ML25247A295

Renewed Operating License No. NPF-41, Relief Request 74 - Proposed Alternative for Steam Generator and Pressurizer Pressure Retaining Welds for PVNGS

ML25247A295
Person / Time
Site:	Palo Verde
Issue date:	09/04/2025
From:	Spina J Arizona Public Service Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
102-09000-JLS/MDD
Download: ML25247A295 (1)

Text

10 CFR 50.55a A member of the STARS Alliance, LLC Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek Jennifer Spina Vice President Nuclear Regulatory & Oversight Palo Verde Nuclear Generating Station P.O. Box 52034 Phoenix, AZ 85072 Mail Station 7602 Tel: 623.393.4621 102-09000-JLS/MDD 6HSWHPEHU , 2025 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, and 3 Docket Nos. STN 50-528, 50-529, and 50-530 Renewed Operating License No. NPF-41 Relief Request 74 - Proposed Alternative for Steam Generator and Pressurizer Pressure Retaining Welds for PVNGS Units 1, 2, and 3 Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a, Codes and Standards, paragraph (z)(1), Arizona Public Service Company (APS) requests Nuclear Regulatory Commission (NRC) staff authorization of Relief Request 74, on the basis that the proposed alternative provides an acceptable level of quality and safety.

In 2017 the Electric Power Research Institute (EPRI) started a project for extended interval examinations of Steam Generator Class 2 feedwater and main steam nozzle components, Remaining Class 1 and 2 Steam Generator (SG) components and the Pressurizer vessel and nozzle components. These ASME Section XI components were identified by the industry as components with very few to no indications detected while requiring considerable impacts to outage resources for carpenter scaffold support, insulator support and non-destructive examination (NDE) support considering personnel safety and radiological risk.

The proposed alternative is to defer the examinations for the SGs and pressurizers at PVNGS from the current ASME Code,Section XI, Division 1 10-year requirement for the remainder of the 4th interval, the 5th and 6th intervals to the end of the current renewed operating licenses scheduled for June 1, 2045, for Unit 1, April 24, 2046, for Unit 2 and November 25, 2047, for Unit 3.

APS is the owner of the information originally marked Proprietary by our vendor in the Attachments and has determined that the information is not proprietary and, therefore, need not be withheld from public disclosure pursuant to 10 CFR 2.390.

APS makes no new commitments to the NRC in this letter. Should you need further information regarding this letter, please contact Michael. D. DiLorenzo, Licensing Department Leader, at (623) 393-3495.

102-09000-JLS/MDD ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Relief Request 74 - Proposed Alternative for Steam Generator and Pressurizer Pressure Retaining Welds for PVNGS Units 1, 2, and 3 Page 2 Sincerely, JS/MDD/cr

Enclosure:

Palo Verde Nuclear Generating Station, Unit 1, 2, and 3, Steam Generator and Pressurizer Welds - Relief Request Number 74 cc:

J. D. Monninger NRC Region IV Regional Administrator W. T. Orders NRC NRR Project Manager for PVNGS E. R. Lantz Senior Resident Inspector for PVNGS Spina, Jennifer (Z08962)

Digitally signed by Spina, Jennifer (Z08962)

Date: 2025.09.04 13:43:19 -07'00'

Enclosure PALO VERDE NUCLEAR GENERATING STATION, UNIT 1, 2, and 3 STEAM GENERATOR AND PRESSURIZER WELDS Relief Request Number 74

Enclosure Relief Request 74 i

Contents Page 1.0 ASME CODE COMPONENT AFFECTED................................................................. 1 2.0 APPLICABLE CODE EDITION AND ADDENDA....................................................... 5 3.0 APPLICABLE CODE REQUIREMENTS.................................................................. 5 4.0 REASON FOR REQUEST................................................................................... 7 5.0 PROPOSED ALTERNATIVE AND BASIS FOR USE.................................................. 7 6.0 DURATION OF PROPOSED ALTERNATIVE.......................................................... 19 7.0 PRECEDENTS................................................................................................ 19

8.0 REFERENCES

................................................................................................ 21 List of Tables Table 1 Palo Verde Pressurizer Shell Dimensions................................................... 10 Table 2 Palo Verde Pressurizer Nozzle Dimensions..................................................10 Table 3 Sensitivity to Combined effects of Fracture Thoughness, Stress, and Weld Flaw Density for 80 Years for the Palo Verde Pressurizer Welds.....................13 Table 4 Palo Verde SG 4th Interval Section XI Examination Requirements and Completion Status...................................................................................16 Table 5 Palo Verde Pressurizer 4th Interval Section XI Examination Requirements and Completion Status...................................................................................17 List of Figures Figure 1 Applied K vs. Fracture Thoughness as a Function of Temperature for Case ID PRSHC-BW-2C........................................................................... 14 ATTACHMENT 1 Plant-Specific Applicability for Pressurizers ATTACHMENT 2 Examination History ATTACHMENT 3 SI Calculation No. 2300243.301, Finite Element Model Development and Thermal/Mechanical Stress Analysis of PVNGS Units 1, 2, and 3 Steam Generator Components, Revision 0 ATTACHMENT 4 SI Calculation No. 2300243.302, Deterministic and Probabilistic Fracture Mechanics Analyses of PVNGS Units 1, 2, and 3 CE System 80 Steam Generator Welds and Components, Revision 0 ATTACHMENT 5 Results of Industry Survey

Enclosure Relief Request 74 ii Nomenclature ACRONYMS:

ASME American Society of Mechanical Engineers B&W Babcock and Wilcox BWR Boiling Water Reactor BWRVIP Boiling Water Reactor Vessel and Internals Program CE Combustion Engineering CFR Code of Federal Regulations DFM Deterministic fracture mechanics EAF Environmentally assisted fatigue EPRI Electric Power Research Institute FAC Flow accelerated corrosion FEA Finite element analysis FW Feedwater ISI Inservice Inspection MIC Microbiologically influenced corrosion MS Main Steam NPS Nominal pipe size NRC Nuclear Regulatory Commission NSSS Nuclear steam supply system O.D.

