NL-08-0877, Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i) Application of Dissimilar Weld Full-Structural Weld Overlays Alternative Lsi ALT-08-02 Version 1

Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i) Application of Dissimilar Weld Full-Structural Weld Overlays Alternative Lsi ALT-08-02 Version 1

ML090260295
Person / Time
Site:	Hatch
Issue date:	06/11/2008
From:	David Jones Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-08-0877
Download: ML090260295 (41)

Text

David H. Jones Southern Nuclear Vice President Operating Company, Inc.

Engineering 40 Inverness Center Parkway Birmingham. Alabama 35242 Tel 205.992.5984 Fax 205.992.0341 SOUTHERN.\.

COMPANY June 11, 2008 Energy to Serve ~"r World'"

Docket Nos.: 50-321 NL-08-0877 50-366 U. S. Nuclear RegUlatory Commission ATIN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant - Units 1 & 2 Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative lSI ALT-08-02 Version 1 Ladies and Gentlemen:

Pursuant to 10 CFR 50.55a(a)(3)(i), Southern Nuclear Operating Company (SNC) hereby requests NRC approval of proposed alternative ISI-ALT-08-02 Version 1 to allow the application of full-structural weld overlays over dissimilar metal welds.

This alternative is for the Hatch Nuclear Plant 4th lSI Interval starting on January 1, 2006 and ending December 31,2015. The details of the 10 CFR 50.55a alternative request are enclosed.

Approval is requested by January 9, 2009 to support the Plant Hatch Unit 2 refueling outage beginning February 9, 2009.

This letter contains no NRC commitments. If you have any questions. please advise.

D. H. Jone Vice Presi ent - Engineering DHJ/PAH/daj

U. S. Nuclear Regulatory Commission NL-08-0877 Page 2

Enclosure:

Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Metal Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 cc: Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. D. R. Madison, Vice President - Hatch RTYPE: CHA02.004 U. S. Nuclear Regulatory Commission Mr. L. A. Reyes, Regional Administrator Mr. R. E. Martin, NRR Project Manager - Hatch Mr. J. A. Hickey, Senior Resident Inspector - Hatch

Edwin I. Hatch Nuclear Plant - Units 1 & 2 Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 Plant Site-Hatch Nuclear Plant Units 1 and 2 (HNP-1&2).

Unit:

Interval Fourth ISI Interval extending from January 1, 2006 through December 31, Dates: 2015.

Requested Date for Approval is requested by January 9, 2009.

Approval :

ASME Code Listed below are the welds subject to this alternative.

Components Affected: HNP-1 There are fourteen (14) Category B-F, Reactor Pressure Vessel (RPV) nozzle to safe-end dissimilar metal (DM) welds. The nozzles are fabricated from SA-508, CL. 2 (P No. 3), the safe-ends are fabricated from SA-182, F-304 (P No. 8), and the weld material is Alloy 82/182 (F No. 43). These 14 welds are described below.

• Two 4 Jet Pump Instrument RPV Nozzle to Safe-End Welds

• Two 10 Core Spray Nozzle Safe-End Welds

• Eight 12 Recirculation Inlet Nozzle to Safe-End Welds

• Two 28 Recirculation Outlet Nozzle to Safe-End Welds There are four small diameter Category B-F, RPV nozzle to safe-end DM welds.

The RPV nozzles are fabricated from Inconel SB-166 (P No. 43), the safe-ends are fabricated from SA-182, F304 (P No. 8) and the weld material is Alloy 82/182 (F No. 43). These four welds are described below.

Three 2 Instrument Nozzle to Safe-End Welds One 2 Standby Liquid Control Nozzle to Safe-End Weld Additionally, there is one Category B-J 24 Residual Heat Removal carbon steel valve body to stainless steel extension piece DM weld. The valve body is fabricated from A-352-LCB (P No. 1), the extension piece is fabricated from F304 stainless steel (P No. 8) and the weld material is INCO-WELD A (F No. 43).

HNP-2 There are sixteen (16) Category B-F, Reactor Pressure Vessel (RPV) nozzle to safe-end DM welds. The nozzles are fabricated from SA-508, CL. 2 (P No. 3), the safe-ends are fabricated from SA-182, F-304 (P No. 8), and the weld material is Alloy 82/182 (F No. 43). These 16 welds are described below.

• Two 4 Jet Pump Instrument RPV Nozzle to Safe-End Welds

• Two 10 Core Spray Nozzle Safe-End Welds

• Ten 12 Recirculation Inlet Nozzle to Safe-End Welds Page 1 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1

• Two 28 Recirculation Outlet Nozzle to Safe-End Welds There is one Category B-F, RPV nozzle to 5.375 (nominal outside diameter) cap DM weld. The Control Rod Drive (CRD) Return nozzle is fabricated from SA-508, CL. 2 (P No. 3), the cap is fabricated from SB-166 (P No. 43), and the weld material is Alloy 82/182 (F No. 43).

There are four small diameter Category B-F, RPV nozzle to safe-end DM welds.

The nozzles are fabricated from Inconel SB-166 (P No. 43), the safe-ends are fabricated from SA-182, F304 (P No. 8) and the weld material is Alloy 82/182 (F No. 43). These four welds are described below.

• Three 2 Instrument Nozzle to Safe-End Welds

• One 2 Standby Liquid Control Nozzle to Safe-End Weld There are eight Category B-F Feedwater 12 Alloy 600 safe-end (P. No. 43) to carbon steel piece (P No. 1) DM welds. The weld material is Alloy 82/182 (F No.

43).

There are four Category B-F Feedwater 12 carbon steel transition piece (P No. 1) to Alloy 600 safe-end (P. No. 43) DM welds. The weld material is Alloy 82/182 (F No. 43).

There are two Category B-J 24 and one 20 Residual Heat Removal A-106 GR B carbon steel piping (P No. 1) to F-316 Nuclear Grade stainless steel piping DM welds (P- No. 8). The weld material is Alloy 82/182 (F No. 43).

Additionally, there are three Category B-J Feedwater 12 Alloy 600 safe-end extension (P. No. 43) to Alloy 600 safe-end (P. No. 43) similar metal welds. The weld material is Alloy 82/182 (F No. 43). ASME Section XI defines these welds as similar metal welds; however, since the weld material is Alloy 82/182, the same type of cracking may occur that occurs in the DM welds. (There were originally four similar metal welds; however, the fourth weld was previously overlaid due to an unacceptable indication).

Applicable The applicable Code edition and addenda is ASME Section XI, Rules for Inservice Code Edition Inspection of Nuclear Power Plant Components, 2001 Edition with Addenda and Addenda: through 2003. The exception is that for ASME Section XI, Appendix VIII, the 2001 Edition of Section XI will be used. This exception is based on 10 CFR 50.55a(b)(2)(xxiv) which states, The use of Appendix VIII and the supplements to Appendix VIII and Article I-3000 of Section XI of the ASME BPV Code, 2002 Addenda through the latest edition and addenda incorporated by reference in paragraph (b)(2) of this section, is prohibited.

NOTE Unless identified otherwise, all Code references provided herein are to ASME Section XI.

Page 2 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 Applicable IWA-4110 of ASME Section XI requires that repairs of welds be performed in Code accordance with Article IWA-4000. IWA-4300 requires that defects be removed or Requirements: reduced to an acceptable size.

