ML072620149

Fourth Ten Year Inservice Inspection Interval Request for Relief No. 07-ON-004

ML072620149
Person / Time
Site:	Oconee
Issue date:	09/13/2007
From:	Brandi Hamilton Duke Energy Carolinas, Duke Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML072620149 (29)

Text

Duke BRUCE HHAMILTON Vice President Pd Energyo Oconee Nuclear Station Duke Energy Corporation ON01 VP / 7800 Rochester Highway Seneca, SC 29672 864 885 3487 864 885 4208 fax bhhamilton@duke-energy.com September 13, 2007 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Subject:

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

Oconee Nuclear Station, Units 1, 2, 3 Docket Nos. 50-269,-270,-287 Fourth Ten Year Inservice Inspection Interval Request for Relief No. 07-ON-004 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, Rules for Inservice Inspection of Nuclear Power Plant Components, for the Oconee Nuclear Station, Units 1, 2, and 3.

This proposed alternative approach is to support application of full structural weld overlays associated with the inspection and mitigation of Alloy 600/82/182 welds within the Reactor Coolant System (RCS) and will provide an acceptable level of quality and safety. The weld overlays addressed by this request for relief are on the Decay Heat Removal (DHR) line to Hot Leg Nozzle welds in the RCS. These welds are not in the scope of Duke's commitment letter of February 22, 2007 (ADAMS Accession Number ML070600169) in which Duke committed to mitigate specific Pressurizer welds by the end of 2007 per MRP-139.

This relief request is needed to support the Oconee Unit 3 Fall 2007 refueling outage (3EOC23) scheduled to start October 27, 2007. Duke requests verbal approval of this relief request prior to that date. However, Duke recognizes that this request provides a relatively short period for review. Following the overlay, NRC verbal approval must be granted before the DHR line can be returned to

.service. The current schedule indicates DHR return to service on November 29, 2007 to support re-entry into Mode 6 (refueling mode). This relief is also intended to apply to DHR line overlays on Oconee Units 1 and 2, which are scheduled for the subsequent outages on each unit in 2008.

www. duke-energy. com

U. S. Nuclear Regulatory Commission September 13, 2007 Page 2 This request is similar to requests for relief 06-ON-004 and 07-ON-001 which were approved by letter dated August 6, 2007 (ADAMS Accession Number ML071280781).

This submittal contains two commitments to provide additional data related to the weld overlays. The first commitment is that Duke will submit, prior to entry into Mode 6 from the Oconee Unit 3 outage in the fall of 2007, 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. The second commitment is that Duke will submit, within 14 days from completion of Ultrasonic Test (UT) examinations of the DHR line weld overlay on each unit, a report that summarizes the results of the UT examinations on that overlay. These commitments are the only regulatory commitments contained in this relief request.

If there are any questions or further information is needed you may contact R. P.

Todd at (864) 885-3418.

B. H. Hamilton Site Vice President Enclosure

Request No. 07-ON-004 Enclosure I ProposedAlternative In Accordance with 10 CFR 50.55a(a)(3)(i)

- Alternative ProvidesAcceptable Level of Quality and Safe4, -

Duke Energy Corporation Oconee Units 1, 2 & 3 Request for Alternative 07-ON-004 CONTENTS 1.0 ASME CODE COMPONENTS AFFECTED ............................................................................. 2 2.0 APPLICABLE CODE EDITION AND ADDENDA .................................................................. 2 3.0 APPLICABLE CODE REQUIREMENTS ................................................................................. 2 4.0 REASON FOR THE REQUEST ................................................................................................ 3 5.0 PROPOSED ALTERNATIVES AND BASIS FOR USE .......................................................... 3 6.0 WELD OVERLAY DESIGN AND VERIFICATION ............................................................. 13 7.0 DURATION OF THE PROPOSED ALTERNATIVES .......................................................... 14 8.0 PRE C E DE N T S ..... ........................................................................................................................... 14 9.0 R E FERE N C E S ............................................................................................................................... 15 10.0 C O N C L U SIO N .............................................................................................................................. 15 A T TA C H M EN T I ....................................................................................................................................... 16 Figure Al: Typical Hot Leg Decay Heat Nozzle Overlay .................................................... 17 Table Al Modifications To Code Case N-504-2 and Corresponding Non-Mandatory Appendix Q R equirem ents ........................................................................................................ 18 Table A2 Alternatives to Appendix VIII, Supplement 11 ............................................... 20 Table A3 Modifications to Code Case N-638-1 ................................................................ 26 List of Figures Figure 5.1 Residual Stress Distribution from ASME White Paper (see Text) ................... 9 Figure 5.2 Calculated Residual Stress Distribution for Oconee (see Text) .......................................... 10 Figure 5.3 Phased array UT coverage for ONS hot leg decay heat nozzle ........................................ 12 Page 1 of 27

Request No. 07-ON-004 Enclosure 1 1.0 ASME CODE COMPONENTS AFFECTED System: Reactor Coolant System Component Number:

.OcT6fi Description..,.',. si Weld Num"ber C.e....