Outside diameter POD Probability of detection PFM Probabilistic fracture mechanics PSI Preservice inspection PWR Pressurized Water Reactor PZR Pressurizer SCC Stress corrosion cracking WEC Westinghouse Electric Company

Enclosure Relief Request 74 1

ASME CODE COMPONENTS AFFECTED:

Steam Generators Code Class:

Class 1 and Class 2

==

Description:==

Steam generator (SG) pressure-retaining welds and full penetration welded nozzles (nozzle-to-shell welds and inside radius sections)

Examination Category: Class 1, Category B-B, pressure-retaining welds in vessels other than reactor vessels Class 1, Category B-D, full penetration welded nozzles in vessels Class 2, Category C-A, pressure-retaining welds in pressure vessels Class 2, Category C-B (Pressure Retaining Nozzle Welds in Pressure Vessels,Section XI, Division 1)

Item Numbers:

B2.31 - Steam generators (primary side), circumferential head weld B2.40 - Steam generators (primary side), tubesheet-to-head weld B3.130 - Steam generators (primary side), nozzle-to-vessel welds C1.10 - Shell circumferential welds C1.20 - Head circumferential welds C1.30 - Tubesheet-to-shell welds C2.21 - Nozzle-to-shell (nozzle-to-head or nozzle-to-nozzle) welds C2.22 - Nozzle inside radius sections Palo Verde Unit 1 SG Components ASME Category ASME Item No.

Component ID Component Description B-B B2.31 3-108 Circumferential Shell Weld B-B B2.40 3-106 Tubesheet to Stay Cylinder Extension Weld B-B B2.40 3-107 Tubesheet to Head B-D B3.130 3-100 Nozzle to Vessel Weld B-D B3.130 3-101 Nozzle to Vessel Weld B-D B3.130 3-102 Nozzle to Vessel Weld B-D B3.130 4-100 Nozzle to Vessel Weld B-D B3.130 4-101 Nozzle to Vessel Weld B-D B3.130 4-102 Nozzle to Vessel Weld B-B B2.40 4-106 Tubesheet to Stay Cylinder Extension Weld B-B B2.40 4-107 Tubesheet to Head B-B B2.31 4-108 Circumferential Shell Weld C-B C2.21 41-102 Nozzle to vessel C-B C2.22 41-102-IR Nozzle IR C-B C2.21 41-103 Nozzle to vessel C-B C2.22 41-103-IR Nozzle IR C-A C1.30 41-104 SG1 Shell to Tube Sheet C-A C1.10 41-105 SG1 Shell to Conical Weld C-A C1.10 41-106 SG1 Shell to Conical Weld C-A C1.20 41-107 SG1 Shell to Head

Enclosure Relief Request 74 2

Palo Verde Unit 1 SG Components ASME Category ASME Item No.

Component ID Component Description C-B C2.21 41-109 SG1 to Nozzle C-B C2.21 41-110 Nozzle to vessel C-B C2.21 41-114 Nozzle to vessel C-B C2.22 41-114-IR Nozzle IR C-B C2.21 41-115 Nozzle to vessel C-B C2.22 41-115-IR Nozzle IR C-B C2.21 42-102 Nozzle to vessel C-B C2.22 42-102-IR Nozzle IR C-B C2.21 42-103 Nozzle to vessel C-B C2.22 42-103-IR Nozzle IR C-A C1.30 42-104 SG2 Shell to Tube Sheet C-A C1.10 42-105 SG2 Shell to Conical Weld C-A C1.10 42-106 SG2 Shell to Conical Weld C-A C1.20 42-107 SG2 Shell to Head C-B C2.21 42-109 SG2 to Nozzle C-B C2.21 42-110 Nozzle to vessel C-B C2.21 42-114 Nozzle to vessel C-B C2.22 42-114-IR Nozzle IR C-B C2.21 42-115 Nozzle to vessel C-B C2.22 42-115-IR Nozzle IR Palo Verde Unit 2 SG Components ASME Category ASME Item No.

Component ID Component Description B-B B2.31 3-105 Stay Cylinder to Head B-B B2.31 4-105 Stay Cylinder to Head B-B B2.40 3-106 Tubesheet to Stay Cylinder Extension Weld B-B B2.40 3-107 Tubesheet to Head B-B B2.40 4-106 Tubesheet to Stay Cylinder Extension Weld B-B B2.40 4-107 Tubesheet to Head B-D B3.130 3-100 Nozzle to Vessel Weld B-D B3.130 3-101 Nozzle to Vessel Weld B-D B3.130 3-102 Nozzle to Vessel Weld B-D B3.130 4-100 Nozzle to Vessel Weld B-D B3.130 4-101 Nozzle to Vessel Weld B-D B3.130 4-102 Nozzle to Vessel Weld C-B C2.21 41-102 Nozzle to vessel C-B C2.22 41-102-IR Nozzle IR C-B C2.21 41-103 Nozzle to vessel C-B C2.22 41-103-IR Nozzle IR C-A C1.30 41-104 SG1 Shell to Tube Sheet C-A C1.10 41-105 SG1 Shell to Conical Weld C-A C1.10 41-106 SG1 Shell to Conical Weld C-A C1.20 41-107 SG1 Shell to Head C-B C2.21 41-109 SG1 to Nozzle C-B C2.21 41-110 Nozzle to vessel C-B C2.21 41-114 Nozzle to vessel C-B C2.22 41-114-IR Nozzle IR C-B C2.21 41-115 Nozzle to vessel C-B C2.22 41-115-IR Nozzle IR C-B C2.21 42-102 Nozzle to vessel

Enclosure Relief Request 74 3

Palo Verde Unit 2 SG Components ASME Category ASME Item No.

