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Relief Request Number RR 5-12, Proposed Alternative to ASME Section XI Code for Full Structural Weld Overlays of Primary Coolant System Hot Leg, Cold Leg, and Pressurizer Nozzle Dissimilar Metal Welds
	ML25232A195
Person / Time
Site:	Palisades
Issue date:	08/20/2025
From:	Fleming J; Holtec Palisades
To:	; Office of Nuclear Reactor Regulation, Document Control Desk
References
	PNP 2025-059
	Download: ML25232A195 (1)
	v • d • e

HOLTEC PALISADES PNP 2025-059 August20,2025 ATTN: Document Control Desk U.S. Nuclear Regulatory commission Washington, DC 20555-0001 Palisades Nuclear Plant NRC Docket 50-255 27780 Blue Star Highway, Covert, MI 49043 10 CFR50.55a Renewed Facility Operating License No. DPR-20

Subject:

Relief Request Number RR 5-12, Proposed Alternative to ASME Section XI Code for Full Structural Weld Overlays of Primary Coolant System Hot Leg, Cold Leg, and Pressurizer Nozzle Dissimilar Metal Welds Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a, Codes and standards, paragraph (z)(1 ), Holtec1 hereby requests Nuclear Regulatory Commission (NRC) approval of the attached relief request for the Palisades Nuclear Plant (PNP) lnservice Inspection (ISi)

Program, fifth ten-year interval.

PNP ceased operation in Spring 2022. Holtec is performing modifications to PNP to support the restart of plant operations. The PNP Primary Coolant System (PCS) Hot Leg, Cold Leg, and Pressurizer Nozzle Dissimilar Metal Welds (DMWs) containing Alloys 82 and 182 weld materials have experienced Primary Water Stress Corrosion Cracking (PWSCC) in components operating at pressurized water reactor temperatures. Holtec is applying Full Structural Weld Overlays (FSWOLs) on the DMWs using PWSCC-resistant nickel Alloy 52M (ERNiCrFe-7A) and Alloy 52MSS (ERNiCrFe-13) filler material. This approach provides an alternative to inspection alone to ensure the structural integrity of these locations.

Nuclear Regulatory Commission approved criteria currently exist for a licensee to apply a FSWOL to an Alloy 82/182 DMW. The edition and addenda of ASME Code Section XI applica-ble to PNP does not contain requirements for FSWOLs for DMWs. However, DMW FSWOLs have been applied to other PCS nozzle DMWs in the PWR industry using alternative require-ments. This request proposes to use the methodology of ASME Code Case N-740-2 for applica-tion of a FSWOL to the DMWs identified in Section 1.0 of Attachment 1. Since ASME Code Case N-740-2 has not been approved by the NRC in the latest revision of Regulatory Guide (RG) 1.147, an alternative is required.

1 Holtec Palisades, LLC ("Holtec Palisades") is the licensed owner of PNP. Pursuant to the license transfer amendment received in connection with the PNP restart (Reference 1 ), licensed operating authority has transferred from Holtec Decommissioning International, LLC ("HDI") to Palisades Energy, LLC ("Palisades Energy").

PNP 2025-059 Page 2 of 3 This request describes the alternative requirements Holtec proposes to use for the design and installation of FSWOLs on the Cold Leg, Hot Leg, and Pressurizer DMWs at PNP.

The provisions of this relief are applicable to the fifth ten-year lnservice Inspection interval at PNP, which commenced on December 13, 2015, and is currently scheduled to end on December 12, 2025, as identified in the Fifth Interval lnservice Inspection Plan, submitted to the NRC on December 09, 2015, (Reference 2). While this relief request identifies some of the same code cases as previous relief requests, updated versions of the applicable code cases, as approved by the NRC, may be used and are referenced in this submittal.

Attachments 1 through 6 to this letter provides the supporting information for this relief request.

Holtec is requesting NRC approval by October 3, 2025.

This letter contains no new regulatory commitments.

Please refer any questions regarding this submittal to Frank Sienczak, PNP Regulatory Assurance Manager, at (269) 764-2263.

Sincerely, Jean A.

Fleming Digitally signed by Jean A. Fleming DN: cn=Jean A. Fleming, o=Holtec Decommissioning International, LLC, ou=Regulatory and Environmental Affairs, email=J.Fleming@Holtec.com Date: 2025.08.20 13:45:02 -04'00' Jean A. Fleming Vice President of Licensing and Regulatory Affairs Holtec International Attachments:

1. Relief Request RR-5-12, Proposed Alternative Requirements for the Modification of Primary Coolant System Hot Leg, Cold Leg, and Pressurizer Nozzle Dissimilar Metal Welds, lnservice Inspection Program, Fifth Ten-Year Interval

2. Requirements for Hot Leg Surge, Hot Leg Shutdown Cooling, Cold Leg Safety Injection, Pressurizer Surge and Pressurizer Relief Dissimilar Metal Weld Overlays

3. Ambient Temperature Temper Bead Welding

4. Review of ASME Code Case N-740-2 Against the Proposed Alternative Weld Overlay

5. Proposed Changes to ASME Code Section XI, Appendix VIII for Compatibility with the Performance Demonstration Initiative (POI) Program

6. Technical Basis for Inclusion of 28% Chromium Nickel-Based Filler Metals in ASME Code Case N-770-X

PNP 2025-059 Page 3 of 3

References:

1. U.S. Nuclear Regulatory Commission (NRC) letter to Holtec, Palisades Nuclear Plant-Order Approving Direct Transfer of Renewed Facility Operating License and Independent Spent Fuel Storage Installation General License and Issuance of Conforming Amendment 275 (EP/O L-2023-LLM-0005), dated July 24, 2025 (ADAMS Accession No. ML25167A243)

2. Entergy Nuclear Operations Inc. letter to NRC, "lnservice Inspection Master Program Fifth 10-year Interval", dated December 09, 2015 (ADAMS Accession No. ML15343A090) cc:

NRC Senior Resident Inspector, PNP NRC Project Manager, PNP NRC Region Ill Administrator

PNP 2025-059 Page 1 of 20 ATTACHMENT 1 PALISADES NUCLEAR PLANT Relief Request Number RR 5-12 Proposed Alternative Requirements for the Modification of Primary Coolant System Hot Leg, Cold Leg, and Pressurizer Nozzle Dissimilar Metal Welds in Accordance with 10 CFR 50.55a(z)(1)

PNP 2025-059 Page 2 of 20 1.0 ASME CODE COMPONENT AFFECTED Component:

!Primary Coolant System (PCS) Hot Leg/ Cold Leg Piping and Pressurizer

==

Description:==

!Alternative Requirements for the Modification of Primary Coolant System Hot Leg iand Cold Leg Nozzles and Pressurizer Nozzle Dissimilar Metal Welds l

1Code Class:

!Class 1 Examination f'SME Code Case N-770-7, Inspection Items A-1, A-2, and B-1

-Category:

I Identification:

!See Table 1-1 Reference

VEN-M1-D, Sheet 108, Rev. 10, Nozzle Details, (M0001D-0108, Rev. 10)

Drawings:

VEN-M 1-D, Sheet 109, Rev. 10, Nozzle Details, (M0001D-0109, Rev. 10)

VEN-M1-LA, Sheet 985, Rev. 13, Nozzle Details for Consumers Power Pressurizer, (M0001 LA-0985, Rev. 13)

VEN-M 1-LA, Sheet 986, Rev. 10, Nozzle Details Pressurizer, (M0001 LA-0986, Rev. 10)

02-1230804-E-00, Palisades PORV Nozzle Safe End/Spool Piece Replacement Materials:

PCS Nozzles - SA-508, Class 1 (P-No. 1)

Pressurizer Nozzles - A508-64, Class 2 (P-No. 3)

Alloy 600 Safe Ends - SB-166 UNS N06600 (P-No. 43)

PCS Branch Piping - Type 316 Stainless Steel (P-No. 8)

Cold Leg Safety Injection Check Valve Bodies 8SMO Cast Stainless Steel (P-No. 8)

Alloy 82/182 Dissimilar Metal Welds (DMW)- ENiCrFe-3, SFA-5.14 /

ENiCrFe-3, SFA-5.11 (both F-No. 43)

Replacement PORV Nozzle Safe End - SA-479, Type 316 (P-No. 8)

PORV Nozzle Alloy 52 Weld - ERNiCrFe-7, SFA-5.14 (F-No. 43)

PORV Nozzle Alloy 182 Weld Remnant - ENiCrFe-3, SFA-5.11 (F-No. 43)

PNP 2025-059 Page 3 of 20 Component PCS Hot Leg PCS Cold Leg Pressurizer Nozzle Description NPS 12 Sch 140 Pressure Surge (Loop 1)

NPS 12 Sch 140 Shutdown Cooling (Loop 2)

NPS 12 Sch 140 Safety Injection (Loop 1A)

NPS 12 Sch 140 Safety Injection (Loop 1 B)

NPS 12 Sch 140 Safety Injection (Loop 2A)

NPS 12 Sch 140 Safety Injection (Loop 2B)

NPS 12 Sch 140 Pressure Surge NPS 4 Sch 120 Power Operated Relief Valve (PORV)

Table 1-1 Weld Identification Weld Number Weld Description Examination Category PCS-12-PSL-1 H1-8 Nozzle to Safe End A-2 PCS-12-PSL-1 H1-7 Safe End to Piping A-2 PCS-12-SDC-2H 1-1 Nozzle to Safe End A-2 PCS-12-SDC-2H1-2 Safe End to Piping A-2 PCS-12-SIS-1A 1-12 Nozzle to Safe End B-1 PCS-12-SIS-1A1-11 Safe End to Valve B-1 PCS-12-SIS-1 B1-16 Nozzle to Safe End B-1 PCS-12-SIS-1 B1-15 Safe End to Valve B-1 PCS-12-SIS-2A 1-15 Nozzle to Safe End B-1 PCS-12-SIS-2A 1-14 Safe End to Valve B-1 PCS-12-SIS-2B1-15 Nozzle to Safe End B-1 PCS-12-SIS-2B1-14 Safe End to Valve B-1 PCS-12-PSL-1 H1-1 Nozzle to Safe End A-1 PCS-12-PSL-1 H1-2 Safe End to Piping A-1 Nozzle to PCS-4-PRS-1 P 1-1 Replacement Safe A-1 End (See Note)

Note - The original safe end and adjacent pipe for the PORV nozzle were replaced with a stainless steel safe end in 1995.

PNP 2025-059 Page 4 of 20 2.0 APPLICABLE CODE EDITION The current edition for the lnservice Inspection (ISi) interval for Palisades Nuclear Plant (PNP) is the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (B&PVC),Section XI, 2007 Edition with Addenda through 2008 (Reference 1 ). PNP is in the fifth inspection interval with a scheduled end date of December 12, 2025.

The Construction Code for the PNP PCS piping is ASA B31.1, 1955 Edition and ASME B&PVC Section 111, 1965 Edition including Addenda through Winter 1966.

The Construction Code for the PNP Pressurizer is ASME B&PVC Section Ill, 1965 Edition including Addenda through Winter 1966.

ASME B&PVC Code Case N-770-7 (Reference 6) as conditioned by 10 CFR 50.55a.

ASME B&PVC Section Ill, Subsection NB, 2019 Edition 3.0 APPLICABLE CODE REQUIREMENTS The applicable requirements of the following ASME Code and Code Cases from which relief is requested are as follows:

ASME Code,Section XI, 2007 Edition through 2008 Addenda 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)."

IWA-4411(b) of ASME Code Section XI states: "Revised Owner's Requirements may be used, provided they are reconciled in accordance with IWA-4222."

IWA-4411 (e) of ASME Code Section XI states: "The requirements of IWA-4600(b) may be used when welding is to be performed without the post weld heat treatment required by the Construction Code."

ASME Code Section XI, Appendix VIII, Supplement 11 provides qualification requirements for UT examination of FSWOLs.

PNP 2025-059 Page 5 of 20 ASME Code Case N-770-7 Paragraph -1210(b) lists ERNiCrFe-7, ENiCrFe-7, and ERNiCrFe-7A as weld filler materials for mitigating piping nozzle butt welds fabricated with Alloy 82/182 material.

4.0 REASON FOR REQUEST Dissimilar metal welds (DMWs) containing Alloys 82 and 182 weld material have experienced primary water stress corrosion cracking (PWSCC) in components operating at pressurized water reactor temperatures (References 9, 10, and 11 ).

