ML110900566

N1-14-CMP-001 Use of Weld Overlays as an Alternative Repair Technique for Steam Generator Hot Leg Nozzles

ML110900566
Person / Time
Site:	North Anna
Issue date:	03/30/2011
From:	Price J Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
11-120
Download: ML110900566 (43)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 March 30, 2011 u.s. Nuclear Regulatory Commission Serial No.11-120 Attention: Document Control Desk NLOS/ETS One White Flint North Docket No. 50-338 11555 Rockville Pike License No. NPF-4 Rockville, MD 20852-2738 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNIT 1 - N1-14-CMP-001 USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR TECHNIQUE FOR STEAM GENERATOR HOT LEG NOZZLES Pursuant to 10CFR50.55a(a)(3)(i), Dominion requests NRC approval for proposed alternatives to certain (ASME Code)Section XI - 2004 Edition requirements associated with the Steam Generator hot leg nozzles repairs. The proposed alternative will permit the application of full structural weld overlay (FSWOL) that are planned to mitigate the potential for primary water stress corrosion cracking (PWSCC) susceptibility at North Anna Unit 1. The enclosure to this letter contains the Request N1-14-CMP-001 for North Anna Unit 1, which identifies the affected components, applicable code requirements, proposed alternatives, basis for their use, and the duration.

Dominion plans to mitigate the primary water stress corrosion cracking susceptibility of the North Anna Unit 1 Steam Generator hot leg nozzle dissimilar metal welds (DMWs) by installing a FSWOL on each of the DMWs. This approach provides an alternative to inspection alone as a means to assure the structural integrity of these locations.

Dominion requests review and approval of this request to support implementation of the alternative repair technique during the North Anna Unit 1 spring 2012 refueling outage, currently scheduled to begin in March 2012. Similar alternatives have been submitted for NRC review and approval and these are referenced in the attached request.

Dominion is submitting this request based on the recent ASME approval of Code Case N-740-2.

Serial No.11-120 Docket No. 50-338 Alternative Request N1-14-CMP-001 Page 2 of 3 If you have any questions regarding this submittal, please contact Mr. Thomas Shaub at (804) 273-2763.

Very truly yours, J. la rice Vi e P esident - Nuclear Engineering Enclosures

1. Alternative Request N1-14-CMP-001 for Unit 1 Use of Weld Overlays as an Alternative Repair Technique with Attachments.

2. Commitment Summary Commitments made in this letter: See Enclosure 2

Serial No.11-120 Docket No. 50-338 Alternative Request N1-14-CMP-001 Page 3 of 3 cc: U.S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, Georgia 30303-1257 Mr. J. E. Reasor, Jr.

Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.

Suite 300 Glen Allen, Virginia 23060 Mr. J. T. Reece NRC Senior Resident Inspector North Anna Power Station Mr. J. S. Wiebe NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 G-9A Rockville, Maryland 20852 Ms. K. R. Cotton NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 G-9A Rockville, Maryland 20852 Mr. M. M. Grace Authorized Nuclear Insurance Inspector North Anna Power Station

Serial No.11-120 Docket No. 50-338 Alternative Request N1-14-CMP-001 ENCLOSURE 1 WITH ATTACHMENTS ALTERNATIVE REQUEST N1-14-CMP-001 USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR TECHNIQUE NORTH ANNA POWER STATION UNIT 1 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

North Anna Unit 1 Proposed Alternative N1-14-CMP-001 Docket No. 50-338 Page 1 of37 10 CFR 50.55a Request Relief Request NI-14-CMP-001 Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

--Alternative Provides Acceptable Level of Quality and Safety--

1. American Society of Mechanical Engineers (ASME) Code Components Affected Steam Generator Hot Leg Nozzle To Safe End Dissimilar Metal Welds Class 1 B-F B9.11 11715-WMKS-RC-E-1A.2 Steam Generator Nominal Low Alloy Steel Hot Leg Nozzle/Alloy

/ 29-RC-1 / N-SE29 IN. Hot Leg Nozzle 29 inch 82-182 Weld! Stainless Steel Safe End to Safe End Weld ill 11715-WMKS-RC-E-1B.2 Steam Generator Nominal Low Alloy Steel Hot Leg Nozzle/Alloy

/ 29-RC-4 / N-SE29 IN. Hot Leg Nozzle 29 inch 82-182 Weld! Stainless Steel Safe End to Safe End Weld ill 11715-WMKS-RC-E-1C.2 Steam Generator Nominal Low Alloy Steel Hot Leg Nozzle!Alloy

/ 29-RC-7 / N-SE29 IN. Hot Leg Nozzle 29 inch 82-182 Weld! Stainless Steel Safe End to Safe End Weld ill

- Low Alloy Steel Nozzle - SA- 508 Class 3

- Stainless Steel Safe End-SA-336, Class F316LN

- ill = Inside Diameter

2. Applicable Code Edition and Addenda

American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)Section XI - 2004 Edition [1]

3. Applicable Code Requirement

IWA-4411 of ASME Code Section XI states:

"Welding, brazing and installation shall be performed in accordance with the Owner's Requirements and, except as modified below, in accordance with the original Construction Code of the item."

IWA-4411(a) of ASME Code Section XI states in part:

"Later Editions and Addenda of the Construction Code, or a later different Construction Code, either in its entirety or portions thereof, and Code Cases may be used, provided the substitution is as listed in IWA-4221(c)."

North Anna Unit 1 Proposed Alternative NI-14-CMP-001 Docket No. 50-338 Page 2 of37 IWA-4411(b) of ASME Code Section XI states:

"Revised Owner's Requirements may be used, provided they are reconciled in accordance with IW A-4222."

IWA-4411(e) of ASME Code Section XI states:

"The requirements of IW A-4600(b) may be used when welding is to be performed without the postweld heat treatment required by the Construction Code."

ASME Code Section XI, Appendix VIII, Supplement 11 [2] provides requirements for the qualification requirements for the ultrasonic examination of Full Structural Overlaid Wrought Austenitic Piping Welds.

4. Reason for Request

Dissimilar metal welds (DMWs) containing nickel welding alloys 82 and 182 have experienced primary water stress corrosion cracking (PWSCC) in components operating at pressurized water reactor temperatures [S, 8,9, 10, 11, 12, ISj.

Virginia Electric and Power Company (Dominion) proposes to mitigate the primary water stress corrosion cracking susceptibility of the North Anna Unit 1 Steam Generator Hot Leg Nozzle dissimilar metal welds by installing a full structural weld overlay (FSWOL) on each of the DMWs. This approach provides an alternative to inspection alone as a means to assure the structural integrity of these locations. Dominion will perform an ASME Code Section XI ultrasonic examination (UT) of each of the DMWs prior to application of the full structural weld overlays.

Currently, there are no generically accepted criteria for a licensee to apply a full structural weld overlay to Alloy 82/182 weld material. The issue and addenda of ASME Code Section XI applicable to North Anna Unit 1 does not contain requirements for weld overlays. Dissimilar metal weld overlays have been applied to other components in the PWR industry. This request proposes to use the guidance of ASME Code Cases N-S04-4

[14] and N-638-4 [13], which have been approved by the NRC as documented in Revision 16 of Regulatory Guide 1.147, and as modified by Code Case N-740-2 [6], for application of FSWOLs to the steam generator nozzle to safe end DMWs at North Anna Unit 1. However, since Code Case N-S04-4 is written specifically for stainless steel pipe-to-pipe weld FSWOLs, and Code Case N-638-4 contains additional restrictions and requirements, an alternative is desired. This request describes the requirements Dominion proposes to use to design and install FSWOLs on steam generator nozzle and reactor coolant piping dissimilar metal welds.

S. Proposed Alternative and Basis for Use Pursuant to 10 CPR SO.SSa (a)(3)(i), Dominion proposes as an alternative to the ASME Code requirements stated above, the use of the alternative described in Attachment 1 to this request to perform FSWOLs. This alternative is based on the methodology contained in ASME Code Case N-740-2.

Appendix VIII, Supplement 11 of the 2004 Edition of ASME Code Section XI [2]

specifies requirements for performance demonstration of ultrasonic examination procedures, equipment, and personnel used to detect and size flaws in full structural

North Anna Unit 1 Proposed Alternative NI-14-CMP-001 Docket No. 50-338 Page 3 of37 overlays of wrought austenitic piping welds. Relief is requested to allow use of the Performance Demonstration Initiative (PDI) program implementation of Appendix VIII for qualification of ultrasonic examinations used to detect and size fla ws in the FSWOLs of this request. The proposed modifications to Appendix VIII, Supplement 11 for use on FSWOLs are detailed in Attachment 2.

The use of this alternative is requested on the basis that the proposed requirements will provide an acceptable level of quality and safety.

Dominion plans to apply a full structural Alloy 52M overlay to each of the dissimilar metal Alloy 82/182 dissimilar metal welds identified in Section 1. As has been noted above, ASME Code Case N-504-4, which provides requirements for weld overlay of stainless steel piping, has been conditionally accepted in Revision 16 of Regulatory Guide 1.147 with the condition that the provisions of ASME Code Section XI, Nonmandatory Appendix Q, Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments, must be met. In addition, ASME Code Case N-638-4 has been conditionally accepted in Revision 16 of Regulatory Guide 1.147 with additional conditions related to NDE and to interpass temperature measurement.

Dominion will meet these additional requirements in the Regulatory Guide, and will propose an increase in the temperbead surface area over the ferritic nozzle material as will be described below in this Section.

Dominion proposes to use ASME Code Case N-740-2 as an alternative to ASME Code Case N-504-4. Code Case N-740-2 has been approved by the ASME Code Committee to specifically address FSWOLs on nickel alloy dissimilar metal welds. However, ASME Code Case N-740- 2 has not yet been accepted by the NRC in Regulatory Guide 1.147.

Code Case N-740-2 provides the basis and requirements for the weld overlay techniques.

The Code Case N-740-2 design requirements which are applicable to North Anna Unit 1 are detailed in Attachment 1 and the implementation requirements that are applicable are detailed in Attachments 1 and 2. ASME Code Case N-740-2 also incorporates the approved version of ASME Code Case N-638-4 for allowing a temperbead surface area over the ferritic low alloy steel hot leg steam generator nozzle that is as large as 500 square inches.

A comparison of the proposed alternative, Code Case N-740-2, and ASME Code Case N-504-4/Appendix Q is provided in Attachment 3.

The proposed alternative provides an acceptable methodology for preventing primary water stress corrosion cracking and for reducing defects that may be observed in these welds to an acceptable size. The use of weld overlay filler metals that are resistant to primary water stress corrosion cracking (for example, Alloy 52/52M), weld overlay procedures that create compressive residual stress profiles within the original weld, and post overlay preservice and inservice inspection requirements provide assurance that structural integrity is maintained for the life of the plant. The weld overlays shall also meet the applicable stress limits from ASME Code Section III. Crack growth evaluations for primary water stress corrosion cracking and fatigue of as-found (or conservatively postulated) flaws shall demonstrate that structural integrity will be maintained.

North AnnaUnit 1 Proposed Alternative NI-14-CMP-OOl DocketNo. 50-338 Page 4 of37 Schematic Configuration for FSWOL Locations Schematic representations of the steam generator hot leg nozzle to safe end DMW configuration is presented in Figure 5-1, below.

