] inch of the length of the overlaid weld, ratherthan 3 inches.

Alternative: (a)(2) When base metal flaws penetrate into the overlay material, (a)(2) When base metal cracking penetrates into the overlay material, the base the base metal grading unit shall not be used as part of any overlay fabrication grading unit shall include the overlay metal within 1 inch of the crack grading unit.

location. This portion of the overlay material shall not be used as part of any Basis: Substituted terms provide clarification and are consistent with Id(1) overlay grading unit. above. The PDIprogram adjustsfor this conservative changefor excluding this type gradingunit.

Alternative: (a)(3) Sufficient unflawed overlaid weld and base metal shall (a)(3) When a base grading unit is designed to be unflawed, at least 1 inch of exist on all sides of the grading unit to preclude interfering reflections from unflawed overlaid weld and base metal shall exist on either side of the base adjacent flaws.

grading unit. The segment of weld length used in one base grading unit shall Basis: Modified to requiresufficient unflawed overlaid weld and base metal to not be used in another base grading unit. Base grading units need not be exist on all sides of the grading unit to preclude interfering reflectionsfrom uniformly spaced around the specimen. adjacentflaws, ratherthan the ] inch requirement.

Page 25 of 30

Request No. 07-GO-001 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR PDI PROGRAM:

FULL STRUCTURAL OVERLAID WROUGHT AUSTENITIC The Proposed Alternative to Supplement 11 Requirements PIPING WELDS Alternative: (b)(1) An overlay fabrication grading unit shall include the overlay material and the base metal-to-overlay interface for a length of at least 1 inch (b)(1) An overlay grading unit shall include the overlay material and the base Basis: The PDlprogramreduces the base metal-to-overlay interface to at metal-to-overlay interface of at least 6 in2 . The overlay grading unit shall be least I inch (in lieu of a minimum of 2 inches) and eliminatesthe minimum rectangular, with minimum dimensions of 2 inch rectangulardimension. This criterion is necessary to allow use of existing examination specimens that werefabricatedin order to meet NRC Generic Letter 88-01. This criterionmay be more challenging than the ASME Code because of the variabilityassociatedwith the shape of the gradingunit.

-4.

Alternative: (b)(2) Overlay fabrication grading units designed to be unflawed shall be separated by unflawed overlay material and unflawed base metal-to-overlay interface for at least 1 inch at both ends. Sufficient unflawed overlaid weld and base metal shall exist on both sides of the overlay fabrication (b)(2) An overlay grading unit designed to be unflawed shall be surrounded by grading unit to preclude interfering reflections from adjacent flaws. The unflawed overlay material and unflawed base metal-to-overlay interface for at specific area used in one overlay fabrication grading unit shall not be used in least 1 inch around its entire perimeter. The specific area used in one overlay another overlay fabrication grading unit. Overlay fabrication grading units grading unit shall not be used in another overlay grading unit. Overlay grading need not be spaced uniformly about the specimen.

units need not be spaced uniformly about the specimen.

Basis: Paragraph1.1 (e)(2)(b)(2) states that overlay fabricationgrading units designed to be unflawed shall be separatedby unflawed overlay materialand unflawed base metal-to-overlay interfacefor at least I inch at both ends, ratherthan around its entire perimeter.

Alternative:.. base metal grading units, ten unflawed base metal grading units, five flawed overlay fabrication grading units, and ten unflawed overlay (b)(3) Detection sets shall be selected from Table VIII-S2-,1. The minimum fabrication grading units. For each type of grading unit, the set shall contain at detection sample set is five flawed base grading units, ten unflawed base least twice as many unflawed as flawed grading units. For initial procedure fa ed overa grading units, seten grading units, Fiveach ad ucntawd olerlayt t qualification, detection sets shall include the equivalent of three personnel grading units. For each type of grading unit, the set shall contain at least twice qualification sets. To qualify new values of essential variables, at least one as many unflawed as flawed grading units. personnel qualification set is required.

Basis: Clarifiedthe guidancefor initialprocedure qualificationsversus qualifying new values of essential variables.