Holtec International (Holtec) is applying full structural weld overlays (FSWOLs) on the DMWs identified in Section 1.0 using PWSCC-resistant nickel Alloy 52M (ERNiCrFe-7 A) and Alloy 52MSS (ERNiCrFe-13) filler material. This approach provides an alternative to inspection alone to ensure the structural integrity of these locations.

Currently, there are no Nuclear Regulatory Commission (NRC) approved criteria for a licensee to apply a FSWOL to an Alloy 82/182 DMW. The edition and addenda of ASME Code Section XI applicable to PNP does not contain requirements for FSWOLs for DMWs. However, DMW FSWOLs have been applied to other PCS nozzle DMWs in the PWR industry using alternative requirements. This request proposes to use the methodology of ASME Code Case N-740-2 (Reference 5) for application of a FSWOL to the DMWs identified in Section 1.0. Since ASME Code Case N-740-2 has not been approved by the NRC in the latest revision of Regulatory Guide (RG) 1.147 (Reference 7), an alternative is required.

This request describes the alternative requirements Holtec proposes to use for the design and installation of FSWOLs on the Cold Leg, Hot Leg, and Pressurizer DMWs at PNP identified in Section 1.0.

PNP 2025-059 Page 6 of 20 5.0 PROPOSED ALTERNATIVE AND BASIS FOR USE Pursuant to 10 CFR 50.55a(z)(1 ), Holtec proposes an alternative to the ASME Code requirements stated in Section 3.0. The proposed alternative is provided in Attachments 2 and 3 and involves the installation of Alloy 52M/Alloy 52MSS FSWOLs that structurally replace the existing DMWs identified in Section 1.0.

The design, analyses, fabrication, acceptance examination, and pressure testing of the FSWOLs will be performed in accordance with ASME Code Case N-740-2 as specified in. ASME Code Case N-740-2 has been approved by the ASME Code Committee to allow FSWOLs on nickel alloy DMWs. However, ASME Code Case N-740-2 has not been accepted by the NRC in RG 1.147, Revision 21. ASME Code Case N-740-2 provides the basis and requirements for the weld overlay techniques. Attachment 4 provides a review of the applicable ASME Code Case N-740-2 requirements used for the proposed alternative and provides justifications and exceptions to those requirements.

The justifications in Attachment 4 include comparisons to Nonmandatory Appendix Q of the 2007 Edition with Addenda through 2008 of ASME Code Section XI, which has been approved by the NRC.

Appendix VIII, Supplement 11 of the 2007 Edition with Addenda through 2008 of ASME Code Section XI specifies requirements for performance demonstration of ultrasonic (UT) examination procedures, equipment, and personnel used to detect and size flaws in FSWOLs of wrought austenitic piping welds. Relief is requested to allow use of the Performance Demonstration Initiative (POI) Program implementation of Appendix VIII for qualification of UT examinations used to detect and size flaws in the FSWOLs of this request for alternative. The proposed modifications to Appendix VIII, Supplement 11 for use on FSWOLs are shown in Attachment 5.

The preservice and inservice inspections of the FSWOLs will be performed in accordance with the augmented inspection requirements of ASME Code Case N-770-7 as prescribed in 10 CFR 50.55a(g)(6)(ii)(F). Paragraph -1210(b) of ASME Code Case N-770-7 does not list Alloy 52MSS as one of the mitigative weld filler materials for piping nozzle butt welds fabricated with Alloy 82/182 material. Holtec requests approval for using ASME Code Case N-770-7 examinations on FSWOLs consisting of Alloy 52MSS weld metal.

Sections 5.1 and 5.2 below provide additional discussion on the FSWOL designs, analyses, verifications, and post-overlay NDE for the proposed alternative.

Ambient temperature temper bead welding will be performed in accordance with the alternative specified in Attachment 3 based on Mandatory Appendix I in ASME Code Case N-740-2. Section 5.3 below discusses the suitability of the proposed ambient temperature temper bead welding technique.

PNP 2025-059 Page 7 of 20 The proposed alternative provides an acceptable methodology for mitigating PWSCC.

The use of weld overlay filler metals that are resistant to PWSCC (e.g., Alloy 52M/52MSS), weld overlay procedures that create compressive residual stress profiles within the original weld, and post-overlay acceptance, preservice and inservice inspection requirements provide assurance that structural integrity will be maintained for the remaining service life of the weld. Crack growth evaluations for PWSCC and fatigue of a bounding postulated flaw have demonstrated that structural integrity of the components, with the FSWOLs in place, will be maintained for the remaining service life of the components.

Therefore, Holtec requests approval of this alternative on the basis that the proposed requirements will provide an acceptable level of quality and safety.

5.1 Weld Overlay Designs and Analyses Weld Overlay Designs Holtec is applying an FSWOL at each of the eight (8) nozzle locations listed in Table 1-1 above. The FSWOLs will extend around the full circumference of the DMWs. The length, thickness, and geometry of each FSWOL are sufficient to meet the structural requirements determined according to the guidance provided in ASME Code Case N-7 40-2. The length of each FSWOL is sufficient to allow 100% coverage for the preservice and inservice examinations required in ASME Code Case N-770-7.

Figure 1 shows a schematic representation of the FSWOL design typical for the Hot Leg Surge, Hot Leg Shutdown Cooling, and Pressurizer Surge nozzle locations. Figure 2 shows a schematic representation of the FSWOL design typical for the four Cold Leg Safety Injection nozzle locations. Figure 3 shows a schematic representation of the FSWOL design for the Pressurizer PORV nozzle location.

Each of the seven (7) nominal pipe size (NPS) 12 schedule (Sch) 140 nozzles will have a single FSWOL that completely covers the two DMWs at each location, the Alloy 600 safe end, the outboard portion of the ferritic steel nozzle, and the inboard portion of the adjacent stainless steel piping or valve, as applicable, with Alloy 52M/52MSS material.

The FSWOL for the PORV nozzle will completely cover the replacement Alloy 52 butt weld (including the original Alloy 182 weld remnant), the outboard portion of the ferritic steel nozzle, and the inboard portion of the replacement stainless steel safe end with Alloy 52M material. The FSWOLs will mitigate the PWSCC susceptible material as well as provide the geometry required to perform the final volumetric examinations and obtain the required examination volume coverage.

PNP 2025-059 Page 8 of 20 Analyses Nozzle-specific sizing calculations, residual stress analyses, crack growth analyses, and ASME Code, Section Ill stress and fatigue analyses have been performed and are summarized in Reference 8. A piping system impact analysis, which is also summarized in Reference 8, has been performed to evaluate the permanent impacts of the installation of the FSWOLs on the PCS piping and attached PCS branch piping. The analyses demonstrate that the FSWOL modifications to the DMWs meet the requirements of Section Ill, Division 1, and Section XI, Division 1, Nonmandatory Appendix C, and will have no significant impact on the PCS piping, PCS branch lines, any pipe supports on the PCS branch lines, or on the PCS Pressurizer upon verification of the assumed axial weld shrinkage dimensions.

5.2 Post-Overlay Nondestructive Examination (NOE)

Suitability of Proposed Post-Overlay UT Examinations As part of the design of the FSWOL, the FSWOL length, surface finish, and flatness are specified to allow for post-installation, qualified ASME Code Section XI, Appendix VIII UT examinations, as implemented through the Electric Power Research Institute (EPRI) POI Program. These examinations include the FSWOL and the required volume of the base material and original weld underneath the FSWOL. The examinations specified in this proposed alternative provide adequate assurance of structural integrity for the following reasons:

The UT examinations that will be performed with the proposed alternative are in accordance with ASME Code Section XI, Appendix VIII, Supplement 11, as implemented through the POI Program. These examinations are considered more sensitive for detection of defects, either from fabrication or service induced, than ASME Code, Section Ill radiography or UT methods. Further, construction flaws are included in the POI qualification sample sets for evaluating procedures and personnel.

Section XI has specific acceptance criteria and evaluation methodology to be used with the results from these more sensitive UT examinations. The criteria 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 planar flaws per Table IWB-3514-1 and allowable laminar flaws per Table IWB-3514-3.

PNP 2025-059 Page 9 of 20 A laminar flaw is defined in 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, weld overlays, and base materials. The standard imposed for evaluating laminar flaws in Section XI is more restrictive than the Section Ill standard for evaluating laminations. The laminar flaw standards are contained in Table IWB-3514-3 of Section XI and are supplemented in Attachment 2. These criteria require that the sum of laminar flaw lengths in any direction must be less than 10% of the overlay length, with a total area of laminar flaws equal to or less than that in Table IWB-3514-3. For weld overlay areas where examination is precluded by the presence of the flaw, the areas must be postulated to be cracked.

Any planar flaws found in the FSWOL during either the weld overlay acceptance or preservice examinations are required to meet the preservice standards of Section XI, Table IWB-3514-1. In applying the planar flaw standards, the thickness of the component must be defined as the thickness of the FSWOL, and the issue of any flaws masked from examination must also be addressed as a part of the proposed alternative.

Section Ill uses NOE procedures and techniques with flaw detection capabilities that are within the practical limits of workmanship standards for welds. These standards are mostly 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 Section Ill acceptance standards are written for a range of fabrication flaws including lack of fusion, 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 Section 111 acceptance standards do not have a significant effect on the structural integrity of the component. The proposed alternative in Attachment 2 was written to specifically address weld overlays. This alternative adequately examines the weld overlay and provides appropriate examinations and acceptance criteria as discussed herein.

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. The criteria are consistent with criteria previously approved by the NRC for weld overlay installations.

PNP 2025-059 Page 10 of 20 Use of ASME Code Case N-770-7 Preservice/lnservice Examinations on FSWOLs consisting of ERNiCrFe-13 (Alloy 52MSS) Weld Metal The preservice and inservice inspections of the FSWOLs will be performed in accordance with the augmented inspection requirements of ASME Code Case N-770-7 as prescribed in 10 CFR 50.55a(g)(6)(ii)(F). Paragraph -121 0(b) of ASME Code Case N-770-7 does not list Alloy 52MSS as one of the mitigative weld filler materials for piping nozzle butt welds fabricated with Alloy 82/182 material.

Many years of operating experience show the exceptional performance of all Alloy 52 type filler materials that utilize a chemistry consisting of greater than 28% Chromium for resisting Stress Corrosion Cracking. Therefore, it is appropriate to include other 28%

Chromium bearing nickel-based filler materials in the list of Alloy 52 materials in ASME Code Case N-770-7. Attachment 6 provides a technical basis for including other Alloy 52 variants that contain at least 28% Chromium as an acceptable filler material in N-770-7.

Therefore, Holtec requests approval for using ASME Code Case N-770-7 examinations on FSWOLs consisting of Alloy 52MSS weld metal.

5.3 Suitability of Proposed Ambient Temperature Temper Bead Technique The FSWOLs addressed by this alternative will be performed using ambient temperature temper bead welding in lieu of post weld heat treatment (PWHT), in accordance with, and the provisions of this Request for Alternative. Research by 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-111050 (Reference 12). According to the EPRI report, repair welds performed with an ambient temperature temper bead procedure utilizing the machine GTAW 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 all demonstrated the effectiveness of this process.

The effects of the ambient temperature temper bead welding process, qualified and performed in accordance with Attachment 3, 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.

PNP 2025-059 Page 11 of 20 Mechanical Properties of Repair Welds The principal reason 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 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 GTAW process, effective tempering of the weld heat affected zone (HAZ) is possible without the application of preheat. According to Section 2-1 of EPRI Report GC-111050, "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 (i.e., tempering) is achieved. The resulting microstructure is very tough and ductile."

The ASME Code,Section XI, IWA-4600 temper bead process also includes a post-weld soak requirement that is performed at 300 degrees Fahrenheit (°F) for 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months (i.e., P-No.

3 base materials). This post-weld soak assists diffusion of any remaining hydrogen from the repair weld. As such, the post-weld soak is a hydrogen bake-out and not a post-weld heat treatment as defined by the ASME Code. At 300°F, the post-weld soak 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 using the GTAW temper bead process, no post-weld soak is needed for this application.

The alternative in Attachment 3 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 are equivalent to or superior to those of the surrounding base material.

PNP 2025-059 Page 12 of 20 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 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 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months of welding.

The machine GTAW process is inherently free of hydrogen. Unlike the shielded metal arc welding (SMAW) process, GTAW filler metals do not rely on flux coverings that may be susceptible to moisture absorption from the environment. Conversely, the GTAW 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 mixing 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 machine GTAW temper bead process. Therefore, the potential for hydrogen-induced cracking is greatly reduced by using the machine GTAW process.