Steam Generator Hot Leg No:a.le Dissimilar Metal Welds The steam generator hot leg nozzle is a 29-inch ill low alloy steel nozzle that is welded to an austenitic stainless steel safe end. The nozzle is buttered with Alloy 82/182 weld material. The nozzle is also internally clad with stainless steel. The nozzle is welded to the safe end using Alloy 82/182 weld material.

ALLOY 82/182 j WELD

/SA.336 CLASS F316LN STAINLESS STEEL

- '-'_'__~L~.E  :.~

ALLOY 82/182 tLLOY 82/182 BUTTER WELD Notes:

1. Hot Leg Nozzle - SA-508 Grade 3 low alloy steel, internally buttered with Alloy 82/182 and internally clad with austenitic stainless steel

2. Austenitic Stainless Steel Safe End - SA-336, Class F316LN Figure 5-1 Schematic Configuration for FSWOL of Steam Generator Hot Leg Nozzles

North AnnaUnit 1 Proposed Alternative NI-14-CMP-001 DocketNo. 50-338 Page 5 of3?

Suitability of Proposed Post Overlay Nondestructive Examination CNDE)

As a part of the design of the weld overiay, the weld length, surface finish, and flatness are specified to allow qualified ASME Code Section XI, Appendix VIII ultrasonic examinations, as implemented through the EPRI PDI Program, of the weld overlay and the required volume of the base material and original weld. The examinations specified in this proposed alternative provide adequate assurance of structural integrity for the following reasons:

• The ultrasonic (UT) examinations to be performed with the proposed alternative are in accordance with ASME Code Section XI, Appendix VIII, Supplement 11 [2], as implemented through the PDI. These examinations are considered more sensitive for detection of defects, either from fabrication or service induced, than either ASME Code Section III radiography or ultrasonic methods. Further, construction flaws have been included in the PDI qualification sample sets for evaluating procedures and personnel.

• ASME Code Section XI has specific acceptance criteria and evaluation methodology to be utilized with the results from these more sensitive examinations. They consider the materials in which the flaw indications are detected, the orientation and size of the indications, and ultimately their potential structural effects on the component. The acceptance criteria include allowable flaw indication tables for planar flaws (Table IWB-3514-2) and for laminar flaws (Table IWB-3514-3).

• A laminar flaw is defined in ASME Code Section XI as a flaw oriented within 10 degrees of a plane parallel to the surface of the component. This definition is applicable to welds and weld overlays as well as base materials. The standard imposed for evaluating laminar flaws in ASME Code Section XI is more restrictive than the Section III standard for evaluating laminations. The ASME Code Section XI laminar flaw standards, ASME Code Table IWB-35i4-3, are supplemented in Attachment 1 such that the total laminar flaw shall not exceed 10 percent (%) of the weld overlay surface area and no linear dimension of the laminar flaw shall exceed 3 inches. For weld overlay areas where examination is precluded by the presence of the flaw, it is required to postulate the area underneath as being cracked.

• Any planar flaws found during either the weld overlay acceptance or preservice examinations are required to meet the preservice standards of ASME Code Table IWB-3514-2. In applying the planar flaw standards, the thickness of the component shall be defined as the thickness of the weld overlay and the issue of any flaws masked from examination shall also be addressed as a part of the proposed alternative.

• Weld overlays for repair of cracks in piping are not addressed by ASME Code Section III. ASME Code Section III utilizes nondestructive examination procedures and techniques with flaw detection capabilities that are within the practical limits of workmanship standards for welds. These standards are most applicable to volumetric examinations conducted by radiographic examination. Radiography (RT) of weld overlays is not practical because of the presence of radioactive material in the reactor coolant system and water in the pipes. The ASME Code Section III acceptance standards are written for a range of fabrication flaws including lack of fusion,

North AnnaUnit 1 Proposed Alternative NI-14-CMP-001 DocketNo. 50-338 Page 6 of37 incomplete penetration, cracking, slag inclusions, porosity, and concavity. However, experience and fracture mechanics have demonstrated that many of the flaws that would be rejected using ASME Code Section III acceptance standards do not have a significant effect on the structural integrity of the component. The proposed alternatives in Attachments 1 and 2 were written to specifically address weld overlays, and not only does this alternative adequately examine the weld overlays, but it provides more appropriate examinations and acceptance criteria than the staff imposed position.

Conversely, the imposition of ASME Code Section III acceptance standards to weld overlays is inconsistent with years of NRC precedence and without justification given the evidence of past NRC approvals and operating experience.

The ASME Code Section XI acceptance standards 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. They are consistent with previous criteria approved by the NRC for weld overlay installations.

Weld overlays have been used for repair and mitigation of cracking in boiling water reactors for many years. In Generic Letter 88-01, the NRC approved the use of ASME Code Section XI inspection procedures for determining the acceptability of installed weld overlays. In addition, for a number of years the NRC has accepted various versions of ASME Code Case N-504 in RG 1.147 with no conditions regarding the use of ASME Code Section XI acceptance standards for determining the acceptability of weld overlays.

ASME Code Case N-504 (and its later versions) was developed to codify the boiling water reactor (BWR) weld overlay experience and NRC approval is consistent with the NRC acceptability of BWR weld overlays. Similarly, ASME Code Case N-638 (and later versions) was acceptable for use in RG 1.147 with no conditions and has been approved by the NRC for use in both BWR and PWR weld overlay installations using the ASME Code Section XI acceptance standards. The NRC staff found the use of the ASME Code Section XI, Appendix VIII, Supplement 11 acceptable for identifying both construction and service induced flaws in the Safety Evaluation Report (SER) for DC Cook Plant dated February 19,2006 and tacitly approved the associated ASME Code Section XI acceptance criteria, Tables IWB-3514-2 and IWB-3514-3. The staff also accepted the use of ASME Code Section XI acceptance standards in an SER dated July 21, 2004 for the Three Mile Island Plant, for disposition of flaws identified in a weld overlay by PDI qualified ultrasonic examinations, with additional restrictions similar to those proposed herein for regions in which inspection is precluded by the flaws.

Suitability of Proposed Ambient Temperature Temper Bead Technique The overlays addressed by this alternative shall be performed using ambient temperature temper bead welding in lieu of Post Weld Heat Treatment, in accordance with Attachment 1, and the provisions of this Request for Alternative. Research by the Electric Power Research Institute (EPRI) and other organizations on the use of an ambient temperature temper bead process using the machine gas tungsten arc welding (GTAW) process is documented in EPRI Report GC-lll 050 [4]. According to the EPRI report, repair welds performed with an ambient temperature temper bead procedure utilizing the machine gas tungsten arc welding process exhibit mechanical properties equivalent to or better than those of the surrounding base material. Laboratory testing, analysis, successful procedure qualifications, and successful repairs have demonstrated the effectiveness of this process.

North AnnaUnit 1 Proposed Alternative NI-14-CMP-OOI DocketNo. 50-338 Page 7 of37 The effects of the ambient temperature temper bead welding process of Attachment 1 on mechanical properties of repair welds, hydrogen cracking, cold restraint cracking, and extent of overlay coverage of ferritic base metal are addressed in the following paragraphs.

Mechanical Properties of Repair Welds The principal reasons to preheat a component prior to repair welding is to minimize the potential for cold cracking. The two cold cracking mechanisms are hydrogen cracking and restraint cracking. Both of these mechanisms occur at ambient temperature. Preheating slows down the cooling rate resulting in a ductile, less brittle microstructure thereby lowering susceptibility to cold cracking. Preheat also increases the diffusion rate of monatomic hydrogen that may have been trapped in the weld during solidification. As an alternative to preheat, the ambient temperature temper bead welding process utilizes the tempering action of the welding procedure to produce tough and ductile microstructures.

Because precision bead placement and heat input control are utilized in the machine gas tungsten arc welding process, effective tempering of weld heat affected zone (HAZ) is possib le without the application of preheat. According to Section 2-1 of EPRI Report GC-II1050, "the temper bead process is carefully designed and controlled such that successive weld beads supply the appropriate quantity of heat to the untempered heat affected zone such that the desired degree of carbide precipitation (tempering) is achieved.

The resulting microstructure is very tough and ductile."

The IWA-4600 temper bead process also includes a postweld hydrogen bakeout requirement (IWA-4623.2(c)). Performed at 450 - 550 degrees Fahrenheit (OF) for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (P-No. 3 base materials), this postweld bakeout assists diffusion of any remaining hydrogen from the repair weld. As such, the postweld bakeout is a hydrogen bakeout and not a postweld heat treatment as defined by the ASME Code. At 450 - 550 of the postweld bakeout does not stress relieve, temper, or alter the mechanical properties of the weldment in any manner. Since the potential for hydrogen absorption is greatly diminished by the use of gas tungsten arc welding temper bead process, no postweld soak is needed for this application.

The alternative in Attachment 1 establishes detailed welding procedure qualification requirements for base materials, filler metals, restraint, impact properties, and other procedure variables. The qualification requirements provide assurance that the mechanical properties of repair welds shall be equivalent to or superior to those of the surrounding base material.

Hydrogen Cracking Hydrogen cracking is a form of cold cracking. It is produced by the action of internal tensile stresses acting on low toughness heat affected zones. The internal stresses are produced from localized build-ups of monatomic hydrogen. Monatomic hydrogen forms when moisture or hydrocarbons interact with the welding arc and molten weld pool. The monatomic hydrogen can be entrapped during weld solidification and tends to migrate to transformation boundaries or other microstructure defect locations. As concentrations build, the monatomic hydrogen recombines to form molecular hydrogen - thus generating localized internal stresses at these internal defect locations. If these stresses exceed the

North AnnaUnit 1 Proposed Alternative NI-I4-CMP-001 DocketNo. 50-338 Page 8 of37 fracture toughness of the material, hydrogen induced cracking occurs. This form of cracking requires the presence of hydrogen and low toughness materials. It is manifested by intergranular cracking of susceptible materials and normally occurs within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of welding.

IWA-4600 establishes elevated preheat and postweld soak requirements. The elevated preheat temperature of 300 degrees Fahrenheit increases the diffusion rate of hydrogen from the weld. The postweld bakeout at 450 - 550 degrees Fahrenheit was also established to bakeout or facilitate diffusion of any remaining hydrogen from the weldment. However, while hydrogen cracking is a concern for shielded metal arc welding (SMA W), which uses flux covered electrodes, the potential for hydrogen cracking is significantly reduced when using machine gas tungsten arc welding.

The machine gas tungsten arc welding process is inherently free of hydrogen. Unlike the shielded metal arc welding process, gas tungsten arc welding filler metals do not rely on flux coverings that may be susceptible to moisture absorption from the environment.

Conversely, the gas tungsten arc welding process utilizes dry inert shielding gases that cover the molten weld pool from oxidizing atmospheres. Any moisture on the surface of the component being welded is vaporized ahead of the welding torch. The vapor is prevented from being mixed with the molten weld pool by the inert shielding gas that blows the vapor away before it can be mixed. Furthermore, modern filler metal manufacturers produce wires having very low residual hydrogen. This is important because filler metals and base materials are the most realistic sources of hydrogen for the automatic or machine gas tungsten arc welding temper bead process. Therefore, the potential for hydrogen-induced cracking is greatly reduced by using the machine gas tungsten arc welding process. Extensive research has been performed by EPRI [7] 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 ASME Code Cases N-638-4 and N-740-2 shall be implemented in accordance with this latest research. This approach has been previously approved by the NRC staff in the SER for Davis Besse, dated January 21,2010, for Reactor Coolant Piping

[16].