(f) Sizing Specimen (1) The minimum number of flaws shall be ten. At least 30% of the flaws shall Alternative: (1) The...least 40% of the flaws shall be open to the inside be overlay fabrication flaws. At least 40% of the flaws shall be cracks open to surface. Sizing sets shall contain a distribution of flaw dimensions to assess Page 26 of 30

Request No. 07-GO-001 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR PDI PROGRAM:

FULL STRUCTURAL OVERLAID WROUGHT AUSTENITIC The Proposed Alternative to Supplement 11 Requirements PIPING WELDS the inside surface, sizing capabilities. For initial procedure qualification, sizing sets shall include the equivalent of three personnel qualification sets. To qualify new values of essential variables, at least one personnel qualification set is required.

Basis: Clarifiedthe guidancefor initialprocedurequalificationsversus qualifying new values of essential variables and is consistent with ld(1) above..

(3) Base metal cracking used for length sizing demonstrations shall be Alternative: (3) Base metal flaws used.. circumferentially.

oriented circumferentially. Basis: Clarifiedwording to be consistent with ld(1) above.

(4) Depth sizing specimen sets shall include at least two distinct locations Alternative: (4) Depth sizing specimen sets shall include at least two distinct where cracking in the base metal extends into the overlay material by at least locations where a base metal flaw extends into the overlay material by at least 0.1 inch in the through-wall direction. 0.1 inch in the through-wall direction.

Basis: Clarifiedwording to be consistent with ld(]) above.

2.0 Conduct of Performance Demonstration The specimen inside surface and identification shall be concealed from the candidate. All examinations shall be completed prior to grading the results and Alternative: The specimen ...prohibited. The overlay fabrication flaw test and presenting the results to the candidate. Divulgence of particular specimen the base metal flaw test may be performed separately.

results or candidate viewing of unmasked specimens after the performance Basis: Clarifiedwording to describeprocess.

demonstration is prohibited.

2.1 Detection Test.

Flawed and unflawed grading units shall be randomly mixed. Although the boundaries of specific grading units shall not be revealed to the candidate, the Alternative: Flawed... (base metal or overlay fabrication)..,-each specimen.

candidate shall be made aware of the type or types of grading units (base or Basis: Clarifiedwording similarto I (e)2 above..

overlay) that are present for each specimen.

2.2 Length Sizing Test (d) For flaws in base grading units, the candidate shall estimate the length of Alternative: (d) For... base metal grading ... base metal wall thickness.

that part of the flaw that is in the outer 25% of the base wall thickness. Basis: Clarifiedwordingfor consistency.

2.3 Depth Sizing Test.

Alternative: (a) The depth sizing test may be conducted separately or in For the depth sizing test, 80% of the flaws shall be sized at a specific location conjunction with the detection test.

identified to the candidate. For the remaining conjunction with the detection on flaws, surface the the regions of specimen of the each specimen containing a flaw to be sized shall be (b) When the depth sizing test is conducted in conjunction with the detection identflawsthe regions idofchspei condidataininghalflw d toe sized salmbeph test and the detected flaws do not satisfy the requirements of 1.1 (f), additional identified to the candidate. The candidate shall determine the maximum depth s shall be provided to the candidate. The regions containing a flaw to be sized shall be identified to the candidate. The candidate shall determine the I maximum depth of the flaw in each region.

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Request No. 07-GO-00 1 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR PDI PROGRAM:

FULL STRUCTURAL OVERLAID WROUGHT AUSTENITIC The Proposed Alternative to Supplement 11 Requirements PIPING WELDS (c) For a separate depth sizing test, the regions of each specimen containing a flaw to be sized shall be identified to the candidate. The candidate shall determine the maximum depth of the flaw in each region.

Basis: Clarifiedwording to better describeprocess.

3.0 ACCEPTANCE CRITERIA 3.1 Detection Acceptance Criteria Alternative: Examination procedures are qualified for detection when:

a. All flaws within the scope of the procedure are detected and the results of the performance demonstration satisfy the acceptance criteria of Table VIII-are $2-1 for false calls.

Examination procedures, equipment, and personnel qualified for detection when the results of the performance demonstration b. At least one successful personnel demonstration has been performed satisfy the acceptance criteria of Table Vlll-S2-1 for both detection and false meeting the acceptance criteria defined in (c).

calls. The criteria shall be satisfied separately by the demonstration results for c. Examination equipment and personnel are qualified for detection when the base grading units and for overlay grading units. results of the performance demonstration satisfy the acceptance criteria of Table VlII-S2-1 for both detection and false calls.

d. The criteria in (b) and (c) shall be satisfied separately by the demonstration results for base metal grading units and for overlay fabrication grading units.

