ML25230A047
| ML25230A047 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 08/26/2025 |
| From: | Tony Nakanishi Plant Licensing Branch IV |
| To: | Heflin A Arizona Public Service Co |
| Orders, William | |
| References | |
| EPID L?2024?LLR?0080 | |
| Download: ML25230A047 (1) | |
Text
August 26, 2025 Mr. Adam Heflin Executive Vice President/
Chief Nuclear Officer Mail Station 7605 Arizona Public Service Company P.O. Box 52034 Phoenix, AZ 85072-2034
SUBJECT:
PALO VERDE NUCLEAR GENERATING STATION, UNIT 1 - RELIEF REQUEST 73 PROPOSED ALTERNATIVE FOR PRESSURIZER LOWER SHELL TEMPERATURE NOZZLE LIFE OF REPAIR (EPID L-2024-LLR-0080)
Dear Mr. Heflin:
By letter dated December 10, 2024 (Agencywide Documents Access and Management System Accession No. ML24346A110), as supplemented by letter dated March 27, 2025 (ML25086A276), Arizona Public Service Company (the licensee) submitted Relief Request 73 for U.S. Nuclear Regulatory Commission (NRC) review and approval of alternatives to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),
Section XI, 2013 Edition, and ASME Code Case N-638-10, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW [Gas Tungsten Arc Welding] Temper Bead Technique,Section XI, Division 1, dated May 6, 2019, as they relate to the repair and replacement of the weld for the pressurizer lower shell temperature nozzle for Palo Verde Nuclear Generating Station (Palo Verde), Unit 1, for the life of repair.
On October 9, 2023, while performing small nozzle inspections during the Palo Verde, Unit 1 refueling outage, boric acid leakage was found in the area of the weld of the pressurizer lower shell temperature nozzle. Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1) the licensee requested, by letter dated October 23, 2023 (ML23296A254), NRC authorization of Relief Request 70 following the repair and replacement of the weld for the temperature nozzle of the pressurizer lower shell, on the basis that the proposed alternative provided an acceptable level of quality and safety. The NRC staff provided verbal authorization for Relief Request 70 on October 27, 2023 (ML23303A011), and a formal written safety evaluation by letter dated September 9, 2024 (ML24197A199). The authorization for Relief Request 70 was approved for the duration of the Palo Verde, Unit 1, Cycle 25, which concluded in the spring of 2025.
The purpose of Relief Request 73 is to provide the NRC with a proposed alternative to justify continued use of the nozzle repair for the life of Palo Verde, Unit 1, including the initial license extension, which expires June 1, 2045. The NRC staff provided a verbal authorization for the continued operation of Palo Verde, Unit 1, following its spring 2025 outage through Cycle 26 on April 11, 2025 (ML25104A042).
As set forth in the enclosed safety evaluation, the NRC has determined that the proposed alternative weld repair of the pressurizer lower shell temperature nozzle for Palo Verde, Unit 1, provides an acceptable level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all regulatory requirements set forth in 10 CFR 50.55a(z)(1).
Therefore, the NRC authorizes the use of Relief Request 73 at Palo Verde, Unit 1, for the remainder of plant life, through the initial license extension.
All other ASME Code,Section XI requirements for which relief was not specifically requested and authorized in this proposed alternative remain applicable, including third party review by the Authorized Nuclear Inservice Inspector If you have any questions, please contact the Palo Verde Project Manager, William Orders, at 301-415-3329 or by email at William.Orders@nrc.gov.
Sincerely, Tony Nakanishi, Chief Plant Licensing Branch LPL4 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-528,
Enclosure:
Safety Evaluation cc: Listserv TONY NAKANISHI Digitally signed by TONY NAKANISHI Date: 2025.08.26 14:35:29 -04'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST 73 PROPOSED ALTERNATIVE FOR PRESSURIZER LOWER SHELL TEMPERATURE NOZZLE LIFE OF REPAIR ARIZONA PUBLIC SERVICE COMPANY PALO VERDE NUCLEAR GENERATING STATION, UNIT 1 DOCKET NO. 50-528 EPID NO. L-2024-LLR-0080
1.0 INTRODUCTION
By letter dated December 10, 2024 (Agencywide Documents Access Management System Accession No. ML24346A110), and supplemented by letter dated March 27, 2025 (ML25086A276), Arizona Public Service (APS, the licensee) submitted Relief Request 73 for U.S. Nuclear Regulatory Commission (NRC) review and approval of alternatives to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code),Section XI, 2013 Edition, and ASME Code Case N-638-10, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW [Gas Tungsten Arc Welding] Temper Bead Technique,Section XI, Division 1, dated May 6, 2019, as they relate to the repair and replacement of the weld for the pressurizer lower shell temperature nozzle for Palo Verde Nuclear Generating Station (Palo Verde), Unit 1, for the life of repair.