RC Pipe Decay heat line to Hot leg 12 NPS 1LP-140-1A(weld) CS Nozzle/Alloy 82-182 butter/

Nozzle 1PHB- 17(butter) Alloy 82-182 weld/SS pipe Ocone. [mDes ition J Size j Weld Number* Comment"'

[Unit 2' RC Pipe Nozzle heat line to Hot leg Decay 12 NPS 2-53A-10-1OA(weld) 12PHA-17(butter) CS Nozzle/Alloy Alloy 82-182 82-182 weld/SS butter/

pipe Oconee... Des c rip ftion j S*e: Weld Number '.comment(])

RC Pipe Decay heat line to Hot leg 12 NPS 3-53A-18-11 (weld) CS Nozzle/Alloy 82-182 butter/

Nozzle 3PHA-17(butter) Alloy 82-182 weld/SS pipe (1) CS = SA-105 Gr 2 - Hot leg nozzle.

SS = Type 316 austenitic stainless steel Code Class: Class 1 Examination Category: B-J Code Item Number: B9. 11 2.0 APPLICABLE CODE EDITION AND ADDENDA Inservice Inspection:

ASME Boiler and Pressure Vessel Code,Section XI, 1998 Edition through 2000 Addenda Design and Fabrication:

USAS B31.7, Code for Pressure Piping, Nuclear Power Piping, dated February, 1968 and as corrected for Errata under date of June, 1968. The decay Heat Removal Drop-line was reanalyzed to ASME Section III, Subsection NB, 1983 edition, no addenda.

Duke Welding Program:

ASME Boiler and Pressure Vessel Code, Section I1, 1989 Edition No Addenda 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" Page 2 of 27

Request No. 07-ON-004 Enclosure 1 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 that are subjected to higher operating temperatures. Structural weld overlays have been used for several years 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 Oconee hot legs; 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. Some of 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. Rather than risk multiple cycles of inspection and modification, Duke is proposing to take a proactive approach to apply a preemptive full structural weld overlay (PWOL) to the dissimilar metal welds of the hot leg 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 Oconee Units 1, 2, & 3 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 IOCFR 50.55a(a)(3)(i), an alternative to the requirements listed in Section 3.0 is requested on the basis that the proposed alternative will provide an acceptable level of quality and safety. Attachment 1, 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 welds identified in Section 1.0. The overlays will extend around the full circumference of the nozzle to piping welds, as illustrated in Figure Al of . The full structural weld overlays are sized to satisfy the 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. 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 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 one-half inch beyond the susceptible weld and includes the outer Page 3 of 27

Request No. 07-ON-004 Enclosure 1 25% of the original wall thickness. The length of the PWOL is extended and blended into the carbon steel (CS) nozzle outer diameter 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.

ASME Boiler and Pressure Vessel Code Section XI 1998 Edition through 2000 Addenda (i.e. the code edition applicable to the fourth inspection interval for Units 1, 2 and 3 and for which relief is requested) requires performance of NDE and specifies the methods and acceptance criteria. 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.

The PWOL will be applied over portions of the CS nozzles. The Construction Code requires either pre-heat or post-weld heat treatment after welding depending on the carbon content or base material thickness. As an alternative to pre-heat or post-weld heat treatment, the overlay will be implemented in accordance with Code Case N-638-1 with the modifications noted in Table A3 of 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 173 square inches for the hot leg decay heat nozzles.

An ASME white paper describes the technical justification for allowing increased overlay areas up to 500 square inches [Ref. 7]. . 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 any continued degradation. The revised limit far exceeds the estimated 173 square inches to be applied to the Oconee hot leg decay heat 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:

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Request No. 07-ON-004 Enclosure 1 (a) Residual Stresses - Using as an example a BWR Feedwater Nozzle, the white paper cites EPRI sponsored analyses [7] of an overlay that just equaled 100 square inches coverage over the ferritic steel base metal. 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 [7] was roughly similar to the ONS hot leg 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 ONS hot leg decay heat nozzles are shown in Figure 5.2. It is seen from this figure that the ONS decay heat nozzle weld overlay design, with its approximately 173 square inches coverage over the ferritic steel base metal, creates favorable compressive residual stresses on the inside surface of the nozzle.