Cold Restraint Cracking Cold cracking generally occurs during cooling at temperatures approaching ambient temperature. As stress builds 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 sufficient heat inventory, to produce the desired tempering for high toughness.

Because the machine GTAW 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 must be appropriately tempered to exhibit toughness sufficient to resist cold cracking.

PNP 2025-059 Page 13 of 20 Weld Procedure Qualification Simulated Post-Weld Heat Treatment The requirement for simulated PWHT in paragraph A3.2.1 (a) of Attachment 3 is in accordance with paragraph 2.1(a) of ASME Code Case N-638-11 (Reference 4), which states that simulated PWHT of the qualification test plate, if used, shall not exceed the time or temperature already applied to the base material to be welded. ASME Code Case N-638-11 has been unconditionally approved by the NRC in RG 1.14 7, Revision

21.

The welding procedures used for ambient temperature temper bead welding on the NPS 12 Sch 140 nozzles have been qualified in accordance with Paragraph A3.2.1(a) and are therefore compliant with paragraph 2.1 (a) of ASME Code Case N-638-11.

The PORV nozzle weld procedure was qualified in accordance with ASME Code Case N-638-4 (Reference 3), and the qualification test plate that was used underwent 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months of simulated PWHT at 1150°F prior to welding. The Construction Code for the PORV nozzle (Reference 2) requires a minimum of 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months of PWHT at a minimum holding temperature of 1100°F, however the PWHT records were not available at the time of this submittal. Therefore, the simulated PWHT for the PORV nozzle weld procedure qualification may or may not exceed the actual time and temperature applied to the base material to be welded.

If the simulated PWHT time and temperature are equal to or greater than the time and temperature applied to the PORV nozzle base material, then the weld procedure qualification complies with ASME Code Case N-638-4, paragraph 2.1 (a), which requires simulated PWHT time and temperature on the temper bead qualification test plate to be equivalent to or exceed the total aggregate time applied to the component to be welded.

ASME Code Case N-638-4 does not specify a maximum limit on the simulated PWHT time or temperature. Paragraph A3.2 of Attachment 3, which is in accordance with paragraph 2(b) of ASME Code Case N-638-11, permits use of welding procedures qualified in accordance with previous revisions of Code Case N-638. Therefore, this scenario would be compliant with paragraph 2(b) of ASME Code Case N-638-11.

PNP 2025-059 Page 14 of 20 If the simulated PWHT time and temperature are less than the actual PWHT time and temperature applied to the PORV nozzle base material, then the weld procedure qualification does not comply with ASME Code Case N-638-4, paragraph 2.1 (a).

However, the simulated PWHT requirement of Revision 4 of Code Case N-638 has been recognized by the ASME Code Committee as non-conservative, as documented in EPRI Report 1025169, Section 3.0 (Reference 13), and was updated in Revision 7. Code Case N-638-11, paragraph 2.1 (a) now states that simulated PWHT of the "test assembly is neither required nor prohibited. However, if used, the simulated PWHT shall not exceed the time or temperature already applied to the base material to be welded."

Therefore, if the simulated PWHT time and temperature do not exceed the time and temperature applied to the PORV nozzle base material, the weld procedure would be compliant with paragraph 2.1(a) of ASME Code Case N-638-11. The NRC has previously approved the application of the updated simulated PWHT requirements of paragraph 2.1 (a) of ASME Code Case N-638 (Revision 7 and later) when using temper bead welding procedures qualified in accordance with Revision 4 of the Code Case (see References 14 and 15).

In summary, the simulated PWHT used for the weld procedure qualification may or may not be greater the PWHT applied to the base material. However, in either scenario, the weld procedure qualification is in compliance with the requirements in ASME Code Case N-638-11.

5.4 Conclusions Implementation of the FSWOL alternative described in Attachments 2 and 3 of this request produces effective mitigation of PWSCC in the identified welds and maintains the nozzle geometry to permit future ASME Code, Appendix VIII UT examinations as implemented through the POI Program. FSWOL mitigation of DMWs has been installed and performed successfully for many years in both PWR and BWR applications. The alternative provides improved structural integrity and reduces the likelihood of leakage at the nozzles. Accordingly, the use of the alternative provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1 ).

6.0 DURATION OF PROPOSED ALTERNATIVE The duration of this relief request is for the remainder of the 60-year licensed operational life (until 2031) plus an additional 20-year operational life extension. The design considers operation for the remainder of the 60-year licensed operational life (until 2031) plus an additional 20-year operational life. The modifications installed in accordance with the provisions of this relief shall remain in place for the remaining operational life of the plant/modification.

PNP 2025-059 Page 15 of 20 7.0 PRECEDENTS

1.

Nine Mile Point Nuclear Station, Unit 1-Authorization And Safety Evaluation for Alternative Relief No. I5R-12 Concerning the Installation of a Full Structural Weld Overlay on Reactor Pressure Vessel Recirculation Inlet Nozzle N2E Safe End-To-Nozzle Dissimilar Metal Weld (EPID L-2023-LLR-0065) ADAMS Accession No. ML24145A186

[Safety Evaluation of Alternative Request I5R-12]

2.

Waterford Steam Electric Station, Unit 3 - Authorization of Proposed Alternative to ASME Code,Section XI, IWA-4000, "Repair/Replacement Activities" (EPID L-2019-LLR-0003) ADAMS Accession No. ML19232A025

[Safety Evaluation of Alternative Request WF3-RR-19-1]

3.

Brunswick Steam Electric Plant, Unit 2 - Relief From The Requirements of the ASME Code,Section XI, IWA-4000 (lnservice Inspection Program Alternative ISl-07) (CAC NO.

MF9561) ADAMS Accession No. ML17230A274

[Safety Evaluation of Alternative Request ISl-07]

4.

Millstone Power Station, Unit No. 2 - Alternative Use Of Weld Overlay As Repair And Mitigation Technique (TAC NO. MF3918) ADAMS Accession No. ML15082A409

[Safety Evaluation of Alternative Request RR-04-20]

5.

Three Mile Island Nuclear Station, Unit 1 -Proposed Alternative RR-12-02 Regarding Weld Overlay of The Lower Cold Leg Letdown Nozzle Dissimilar Metal Welds And Alloy 600 Safe-End (TAC NO. ME9818) ADAMS Accession No. ML13134A467

[Safety Evaluation of Alternative Request RR-12-02]

PNP 2025-059 Page 16 of 20

8.0 REFERENCES

1.

American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)Section XI, 2007 Edition with the 2008 Addenda

2.

ASME Code Section Ill, 1965 Edition and Addenda through Winter 1966

3.

ASME Code Case N-638-4, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,Section XI, Division 1, Approval Date: October 5, 2006

4.

ASME Code Case N-638-11, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,Section XI, Division 1, Approval Date: August 2, 2019

5.

ASME Code Case N-740-2, Full Structural Dissimilar Metal Weld Overlay for Repair or Mitigation of Class 1, 2, and 3 Items,Section XI, Division 1, Approval Date:

November 10, 2008

6.

ASME Code Case N-770-7, Alternative Examination Requirements and Acceptance Standards for Class 1 PWR Piping and Vessel Nozzle Butt Welds Fabricated With UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of Listed Mitigation Activities,Section XI, Division 1, Approval Date: December 4, 2020

7.

NRC Regulatory Guide 1.147, Revision 21, lnservice Inspection Code Case Acceptability, ASME Section XI, Division 1, ADAMS Accession Number ML23291A003

8.

Framatome Evaluation 51-9384372-000, Life Assessment Summary for Palisades Hot Leg Surge, Hot Leg Shutdown Cooling, Cold Leg Safety Injection, Pressurizer Surge, and Pressurizer Relief Weld Overlays (Proprietary)

9.

EPRI Report 1006696, Materials Reliability Program Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Alloy 82, 182, and 132 Welds (MRP-115), EPRI, Palo Alto, CA: 2004..

10.

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

11.

EPRI Report 1015009, Materials Reliability Program: Primary System Piping Butt Weld Inspection and Evaluation Guideline (MRP-139, Revision 1 ). EPRI, Palo Alto, CA: 2008.

12.

EPRI Report GC-111050, Ambient Temperature Preheat for Machine GTAW Temper bead Applications; EPRI, Palo Alto, CA: 1999.

13.

EPRI Report 1025169, "Welding and Repair Technology Center: Welding and Repair Technical Issues in ASME Section XI", EPRI, Palo Alto, CA: 2012.

PNP 2025-059 Page 17 of 20

14.

Arkansas Nuclear One, Unit 2 -Approval Of Request For Alternative From Certain Requirements Of The American Society Of Mechanical Engineers Boiler And Pressure Vessel Code (EPID L-2021-LLR-0084) ADAMS Accession Number ML22073A095,

15.

Arkansas Nuclear One, Unit 2 - Authorization And Safety Evaluation For Alternative Request No. ANO2-RR-24-001 (EPID L-2024-LLR-0065) ADAMS Accession Number ML25107A057.

PNP 2025-059 Page 18 of 20 Figure 1 Schematic Configuration of the Hot Leg Surge, Hot Leg Shutdown Cooling, and Pressurizer Surge Nozzles with FSWOLs WELD OVERLAY TOE-,

TAPER i TRANSmON CLADDING TYPE 304 STAINLESS STEEL FSWOL ALLOY 52Mf52MSS (P-No. 43)

J... ---t -------------.. --- --

DMW

\\

DMW ALLOY 82/182 (P-No_ 43) ___ \\

, ___ ALLOY 82/182 (P-No. 43) f-c-+--+-t---

NOZZLE HOT LEG SURGE: A508, CLASS 1 (P-No. 1)

SAFE END BUFFER LAYER ER309L (P-No. 8 )

\\

WELD OVERLAY

\\

TOE l

TAPER

\\

! TRANSITION

\\

)

1---.,-,----,-

\\

1

\\

1i I

\\

HOT LEG SHUTDOWN COOLING: SA-508, CLASS 1 (P-No. 1)

PRESSURIZER SURGE: A508, CLASS 2,(P-No. 3)

SB-166, ALLOY 600 (P-No. 43)

Note: The figure above depicts the general configuration of the Hot Leg Surge, Hot Leg Shutdown Cooling, and Pressurizer Surge Nozzles with FSWOLs. The orientation and nozzle, safe end, and FSWOL geometry vary between the three locations.

PNP 2025-059 Page 19 of 20 Figure 2 Schematic Configuration of the Cold Leg Safety Injection Nozzles with FSWOLs FSWOL ALLOY 52M/52MSS (P-No. 43) i i

i i

i BRIDGE LAYER BUFFER LA YER ER309L (P-No. 8)

DMW

\\

ALLOY 821182 (P-No. 43)

\\

-______ __i ____________.

+------

___ _ ___ ____L WELD OVERLAY i

TOE I

TAPER--!-__

TRANSITION i --------

CLADDING TYPE 304 !

STAINLESS STEEL i

\\

i i

WELD OVERLAY TOE TAPER TRANSITION SA-508, CLASS 1 (P-No. 1)

SB-166, ALLOY 600 (P-No. 43) 18--SSMO CAST STAINLESS STEEL (P-No. 8)

Note: The figure above depicts the general configuration of the four (4) Cold Leg Safety Injection Nozzles with FSWOLs.

PNP 2025-059 Page 20 of 20 Figure 3 Schematic Configuration of the Pressurizer PORV Nozzle with FSWOL BUFFER LAYER ER309L (P-No. 8)

FSWOL ALLOY 52M (P-No. 43)

DMW & BUTTERING REMNANT ALLOY 82 {P-No 43)

Sff NOTE REPLACEMENT SAFE END SA-479 TYPE 316 {P-No. Bl SEE NOTE WELD & BUTTERING ALLOY 52 (P-No. 43)

SEE NOTE WELD OVERLAY TOE ER TRANSITION CLADDING TYPE 304 STAJNLESS STEEL Note: The figure above depicts the general configuration of the Pressurizer PORV Nozzle with FSWOL. The original safe end and adjacent pipe for the PORV nozzle were replaced in 1995. A stainless steel safe end was welded to the nozzle with Alloy 52 weld metal. A remnant of the existing Alloy 182 butter and weld was left on the nozzle and encapsulated by an onlay on the inside diameter with Alloy 52 weld metal prior to attaching the new safe end.