On October 9, 2023, while performing small nozzle inspections during the Palo Verde, Unit 1 refueling outage, boric acid leakage was found in the area of the weld of the pressurizer lower shell temperature nozzle. Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1), Acceptable level of quality and safety, the licensee requested, by letter dated October 23, 2023 (ML23296A254), NRC authorization of Relief Request 70 following the repair and replacement of the weld for the temperature nozzle of the pressurizer lower shell, on the basis that the proposed alternative provided an acceptable level of quality and safety. The NRC staff provided verbal authorization for Relief Request 70 on October 27, 2023 (ML23303A011),
and a formal written safety evaluation (SE) by letter dated September 9, 2024 (ML24197A199).
The authorization for Relief Request 70 was approved for the duration of the Palo Verde, Unit 1 Cycle 25, which concluded in the spring of 2025.
The purpose of Relief Request 73 is to provide the NRC with a proposed alternative to justify continued use of the nozzle repair for the life of Palo Verde, Unit 1, including the initial license extension, which expires June 1, 2045. The NRC staff provided a verbal authorization for the continued operation of Palo Verde, Unit 1, following its spring 2025 outage through Cycle 26 on April 11, 2025 (ML25104A042).
2.0 REGULATORY EVALUATION
Adherence to Section XI of the ASME Code is mandated by 10 CFR 50.55a(g)(4), Inservice inspection standards requirements for operating plants, which states, in part that ASME Code Class 1, 2, and 3 components will meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI.
The regulations in 10 CFR 50.55a(z), Alternative to codes and standards requirements, states:
Alternatives to the requirements of paragraphs (b) through (h) of [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 applicant or licensee must demonstrate that: (1) Acceptable level of quality and safety. The proposed alternative would provide an acceptable level of quality and safety; or (2) Hardship without a compensating increase in quality and safety. 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.
Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request and the NRC to grant the relief requested by the licensee.
3.0 TECHNICAL EVALUATION
3.1 Licensees Relief Request 3.1.1 ASME Code Component Affected The affected component is the pressurizer lower shell temperature nozzle TE101 (nominal pipe size 1 inch). It is classified as ASME Code Class 1, Examination Category B-P, Item No. B15.10.
3.1.2 Applicable Code Edition and Addenda The fourth 10-year interval of the Palo Verde inservice inspection interval runs from June 1, 2019, to July 17, 2028, and complies with ASME Code,Section XI, 2013 Edition, no addenda.
The Code of Construction for the Pressurizer is the ASME Code Section III, 1971 Edition with Addenda through Winter 1973.
The repair installation Code for the previous temperature nozzle repair is ASME Code,Section III, 1986 Edition.
The current repair installation Code of Construction is the ASME Code,Section III, 1974 Edition with Addenda through Winter 1975, reconciled from ASME Code Section III, 2013 Edition.
3.1.3 Applicable Code Requirements The following flaw removal requirements from ASME Code,Section XI, 2013 Edition, are applicable to this submittal:
IWA-4412 requires that defect removal be accomplished in accordance with the requirements of IWA-4420.
IWA 4421 requires that defects be removed or mitigated in accordance with the following requirements:
- a. Removal by mechanical processing be in accordance with IWA-4462
- b. Removal by thermal methods be in accordance with IWA-4461
- d. Removal or mitigation by modification be in accordance with IWA-4340 IWA-5250(a)(3) states Components requiring corrective action shall have repair/replacement activities performed in accordance with IWA-4000 or corrective measures performed where the relevant condition can be corrected without repair/replacement activity.
