ML25352A332
| ML25352A332 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 12/22/2025 |
| From: | Marlayna Vaaler Doell Plant Licensing Branch III |
| To: | Holtec Palisades |
| Wall S | |
| References | |
| EPID L-2025-LLR-0080, RR 5-12 | |
| Download: ML25352A332 (0) | |
Text
December 22, 2025 PALISADES NUCLEAR PLANT - AUTHORIZATION AND SAFETY EVALUATION FOR ALTERNATIVE REQUEST NO. RR 5-12 (EPID L-2025-LLR-0080)
LICENSEE INFORMATION Recipients Name and Address:
Site Vice President Palisades Energy, LLC Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043-9530 Licensee:
Holtec Palisades, LLC Plant Name:
Palisades Nuclear Plant Docket No.:
50-255 APPLICATION INFORMATION Submittal Date: August 20, 2025 Submittal Agencywide Documents Access and Management System (ADAMS) Accession No.: ML25232A195 Supplement Dates: September 16, 2025; November 26, 2025 Supplement ADAMS Accession Nos.: ML25260A638; ML25330A180, package Applicable Inservice Inspection (ISI) or Inservice Testing (IST) Program Interval and Interval Start/End Dates: The fifth ISI interval began on December 13, 2015, and is scheduled to end on December 12, 2025.
Alternative Provision: The licensee requested an alternative under Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(z)(1).
American Society of Mechanical Engineers (ASME) Code,Section XI, IWA-4411 regarding the compliance of welding repair/replacement activities in accordance with the original Construction Code.
ASME Code Section XI, Appendix VIII, Supplement 11 that provides qualification requirements for ultrasonic (UT) examination of full structural weld overlays (FSWOLs).
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, Paragraph -1210(b) that lists ERNiCrFe-7, 152ENiCrFe-7, and ERNiCrFe-7A filler materials (Alloy 52, Alloy 152 and Alloy 52M filler metals, respectively) for mitigating piping nozzle butt welds fabricated with Alloy 82/182 material.
Applicable Code Edition and Addenda: The Palisades code of record for the fifth ISI interval is the 2007 Edition with 2008 addenda of the ASME Code,Section XI.
Brief Description of the Proposed Alternative: The edition and addenda of the ASME Code,Section XI applicable to the Palisades Nuclear Plant (PNP) does not contain requirements for FSWOLs for dissimilar metal welds (DMWs). However, DMW FSWOLs have been applied to other primary coolant system (PCS) nozzle DMWs in the pressurized water reactor (PWR) industry using alternative approaches. The licensee (Holtec Palisades, LLC) proposes to use the methodology of 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, for application of FSWOLs to the PCS hot leg, cold leg, and pressurizer nozzle DMWs identified in Section 1.0 of of the licensees request letter dated August 20, 2025. Since ASME Code Case N-740-2 has not been approved by the NRC in the latest revision (Revision 21) of Regulatory Guide (RG) 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1, a proposed alternative needs to be approved before the installation and use of the FSWOLs.
The licensee also proposed to use ASME Code Case N-770-7 in the preservice and inservice inspections for the FSWOLs that will be fabricated with Alloy 52MSS. In comparison, ASME Code Case N-770-7 does not include Alloy 52MSS as a nickel-based alloy resistant to primary water stress corrosion cracking (PWSCC). Therefore, as an alternative to N-770-7, the licensee identified the use of Alloy 52MSS as a PWSCC-resistant alloy.
For additional details on the licensees request, please refer to the documents located at the ADAMS Accession Nos. identified above.
REGULATORY EVALUATION Regulatory Basis: 10 CFR 50.55a(z)(1)
The NRC regulations in 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state the following:
Alternatives to the requirements of paragraphs (b) through (h) of this section
[10 CFR 50.55a] or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation. The licensee must demonstrate that its request meets one of two criteria: (1) the proposed alternative would provide an acceptable level of quality and safety in accordance with paragraph (z)(1); or (2) compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety in accordance with paragraph (z)(2).
The licensee submitted its request on the basis that the proposed alternative would provide an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1). Based on the above regulations, the NRC staff concludes that regulatory authority exists to authorize an alternative to ASME Code,Section XI and Code Case N-770-7, as requested by the licensee.