Reason for Alloy 82/182 weld configurations may have leakage or unacceptable indications Request: during 4th Interval examinations. In this case, a full-structural overlay is the preferred method of repair. Additionally, due to weld configurations, there are Alloy 82/182 welds at HNP-1&2 that have significant issues with meeting the industry requirements for the examination of DM welds. In select cases, overlay of the Alloy 82/182 welds is the preferred manner of solving these significant examination issues. However,Section XI of the American Society of Mechanical Engineers, Boiler and Pressure Vessel Code (Section XI Code) does not provide rules for the design of weld overlays or for repairs without removal of flaws. Additionally, Code Case N-504-3, which has been approved by the NRC for use, does not provide the methodology for overlaying nickel alloy welds. Therefore, this alternative is required.

Proposed Proposed Alternative Alternative and Basis for Contingency Overlay Repairs - This proposed alternative may be used as a repair Use: for unacceptable indications or for through-wall leaks. If through-wall leakage is detected at any of the Alloy 82/182 welds, a contingency full structural weld overlay (FSWOL) is an option. Section 2.0(a) defines crack-growth requirements and section 2.0(b) defines the design requirements.

Preemptive Overlays - As a conservative measure, preemptive FSWOLs may be applied to Alloy 82/182 welds where the ultrasonic examination is determined to be extremely limited. Section 2.0(a) defines crack-growth requirements and section 2.0(b) defines the design requirements.

In lieu of using the IWA-4000 Repair Procedures in the Section XI Code, SNC proposes to use the following alternative for the design, fabrication, pressure testing, and examination of the weld overlays. This alternative provides an acceptable methodology for reducing a defect in austenitic nickel alloy weld joints to an acceptable size by increasing the wall thickness through deposition of a weld overlay. The methodology is shown below.

1.0 General Requirements:

(a) An FSWOL will be applied by deposition of weld reinforcement (weld overlay) over the Alloy 82/182 weld and the two components on either side of the weld. The weld reinforcement will consist of Alloy 52/152. (Note: As used in this alternative, the use of Alloy 52/152 refers to the family of filler metals which includes filler metals such as 52, 52M, 52MS, etc.)

Page 3 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 When components subject to being overlaid contain levels of trace chemicals (e.g., sulfur) that could cause unacceptable indications in the Alloy 52/152 weld, an initial layer of low carbon (0.035% max.) austenitic stainless steel and/or an austenitic nickel alloy may be applied as a buffer between the base metal and the Alloy 52/152 overlay. This buffer will be considered as a non-credited layer and will provide an acceptable chemical composition to apply the FSWOL. Depending on the chemical composition of the base materials where the weld overlay is to be applied, there may be different ways to apply the first layer of weld material. SNC considered the effects of the buffer layer on the requirements previously set forth in this alternative. Significant points are:

Code Case N-740, from which this alternative is derived, provides a methodology for the application of low carbon austenitic stainless and austenitic nickel alloys.

This non-credited buffer layer will not be included in calculations required by this alternative.

Since the FSWOL over the Alloy 82/182 weld will continue to consist of Alloy 52/152, there will be no effect on the ability of the overlay to stop the progress of stress corrosion cracking (SCC).

A review of the geometry by SNC and EPRI NDE personnel indicated that there will be no appreciable effect on the performance of ultrasonic examinations.

No effects detrimental to the structure will be introduced by addition of the non-credited buffer layer.

The figures in Appendix 6 provide typical sketches of the Alloy 52/152 overlay and the materials for each component. The figures are:

• Figure 1 is a typical RPV nozzle to safe-end weld with an overlay.

• Figure 2 is the RPV CRD Return nozzle to cap weld with an overlay.

• Figure 3 shows an Inconel nozzle to stainless steel safe-end weld with an overlay. Typically, this configuration is used for RPV instruments and for Standby Liquid Control.

• Figure 4 is a typical Unit 2 Feedwater Inconel safe-end configuration.

The overlay is not shown, because due to the close proximity of adjacent welds, multiple welds could require overlay to maintain an inspectable configuration.

Due to the base metal chemical composition, a non-credited layer (not shown in the figures) may be applied as a buffer. Specific dimensions and the overlay thickness are will be documented in the design package.

Prior to deposition of the non-credited buffer layer, the surface will be Page 4 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 examined by the liquid penetrant method. Indications larger than 1/16-inch shall be removed, reduced in size, or corrected 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 correction of indications is required, the area where the weld overlay is to be deposited, including any local repairs or initial weld overlay layer, shall be examined by the liquid penetrant method. The area shall contain no indications greater than 1/16-inch prior to the application of the structural layers of the weld overlay.

Since no credit is being taken for the non-credited buffer layer, the non-credited buffer layer will not be further discussed in this proposed alternative.

(b) The Alloy 52/152 weld overlay filler metal is an austenitic nickel alloy having a chromium (Cr) content of at least 28%. The weld overlay is applied 360 degrees around the circumference of the item, e.g., safe end to nozzle weld, and will be deposited using a Welding Procedure Specification (WPS) for groove welding, qualified in accordance with the Construction Code and Owners requirements and identified in the Repair/Replacement Plan. As an alternative to the post-weld heat treatment requirements of the Construction Code and Owners requirements, the provisions for ambient temperature temperbead welding will be used on the ferritic nozzles. (See Ambient Temperature Temperbead Welding, which is located in Appendix 1 to this proposed alternative). The maximum area of an individual weld overlay on the finished surface of the ferritic material shall be no greater than 300 square inches.

(c) Prior to deposition of the FSWOL, the surface will be examined by the liquid penetrant method. Indications larger than 1/16-inch shall be removed, reduced in size, or corrected 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 correction of indications identified in 1.0(c) is required, the area where the weld overlay is to be deposited, including any local repairs or initial weld overlay layer, shall be examined by the liquid penetrant method.

The area shall contain no indications greater than 1/16-inch prior to the application of the structural layers of the weld overlay.

Page 5 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 (d) Weld overlay deposits shall meet the following requirements:

The austenitic nickel alloy weld overlay shall consist of at least two weld layers deposited using a filler material such as that identified in 1.0(b). The first layer of weld metal deposited may not be credited toward the required thickness. Alternatively, for BWR applications, a 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 20% 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 WPS for the production weld.

(e) Welding will only be performed for applications predicted not to have exceeded a thermal neutron fluence of 1 x 1017 (E< 0.5 eV) neutrons per cm2 prior to welding.

2.0 Crack Growth Considerations and Design (a) Crack Growth Considerations - Crack growth calculations will be performed as part of a design package. Flaw characterization and evaluation requirements shall be based on the as-found flaw in the case of a contingency overlay. For a preemptive overlay, a flaw in the original dissimilar metal weld with a depth of 75% and a circumference of 360 degrees that originates from the inside of the pipe is postulated for crack growth purposes. A 75% through-wall depth flaw is the largest flaw that could remain undetected during the FSWOL preservice examination. This preservice examination will verify there is no cracking in the upper 25% of the original weld wall thickness, and thus verify that the assumption of a 75% through-wall crack is conservative. However, if any crack-like flaws are found during the preservice examination in the upper 25% of the original weld or base materials, the as-found flaw (postulated 75% through wall, plus the portion of the flaw in the upper 25%) would be used for the crack growth analysis. The size of all flaws will be projected to the end of the design life of the overlay. Crack growth, including both stress corrosion and fatigue crack growth, shall be evaluated in the materials in accordance with IWB-3640. If the flaw is at or near the boundary of two different materials, evaluation of flaw growth in both materials is required. This report will be submitted within 90 days after plant startup.