The following flaw evaluation requirements from ASME Code,Section XI, 2013 Edition, are applicable to this submittal:
IWB-3142.1(b) states A component whose visual examination detects the relevant conditions described in the standards of Table IWB-3410-1 shall be unacceptable for continued service, unless such components meet the requirements of IWB-3142.2, IWB-3142.3, or IWB 3142.4.
IWA-3300(a) states, in part, Flaws detected by the preservice and inservice examinations shall be sized by the bounding rectangle or square for the purpose of description and dimensioning. The dimensions of a flaw shall be determined by the size of a rectangle or square that fully contains the area of the flaw. The flaw aspect ratio shall not exceed 0.5.
IWA-3300(b) states, in part, Flaws shall be characterized in accordance with IWA-3310 through IWA-3390, as applicable IWB-3420 states Each detected flaw or group of flaws shall be characterized by the rules of IWA-3300 to establish the dimension of the flaws. These dimensions shall be used in conjunction with the acceptance standards of IWB-3500.
IWB-3522.1 states, in part, A Component whose visual examination (IWA-5240) detects any of the following relevant conditions shall meet IWB-3142 and IWA-5250 prior to continued service.
- a. IWB-3522.1(a) states any through-wall or through-weld, pressure-retaining material leakage from insulted and noninsulated components; IWB-3610(b) states, in part, For purposes of evaluation by analysis, the depth of flaws in clad components shall be defined in accordance with Figure IWB-3610-1.
The following successive examinations requirements from ASME Code Section XI, 2013 Edition, are applicable to this submittal:
IWB-2420(a) states, in part, The sequence of component examinations which was established during the first inspection interval shall be repeated during each successive inspection interval, to the extent practical.
IWB-2420(b) states, in part, If a component is accepted for continued service in accordance with IWB-3132.3 or IWB-3142.4, the areas containing flaws or relevant conditions shall be reexamined during the next three inspection periods listed in the schedule of the inspection program of IWB-2400.
In addition, the licensee seeks approval for an alternative to a portion of NRC approved ASME Code Case N-722-1, Additional Examinations for PWR [Pressurized Water Reactor] Pressure Retaining Welds in Class 1 Components Fabricated with Alloy 600/82/182 Materials,Section XI, Division 1, which states, that Item No. B15.180, Instrumentation Connections, require visual examination each refueling outage with IWB-3522 acceptance standards.
The licensee seeks approval for an alternative to paragraph 4(a)(2) of NRC-approved ASME Code Case N-638-10, which requires a completed GTAW of a Class 1 component without the use of preheat or postweld heat treatment to be nondestructively examined after the three tempering layers have been in place for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.
3.1.4 Licensees Reason for Request On October 9, 2023, while performing a small nozzle inspection in support of boric acid walkdowns during Palo Verde, Unit 1 refueling outage 24 (1R24), boric acid leakage was found on the area of the weld of the pressurizer lower shell temperature nozzle. The pressurizer nozzle (TE101) is Item No. B15.10 in table IWB-2500-1 of ASME Code,Section XI, and Item No. B15.180 in table 1, in ASME Code Case N-722-1. Non-destructive examination (NDE) of the weld indicated leakage through the reactor coolant pressure boundary. The examination result constitutes defects in the primary coolant system that are unacceptable under ASME Code,Section XI.
The licensee stated in its submittal that the original Alloy 600 temperature nozzle was preemptively replaced in 1992 with an Alloy 690 nozzle, an Alloy 690 outer sleeve, an Alloy 82 weld pad, and an Alloy 82 nozzle-to-weld pad J-groove weld. The leakage found on October 9, 2023, was in the Alloy 82 J-groove weld on the outside of the pressurizer shell.
The licensee also stated in its submittal that visual inspection showed linear indications along the autogenous weld toe and a rounded indication near the midpoint of the autogenous weld.
The portion of the weld surrounding the defect was removed and destructively examined to determine that the Alloy 82 J-groove weld had incomplete fusion indications and a network of solidification cracks, coupled with flaws in the autogenous weld bonding the original J-groove weld to the outer sleeve, resulting in primary water stress corrosion cracking (PWSCC) of the outside diameter (OD) J-groove weld.