Component ID Component Description C-B C2.22 42-102-IR Nozzle IR C-B C2.21 42-103 Nozzle to vessel C-B C2.22 42-103-IR Nozzle IR C-A C1.30 42-104 SG2 Shell to Tube Sheet C-A C1.10 42-105 SG2 Shell to Conical Weld C-A C1.10 42-106 SG2 Shell to Conical Weld C-A C1.20 42-107 SG2 Shell to Head C-B C2.21 42-109 SG2 to Nozzle C-B C2.21 42-110 Nozzle to vessel C-B C2.21 42-114 Nozzle to vessel C-B C2.22 42-114-IR Nozzle IR C-B C2.21 42-115 Nozzle to vessel C-B C2.22 42-115-IR Nozzle IR Palo Verde Unit 3 SG Components ASME Category ASME Item No.

Component ID Component Description B-D B3.130 3-101 Nozzle to Vessel Weld B-D B3.130 3-102 Nozzle to Vessel Weld B-B B2.40 3-106 Tubesheet to Stay Cylinder Extension Weld B-B B2.40 3-107 Tubesheet to Head B-B B2.31 3-108 Circ weld B-D B3.130 3-100 Nozzle to Vessel Weld B-D B3.130 4-101 Nozzle to Vessel Weld B-D B3.130 4-102 Nozzle to Vessel Weld B-B B2.40 4-106 Tubesheet to Stay Cylinder Extension Weld B-B B2.40 4-107 Tubesheet to Head B-B B2.31 4-108 Circ weld B-D B3.130 4-100 Nozzle to Vessel Weld C-A C1.30 41-104 SG1 Shell to Tube Sheet C-A C1.10 41-105 SG1 Shell to Conical Weld C-A C1.10 41-106 SG1 Shell to Conical Weld C-A C1.20 41-107 SG1 Shell to Head C-A C1.30 42-104 SG2 Shell to Tube Sheet C-A C1.10 42-105 SG2 Shell to Conical Weld C-A C1.10 42-106 SG2 Shell to Conical Weld C-A C1.20 42-107 SG2 Shell to Head C-B C2.21 41-102 Nozzle to vessel C-B C2.22 41-102-IR Nozzle IR C-B C2.21 41-103 Nozzle to vessel C-B C2.22 41-103-IR Nozzle IR C-B C2.21 41-109 SG1 to Nozzle C-B C2.21 41-110 Nozzle to vessel C-B C2.21 41-114 Nozzle to vessel C-B C2.22 41-114-IR Nozzle IR C-B C2.21 41-115 Nozzle to vessel C-B C2.22 41-115-IR Nozzle IR C-B C2.21 42-102 Nozzle to vessel C-B C2.22 42-102-IR Nozzle IR C-B C2.21 42-103 Nozzle to vessel C-B C2.22 42-103-IR Nozzle IR

Enclosure Relief Request 74 4

Palo Verde Unit 3 SG Components ASME Category ASME Item No.

Component ID Component Description C-B C2.21 42-109 SG2 to Nozzle C-B C2.21 42-110 Nozzle to vessel C-B C2.21 42-114 Nozzle to vessel C-B C2.22 42-114-IR Nozzle IR C-B C2.21 42-115 Nozzle to vessel C-B C2.22 42-115-IR Nozzle IR Pressurizers Code Class:

Class 1

==

Description:==

Pressurizer vessel head, shell-to-head, and nozzle-to-vessel welds Examination Category: Class 1, Category B-B, pressure-retaining welds in vessels other than reactor vessels Class 1, Category B-D, full penetration welded nozzles in vessels Item Numbers:

B2.11 - Pressurizer, shell-to-head welds, circumferential B2.12 - Pressurizer, shell-to-head welds, longitudinal B3.110 - Pressurizer, nozzle-to-vessel welds Palo Verde Unit 1 Pressurizer Components ASME Category ASME Item No.

Component ID Component Description B-B B2.11 5-002 Circumferential Shell Weld B-B B2.12 5-003 Longitudinal Shell Weld(1)

B-B B2.12 5-004 Longitudinal Shell Weld(1)

B-B B2.12 5-006 Longitudinal Shell Weld(1)

B-B B2.12 5-007 Longitudinal Shell Weld(1)

B-B B2.11 5-008 Circumferential Shell Weld B-D B3.110 5-009 Nozzle-to-Vessel Weld B-D B3.110 5-010 Nozzle-to-Vessel Weld B-D B3.110 5-011 Nozzle-to-Vessel Weld B-D B3.110 5-012 Nozzle-to-Vessel Weld B-D B3.110 5-013 Nozzle-to-Vessel Weld B-D B3.110 5-014 Nozzle-to-Vessel Weld Note 1: The applicable portion of the longitudinal seam weld is where it intersects the associated Item No. B2.11 (shell to head) weld.

Palo Verde Unit 2 Pressurizer Components ASME Category ASME Item No.

Component ID Component Description B-B B2.11 5-002 Circumferential Shell Weld B-B B2.12 5-003 Longitudinal Shell Weld(1)

B-B B2.12 5-004 Longitudinal Shell Weld(1)

B-B B2.12 5-006 Longitudinal Shell Weld(1)

B-B B2.12 5-007 Longitudinal Shell Weld(1)

B-B B2.11 5-008 Circumferential Shell Weld B-D B3.110 5-009 Nozzle to Vessel Weld B-D B3.110 5-010 Nozzle to Vessel Weld B-D B3.110 5-011 Nozzle to Vessel Weld

Enclosure Relief Request 74 5

Palo Verde Unit 2 Pressurizer Components ASME Category ASME Item No.

Component ID Component Description B-D B3.110 5-012 Nozzle to Vessel Weld B-D B3.110 5-013 Nozzle to Vessel Weld B-D B3.110 5-014 Nozzle to Vessel Weld Note 1: The applicable portion of the longitudinal seam weld is where it intersects the associated Item No. B2.11 (shell to head) weld.

Palo Verde Unit 3 Pressurizer Components ASME Category ASME Item No.