(b) Design of the FSWOL The design of the FSWOL weld is the same for preemptive overlays and for contingency overlays. The following design analysis shall be completed in accordance with IWA-4311.

1. The axial length and end slope of the weld overlay shall cover the weld Page 6 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 and the heat affected zones on each side of the weld, and shall provide for load redistribution from the item into the weld overlay and back into the item without violating applicable stress limits of ASME Section III, NB-3200. Any laminar flaws in the weld overlay shall be evaluated in the analysis to ensure that load redistribution complies with these requirements. These requirements will usually be satisfied if the weld overlay full thickness length extends axially beyond the projected flaw by at least 0.75 Rt , where R is the outer radius of the item and t is the nominal wall thickness of the item.

2. Unless specifically analyzed in accordance with 2.0(b) 1. above the end transition slope of the overlay shall not exceed 45 degrees. A slope of not more than 1:3 is recommended.

3. The thickness of the FSWOL shall be determined based on the assumption of a through-wall flaw, with a length of 360 degrees in the underlying pipe. The overlay will be applied, so that the criteria of IWB-3640 are met after the overlay is applied. The determination of the thickness shall include the deposit analysis requirements of 1.0(d).

4. 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 (e.g., support loads and clearances, nozzle loads, changes in system flexibility and weight due to the weld overlay) shall be evaluated. The effects of water backing on the repair weld shall be considered. (There are no pre-existing flaws previously accepted by analytical evaluation welds to be considered in this evaluation.) Included are:

i. A stress analysis will be performed that demonstrates that the pressure-retaining components will perform their intended design function with the FSWOL installed. The stress analysis report will include results showing that the requirements of Subarticles NB-3200 and NB-3600 of the ASME Code,Section III are satisfied.

The stress analysis will also include results showing that the requirements of IWB-3000 of the ASME Code,Section XI, are satisfied. The results will show that the postulated crack including its growth would not adversely affect the integrity of the overlaid welds. This report will be submitted within 90 days after plant startup.

ii. (Leak-before-break does not apply.)

3.0 Examination and Inspection In lieu of all other examination requirements, the examination requirements proposed herein shall be met. Nondestructive examination methods shall be in accordance with IWA-2200, except as specified herein. Nondestructive Page 7 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 examination personnel shall be qualified in accordance with IWA-2300.

Ultrasonic examination procedures and personnel shall be qualified in accordance with Appendix VIII,Section XI, as implemented through the performance demonstration initiative (PDI). (The PDI Program Status for Code Compliance and Applicability developed in June 2005 indicates that the PDI Program is in compliance with Appendix VIII, 2001 Edition of Section XI as amended and mandated by 10 CFR 50.55a, Final Rule dated October 1, 2004.)

Ultrasonic examination will be performed to the maximum extent achievable.

Pre-Overlay Examinations For welds overlaid due to leakage no examinations will be performed. In lieu of performing ultrasonic examinations when there is leakage, the flaw will be assumed to be 100% through the original wall thickness for the entire circumference.

For welds overlaid because the examination coverage is severely limited no additional examinations are practical. The flaw will be assumed to be 100%

through the original wall thickness for the entire circumference.

For welds overlaid because of unacceptable indications, the flaw size would be defined by qualified ultrasonic examinations.

Post-Overlay Examinations There are two examinations to be performed after the overlay is installed, i.e.,

the Acceptance Examination of the Overlay and the Preservice Examination.

The purpose of the Acceptance Examination is to assure a quality overlay was installed. The purpose of the Preservice Examination is to provide a baseline for future examinations and to locate and size any cracks that might have propagated into the upper 25% of the original wall thickness and evaluate accordingly. While listed below as two separate examinations the two examinations may be performed during the same time period. SNC will provide the NRC, within 14 days after the completion of the ultrasonic examination of the weld overlay installations, (1) the examination results of the weld overlays and (2) a discussion of any repairs to the overlay material and/or base metal and the reason for repair.

The NDE requirements listed below cover the area that will be affected by application of the overlay. Any SCC degradation would be in the DM weld or the adjacent heat affected zone (HAZ). Further, the original weld and adjacent base materials have received a radiographic examination (RT) prior to the initial acceptance of the existing butt weld. The proposed surface and volumetric examinations provide adequate assurance that any defects produced by welding of the overlay or by extension of pre-existing defects will be identified.

(a) Acceptance Examination of the Overlay Page 8 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1

1. The weld overlay shall have a roughness average (RA) of 225 micro-inches (250 RMS) or better and a flatness sufficient to allow for adequate examination in accordance with procedures qualified per Appendix VIII. The weld overlay shall be examined to verify acceptable configuration.

2. The weld overlay and the adjacent base material for at least 1/2 inch from each side of the weld 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 ASME Section III, NB-5300. The adjacent base metal shall satisfy the surface examination acceptance criteria for base material of the Construction Code or ASME Section III, NB-2500. If ambient temperature temperbead welding is used, the liquid penetrant 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 the third layer of the weld overlay has been completed. See Appendix 7 for hold time justification.

3. The examination volume A-B-C-D in Figure 1, which is provided in Appendix 2 to this proposed alternative, shall be ultrasonically examined to assure adequate fusion (i.e., adequate bond) with the base metal and to detect welding flaws, such as interbead lack of fusion, inclusions, or cracks. The interface C-D shown between the overlay and the weld includes the bond and the heat affected zone from the overlay. If ambient temperature temperbead welding is used, the 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 the third layer of the weld overlay has been completed. See Appendix 7 for hold time justification.

4. Planar flaws shall meet the preservice examination standards of Table IWB-3514-2. In applying the acceptance standards, wall thickness tw shall be the thickness of the weld overlay. For weld overlay examination volumes with unacceptable indications, the unacceptable indications will be removed and the volume will be re-welded. Re-examination per IWB-2420 is not required because unacceptable indications will be removed and the volume will be re-welded.

5. Laminar flaws shall meet the acceptance standards of Table IWB-3514-3 with the additional limitation that the total laminar flaw shall not exceed 10% of the weld surface area and that no linear dimension of the laminar flaw area exceeds 3.0 inches. Additional requirements are:

i. The reduction in coverage of the examination volume in Figure 1 (which is provided in Appendix 2 to this proposed alternative) due to laminar flaws shall be less than 10%. The dimensions of the uninspectable volume are dependent on the coverage achieved with the angle beam examination of the overlay.

Page 9 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 ii. Any uninspectable volume in the weld overlay beneath a laminar flaw shall be assumed to contain the largest radial planar flaw that could exist within that volume. This assumed flaw shall meet the preservice examination standards of Table IWB-3514-2. In applying the acceptance standards, wall thickness tw shall be the thickness of the weld overlay. Both axial and circumferential planar flaws shall be assumed.

iii. If the preservice acceptance criteria of Table IWB-3514-2 are not met, the assumed flaw shall be evaluated and shall meet the requirements of IWB-3640. The IWB-3640 evaluation shall be submitted to the NRC within 90 calendar days of the completion of the refueling outage. If the assumed flaw is not acceptable for continued service per IWB-3640, the lamination shall be removed or reduced in area such that the assumed flaw is acceptable per IWB-3640.

6. After completion of all welding activities, affected restraints, supports, and snubbers shall be VT-3 visually examined to verify that design tolerances are met.