TECHNICAL EVALUATION 1.0 GENERAL DISCUSSION The licensee explained that PNP ceased operation in spring 2022 and that it is performing modifications to PNP to support the restart of plant operations. The licensee also indicated that it is planning to apply FSWOLs on the hot leg, cold leg, and pressurizer nozzle DMWs using PWSCC-resistant Alloy 52M (ERNiCrFe-7A) and Alloy 52MSS (ERNiCrFe-13) filler metals. In addition, the licensee explained that the installation and use of the FSWOLs, along with the inspection activities, will continue to ensure the structural integrity of the associated nozzles and piping.
As identified in Section 1.0 of Attachment 1 of the licensees request letter dated August 20, 2025, the scope of the proposed alternative includes the DMWs of the following hot leg, cold leg, and pressurizer nozzles: (1) hot leg surge nozzle; (2) hot leg shutdown cooling nozzle; (3) cold leg safety injection nozzles (four nozzles); (4) pressurizer surge nozzle; and (5) pressurizer power operated relief valve (PORV) nozzle. Except for the pressurizer PORV nozzle, the size of these nozzles is nominal pipe size (NPS) 12 schedule 140. The size of the pressurizer PORV nozzle is NPS 4 schedule 120.
The overall approach of the proposed alternative is described in Attachment 1 of the licensees request letter. The licensee proposed to design and install the FSWOLs in accordance with ASME Code Case N-740-2 with some modifications (e.g., use of Alloy 52MSS). The licensee indicated that ASME Code Case N-740-2 has not been approved by the NRC in the latest revision (Revision 21) of RG 1.147 that addresses acceptable Code Cases with NRC staff-mandated conditions as necessary. In addition, ASME Code Case N-770-7, which is incorporated by reference in 10 CFR 50.55a, Codes and standards, does not include Alloy 52MSS as a PWSCC-resistant nickel-based weld material. Accordingly, the licensee submitted the proposed alternative for NRC staff review and approval before the installation and use of the FSWOLs.
The NRC staffs safety evaluation of the proposed alternative is documented below. This safety evaluation is not intended to generically approve the provisions in ASME Code Case N-740-2 for the use of FSWOLs.
2.0 WELD OVERLAY DESIGN AND ANALYSES Weld Overlay Sizing Analyses The licensee indicated that the FSWOLs will extend around the full circumference of the DMWs and that the length of each weld overlay is sufficient to allow 100 percent coverage for the preservice and inservice examinations. The licensee also explained that the length, thickness and geometry of each weld overlay are sufficient to meet the structural requirements of ASME Code Case N-740-2.
The licensee explained that the weld overlay sizing is based on the limiting case of the following in relation to the postulation of a flaw in the existing base and weld materials: (a) 100 percent through-wall circumferential flaw for the entire circumference and (b) 100 percent through-wall axial flaw with a length of 1.5 inches or the combined width of the weld plus buttering plus any stress corrosion cracking (SCC) susceptible material, whichever is greater. This approach is described in Attachment 4 of the licensees request letter.
The NRC staff finds that the licensees weld overlay sizing analyses are acceptable because (1) the sizing analyses conservatively assume the 100 percent through-wall full circumferential (360 degree) flaw and the 100 percent through-wall axial flaw with the length covering SCC-susceptible materials in the existing base and weld materials and (2) the sizing analyses select the greater thickness for the weld overlays based on the limiting case of the flaw assumptions for the circumferential and axial flaw orientations.
In addition, the licensee also indicated that the cumulative usage factor (CUF) values of the FSWOLs and associated nozzles and components do not exceed the fatigue design limit of 1.0 for the current license term. The NRC staff finds that the CUF analyses are acceptable because the CUF values meet the fatigue design limit of 1.0 for the current license term.
Weld Residual Stress Analyses The licensee performed finite element weld residual stress (WRS) analyses for the Alloy 82/182 welds of the nozzles that are mitigated by the weld overlay installation process. The purpose of the analyses is to estimate the WRS after welding and operating (heat-up/cool-down) cycles.
The licensee indicated that the WRS analyses included the simulation of the nozzle butter weld, the Alloy 82/182 weld attaching the nozzle to the safe end, the dissimilar metal weld attaching the safe end to the associated piping or component as applicable, and the proposed weld overlay.