Cold Restraint Cracking Cold cracking generally occurs during cooling at temperatures approaching ambient temperature. As stresses build under a high degree of restraint, cracking may occur at defect locations. Brittle microstructures with low ductility are subject to cold restraint cracking. However, the ambient temperature temper bead process is designed to provide a sufficient heat inventory so as to produce the desired tempering for high toughness.

Because the machine gas tungsten arc welding temper bead process provides precision bead placement and control of heat, the toughness and ductility of the heat affected zone is typically superior to the base material. Therefore, the resulting structure shall be appropriately tempered to exhibit toughness sufficient to resist cold cracking.

Area Limitation The latest ASME and NRC approved version of ASME Code Case N-638, denoted N-638-4 in Regulatory Guide 1.147, Revision 16, for temper bead welding, contains a limit of 500

North AnnaUnit 1 Proposed Alternative NI-I4-CMP-00I DocketNo. 50-338 Page 9 of37 square inches for the surface area of temper bead weld over the ferritic base metal. The associated limitation proposed in this alternative is 1000 square inches. The justification for this proposed alternative is described in the paragraph below.

The NRC has recently approved extending of the temper bead surface area limitation to 700 square inches in the Davis-Besse Relief Request, Adams Accession No. ML100080573. In addition, EPRI has issued Report ill 1021073 on June 21,2010, entitled "Justification for Extension of the Temper Bead Limit to 1000 Square Inches for WOL of PI and P3 Materials" [3]. This report states that "The results of the analysis work described in this report show that larger scale temperbead weld repairs could be performed on low-alloy steel components. Specifically, repairs that included weld overlays on vessel nozzles and similar components could be expanded to an area of 1000 square inches without creating deleterious residual stress levels and still maintain the structural integrity of the component".

Due to the outside diameter of the steam generator hot leg nozzles, the weld overlay repair may extend up to greater than 700 square inches of surface area on the low alloy steel component, but will be less than 1000 square inches of surface area. Consequently, the proposed alternative includes a maximum individual weld overlay area requirement of 1000 square inches, as discussed within General Requirement A2.2(b) of Attachment I.

Analyses and Verifications The following list of analyses and verifications shall be performed subject to the specific design, analysis, and inspection requirements that have been defined in this alternative.

I. Nozzle specific stress analyses shall be performed to establish a residual stress profile in the nozzle. Inside diameter (ill) weld repairs shall be assumed in these analyses to effectively bound any actual weld repairs that may have occurred in the nozzles. The analysis shall then simulate application of the weld overlays to determine the final residual stress profile. Post weld overlay residual stresses at normal operating conditions shall be shown to result in an improved stress state in the component that reduces the probability for further crack propagation due to primary water stress corrosion cracking.

2. Fracture mechanics analyses shall be performed to predict crack growth. Crack growth due to primary water stress corrosion cracking and fatigue crack growth in the original dissimilar metal weld shall be evaluated. The crack growth analyses shall consider all design loads and transients, plus the post weld overlay through-wall residual stress distributions, and shall demonstrate that the assumed cracks shall not grow beyond the design bases for the weld overlays (that is, through the original dissimilar metal weld thickness and any additional allowance for crack growth within the weld overlay) for the time period until the next scheduled inservice inspection.

The crack growth analyses shall determine the time period for the assumed cracks to grow to the design basis for the weld overlay.

3. The analyses shall demonstrate that the application of the weld overlays does not impact the conclusions of the existing nozzle stress reports. ASME Code Section III stress and fatigue criteria shall be met for the regions of the overlays remote from observed (or assumed) cracks.

North Anna Unit 1 Proposed Alternative N1-14-CMP-001 Docket No. 50-338 Page 10 of37

4. Axial shrinkage shall be measured before and after the weld overlay application.

Shrinkage stresses arising from the weld overlays at other locations in the piping systems shall be demonstrated to not have an adverse effect on the systems.

Clearances of affected supports and restraints shall be checked after the overlay repair, and shall be reset within the design ranges as required.

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

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

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 following completion of the weld overlays. Items 4 through 6 are performed following installation of the weld overlays and results shall be included in the design modification package closure documents. This information shall be available to resident or field inspectors for review as needed.

The following information will be submitted to the NRC within 14 days of completion of the final ultrasonic examination of the overlaid welds. 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 indications detected 1

• The disposition of all indications using the standards of ASME Code Section XI, IWB-3514-2 and/or IWB-3514-3 criteria and, if possible, the type and nature of the indications' Conclusions Quality and Safety of Proposed Alternative Implementation of the alternative to IWA-4600 of ASME Code Section XI described in Attachments 1 and 2 of this request shall produce effective repairs or mitigation for potential primary water stress corrosion cracking in the identified welds and improve piping geometries to permit ASME Code Appendix VIII ultrasonic examinations as implemented through the PDI program. Weld overlay repairs of dissimilar metal welds have been installed and performed successfully for many years in both pressurized water reactor and boiling water reactor applications.

The alternative provides improved structural integrity and reduced likelihood of I The recording criteria of the ultrasonic examination procedure to be used for the examination of the Dominion overlays requires that all 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 requires that all suspected flaw indications are to be plotted on a cross sectional drawing of the weld and that the plots should accurately identify the specific origin of the reflector.

North AnnaUnit 1 Proposed Alternative NI-14-CMP-001 DocketNo. 50-338 Page 11 of37 leakage for the primary system. Accordingly, the use of the alternative provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(a)(3)(i).

6. Duration of Proposed Alternative The provisions of this alternative are applicable to the fourth ten-year inservice inspection interval for Dominion which commenced on May 1,2009 and will end on April 30, 2019.

The weld overlays installed in accordance with the provisions of this alternative shall remain in place for the design life of the repair established as described in Attachments 1 and 2.

7. References

1. ASME Boiler and Pressure Vessel Code,Section XI, 2004 Edition.

2. ASME Boiler and Pressure Vessel Code,Section XI, 2004 Edition, Appendix VIII, Supplement 11, "Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds."

3. EPRI Report 1021073 "Justification for Extension of the Temper Bead Limit to 1000 Square Inches for WOL of PI and P3 Materials", June 21,2010.

4. EPRI Report GC-lll050, November 1998, "Ambient Temperature Preheat for Machine GTAW Temper Bead Applications", EPRI, Palo Alto, CA, and Structural Integrity Associates, Inc., San Jose, CA.

5. EPRI Materials Reliability Program Report: Crack Growth Rates for Evaluating PWSCC of Alloy 82, 182, and 132 Welds (MRP-115), EPRI, Palo Alto, CA, and Dominion Engineering, Inc., Reston, VA: November 2004. 1006696.

6. ASME Code Case N-740-2 "Dissimilar Metal Weld Overlay for Repair or Mitigation of Class 1,2, and 3 Items".

7. EPRI Report 1013558, Temperbead Welding Applications, 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding, EPRI, Palo Alto, CA and Hermann & Associates, Key Largo, FL, December 2006.

8. W. HUbner, B. Johansson, and M. de Pourbaix, Studies of the Tendency to Intergranular Stress Corrosion Cracking of Austenitic Fe-Cr-Ni Alloys in High Purity Water at 300°C, Studsvik report AE-437, Nykoping, Sweden, 1971.

9. W. Debray and L. Stieding, Materials in the Primary Circuit of Water-Cooled Power Reactors, International Nickel Power Conference, Lausanne, Switzerland, May 1972, Paper No.3.

10. C. Arnzallag, et al., "Stress Corrosion Life Assessment of 182 and 82 Welds used in PWR Components," Proceedings of the 10th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, NACE,2001.

North AnnaUnit 1 Proposed Alternative NI-I4-CMP-001 DocketNo. 50-338 Page 12 of37

11. NUREG/CR-6907, "Crack Growth Rates of Nickel Alloy Welds in a PWR Environment," U.S. Nuclear Regulatory Commission (Argonne National Laboratory), May 2006.

12. EPRI Material Reliability Program Report: Primary System Piping Butt Weld Inspection and Evaluation Guidelines (MRP-139), EPRI, Palo Alto, CA: August 2005. 1010087.

13. ASME Code Case N-638-4 "Similar and Dissimilar Metal Welding Using Ambient Temperature GTAW Temper Bead Technique."

14. ASME Code Case N-S04-4 "Alternative Rules for Repair of Classes 1,2, and 3 Austenitic Stainless Steel Piping."

IS. D. Buisine, et aI., "PWSCC Resistance of Nickel Based Weld Metals with Various Chromium Contents," Proceedings: 1994 EPRI Workshop on PWSCC of Alloy 600 in PWRs, EPRI, Palo Alto, CA: 1995. TR-lOS406, Paper DS.

16. NRC SER Davis-Besse Nuclear Power Station Unit 1- Relief Request RR-A33 for the Application of Full Structural Weld Overlays on Dissimilar Metal Welds of Reactor Coolant Piping (TAC No. ME0478), Adams Accession Number ML100080S73, January 21, 2010.

North AnnaUnit 1 Proposed Alternative NI-I4-CMP-001 DocketNo. 50-338 Page 13 of37 North Anna Unit 1 Proposed Alternative Attachment 1 Page 1 of 13 PROPOSED ALTERNATIVE FOR NORTH ANNA UNIT 1 RPV HOT LEG NOZZLE TO SAFE END DISSIMILAR METAL WELD OVERLAYS Al.l INTRODUCTION Dominion proposes the following detailed requirements for the design, analysis, fabrication, examination, and pressure testing of the North Anna Unit 1 steam generator hot leg nozzle to safe end dissimilar metal weld overlays. These requirements, which are derived from applicable portions of ASME Code Case N-740-2, provide an acceptable methodology for reducing potential defects in these austenitic nickel alloy welds to an acceptable size or mitigating the potential for future primary water stress corrosion cracking by increasing the wall thickness through deposition of weld overlays. The weld overlays shall be applied by deposition of weld reinforcement (weld overlay) on the outside surface of the piping, nozzles, and associated dissimilar metal welds, including ferritic materials when necessary, in accordance with the following requirements:

Al.2 GENERAL REQUIREMENTS Al.2.1 Definitions (a) full structural weld overlay - deposition of weld reinforcement on the outside diameter of the piping, component, or associated weld, such that the weld reinforcement is capable of supporting the design loads, without consideration of the piping, component, or associated weld beneath the weld reinforcement. Full structural weld overlay can be either mitigative or repair weld overlay as defined in A1.2.1(b) and (c).

(b) mitigative weld overlay - weld overlay that is applied over material with no inside-surface-connected flaws found during an examination performed in accordance with A1.3(a)(3), prior to the weld overlay being applied.

(c) repair weld overlay- weld overlay that is applied over material with an inside-surface-connected flaw or subsurface defect, or where a pre-weld overlay examination is not performed.

(d) SCC susceptible materials - for this proposed alternative, the stress-corrosion-cracking (SCC) susceptible materials are Unified Numbering System (OOS) N06600, N06082, or W86182 in pressurized water reactor environments; or OOS N06600, W86182, or austenitic stainless steels and associated welds in boiling water reactor environments.