(b) Preservice Inspection

1. The examination volume A-B-C-D in Figure 2, which is provided in Appendix 3 to this proposed alternative, 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 cracks that might have propagated into the upper 25% of the original wall thickness or into the weld overlay. (Additionally, the A-B dimension will be extended such that the overlay will be scanned to the extent practical).

2. The preservice examination acceptance standards of Table IWB-3514-2 shall be applied to planar indications in the weld overlay material. If the indication is found acceptable per Table IWB-3514-2 the weld overlay will be placed in service and the inservice schedule and acceptance criteria of 3(c) will be followed. In applying the acceptance standards, wall thickness, tw, shall be the thickness of the weld overlay.

Planar flaws not meeting the preservice acceptance standards of Table IWB-3514-2 shall be repaired. Re-examination per IWB-2420 is not required because unacceptable indications will be removed and the volume will be re-welded.

3. Cracks in the outer 25% of the original wall thickness shall meet the design analysis requirements as addressed in Section 2.0, Crack Growth Considerations and Design, of this proposed alternative.

(c) Inservice Inspection Page 10 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 Inservice examinations of the FSWOLs will be performed in accordance with Q-4300 and 4310 of Appendix Q to the 2004 Edition of Section XI with Addenda through 2005 with modifications. Appendix 8 shows Q-4300 and 4310 with the SNC modifications shown in italics.

4. Pressure Testing A system leakage test shall be performed in accordance with IWA-5000.

5. Documentation Use of this proposed alternative shall be documented on ASME Form NIS-2 or NIS-2A.

Basis for Use The use of weld overlay materials resistant to SCC (e.g., Alloy 52/152) that create low tensile or compressive residual stress profiles in the original weld provide increased assurance of structural integrity. The weld overlay is of sufficient thickness and length to meet the applicable stress limits from ASME Section III, NB-3200. Crack growth evaluations for SCC and fatigue of any as-found flaws or any conservatively postulated flaws will ensure that structural integrity will be maintained.

As a part of the design of the weld overlay, the weld length, surface finish, and flatness are specified in order to allow qualified ASME Section XI, Appendix VIII UT examinations, as implemented through the EPRI Performance Demonstration Initiative (PDI) Program, of the weld overlay and the required volume of the base material and original weld. The examinations specified in this proposed alternative, versus those limited examinations performed on the original dissimilar welds, will provide improved assurance of structural integrity. Further, if no flaws are found in the upper 25% of the original wall thickness by the preservice UT examinations, the postulated 75% through-wall flaw for the preemptive overlays is conservative for crack growth evaluations. If a flaw is detected in the upper 25% of the original material during the preservice examination, the actual flaw size will be used for the crack growth evaluations.

The implementation of the alternative reduces the likelihood for SCC in the identified welds and improves piping geometries to permit Appendix VIII UT 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 PWR and BWR applications. The alternative provides improved structural integrity and reduced likelihood of 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).

Duration of The proposed alternative is applicable to the 4th ISI Interval.

Page 11 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 Proposed Alternative:

Precedents: This proposed alternative is technically similar to ISI-ALT-08-01, Version 1.0, as documented in letters dated February 26, 2008 and February 28, 2008, which was developed for the Hatch Nuclear Plant Unit 1 CRD Return Line nozzle to cap overlay. This alternative was approved verbally by the NRC on February 29, 2008. The major difference between ISI-ALT-08-01 and this new proposed alternative is that ISI-ALT-08-01 was for a specific weld with a defined flaw, while this proposed alternative is more generic. Additionally, the reference to Code Case N-504-2 has been changed to N-504-3 in the proposed alternative.

This proposed alternative is also technically similar to ISI-GEN-ALT-07-03, 2.0 previously developed for Farley Nuclear Plant Unit 2 and Vogtle Electric Generating Plant Unit 1. ISI-GEN-ALT-07-03, Version 2.0 was approved by NRC Safety Evaluation dated March 10, 2008.

References:

TAC Numbers MD6307 AND MD6308 for the ISI-GEN-ALT-07-03, Version 2.0 NRC safety evaluation.

Status: Awaiting NRC approval.

Page 12 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 1 AMBIENT TEMPERATURE TEMPERBEAD WELDING 1.0 GENERAL REQUIREMENTS (a) This appendix applies to dissimilar austenitic filler metal welds between P-Nos. 1, 3, 12A, 12B, and 12C1 materials and their associated welds and welds joining P-No. 8 or 43 materials to P-No. 1, 3, 12A, 12B, and 12C materials with the following limitation:

This Appendix shall not be used to repair SA-302 Grade B material unless the material has been modified to include from 0.4% to 1.0% nickel, quenching and tempering, and application of a fine grain practice. (1P-No. 12C designation refers to specific material classifications originally identified in ASME Section III and subsequently reclassified in a later Edition of ASME Section IX).

(b) The maximum area of an individual weld overlay based on the finished surface over the ferritic base material shall be 300 square inches.

(c) Repair/replacement activities on a dissimilar-metal weld in accordance with this Appendix are limited to those along the fusion line of a nonferritic weld to ferritic base material on which 1/8- inch, 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 Appendix, provided the depth of repair in the base material does not exceed 3/8-inch.

(e) Prior to welding the area to be welded and a band around the area of at least 1-1/2 times the component thickness or 5 inches, whichever is less, shall be at least 50 degrees Fahrenheit.

(f) Welding materials shall meet the Owner's Requirements and the Construction Code and Cases specified in the Repair/Replacement 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.

2.0 WELDING QUALIFICATIONS The welding procedures and the welding operators shall be qualified in accordance with ASME Section IX and the requirements of 2.1 and 2.2 provided below.

Page 13 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 1 (Continued)

AMBIENT TEMPERATURE TEMPERBEAD WELDING 2.1 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 root width and included angle of the cavity in the test assembly shall be no greater than the minimum specified for the repair.

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

(d) The test assembly cavity depth shall be at least 1 inch. The test assembly thickness shall be at least twice the test assembly cavity depth. The test assembly shall be large enough to permit removal of the required test specimens.

The test assembly dimensions surrounding the cavity shall be at least the test assembly thickness and at least 6 inches. The qualification test plate shall be prepared in accordance with Figure 1-1.

(e) 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 (f) below, but shall be in the base metal.

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

(i) 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. When 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.

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

Page 14 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 1 (Continued)

AMBIENT TEMPERATURE TEMPERBEAD WELDING (iii) The Charpy V-notch test shall be performed in accordance with ASME Section II, Part A, 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 mm X 10 mm 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.

(g) 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 appendix, 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 NB-4335.2 of Section III, 2001 Edition with 2002 Addenda. The RTNDT 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.

2.2 Performance Qualification Welding operators shall be qualified in accordance with ASME Section IX.

3.0 WELDING PROCEDURE REQUIREMENTS The welding procedure shall include the following requirements.

(a) The weld metal shall be deposited by the automatic or machine GTAW process.

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

Page 15 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 1 (Continued)

AMBIENT TEMPERATURE TEMPERBEAD WELDING (c) The area to be welded shall be buttered with a deposit of at least three layers to achieve at least 1/8-inch overlay thickness, with the heat input for each layer controlled to within +/-10% of that used in the procedure qualification test. The heat input of the first three layers shall not exceed 45,000 J/inch 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 HAZ 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 3500F 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 (e)(1). If it is not possible to use (e)(1) then (e)(2) and (e)(3) may be used in combination.