Basis: Clarifiedwording to better describe the difference between procedure qualificationand equipment andpersonnel qualifications.

3.2 Sizing Acceptance Criteria (a) The RMS error of the flaw length measurements, as compared to the true Alternative: (a) The.. .base metal flaws is.. .position.

flaw lengths, is less than or equal to 0.75 inch. The length of base metal Basis: Clarifiedwording to be consistent with ld(1) above.

cracking is measured at the 75% through-base-metal position.

Alternative: This requirement is omitted.

Basis: The requirementfor reportingall extensions of crackinginto the (b) All extensions of base metal cracking into the overlay material by at least overlay is omittedfrom the PDIProgram because it is redundantto the RMS 0.1 inch are reported as being intrusions into the overlay material, calculationsperformed in paragraph3.2(c) and its presence adds confusion and ambiguity to depth sizing as requiredby paragraph3.2(c). This also makes the weld overlay program consistent with the supplement 2 depth sizing criteria Page 28 of 30

Request No. 07-GO-00I Enclosure 1 Table A3 Modifications to Code Case N-638-1 Code Case N-638-1 Modification/Basis Modification: The maximum area of an individual weld based on the finished surface over the ferritic materialwill not exceed 500 square Weld Area inches. Depth in N-638-1 refers to depth of the repair cavity and is not 1.0(a) The maximum area of an individual weld applicable to the weld overlays described in this request for relief.

based on the finished surface shall be 100 sq. inch, Basis: The maximum area of the WOL for the surge line nozzle will be and the depth of the weld shall not be greater than approximately 120 sq-in over the ferritic material. An ASME white one-half of the ferritic base metal thickness. paperproviding technicaljustification for extending the area limitation to 500 sq. inch was published by the ASME Code Committees. As previously noted in the text, this white paperhas been submitted to the NRC for their use.

Examination (Referenced below in 4.0(b) para. 1.0(d) Prior to welding the area to be welded and a band around the area of at least 11/2 times the component thickness or 5inch, whichever is less shall be at least 50'F.)

4.0(b) The final weld surface and a band around the area defined in Modification: Of the required examinations of 4.0(b) only the required para. 1.0 (d) shall be examined using a surface and ultrasonic methods liquid penetrant examination will be performed. In lieu of the required when the completed weld has been at ambient temperature for at least ultrasonic examination, the ultrasonic examination will be in 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. The ultrasonic examination shall be in accordance with accordance with N-504-2 and Appendix Q.

Appendix 1.3 Basis: For the applicationof the weld overlay repairaddressed in this request the appropriateexamination methodologies and volumes are NRC Condition for N638-1 provided in Code Case N-504-2 and NonmandatoryAppendix Q Code Case N-638-1 applies to any type of welding where a temper bead UT examinations shall be demonstrated for the repaired volume using technique is to be employed and is not specifically written for a weld representative samples which contain construction type flaws. The overlay repair. As described in the text of this request, the proposed acceptance criteria of NB-5330 of Section III edition and addenda inspection will provide equal or better assurance of the soundness of approved in 10 CFR 50.55a apply to all flaws identified within the the weld overlay and surrounding material.

repaired volume.

3 Refer to the 1989 Edition with the 1989 Addenda and later Editions and Addenda Page 29 of 30

Request No. 07-GO-001 Enclosure 1 Table A3 Modifications to Code Case N-638-1 Code Case N-638-1 Modification/Basis Modification: Preheat and interpass temperatures for the weld overlay will be measured using a temporarily attached or contact pyrometer.

Readout of the temperature may be local using a manual method or remotely monitored by the operator. Interpass temperature control 4.0(c) requires temperature monitoring by welded thermocouples per required by Code Case N-638-1 will be maintained.

IWA-461 0(a) Basis: The proposed technique is faster and does not compromise collection of requireddata. The proposed technique provides data equivalent to that obtained from weld attached thermocouples to monitor interpass temperatureduring welding. As noted earlierin this document, the NRC has previously approved this type of temperature data collection.

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