ML24262A105
| ML24262A105 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 09/20/2024 |
| From: | Arizona Public Service Co |
| To: | William Orders NRC/NRR/DORL/LPL4 |
| Orders, William | |
| References | |
| Download: ML24262A105 (1) | |
Text
Pre-Submittal Presentation - 1R25 PZR Nozzle Life of Repair - Relief Request 73 September 20, 2024
2 Agenda Introduction
Background
Leak Identification Design History ASME Section XI Code Requirements Proposed Alternative Pursuant to 10 CFR 50.55a(z)(1)
Precedents ASME Section III Code Compliance Loose Parts Corrosion As Left J Groove Weld Analysis Code Reconciliation Schedule Questions
3 Background - Leak Identification 1R24 leak is discovered and repaired on nozzle TW-101
4 Background - Nozzle Design History Pre 1992: Nozzle Alloy 600 & Weld Alloy 82/182
5 Background - Nozzle Design History Post-1992: Nozzle Alloy 690 & Weld Alloy 82
6 Background - Nozzle Design History Root Cause Evaluation (23-10254-010)
The cause of the leak was a compromised outside diameter J-groove fillet weld, consisting of incomplete fusion and a network of solidification cracks, coupled with flaws in the autogenous weld bonding the original J-groove weld to the corrosion sleeve, resulting in PWSCC of the outside diameter J-groove fillet weld.
7 Background - Nozzle Design History Post 2023 (1R24): Nozzle Alloy 690 & Weld Alloy 52M
8 Code Requirements ASME Code,Section XI, 2013 Edition IWB-3522: Pressure retaining material leakage requires corrective action per IWA-5250 and acceptance per IWB-3142 Flaw Removal Corrective actions per IWA-5250, and IWA-4000 repair/replacement activities will eliminate the pressure boundary leakage by installation of the Alloy 52M welds and Alloy 690 nozzle Flaw removal required per IWA-4412/4420
9 Code Requirements ASME Code,Section XI, 2013 Edition Flaw Evaluation 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 are accepted by supplemental evaluation, accepted by corrective measures, or accepted by analytical evaluation.
IWB-3420 states, Each detected flaw or group of flaws shall be characterized by the rules of IWA-3300 to establish the dimensions of the flaws.
IWA-3300 states, Flaws detected by inservice examinations shall be sized IWB-2420(b) states, 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
10 Proposed Alternative Pursuant to 10 CFR 50.55a(z)(1)
For life of repair the following areas needed expanded analysis to envelope remaining plant life:
Loose Parts Corrosion As Left J Groove Weld Analysis Code Reconciliation Duration of proposed alternative:
The proposed alternative is requested to continue through initial license extension for PVNGS Unit 1 (expires June 1, 2045)
Analysis have been prepared for a duration of 80 years
11 Proposed Alternative - Precedents NRC approval via verbal authorization on November 6, 2020 (ML20314A028) for Peach Bottom Atomic Power Station, Unit 2. Safety Evaluation April 23, 2021 (ML21110A680)
NRC verbal authorization on April 15, 2012, for Quad Cities, Unit 2 (ML12107A472). Safety Evaluation January 30, 2013 (ML13016A454)
NRC approval via a verbal authorization on May 17, 2017, for Limerick, Unit 2 (ML17137A307). Safety Evaluation August 14, 2017 (ML17208A090)
NRC verbal authorization on May 9, 2023 (ML23129A312) for Beaver Valley, Unit 2 (ML23118A381) and Letter from David Gudger (Constellation Energy Generation) to NRC dated March 24, 2023, ADAMS Accession No. ML23083B991 PVGS Relief Request 70 verbal authorization (ML23303A011) and written authorization (ML24197A199) for 1 cycle repair approval
12 Proposed Alternative - Code Compliance Repair is code compliant, and all ASME Section III, NB (Class 1) stress requirements are met for the new primary pressure boundary and the fatigue cumulative usage factor requirements.
Environmentally Assisted Fatigue (EAF) was considered and is bounded by EAF program sentinel component in the vicinity, pressurizer heater sleeve.
13 Proposed Alternative - Loose Parts
Purpose:
With modifications to the corrosion sleeve, could it potentially enter the RCS system as a single object or smaller weld/sleeve pieces.
==
Conclusion:==
In the event of a loose part, it would drop down into pressurizer bottom head. Negligible chance to exit pressurizer itself.
14 Proposed Alternative - Corrosion
Purpose:
Evaluate corrosion mechanisms for the following items Exposed low alloy steel base metal (SA-533, Grade B, Class 1) of the PZR shell The replacement Alloy 690 outer nozzle sleeve and temperature nozzle The replacement Alloy 52M weld metals, and the replacement Type 316 thermowell
==
Conclusion:==
For life of repair for the above items For exposed low alloy steel base metal galvanic corrosion, hydrogen embrittlement, SCC, and crevice corrosion are not expected to be a concern.
For Alloy 690 and 52M extensive testing and OE demonstrate no susceptibility in PWR environment No SCC expected at the interface between Alloy 52M and Type 316 thermowell WCAP -15973-P was utilized and assumes a cycle run to run corrosion rate. Cycles will be evaluated using STUDY 13-MS-B041 to ensure compliance with corrosion rate.
15 Proposed Alternative - As Left J Groove Weld
Purpose:
Using fracture mechanics demonstrate suitability of leaving a postulated degraded J-groove weld in the pressurizer for 80 years of operation. Residual Weld Stress Analysis report is a direct input into the flaw evaluation analysis
==
Conclusion:==
Both linear elastic and elastic-plastic fracture mechanics demonstrates that the postulated flaw is shown to be acceptable for 80 years. In addition, no structure collapse at 150% of Design Pressure. Per analyses, successive flaw examinations are not necessary.
16 Proposed Alternative - Code Reconciliation
Purpose:
Reconcile the nozzle modification code requirements to code year of record.
==
Conclusion:==
Code requirements reconciled iaw ASME Section XI IWA-4220-4226 2013 Ed. Specifically with regards to welding, weld material, flaw removal, Nondestructive Examination/Testing, and design of the modification itself.
The repair is code compliant and meets ASME Section III requirements for primary stresses, primary + secondary stresses, and fatigue.
17 Schedule Proposed submittal date for RR-73 Late October 2024 Request NRC review completion to support restart following 1R25 Early May 2025
Questions?