(b) HAZ Tempering - The white paper cites past programs which have demonstrated that temper bead welding using automatic GTAW provides adequate tempering of the HAZ in P-I and P-3 materials and does not degrade strength or fracture toughness for temper bead weld overlays. 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 -119 square inches of the low alloy steel nozzle (approximately the same as the ONS hot leg decay heat 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 material similar to that for the ONS hot leg decay heat 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 low alloy steel 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 soak specified in the Code is intended as post hydrogen bake out 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. Extensive research has been performed by EPRI (Technical Report 1013558, Temper Bead Welding Applications -

48 Hour Hold Requirements for Ambient Temperature Temper Bead Welding) which provides a technical basis for starting the 48-hour hold after completing the third temper bead weld layer rather than waiting for the weld overlay to cool to ambient temperature. The hold time required by N-638 will be implemented in accordance with this latest research. This approach has been previously reviewed and approved by the NRC [Ref. 11 ]. 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 have been proven in practice by extensive field experience with temper bead weld overlays, with 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 Page 5 of 27

Request No. 07-ON-004 Enclosure 1 applications. It is seen from this table that the original DMW weld overlay was applied over 20 years ago, and WOLs with low alloy steel coverage in the 100 square inches range have been in service for 5 to 15 years. Several overlays have been applied with low alloy steel 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, 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 carbon steel material containing the weld HAZ and a volume of unaffected base material beyond the HAZ (see Figure 5.3).

Code Case N-638-1 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 ONS, this technique will be used to apply a non-ferritic overlay to the 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 Figure 5.3, 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 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.

Page 6 of 27

Request No. 07-ON-004 Enclosure 1 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 VIII, Supplement 11, 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 HI 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. Precedents 8 and 9).

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Request No. 07-ON-004 Enclosure 1 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.

" 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, 2

• the type and nature of the indications 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.

Subsequent Inservice examination of the structural weld overlays on the overlaid nozzles 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 Oconee hot leg decay heat nozzle overlays 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.

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Request No. 07-ON-004 Enclosure I Residual Axial Stress Along Inside Wall Length of 100 in^2 Weld Overlay 0

1010

-165

-20

-25 --o- 100 inA2 Extended

-301

-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

-6 Length of 100 In^2 Weld Overlay

-10 CS

./

0-20 0

-25 -25 ' 9 - '

-30

-e- 100 inA2

--- Extended

-3 5 .. . . . . . . . . .

-7 -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)

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Request No. 07-ON-004 Enclosure 1 ID Surface Axial Residual Stress Post IDweld repair 70°T-* Post weld overlay 70°F Post weld overlay 604°F+2200psig 100 Nozzle Side WELD REGION 80 60 ____

40 Un o20 0)

-20_____

-40

-5 -4 -3 -2 -1 0 1 2 3 4 5 Distance from ID Weld Repair Centerline (in)

ID Surface Hoop Residual Stress

.- Post ID weld repair 70°F - Post weld overlay 70°F

- Post weld overlay 604'F+2200psig 80 60 40 "g 20 0

-20

-40

-60

-5 -4 -3 -2 -1 0 1 2 3 4 5 Distance from ID Weld Repair Centerline (in)

Figure 5.2 Calculated Residual Stress Distribution for Oconee (see Text)

Page 10 of 27

Request No. 07-ON-004 Enclosure 1 Table 5.1- Dissimilar Metal Weld Overlay Experience Nozzle Approx. low alloy Date Plant Component Diameter (in) steel Coverage (in2 )

Spray nozzle 4.5 30 Safety/relief nozzles 4.5 30 April 2007 Oconee Unit 2 PZR surge nozzle 11.5 125 Hot leg surge nozzle 11.5 70 Spray nozzle 6 33 March 2007 McGuire Unit 1 Safety/relief nozzles 8 55 Surge nozzle 15 120 Spray nozzle 6 33 September 2006 McGuire Unit 2 Safety/relief nozzles 8 55 Surge nozzle 15 120 Spray nozzle 6 33 December 2006 Catawba Unit 1 Safety/relief nozzles 8 55 Surge nozzle 15 120 Spray nozzle 4.5 30 Safety/relief nozzles 4.5 30 October 2006 Oconee Unit I PZR surge nozzle 11.5 125 Hot leg surge nozzle 11.5 70 April 2006 Davis Besse Hot leg drain nozzle 4 16 PZR spray nozzle 8 50 February 2006 SONGS Unit 2 safety/relief nozzles 6 28 November2005 Kuosheng Unit 2 Recirculation outlet 22 250 nozzle April 2004 Susquehanna Unit 1 Recirc.