(1) Temperature measurement (e.g., pyrometers, temperature indicating crayons, thermocouples) during welding. Trending of the interpass temperatures during installation of overlays using contact pyrometers has shown that the difference between the observed temperatures and the maximum allowable interpass temperature of 3500F is large and considerable margin exists. Based on this trending, there is reasonable assurance that the temperature of any bead will not approach the maximum allowable temperature. SNC will monitor the interpass temperature every weld pass for the first three layers. For additional layers, the frequency of measuring interpass temperature may be reduced when the temperature is at least 1000 F below the 3500 F limit and trend data supports a reduced monitoring frequency.

(2) Heat flow calculations using the variables listed below as a minimum.

(i) welding heat input (ii) initial base material temperature (iii) configuration, thickness, and mass of the item being welded (iv) thermal conductivity and diffusivity of the materials being welded (v) arc time per weld pass and delay time between each pass (vi) arc time to complete the weld (3) Measurement of the maximum interpass temperature on a test coupon that is equal to or less than the thickness of the item to be welded. The maximum heat input of the welding procedure shall be used in the welding of the test coupon.

(f) 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 metal, and shielding gas shall be suitably controlled.

Page 16 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 1 (Continued)

AMBIENT TEMPERATURE TEMPERBEAD WELDING Page 17 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 Figure 1-1: QUALIFICATION TEST PLATE APPENDIX 2 ACCEPTANCE EXAMINATION VOLUME Examination Volume A-B-C-D FIGURE 1: ACCEPTANCE EXAMINATION VOLUME Page 18 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 3 PRESERVICE EXAMINATION VOLUME 1/2 in. (min.) 1/2 in. (min.)

(Note 1)

A B t/4 D C t

Examination Volume A-B-C-D FIGURE 2: PRESERVICE EXAMINATION VOLUME Page 19 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 4 COMPARISON OF PROPOSED ALTERNATIVE WITH N-504-3 CODE CASE N-504-3 PROPOSED ALTERNATIVE Use Of Code Case Use Of Alternative Reduce a defect to a flaw of acceptable size by Reduce a defect to a flaw of acceptable size by weld overlay on austenitic SS piping. weld overlay on austenitic stainless steel, low alloy steel, carbon steel, or austenitic nickel alloy components and associated welds.

(Material covered is P-8). 1.0(a) of Appendix 1 - Materials covered are P-8 or P-43 and P-1, 12A, 12B or 12C or between P-1, 3, 12A, 12B or 12C. Also includes P-8 to P-43, P-8 to P-8 or P-43 to P-43 joined with austenitic filler materials.

Reinforcement Weld Metal Filler Metal (b) Reinforcement weld metal shall be low 1.0(b) The Alloy 52/152 weld overlay filler metal is carbon (0.035% max.) austenitic stainless steel an austenitic nickel alloy having a chromium (Cr) applied 360 deg. around the circumference of content of at least 28%. The weld overlay is the pipe, and shall be deposited in accordance applied 360 degrees around the circumference of with a qualified welding procedure specification the item, e.g., safe end to nozzle weld, and will be identified in the Repair Program. The deposited using a Welding Procedure Specification submerged arc method shall not be used for for groove welding, qualified in accordance with the weld overlay. Construction Code and Owners requirements and identified in the Repair/Replacement Plan.

Repair Of Indications Prior To Overlay Repair Of Indications Prior To Overlay (c) Prior to deposition of the weld reinforcement, 1.0(c) Prior to deposition of the FSWOL, the the surface to be repaired shall be examined by surface will be examined by the liquid penetrant the liquid penetrant method. Indications greater method. Indications larger than 1/16-inch shall be than 116in. are unacceptable and shall be removed, reduced in size, or corrected in prepared for weld reinforcement in accordance accordance with the following requirements.

with (1) or (2) below:

(c)(1) Unacceptable indication shall be 1.0(c) 1. One or more layers of weld metal shall be excavated to the extent necessary to create a applied to seal unacceptable indications in the area cavity that can be repaired using qualified to be repaired, with or without excavation. The welding procedures. (c)(2) One or more layers thickness of these layers shall not be used in of weld overlay shall be applied to seal meeting weld reinforcement design thickness unacceptable indications in the area to be requirements. Peening the unacceptable indication Page 20 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 4 COMPARISON OF PROPOSED ALTERNATIVE WITH N-504-3 CODE CASE N-504-3 PROPOSED ALTERNATIVE repaired without excavation. The thickness of prior to welding is permitted.

these layers shall not be included in meeting weld reinforcement design thickness requirements.

(d) If the preparation of (c)(1) or (2) above is 1.0(c) 2. If correction of indications is required, the required, the area where the weld reinforcement area where the weld overlay is to be deposited, is to be deposited, including any local repairs or including any local repairs or initial weld overlay initial weld overlay layers, shall be examined by layer, shall be examined by the liquid penetrant the liquid penetrant method, and shall contain no method. The area shall contain no indications indications greater than 116 in. prior to greater than 1/16-inch prior to the application of application of the structural layers of the weld the structural layers of the weld overlay.`

overlay.

Weld Reinforcement Weld Reinforcement (e) The weld reinforcement shall consist of a (This alternative does not address austenitic SS).

minimum of two weld layers having as-deposited delta ferrite content of at least 7.5 FN. The first layer of weld metal with delta ferrite content of least 7.5 FN shall constitute the first layer of the weld reinforcement design thickness.

Alternatively, first layers of at least 5 FN may be acceptable based on evaluation.

(This Code Case does not address nickel alloy 1.0(d) The austenitic nickel alloy weld overlay shall weld overlays). consist of at least two weld layers deposited using a filler material identified in 1(b). The first layer of weld metal deposited may not be credited toward the required thickness. Alternatively, for BWR applications, a 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 20% Cr.

Design of the Weld Overlay Design of the Weld Overlay Page 21 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 4 COMPARISON OF PROPOSED ALTERNATIVE WITH N-504-3 CODE CASE N-504-3 PROPOSED ALTERNATIVE (f) The design shall provide for access for the 2.0(b) The design of the FSWOL weld is the same examinations required by (i) and (j), and shall be for preemptive overlays and for contingency in accordance with (1), (2), or (3) below. overlays. The following design analysis shall be completed in accordance with IWA-4311.

(f)(1) For circumferentially oriented flaws greater than 10% of the pipe circumference, axial flaws 2.0(b) 1. The axial length and end slope of the weld equal to or greater than 1.5 in. in length, or 5 or overlay shall cover the weld and the heat affected more axial flaws of any length, the weld zones on each side of the weld, and shall provide reinforcement shall provide the necessary wall for load redistribution from the item into the weld thickness to satisfy the flaw evaluation overlay and back into the item without violating procedures of IWB-3640. The flaw shall be applicable stress limits of ASME Section III, NB-assumed to be 100% through the original pipe 3200. Any laminar flaws in the weld overlay shall wall thickness for the entire circumference of the be evaluated in the analysis to ensure that load pipe. The axial length and end slope of the redistribution complies with the these requirements.

reinforcement shall be sufficient to provide for These requirements will usually be satisfied if the load redistribution from the pipe into the weld overlay full thickness length extends axially deposited weld metal and back into the pipe beyond the projected flaw by at least 0.75 Rt ,

without violating applicable stress limits of where R is the outer radius of the item and t is the Section III for primary local and bending nominal wall thickness of the item.

stresses and secondary peak stresses. (These requirements will usually be satisfied if the 2.0(b) 2. Unless specifically analyzed in overlay full thickness length extends axially at accordance with 2(b) 1 above, the end transition least 0.75 Rt , beyond each end of the slope of the overlay shall not exceed 45 degrees.

observed flaws, where R and t are the outer A slope of not more than 1:3 is recommended.

radius and nominal wall thickness of the pipe, prior to depositing the weld overlay, and the end 2.0(b) 3. The thickness of the FSWOL shall be slope is no steeper than 45 deg.) determined based on the assumption of a through-wall flaw, with a length of 360 degrees in the underlying pipe. The overlay will be applied, so that the criteria of IWB-3640 are met after the overlay is applied. The determination of the thickness shall include the deposit analysis requirements of 1(d).