Component ID Component Description B-B B2.11 5-002 Circumferential Shell Weld B-B B2.12 5-003 Longitudinal Shell Weld(1)

B-B B2.12 5-004 Longitudinal Shell Weld(1)

B-B B2.12 5-006 Longitudinal Shell Weld(1)

B-B B2.12 5-007 Longitudinal Shell Weld(1)

B-B B2.11 5-008 Circumferential Shell Weld B-D B3.110 5-009 Nozzle to Vessel Weld B-D B3.110 5-010 Nozzle to Vessel Weld B-D B3.110 5-011 Nozzle to Vessel Weld B-D B3.110 5-012 Nozzle to Vessel Weld B-D B3.110 5-013 Nozzle to Vessel Weld B-D B3.110 5-014 Nozzle to Vessel Weld Note 1: The applicable portion of the longitudinal seam weld is where it intersects the associated Item No. B2.11 (shell to head) weld.

APPLICABLE CODE EDITION AND ADDENDA:

The fourth 10-year inservice inspection (ISI) interval Code of record for Palo Verde is the 2013 Edition of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components.

APPLICABLE CODE REQUIREMENT:

Steam Generators ASME Section XI IWB-2500(a), Table IWB-2500-1, examination Categories B-B and B-D and IWC-2500(a), Table IWC-2500-1, Examination Categories C-A and C-B require examination of the following Item Nos.:

Item No. B2.31 - Volumetric examination of all nozzles during the first Section XI inspection interval and one weld per head during successive intervals. The examination areas for are shown in Figures IWB-2500-3.

Item No. B2.40 - Volumetric examination of essentially 100% of the weld length of all welds during the first Section XI inspection interval. For successive inspection intervals the examination may be limited to one vessel among the group of vessels performing a similar function. The examination volume is shown in Figure IWB-2500-6.

Item No. B3.130 - Volumetric examination of all nozzles during each Section XI inspection interval. The examination areas for are shown in Figures IWB-2500-7(a), (b),

Enclosure Relief Request 74 6

(c) and (d).

Item No. C1.10 - Volumetric examination of essentially 100% of the weld length of the cylindrical-shell-to-conical shell-junction welds and shell (or head)-to-flange welds during each Section XI inspection interval. In the case of multiple vessels of similar design, size, and service (such as steam generators, heat exchangers), the required examinations may be limited to one vessel or distributed among the vessels. The examination volume is shown in Figure IWC-2500-1.

Item No. C1.20 - Volumetric examination of essentially 100% of the weld length of the head-to-shell weld during each Section XI inspection interval. In the case of multiple vessels of similar design, size, and service (such as steam generators, heat exchangers), the required examinations may be limited to one vessel or distributed among the vessels. The examination volume is shown in Figure IWC-2500-1.

Item No. C1.30 - Volumetric examination of essentially 100% of the weld length of the tubesheet-to-shell welds during each Section XI inspection interval. In the case of multiple vessels of similar design, size, and service (such as steam generators, heat exchangers), the required examinations may be limited to one vessel or distributed among the vessels. The examination volume is shown in Figure IWC-2500-2.

Item No. C2.21 - Volumetric and surface examination of all nozzle welds at terminal ends of piping runs during each Section XI inspection interval. In the case of multiple vessels of similar design, size, and service (such as steam generators, heat exchangers), the required examinations may be limited to one vessel or distributed among the vessels. The examination area and volume are shown in Figures IWC-2500-4(a), (b), or (d).

Item No. C2.22 - Volumetric examination of all nozzle inside radius sections at terminal ends of piping runs during each Section XI inspection interval. In the case of multiple vessels of similar design, size, and service (such as steam generators, heat exchangers), the required examinations may be limited to one vessel or distributed among the vessels. The examination volume is shown in Figures IWC-2500-4(a), (b), or (d).

Pressurizers ASME Section XI IWB-2500(a), Table IWB-2500-1, examination Categories B-B and B-D require examination of the following Item Nos.:

Item No. B2.11 - Volumetric examination of both circumferential shell-to-head welds during each inspection interval.

Item No. B2.12 - Volumetric examination of one foot of all longitudinal shell-to-head welds that intersect circumferential welds during the first interval and one foot of one longitudinal shell-to-head weld that intersects a circumferential weld during successive intervals.

Item No. B3.110 - Volumetric examination of all full penetration nozzle-to-vessel welds during each inspection interval.

Enclosure Relief Request 74 7

REASON FOR REQUEST:

The Electric Power Research Institute (EPRI) performed assessments in References

[9.1], [9.2], [9.3] and [9.4] of the basis for the ASME Code,Section XI examination requirements specified for the above listed ASME Code,Section XI, Division 1 examination categories for SG and pressurizer welds. The assessments include a survey of inspection results from 74 domestic and international nuclear units and flaw tolerance evaluations using probabilistic fracture mechanics (PFM) and deterministic fracture mechanics (DFM). The Reference [9.1] through [9.4] reports concluded that the current ASME Code,Section XI ISI examinations can be deferred for some time with no impact to plant safety. Based on the conclusions of the EPRI reports supplemented by plant-specific evaluations contained herein, APS is requesting an ISI examination deferral for the subject welds. The Reference [9.1] through [9.4] reports were developed consistent with the recommendations provided in EPRIs White Paper on suggested content for PFM submittals [9.10] and NRC Regulatory Guide 1.245 for PFM submittals and associated technical basis [9.11, 9.12].

PROPOSED ALTERNATIVE AND BASIS FOR USE:

Steam Generators For Palo Verde, APS is requesting an inspection alternative to the examination requirements of ASME Code,Section XI, Tables IWB-2500-1 and IWC-2500-1, for the following examination categories and item numbers:

ASME Category Item No.