Al.2.2 General Overlay Requirements (a) A full-structural weld overlay shall be applied by deposition of weld reinforcement (weld overlay) on the outside surface of circumferential welds. This proposed method applies to austenitic nickel alloy and austenitic stainless steel welds between the following:

(1) P-No. 8 or P-No. 43 and P-Nos. 1,3, 12A, 12B, or 12C (2) P-No. 8 and P-No. 43 (3) Between P-Nos. 1, 3, 12A, 12B, and 12C materials

North Anna Unit 1 Proposed Alternative NI-14-CMP-00I Docket No. 50-338 Page 14 of37 Attachment 1 Page 2 of 13 (b) If a weld overlay on any of the material combinations in Al.2.2(a) obstructs a required examination of an adjacent P-No. 8 to P-No. 8 weld, the overlay may be extended to include overlaying the adjacent weld.

(c) Weld overlay filler metal shall be austenitic nickel alloy (28 percent chromium minimum, ERNiCrFe-7/7A) meeting the requirements of 1.2(e)(1) or (2), as applicable, applied 360 degrees around the circumference of the item and deposited using a Welding Procedure Specification (WPS) for groove welding, qualified in accordance with the Construction Code and Owner's Requirements identified in the RepairlReplacement Plan. As an alternative to the post weld heat treatment (PWHT) requirements of the Construction Code and Owner's requirements, ambient-temperature temper bead welding in accordance with A2.1 shall be used.

(d) Prior to deposition of the weld overlay, the surface to be weld overlaid shall be examined using the liquid penetrant method. Indications with major dimensions greater than V16 inch (1.5 millimeters) shall be removed, reduced in size, or weld repaired in accordance with the following requirements:

(1) One or more layers of weld metal shall be applied to seal unacceptable indications in the area to be repaired with or without excavation. The thickness of these layers shall not be used in meeting weld reinforcement design thickness requirements. Peening the unacceptable indication prior to welding is permitted.

(2) If weld repair of indications identified in A1.2.2(d) is required, the area where the weld overlay is to be deposited, including any local weld repairs or initial weld overlay layer, shall be examined by the liquid penetrant method. The area shall contain no indications with major dimensions greater than V16 inch (1.5 millimeters) prior to application of the structural layers of the weld overlay.

(3) To reduce the potential of hot cracking when applying an austenitic nickel alloy over P-No. 8 base metal, it is permissible to apply a layer or multiple layers of austenitic stainless steel filler material over the austenitic stainless steel base metal. The stainless steel filler metal shall have a delta ferrite content of 5 - 15 Ferrite Number (FN), as reported on the Certified Material Test Report.

The thickness of these buffer layers shall not be used in meeting weld reinforcement design thickness requirements.

(e) Weld overlay deposits shall meet the following requirements:

(1) The austenitic nickel alloy weld overlay shall consist of at least two weld layers deposited using a filler material with a chromium (Cr) content of at least 28 percent. The first layer of weld metal deposited may not be credited toward the required thickness except that a first diluted layer may be credited toward the required thickness, provided the portion of the layer over the austenitic base material, austenitic filler material weld, and the associated dilution zone from an adjacent ferritic base material contain at least 24 percent Cr, and the Cr content of the deposited weld metal is determined by chemical analysis of the production weld or of a representative coupon taken from a mockup prepared in accordance with the weld procedure for the production weld.

if) A new weld overlay shall not be installed over the top of an existing weld overlay that has been in service.

North AnnaUnit 1 Proposed Alternative NI-I4-CMP-001 DocketNo. 50-338 Page 15 of 37 Attachment 1 Page 3 of 13 Al.3 CRACK GROWTH AND DESIGN (a) Crack Growth Calculation of Flaws in the Original Weld or Base Metal. The size of all flaws detected or postulated in the original weld or base metal shall be used to define the life of the overlay.

The inspection interval shall not be longer than the shorter of the life of the overlay or the period specified in A1.4(c). Crack growth due to both stress corrosion and fatigue, shall be evaluated. Flaw characterization and evaluation shall be based on the examination results or postulated flaw, as described below. If the flaw is at or near the boundary of two different materials, evaluation of flaw growth in both materials is required.

(1) For repair overlays, the initial flaw size for crack growth in the original weld or base metal shall be based on the as-found flaw or postulated flaw, if no pre-overlay examination is performed.

(2) For postulated flaws, the axial flaw length shall be 1.5 inches (38 millimeters) or the combined width of the weld plus buttering plus any adjacent SCC susceptible material, whichever is greater.

The circumferential flaw length shall be assumed to be 360 degrees. The depths associated with these lengths are specified in A1.3(a)(3) and A1.3(a)(4).

(3) If an ASME Section XI, Appendix VIII, Supplement 10, or Supplement 2, as applicable, ultrasonic examination is performed prior to application of the overlay, and no inside-surface-connected planar flaws are discovered, initial flaws originated from the inside surface of the weldment equal to 10 percent of the original wall thickness shall be assumed in both the axial and circumferential directions, and the overlay shall be considered mitigative.

(4) If an ASME Section XI, Appendix VIII, Supplement 10, or Supplement 2, as applicable, ultrasonic examination is not performed prior to application of the overlay, initial inside-surface-connected planar flaws equal to at least 75 percent through the original wall thickness shall be assumed, in both the axial and circumferential directions, and the overlay shall be considered a repair.

(5) There may be circumstances in which an overlay examination is performed using an ultrasonic examination procedure qualified in accordance with Appendix VIII, Supplement 11 for depths greater than the outer 25 percent of the original wall thickness (Fig. AI-2). For such cases, the initial flaw depths are assumed to be the detected depth found by the Appendix VIII, Supplement 11 qualified examination, plus the postulated worst-case flaw in the region not covered by the Appendix VIII ultrasonic examination.

(6) In determining the life of the overlay, any inside-surface-connected planar flaw found by the overlay preservice inspection of A1.4(b) that exceeds the depth of (3), (4), or (5) above shall be used as part of the initial flaw depth. The initial flaw depth assumed is the detected flaw depth plus the postulated worst-case flaw depth in the region of the pipe wall thickness that was not examined using an ultrasonic examination procedure meeting Appendix VIII for that region. An overlay meeting this condition shall be considered a repair, rather than mitigation.

(b) Structural Design and Sizing ofthe Overlay. The design of the weld overlay shall satisfy the following, using the assumptions and flaw characterization requirements in A1.3(a). The following design analysis shall be completed in accordance with IWA-4311:

North AnnaUnit 1 Proposed Alternative N1-I4-CMP-00l DocketNo. 50-338 Page 16 of 37 Attachment 1 Page 4 of 13 (1) The axial length and end slope of the weld overlay shall cover the weld and heat-affected zones on each side of the weld, as well as any stress corrosion cracking susceptible base material adjacent to the weld, and provide for load redistribution from the item into the weld overlay and back into the item without violating applicable stress limits of NB-3200. Any laminar flaws in the weld overlay shall be evaluated in the analysis to ensure that load redistribution complies with the above. These requirements are usually satisfied if the weld overlay full thickness length extends axially beyond the SCC-susceptible material or projected flaw by at least O.7sJRi, where R is the outer radius of the item and t is the nominal wall thickness of the item at the applicable side of the overlay (that is, Rand t of the nozzle on the nozzle side and Rand t of the safe-end on the safe-end side).

(2) Unless specifically analyzed in accordance with A1.3(b)(1), the end transition slope of the overlay shall not exceed 30 degrees.

(3) The assumed flaw in the underlying base material or weld shall be based on the limiting case of A1.3(b)(3)(a) and (b) that results in the larger required overlay thickness.

(a) 100 percent through-wall circumferential flaw for the entire circumference (b) 100 percent through-wall flaw with length of 1.5 inches (38 millimeters), or the combined width of the weld plus buttering plus any SCC-susceptible material, whichever is greater, in the axial direction (4) The overlay design thickness shall be verified, using only the weld overlay thickness conforming to the deposit analysis requirements of A1.2.2(e). The combined wall thickness at the weld overlay, any postulated worst-case planar flaws under the laminar flaws in the weld overlay, and the effects of any discontinuity (for example, another weld overlay or reinforcement for a branch connection) within a distance of 2.5.JRi, from the toes of the weld overlay, including the flaw size assumptions defined in A1.3(b)(3) above, shall be evaluated and shall meet the requirements of IWB-3640.

(5) The effects of any changes in applied loads, as a result of weld shrinkage from the entire overlay, on other items in the piping system (for example, support loads and clearances, nozzle loads, and changes in system flexibility and weight due to the weld overlay) shall be evaluated. Existing flaws previously accepted by analytical evaluation shall be evaluated in accordance with IWB-3640.

AI.4 EXAMINATION In lieu of all other examination requirements, the examination requirements of this proposed method shall be met for the life of the overlay. Nondestructive examination methods shall be in accordance with IWA-2200, except as specified herein. Nondestructive examination personnel shall be qualified in accordance with IWA-2300. Ultrasonic examination procedures and personnel shall be qualified in accordance with the modified requirements to ASME Code Section XI, Appendix VIII, Supplement 11 as described in . The examination shall be performed to the maximum extent practicable, for axial and circumferential flaws. If 100 percent coverage of the required volume for axial flaws cannot be achieved, but essentially 100 percent coverage for circumferential flaws (100 percent of the susceptible volume) can be achieved, the examination for axial flaws shall be performed to achieve the maximum coverage practicable, with limitations noted in the examination report. The examination coverage requirements

North AnnaUnit 1 Proposed Alternative NI-I4-CMP-001 DocketNo. 50-338 Page 17 of37 Attachment 1 Page 5 of 13 shall be considered to be met. For welds containing cast stainless steel materials the examination volume includes only the susceptible material (non-stainless steel) volume.

(a) Acceptance Examination (1) The weld overlay shall have a surface finish of 250 micro-inches (uin), 6.3 micrometer (urn) roughness measurement system (RMS) or better and contour that permits ultrasonic examination in accordance with procedures qualified in accordance with ASME Code Section XI, Appendix VIII.

The weld overlay shall be inspected to verify acceptable configuration.

(2) The weld overlay and the adjacent base material for at least 1/2 inch (13 millimeters) from each side of the overlay shall be examined using the liquid penetrant method. The weld overlay shall satisfy the surface examination acceptance criteria for welds of the Construction Code or NB-5300.

The adjacent base material shall satisfy the surface examination acceptance criteria for base material of the Construction Code or NB-2500. If ambient temperature temper bead welding is performed, the liquid penetrant examination of the completed weld overlay shall be conducted no sooner than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> following completion of the three tempering layers over the ferritic steel.

(3) The examination volume A-B-C-D in Figure Al-l(a) shall be ultrasonically examined to assure adequate fusion (that is, adequate bond) with the base material and to detect welding flaws, such as interbead lack of fusion, inclusions, or cracks. The interface C-D shown between the overlay and weld includes the bond and heat-affected zone from the overlay. If ambient temperature temper bead welding is performed, the ultrasonic examination shall be conducted no sooner than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> following completion of the three tempering layers over the ferritic steel. Planar flaws detected in the weld overlay acceptance examination .shall meet the preservice examination standards of IWB-3514.