(f)(2)& (3) Provides alternate design (Not in the proposed alternative).

requirements when circumferential cracking is less than 10% or there are 4 axial flaws or less.

Evaluation of the Weld Overlay Evaluation of the Weld Overlay Page 22 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 4 COMPARISON OF PROPOSED ALTERNATIVE WITH N-504-3 CODE CASE N-504-3 PROPOSED ALTERNATIVE (g) An evaluation of the repaired weldment, as 2.0(a) Crack growth calculations will be performed well as other welds and components in the as part of a design package. Flaw characterization system affected by the weld reinforcement, shall and evaluation requirements shall be based on the be performed in accordance with (1) through (3). as-found flaw in the case of a contingency overlay.

For a preemptive overlay, a flaw in the original (g)(1) The Owner shall comply with IWA- dissimilar metal weld with a depth of 75% and a 1400(p). circumference of 360 degrees that originates from the inside of the pipe is postulated for crack growth (g)(2) The evaluation shall consider residual purposes. The size of all flaws will be projected to stresses produced by the weld overlay with the end of the design life of the overlay. Crack other applied loads on the system. The effects growth, including both stress corrosion and fatigue of water backing on the repair weld shall be crack growth, shall be evaluated in the materials in considered. The evaluation shall demonstrate accordance with IWB-3640. If the flaw is at or near that the requirements of IWB-3640 are satisfied the boundary of two different materials, evaluation for the design life of the repair, considering of flaw growth in both materials is required.

potential flaw growth due to fatigue and the mechanism believed to have caused the flaw. 2.0(b) 4. The effects of any changes in applied The flaw growth evaluation shall be performed in loads, as a result of weld shrinkage from the entire accordance with Appendix C. overlay, on other items in the piping system (e.g.,

support loads and clearances, nozzle loads, (g)(3) The evaluation of other welds and changes in system flexibility and weight due to the components in the system shall consider weld overlay) shall be evaluated. The effects of potential increases in loading, including water backing on the repair weld shall be shrinkage effects, due to all weld overlays in the considered. A stress analysis will be performed system, and shall identify and record the that demonstrates that the pressure-retaining magnitude and location of the maximum components will perform their intended design shrinkage stress developed. These welds and function with the overlay installed. The stress components shall meet the applicable stress analysis report will include results showing that the limits of the Construction Code. Shrinkage requirements of Subarticles NB-3200 and NB-3600 stresses shall be included with other applied of the ASME Code,Section III are satisfied. The loads on the system in any IWB-3640 flaw stress analysis will also include results showing evaluations required for the system. In addition, that the requirements of IWB-3000 of the ASME the effect of shrinkage from weld overlays on the Code,Section XI, are satisfied. The results will affected portion of the system restraints, show that the postulated crack including its growth supports, and snubbers shall be evaluated to would not adversely affect the integrity of the determine whether design tolerances are overlaid welds.

exceeded.

Pressure Testing Pressure Testing (h) The completed repair shall be pressure 4.0 A system leakage test shall be performed in Page 23 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 4 COMPARISON OF PROPOSED ALTERNATIVE WITH N-504-3 CODE CASE N-504-3 PROPOSED ALTERNATIVE tested in accordance with IWA-5000. If the flaw accordance with IWA-5000.

penetrated the original pressure boundary prior to welding, or if any evidence of the flaw penetrating the pressure boundary is observed during the welding operation, a system hydrostatic test shall be performed in accordance with IWA-5000. If the system pressure boundary has not been penetrated, a system leakage, inservice, or functional test shall be performed in accordance with IWA-5000.

Nondestructive Examinations (NDE) Nondestructive Examinations (NDE)

(i) Preservice examinations shall be performed 3.0 In lieu of other NDE requirements, the NDE in accordance with IWB-2200 and shall include requirements in the alternative shall be met. NDE the weld and volume identified below. methods shall be in accordance with IWA-2200, Examination procedures shall be specified in the except as specified herein. NDE personnel shall Repair Program. Liquid penetrant (PT) and be qualified in accordance with IWA-2300. UT ultrasonic (UT) examinations of the overlay shall procedures and personnel shall be qualified per be performed. Appendix VIII.

3.0(a) 1. The weld overlay shall have a roughness average (RA) of 225 micro-inches (250 RMS) or Grinding and machining of the as-welded better and a flatness sufficient to allow for overlay surface may be used to improve the adequate examination in accordance with surface finish for such examinations, when the procedures qualified per Appendix VIII.

overlay thickness is not reduced below design requirements. 3.0(a) 2. Perform a liquid penetrant examination of the overlay and 1/2-inch on either side of the overlay. Acceptance standards for the PT of the weld overlay, meet weld Construction Code criteria or NB-5300. Base material meet base material criteria or NB-2500. A 48-hour hold time after the third layer is completed is imposed when ambient temperature temperbead welding is used.

3.0(a) 3. Perform an ultrasonic (UT) examination per Figure 1, Appendix 2 to ensure adequate fusion with the base metal and to detect welding flaws.

The acceptance standards of Table IWB-3514-2 3.0(a) 4. Use the acceptance standards of Table Page 24 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 4 COMPARISON OF PROPOSED ALTERNATIVE WITH N-504-3 CODE CASE N-504-3 PROPOSED ALTERNATIVE shall apply for planar flaws. IWB-3514-2 for planar flaws. Unacceptable indications will be removed and the volume will be re-welded. A 48-hour hold time after the third layer is completed is imposed when ambient temperature temperbead welding is used.

The acceptance standards of Table IWB-3514-3 3.0(a) 5. The acceptance standards of Table IWB-shall apply for laminar flaws provided the 3514-3 shall apply for laminar flaws with the reduction in coverage of the examination volume additional limitation that the total laminar flaw shall is less than 10%. The dimensions of the not exceed 10% of the surface area and no linear uninspectable volume are dependent on the dimension of the laminar flaw area is in excess of 3 coverage achieved with the angle beam inches. Reduction in coverage is limited to 10%.

examination. Any uninspectable volume in the The dimensions of the uninspectable volume are weld overlay shall be assumed to contain the dependent on the coverage achieved with the largest radial planar flaw that could exist within angle beam examination of the overlay. Any that volume. The assumed planar flaw shall uninspectable volume in the weld overlay beneath meet the inservice examination acceptance a laminar flaw shall be assumed to contain the standards of Table IWB-3514-2. Both axial and largest radial planar flaw that could exist within that circumferential flaws shall be assumed. As an volume. The assumed flaw shall meet the alternative to the assumed planar flaw, preservice examination standards of Table IWB-radiography in accordance with the Construction 3514-2. If the preservice acceptance criteria of Code shall be used to examine the Table IWB-3514-2 are not met, the assumed flaw uninspectable volume in the weld overlay. The shall be evaluated and shall meet the requirements radiographic acceptance criteria of the of IWB-3640. If the assumed flaw is not acceptable Construction Code shall apply. Ultrasonic for continued service per IWB-3640, the lamination examinations shall verify the integrity of the shall be removed or reduced in area such that the newly applied weld reinforcement. assumed flaw is acceptable per IWB-3640.