Rcr.ote inlet nozzle oze2 12 100 2

Recirc. outlet nozzle 28 325 November 2003 TMI Unit I Surge line nozzle 11.5 75 October 2003 Pilgrim Core C~ spray nozzle eunnzl 10 50 CRD return nozzle 5 20 Core spray nozzle 10 50 October 2002 Peach Bottom Units 2 & 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 2 Feedwater nozzle 12 100 March 1996 Brunswick Units 1 & 2 Feedwater nozzle 12 100 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 11 of 27

Request No. 07-ON-004 Enclosure 1 Figure 5.3 Phased array UT coverage for ONS hot leg decay heat nozzle.

(Lack of coverage indicated by cross hatch area)

Page 12 of 27

Request No. 07-ON-004 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 analyses performed are bounding for all three Oconee units and demonstrate the modifications are long-term repairs for mitigation of PWSCC at each of the locations considered in the analysis. 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 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.

1. Nozzle specific stress analyses established a residual stress profile in the nozzle. Severe ID weld repairs were assumed that effectively bound any actual weld repairs to the nozzle. The weld overlay was subsequently applied to simulate the final residual stress profile. Post weld overlay residual stresses at normal operating conditions were 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 were performed to predict crack growth with the assumption 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 due to PWSCC as well as due to fatigue crack growth in the original DMW was evaluated. The crack growth analyses considered all design loads and transients, plus the post weld overlay residual stress distributions. These analyses demonstrate that cracks will not grow beyond the allowable Code depth of 75% of the original weld plus new overlay thickness for the time period until the next scheduled inservice inspection.

3. The analyses demonstrate that application of the weld overlays does not impact the qualification of the existing nozzle documented in the Stress Reports. ASME Code,Section III stress and fatigue criteria are met, as detailed in ASME Code Case N-504-2.

4. Shrinkage will be measured during the overlay application. Shrinkage stresses arising from the weld overlays will be demonstrated to have no adverse effect at other locations in the piping 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 has been evaluated and is acceptable (Oconee calculation OSC-8745.06).

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.

Summaries of the results of the bounding analyses for the items listed in 1 through 3 above will be completed and submitted to the NRC prior to entry into mode 6 during the restart of Unit 3 after the EOC 23 (Fall 2007) outage. Items 4 through 6 will be completed prior to entry into mode 6 during the restart Page 13 of 27

Request No. 07-ON-004 Enclosure 1 of each of the Oconee Units. All analyses and data will be available for review by the NRC resident or field inspectors as needed.

7.0 DURATION OF THE PROPOSED ALTERNATIVES These structural weld 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. The overlays will be performed during the fourth inspection interval for Oconee Unit 1, Unit 2 and Unit 3. The interval start and end dates are:

Oconee Unit 1 Start: 01/01/2004 End: 07/14/2013 Oconee Unit 2 Start: 09/09/2004 End: 09/09/2014 Oconee Unit 3 Start: 01/02/2005 End: 12/16/2014 The Code of Record for inservice inspection during these intervals is the ASME Boiler and Pressure Vessel Code,Section XI, 1998 Edition through 2000 Addenda for all units.

8.0 PRECEDENTS I. 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. MC 1201)," 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 I - 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 I

- 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, approved August 6, 2007.

9. Duke Energy Corporation, Request for Relief 06-GO-001, for McGuire Unit 2, approved July 25, 2007.

Page 14 of 27

Request No. 07-ON-004 Enclosure 1

10. Duke Energy Corporation, Request for Relief 06-GO-001, for Catawba Unit 1, approved July 25, 2007.

9.0 REFERENCES

(1) ASME Code,Section XI, 1998 Edition through 2000 Addenda, 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 I , February 13, 2003.

(6) ASME Code Case N-638-3, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,Section XI, Division 1 , April 18, 2006 & accompanying white paper.

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

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

(8) "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.

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

(10) 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.

(11) Safety Evaluation By The Office Of Nuclear Reactor Regulation Related To ASME Code,Section XI, Alternatives For Union Electric Company Callaway Plant, Unit 1, Docket No. 50-483, July 10, 2007.

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 15 of 27

Request No. 07-ON-004 Enclosure 1 ATTACHMENT 1 CONTENTS Figure Al Hot Leg Decay Heat Nozzle Weld Overlay 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 16 of 27

Request No. 07-ON-004 Enclosure 1 SA-I105 GR 2 DECAY HEAT NOZZLE Figure Al: Typical Hot Leg Decay Heat Nozzle Overlay Page 17 of 27.

Request No. 07-ON-004 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 Modification. Code Case N-504-2 will be used for weld overlay repairs to the ferritic base material and nickel alloy weld as well as the austenitic stainless steel Reply. It is the opinion of the Committee that, in lieu of the requirements of base material.