The licensee submitted a relief request for one cycle of operation, which began after 1R24, and was approved by the NRC on October 27, 2023. The licensee removed the existing Alloy 690 nozzle, Alloy 82 nozzle J-groove weld, and Alloy 82 weld pad. In accordance with ASME Code,Section XI; ASME Code Case N-638-10; and ASME Code,Section III, the licensee applied a new welded pad and J-groove weld on the outer surface of the pressurizer using Nickel-Alloy 52M filler metal, which has low susceptibility to PWSCC. The new weld pad was deposited onto the OD of the pressurizer shell using the machine GTAW ambient temperature temper bead (ATTB) welding technique, with inert shielding gas. The licensee then attached a nickel-based alloy nozzle with a partial penetration weld using a manual GTAW welding technique and Nickel-Alloy 52M filler metal. The original Alloy 690 sleeve was trimmed back so it would no longer engage the new outer weld pad but the original autogenous weld to the internal J-groove inside the pressurizer and attachment to the sleeve installed in 1992 remained in place.
ASME Code,Section XI, IWA-4412 contains requirements for the removal of, or reduction in size of defects. The licensee is seeking approval of an alternative to these requirements as they apply to the original J-groove weld and autogenous weld that was not removed.
The licensee is also seeking approval of an alternative to the requirements of ASME Code Case N-638-10 that the completed weld be in place for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> prior to the performance of surface and volumetric NDE. Instead of the 48-hour hold, the licensee performed liquid penetrant and ultrasonic acceptance examinations before the 48-hour period ended.
3.1.5 Licensees Proposed Alternative The licensee proposes to use the submitted analyses to satisfy design requirements of ASME Code,Section III, 2013 Edition and show that the replacement temperature nozzle and thermowell is acceptable for 80 years.
The licensee proposed the following alternatives as they relate to ASME Code requirements for flaw removal and flaw evaluation:
As an alternative to flaw removal or reduction in size, of the original J-groove weld on the inner surface of the pressurizer shell, to meet the applicable acceptance standards of IWA-4412, APS proposed to implement an OD repair of the pressurizer lower shell temperature nozzle utilizing an OD weld pad and replacement full nozzle.
As an alternative to performing the NDE required to characterize a flaw under IWB-3420 and IWB-3610(b) in the temperature nozzle penetration, APS proposes analyzing a maximum postulated flaw that bounds the range of flaw sizes that could exist in the original J-groove weld and buttering.
Alternatives as they relate to ASME Code requirements for welding are as follows:
As an alternative to NB-4620, APS proposed to install a welded pad using ATTB welding in accordance with ASME Code Case N-638-10. APS also proposed an alternative to the requirements of Code Case N-638-10, paragraph 4(a)(2), which requires a 48-hour hold time prior to performing NDE. APS performed the weld repair with austenitic filler material in accordance with the ATTB welding technique of Code Case N-638-10, with one exception (i.e., perform NDE without the 48-hour hold time). APS performed the NDE examinations after completion of the weld repair.
3.1.6 Basis for Alternative To support its repair procedure, the licensee provided the following technical basis to demonstrate that the structural integrity of the repaired nozzle will be acceptable for the duration of the life of the plant:
A residual stress analysis of the thermowell nozzle weld through the installation of the original nozzle through the repair configuration.
A fatigue crack growth and fracture mechanics evaluation of the J-groove weld that was left in place A stress evaluation and fatigue analysis of the new thermowell well configuration for the life of repair.
An evaluation of potential corrosion mechanisms that may affect the temperature instrument nozzle repair.
An evaluation of the potential for the outer sleeve of the 1992 repair, the original J-groove weld, or fragments of them to become loose parts and enter the pressurizer 3.1.7 Duration of the Request The licensee submitted this request for the remainder of Palo Verde, Unit 1 initial license extension, which expires June 1, 2045.
3.2
NRC Staff Evaluation
The licensee had previously received NRC approval for one cycle of operation for an installed welded pad using ATTB welding in accordance with ASME Code Case N-638-10. The licensee removed the existing Alloy 82 weld pad and welded a new weld pad to the outer diameter of the pressurizer shell.