The licensee indicated that the residual stresses are simulated using validated thermoplastic finite element methods and are used as part of the applied stresses in the ASME Code,Section XI, Appendix C crack growth analyses. The licensee also indicated that the transient thermal analyses employ temperature-dependent material properties and heat inputs representative of the actual weld parameters to generate the temperature history during welding. In addition, the licensee explained that the resulting temperature history from the thermal analysis is then used as input to the multi-pass weld deposition in the subsequent structural analysis to predict the residual stress distribution in the welded components.
With respect to the WRS analysis approach, the licensee indicated that the finite element welding simulation procedure is consistent with the recommendations of industry WRS modeling guidance documents such as MRP-317, Revision 1, Materials Reliability Program: Welding Residual Stress Dissimilar Metal Butt-Weld Finite Element Modeling Handbook (MRP-317, Revision 1). and MRP-287, Materials Reliability Program: Primary Water Stress Corrosion Cracking (PWSCC) Flaw Evaluation Guidance (MRP-287).
In addition, the licensee explained that, for WRS simulation validation purpose, Framatome (formerly known as AREVA NP Inc.), who performed the WRS analyses for the proposed alternative, participated in the finite element round robin study coordinated by the NRC, as documented in NUREG-2228, Weld Residual Stress Finite Element Analysis Validation Part II
- Proposed Validation Procedure, Final Report. The licensee indicated that NUREG-2228 provided finite element modeling guidance aimed at reducing analyst-to-analyst scatter. The licensee also explained that participation in the NUREG-2228 round robin study demonstrated that the WRS prediction capability of Framatome's weld simulation procedure is consistent with the prediction capabilities of other participants and that the WRS simulation procedure of Framatome follows the industry recommended practices.
The NRC staff finds that the WRS analyses are acceptable because (1) the analysis approach is consistent with the recommendations in the industry guidance documents such as MRP-317, Revision 1, and MRP-287, (2) Framatome, who performed the WRS analyses, participated in the round robin study documented in NUREG-2228, and (3) the study results in NUREG-2228 demonstrate that the analysis approach of Framatome generates the analysis results in agreement with those of other industry participants and measurement data (e.g., contour measurement data).
Crack Growth Analyses The licensee postulated inside surface-connected axial and circumferential flaws in the crack growth analyses. For these postulated flaws, the length of the semi-elliptical axial flaw was assumed to be 1.5 inches or the combined width of the weld plus buttering plus any adjacent SCC-susceptible material, whichever is greater. In addition, the length of the circumferential flaw was assumed to be 360 degrees (i.e., assumption of a full circumferential flaw). The NRC staff finds that the licensees approach for postulating the flaw length is acceptable because the approach conservatively assumes the axial and circumferential flaw lengths based on the consideration of the material susceptibility to SCC.
With respect to the postulated flaw depth, a 100 percent through-wall axial flaw and a 100 percent through-wall 360-degree circumferential flaw were assumed for the FSWOLs on the NPS 12 nozzles (i.e., all the nozzles within the scope of the proposed alternative except the pressurizer PORV nozzle). For the pressurizer PORV nozzle (NPS 4), a 75 percent through-wall axial flaw with the length discussed above and a 75 percent through-wall 360-degree circumferential flaw were assumed in the crack growth analyses.
The NRC staff finds the licensees postulation of the flaw depth in the crack growth analyses acceptable because the approach assumes a conservative flaw depth of at least 75 percent original wall thickness, which corresponds to the maximum allowable flaw depth described in ASME Code,Section XI, IWB-3640 and Appendix C.
The licensee also indicated that the crack growth analyses included crack growth due to fatigue and PWSCC. The NRC staff finds that the crack growth analyses considered relevant degradation mechanisms and, therefore, the licensees approach is acceptable in terms of the evaluated mechanisms of crack growth.
With respect to the evaluated loads, the licensee indicated that the crack growth analyses considered stresses associated with transient cycles, weld residual stresses, and sustained stresses due to pipe external loads, pressure, and thermal stratification loads as applicable. The NRC staff finds that the crack growth analyses considered relevant cyclic and sustained stresses and, therefore, the licensees approach for identifying and evaluating applicable loads are acceptable.
In addition, the crack growth analyses were performed in accordance with ASME Code,Section XI, Appendix C and determined the plant operating period that meets the acceptance criteria in ASME Code,Section XI, Appendix C. The plant operating period determined in the crack growth analyses is also called the design life or mitigation evaluation period of the weld overlay in relation to the use of ASME Code Cases N-740-2 and N-770-7.