IWA-4120 in Editions and Addenda up to and including the 1989 Edition with Basis: Code Case N-504-2 is acceptedfor use along with Nonmandatoty the 1990 Addenda, in IWA-4170(b) in the 1989 Edition with the 1991 Addenda Appendix Q in the currentNRC Regulatory Guide 1.147 Rev. 14. For the weld up to and including the 1995 Edition, and in IWA-4410 in the 1995 Edition with overlay of the identified welds at Oconee Units 1, 2 & 3 the base materialwill be the 1995 Addenda and later Editions and Addenda, defect in austenitic stainless ferritic materialwith existing nickel alloy weld metal to which an austenitic steel piping may be reduced to a flaw of acceptable size in accordance with IWB- stainless steel pipe is welded Industry operationalexperience has shown that 3640 from the 1983 Edition with the Winter 1985 Addenda, or later Editions and PWSCC in Alloy 82/182 will blunt at the interface with stainlesssteel base metal, Addenda, by deposition of weld reinforcement (weld overlay) on the outside ferritic base metal, or Alloy 52/52M/52MS weld metal. The 3600 structuralweld surface of the pipe, provided the following requirements are met. [Essentially overlay will controlgrowth in any PWSCC crack and maintain weld integrity.

same as Scope of Appendix Q]: The weld overlay will induce compressive stress in the weld, thus impeding growth of any reasonablyshallow cracks. Furthermore,the overlay will be sized to meet all structuralrequirements independent 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 ERAriCrFe-7(Alloy 52 UNS N06052). This weld metal is assignedF43 by ASME.

The requirements of ASME Section Ill, NB-2400 will be applied to allfiller material.The chromium content ofAlloy 52M/MS is 28-31.5%, identical to that ofAlloy 52. The main difference in Alloy 52 vs. Alloy 52M/MS is a higher (b) Reinforcement weld metal shall be low carbon (0.035% max.) austenitic Niobium content (0.5-1 %). The difference in chemical composition between stainless steel applied 3600 around the circumference of the pipe, and shall be Alloy 52 andAlloy 52M/MS improves the weld-ability of the materialand pins deposited in accordance with a qualified welding procedure specification the grain boundariesthus preventingseparationbetween the grains and hot identified in the Repair Program. [Same as Q-2000(a)]

tearingduring weld puddle solidification. These filler materialswere selected for their improved resistanceto P WSCC. Alloys 52 and 52M/MS contain about 30% chromium that imparts excellent corrosionresistance. The existingAlloy 82/182 weld and the Alloy 52M/52MS overlay are nickel base and have ductile propertiesand toughness similar to austeniticstainless steelpiping welds at pressurizedwater reactoroperatingtemperature. These filler materials are suitablefor welding over the ferritic nozzle, nickel alloy weld or base material, and the austenitic stainless steel safe end or pipe components.

Page 18 of 27

Request No. 07-ON-004 Enclosure I Table Al Modifications To Code Case N-504-2 and Corresponding Non-Mandatory Appendix Q Requirements Code Case N-504-2 Modification/Basis (e) The weld reinforcement shall consist of a minimum of two weld layers Modification: Delta ferrite (FN) measurements will not be performed for weld having as-deposited delta ferrite content of at least 7.5 FN. The first layer of weld odificaion de f All ) measurems wll notb f f metal with delta ferrite content thedesig of least wel reinfrcemen thickess. 7.5 FN shall constitute the first layer of overlay repairs made of Alloy 52/52M/52MS weld metal.

the weld reinforcement design thickness. Aternatvelyairst:lyersdosatflestloyBais:2Weds2of Alternatively, first layers of at least 5 lary51500/Sausaren00%iauteniticandacntain ferrite dlue to the high nickel composition (approximately 60% nickel). oddelt FN may be acceptable based on evaluation. ISame as Q-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) of the weld Pressure Testing overlay will be performed consistent with ASME IWA-4540(a)(2), as modified (h) The completed repair shall be pressure tested in accordance with IWA-5000. by Nonmandatory Appendix Q.

If the flaw penetrated the original pressure boundary prior to welding, or if any Basis: Application of IWA-4540(a)(2)for a system leakage test in lieu of a evidence of a flaw penetrating the pressure boundary is observed during the system hydrostatic test requiresperformance of NDE in accordancewith the methods and acceptance criteriaof the applicable Subsection of the 1992 Edition welding operation, a system hydrostatic test shall be performed in accordance of ASME Section III. ASME Section III Subsection NB Article 5000for with IWA-5000. If the system pressure boundary has not been penetrated, a Examination does not address the structuralweld overlay type configuration.

system leakage, inservice, or functional test shall be performed in accordance Nxamrequirements of Nonsandatory A end ovwll befollwefrathe with IWA-5000. The NDE requirementsof Nownandatory Appendix Q will be f!!lowed for the requiredNDE in lieu ofASME Section III. Code Case N-504-2 and Nonmandatory Appendix Q provide appropriateexamination requirements includingexamination volume, acceptance criteria,and examinationmethods per Appendix VIII.