Description B-B B2.31 Steam generators (primary side), circumferential head weld B-B B2.40 Steam generators (primary side), tubesheet-to-head weld B-D B3.130 Steam generators (primary side), nozzle-to-vessel welds C-A C1.10 Shell circumferential welds C-A C1.20 Head circumferential welds C-A C1.30 Tubesheet-to-shell welds C-B C2.21 Nozzle-to-shell (nozzle-to-head or nozzle-to-nozzle) welds C-B C2.22 Nozzle inside radius sections The Palo Verde SGs were replaced on the following schedule:

Unit 1 = 2005 (third period of the second inspection interval)

Unit 2 = 2003 (second period of the second inspection interval)

Unit 3 = 2007 (third period of the second inspection interval)

The new SG welds and components received the required preservice inspections (PSI) prior to service followed by ISI examinations through the first period of the current fourth inspection interval.

The proposed alternative is to defer the ISI examinations for these Item Nos. for the SGs at Palo Verde from the current ASME Code,Section XI, Division 1 requirement to for the remainder of the 4th interval, the 5th and 6th intervals to the end of operating license

Enclosure Relief Request 74 8

scheduled for June 1, 2045 for Unit 1, April 24, 2046 for Unit 2 and November 25, 2047 for Unit 3.

Pressurizers For Palo Verde, APS is requesting an inspection alternative to the examination requirements of ASME Section XI, Table IWB-2500-1 for the following examination categories and item numbers:

ASME Category Item No.

Description B-B B2.11 Pressurizer, shell-to-head welds, circumferential B-B B2.12 Pressurizer, shell-to-head welds, longitudinal B-D B3.110 Pressurizer, nozzle-to-vessel welds Palo Verde still has its original pressurizers. The pressurizer welds and components received the required PSI examinations prior to service followed by ISI examinations through the first period of the current fourth inspection interval.

The proposed alternative is to defer the ISI examinations for these Item Nos. for the pressurizers at Palo Verde from the current ASME Code,Section XI, Division 1 requirement to for the remainder of the 4th interval, the 5th and 6th intervals to the end of operating license scheduled for June 1, 2045 for Unit 1, April 24, 2046 for Unit 2 and November 25, 2047 for Unit 3.

Technical Basis A summary of the key aspects of the technical basis for this request is summarized below. The applicability of the technical basis to Palo Verde is shown in Attachments 1 through 4.

Applicability of the Degradation Mechanism Evaluation in References [9.1] through [9.4]

to Palo Verde An evaluation of degradation mechanisms that could potentially impact the reliability of the SG and pressurizer welds was performed in References [9.1] through [9.4]. The degradation mechanisms that were evaluated included stress corrosion cracking (SCC),

environmental assisted fatigue (EAF), microbiologically influenced corrosion (MIC),

pitting, crevice corrosion, erosion-cavitation, erosion, flow accelerated corrosion (FAC),

general corrosion, galvanic corrosion, and mechanical/thermal fatigue. Other than the potential for EAF and mechanical/thermal fatigue, there were no active degradation mechanisms identified that significantly affect the long-term structural integrity of the SG and pressurizer welds covered in this request. This observation was acknowledged by the NRC in Section 3.8, page 6, second paragraph of the Reference [9.13] Safety Evaluation (SE) for Vogtle Units 1 & 2; Section 2.0, page 3, second paragraph of the Reference [9.14] SE for Millstone Unit 2 and Section 2, page 3, second paragraph of the Reference [9.15] SE for Salem Units 1 & 2. The materials and operating conditions for the SG and pressurizer components considered in this Request for Alternative are similar to those in References [9.1], [9.2] and [9.3], and therefore the conclusions of those reports apply to the components in this Request for Alternative. The fatigue-related mechanisms were considered in the PFM and DFM evaluations in References

Enclosure Relief Request 74 9

[9.1] through [9.4].

As part of the technical bases in References [9.1] through [9.4], a comprehensive industry survey involving 74 PWR units was conducted to determine the degradation history of these components. The survey reviewed examination results from the start of plant operation. Most of these plants have operated for over 30 years and in some cases over 40 years. The results showed that no examinations identified any unknown degradation mechanisms (i.e., mechanisms other than those listed above). Based on this exhaustive industry survey, it is concluded that although the emergence of an unknown degradation mechanism cannot be completely ruled out, the possibility of the occurrence of such an unknown degradation mechanism is highly unlikely.

Applicability of the Stress Analysis in References [9.1] through [9.4] to Palo Verde Steam Generators The geometric configuration of the SG used in the Reference [9.1], [9.2] and [9.4] stress analyses, while consistent with standard Westinghouse/CE SG designs, is not appropriate for the System 80 SG design at Palo Verde. A plant-specific stress analysis was therefore performed for the System 80 SG design and is documented in Attachment

3. The plant-specific stress analysis performed in Attachment 3, together with the examination history provided in Attachment 2, demonstrates that all plant-specific requirements are met for Palo Verde.

The technical approach used in the stress analysis for the System 80 SG design in is consistent with Section 7 of the Reference [9.1], [9.2] and [9.4] reports, using the Palo Verde plant-specific geometry and operating conditions. The stress results are presented in Section 6.0 of Attachment 3. Due to the relatively complicated geometry of the System 80 SG design (shown in Figures 1 through 3 of Attachment 3),

29 critical stress paths were chosen for subsequent fracture mechanics evaluations, compared to 4, 14 and 3 critical stress paths in the Reference [9.1], [9.2] and [9.4] EPRI reports, respectively. The locations of the critical stress paths are provided in Figures 8 through 21 of Attachment 3, which corresponds to Figure 7-8, 7-18 and 7-31 of Reference [9.1], Figure 7-24 of Reference [9.2] and Figure 7-8 of Reference [9.4]

respectively.