As discussed above, the NRC staff finds that the crack growth analyses are acceptable because (1) the initial flaws postulated in the crack growth analyses are conservative (e.g., postulation of a 360 degree full circumferential flaw with a depth of at least 75 percent original wall thickness) and (2) the analyses were performed in accordance with the provisions of ASME Code,Section XI, Appendix C that address relevant procedures and acceptance criteria for analytical evaluations of flaws. Accordingly, the NRC staff finds that the crack growth analysis results including the design life of the weld overlay are acceptable to be used as the input to the licensees inservice inspections that will be performed in accordance with ASME Code Case N-770-7, as incorporated by reference in 10 CFR 50.55a.
3.0 NONDESTRUCTIVE EXAMINATION UT Examination Procedure and Personnel Qualification The licensee indicated that as part of the design of the weld overlay, the weld overlay length, surface finish, and flatness are specified to allow for post-overlay, qualified ASME Code,Section XI, Appendix VIII UT examinations, as implemented through the Electric Power Research Institute (EPRI) Performance Demonstration Initiative (PDI) Program. The licensee also explained that 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. The licensee further indicated that construction flaws are included in the PDI qualification sample sets to evaluate examination procedures and personnel.
In addition, the licensee explained that the procedure and personnel for the post-overlay, preservice and inservice UT examinations for the weld overlays will be qualified in accordance with ASME Code,Section XI, Appendix VIII, Supplement 11 with some modifications. of the licensees request letter describes these modifications to the Appendix VIII, Supplement 11 requirements for the UT procedure and personnel qualification as well as their basis. The NRC staff has determined that the alternative method used by the PDI program described in Attachment 5 of the licensees request letter is of equivalent rigor to the ASME Code requirements. The NRC staff expects that the personnel, procedure and equipment that pass the PDI program will be able to detect the flaws of interest in examinations.
Post-overlay Examination In relation to the post-overlay examination (also called post-installation examination), the licensee indicated that ASME Code,Section XI has specific acceptance criteria and evaluation methodology to be used with the results from the UT examinations. The licensee also explained that the acceptance criteria consider the materials in which the flaw indications are detected, the orientation and size of the indications and their potential structural effects on the component.
The licensee further indicated the acceptance criteria include allowable planar flaws per ASME Code,Section XI, Table IWB-3514-1 and allowable laminar flaws per ASME Code,Section XI, Table IWB-3514-3.
The NRC staff finds that the licensees approach for post-overlay UT examination is acceptable because (1) the acceptance criteria for the examination include those specified for planar and laminar flaws in ASME Code,Section XI and (2) the UT examination procedure and personnel qualification based on Section XI, Appendix VIII provisions with the licensees modifications are adequate to ensure appropriate volumetric examination as discussed above.
With respect to the post-overlay surface examination, the licensee indicated that the weld overlay and the adjacent base material for at least 0.5 inches from each side of the overlay are required to be examined using the liquid penetrant method. The licensee also indicated that the weld overlay is required to satisfy the surface examination acceptance criteria for welds of ASME Code,Section III, NB-5300 and that the adjacent base material will satisfy the surface examination acceptance criteria for base material of ASME Code,Section III, NB-2500.
The NRC staff finds that the post-overlay surface examination is acceptable because the surface examination covers a sufficient area of the weld overlay including the adjacent base material and the surface examination uses the relevant acceptance criteria specified in ASME Code,Section III.
In its supplement dated November 26, 2025 (ML25330A180, package), the licensee explained that the post-overlay examinations of the FSWOLs revealed rejectable indications due to interbead lack of fusion in the FSWOL for the hot leg surge nozzle, such that local weld repairs were performed to remove these indications or to reduce the indications to acceptable sizes.
The licensee also confirmed that a final acceptance UT examination performed after the local weld repairs did not reveal any unacceptable indications. The NRC staff finds that the examination results are acceptable because they confirmed the absence of rejectable indications.
Preservice and Inservice Examinations In its supplement dated November 26, 2025, the licensee clarified that the preservice examinations (also called preservice inspections) were performed on the FSWOLs in accordance with the augmented examination requirements of ASME Code Case N-770-5, which was incorporated by reference in 10 CFR 50.55a, published in the Federal Register (FR) on October 27, 2022 (87 FR 65128). The licensee further indicated that the preservice inspections confirmed the absence of unacceptable indications in the FSWOLs and the associated weld and base materials.