PNP 2025-059 Page 1 of 9 ATTACHMENT 2 REQUIREMENTS FOR HOT LEG SURGE, HOT LEG SHUTDOWN COOLING, COLD LEG SAFETY INJECTION, PRESSURIZER SURGE, AND PRESSURIZER RELIEF DISSIMILAR METAL WELD OVERLAYS

PNP 2025-059 Page 2 of 9 A

2.1 INTRODUCTION

The following detailed requirements are applicable for the design, analyses, fabrication, examination, and pressure testing of the Hot Leg Surge, Hot Leg Shutdown Cooling, Cold Leg Safety Injection, Pressurizer Surge, and Pressurizer Relief dissimilar metal weld overlays. These requirements, which are derived from applicable portions of ASME Code Case N-7 40-2, provide an acceptable methodology for reducing potential defects in these austenitic nickel alloy welds to an acceptable size or mitigating the potential for future stress corrosion cracking by increasing the wall thickness through deposition of weld overlays.

The weld overlay will be applied by deposition of weld reinforcement (i.e., weld overlay) on the outside surface of the piping, nozzle, and associated dissimilar metal weld, including ferritic materials when necessary, in accordance with the following requirements:

A2.2 GENERAL REQUIREMENTS (Correlated to N-740-2, paragraph 1)

A2.2.1 DEFINITIONS (a)

Full structural weld overlay - deposition of weld reinforcement on the outside diameter of the piping, component, or adjacent 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 A2.2.1(b) and (c).

(b)

Mitigative weld overlay - weld overlay that is applied over material with no inside-surface-connected flaws found during an ultrasonic examination performed 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) sec susceptible materials - for this proposed alternative, the stress-corrosion-cracking (SCC) susceptible materials are Unified Numbering System (UNS) N06600, N06082, or W86182 in pressurized water reactor environments; or UNS N06600, W86182 surfaces with a nominal operating temperature equal to or greater than 525° and in contact with the reactor coolant environment.

PNP 2025-059 Page 3 of 9 A2.2.2 GENERAL OVERLAY REQUIREMENTS (a)

A full-structural weld overlay will be applied by deposition of weld reinforcement (i.e., weld overlay) on the outside surface of circumferential welds. This proposed method applies to austenitic nickel alloy welds between the following:

(1)

P-No. 8 or P-No. 43 and P-Nos. 1 or 3 (2)

P-No. 8 and P-No. 43 (b) The weld overlay will not obstruct a required examination of an adjacent weld.

(c) Weld overlay filler metal will be austenitic nickel alloy (i.e., 28% chromium minimum, ERNiCrFe-7/7A [see Note below]) meeting the requirements of A2.2.2(e)(1) 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 Repair/Replacement 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 Attachment 3 will be used.

Note:

ERNiCrFe-7A (Alloy 52M) and ERNiCrFe-13 (Alloy 52MSS) will be used. provides a technical basis for including other Alloy 52 variants that contain at least 28% Chromium as an acceptable filler material in N-770-7 as prescribed in 10 CFR 50.55a(g)(6)(ii)(F).

(d) Prior to deposition of the weld overlay, the surface to be weld overlaid will be examined using the liquid penetrant method in accordance with IWA-2222 using personnel qualified in accordance with IWA-2300. Indications with major dimensions greater than 1/16 in. (1.5 mm) will be removed, reduced in size, or weld repaired in accordance with the following requirements:

(1)

One or more layers of weld metal will be applied to seal unacceptable Indications in the area to be repaired with or without excavation. The thickness of these layers will 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 A2.2.2(d) is required, the area where the weld overlay is to be deposited, including any local weld repairs or initial weld overlay layer, will be examined by the liquid penetrant method. The area will contain no indications with major dimensions greater than 1/16 in. (1.5 mm) prior to application of the structural layers of the weld overlay.

PNP 2025-059 Page 4 of 9 (3)

To reduce the potential of hot cracking when applying an austenitic nickel alloy over P-No. 8 base metal, a layer or multiple layers of austenitic stainless steel filler material will be applied over the austenitic stainless steel base metal. The thickness of these buffer layers will not be used in meeting weld reinforcement design thickness requirements.

(e)

Weld overlay deposits will meet the following requirements:

The austenitic nickel alloy weld overlays will 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.

(f)

This alternative will only be used for welding in applications predicted not to have exceeded thermal neutron (E < 0.5 eV) fluence of 1 x 1017 neutrons per cm2 prior to welding.

(g)

A new weld overlay is not being installed over the top of an existing weld overlay that has been in service.

A2.3 FLAW GROWTH AND DESIGN (Correlated to N-740-2, paragraph 2)

(a)

Flaw Growth Calculation of Flaws in the Original Weld or Base Metal.

The size of the flaws detected in the base metal will be used to define the life of each overlay. Flaw growth due to both stress corrosion and fatigue, will be evaluated. The applicable crack growth flaw for the susceptible material shall be evaluated using Section XI, Nonmandatory Appendix C. Flaw characterization and evaluation will 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, an evaluation of flaw growth in both materials will be performed.

(1)

For repair overlays, the initial flaw size for crack growth in the original weld or base metal will be based on the as-found flaw from the result of a qualified ultrasonic examination performed in accordance with A2.4 or postulated flaw, if no pre-overlay examination is performed.

(2)

For postulated inside-surface-connected planar flaws, the axial flaw length will be 1.5 in. (38 mm) or the combined width of the weld plus buttering plus any adjacent SCC susceptible material, whichever is greater. The circumferential flaw length will be assumed to be 360 degrees. The depths associated with these lengths are specified in A2.3(a)(3).

PNP 2025-059 Page 5 of 9 (3)

If qualified ultrasonic examination is not performed in accordance with A2.4 prior to application of the overlay, initial inside-surface-connected planar flaws equal to at least 75% through the original wall thickness will be assumed, in both the axial and circumferential directions, and the overlay will be considered a repair. For cast austenitic stainless steel (CASS) items, a 100%

through-wall flaw will be assumed in the susceptible weld material in the limiting direction.

(4)

In determining the life of each overlay, any inside-surface-connected planar flaw found by the overlay preservice inspection that exceeds the depth of A2.3(a)(3) above will 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 will be considered a repair, rather than mitigation.

(b)

Structural Design and Sizing of the Overlay.

The design of the weld overlay will satisfy the following, using the assumptions and flaw characterization requirements in A2.3(a). The impact of the weld overlay on the validity of the component design will be evaluated as required by IWA-4311. In addition, the following requirements will be met:

(1)

The axial length and end slope of the weld overlay will 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 will 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 0.75Rt, where R is the outer radius of the item and tis the nominal wall thickness of the item at the applicable side of the overlay (i.e., Randt of the nozzle on the nozzle side and Randt of the safe-end on the safe-end side).

(2)

In accordance with A2.3(b)(1 ), the end transition slope of the overlay will be analyzed for the design configuration.

(3)

The assumed flaw in the underlying base material or weld will be based on the limiting case of A2.3(b)(3)(-a) or (-b) which results in the larger required overlay thickness.

(-a) 100% through-wall circumferential flaw for the entire circumference.

(-b) 100% through-wall flaw with length of 1.5 in. (38 mm), or the combined width of the weld plus buttering plus any SCC-susceptible material, whichever is greater, in the axial direction.

PNP 2025-059 Page 6 of 9 (4)

The overlay design thickness will be verified, using only the weld overlay thickness conforming to the deposit analysis requirements of A2.2.2(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 within a distance of 2.5Rt, from the toes of the weld overlay, including the flaw size assumptions defined in A2.3(b)(3) above, will be evaluated and will 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 (e.g., support loads and clearances, nozzle loads, and changes in system flexibility and weight due to the weld overlay) will be evaluated. For the DWMs identified in Attachment 1, there are no existing flaws previously accepted by analytical evaluation that need to be evaluated in accordance with IWB-3640.

(c)

Residual Stress Analysis of the Overlay.

A residual stress analysis will be performed of the overlay and the underlying weld(s).

The residual stress analysis will include the residual stresses that exist prior to application of the overlay. The analysis will address residual stresses due to the as-welded condition plus any machining or weld repairs that were previously performed. A severe as-welded stress distribution for a 50%-through-wall 360 deg circumferential repair will be assumed as the starting point for the analysis. If construction records or inservice records show more severe repairs, they will be assumed in the analysis. The residual stress distribution may be modified considering the effects of PWHT, if applicable.

PNP 2025-059 Page 7 of 9 A2.4 EXAMINATION (Correlated to N-740-2, paragraph 3)

Nondestructive examination methods will be in accordance with IWA-2200, except as specified herein. Nondestructive examination personnel will be qualified in accordance with IWA-2300. Ultrasonic examination procedures and personnel will be qualified in accordance with the modified requirements to ASME Code,Section XI, Appendix VIII, Supplement 11 as described in Attachment 5. The examination will be performed, to the maximum extent practicable, for axial and circumferential flaws. If 100% coverage of the required volume for axial flaws cannot be achieved, but essentially 100% coverage for circumferential flaws (i.e., 100% of the susceptible volume) can be achieved, the examination for axial flaws will be performed to achieve the maximum coverage practicable, with limitations noted in the examination report. The examination coverage requirements will be considered to be met. For CASS components for which no supplement is available in Appendix VIII, the weld volume will be examined using Appendix VIII procedures to the maximum extent practicable.

(a)

Acceptance Examination (1)

The weld overlay will have a surface finish of 250 µin. (6.3 µm) 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 will be inspected to verify acceptable configuration.

(2)

The weld overlay and the adjacent base material for at least 1/2 in. (13 mm) from each side of the overlay will be examined using the liquid penetrant method. The weld overlay will satisfy the surface examination acceptance criteria for welds of the NB-5300. The adjacent base material will satisfy the surface examination acceptance criteria for base material of the NB-2500. If ambient temperature temper bead welding is performed, the liquid penetrant examination of the completed weld overlay will be conducted no sooner than 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months following completion of the three tempering layers over the ferritic steel.

PNP 2025-059 Page 8 of 9 (3)

The examination volume A-B-C-O in Figure A2-1 (a), shown below, which includes the overlay and welds made in accordance with A2.2.2(d) and (e),

will be ultrasonically examined to assure adequate fusion (i.e., adequate bond) with the base material and to detect welding flaws, such as interbead lack of fusion, inclusions, or cracks. The interface C-O 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 will be conducted no sooner than 48-hours following completion of the three tempering layers over the ferritic steel. Planar flaws detected in the weld overlay acceptance examination will meet the preservice examination standards of IWB-3514. In applying the acceptance standards to planar indications, the thickness, t1 orb defined in Figure A2-1(b) will be used as the nominal wall thickness in IWB-3514, provided the base material beneath the flaw (i.e., safe end, nozzle, or piping material) is not susceptible to stress corrosion cracking. For susceptible material, t1 will be used. If a flaw in the overlay crosses the boundary between the two regions t1 will be used. Planar flaws at or near the weld overlay interface may be evaluated as subsurface flaws provided there were no through-wall leaks in that area prior to weld overlay application. Laminar flaws in the weld overlay will meet the following requirements:

(-a)

The acceptance standards of IWB-3514 will be met, with the additional limitation that the total laminar flaw area will not exceed 10% of the weld surface area and that no linear dimension of the laminar flaw area will exceed the greater of 3 in. (76 mm) or 10% of the pipe circumference.

(-b)

For examination volume A-B-C-O in Figure A2-1(a), the reduction in coverage due to laminar flaws will be less than 10%. 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 will be assumed to contain the largest radial planar flaw that could exist within that volume.

This assumed flaw will meet the preservice examination acceptance standards of IWB-3514, with nominal wall thickness as defined above the planar flaws. Assumed flaws located at or near the weld overlay interface may be evaluated as subsurface flaws provided there were no through-wall leaks in that area prior to the weld overlay application.

Alternatively, the assumed flaw will be evaluated and meet the requirements of IWB-3640, IWC-3640, and IWD-3640, as applicable.

Both axial and circumferential planar flaws will be assumed.

(-d)

The flaw evaluations defined in A2.4(a)(3)(-b) and (-c) shall be performed separately using the actual values measured with qualified procedures and do no require IWA-3360 proximity evaluation.

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

PNP 2025-059 Page 9 of 9 Figure A2-1 Examination Volume and Thickness Definitions Acceptance Examination Volume and Thickness Definitions A

D (a) Examination Volume A-B-C-O t,

A D

(bl Thickness (t 1 and t2) for Table IWB-3514-1 GENERAL NOTES:

B C

(a)

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

(b)

The nominal wall thickness is t 1 for flaws in E-F-G-H, and t2 for flaws in A-E-H-D or F-B-C-G.