Enclosure Relief Request 74 10 Pressurizers Finite element analysis (FEA) was performed in Reference [9.3] to determine the stresses in the pressurizer welds covered in this request. The analysis was performed using representative Westinghouse plant geometries (which bound CE plants), bounding transients, and typical material properties. The results of the stress analyses were used in a flaw tolerance evaluation. The applicability of the Reference [9.3] FEA analysis to Palo Verde is demonstrated in Attachments 2 and 3 and confirms that all plant-specific requirements are met. In particular, the key geometric parameters used in the Reference

[9.3] stress analysis are compared to those of Palo Verde in Tables 1 and 2:

Table 1. Palo Verde Pressurizer Shell Dimensions Plant Upper Shell ID (in)

Upper Shell/Clad Thk (in)

Upper Shell Ri/t Lower Shell ID (in)

Lower Shell/Clad Thk (in)

Lower Shell Ri/t EPRI Report (Table 4-4 of

[9.1])

84(1)(2) 3.75/0.063(1)(2) 11.2 84(1)(2) 3.75/0.063(1)(2) 11.2 Palo Verde U1 96.38 [9.5]

5.25/0.16

[9.5, 9.6]

9.2 96.38

[9.5, 9.6]

5.25/0.5

[9.5, 9.7]

9.2 Palo Verde U2 96.38 [9.5]

5.25/0.16

[9.5, 9.6]

9.2 96.38

[9.5, 9.6]

5.25/0.5

[9.5, 9.7]

9.2 Palo Verde U3 96.38 [9.5]

5.25/0.16

[9.5, 9.6]

9.2 96.38

[9.5, 9.6]

5.25/0.5

[9.5, 9.7]

9.2 Notes

1. Westinghouse pressurizer dimensions, associated with model for bottom head.

2. Determined using OD and thickness from Table 4-4 of Reference [9.1].

Table 2. Palo Verde Pressurizer Nozzle Dimensions Plant Surge Nzl ID (in)

Surge Nzl Thk (in)

Surge Nzl Ri/t SRV Nzl ID (in)

SRV Nzl Thk (in)

SRV Nzl Ri/t EPRI Report (Table 4-5 of

[9.1])

12.44(1) 3.27(1) 1.9 5.625(2) 1.19(2) 2.4 Palo Verde U1 11.875 [9.5]

4.31(3) 1.4 5.63 [9.5]

1.94(4) 1.5 Palo Verde U2 11.875 [9.5]

4.31(3) 1.4 5.63 [9.5]

1.94(4) 1.5 Palo Verde U3 11.875 [9.5]

4.31(3) 1.4 5.63 [9.5]

1.94(4)

1.5 Notes

1. Westinghouse pressurizer nozzle dimensions, associated with model for bottom head.

2. CE pressurizer nozzle dimensions, associated with model for top head.

3. Determined using ID from Reference [9.5] and OD from Reference [9.8].

4. Determined using ID from Reference [9.5] and OD from Reference [9.9].

As noted by the NRC in Section 5.1, page 7, fourth paragraph of the Salem SE [9.15],

the dominant stress is the pressure stress. Therefore, the variation in the Ri/t ratio determined in Tables 1 and 2 can be used to scale up the stresses of the Reference

[9.3] report to obtain the plant-specific stresses for each unit and component. Since all pressurizer welds at Palo Verde listed in Section 1 are shell welds, Table 1 applies.

From this table, the stress ratio (Ri/t) of Palo Verde relative to the that used in the EPRI report is (9.2/11.2) = 0.82. Therefore, the stresses at Palo Verde are less than those considered in the EPRI report, indicating that the Westinghouse plant geometry used in

Enclosure Relief Request 74 11 the stress analysis of Reference [9.3] bounds the Palo Verde pressurizer design.

In the selection of the transients in Section 5 of Reference [9.3] and the subsequent stress analyses in Section 7, test conditions beyond a system leakage test were not considered since pressure tests at Palo Verde are performed at normal operating conditions. No hydrostatic testing had been performed at Palo Verde since the unit went into operation.

Applicability of the Flaw Tolerance Evaluation in References [9.1] through [9.4] to Palo Verde Steam Generators Plant-specific DFM and PFM evaluations were performed for the Palo Verde System 80 SG design using the results of the stress analyses in Attachment 3. The evaluations are presented in Attachment 4 and demonstrate that all plant-specific requirements are met for Palo Verde.

The technical approach used in the DFM evaluation for the Palo Verde System 80 SG is consistent with Section 8.3, 8.2 and 8.2 in the Reference [9.1], [9.2] and [9.4] EPRI reports, respectively. The design inputs used in the DFM evaluation are summarized in Table 2 of Attachment 4. An initial flaw size of 5.2% of the wall thickness was assumed, equivalent to the most conservative ASME Code,Section XI acceptance standard for these components. The ASME Code,Section XI, Appendix A, Paragraph A-4300 fatigue crack growth (FCG) law was used in the evaluation using the through-wall stress distributions from the stress analyses in Attachment 3. The fracture mechanics models identified in Section 8.2.2.5 of the Reference [9.1] EPRI report were used to determine the length of time for the postulated initial flaw to grow to a depth of 80% of the wall thickness (assumed to equate to leakage in this evaluation) or the depth at which the allowable toughness (upper shelf value of KIC equal to 220 ksi¥inch) was reached, whichever was less.

The results of the DFM evaluation for the System 80 SG configuration are summarized in Table 5 of Attachment 4, which shows that the period required for hypothetical postulated flaws to leak are very long (in excess of 200 years). This indicates that the System 80 SG components are very flaw tolerant. The maximum stress intensity factors K from the DFM evaluation are also shown in Table 5 of Attachment 4. As seen in this table, they are all below the fracture toughness of 220 ksi¥inch.

The PFM evaluations in Attachment 4 were performed consistently with the approach described in Section 8.2 of the Reference [9.1] EPRI report using PROMISE, Version

2.0. (Note

See expanded discussion of this software under the Palo Verde pressurizer flaw tolerance section, below.) The design inputs used for the PFM evaluation are shown in Table 6 of Attachment 4. For the replacement Palo Verde System 80 SGs, PSI examinations have been performed followed by ISI examinations over one completed 10-year interval. The PSI/ISI scenario is therefore PSI plus one 10-year ISI examination to be followed by two 30-year ISI deferrals (PSI+10+40+70).

The results of the PFM evaluation assuming 100% inspection coverage are presented in Table 7 of Attachment 4. As shown in this table, the probabilities of rupture and leakage are all below the NRC acceptance criterion of 1.0x10-6 after 80 years of plant operation by at least three orders of magnitude.