Page 19 of 27

Request No. 07-ON-004 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 Appendix V1ii 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 VI11 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 Tri-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 FULL PDI PROGRAM:

STRUCTURAL OVERLAID WROUGHT AUSTENITIC PIPING The Proposed Alternative to Supplement 11 Requirements 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 and overlay thicknesses. They shall include the minimum and maximum Alternative: (b) The specimen set shall include specimens with overlays not thicker nominal pipe diameters for which the examination procedure is applicable. Pipe than 0.1 inch more than the minimum thickness, nor thinner than 0.25 inch of the diameters within a range of 0.9 to 1.5 times a nominal diameter shall be considered maximum nominal overlay thickness for which the examination procedure is equivalent. If the procedure is applicable to pipe diameters of 24 inch or larger, the specimen set must include at least one specimen 24 inch or larger but need not include applicable.

Basis: To avoid confuion, the overlay thickness tolerance contained in thle last the maximum diameter. The specimen set must include at least one specimen with fus ythickness within -0.1 inch to +0.25 inch of the maximum nominal overlay sentence was reworded and the phrase "and the remaindershall be alternativeflaws" overlay for withe -0.1 is applicable. was added to the next to last sentence in paragraph1.1 (d) (1).

thickness for which the procedure is applicable.

(d) Flaw Conditions Alternative: (1) ... must be in or... intentional overlay fabrication flaws shall not interfere with ultrasonic detection or characterization of the base metal flaws.

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

detection or characterization of the cracking. Specimens containing IGSCC shall be (a) The use of alternative flaws shall be limited to when the implantation of cracks used when available. 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 mnetalflaws be cracks. Implanting a crack

Request No. 07-ON-004 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR FULL STRUCTURAL OVERLAID WROUGHT AUSTENITIC PIPING PDI PROGRAM:

The Proposed Alternative to Supplement 11 Requirements WELDS requires excavation of the base materialon at least one side of theflaw. While this may be satisfactoryforferriticmaterials, it does not produce a useable axialflaw in austenitic materials because the sound beam, which normallypasses only through base material, must now travel through weld materialon at least one side, producingan unrealisticflaw response. To resolve this issue, the PD!program revised this paragraphto allow use of alternativeflaw mechanisms under controlledconditions.

For example, alternativeflaws shall be limited to when implantationof cracks precludes obtainingan 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 theflaws in the detection and sizing test shall be cracks and the remaindershall be alternativeflaws.

To avoid confusion, the overlay thickness tolerance contained in paragraph1. 1(b) last sentence, was rewordedand the phrase "andthe remaindershall be alternativeflaws" was added to the next to last sentence. Paragraph1.1(d)(1) includes the statement that intentionaloverlayfabricationflawsshall not interfere with ultrasonic detection or characterizationof the base metal 1Taws.

I -

(e) Detection Specimens Alternative: (1) At least 20% but less than 40% of the base metal flaws shall be oriented within +/-200 of the pipe axial direction. The remainder shall be oriented circumferentially. Flaws shall not be open to any surface to which the candidate has (1) At least 20% but less than 40% of the flaws shall be oriented within +/-20' of the physical or visual access.

pipe axial direction. The remainder shall be oriented circumferentially. Flaws shall not Basis: The requirementforaxially orientedoverlayfabricationflaws was excluded be open to any surface to which the candidate has physical or visual access. The rules from the PDIProgramas an improbable scenario. Weld overlays are typically applied of IWA-3300 shall be used to determine whether closely spaced flaws should be treated using automated GTA W techniques with thefiller metal appliedin a circumferential as single or multiple flaws. direction. Because resultantfabrication induced discontinuitieswould also be expected to have major dimensions oriented in the circumferentialdirection axial overlay fabricationflaws are unrealistic. The requirementfor using IWA-3300 for proximity flaw evaluation was excluded; instead indicationswill be sized basedon their individualmerits.

4 Alternative: (2) Specimens shall be divided into base metal and overlay fabrication (2) Specimens shall be divided into base and overlay grading units. Each specimen grading units. Each specimen shall contain one or both types of grading units. Flaws shall contain one or both types of grading units. shall not interfere with ultrasonic detection or characterization of other flaws.