(c)

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

B C

(d)

The weld includes the nozzle or safe end butter, where applied, plus any SCC-susceptible base material in the nozzle.

PNP 2025-059 Page 1 of 6 ATTACHMENT 3 AMBIENT TEMPERATURE TEMPER BEAD WELDING

PNP 2025-059 Page 2 of 6 A3.1 GENERAL REQUIREMENTS (Correlated to N-740-2, Mandatory Appendix I, Paragraph 1-1)

(a) This Attachment applies to dissimilar austenitic filler metal welds between P-Nos. 1 and 3 materials and their associated welds and welds joining P-No. 8 or 43 materials to P-Nos. 1 and 3 materials.

(b) The maximum area of an individual weld overlay based on the finished surface over the ferritic base material will be 500 in2 (325,000 mm2).

(c) Repair/replacement 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 in. (3 mm) 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 3/8 in. (10 mm).

(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 in. (130 mm), whichever is less, will be at least 50°F (10°C).

(f)

Welding materials will meet the Owner's Requirements and the Construction Code and Cases specified in the Repair/Replacement Plan. Welding materials will be controlled so that they are identified as acceptable until consumed.

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

A3.2 WELDING QUALIFICATIONS (Correlated to N-740-2, Mandatory Appendix I, Paragraph 1-2)

(a) The welding procedures and welding operators will be qualified in accordance with ASME Code Section IX and the requirements of A3.2.1 and A3.2.2.

(b) Existing welding procedure and welding operator qualifications performed in accordance with ASME Code Case N-638-11 or any previous revisions of Case N-638 may be used without requalification.

PNP 2025-059 Page 3 of 6 A3.2.1 PROCEDURE QUALIFICATION (a) The base material for the welding procedure qualification shall be of the same P-Number and Group Number as the materials to be welded. Prior simulated postweld heat treatment on the procedure qualification test assembly is neither required nor prohibited. However, if used, the simulated postweld heat treatment shall not exceed the time or temperature already applied to the base material to be welded.

(b) The maximum interpass temperature for the first three layers of the test assembly will be 150°F (66°C).

(c) The weld overlay will be qualified using groove weld coupon. The test assembly groove depth will be at least 1 in. (25 mm). The test assembly thickness will be at least twice the test assembly groove depth. The test assembly will be large enough to permit removal of the required test specimens. The test assembly dimensions on either side of the groove will be at least 6 in. (150 mm). The qualification test plate will be prepared in accordance with Figure A3-1 below.

(d) Ferritic base material for the procedure qualification test will 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 will 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 will be similar to those required in A3.2.1 ( e) but will be in the base metal.

(e) Charpy V-notch tests of the ferritic heat-affected zone (HAZ) will be performed at the same temperature as the base metal test of A3.2.1 (d). Number, location, and orientation of test specimens will be as follows:

(1)

The specimens will 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 will be taken transverse to the axis of the weld and etched to define the HAZ. The notch of the Charpy V-notch specimen will 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 will be inclined to allow the root of the notch to be aligned parallel to the fusion line.

(2)

If the material thickness permits, the axis of a specimen will 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 will be oriented parallel to the principal direction of rolling or forging.

PNP 2025-059 Page 4 of 6 (4) The Charpy V-notch test will be performed in accordance with SA-370. Specimens will be in accordance with SA-370, Figure 11, Type A. The test will consist of a set of three full-size 10 mm by 10 mm specimens. The lateral expansion, percent shear, absorbed energy, test temperature, orientation, and location of all test specimens will be reported in the Procedure Qualification Record.

(f)

The average lateral expansion value of the three HAZ Charpy V-notch specimens will 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 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 will be performed:

(1)

The welding procedure will be requalified.

(2)

An Adjustment Temperature for the procedure qualification will be determined in accordance with the applicable provisions of Paragraph NB-4335.2 of Section Ill, 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 will be increased by a temperature equivalent to that of the Adjustment Temperature.

A3.2.2 PERFORMANCE QUALIFICATION Welding operators will be qualified in accordance with ASME Code,Section IX.

A3.3 WELDING PROCEDURE REQUIREMENTS (Correlated to N-740-2, Mandatory Appendix I, Paragraph 1-3)

The welding procedure will include the following requirements:

(a)

The weld metal will be deposited by the machine gas tungsten arc welding process.

(b)

Dissimilar metal welds will be made using F-No. 43 weld metal (i.e., QW-432) for P-No. 8 or 43 to P-No. 1 or 3 weld joints.

PNP 2025-059 Page 5 of 6

( c)

The area to be welded will be buttered with a deposit of at least three layers to achieve at least 1/8 in. (3 mm) 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 will not exceed 45 kJ/in. (1.8 kJ/mm) under any conditions. Particular care will 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 will 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 will be 350°F (180°C) for all weld layers regardless of the interpass temperature used during qualification. The interpass temperature limitation of QW-406.3 will not be applied.

(e)

The interpass temperature will be determined as follows:

(1) Temperature measurement (e.g., pyrometers, temperature-indicating crayons, and thermocouples) during welding. If direct measurement is impractical, interpass temperature will be determined in accordance with A3.3(e)(2) or (3).

(f)

Particular care will 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 will be suitably controlled.

PNP 2025-059 Page 6 of 6 Figure A3-1 Qualification Test Plate Qualification Test Plate Discard Transverse side bend Reduced section tensile Transverse side bend

,A..

HAZ Charpy

/'._

V-notch

/'...

Transverse side bend Reduced section tensile Transverse side bend Discard I

I I

~ Fusion 1

line rTWeld metal

":;~ct,,--;a; zone (HAZ)

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

PNP 2025-59 Page 1 of 17 ATTACHMENT 4 REVIEW OF ASME CODE CASE N-740-2 AGAINST THE PROPOSED ALTERNATIVE WELD OVERLAY

PNP 2025-059 Page 2 of 17 ASME Code Case N-740-2 Requirement

1. GENERAL REQUIREMENTS 1.1 DEFINITION (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 (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 2(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 Case, the stress-corrosion-cracking (SCC) susceptible materials are UNS N06600, N06082, or W86182 in PWR environment; or UNS N06600, W86182, or austenitic stainless steels and associated welds in BWR environments.

Included in Proposed Justification Alternative?

N/A N/A N/A N/A Yes This definition applies to the proposed alternative No This definition does not apply to the proposed alternative since ultrasonic examinations of the base material were not performed prior to the weld overlays being applied.

Yes This definition applies to the proposed alternative Yes The referenced materials are also recognized as susceptible materials in ASME Code,Section XI, 2007 Edition with 2008 addenda.

PNP 2025-059 Page 3 of 17 ASME Code Case N-740-2 Requirement 1.2 GENERAL OVERLAY REQUIREMENTS (a) A full-structural weld overlay will be applied by deposition of weld reinforcement (weld overlay) on the outside surface of circumferential welds.

This Case applies to austenitic nickel alloy and austenitic stainless-steel welds between the following:

(I) P-No. 8 or P-No. 43 and P-Nos. 1, 3, 12A, 12B, or 12C1 (2) P-No. 8 and P-No. 43 (3) Between P-Nos. 1, 3, 12A, 12B, and 12C1 materials (b) If a weld overlay on any of the material combinations in (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.

Included in Proposed Alternative?

N/A Yes No Justification N/A ASME Code Case N-740-2 was specifically written to address the application of weld overlays over dissimilar metal welds and austenitic stainless steel welds Excei:2tion to N-740-2 (highlighted in bold}:

The alternative is used only for the following:

P-No.8 to P-No. 3 P-No.8 to P-No. 43 P-No.43 to P-No. 1 P-No.43 to P-No. 3 The weld overlays do not obstruct the required examination of any adjacent P-No. 8 to P-No. 8 weld.

PNP 2025-059 Page 4 of 17 ASME Code Case N-740-2 Requirement (c) Weld overlay filler metal will be austenitic nickel alloy (28% Cr min.,

ERNiCrFe-7/7 A) meeting the requirements of (e)(1) or (e)(2), as applicable, applied 360 deg 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 Repair/Replacement Plan. As an alternative to the post weld heat treatment (PWHT) requirements of the Construction Code and Owner's requirements, the provisions of Mandatory Appendix I may be used for ambient-temperature temper bead welding.

(1) For P-No. 1 base materials, the Construction Code PWHT exemptions permitted for circumferential butt welds may be applied to exempt the weld overlay from PWHT, with the following clarifications:

(-a) The nominal weld thickness is defined as the maximum overlay thickness applied over the ferritic base material.

(-b) The base material thickness is defined as the maximum thickness of the ferritic material where the overlay is applied.

Included in Proposed Alternative?

Yes No Justification The weld filler metal and procedure requirements of ASME Code Case N-740-2 are equivalent to ASME Code,Section XI, Nonmandatory Appendix Q, which is accepted for use by the NRG.

Regarding the welding procedure specification (WPS),

the requirements of Attachments 2 and 3 provide clarification that the WPS used for depositing weld overlays must be qualified as a groove welding procedure to ensure that mechanical properties of the 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 Attachment 1, Section 5.3.

Exception to N-740-2 (highlighted in bold}:

ERNiCrFe-7A (Alloy 52M) and ERNiCrFe-13 (Alloy 52MSS) will be used. Attachment 6 provides a technical basis for including other Alloy 52 variants that contain at least 28% Chromium as an acceptable filler material in N-770-7 as prescribed in 10 CFR

50. 55a(g)(6 )(i i)(F).

Ambient-temperature temper bead welding will be performed in accordance with Mandatory Appendix I as specified in Attachment 3 and discussed below.

PNP 2025-059 Page 5 of 17 ASME Code Case N-740-2 Requirement (2) If ambient-temperature temper bead welding is used, Mandatory Appendix I will be used.

(d) Prior to deposition of the weld overlay, the surface to be weld overlaid will be examined using the liquid penetrant method. Indications with major dimensions greater than 1/16 in. (1.5 mm) will be removed, reduced in size, or weld repaired in accordance with the following requirements:

(1) One or more layers of weld metal will be applied to seal unacceptable indications in the area to be repaired with or without excavation. The thickness of these layers will 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 (d) is required, the area where the weld overlay is to be deposited, including any local weld repairs or initial weld overlay layer, will be examined by the liquid penetrant method. The area will contain no indications with major dimensions greater than 1/15 in.

(1.5 mm) 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 thickness of these layers will not be used in meeting weld reinforcement design thickness requirements. The filler material used will meet the minimum requirements for delta ferrite.

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

Included in Proposed Justification Alternative?

Yes Ambient-temperature temper bead welding will be performed in accordance with Mandatory Appendix I as specified in Attachment 3 and discussed below.

Yes The requirements for examination prior to deposition of the weld overlay in ASME Code Case N-740-2 are equivalent to ASME Code,Section XI, Nonmandatory Appendix Q, Q-2000 which has been accepted for use by the NRC.

Yes The requirements for examination prior to deposition of the weld overlay in N-740-2 are equivalent to ASME Code,Section XI, Nonmandatory Appendix Q, Q-2000 which has been accepted for use by the NRC.

Yes The requirements for examination prior to deposition of the weld overlay in ASME Code Case N-740-2 are equivalent to ASME Code,Section XI, Nonmandatory Appendix Q, Q-2000 which has been accepted for use by the NRC.

Yes A minimum of one layer of Alloy 82 and ER309L filler material will be applied over the P-No. 8 base metal to prevent the potential of hot cracking of the Alloy 52M/Alloy 52MSS weld overlay material.

See below Only the requirements of N-740-2(e)(2) are applicable, as indicated below.

PNP 2025-059 Page 6 of 17 ASME Code Case N-740-2 Requirement (1) The austenitic stainless steel weld overlay will consist of at least 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 at least 7.5 FN will constitute the first layer of the weld reinforcement that may be credited toward the required thickness. Alternatively, layers of at least 5 FN are acceptable, provided the carbon content of the deposited weld metal is determined by chemical analysis to be less than 0.02%.

(2) The austenitic nickel alloy weld overlay will consist of at least two weld layers deposited using a filler material with a Cr content of at least 28%. The first layer of weld metal deposited may not be credited toward the required thickness. Alternatively, for PWR applications, 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% 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. 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.

(f) This Case is only for welding in applications predicted not to have exceeded thermal neutron (E < 0.5 eV) fluence of 1 x 1017 neutrons per cm2 prior to welding.

Included in Proposed Justification Alternative?

No The requirements of N-740-2(e)(1) are not applicable because Alloy 52M/Alloy 52MSS material will be used for the FSWOL.