Examinations shall also be performed to identify the original flaws in the outer 25% of the 3.0(b) 1. The examination volume A-B-C-D in underlying pipe wall as a benchmark for Figure 2, Appendix 3 shall be ultrasonically subsequent examinations of the overlay. 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 cracks that might have propagated into the upper 25% of the original wall thickness or into the weld overlay. (Additionally, the A-B dimension will be extended such that the overlay will be scanned to the extent practical).

3.0(b) 2. Meet the acceptance criteria of IWB-3514-2 for planar indications in the overlay. Wall thickness tw is the thickness of the overlay. Planar flaws not meeting the preservice acceptance Page 25 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 4 COMPARISON OF PROPOSED ALTERNATIVE WITH N-504-3 CODE CASE N-504-3 PROPOSED ALTERNATIVE standards of Table IWB-3514-2 shall be repaired.

3.0(b) 3. Cracks in the outer 25% of the original wall thickness shall meet the design analysis requirements as addressed in Section 2, Crack Growth Considerations and Design.

3.0(c) Inservice examinations of the overlays will be performed in accordance with Q-4300 and 4310 of Appendix Q to the 2004 Edition of Section XI with Addenda through 2005 with modifications.

Appendix 8 shows Q-4300 and 4310 with the SNC modifications shown in italics.

(k) VT-3 of snubbers, supports and restraints 3.0(a) 6. After completion of all welding activities, after welding affected restraints, supports, and snubbers shall be VT-3 visually examined to verify that design tolerances are met.

(l) Reference to other applicable requirements of IWA-4000 requirements would be met unless an IWA-4000 alternative provided (m) Use of case to be documented on an NIS-2 5.0 Use of case to be documented on an ASME form Form NIS-2 (or ASME Form NIS-2A).

Page 26 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 5 COMPARISON OF APPENDIX 1 OF PROPOSED ALTERNATIVE WITH N-638-1 APPENDIX 1 OF THE PROPOSED N-638-1 ALTERNATIVE Code Case N-638-1 provides rules for automatic Appendix 1 is invoked in by 1.(b) of the alternative or machine GTAW temperbead welding without for use of ambient temperature temperbead pre-heat or post weld heat treatment. The case welding as an alternative to the post weld heat covers similar and dissimilar welding for cavity treatment requirements of the Construction Code and overlay repairs. The code case permits the and Owners requirements. The appendix provides use of NDE examinations in accordance with the the ambient temperature temperbead requirements case in lieu of those in the Construction Code. applicable to dissimilar metal weld overlay repairs.

This case has a broader scope of use then NDE requirements are in lieu of the Construction Appendix 1. Code and were covered in Section 3.0 of the alternative.

1.0 General Requirements 1.0 General Requirements Scope of welds in the Reply (a) Scope of welds. Same as N-638-1 (a) Max area of finished surface of the weld (b) Surface area limitation 300 square inches over limited to 100 square inches and half of the the ferritic material. (Note: Code Case N-638-3 ferritic base metal thickness. (Note: the depth which has been approved by ASME but has not requirement is for the ferritic material. There is been issued in Supplement 9. Residual stress no need to limit either surface area or depth for analyses results show that stresses for 100 square welding on austenitic SS or nickel alloys since inches through 500 square inches surface area no post weld heat treatment is required.) overlays very similar.)

(b) (c) (d) (e) (f) (c) (d) (e) (f) (g) are the same requirements as listed for N-638-1 1.0 Welding Qualifications 2.0 Welding Qualifications The welding procedures and welding The welding procedures and welding operators shall be qualified per Section IX operators shall be qualified per Section IX and and the requirements of 2.1 and 2.2 the requirements of 2.1 and 2.2 2.1 Procedure Qualification Sections (a) (d) 2.1 Procedure Qualification Sections (a) (b) (c)

(e) (f) (g) (d) (e) same as in N-638-1 for equivalent paragraphs.

Section (h) Equivalent paragraph not in Appendix 1.

Section (i) Section (f) same as (i) from N-638-1.

Section (j) Section (g) changed the first sentence adding lateral expansion in front of value Page 27 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 5 COMPARISON OF APPENDIX 1 OF PROPOSED ALTERNATIVE WITH N-638-1 APPENDIX 1 OF THE PROPOSED N-638-1 ALTERNATIVE both at the beginning and end of the sentence. Additional provisions as follow were added:

However if the average lateral expansion value of the HAZ Charpy V-notch specimens is less than the average value of the unaffected base metal specimen and the procedure qualification meets all other requirements of this appendix, 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 NB-4335.3 of Section III, 2001 Edition with 2002 Addenda. RTndt 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. This is identical wording to N-638-2, which has been approved by ASME.

Section (b) Provisions for welding in a Not included for overlays in Appendix 1.

pressurized environment Section (c) Provisions to address Not included in Appendix 1. Thermal neutron radiation effects limitation imposed in the proposed alternative.

1.1 Performance Qualification 2.2 Performance Qualification Welding operators shall be qualified in Welding operators shall be qualified in accordance with Section IX. accordance with Section IX.

3.0 Welding Procedure Requirements 3.0 Welding Procedure Requirements (no corresponding section) (e) Section added to clarify temperature measurement requirements. This is identical wording to N-638-2, which has been approved by Page 28 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 5 COMPARISON OF APPENDIX 1 OF PROPOSED ALTERNATIVE WITH N-638-1 APPENDIX 1 OF THE PROPOSED N-638-1 ALTERNATIVE ASME.

(a) (b) (c) (a) (b) (c) same as N-638-1 except last two sentences deleted in (c) from N-638-1 since not applicable to this proposed alternative.

(d) (d) same as N-638-1 but the following added:

The interpass temperature of QW-406.3 need not be applied. This is identical wording to N-638-2, which has been approved by ASME.

(no corresponding section) (e) Section added to clarify temperature measurement requirements. This is identical wording to N-638-2, which has been approved by ASME.

(e) (f) same as (e) from N-638-1 4.0 Examination Examination and Inspection is shown in Section 3 The final weld surface and the band around the of the proposed alternative.

area defined in paragraph 1.0(d) of N-638-1 shall be examined using surface and ultrasonic methods when the completed weld has been at ambient temperature for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

5.0 Documentation Documentation is shown in Section 5 of the proposed alternative.

(no corresponding section) Pressure Testing is shown in Section 4 of the proposed alternative.