In applying the acceptance standards to planar indications, the thickness, t] or t2 defined in Figure Al-l(b) shall be used as the nominal wall thickness in IWB-3514, provided the base material beneath the flaw (that is, safe end, nozzle, or piping material) is not susceptible to stress corrosion cracking. For susceptible material, t] shall be used. If a flaw in the overlay crosses the boundary between the two regions, the more conservative of the two dimensions (t] or t2) shall be used. Laminar flaws in the weld overlay shall meet the following requirements:

(a) The acceptance standards ofIWB-3514 shall be met, with the additional limitation that the total laminar flaw area shall not exceed 10 percent of the weld surface area and that no linear dimension of the laminar flaw area shall exceed the greater of 3 inches (76 millimeters) or 10 percent of the pipe circumference.

(b) For examination volume A-B-C-D in Figure Al-l (a), the reduction in coverage due to laminar flaws shall be less than 10 percent. The uninspectable volume is the volume in the weld overlay underneath the laminar flaws for which coverage cannot be achieved with the angle beam examination method.

(c) Any uninspectable volume in the weld overlay shall be assumed to contain the largest radial planar flaw that could exist within that volume. This assumed flaw shall meet the preservice examination acceptance standards of IWB-3514, with nominal wall thickness as defined above the planar flaws. Alternatively, the assumed flaw shall be evaluated and meet the requirements of IWB-364. Both axial and circumferential planar flaws shall be assumed.

(4) After completion of all welding activities, VT-3 visual examination shall be performed on all affected restraints, supports, and snubbers, to verify that design tolerances are met.

North AnnaUnit 1 Proposed Alternative NI-I4-CMP-001 Docket No. 50-338 Page 18 of 37 Attachment 1 Page 6 of 13 EndTransition Slope (not to exceed 30-<f~r;;es. unlessooaf)zed}

A B (a) Examination Volume A-B-C-D A

D (b) Thickness (t1 and t2) for Table IWB-35 14-2 Notes:

1 Dimension b is equivalent to the nominal thickness of the nozzle or pipe being overlaid, as appropriate.

2 The nominal wall thickness is t1 for flaws in E-F-G-H, and tz for flaws in A-E-H-D or F-B-C-G.

3 For flaws that span two examination volumes (such as illustrated at F-G), the t1 thickness shall be used.

4 The weld includes the nozzle or safe end butter, where applied, plus any stress corrosion cracking susceptible base material in the nozzle.

Figure A1-1 Examination Volume and Thickness Definitions (b) Preservice Inspection (1) The examination volume in Fig. Al-2 shall be ultrasonically examined. The angle beam shall be directed perpendicular and parallel to the piping axis, with scanning performed in four directions, to locate and size any planar flaw that have propagated into the outer 25 percent of the base metal thickness or into the weld overlay. For weld overlays on cast austenitic stainless steel base materials, if a 100 percent through-wall flaw is used for crack growth, only planar flaws that have propagated into the weld overlay, or are in the overlay, are required to be located and sized.

North Anna Unit 1 Proposed Alternative NI-I4-CMP-001 Docket No. 50-338 Page 19 of37 Attachment 1 Page 7 of 13 (2) The preservice examination acceptance standards ofIWB-3514 shall be met for the weld overlay.

In applying the acceptance standards to planar indications, the thickness, t[ or t2, defined in Fig. Al-l(b) shall be used as the nominal wall thickness in IWB-3514, provided the base material beneath the flaw (that is, safe end, nozzle, or piping material) is not susceptible to SCC. For susceptible material, t[ shall be used. Planar flaws in the outer 25 percent of the base metal thickness shall meet the design analysis requirements of Al.3(b).

(3) The flaw evaluation requirements ofIWB-3640 shall not be applied to planar flaws, identified during preservice examination, that exceed the preservice examination acceptance standards of IWB-3514.

Minimum 1/2 in. (13 mm) Minimum112 in. (13 mm) (Note 1) 1t

_ _~--------3lC~~---......-._j As-found Raw - - - - - - - '

Examination Volume A-B-C-D Notes:

1 The weld includes the nozzle or safe end butter, where applied.

2 For axial or circumferential flaws, the axial extent of the examination volume shall extend at least Y2 inch (13 millimeters) beyond the as-found flaw and at least Y2 inch (13 millimeters) beyond the toes of the original weld, including weld end butter, where applied.

Figure AI-2 Preservice and Inservice Examination Volume (c) Inservice Inspection (1) For welds whose pre-overlay examination, post-overlay acceptance examination, or preservice examination did not reveal any planar flaws, the welds shall be placed into a population of full structural weld overlays to be examined on a sample basis. Twenty-five (25) percent of this population shall be added to the lSI Program and shall be examined once each inspection interval. If multiple welds are mitigated in the same inspection period, examinations shall be spread throughout years 3 through 10 following application, similar to provisions in IWB-2412(b). The 25 percent sample shall consist of the same welds in the same sequence during successive intervals to the extent practical provided the 25 percent sample contains welds that experience the hottest operating temperature in the population. If hot leg and cold leg welds are included in the population, the 25 percent sample does not need to include the cold leg welds. All weld overlays, including those not in the 25 percent sample, shall be examined prior to the end of their design life as determined in Al.3(a).

North Anna Unit 1 Proposed Alternative NI-I4-CMP-001 Docket No. 50-338 Page 20 of37 Attachment 1 Page 8 of 13 (2) For welds whose pre-overlay examination, post-overlay acceptance examination, or preservice examination reveal planar flaws, or for which a pre-overlay examination was not performed, the weld overlay shall be ultrasonically examined during the first or second refueling outage following application. Examination volumes that show no indication of crack growth or new cracking shall then be placed into a population of full structural weld overlays to be examined on a sample basis.

Twenty- five (25) percent of this population shall be added to the lSI Program in accordance with IWB-24I2(b). The 25 percent sample shall consist of the same welds in the same sequence during successive intervals to the extent practical provided the 25 percent sample contains welds that experience the hottest operating temperature in the population. If hot leg and cold leg welds are included in the population, the 25 percent sample does not need to include the cold leg welds. All weld overlays, including those not in the 25 percent sample, shall be examined prior to the end of their design life as determined in A1.3(a).

(3) The weld overlay examination volume in Fig. AI-2 shall be ultrasonically examined to determine if any new or existing planar flaws have propagated into the outer 25 percent of the base material thickness or into the overlay. The angle beam shall be directed perpendicular and parallel to the piping axis, with scanning performed in four directions.

(4) The weld overlay shall meet the inservice examination acceptance standards ofIWB-35I4. In applying the acceptance standards to planar indications, the thickness, t1 or t2, defined in Fig. AI-I (b) shall be used as the nominal wall thickness in IWB-35I4, provided the base material beneath the flaw (that is, safe end, nozzle, or piping material) is not susceptible to SCC. For susceptible material, t1 shall be used. Ifthe acceptance standards ofIWB-35I4 cannot be met, the weld overlay shall meet the acceptance standards of IWB-3600. If a planar flaw is detected in the outer 25 percent of the base material thickness shall meet the design analysis requirements of AI.3. Any indication characterized as stress corrosion cracking in the weld overlay material is unacceptable.

(5) If inservice examinations reveal planar flaw growth, or new planar flaws, meeting the acceptance standards of IWB-35I4 or IWB-3600, the weld overlay examination volume shall be reexamined during the first or second refueling outage following discovery of the growth or new flaws.

(6) For weld overlay examination volumes with unacceptable indications in accordance with A1.4(c)(5), the weld overlay and original defective weld shall be removed. A repair/replacement activity shall be performed in accordance with IWA-4000.

(d) Additional Examinations. If inservice examinations reveal a defect, in accordance with A1.4(c)(5),

planar flaw growth into the weld overlay design thickness, or axial flaw growth beyond the specified examination volume, additional weld overlay examination volumes, equal to the number scheduled for the current inspection period, shall be examined prior to return to service. If additional defects are found in the second sample, 50 percent of the total population of weld overlay examination volumes shall be examined prior to return to service. If additional defects are found, the entire remaining population of weld overlay examination volumes shall be examined prior to return to service.

North Anna Unit 1 Proposed Alternative NI-I4-CMP-001 Docket No. 50-338 Page 21 of 37 Attachment 1 Page 9 of 13 AI.S PRESSURE TESTING A system leakage test shall be performed in accordance with IW A-SOOO.

AI.6 DOCUMENTATION Use of this proposed method shall be documented on Form NIS-2.

North Anna Unit 1 Proposed Alternative NI-I4-CMP-00I Docket No. 50-338 Page 22 of37 Attachment 1 Page 10 of 13 AMBIENT-TEMPERATURE TEMPERBEAD WELDING A2.1 AMBIENT-TEMPERATURE TEMPER BEAD WELDING A2.2 GENERAL REQUIREMENTS (a) This Attachment applies to dissimilar austenitic filler metal welds between P-Nos. 1,3, 12A, 12B, and 12C materials and their associated welds and welds joining P- No.8 or 43 materials to P-Nos. 1, 3, 12A, 12B, and 12C materials with the following limitation. This Attachment shall not be used to repair SA-302 Grade B material unless the material has been modified to include from 0.4 percent to 1.0 percent nickel, quenching, tempering, and application of a fine grain practice.

(b) The maximum area of an individual weld overlay based on the finished surface over the ferritic base material may be greater than 600 square inches (390, 000 square millimeters), but less than 1000 square inches (650,000 square millimeters).

(c) Repairlreplacement activities on a dissimilar-metal weld in accordance with this Attachment are limited to those along the fusion line of a nonferritic weld to ferritic base material on which 1/8 inch (3 millimeters) or less of nonferritic weld deposit exists above the original fusion line.

(d) If a defect penetrates into the ferritic base material, repair of the base material, using a nonferritic weld filler material, may be performed in accordance with this Attachment, provided the depth of repair in the base material does not exceed % inch (10 millimeters).

(e) Prior to welding, the area to be welded and a band around the area of at least 1Yz times the component thickness or 5 inches (130 millimeters), whichever is less, shall be at least 50 degrees Fahrenheit (10 degrees Celsius).

(j) Welding materials shall meet the Owner's Requirements and the Construction Code and Cases specified in the RepairlReplacement Plan. Welding materials shall be controlled so that they are identified as acceptable until consumed.

(g) Peening may be used, except on the initial and final layers.

A2.3 WELDING QUALIFICATIONS The welding procedures and operators shall be qualified in accordance with ASME Code Section IX and the requirements of A2.3.1 and A2.3.2.

North AnnaUnit 1 Proposed Alternative NI-I4-CMP-001 DocketNo. 50-338 Page 23 of37 Attachment 1 Page 11 of 13 A2.3.1 Procedure Qualification (a) The base materials for the welding procedure qualification shall be of the same P-Number and Group Number as the materials to be welded. The materials shall be postweld heat treated to at least the time and temperature that was applied to the materials being welded.

(b) The maximum interpass temperature for the first three layers of the test assembly shall be 150 degrees Fahrenheit (66 degrees Celsius).

(c) The weld overlay shall be qualified using groove weld coupon. The test assembly groove depth shall be at least 1 inch (25 millimeters). The test assembly thickness shall be at least twice the test assembly groove depth. The test assembly shall be large enough to permit removal of the required test specimens. The test assembly dimensions on either side of the groove shall be at least 6 inches (150 millimeters). The qualification test plate shall be prepared in accordance with Figure A2-I.

(d)Ferritic base material for the procedure qualification test shall meet the impact test requirements of the Construction Code and Owner's Requirements. If such requirements are not in the Construction Code and Owner's Requirements, the impact properties shall be determined by Charpy V-notch impact tests of the procedure qualification base material at or below the lowest service temperature of the item to be repaired. The location and orientation of the test specimens shall be similar to those required in A2.3.1(e) but shall be in the base metal.