Yes The weld overlays will be deposited with ERNiCrFe-7A (Alloy 52M) and ERNiCrFe-13 (Alloy 52MSS) filler metals, which have been included into ASME Code Section IX as F-No. 43 filler metals. Containing 28.0 -

31.5 and 28.5 - 31.0 percent chromium, respectively (i.e., roughly twice the chromium content of 82/182 filler metal), these filler metals have excellent resistance to stress corrosion cracking. This point has been clearly documented in EPRI Technical Report MRP-115, Section 2.2 (Reference 9).

The first deposited layer will not be credited toward the required thickness of the FSWOLs.

Exce(2tion to N-740-2 (highlighted in bold}:

Alternative requirements for crediting the dilution layer for PWRs will not be used.

Alternative requirements for BWR applications are not applicable.

Yes Holtec confirms the thermal neutron fluence at the FSWOL locations is less than the threshold specified.

PNP 2025-059 Page 7 of 17 ASME Code Case N-740-2 Requirement (g) A new weld overlay will not be installed over the top of an existing weld overlay that has been in service.

2 CRACK GROWTH AND DESIGN (a) Crack Growth Calculation of Flaws in the Original Weld or Base Metal.

The size of the flaw detected in the base metal will be used to define the life of each overlay. The inspection interval will not be longer than the shorter of the life of the overlay or the period specified in 3(c). Crack growth due to both stress corrosion and fatigue, will be evaluated. Flaw characterization and evaluation will be based on the examination result 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 will 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 will be 1.5 in. (38 mm) or the combined width of the weld plus buttering plus any adjacent sec susceptible material, whichever is greater. The circumferential flaw length will be assumed to be 360 degrees. The depths associated with these lengths are specified in (3) and (4).

Included in Proposed Alternative?

Yes N/A Yes Yes Yes Justification The proposed alternative is the first application of a weld overlay on these welds.

N/A The requirements in 2(a) are equivalent, or more stringent, than those specified in Nonmandatory Appendix Q. ASME Code,Section XI, Nonmandatory Appendix Q has been accepted for use by the NRC.

These requirements will ensure that the growth of the flaw will be accounted for in the design of the overlay.

Exce(2tion to N-740-2 (highlighted in bold}:

lnservice inspections will be performed in accordance with ASME Code Case N-770-7, as prescribed in 10 CFR 50.55a(g)(6)(ii)(F), will be used instead of 3(c) of N-740-2.

This requirement is applicable to the proposed alternative per 2(a)(4) below This requirement is met as a 100% through-wall axial flaw with flaw length-to-depth ratio equal to 4 and a 100% through-wall 360° circumferential flaw will be assumed in the crack growth evaluation of the FSWOLs on the NPS 12 Sch 140 nozzles, and a 75%

through-wall axial flaw with flaw length-to-depth ratio equal to 4 and a 75% through-wall 360° circumferential flaw will be assumed in the crack growth evaluation of the PORV FSWOL.

PNP 2025-059 Page 8 of 17 ASME Code Case N-740-2 Requirement (3) If an 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 will be assumed in both the axial and circumferential directions, and the overlay will be considered mitigative.

(4) If an 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 will be assumed, in both the axial and circumferential directions, and the overlay will be considered a repair. For cast austenitic stainless steel (CASS) items, a 100 percent through-wall flaw will be assumed unless the subsequent in-service inspection schedule is modified as discussed in 3(c)(8).

(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. 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.

Included in Proposed Justification Alternative?

No This requirement is not applicable because ultrasonic examinations will not be performed prior to application of the overlay.

Yes This requirement is met as a 100% through-wall axial flaw with flaw length-to-depth ratio equal to 4 and a 100% through-wall 360° circumferential flaw will be assumed in the crack growth evaluation of the FSWOLs on the NPS 12 Sch 140 nozzles, and a 75%

through-wall axial flaw with flaw length-to-depth ratio equal to 4 and a 75% through-wall 360° circumferential flaw will be assumed in the crack growth evaluation of the PORV FSWOL.

No This requirement is met as a 100% through-wall axial flaw with flaw length-to-depth ratio equal to 4 and a 100% through-wall 360° circumferential flaw will be assumed in the crack growth evaluation of the FSWOLs on the NPS 12 Sch 140 nozzles, and a 75%

through-wall axial flaw with flaw length-to-depth ratio equal to 4 and a 75% through-wall 360° circumferential flaw will be assumed in the crack growth evaluation of the PORV FSWOL.

PNP 2025-059 Page 9 of 17 ASME Code Case N-740-2 Requirement (6) In determining the life of each overlay, any inside-surface-connected planar flaw found by the overlay preservice inspection that exceeds the depth of (3), (4 ), or (5) above will 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 will be considered a repair, rather than mitigation.

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

(1) The axial length and end slope of the weld overlay will cover the weld and heat-affected zones on each side of the weld, as well as any SCC-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 will 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 sec susceptible material or projected flaw by at least 0.75 v(Rt), 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 (i.e., R and t of the nozzle on the nozzle side and R and t of the safe-end on the safe-end side).

Included in Proposed Justification Alternative?

Yes For the FSWOLs on the NPS 12 Sch 140 nozzles this requirement is met as a 100% through-wall axial flaw with flaw length-to-depth ratio equal to 4 and a 100%

through-wall 360° circumferential flaw will be assumed in the crack growth evaluation of the FSWOLs.

For the Pressurizer PORV FSWOL, if any crack-like flaws are identified in the upper 25 percent of the original weld or base material by the preservice examination, then the as-found flaw (i.e., postulated 75% through-wall flaw plus the portion of the flaw in the upper 25%) shall be used for the crack growth analysis.

Yes This requirement is met, as indicated below.

Yes These requirements are essentially the same as ASME Code,Section XI, Nonmandatory Appendix Q, Article Q-3000(b )( 1 ), which has been accepted for use by the NRC.

PNP 2025-059 Page 10 of 17 ASME Code Case N-740-2 Requirement (2) Unless specifically analyzed in accordance with (1 ), the end transition slope of the overlay will not exceed 30 deg.

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

(-a) 100% through-wall circumferential flaw for the entire circumference

(-b) 100% through-wall flaw with length of 1.5 in. (38 mm) 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 will be verified, using only the weld overlay thickness conforming to the deposit analysis requirements. 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 within a distance of 2.5 v(Rt), from the toes of the weld overlay, including the flaw size assumptions defined in (3), above, will be evaluated and will meet the requirements of IWB-3640, IWC3640, or IWD-3640, as applicable.

Included in Proposed Justification Alternative?

Yes This requirement is similar to ASME Code,Section XI, Nonmandatory Appendix Q, Article Q-3000(b)(2), which has been accepted for use by the NRC, except that Appendix Q, Article Q-3000(b)(2), specifies a maximum angle of 45 degrees, which is less stringent than this requirement.

The proposed alternative will comply with the N-740-2 requirement.

Yes The sizing calculation for each FSWOL design considers both cases and determines the minimum structural FSWOL thickness based on the case that results in the larger required FSWOL thickness.

Yes These requirements are essentially the same as ASME Code,Section XI, Nonmandatory Appendix Q, Article Q-3000(b)(3), which has been accepted for use by the NRC.

PNP 2025-059 Page 11 of 17 ASME Code Case N-740-2 Requirement (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 (e.g.,

support loads and clearances, nozzle loads, and changes in system flexibility and weight due to the weld overlay) will be evaluated. Existing flaws previously accepted by analytical evaluation will be evaluated in accordance with IWB-3640, IWC-3640, or IWD-3640, as applicable.

3 EXAMINATION In lieu of all other examination requirements, the examination requirements of this Case 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 Appendix VIII, Supplement 11. The examination shall be performed to the maximum extent practicable, for axial and circumferential flaws. If 100%

coverage of the required volume for axial flaws cannot be achieved, but essentially 100% coverage for circumferential flaws (100% 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 shall be considered to be met. For cast stainless steel components for which no supplement is available in Appendix VIII, the weld volume shall be examined using Appendix VIII procedures to the maximum extent practicable.

Included in Proposed Justification Alternative?

Yes The requirement is more stringent than ASME Code,Section XI, Nonmandatory Appendix Q, Article Q-3000(b)(4), which has been accepted for use by the NRC.

Exception to N-740-2 (highlighted in bold}

There is no existing flaws previously accepted by analytical evaluation that need to be evaluated in accordance with IWB-3640 Yes The proposed alternative will comply with this requirement.

Exceptions to N-740-2 (highlighted in bold}:

Preservice and inservice inspections will be performed in accordance with ASME Code Case N-770-7, as prescribed in 10 CFR 50.55a(g)(6)(ii)(F).

Ultrasonic examination personnel will be qualified in accordance with the modified requirements of Appendix VIII, Supplement 11 as described in.

PNP 2025-059 Page 12 of 17 ASME Code Case N-740-2 Requirement (a) Acceptance Examination

{l) The weld overlay will have a surface finish of 250 µin. (6.3 µm) RMS or better and contour that permits ultrasonic examination in accordance with procedures qualified in accordance with Appendix VIII. The weld overlay will be inspected to verify acceptable configuration.

(2) The weld overlay and the adjacent base material for at least 1/2 in. (13 mm) from each side of the overlay will be examined using the liquid penetrant method. The weld overlay will satisfy the surface examination acceptance criteria for welds of the Construction Code or NB-5300. The adjacent base material will 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 will be conducted no sooner than 48 hr following completion of the three tempering layers over the ferritic steel.

Included in Proposed Justification Alternative?

Yes The surface finish requirements of ASME Code Case N-740-2 are the same as ASME Code,Section XI, Nonmandatory Appendix Q, Article Q-4100 which has been accepted for use by the NRC.

Exception to N-740-2 (highlighted in bold}:

Ultrasonic examination procedures will be qualified in accordance with the modified requirements of Appendix VIII, Supplement 11 as described in.

Yes The surface examination requirements and acceptance criteria for the weld overlay and adjacent base material are equivalent to ASME Code,Section XI, Nonmandatory Appendix Q, Article Q-4100 which has been accepted for use by the NRC.

PNP 2025-059 Page 13 of 17 ASME Code Case N-740-2 Requirement (3) The examination volume A-B-C-D in Figure 1 (a) will be ultrasonically examined to assure adequate fusion (i.e., 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 will be conducted no sooner than 48 hr. following completion of the three tempering layers over the ferritic steel. Planar flaws detected in the weld overlay acceptance examination will meet the preservice examination standards of IWB-3514. In applying the acceptance standards to planar indications, the thickness, t1, or t2 defined in Figure 1 (b ), will be used as the nominal wall thickness in IWB-3514, provided the base material beneath the flaw (i.e., safe end, nozzle, or piping material) is not susceptible to SCC. For susceptible material, t1 will be used. If a flaw in the overlay crosses the boundary be-tween the two regions, the more conservative of the two dimensions (t1 or t2) will be used. Laminar flaws in the weld overlay will meet the following requirements:

(-a) The acceptance standards of IWB-3514 will be met, with the additional limitation that the total laminar flaw area will not exceed 10% of the weld surface area and that no linear dimension of the laminar flaw area will exceed the greater of 3 in. (76 mm) or 10% of the pipe circumference

(-b) For examination volume A-B-C-D in Figure 1 (a), the reduction in coverage due to laminar flaws will be less than 10%. 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.

Included in Proposed Justification Alternative?

Yes The examination requirements in ASME Code Case N-740-2, Figure 1(a) are identical to those specified in Section XI, Nonmandatory Appendix Q, Figure Q-4100-1, which has been accepted for use by the NRC.

Yes The proposed acceptance standards in IWB-3514 have been accepted by the NRC in Section XI, Nonmandatory Appendix Q for use.

The proposed alternative will comply with the additional limitations of N-740-2.

Yes ASME Code Case N-7 40-2, Figure 1 (a) is equivalent to ASME Code,Section XI, Nonmandatory Appendix Q, Figure Q-4100-1, which has been accepted by the NRC for defining the acceptance examination volume for weld overlay repairs. Q-41 00(c)(1) of Nonmandatory Appendix Q contains the 10% limit.

PNP 2025-059 Page 14 of 17 ASME Code Case N-740-2 Requirement

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

Alternatively, the assumed flaw will be evaluated and meet the requirements of IWB-3640, IWC-3640, and IWD-3640, as applicable. Both axial and circumferential planar flaws will be assumed.

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

Included in Proposed Justification Alternative?