The NRC staff finds that the licensees preservice inspections in accordance with ASME Code Case N-770-5 is acceptable because (1) even though ASME Code Case N-770-7 was incorporated by reference in the most recent version of 10 CFR 50.55a (89 FR 70449, published August 24, 2024), the preservice inspection approach per Code Case N-770-5 is consistent with that per Code Case N-770-7, (2) a new inspection item for auxiliary head adapter butt welds, B-3, which is created in Code Case N-770-7, is not applicable to the proposed alternative such that this newly created inspection item does not affect the validity of the preservice inspections that the licensee completed in accordance with Code Case N-770-5, and (3) the licensees preservice inspections did not reveal any unacceptable indications.
In addition, the licensee indicated that the inservice inspections of the FSWOLs will be performed in accordance with the augmented inspection requirements of ASME Code Case N-770-7, as incorporated by reference in 10 CFR 50.55a. The licensee also explained that Paragraph -1210(b) of Code Case N-770-7 does not list Alloy 52MSS as a mitigative weld filler material for piping nozzle butt welds fabricated with Alloy 82/182 materials. Therefore, the licensee requested approval for using Code Case N-770-7 examinations on the FSWOLs consisting of Alloy 52MSS weld metal.
of the licensees request letter describes the basis of identifying Alloy 52MSS as a mitigative weld filler material in the use of ASME Code Case N-770-7. The licensee indicated that the Code Case provides for alternative inspection requirements for Alloy 82/182 welds with or without mitigation activities and that these requirements address the method (volumetric, visual, and/or surface), extent and frequency of inservice examinations and the preservice baseline examination.
The licensee further explained that in accordance with Paragraph -1210(b) of ASME Code Case N-770-7, these inspection requirements apply to the mitigation activities involving welding (full structural weld overlay, onlay, etc.) that utilize Alloy 52, Alloy 152 and Alloy 52M filler materials. In addition, the licensee indicated that exceptional corrosion resistance performance has been reported for all Alloy 52 type filler materials that utilize a chromium (Cr) content greater than 28 weight (wt.) percent. Given this proof of performance and established standard of 28 wt. percent for resistance to SCC, the licensee explained that it is acceptable to include other 28 wt. percent Cr bearing nickel-based filler materials in the list of Alloy 52 materials that retain the resistance to SCC.
The licensee further explained that extensive research, including NUREG/CR-7103 and EPRI test data, demonstrates that a minimum bulk chromium content of 28 wt. percent in nickel-based weld metals is critical for suppressing intergranular SCC in simulated PWR primary water. The licensee also indicated that as discussed in NUREG/CR-7103, the main conclusion from the SCC tests on Alloy 152, 152M, 52, 52M and 52MSS weld metals with typical Cr bulk concentrations of 28 - 30 wt. percent is that these materials are resistant to SCC crack growth.
The NRC staff finds that the licensee provided acceptable justification for inclusion of Alloy 52MSS as a mitigative weld filler metal in the proposed use of ASME Code Case N-770-7 because the nickel-based weld filler metals with 28 wt. percent Cr or greater have insignificant PWSCC crack growth rates compared to the Alloy 82/182 weld filler metals and the SCC crack growth rate data of high Cr nickel-based alloys (e.g., Alloy 152, 152M, 52, 52M and 52MSS materials) support the identification of Alloy 52MSS as a PWSCC-resistant material in the proposed use of Code Case N-770-7.
As discussed above, the NRC staff finds that Alloy 52MSS can be identified as a PWSCC-resistant material in the implementation of the inspection provisions of ASME Code Case N-770-7 based on the resistance of the weld material to PWSCC. The NRC staff also finds that the licensees preservice and inservice inspections are sufficient to ensure the integrity of the FSWOLs, consistent with the inspection requirements specified in 10 CFR 50.55a.
4.0 WELDING The licensee indicated that the installation of FSWOLs within the scope of the proposed alternative is performed using ambient temperature temper bead (ATTB) welding in accordance with Attachment 3 of the licensees request letter based on Appendix I in ASME Code Case N-740-2. The licensee also explained that research on the use of an ATTB welding using the machine gas tungsten arc welding (GTAW) process is documented in EPRI Report GC-111050, Ambient Temperature Preheat for Machine GTAW Temperbead Applications, November 1998. In addition, the licensee indicated that the EPRI report demonstrates that repair welds performed with an ATTB procedure utilizing the machine GTAW process exhibit mechanical properties equivalent to or better than those of the surrounding base material.