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

Page 21 of 27

Request No. 07-ON-004 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR FULL PDI PROGRAM:

STRUCTURAL OVERLAID WROUGHT AUSTENITIC PIPING The Proposed Alternative to Supplement 11 Requirements WELDS 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 the original weld crown and a (a)(1) A base grading unit shall include at least 3 inch of the length of the overlaid minimum of 0.50" of the adjacent base material.

weld. The base grading unit includes the outer 25% of the overlaid weld and base metal Basis: The phrase "and base metal on both sides, "was inadvertently included in the on both sides. The base grading unit shall not include the inner 75% of the overlaid descriptionof a base metal gradingunit, The PDlprogramintentionally excludes this weld and base metal overlay material, or base metal to-overlay interface. requirement because some of the qualificationsamples includeflaws on both sides of the weld. To avoid confusion several instances of the term "cracks" or "cracking" were changedto the term 'flaws" because of the use of alternative Flaw mechanisms.

Modified to requirethat a base metal grading unit include at leastl inch of the length of the overlaidweld, ratherthan 3 inches.

(a)(2) When base metal cracking penetrates into the overlay material, the base grading Alternative: (a)(2) When base metal flaws penetrate into the overlay material, the base (nitsha)(2 Whcluen baseoverla metal c n p t inthof theoerlayk lateona, Thease gradiongo metal grading unit shall not be used as part of any overlay fabrication grading unit.

unit shall include the overlay metal within 1 inch of the crack location. This portion of Basis: Substitutedterms provide clarificationand are consistent with ld(1) above. The the overlay matenial shall not be used as part of any overlay grading unit. PDIprogram adjustsfor this conservative changefor excluding this type grading unit.

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

overlaid weld and base metal shall exist on either side of the base grading unit. The Basis: Modified to requiresufficient unflawed overlaid weld and base metal to exist on segment of weld length used in one base grading unit shall not be used in another base all sides of the grading unit to prechlde interferingreflectionsfrom adjacentflaws, grading unit. Base grading units need not be uniformly spaced around the specimen. rather than the I inch requirement.

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 metal-to- Basis: The PDIprogram reduces the base metal-to-overlay interface to at least 1 inch overlay interface of at least 6 in'. The overlay grading unit shall be rectangular, with (in lieu of a minimum of 2 inches) and eliminates the minimum rectangulardimension.

minimum dimensions of 2 inch This criterionis necessary to allow use of existing examination specimens that were fabricatedin order to meet NRC Generic Letter 88-01. This criterionmay be more challengingthan the ASME Code because of the variabilityassociatedwith the shape of the gradingunit.

(b)(2) An overlay grading unit designed to be unflawed shall be surrounded by Alternative: (b)(2) Overlay fabrication grading units designed to be unflawed shall be unflawed overlay material and unflawed base metal-to-overlay interface for at least 1 separated by unflawed overlay material and unflawed base metal-to-overlay interface Page 22 of 27

Request No. 07-ON-004 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR FULL STRUCTURAL OVERLAID WROUGHT AUSTENITIC PIPING PDI PROGRAM:

The Proposed Alternative to Supplement 11 Requirements WELDS inch around its entire perimeter. The specific area used in one overlay grading unit for at least 1 inch at both ends. Sufficient unflawed overlaid weld and base metal shall shall not be used in another overlay grading unit. Overlay grading units need not be exist on both sides of the overlay fabrication grading unit to preclude interfering spaced uniformly about the specimen. reflections from adjacent flaws. The specific area used in one overlay fabrication grading unit shall not be used in another overlay fabrication grading unit. Overlay fabrication grading units need not be spaced uniformly about the specimen.

Basis: Paragraph1.1 (e)(2)(b)(2) states that overlay fabricationgradingunits designed to be unflawed shall be separatedby unflawed overlay,materialand unflanved base metal-to-overlay interfacefor at least I inch at both ends, ratherthan aroundits entireperimeter.

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

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

(f) Sizing Specimen Alternative: (1) The...least 40% of the flaws shall be open to the inside surface. Sizing (1) The minimum number of flaws shall be ten. At least 30% of the flaws shall be sets shall contain a distribution of flaw dimensions to assess sizing capabilities. For overlay fabrication flaws. At least 40% of the flaws shall be cracks open to the inside initial procedure qualification, sizing sets shall include the equivalent of three surface. personnel qualification sets. To qualify new values of essential variables, at least one personnel qualification set is required.

Basis: Clarifiedthe guidancefor initialprocedure qualificationsversus qualifying new values of essential variablesand is consistent with ld(1) above..

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

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

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

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

2.0 Conduct of Performance Demonstration The specimen inside surface and identification shall be concealed from the candidate. Alternative: The specimen ...prohibited. The overlay fabrication flaw test and the base Page 23 of 27

Request No. 07-ON-004 Enclosure 1 Table A2 Alternatives to Appendix VIII, Supplement 11 SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR FULL STRUCTURAL OVERLAID WROUGHT AUSTENITIC PIPING PDI PROGRAM:

WELDS The Proposed Alternative to Supplement 11 Requirements All examinations shall be completed prior to grading the results and presenting the metal flaw test may be performed separately.

results to the candidate. Divulgence of particular specimen results or candidate viewing Basis: Clarifiedwording to describeprocess.

of unmasked specimens after the performance 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 candidate shall be Alternative: Flawed... (base metal or overlay fabrication).. .each specimen.

made aware of the type or types of grading units (base or overlay) that are present for Basis: Clarifiedwording similarto I(e)2 above..

each specimen.