The licensee stated that the repair plan was performed in accordance with the ASME Code Section XI, 2013 Edition. Welding was performed using the machine GTAW ATTB welding technique, with inert shielding gas using Alloy 52M (ASME Code,Section II, Part C SFA-5.14, Class ERNiCrFe-7A) filler metal. The weld repair of the new completed weld pad used three layers per the temper bead rules in ASME Code Case N-638-10. The licensee stated that the required Code Case N-638-10 penetrant testing (PT) and ultrasonic testing (UT) examinations of the completed weld pad was performed in accordance with ASME Code,Section III acceptance criteria after the weld pad had been prepared for NDE and dimensionally inspected.
Those examinations verified that there were no unacceptable indications (cracking or fabrication defects) in the newly installed weld pad or original base metal material. The UT examination was performed in accordance with ASME Code,Section III, NB-5244 and includes the weld deposit, fusion zone, and the base metal beneath the weld to assure freedom from lack of fusion and laminar defects.
The licensee, pursuant to 10 CFR 50.55a(z)(1), proposed several alternatives to the ASME Code requirements stated in section 3.1.3 of this SE by performing a design analysis of the repaired nozzle weld in accordance with ASME Code,Section III, 2013 Edition (attachment 3.3 of the submittal). This analysis was updated in the supplement dated March 27, 2025. The licensee stated that the analyses meet the stress requirements of Section III of the ASME Code, that the fatigue life of the nozzle is acceptable for 80 years, and that the new nozzle will not eject from the pressurizer under design-basis conditions for the life of the repair. The NRC staff recognized that this analysis and other analyses submitted for this request provided data for Palo Verde, Units 1, 2, and 3, even though the subject request is solely for Unit 1. However, the staff noted that any approval contained in this SE only applies to the subject request relating solely to Unit 1. All analyses presented in attachment 3 of the licensees submittal dated December 10, 2024, use material properties, design pressures and temperatures, design-basis transient load conditions, frequency of transient cycles, and external loads to inform an ANSYS Finite Element Model (FEM) to simulate conditions. The staff finds this acceptable because ANSYS FEM is a widely accepted industry practice for simulating portions of the plant and the simulations provide detailed output on stresses and fatigue over hundreds of cycles and thousands of iterations.
The NRC staff reviewed this life of repair analysis for compliance with acceptance criteria in ASME Code,Section III. The analysis considered nozzle thickness, shear stress in the repair weld connecting the nozzle to the weld pad, comparison of weld design with minimum Code requirements, assessment of repair and corrosion on reinforcements, and primary plus secondary stresses and fatigue quantitative qualification for the life of the repair. The life of repair analysis used the corrosion analysis (attachment 3.4 of the submittal). The staff found the assumptions of the FEM to be acceptable as they either follow current Palo Verde, Unit 1, operating experience or are conservative, such as assuming leakage through the as-left J-groove weld (ALJGW) from initial installation. The results, presented in section 7.0 of the Life of Repair analysis, show that primary stress qualification, nozzle design, and fatigue over the life of the repair are either below allowable limits or conservative and larger in size than required.
The staff finds the life of repair analysis acceptable because the licensee meets the ASME Code requirements for repair and operation and will continue to inspect this weld repair.
The licensee proposed, as an alternative to the flaw removal or reduction in size acceptance criteria of IWA-4412, to implement an OD repair of the pressurizer lower shell temperature nozzle utilizing an OD weld pad and replacement full nozzle as described in the application. The licensee performed a weld residual stress analysis of the state of the nozzle weld after the 1992 repair (attachment 3.1 of the submittal) and then used the weld residual stress to feed into a crack growth analysis for a postulated radial-axial corner flaw through the entire ALJGW and buttering (attachment 3.2) to demonstrate that the postulated flaw is acceptable for 80 years of operation. The ALJGW analyses used linear elastic fracture mechanics and elastic plastic fracture mechanics to simulate crack growth. The licensee obtained the J-integral resistance curve for the analysis by following Regulatory Guide (RG) 1.161, Evaluation of Reactor Pressure Vessels with Charpy Upper-Shelf Energy Less Than 50 FT-LB, June 1995 (ML003740038), section 3.3.1, which is acceptable because the maximum sulfur value of relevant materials is below the 0.018 wt. percent threshold for sulfur content outlined in RG 1.161. The licensee stated that all IWB-3610 acceptance criteria are met for the life of the plant in the ALJGW analysis by not exceeding primary stress limits for design conditions and showing that the repaired nozzle would not eject under conditions of 150 percent of design pressure. The NRC staff finds this acceptable as all relevant ASME Code acceptance criteria are met for 80 years of operation, showing a factor of safety is present; the ALJGW does not need to be removed, and a flaw does not need to be sized as the crack growth analysis was done for the largest possible flaw.