The licensee further discussed that, as an alternative to preheat, the ATTB welding process utilizes the tempering effect of the welding procedure to produce tough and ductile microstructures. The licensee indicated that because precise 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. The licensee also explained that, as discussed in 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 and accordingly the desired degree of tempering is achieved with the resulting microstructure being very tough and ductile.
In addition, the licensee indicated that the ASME Code,Section XI, IWA-4600 temper bead process includes a post-weld soak requirement that is performed at 300 degrees Fahrenheit (°F) for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The licensee explained that this post-weld soak is intended to assist diffusion of any remaining hydrogen from the repair weld and, as such, the post-weld soak is a hydrogen bake-out process and not a post-weld heat treatment. The licensee also indicated that at 300°F, the post-weld soak does not stress-relieve, temper, or alter the mechanical properties of the weldment in any manner.
The licensee further explained that the machine GTAW process is inherently free of hydrogen because, 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. The licensee indicated that any moisture on the surface of the component being welded is vaporized ahead of the welding torch and that the GTAW process utilizes dry inert shielding gases that cover the molten weld pool from oxidizing atmospheres. Accordingly, 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.
Therefore, the licensee indicated that the potential for hydrogen-induced cracking is greatly reduced by using the machine GTAW process. Since the potential for hydrogen absorption is greatly diminished using the GTAW process, the licensee determined that no post-weld soak is needed for the proposed alternative to mitigate the potential effect of hydrogen on the integrity of the weld overlays.
The NRC staff finds that the licensees approach using the ATTB welding process is acceptable because (1) the welding process with the application of weld beads can provide a localized heat treatment effect of tempering such that the ductility and toughness of the HAZ are enhanced and (2) the GTAW welding process minimizes the potential adverse effect of hydrogen on the integrity of the HAZ.
The NRC staff also noted that the licensees ATTB welding approach is based on the provisions of Appendix I in ASME Code Case N-740-2 that are in turn taken from ASME Code Case N-638-4, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,Section XI, Division 1. The NRC staff further noted that RG 1.147, Revision 21 identifies two conditions for ASME Code Case N-638-4 as follows:
(1) demonstration for ultrasonic examination of the repaired volume using representative samples that contain construction type flaws and (2) the provisions of Paragraph 3(e)(2) or 3(e)(3) (i.e., determination of the maximum interpass temperature for field applications by using heat flow calculations or measurements on a test coupon) may only be used when it is impractical to use the direct interpass temperature measurement.
The licensee clarified that these two conditions are met in the licensees use of the welding provisions of Appendix I in ASME Code Case N-740-2, as discussed in Attachment 4 of the licensees request letter. Accordingly, the NRC staff finds that the ATTB welding approach of the proposed alternative is reasonable because the licensees approach meets the NRC staff-mandated conditions regarding the demonstration for UT examination and the determination of the interpass temperature in relation to the use of the ATTB welding provisions described in ASME Code Case N-740-2.
In addition, the NRC staff finds that the licensees proposed installation and use of the FSWOLs is acceptable until the end of the current license term ending on March 24, 2031, because the installation of the FSWOLs is not a temporary means to address the susceptibility of the DMWs to PWSCC.
CONCLUSION The NRC staff has determined that the proposed alternative in the licensees request referenced above, as supplemented, would provide an acceptable level of quality and safety.
The NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(1).
The NRC staff authorizes the use of proposed alternative RR 5-12 at the Palisades Nuclear Plant for the remainder of the current license term ending on March 24, 2031.
All other ASME Code,Section XI requirements for which an alternative was not specifically requested and authorized remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributors: S. Min, NRR J. Collins, NRR S. Cumblidge, NRR Date: December 22, 2025 Ilka Berrios, Acting Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation cc: Listserv JUSTIN POOLE Digitally signed by JUSTIN POOLE Date: 2025.12.22 16:04:17 -05'00'
ML25352A332 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DNRL/NPHP/BC NAME MDoell (BBallard for)
SLent MMitchell DATE 12/19/2025 12/22/2025 12/10/2025 OFFICE NRR/DORL/LPL3/BC NRR/DORL/LPL3/PM NAME IBerrios (JPoole for)
MDoell (BBallard for)
DATE 12/22/2025 12/22/2025