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

of the flaw that is in the outer 25% of the base wall thickness. Basis: Clarifiedwordingforconsistency.

2.3 Depth Sizing Test.

Alternative: (a) The depth sizing test may be conducted separately or in conjunction with the detection test.

(b) When the depth sizing test is conducted in conjunction with the detection test and For the depth sizing test, 80% of the flaws shall be sized at a specific location on the the detected flaws do not satisfy the requirements of 1.1 (f), additional specimens shall surface of the specimen identified to the candidate. For the remaining flaws, the regions be provided to the candidate. The regions containing a flaw to be sized shall be of each specimen containing a flaw to be sized shall be identified to the candidate, The identified to the candidate. The candidate shall determine the maximum depth of the candidate shall detenrnine the maximum depth of the flaw in each region. flaw in each region.

(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:

Examination procedures, equipment, and personnel are a. All flaws within the scope of the procedure are detected and the results of the qualified for detection when the results of the performance demonstration satisfy the performance demonstration satisfy the acceptance criteria of Table VIII-S2-1 for false acceptance criteria of Table VIII-S2-1 for both detection and false calls. The criteria calls.

shall be satisfied separately by the demonstration results for base grading units and for b. At least one successful personnel demonstration has been performed meeting the overlay grading units. acceptance criteria defined in (c).

c. Examination equipment and personnel are qualified for detection when the results of the performance demonstration satisfy the acceptance criteria of Table Vlll-S2-1 for both detection and false calls.

Page 24 of 27

Request No. 07-ON-004 Enclosure I Table A2 Alternatives to Appendix VIII, Supplement 11 SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS FOR FULL PDI PROGRAM:

STRUCTURAL OVERLAID WROUGHT AUSTENITIC PIPING The Proposed Alternative to Supplement 11 Requirements WELDS

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 flaw Alternative: (a) The.. base metal flaws is... position.

lengths, is less than or equal to 0.75 inch. The length of base metal cracking is Basis: Clarified wording to be consistent with ld(J) above.

measured at the 75% through-base-metal position. Basis:_Clarifiedwordingtobeconsistentwithld(!)_above.

Alternative: This requirement is omitted.

(b) All extensions of base metal cracking into the overlay material by at least 0.1 inch Basis: The requirementfor reportingall extensions of cracking into the overlay is are reported as being intrusions into the overlay material. omittedfrom the PDIProgram because it is redundant to the RMS calculations performed 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 25 of 27

Request No. 07-ON-004 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 decay heat nozzle will and the depth of the weld shall not be greater than be approximately 173 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 paper has been submitted to the NRC for their use.

Modification: The required liquid penetrant examination of 4.0(b) will be performed. In lieu of ultrasonic examination in accordance with Appendix I, the ultrasonic examination will be in accordance with N-Examination 504-2 and Appendix Q.

(Referenced below in 4.0(b) para. 1.0(d) Prior to welding the area to be Examination of the weld overlay covering the ferritic base material and welded and a band around the area of at least 11/2 times the examination of the adjacent ferritic base material shall be performed no component thickness or 5 inch, whichever is less shall be at least sooner than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after completion of the third temperbead layer 50°F.) over the ferritic base material.

Basis: For the application of the weld overlay repair addressedin this 4.0(b) The final weld surface and a band around the area defined in request the appropriateexamination methodologies and volumes are para. 1.0 (d) shall be examined using a surface and ultrasonic methods provided in Code Case N-504-2 and NonmandatoryAppendix Q Code when the completed weld has been at ambient temperature for at least Case N-638-1 applies to any type of welding where a temper bead 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 technique is to be employed and is not specifically written for a weld Appendix 1.3 overlay repair. Code Case N-638-3 has eliminated the requirementto.

examine a band around the area to be welded, and specifies required post weld non-destructive examination of the welded region only.

3 Refer to the 1989 Edition with the 1989 Addenda and later Editions EPRI research has shown that it is not necessary to wait until ambient and Addenda temperature is reached before initiating the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold in order to assure adequate hydrogen removal. No further tempering or potential hydrogen absorptioneffects will occur after deposition of the third overlay layer. See text for reference.

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Request No. 07-ON-004 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 obtainedfrom weld attached thermocouples to monitor interpass temperature during welding. As noted earlierin this document, the NRC has previously approved this type of temperature data collection.

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