The licensee also included a loose parts analysis in attachment 3.5 to demonstrate that if any part of the original nozzle and weld were to come loose, they would drop into the pressurizers bottom head and remain there, unlikely to exit the pressurizer. The possibility of pieces exiting the pressurizer and circulating in the reactor coolant system was analyzed and showed a very low likelihood of impact on the steam generator tubes, fuel, or core instrumentation. The NRC staff find this acceptable as any scenario of loose parts is unlikely.
Pursuant to 10 CFR 50.55a(z)(1), the licensee proposes an alternative to ASME Code,Section XI and ASME Code Case N-638-10, paragraph 4(a)(2) that requires a 48-hour hold time prior to performing an NDE. The licensee performed the final examination without waiting the required 48-hours from the completion of the three tempering layers. The licensee stated that the temper bead technique is an effective tool for performing repairs on carbon and low alloy steel materials. The licensee provided a White paper based on PVP 2023-107489, Elimination of the 48-hour Hold for Ambient Temperature Temper Bead Welding with Austenitic Weld Metal, to justify the removal of the 48-hour hold time. This White paper was part of the technical basis for various precedent proposed alternatives from other licensees that the NRC has previously approved.
Upon completion of the new weld pad, the licensee stated that a new J-groove weld preparation was machined into the weld pad. The J-groove weld was dimensionally inspected and underwent PT. The licensee stated that the new Alloy 690 nozzle-to-weld pad was welded with Alloy 52M partial penetration weld and receive progressive PT of the weld in accordance with ASME Code Section III, NB-5245 at half thickness and full thickness after the fillet weld is complete.
The NRC staff finds the licensees performance of the final examination using PT and UT without waiting for the 48-hour hold time to be acceptable because hydrogen induced or delayed cracking will not be likely to occur. The primary water stress corrosion cracking resistant Alloy 52M weld material is being applied with the machine GTAW process, which produces welds with very low diffusible hydrogen when compared to welding processes that use flux (e.g.,
shielded metal arc welding). Therefore, hydrogen induced cracking is not likely to occur and performing the required final PT and UT examinations prior to the 48-hour hold time provided an acceptable level of quality and safety. All required NDEs per ASME Code Case N-638-10 were performed by qualified examiners and a procedure qualified in accordance with ASME Code,Section XI was used. In addition, the NRC is unaware of any instances of hydrogen induced cracking out of the number of weld overlays that have been completed by the nuclear industry using any of the revisions of Code Case N-638-10.
4.0 CONCLUSION
As set forth above, the NRC staff determines that the proposed alternatives provide an acceptable level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all regulatory requirements set forth in 10 CFR 50.55a(z)(1).
Therefore, the NRC authorizes the use of Relief Request 73 at Palo Verde, Unit 1, for the remainder of the Palo Verde Unit 1, initial license extension, which expires on June 1, 2045.
All other requirements in the ASME Code,Section XI for which relief was not specifically requested and approved in this relief request remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: Cory Parker, NRR Date: August 26, 2025
- via eConcurrence NRR-028 OFFICE NRR/DORL/LPL4/PM*
NRR/DORL/LPL4/LA*
NRR/DNRL/NVIB/BC*
NAME WOrders PBlechman ABuford DATE 8/17/2025 8/20/2025 8/25/2025 OFFICE NRR/DORL/LPL4/PM*
NRR/DORL/LPL4/BC*
NAME WOrders TNakanishi DATE 8/25/2025 8/26/2025