Yes The acceptance standards in ASME Code Case N-740-2 for the weld overlay are equivalent to, or more stringent than, the rules of ASME Code,Section XI, Nonmandatory Appendix Q, Article 04100 which has been accepted for use by the NRC. Q-4100(c)(2) of Nonmandatory Appendix Q contains the assumed flaw size.

Yes A VT-3 visual examination of all affected restraints, supports, or snubbers (if applicable) will be performed to ensure that they have been returned to the design configuration following application of the FSWOLs.

PNP 2025-059 Page 15 of 17 ASME Code Case N-740-2 Requirement N-740-2 Figure 1, Acceptance Examination Volume and Thickness Definitions Figure 1 Acceptance Examination Volume and Thickness Definitions (a) Examination Volume A-B-C-0 A

r-b, r-b7 0

12 (b) Thicknessit, and t,J for Table IWB-3514-2 GENERAL NOTES,

[a)

Dimen~on b is equivalent to the nominal thickness of the nozrl, or pipe being overlaid, as appropr.at,.

[b) The nominal wall thicknm isl, for flaws in E-F*G-H,and t, forfiaws in A*E*H*D or F*B*C*G.

[c) For flaws that scan hvo examination volumes (such as illustr.ted in F*G) the i, thickness shall be us,d, (d) The weld includes the noul, or safe end butter, whm applied. plus any sec-susceptible base mate:ial in the noule.

Included in Proposed Alternative?

Yes Justification Figure 1 (a) is similar to ASME Code Section XI, Nonmandatory Appendix Q, Figure Q-4100-1, which has been accepted by the NRC.

The examination volume required by Figure 1 (b) is specified to ensure that the portion of the FSWOL that covers the DM weld is capable of providing structural integrity in lieu of the underlying DM weld. Flaws in this region of the FSWOL are evaluated using the thickness t1 when applying the acceptance standards of IWB-3514.

Exception to N-740-2, Figure 1 In Detail (b), "Table IWB-3514-2" is a typo and should be "Table IWB-3514-1". In General Note (c), "scan" should be "span", and "t" should be 11 These are being corrected in ASME Code Case N-740-3.

PNP 2025-059 Page 16 of 17 ASME Code Case N-740-2 Requirement (b) Preservice Inspection (c) lnservice Inspection 4 PRESSURE TESTING A system leakage test will be performed in accordance with IWA-5000.

5 DOCUMENTATION Use of this Case will be documented on Form NIS-2.

Included in Proposed Alternative?

No No Yes Yes Justification The preservice inspection will be performed in accordance with N-770-7 as prescribed in 10 CFR

50. 55a(g)(6 )(i i)(F).

The inservice inspection will be performed in accordance with N-770-7 as prescribed in 10 CFR

50. 55a(g)(6 )(i i)(F).

IWA-5214 requires a preservice system pressure test following repair/replacement activities in accordance with IWA-4540. IWA-4540(b)(3) exempts welding or brazing that does not penetrate through the pressure boundary from a pressure test and VT-2 examination.

The FWSOL does not penetrate through the full thickness of the pressure boundary and is therefore exempt from the pressure testing requirements of IWA-4540.

However, the FSWOL is within the boundary of IWB-5222(a) and will be subject to pressurization and a VT-2 examination as part of the Class 1 system leakage test prior to return to service.

Documentation of the use of this ASME Code Case in the post outage summary report is an administrative requirement.

PNP 2025-059 Page 17 of 17 ASME Code Case N-740-2 Requirement MANDATORY APPENDIX I, AMBIENT-TEMPERATURE TEMPER BEAD WELDING Included in Proposed Alternative?

Yes Justification Ambient temperature temper bead welding will be performed in accordance with Mandatory Appendix I, as specified in Attachment 3 of this Relief Request. The requirements in Mandatory Appendix I were taken from ASME Code Case N-638-4, which was conditionally approved by the NRC in RG 1.14 7 with conditions related to nondestructive examination (NDE) and to interpass temperature measurement. Holtec will meet the additional requirements specified in RG 1.147.

The NRC previously approved the use of the Mandatory Appendix I requirements for DMW FSWOLs in Precedents 3 and 5 listed in Attachment 1, Section 7.0.

Exceptions to N-740-2, Mandatory Appendix I:

Paragraph 1-2 is updated to incorporate subparagraph 2(b) of ASME Code Case N-638-11, which has been unconditionally approved by the NRC.

Paragraph 1-2.1 (a) is replaced with paragraph 2.1 (a) of ASME Code Case N-638-11, which has been unconditionally approved by the NRC.

PNP 2025-059 Page 1 of 10 ATTACHMENT 5 PROPOSED CHANGES TO ASME CODE, SECTION XI, APPENDIX VIII FOR COMPATIBILITY WITH THE PERFORMANCE DEMONSTRATION INITIATIVE (PDI)

PROGRAM

PNP 2025-059 Page 2 of 10 Supplement 11 - Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds 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 specimens having different nominal pipe diameters and overlay thicknesses. They shall include the minimum and maximum nominal pipe diameters for which the examination procedure is applicable. Pipe diameters within a range of 0.9 to 1.5 times a nominal diameter shall be considered equivalent. If the procedure is applicable to pipe diameters of 24-inch or larger, the specimen set must include at least one specimen 24-inch or larger but need not include 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) Flaw Conditions (1) Base metal flaws. All flaws must be cracks in or near the approximate butt weld heat-affected zone, open to the inside surface, and extending at least 75 percent through the base metal wall.

Flaws may extend 100 percent through the base metal and into the overlay material; in this case, intentional overlay fabrication flaws shall not interfere with ultrasonic detection or characterization of the cracking. Specimens containing IGSCC shall be used when available.

PDI Program: The Proposed Alternative to Supplement 11 Requirements 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.

Alternative: (b) The specimen set shall include specimens with overlays not thicker than 0.1 inch more than the minimum thickness, nor thinner than 0.25 inch of the maximum nominal overlay thickness for which the examination procedure is applicable.

Basis: To avoid confusion, the overlay thickness tolerance contained in the last sentence was reworded and the phrase "and the remainder shall be alternative flaws" was added to the next to last sentence in paragraph 1.1(d)(1).

Alternative: (1)... must be in or... extending at least 50 percent through... intentional overlay fabrication flaws shall not interfere with ultrasonic detection or characterization of the base metal flaws. Specimens containing intergranular stress corrosion cracking shall be used when available.

At least 70 percent of the flaws in the detection and sizing tests shall be cracks and the remainder shall be alternative flaws. Alternative flaw mechanisms, if used, shall provide crack-like reflective characteristics and shall be limited by the following:

PNP 2025-059 Page 3 of 10 Supplement 11 - Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds PDI Program: The Proposed Alternative to Supplement 11 Requirements (a) The use of alternative flaws shall be limited to 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 PD/ 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. To avoid confusion, the overlay thickness tolerance contained in paragraph

1. 1 (b) last sentence, was reworded and the phrase "and the remainder shall be alternative flaws" was added to the next to last sentence.

Paragraph 1. 1 (d)(1) includes the statement that intentional overlay fabrication flaws shall not interfere with ultrasonic detection or characterization of the base metal flaws.

Additionally, 1.1(d)(1) was revised to state that flaws must extend at least 50 percent through the base metal wall. This allows qualification to take advantage of additional test specimens to demonstrate increased examination depth.

PNP 2025-059 Page 4 of 10 Supplement 11 - Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds (e) Detection Specimens (1) At least 20 percent but less than 40 percent of the flaws shall be oriented within +/-20° of the pipe axial direction. The remainder shall be oriented circumferentially. Flaws shall not be open to any surface to which the candidate has physical or visual access. The rules of IWA-3300 shall be used to determine whether closely spaced flaws should be treated as single or multiple flaws.

(2) Specimens shall be divided into base and overlay grading units. Each specimen shall contain one or both types of grading units.

PDI Program: The Proposed Alternative to Supplement 11 Requirements Alternative: (1) At least 20 percent but less than 40 percent of the base metal flaws shall be oriented within +/-20 degrees of the pipe axial direction. The remainder shall be oriented circumferentially. Flaws shall not be open to any surface to which the candidate has physical or visual access.

Basis: The requirement for axially oriented overlay fabrication flaws was excluded from the POI 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 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.

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

PNP 2025-059 Page 5 of 10 Supplement 11 - Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds (a)(1) A base grading unit shall include at least 3 inch of the length of the overlaid weld. The base grading unit includes the outer 25 percent of the overlaid weld and base metal on both sides. The base grading unit shall not include the inner 75 percent of the overlaid weld and base metal overlay material, or base metal-to-overlay interface.

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

(a)(3) When a base grading unit is designed to be unflawed, at least 1 inch of unflawed overlaid weld and base metal shall exist on either side of the base grading unit. The segment of weld length used in one base grading unit shall not be used in another base grading unit. Base grading units need not be uniformly spaced around the specimen.

PDI Program: The Proposed Alternative to Supplement 11 Requirements Alternative: (a)(1) A base metal grading unit includes the overlay material and the outer 50 percent of the original overlaid weld. The base metal grading unit shall extend circumferentially for at least 1 inch and shall start at the weld centerline and be wide enough in the axial direction to encompass one half of the original weld crown and a minimum of 0.50 inch of the adjacent base material.

Basis: The phrase "and base metal on both sides," was inadvertently included in the description of a base metal grading unit. The POI program intentionally excludes this requirement because some of the qualification samples include flaws on both sides of the weld. To avoid confusion several instances of the term "cracks" or "cracking" were changed to the term "flaws" because of the use of alternative Flaw mechanisms. Modified to require that a base metal grading unit include at least 1 inch of the length of the overlaid weld, rather than 3 inches.

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

Basis: Substituted terms provide clarification and are consistent with 1d(1) above. The POI program adjusts for this conservative change for excluding this type grading unit.

Alternative: (a)(3) Sufficient unflawed overlaid weld and base metal shall exist on all sides of the grading unit to preclude interfering reflections from adjacent flaws.

Basis: Modified to require sufficient unflawed overlaid weld and base metal to exist on all sides of the grading unit to preclude interfering reflections from adjacent flaws, rather than the 1 inch requirement.

PNP 2025-059 Page 6 of 10 Supplement 11 - Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds (b)(1) An overlay grading unit shall include the overlay material and the base metal-to-overlay interface of at least 6 in2. The overlay grading unit shall be rectangular, with minimum dimensions of 2 inches.

(b)(2) An overlay grading unit designed to be unflawed shall be surrounded by unflawed overlay material and unflawed base metal-to-overlay interface for at least 1 inch around its entire perimeter. The specific area used in one overlay grading unit shall not be used in another overlay grading unit. Overlay grading units need not be spaced uniformly about the specimen.

PDI Program: The Proposed Alternative to Supplement 11 Requirements Alternative: (b)(1) An overlay fabrication grading unit shall include the overlay material and the base metal-to-overlay interface for a length of at least 1 inch Basis: The POI program reduces the base meta/-

to-overlay interface to at least 1 inch (in lieu of a minimum of 2 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 NRG Generic Letter 88-01. This criterion may be more challenging than the ASME Code because of the variability associated with the shape of the grading unit.

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

Basis: 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.

PNP 2025-059 Page 7 of 10 Supplement 11 - Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds (b)(3) Detection sets shall be selected from Table VIII-S2-1. The minimum detection sample set is five flawed base grading units, ten unflawed base grading units, five flawed overlay grading units, and ten unflawed overlay grading units. For each type of grading unit, the set shall contain at least twice as many unflawed as flawed grading units.

(f) Sizing Specimen (3) Base metal cracking used for length sizing demonstrations shall be oriented circumferentially (4) Depth sizing specimen sets shall include at least two distinct locations where cracking in the base metal extends into the overlay material by at least 0.1 inch in the through-wall direction.

PDI Program: The Proposed Alternative to Supplement 11 Requirements Alternative: Base metal grading units, ten unflawed base metal grading units, five flawed overlay fabrication grading units, and ten unflawed overlay fabrication grading units. For each type of grading unit, the set shall contain at least twice as many unflawed as flawed grading units. For initial 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 guidance for initial procedure qualifications versus qualifying new values of essential variables.

Alternative: (1) The... least 40 percent of the flaws shall be open to the inside surface. Sizing sets shall contain a distribution of flaw dimensions to assess 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 1. 1 (d)(1) above.

Alternative: (3) Base metal flaws used... circumferentially.

Basis: Clarified wording to be consistent with 1.1(d)(1) above.

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

Basis: Clarified wording to be consistent with 1.1(d)(1) above.