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Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 6 FIGURE 1 TYPICAL RPV NOZZLE TO SAFE-END DISSIMILAR METAL WELD OVERLAY Page 30 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 6 (Continued)

FIGURE 2 CRD RETURN NOZZLE TO CAP DISSIMILAR METAL WELD OVERLAY Page 31 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 6 (Continued)

FIGURE 3 TYPICAL INCONEL NOZZLE TO STAINLESS STEEL SAFE-END DISSIMILAR METAL WELD OVERLAY Page 32 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 6 (Continued)

FIGURE 4 TYPICAL UNIT 2 FEEDWATER INCONEL SAFE-END CONFIGURATION Page 33 of 38

Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 7 JUSTIFICATION FOR PERFORMING EXAMINATIONS 48 HOURS AFTER THE COMPLETION OF THE THIRD WELD LAYER American Society of Mechanical Engineers (ASME) Code,Section XI, Code Case N-638-1 requires (when ambient temperbead welding is used over ferritic materials) that surface and ultrasonic examinations be performed when the completed weld has been at ambient temperature for least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. This delay was provided to allow sufficient time for hydrogen cracking to occur (if it is to occur) in the heat affected zone (HAZ) of ferritic materials prior to performing examinations, to ensure detection by non-destructive examinations (NDE).

However, based on research and industry experience, EPRI has provided a technical basis for starting the 48-hour hold after completion of the third temperbead weld layer rather than waiting for the weld overlay to cool to ambient temperature. Weld layers beyond the third layer are not designed to provide tempering to the ferritic HAZ during ambient temperature temperbead welding. EPRI has documented their technical basis in Technical Update report 1013558, Repair and Replacement Applications Center: Temperbead Welding Applications 48-Hour Hold Requirements for Ambient Temperature Temperbead Welding (ADAMS Accession No. ML070670060). The technical data provided by EPRI in their report is based on testing performed on SA-508, Class 2 low-alloy steels, which is the nozzle material. After evaluating all of the issues relevant to hydrogen cracking such as microstructure of susceptible materials, availability of hydrogen, applied stresses, temperature, and diffusivity and solubility of hydrogen in steels, EPRI concluded that: ...[t]here appears to be no technical basis for waiting the 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after cooling to ambient temperature before beginning the NDE of the completed weld.

There should be no hydrogen present, and even if it were present, the temperbead welded component should be very tolerant of the moisture... EPRI also notes that over 20 weld overlays and 100 repairs have been performed using temperbead techniques on low alloy steel components over the last 20 years. During this time, there has never been an indication of hydrogen cracking by the non-destructive examinations performed after the 48-hour hold or by subsequent ISI examinations.

In addition, the ASME database, C&S Connect, for Code Case N-638-4 contains background material consisting of a Technical Basis Paper to support the 48-hour hold time alternative. The Technical Basis Paper (ADAMS Accession No. ML070790679) points out that the introduction of hydrogen to the [ferritic] HAZ is limited to the first weld layer since this is the only weld layer that makes contact with the [ferritic] base material. While the potential for the introduction of hydrogen to the [ferritic] HAZ is negligible during subsequent weld layers, these layers provide a heat source that accelerates the dissipation of hydrogen from the [ferritic] HAZ in non-water backed applications. The Technical Basis Paper concludes that there is sufficient delay time to facilitate the detection of potential hydrogen cracking when NDE is performed 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 weld layer.

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Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 7 JUSTIFICATION FOR PERFORMING EXAMINATIONS 48 HOURS AFTER THE COMPLETION OF THE THIRD WELD LAYER (Continued)

Furthermore, the solubility of hydrogen in austenitic materials such as Alloy 52M is much higher than that of ferritic materials while the diffusivity of hydrogen in austenitic materials is lower than that of ferritic materials. As a result, hydrogen in the ferritic HAZ tends to diffuse into the austenitic weld metal, which has a much higher solubility for hydrogen. This diffusion process is enhanced by heat supplied in subsequent weld layers.

Based on this information, SNC concludes that performing NDE 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the third weld layer is installed will provide an acceptable level of quality and safety. As a precedent see the April 6, 2007, safety evaluation for Arkansas Nuclear One, Unit 1 (TAC NO. MD4019) and the December 19, 2007 safety evaluation for Farley Nuclear Plant Units 1 and 2 (TAC NOS.

MD6304 and MD6305).

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Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 8 Q-4300 EXAMINATION REQUIREMENTS Q-4300 Inservice Examination Requirements (a) The weld overlay examination volume in Fig. Q-4300-1 shall be added to the inspection plan and shall be ultrasonically examined during the first or second refueling outage following application.

(b) The weld overlay examination volume in Fig. Q-4300-1 shall be ultrasonically examined to determine if any new or existing cracks have propagated into the upper 25% of the pipe base material or into the overlay. The angle beam shall be directed perpendicular and parallel to the pipe axis, with scanning performed in four directions.

Modified Q-4300 Inservice Flaw Evaluation Requirements (a) Flaws characterized as SCC in the Alloy 52/152 weld overlay are unacceptable and the use of IWB-3514-2 and IWB-3640 for SCC evaluation in the Class 1 overlay material is prohibited.

(b) For non-SCC flaws in the Alloy 52/152 overlay, Table IWB-3514-2 must be used to evaluate recordable indications prior to the use of the acceptance criteria of IWB-3600. If the requirements of Table IWB-3514-2 cannot be satisfied, the acceptance criteria of IWB-3600 shall be satisfied. For unacceptable indications, the weld overlay (or the portion of the weld overlay containing the unacceptable indication) shall be removed and corrected by a repair/replacement activity in accordance with IWA-4000.

(c) If examinations reveal crack growth or new cracking in the upper 25% of the original weld or base materials, the as-found flaw (postulated 75% through wall, plus the portion of the flaw in the upper 25%) will be used to re-evaluate the crack growth analysis. The size of all flaws will be projected to the end of the design life of the overlay. Crack growth, including both stress corrosion and fatigue crack growth, shall be evaluated in the materials in accordance with IWB-3640. If the flaw is at or near the boundary of two different materials, evaluation of flaw growth in both materials is required. For unacceptable indications, the weld overlay shall be removed, including the original defective piping weldment, and corrected by a repair/replacement activity in accordance with IWA-4000.

Modified Q-4300 Re-examination Requirements (a) Weld overlay examination volumes that show no indication of crack growth or new cracking shall be placed into a population to be examined on a sampling basis. Twenty-five percent of this population shall be examined once every ten years.

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Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 8 Q-4300 EXAMINATION REQUIREMENTS (Continued)

(b) If inservice examinations reveal acceptable crack growth or new cracking in the upper 25% of the original weld or base materials, the weld overlay examination volume shall be reexamined during the first or second refueling outage following discovery of the growth or new cracking. Weld overlay examination volumes that show no additional indication of crack growth or new cracking shall be placed into a population to be examined on a sample basis. Twenty-five percent of this population shall be examined once every ten years.

(c) If inservice examinations reveal acceptable non-SCC flaws in the overlay material, the weld overlay examination volume shall be reexamined during the first or second refueling outage following discovery of the growth or new cracking. Weld overlay examination volumes that show no additional indication of crack growth or new cracking shall be placed into a population to be examined on a sample basis. Twenty-five percent of this population shall be examined once every ten years.

Q-4310 Additional Examinations If inservice examinations reveal an unacceptable indication, crack growth into the weld overlay design thickness, or axial crack growth beyond the specified examination volumes, additional weld overlays, equal to the number scheduled for the current inspection period, shall be examined prior to return to service. If additional unacceptable indications are found in the second sample, a total of 50% of the total population of weld overlays shall be examined prior to operation. If additional unacceptable indications are found, the entire remaining population of weld overlays shall be examined prior to return to service.

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Enclosure Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

Application of Dissimilar Weld Full-Structural Weld Overlays Alternative ISI ALT-08-02 Version 1 APPENDIX 8 Q-4300 EXAMINATION REQUIREMENTS (Continued)

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