(e) Charpy V-notch tests of the ferritic heat-affected zone (HAZ) shall be performed at the same temperature as the base metal test of A2.3.1(d). Number, location, and orientation of test specimens shall be as follows:

(1) The specimens shall be removed from a location as near as practical to a depth of one-half the thickness of the deposited weld metal. The coupons for HAZ impact specimens shall be taken transverse to the axis of the weld and etched to define the HAZ. The notch of the Charpy V-notch specimen shall be cut approximately normal to the material surface in such a manner as to include as much HAZ as possible in the resulting fracture.

(2) If the material thickness permits, the axis of a specimen shall be inclined to allow the root of the notch to be aligned parallel to the fusion line.

(3) If the test material is in the form of a plate or forging, the axis of the weld shall be oriented parallel to the principal direction of rolling or forging.

(4) The Charpy V-notch test shall be performed in accordance with SA-370. Specimens shall be in accordance with SA-370, Figure 11, Type A. The test shall consist of a set of three full-size 10 millimeters by 10 millimeters specimens. The lateral expansion, percent shear, absorbed energy, test temperature, orientation, and location of all test specimens shall be reported in the Procedure Qualification Record.

North Anna Unit 1 Proposed Alternative Nl-I4-CMP-001 Docket No. 50-338 Page 24 of3?

Attachment 1 Page 12 of 13 (f) The average lateral expansion value of the three HAZ Charpy V-notch specimens shall be equal to or greater than the average lateral expansion value of the three unaffected base metal specimens.

However, if the average lateral expansion value of the HAZ Charpy V-notch specimens is less than the average value for the unaffected base metal specimens and the procedure qualification meets all other requirements of this Attachment, either of the following shall be performed:

(1) The welding procedure shall be requalified.

(2) An Adjustment Temperature for the procedure qualification shall be determined in accordance with the applicable provisions of Paragraph NB-4335.2 of Section III, 2001 Edition with the 2002 Addenda of the ASME Code. The reference nil-ductility temperature (RT NDT) or lowest service temperature of the materials for which the welding procedure will be used shall be increased by a temperature equivalent to that of the Adjustment Temperature.

A2.3.2 Performance Qualification Welding operators shall be qualified in accordance with ASME Code Section IX.

A2.4 WELDING PROCEDURE REQUIREMENTS The welding procedure shall include the following requirements:

(a) The weld metal shall be deposited by the automatic or machine gas tungsten arc welding process.

(b) Dissimilar metal welds shall be made using A-No.8 weld metal (QW-442) for P-No. 8 to P-No. 1, 3, or 12 (A, B, or C) weld joints or F-No. 43 weld metal (QW-432) for P-No. 8 or 43 to P-No. 1, 3, or 12 (A, B, or C) weld joints.

(c) The area to be welded shall be buttered with a deposit of at least three layers to achieve at least lIS inch (3 millimeters) overlay thickness with the heat input for each layer controlled to within +/-10 percent of that used in the procedure qualification test. The heat input of the first three layers shall not exceed 45 kilojoule [kJ]/inch or 1.8 kJ/millimeter under any conditions. Particular care shall be taken in the placement of the weld layers of the austenitic overlay filler material at the toe of the overlay to ensure that the heat affected zone and ferritic base metal are tempered. Subsequent layers shall be deposited with a heat input not exceeding that used for layers beyond the third layer in the procedure qualification.

(d) The maximum interpass temperature for field applications shall be 350 degrees Fahrenheit (180 degrees Celsius) for all weld layers regardless of the interpass temperature used during qualification. The interpass temperature limitation of QW-406.3 need not be applied.

(e) The interpass temperature shall be determined by contact pyrometers. The measurements are taken multiple ~imes within each layer.

North Anna Unit 1 Proposed Alternative NI-I4-CMP-001 Docket No. 50-338 Page 25 of3?

Attachment 1 Page 13 of 13 if) Particular care shall be given to ensure that the weld region is free of all potential sources of hydrogen. The surfaces to be welded, filler metals, and shielding gas shall be suitably controlled.

Discard Transverse Side Bend Reduced SectionTensile Transverse Side Bend r-;

HAZ Charpy r-;

V-Notch r-:

Transverse Side Bend Reduced Section Tensile Transverse Side Bend Discard Fusion line Weld metal Heat affected zone (HAZ)

Note:

Base metal Charpy impact specimens are not shown. This figure illustrates a similar-metal weld.

Figure A2-1 Qualification Test Plate

North AnnaUnit 1 Proposed Alternative Nl-I4-CMP-00l DocketNo. 50-338 Page 26 of37 North Anna Unit 1 Proposed Alternative ATTACHMENT 2 Page 10f7 PROPOSED CHANGES TO ASME CODE SECTION XI APPENDIX VIII FOR COMPATIBILITY WITH THE PERFORMANCE DEMONSTRATION INITIATIVE PROGRAM SUPPLEMENT 11 . QUALIFICATION PDI PROGRAM:

REQUIREMENTS FOR FULL The Proposed Alternative to Supplement 11 STRUCTURAL OVERLAID WROUGHT Requirements AUSTENITIC PIPING WELDS Title Alternative: "Qualification Requirements for Overlaid Wrought Austenitic Piping Welds:

Basis: The title was clarified to be applicable for all overlays on wrought austenitic piping welds. The specific qualification shall detail the range of qualification.

1 0 SPECIMEN REQUIREMENTS 1.1 General. The specimen set shall conform to the following requirements.

(b) The specimen set shall consist of at least three Alternative: (b) The specimen set shall include specimens having different nominal pipe specimens with overlays not thicker than 0.1 inch diameters and overlay thicknesses. They shall more than the minimum thickness, nor thinner than include the minimum and maximum nominal pipe 0.25 inch of the maximum nominal overlay diameters for which the examination procedure is thickness for which the examination procedure is applicable. Pipe diameters within a range of 0.9 applicable.

to 1.5 times a nominal diameter shall be considered equivalent. If the procedure is Basis: To avoid confusion, the overlay thickness applicable to pipe diameters of 24-inch or larger, tolerance contained in the last sentence was the specimen set must include at least one reworded.

specimen 24-inch or larger but need not include the maximum diameter. The specimen set must include at least one specimen with overlay thickness within minus 0.1 inch to plus 0.25 inch of the maximum nominal overlay thickness for which the procedure is applicable.

(d) PIaw Conditions (1) Base metal flaws. All flaws must be cracks in Alternative: (1) All flaws must be in or near ...

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

(a) The use of alternative flaws shall be limited to

North Anna Unit 1 Proposed Alternative NI-I4-CMP-00I Docket No. 50-338 Page 27 of37 SUPPLEMENT 11- QUALIFICATION PDI PROGRAM:

REQUIREMENTS FOR FULL The Proposed Alternative to Supplement 11 STRUCTURAL OVERLAID WROUGHT Requirements AUSTENITIC PIPING WELDS when the implantation of 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 paragraph requires that all base metal flaws be cracks and to extend at least 75 percent through the base metal wall. Implanting a crack requires excavation of the base material on at least one side of the flaw. While this may be satisfactory for ferritic materials, it does not produce a useable axial flaw in austenitic materials because the sound beam, which normally passes only through base material, must now travel through weld material on at least one side, producing an unrealistic flaw response. To resolve this issue, the PDI program revised this paragraph to allow use of alternative flaw mechanisms under controlled conditions. For example, alternative flaws shall be limited to when implantation of cracks precludes obtaining an effective ultrasonic response, flaws shall be semi elliptical with a tip width of less than or equal to 0.002 inches, and at least 70 percent of the flaws in the detection and sizing test shall be cracks and the remainder shall be alternative flaws. The statement "intentional overlay fabrication flaws shall not interfere with ultrasonic detection or characterization of the base metal flaws " was included into paragraph 1.1(d)( 1). Additionally, to avoid confusion, the phrase "and the remainder shall be alternate flaws " was added to the second to last sentence of this first paragraph above.

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

Basis: The requirement for axially oriented overlay fabrication flaws was excluded from the PDI Program as an improbable scenario. Weld overlays are typically applied using automated gas tungsten arc welding techniques with the filler metal applied in a circumferential direction. Because resultant fabrication induced discontinuities would also be expected to have major dimensions oriented in the

North Anna Unit 1 Proposed Alternative NI-I4-CMP-001 Docket No. 50-338 Page 28 of37 SUPPLEMENT 11- QUALIFICATION PDI PROGRAM:

REQUIREMENTS FOR FULL The Proposed Alternative to Supplement 11 STRUCTURAL OVERLAID WROUGHT Requirements AUSTENITIC PIPING WELDS circumferential direction axial overlay fabrication flaws are unrealistic. The requirement for using IWA-3300 for proximity flaw evaluation was excluded; instead indications shall be sized based on their individual merits.

(2) Specimens shall be divided into base and Alternative: (2) Specimens shall be divided into overlay grading units. Each specimen shall base metal and overlay fabrication grading units.

contain one or both types of grading units. Each specimen shall contain one or both types of grading units. Flaws shall not interfere with ultrasonic detection or characterization of other flaws.

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

(a)(l) A base grading unit shall include at least 3 Alternative: (a)(l) A base metal grading unit inches of the length of the overlaid weld. The includes the overlay material and the outer 25 base grading unit includes the outer 25 percent of percent of the original overlaid weld. The base the overlaid weld and base metal on both sides. metal grading unit shall extend circurnferentially for The base grading unit shall not include the inner at least 1 inch and shall start at the weld centerline 75 percent of the overlaid weld and base metal and be wide enough in the axial direction to overlay material, or base metal-to-overlay encompass one half of the original weld crown and a interface. minimum of 0.50" of the adjacent base material.

Basis: The phrase "and base metal on both sides,"

was inadvertently included in the description ofa base metal grading unit. The PDI program intentionally excludes this requirement because some of the qualification samples include flaws on both sides of the weld. This paragraph was also modified to require that a base metal grading unit include at leastlinch of the length of the overlaid weld, rather than 3 inches.

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

material shall not be used as part of any overlay grading unit. Basis: Substituted terms provide clarification and are consistent with 1d(1) above. The PDI program adjusts for this conservative change for excluding this type grading unit.

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

North Anna Unit 1 Proposed Alternative NI-I4-CMP-001 Docket No. 50-338 Page 29 of37 SUPPLEMENT 11 . QUALIFICATION PDI PROGRAM:

REQUIREMENTS FOR FULL The Proposed Alternative to Supplement 11 STRUCTURAL OVERLAID WROUGHT Requirements AUSTENITIC PIPING WELDS weld and base metal shall exist on either side of grading unit to preclude interfering reflections from the base grading unit. The segment of weld length adjacent flaws.

used in one base grading unit shall not be used in another base grading unit. Base grading units Basis: Modified to require sufficient unflawed need not be uniformly spaced around the overlaid weld and base metal to exist on all sides of specimen. the grading unit to preclude interfering reflections from adjacent flaws, rather than the 1 inch requirement.

(b)(l) An overlay grading unit shall include the Alternative: (b)(l) An overlay fabrication grading overlay material and the base metal-to-overlay unit shall include the overlay material and the base interface of at least 6 in2* The overlay grading metal-to-overlay interface for a length of at least 1 unit shall be rectangular, with minimum inch.

dimensions of 2 inches.