PNP 2025-059 Page 8 of 10 Supplement 11 - Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds 2.0 Conduct of Performance Demonstration The specimen inside surface and identification shall be concealed from the candidate. All examinations shall be completed prior to grading the results and presenting the results to the candidate.

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

2.1 Detection Test.

Flawed and unflawed grading units shall be randomly mixed. Although the boundaries of specific grading units shall not be revealed to the candidate, the candidate shall be made aware of 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 shall estimate the length of that part of the flaw that is in the outer 25 percent of the base wall thickness.

2.3 Depth Sizing Test.

For the depth sizing test, 80 percent of the flaws shall be sized at a specific location on the surface of the specimen identified to the candidate. For the remaining flaws, the regions of each specimen containing a flaw to be sized shall be identified to the candidate. The candidate shall determine the maximum depth of the flaw in each region.

PDI Program: The Proposed Alternative to Supplement 11 Requirements Alternative: The specimen... prohibited. The overlay fabrication flaw test and the base metal flaw test may be performed separately.

Basis: Clarified wording to describe process.

Alternative: Flawed... (i.e., base metal or overlay fabrication)... each specimen.

Basis: Clarified wording similar to 1. 1 (e)(2) above.

Alternative: (d) For... base metal grading... 50 percent of the base metal wall thickness.

Basis: Clarified wording for consistency and to be consistent with 1.1(d)(1) above.

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

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

PNP 2025-059 Page 9 of 10 Supplement 11 - Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds 3.0 ACCEPTANCE CRITERIA 3.1 Detection Acceptance Criteria Examination procedures, equipment, and personnel are qualified for detection when the results of the performance demonstration satisfy the acceptance criteria of Table VIII-S2-1 for both detection and false calls. The criteria shall be satisfied separately by the demonstration results for base grading units and for overlay grading units.

3.2 Sizing Acceptance Criteria (a) The RMS error of the flaw length measurements, as compared to the true flaw lengths, is less than or equal to 0. 75 inch. The length of base metal cracking is measured at the 75 percent through-base-metal position.

PDI Program: The Proposed Alternative to Supplement 11 Requirements (c) For a separate depth sizing test, the regions of each specimen containing a flaw to be sized shall be identified to the candidate. The candidate shall determine the maximum depth of the flaw in each region.

Basis: Clarified wording to better describe process.

Alternative: Examination procedures are qualified for detection when:

(a) All flaws within the scope of the procedure are detected and the results of the performance demonstration satisfy the acceptance criteria of Table VIII-S2-1 for false calls.

(b) At least one successful personnel demonstration 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 VIII-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.

Alternative: (a) The... base metal flaws is... 50 percent through-base-metal position.

Basis: Clarified wording to be consistent with 1.1(d)(1) above.

PNP 2025-059 Page 10 of 10 Supplement 11 - Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds (b) All extensions of base metal cracking into the overlay material by at least 0.1 inch are reported as being intrusions into the overlay material.

PDI Program: The Proposed Alternative to Supplement 11 Requirements Alternative: This requirement is omitted.

Basis: The requirement for reporting all extensions of cracking into the overlay is omitted from the POI 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.

PNP 2025-059 Page 1 of 5 ATTACHMENT 6 TECHNICAL BASIS FOR THE INCLUSION OF 28% CHROMIUM NICKEL-BASED FILLER METALS IN ASME CODE CASE N-770-X

PNP 2025-059 Page 2 of 5 1.0 Purpose Provide a technical basis to the inclusion of ERNiCrFe-13 filler material to the list of acceptable filler materials in N-770-X.

2.0 Executive Summary Code Case N-770-8 provides for alternative examination requirements for Alloy 82/182 welds with or without mitigation activities. These requirements affect the method (volumetric, visual, and/or surface), extent and frequency of inservice examinations as well as the preservice baseline examination. Per 1210 (b), these examination requirements only apply to mitigation activities involving welding (full structural overlay, onlay, etc.) that utilize Alloy 52 (UNS 06052, SFA-5.14, ERNiCrFe-7), Alloy 152 (UNS W86152, SFA 5.11, ENiCrFe-7) and Alloy 52M (UNS N06054, SFA-5.14, ERNiCrFe-7A) filler materials. Exceptional corrosion-resistance performance has been reported for all Alloy 52 type filler materials that utilize alloy content greater than 28% Chromium. Given this proof of performance and established standard of 28% Chromium for resistance to Stress Corrosion Cracking, it is appropriate to include other 28% Chromium bearing nickel-based filler materials in the list of Alloy 52 materials in code case N-770-X.

3.0 Introduction This white paper has the objective of establishing the technical basis for inclusion of all Alloy 52 variants (28% Chromium nickel-based filler wire) into Code Case N-770, which modifies the Section XI inspection requirements for Class 1 PWR piping and vessel nozzle butt welds fabricated with Alloy 82/182 material.

4.0 Scope of N-770-8 Code Case N-770-8, "Alternative Examination Requirements and Acceptance Standards for Class 1 PWR Piping and Vessel Nozzle Butt Welds Fabricated With UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of Listed Mitigation ActivitiesSection XI, Division 1," provides alternative examination requirements and acceptance standards for volumetric examination, surface examination and visual examination of pressure containing Class 1 PWR piping and nozzle butt welds fabricated with Alloy 82/182 (UNS N06082/W86182) materials, with or without application of mitigation activities.

5.0 Brief Technical Background on SCC in Alloy 600/690 and Associated Weld Fillers Stress corrosion cracking (SCC) has been a significant degradation mechanism for Alloy 600 and its associated weld metals (Alloy 82/182) in primary water environments of pressurized water reactors (PWRs). The low chromium content (~15-20 wt%) in Alloy 600 and its weld metals has been identified as a key contributor to susceptibility to SCC, especially in high-temperature, high-pressure, hydrogenated water environments where aggressive oxidation can occur along grain boundaries.

PNP 2025-059 Page 3 of 5 In contrast, Alloy 690, with a chromium content of approximately 30 wt%, has demonstrated excellent resistance to SCC, attributed to the formation of a stable, protective Cr20 3 passive film on the alloy surface. This performance has prompted a shift toward the use of high-chromium nickel-base filler metals, such as Alloy 52 and its variants, for structural overlays and new welds on components originally fabricated with Alloy 600 or 82/182.

The associated filler metals Alloy 52 (ERNiFeCr-7), 52M (ERNiFeCr-?A), and 52MSS (ERNiFeCr-13) were developed to match the corrosion performance of Alloy 690. Alloy 52 variants typically contain greater than 28 wt% chromium, significantly improving their resistance to sec and corrosion fatigue in PWR primary water.

6.0 Background on the Development of New Alloy 52 Variants Alloy 52 and its derivatives have evolved over the past two decades in response to performance needs related to fabrication and in-service conditions. While Alloy 52 has always provided strong resistance to SCC, weldability issues such as solidification cracking and ductility dip cracking (DOC) prompted further development.

Alloy 52M was introduced with optimized trace element controls and minor composition shifts to reduce susceptibility to DOC, especially in multi-pass welding over stainless steel base materials. Subsequent developments, including 52MSS and 52MSS-Ta, have further improved weldability by adjusting elements such as niobium, tantalum and molybdenum. The core design principle across all these variants remains the retention of high chromium content (~28%) to ensure PWR-relevant SCC resistance.

7.0 Technical Justification For The Inclusion Of ERNiCrFe-13 (Alloy 52MSS) Into N-770-X Based On Chemistry The principal justification for inclusion of additional Alloy 52 variants lies in the chromium threshold for SCC resistance. Extensive research, including NUREG/CR-7103 and EPRI test data, demonstrates that a minimum bulk chromium content of 28 wt% in nickel-based weld metal is critical for suppressing intergranular SCC in simulated PWR primary water. From NUREG/CR-7103: "The main conclusion from these experiments on alloy 152, 152M, 52, 52M and 52MSS weld metals with typical Cr bulk concentrations (28-30 wt%) is that they are resistant to SCC crack growth. " From the NUREG/CR-7103 report, the following plot is given which demonstrates the performance of Alloy 52 MSS (ERNiCrFe-13) alongside other Alloy 52 variants.

PNP 2025-059 Page 4 of 5 10 cn e 10-7 E

Qf...

la a:

.c i 0 10*5 a..

C, 0 u en "C

cu..

, 10-9 en la Q)

~

1 o-10 MRP-55 Alloy 182 325°C 75%

~

(f)

)

.A.

20 30 40

~ Alloy 152 A

.A.

Alloy 52 B Iii...

lloy 152M A Alloy 52 A Alloy 52 B Alloy 52M A Giil Alloy 52M 1

~ Alloy 52M 82 I] Alloy 52M B3 (I) Alloy 52MSS MRP-55 6

GEG 152 B GEG 152 D

<I GEG 152 E

~

GEG 152 F T

GEG 152 G

~

.... GEG 152 A T

~ GEG 152 B

~

GEG 52 B

~

GEG 52C GEG 52 D GEG 52M C 50 60 Stress Intensity, MPa m Additional work performed by EPRl's Welding and Repair Technology Center provides additional data points for sec crack growth rates in recent heats of ERNiCrFe-13:

Summary of sec Crack Growth Rates; 52M, 52MSS-0Fe, 52XL, 52MSS-Ta 52M, Special Metals NX7206TK 52MSS-0Fe, Special Metals HV1500 EPRI 52XL, Kobelco S2768 52MSS-Ta, Special Metals NV1673 52MSS-Ta, Special Metals VX131WXW 52MSS-Ta, Special Metals VX135WXW CGR(mtn/sJ 4.0 X l0-lO 1.0 X 10-8 3.5 X 10-9 1.3 X 10-9 7.8 X l0*lO ~o 2.0 X 10*10 1.5 X 10*8 4.0 X 10*10 1.6 X 10*9 5.0 X l0*lO 1. 7 X 10-9

PNP 2025-059 Page 5 of 5 Chromium enhances the formation of a stable, adherent oxide film that impedes localized oxidation and crack initiation along grain boundaries. All known Alloy 52 variants-including 52M, 52MSS, and 52MSS-Ta-meet or exceed this threshold and share comparable electrochemical and sec resistance characteristics in autoclave and corrosion-fatigue tests.

Alloy developments intended to resist weldability issues have not been shown to decrease their corrosion performance.

Additionally, the Materials Reliability Program (MRP) MRP-169, Technical Basis for Preemptive Weld Overlays for Ally 82/182 Butt Welds in PWRs, provides additional basis for the performance of a number of 28% chromium bearing nickel based alloys.

As Code Case N-770-8 currently restricts the list of acceptable mitigation fillers to only three named designations, the exclusion of ERNiCrFe-13 which meets the same metallurgical performance targets constitutes an unnecessary limitation.

8.0 Conclusion Stress corrosion cracking mitigation in Alloy 82/182 welds is a critical issue for the long-term reliability of Class 1 pressure boundary components in PWRs. The effectiveness of mitigation depends largely on the corrosion resistance of the deposited weld metal. As demonstrated by the body of research cited, ERNiCrFe-13 which contains ~28 wt% Chromium provides superior resistance to SCC due to its enhanced passivity and resistance to grain boundary oxidation in PWR primary environments. Inclusion of this material classification into Code Case N-770-X will ensure the reliable corrosion performance expected out of Alloy 52, with the added benefit of modern weldability improvements which will serve to decrease outage lengths by increasing the frequency of first-time quality for welds and weld overlays in the field.

9.0 Reference Documents ASME Code Case N-770-8 NUREG/CR-7103 Vol. 4, Pacific Northwest National Laboratory, 2019 EPRI WRTC TAC Meeting, June 2024, RFA-1 Material Weldability and Welding Alloy Development Liang, H. C., Wang, C. J., & Wu, Z. W. (2021 ). Corrosion behavior of alloy 52M and 52MSS weld surfacing. International Journal of Pressure Vessels and Piping, 191, 104356.

Andresen, P. L., Morra, M. M., & Ahluwalia, K. (2016). SCC of Alloy 690 and its Weld Metals. In Proceedings of the 15th International Conference on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors (pp. 161-178).

Materials Reliability Program (MRP) MRP-169, Technical Basis for Preemptive Weld Overlays for Alloy 82/182 Butt Welds in PWRs

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PNP 2025-059, Relief Request Number RR 5-12, Proposed Alternative to ASME Section XI Code for Full Structural Weld Overlays of Primary Coolant System Hot Leg, Cold Leg, and Pressurizer Nozzle Dissimilar Metal Welds

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