Enclosure Relief Request 74 12 In the sensitivity studies performed in References [9.1, 9.2], fracture toughness and stress were found to be the critical parameters. It was shown in Tables 8-13 through 8-16 of Reference [9.1] that by reducing the fracture toughness to 80 ksi and increasing all stresses (including transient stresses) by a factor of 2.2, the acceptance criterion is still met. Similarly, in Tables 8-12, 8-14, 8-16 and 8-18 of Reference [9.2], it was shown that by reducing the fracture toughness to 80 ksi¥in and increasing all stresses (including transient stresses) by a factor of 1.25, the acceptance criterion is met. The base cases used in these sensitivity studies have higher probabilities of rupture and leakage than those determined for the Palo Verde-specific System 80 SG components shown in Table 7 of Attachment 4. Hence, it follows that the same sensitivity studies for the Palo Verde components would also result in favorable results compared to the acceptance criterion.

Some Palo Verde System 80 SG components have limited inspection coverage. From, the minimum coverage for the SGs at the three Palo Verde units is associated with an examination performed on an Item No. B2.31 component at Unit 3, which had an inspection coverage of 59.5%. An evaluation was performed in Reference

[9.20] to address coverage of SG components on a generic basis. It was determined in Table 4 of Reference [9.20] that coverage as low as 25% is acceptable. The coverages for all PVNGS SG components are above this value and are therefore acceptable.

Pressurizers Flaw tolerance evaluations were performed in Reference [9.3] consisting of PFM evaluations and confirmatory DFM evaluations. Since the Westinghouse pressurizer configuration considered in Reference [9.3] is bounding relative to the CE pressurizer design, the results of the flaw tolerance evaluation can be conservatively applied to the Palo Verde pressurizer. The results of the PFM analyses indicate that, after PSI followed by subsequent ISI, the NRC safety goal of 1.0x10-6 failures per year is met.

The PFM analysis in Reference [9.3] was performed using the PRobabilistic OptiMization of InSpEction (PROMISE) Version 1.0 software, developed by Structural Integrity Associates. As part of the NRCs review of Southern Nuclears alternative request, the NRC performed an audit of the PROMISE Version 1.0 software as discussed in the NRCs audit plan dated May 14, 2020 (ADAMS Accession No. ML20128J311). The PFM analysis in Reference [9.3] was performed using the PROMISE Version 2.0 software which has not been audited by the NRC. The only technical difference between the two versions is that in PROMISE Version 1.0, the user-specified examination coverage is applied to all inspections, whereas in PROMISE Version 2.0, the examination coverage can be specified by the user uniquely for each inspection. In both Versions 1.0 and 2.0, the software assumes 100% coverage for the PSI examination. The NRC staff found the use PROMISE Version 2.0 acceptable in Section 3.1, page 5, fourth paragraph of the Reference [9.15] SE for Salem. Note that the assumption below of a 30-year ISI deferral is conservative compared to the end of currently licensed operating life for Palo Verde.

For the Palo Verde pressurizers, PSI examinations have been performed followed by ISI examinations for three complete ISI intervals. The PSI/ISI scenario for the Palo Verde pressurizers is therefore (PSI+10+20+30+60). This scenario was not specifically considered in the Reference [9.3] PFM evaluations in combination with key variables, as evaluated by the NRC in Section 4.0 (page 6) of the Reference [9.15] SE. Therefore, a new PFM evaluation was performed for this PSI/ISI scenario using PROMISE Version 2.0, the same version used for the evaluations in Reference [9.3]. The evaluations were

Enclosure Relief Request 74 13 performed for the critical Case ID from Reference [9.3] (PRSHC-BW-2C) with a combination of the most dominant parameters (stress and fracture toughness) as identified by the NRC in Section 4.0 (page 6) and Section 10 (page 19) of Reference

[9.12].

Since all welds under consideration are shell welds, a flaw density of 1.0 was used in the evaluation. This flaw density value was found acceptable by the NRC in Section 9.6 of Reference [9.15]. A fracture toughness of 200 ksi¥in with a standard deviation of 5 ksi¥in was used, as recommended by the NRC in Section 10 (page 19) of Reference [9.15]. A stress multiplier of 2.1 was used in the evaluation. This stress multiplier was conservatively chosen such that probability of rupture or leakage will be close to the NRC acceptance criterion of 1.0x10-6 after 80 years. As discussed above, a stress multiplier of 0.82 can be applied to the Palo Verde pressurizer components and therefore the stress multiplier of 2.1 used in the evaluation is very conservative. The results of the evaluation are presented in Table 3.

Table 3. Sensitivity to Combined Effects of Fracture Toughness, Stress, and Weld Flaw Density for 80 Years for the Palo Verde Pressurizer Welds (Case ID PRSHC-BW-2C from Reference [9.1])

Time (year)

Probability per Year for Combined Case KIC = 200 ksi¥in.,

SD = 5 ksi¥in.

Stress Multiplier = 2.1 Nozzle Flaw Density = 1 PSI+10+20+30+60 Rupture Leak 10 3.90E-07 1.00E-08 20 3.55E-07 5.00E-09 30 2.40E-07 3.33E-09 40 1.80E-07 2.50E-09 50 1.44E-07 2.00E-09 60 1.23E-07 1.67E-09 70 1.06E-07 1.43E-09 80 9.25E-08 1.25E-09 The plant-specific PFM evaluation presented above for Palo Verde indicates that with conservative inputs of the critical parameters, the probabilities of rupture and leakage are well below the NRC acceptance criterion of 1.0x10-6 failures per year. The stress multiplier applied in Table 3 is greater than the Palo Verde Ri/t ratio shown in Table 1 relative to that of the model used in the EPRI report and therefore the analysis in Table 3 is conservative. It should be noted that the evaluation incorporates a conservative assumption with regard to the PSI/ISI scenarios in that the partial-interval examinations performed during the 4th ISI interval are not credited. Furthermore, the evaluation was performed for 80 years, which his longer than the deferral being sought by APS in this Request for Alternative.