Basis: The PDf program 'reduces the base metal-to-overlay interface to at least 1 inch (in lieu of a minimum of2 inches) and eliminates the minimum rectangular dimension. This criterion is necessary to allow use of existing examination specimens that were fabricated in order to meet NRC Generic Letter 88-01. This criterion may be more challenging than the ASME Code because ofthe variability associated with the shape ofthe grading unit.

(b)(2) An overlay grading unit designed to be Alternative: (b)(2) Overlay fabrication grading unflawed shall be surrounded by unflawed overlay units designed to be unflawed shall be separated by material and unflawed base metal-to-overlay unflawed overlay material and unflawed base metal-interface for at least 1 inch around its entire to-overlay interface for at least 1 inch at both ends.

perimeter. The specific area used in one overlay Sufficient unflawed overlaid weld and base metal grading unit shall not be used in another overlay shall exist on both sides of the overlay fabrication grading unit. Overlay grading units need not be grading unit to preclude interfering reflections from spaced uniformly about the specimen. 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: Paragraph 1.1 (e)(2)(b)(2) states that 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, rather than around its entire perimeter.

(b)(3) Detection sets shall be selected from Table Alternative: Base metal grading units, ten unflawed VIII-S2-I. The minimum detection sample set is base metal grading units, five flawed overlay five flawed base grading units, ten unflawed base fabrication grading units, and ten unflawed overlay grading units, five flawed overlay grading units, fabrication grading units. For each type of grading

North Anna Unit 1 Proposed AlternativeN1-14-CMP-001 DocketNo. 50-338 Page 30 of37 SUPPLEMENT 11 - QUALIFICATION PDI PROGRAM:

REQUIREMENTS FOR FULL The Proposed Alternative to Supplement 11 STRUCTURAL OVERLAID WROUGHT Requirements AUSTENITIC PIPING WELDS and ten unflawed overlay grading units. For each unit, the set shall contain at least twice as many type of grading unit, the set shall contain at least unflawed as flawed grading units. For initial twice as many unflawed as flawed grading units. procedure qualification, detection 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: Clarified the guidance for initial procedure qualifications versus qualifying new values of essential variables.

(f) Sizing Specimen (1) The minimum number of flaws shall be ten. Alternative: (1) The ...least 40 percent of the flaws At least 30 percent of the flaws shall be overlay shall be open to the inside surface. Sizing sets shall fabrication flaws. At least 40 percent of the flaws contain a distribution of flaw dimensions to assess shall be cracks open to 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: Clarified the guidance for initial procedure qualifications versus qualifying new values of essential variables and is consistent with l.l(d)(l) above.

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

circumferentially.

Basis: Clarified wording to be consistent with l.l(d)(l) above.

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

Basis: Clarified wording to be consistent with 1.1(d)(l) above.

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

the results and presenting the results to the candidate. Divulgence of particular specimen Basis: Clarified wording to.describe process.

results or candidate viewing of unmasked specimens after the performance demonstration is prohibited.

2.1 Detection Test

North Anna Unit 1 Proposed Alternative NI-I4-CMP-001 Docket No. 50-338 Page 31 of37 SUPPLEMENT 11

• QUALIFICATION PDI PROGRAM:

REQUIREMENTS FOR FULL The Proposed Alternative to Supplement 11 STRUCTURAL OVERLAID WROUGHT Requirements AUSTENITIC PIPING WELDS Flawed and unflawed grading units shall be Alternative: Flawed (base metal or overlay randomly mixed. Although the boundaries of fabrication) ... each specimen.

specific grading units shall not be revealed to the candidate, the candidate shall be made aware of Basis: Clarified wording similar to 1.1(e)(2) above.

the type or types of grading units (base or overlay) that are present for each specimen.

2.2 Length Sizing Test (d) For flaws in base grading units, the candidate Alternative: (d) For ... base metal grading ... 25 shall estimate the length of that part of the flaw percent of the base metal wall thickness.

that is in the outer 25 percent of the base wall thickness. Basis: Clarified wording for consistency and to be consistent with 1.1(d)(1) above.

2.3 Depth Sizing Test For the depth sizing test, 80 percent of the flaws Alternative: The depth sizing test may be shall be sized at a specific location on the surface conducted separately or in conjunction with the of the specimen identified to the candidate. For detection test.

the remaining flaws, the regions of each specimen containing a flaw to be sized shall be identified to Basis: Clarified wording to better describe process.

the candidate. The candidate shall determine the maximum depth of the flaw in each region.

3.0 ACCEPTANCE CRITERIA 3.1 Detection Acceptance Criteria Examination procedures, equipment, and Alternative: Examination procedures are qualified personnel are qualified for detection when the for detection when:

results of the performance demonstration satisfy a. All flaws within the scope of the procedure are the acceptance criteria of Table Vlll-S2-1 for both detected and the results of the performance detection and false calls. The criteria shall be demonstration satisfy the acceptance criteria of satisfied separately by the demonstration results Table VIII-S2-1 for false calls.

for base grading units and for overlay grading b. At least one successful personnel demonstration units. has been performed meeting the 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.

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: Clarified wording to better describe the difference between procedure qualification and equipment and personnel qualifications.

3.2 Sizin~ Acceptance Criteria (a)The RMS error of the flaw length Alternative: (a) The ...base metal flaws are ... 75

North Anna Unit 1 ProposedAlternative NI-I4-CMP-001 Docket No. 50-338 Page 32 of37 SUPPLEMENT 11 . QUALIFICATION POI PROGRAM:

REQUIREMENTS FOR FULL The Proposed Alternative to Supplement 11 STRUCTURAL OVERLAID WROUGHT Requirements AUSTENITIC PIPING WELDS measurements, as compared to the true flaw percent through-base-metal 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 measured at the 75 percent through-base- 1.1(d)(l) above.

metal position.

(b) All extens ions of base metal cracking into the Alternative: This requirement is omitted.

overlay material by at least 0.1 inch are reported as being intrusions into the overlay material. Basis: The requirement for reporting all extensions of cracking into the overlay is omitted from the PDf Program because it is redundant to the RMS calculations performed in paragraph 3.2(c) and its presence adds confusion and ambiguity to depth sizing as required by paragraph 3.2(c). This also makes the weld overlay program consistent with the supplement 2 depth sizing criteria.

North Anna Unit 1 Proposed Alternative Nl-I4-CMP-00I Docket No. 50-338 Page 33 of 37 North Anna Unit 1 Proposed Alternative ATTACHMENT 3 Page 1 of5 COMPARISON OF ASME CODE CASE N-504-4 AND APPENDIX Q OF ASME CODE SECTION XI WITH THE PROPOSED ALTERNATIVE OF ATTACHMENT 1 FOR WELD OVERLAY, CODE CASE N-740-2 ASME Code Case N-504-4 and Appendix Q of ASME Code Section XI Proposed Alternative of Attachment T-Code Case N-740-2 ASME Code Case N-504-4 provides requirements for reducing a defect to a The proposed alternative of Attachment 1 provides requirements for installing flaw of acceptable size by deposition of weld reinforcement (weld overlay) on a repair or preemptive full structural weld overlay by deposition of weld the outside surface of the pipe using austenitic stainless steel filler metal as an reinforcement (weld overlay) on the outside surface of the item using Nickel alternative to defect removal. ASME Code Case N-504-4 is applicable to Alloy 52M filler metal. Attachment 1 is applicable to dissimilar metal welds austenitic stainless steel piping only. According to Regulatory Guide 1.147, associated with nickel alloy materials. The proposed alternative of Attachment Revision 16, the provisions of Nonmandatory Appendix Q of ASME Code 1 is based on ASME Code Case N-740~2.

Section XI must also be met when using this Case. Therefore, the Code Case N-504-4 requirements presented below have been supplemented by Appendix Q of ASME Code Section XI.

General Requirements General Requuements ASME Code Case N-504-4 and Appendix Q are only applicable to P-No. 8 As specified in paragraph 1.1(a), the proposed alternative is applicable to austenitic stainless steels. dissimilar metal 82/182 welds joining P-No. 3 to P-No. 8 or 43 materials and P-No. 8 to P-No. 43 materials. It is also applicable to austenitic stainless steel welds joining P-No. 8 materials.

Basis: ASME Code Case N-504-4 and Appendix Q are applicable to austenitic weld overlays ofP-No. 8 austenitic stainless steel materials. Based on ASME Code Case N-740-2, the proposed alternative ofAttachment 1 was specifically written to address the application of weld overlays over dissimilar metal welds and austenitic stainless steel welds.

According to paragraph (b) of ASME Code Case N-504-4 as supplemented by The weld filler metal and procedure requirements of paragraph 1.1(b) are Appendix Q, weld overlay filler metal shall be low carbon (0.035 percent equivalent to ASME Code Case N-504-4 and Appendix Q except as noted max.) austenitic stainless steel applied 360 degrees around the circumference below:

of the pipe, and shall be deposited using a Welding Procedure Specification for groove welding, qualified in accordance with the Construction Code and

• Weld overlay filler metal shall be austenitic Nickel Alloy 52M Owner's Requirements and identified in the Repair/Replacement Plan. (ERNiCrFe-7A) filler metal which has a chromium content of at least 28 percent. If a stainless steel buffer layer is used as permitted by N-740-2, the ferrite content of the filler material shall be 5 - l5FN as required by the Construction Code.

North Anna Unit 1 Proposed Alternative NI-14-CMP-001 Docket No. 50-338 Page 34 of 37 As an alternative to post-weld heat treatment, the provisions for "Ambient Temperature Temper Bead Welding" may be used on the ferritic nozzle as described in Attachment 1.

Basis: The weld overlay shall be deposited with ERNiCrFe-7A (Alloy 52M) filler metal. It has been included into ASME Code Section IX as F-No. 43 filler metals. Containing 28.0 - 31.5 percent chromium (roughly twice the chromium content of 82/182 filler metal), this filler metal has excellent resistance to primary water stress corrosion cracking. This point has been clearly documented in EPRI Technical Report MRP-115, Section 2.2[5]. Regarding the welding procedure specification (WPS), the requirements ofAttachment 2 provide clarification that the WPS used for depositing weld overlays must be qualified as a groove welding procedure to ensure that mechanical properties ofthe WPS are appropriately established. Where welding is performed on ferritic nozzles, an ambient temperature temper bead WPS shall be used.

Suitability of an ambient temperature temper bead WPS is addressed in Section 5 ofthis Request.

According to paragraph (e) of AS:ME Code Case N-504-4 as supplemented by The weld overlay described in Attachment 1 is deposited using nickel Alloy Appendix Q, the weld reinforcement shall consist of at least two weld layers 52M filler metal instead of austenitic stainless steel filler metals. Therefore, having as-deposited delta ferrite content of at least 7.5 FN. The first layer of the basis for crediting the first layer towards the required design thickness is weld metal with delta ferrite content of at least 7.5 FN shall constitute the first based on the chromium content of the nickel alloy filler metal. According to layer of the weld reinforcement that may be credited toward the required paragraph Al.l(e), the first layer of nickel Alloy 52M deposited weld metal thickness. Alternatively, first layers of at least 5 FN provided the carbon may be credited toward the required thickness provided the portion of the layer content is determined by chemical analysis to be less than 0.02 percent. over the austenitic base material, austenitic weld, and the associated dilution zone from an adjacent ferritic base material contains at least 24 percent chromium. The chromium content of the deposited weld metal may be determined by chemical analysis of the production weld or from a representative coupon taken from a mockup prepared in accordance with the WPS for the production weld.

Basis: The weld overlay shall be deposited with ERNiCrFe-7A (Alloy 52M) filler metal. Credit for the first weld layer may not be taken toward the required thickness unless it has been shown to contain at least 24 percent chromium This is a sufficient amount of chromium to prevent primary water stress corrosion cracking. Section 2.2 ofEPRI Technical Report MRP-115 states the following: "The only well explored effect ofthe compositional differences among the weld alloys on primary water stress corrosion cracking is the influence of chromium. Buisine, et al. (Reference 24) evaluated the primary water stress corrosion cracking resistance ofnickel-based weld metals with various chromium contents ranging from about 15 percent to 30 percent

North Anna Unit 1 Proposed Alternative N1-14-CMP-001 Docket No. 50-338 Page 35 of3?

chromium Testing was performed in doped steam and primary water. Alloy 182, with about 14.5 percent chromium, was the most susceptible. Alloy 82 with 18-20 percent chromium took three or four times longer to crack. For chromium contents between 21 and 22 percent, no stress corrosion crack initiation was observed ... n Design and Crack Growth Considerations Design and Crack Growth Considerations The design and flaw characterization provisions of AS:ME Code Case N504-4, The design and flaw evaluation provisions in the proposed alternative are the paragraphs (f) and (g) as supplemented by Appendix Q are summarized below: same as AS:ME Code Case N-504-4 as supplemented in Appendix Q with the exceptions below. The proposed design and flaw evaluation provisions are (i) Flaw characterization and evaluation are based on the as-found flaw. Flaw based on postulated flaws or as-found flaws.

evaluation of the existing flaws is based on IWB-3640 for the design life.

• For weld overlay crack growth evaluations, a flaw with a depth of 10 percent

• Multiple circumferential flaws shall be treated as one flaw of length equal to and a circumference of 360 degrees shall be assumed or the as-found flaw size the sum of the lengths of the individual flaws. shall be used. The size of the flaws shall be projected to the end of the design life of the overlay. Crack growth, including both stress corrosion and fatigue

• Circumferential flaws are postulated as 100 percent through-wall for the crack growth, shall be evaluated in the materials in accordance with IWB-entire circumference with one exception. When the combined length of 3640. If the flaw is at or near the boundary of two different materials, circumferential flaws does not exceed 10 percent of the circumference, the evaluation of flaw growth in both materials is required.

flaws are only assumed to be 100 percent through-wall for the combined length of the flaws. Basis: A preservice volumetric examination shall be performed after application ofthe weld overlay using an ASME Code Section XI, Appendix VllI

• For axial flaws 1.5 inches or longer, or for five or more axial flaws of any (as implemented through PDl) examination procedure. This examination shall length, the flaws shall be assumed to be 100 percent through-wall for the axial verify that there is no cracking in the upper 25 percent ofthe original weld and length of the flaw and entire circumference of the pipe. base material for afull structural weld overlay. The preservice examination shall also demonstrate that the assumed through-wall crack depths are (ii) For four or fewer axial flaws less than 1.5 inches in length, the weld conservative. However, if any crack-like flaws are identified in the upper 25 overlay thickness need only consist of two or more layers of weld metal percent ofthe original weld or base material by the preservice examination, meeting the deposit analysis requirements. then the as-found flaw (postulated 75 percent through-wall flaw plus the portion ofthe flaw in the upper 25 percent) shall be usedfor the crack growth (iii) The axial length and end slope of the weld overlay shall cover the weld analysis. With regard to design, flaws are considered to be either 75 percent and HAZs on each side of the weld, and shall provide for load redistribution through-wall for assumed crack depth or 100 percent through the original from the item into the weld overlay and back into the item without violating weld when aflaw is identified by inspection and no structural credit is taken applicable stress limits of the Construction Code. Any laminar flaws in the for the weld. All other requirements are equivalent to ASME Code Case N-weld overlay shall be evaluated in the analysis to ensure that load redistribution 504-4 as supplemented by Appendix Q.

complies with the above. These requirements are usually met if the weld overlay extends beyond the projected flaw by at least 0.75(Rt)lI2.

(iv) Unless specifically analyzed, the end transition slope of the overlay shall not exceed 45 degrees, and a slope of not more than 1:3 is recommended.

(v) The overlay design thickness of items shall be based on the measured

North Anna Unit 1 Proposed Alternative N1-I4-CMP-001 Docket No. 50-338 Page 36 of 37 diameter, using only the weld overlay thickness conforming to the deposit analysis requirements. The combined wall thickness at the weld overlay, any planar flaws in the weld overlay, and the effects of any discontinuity (for example, another weld overlay or reinforcement for a branch connection) within a distance of 0.75(Rt)112 from the toes of the weld overlay, shall be evaluated and meet the requirements of IWB-, IWC-, or IWD-3640.

(vi) The effects of any changes in applied loads, as a result of weld shrinkage or existing flaws previously accepted by analytical evaluation shall be evaluated in accordance with IWB-3640, IWC-3640, or IWD-3640, as applicable.

Examination and Inspection Examination and Inspection Acceptance Examination The acceptance standards in Attachment 1 are identical to those of paragraph Q-4100(c) states that the examination volume in Figure Q-4100-1 shall be Q-4100(c) except that the proposed method includes requirements and ultrasonically examined to assure adequate fusion (that is, adequate bond) with clarifications that are not included in Appendix Q. First, it specifies that the the base metal and to detect welding flaws, such as inter-bead lack of fusion, ultrasonic examination shall be conducted at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after completing inclusions, or cracks. Planar flaws shall meet the preservice examination the third layer of the weld overlay when ambient temperature temper bead standards of Table IWB-35 14-2. Laminar flaws shall meet the following: welding is used. Secondly, it provides the following clarifications:

• The interface C-D between the weld overlay and the weld includes the bond and the HAZ from the weld overlay.

• In applying the acceptance standards, wall thickness "t;" shall be the thickness of the weld overlay.

Basis: Appendix Q is applicable to austenitic stainless steel materials only; therefore, ambient temperature temper bead welding would not be applicable.

It is applicable to welding performed in the proposed alternative. When ambient temperature temper bead welding is performed, nondestructive examinations must be performed at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after completing the third layer of the weld overlay to allow sufficient time for hydrogen cracking to occur (if it is to occur). Technicaljustificationfor starting the 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 layer of the weld overlay is provided in Section 5 ofthe Request. The other two changes are simply clarifications that were added to ensure that the examination requirements were appropriately performed.

Q-4100(c)(l) states that laminar flaws shall meet the acceptance standards of The acceptance standards of the proposed method are identical to paragraph Q-Table IWB-35 14-3. 4100(c)(1) except that the proposal includes the additional limitation that the total laminar flaw shall not exceed 10 percent of the weld surface area and that no linear dimension of the laminar flaw area exceeds 3.0 inches

North Anna Unit 1 Proposed Alternative NI-I4-CMP-00I Docket No. 50-338 Page 37 of 37 Basis: These changes were made to provide additional conservatism to the weld overlay examination and to reduce the size ofthe un-inspectable volume beneath a laminar flaw. See Section 5 ofthis Requestfor additional information.

Q-4100(c)(4) allows the performance of radiography in accordance with the The acceptance standards of the proposed alternative do not include the Construction Code as an alternative to Q-4100(c) (3). radiographic alternative of paragraph Q-4100(c)(4).

Basis: The ultrasonic examinations performed in accordance with the proposed alternative are in accordance with ASME Code,Section XI, Appendix VIII, Supplement 11 as implemented through the PDl. These examinations are considered more sensitive for detection ofdefects, either fromfabrication or service-induced, than either ASME Code Section III radiographic or ultrasonic methods. Furthermore, construction type flaws have been included in the PDI qualification sample sets for evaluating procedures and personnel. See Section 5 ofthis Request for additional justification.

Preservice Inspection Preservice Inspection Q-4200(b) states that the preservice examination acceptance standards of Table The acceptance standards of the proposed alternative are identical to paragraph IWB-35 14-2 shall be met for the weld overlay. Cracks in the outer 25 percent Q-4200(b) except proposed alternative includes the following statement: "In of the base metal shall meet the design analysis requirements of Q-3000. applying the acceptance standards, wall thickness, shall be the thickness of the weld overlay."

Basis: This provision is actually a clarification that the nominal wall thickness of Table lWB-3514-2 shall be considered the thickness ofthe weld overlay. It must be remembered that the acceptance standards were originally written for the welds identified in IWB-2500. Because IWB-2500 does not address weld overlays, this clarification was provided to avoid any potential confusion.

However, defining the weld overlay thickness as the nominal wall thickness of Table lWB-3514-2 has always been the practice since it literally becomes the new design wall ofthe piping or component nozzle.

Pressure Testing Pressure Testing (h) The completed repair shall be pressure tested in accordance with IWA- The pressure testing requirements included in the alternative are similar to 5000. A system hydrostatic test is required if the flaw penetrated the pressure paragraph (h) of ASME Code Case N-504-4 except that only a system leakage boundary. A system leakage test may be performed if pressure boundary is not test per IWA-5000 is required.

penetrated.

Serial No.11-120 Docket No. 50-338 Alternative Request N1-14-CMP-001 ENCLOSURE 2 COMMITMENT

SUMMARY

ALTERNATIVE REQUEST N1-14-CMP-001 USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR TECHNIQUE NORTH ANNA POWER STATION UNIT 1 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

Serial No.11-120 Docket No. 50-338 Alternative Request N1-14-CMP-001 Commitments Associated with N1-14-CMP-001 Commitment Due Date

1. Summaries of the results of the analyses listed in Items a through Prior to entry into Mode c below will be submitted to the NRC prior to entry into Mode 4 4 following the following completion of the weld overlays. completion of the weld overlays

a. Nozzle specific stress analyses shall be performed to establish a residual stress profile in the nozzle. Inside diameter (10) weld repairs shall be assumed in these analyses to effectively bound any actual weld repairs that may have occurred in the nozzles. The analysis shall then simulate application of the weld overlays to determine the final residual stress profile.

Post weld overlay residual stresses at normal operating conditions shall be shown to result in an improved stress state in the component that reduces the probability for further crack propagation due to primary water stress corrosion cracking.

b. Fracture mechanics analyses shall be performed to predict crack growth. Crack growth due to primary water stress corrosion cracking and fatigue crack growth in the original dissimilar metal weld shall be evaluated. The crack growth analyses shall consider all design loads and transients, plus the post weld overlay through-wall residual stress distributions, and shall demonstrate that the assumed cracks shall not grow beyond the design bases for the weld overlays (that is, through the original dissimilar metal weld thickness and any additional allowance for crack growth within the weld overlay) for the time period until the next scheduled inservice inspection. The crack growth analyses shall determine the time period for the assumed cracks to grow to the design basis for the weld overlay.

c. The analyses shall demonstrate that the application of the weld overlays does not impact the conclusions of the existing nozzle stress reports. ASME Code Section III stress and fatigue criteria shall be met for the regions of the overlays remote from observed (or assumed) cracks.

2. The following information will be submitted to the NRC within 14 Within 14 days of days of completion of the final ultrasonic examination of the completion of the final overlaid welds. ultrasonic examination

• a listing of indications detected of the overlaid welds

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