In the PFM evaluations in Reference [9.3], the PVRUF initial flaw size distribution was used. This distribution is applicable to thick vessels and not to relatively thin vessels like

Enclosure Relief Request 74 14 pressurizers. This issue was raised by the NRC in RAI No. 4 in Reference [9.16]. In response to this RAI, various initial flaw size distributions were used in a sensitivity study

[9.15] which showed that regardless of which distribution was used, the conclusions of Reference [9.3] remain the same. This was found acceptable by the NRC in Section 9.1, page 15, last paragraph of the SE for Salem [9.15].

An evaluation was performed to show acceptability of the low KIC values at the beginning and ending of the heatup/cooldown transient to address the NRC RAI No. 4 for PSEG in Reference [9.16], using the maximum RTNDT value of 60oF allowed by BTP 5-3 [9.17].

The RTNDT value of 60oF bounds the limiting RTNDT value of 40oF in Attachment 1 for the pressurizer materials at Palo Verde. The evaluation was performed for the most critical Case ID (PRSHC-BW-2C) from Reference [9.3], similar to that performed in Reference

[9.18] to respond to RAI 1 in Reference [9.16]. The three flaw sizes evaluated in the PSEG RAI response are also considered. The results are shown Figure 1. As seen in this figure, the calculated applied stress intensity factors are bounded with margin by the corresponding KIC calculated as a function of temperature (based on an RTNDT of 60oF) throughout the transient, for all three flaw depths. The heatup/cooldown transient also includes the leak test; hence, this addresses the adequacy of the temperature of the leak test to ensure that the applied stress intensity factor is below the fracture toughness during the leak test.

Figure 1. Applied K vs. Fracture Toughness as a Function of Temperature for Case ID PRSHC-BW-2C (RTNDT = 60oF)

The DFM evaluation in Table 8-4 of Reference [9.3] provides verification of the above PFM results for Palo Verde by demonstrating that it takes approximately 80 years for a postulated flaw with an initial depth equal to ASME Code,Section XI acceptance standards to grow to a depth where the maximum stress intensity factor (K) exceeds the ASME Code,Section XI allowable fracture toughness.

Inspection History As described in Section 8.2.4.1.1 of Reference [9.1], Section 8.3.4.1 of Reference [9.2],

Section 8.3.4.1 of Reference [9.3] and Section 8.3.2.8 of Reference [9.4], PSI refers to the superset of the examinations required by ASME Code,Section III during fabrication

Enclosure Relief Request 74 15 and any ASME Code,Section XI examinations performed prior to service. The Section III fabrication examinations required for these components were robust, and any Section XI preservice examinations further contributed to thorough initial examinations.

Inspection history for the Palo Verde SG and pressurizer components (including examinations performed to date, examination findings, inspection coverage, and relief requests) is presented in Attachment 2. As shown in Attachment 2, no flaws that exceeded the ASME Code,Section XI acceptance standards were identified during any examinations.

Steam Generators As shown in the attachment, the minimum examination coverage for the Palo Verde SG components is 59.5%, which is associated with an examination performed on Item No.

B2.31 component at Unit 3. This coverage is greater than the minimum coverage of 25% justified in Reference [9.20].

Pressurizers As shown in the attachment, the minimum examination coverage for the Palo Verde pressurizer components is 65%, which is greater than the 37% determined to be acceptable per Section 10 of the Salem SE [9.155].

Industry Survey The inspection history for the subject SG and pressurizer components as obtained from an industry survey is presented in Attachment 5. The results of the survey indicate that these components are very flaw tolerant.

Performance Monitoring The NRC stated in ML23114A034 [9.22] that probabilistic fracture mechanics (PFM) is inherently risk-informed and consequently any submittal that uses PFM technology as its basis will be reviewed as a risk-informed submittal. Therefore, performance monitoring (PM) must be addressed in any submittals relying on PFM. An acceptable PM approach must provide:

Direct evidence of the presence and/or extent of degradation; Validation and confirmation of continued adequacy of analysis; and A timely method to detect novel or unexpected degradation.

Also, in ML23114A034 [9.22] and ML23158A180 [9.23], the NRC stated that a PM sample of 25% would yield acceptable results, under certain assumptions, for the US fleet of 61 PWRs using a binomial distribution. It was noted that a smaller PM sample may be acceptable using a Monte Carlo analysis method. This PM sample would result in a 75% examination reduction compared to current ASME Code,Section XI examination requirements. Since this proposed alternative relies on PFM as part of the technical basis and the requested deferral period is greater than 20 years for some of

Enclosure Relief Request 74 16 the SG and pressurizer components, APSs proposed PM plan is provided below.

Steam Generators The PM plan for the SGs at Palo Verde is provided separately for the current on-going 4th inspection interval and the successive (5th and 6th) inspection intervals.

Current 4th Inspection Interval As shown in Table 4 below, Palo Verde Units 1, 2 and 3 have collectively completed 38 SG examinations (51% of the required 75 examinations) in the 4th interval to-date. This is more than the 25% sampling required under the NRC binomial distribution model.

Table 4. Palo Verde SG 4th Interval Section XI Examination Requirements and Completion Status Note: ASME Section XI Item B-D, B3.130 is applicable to primary steam generator nozzles on each steam generator or a total of six nozzles.

The SG examinations completed during the current, and previous, inspection intervals serve as sufficient PM to support the proposed alternative for the remainder of the current 4th interval for the Palo Verde Units 1, 2 and 3. The examinations performed during the current and previous inspection intervals provide direct evidence of the absence of any service-induced degradation, validate the adequacy of the PFM analysis, and confirm the absence of any novel or unexpected degradation. Therefore, no additional SG examinations will be performed during the current 4th inspection interval for any of the Palo Verde units. This PM plan is consistent with that of the Constellation Energys PWR SGs in ML23284A259 [24] which was approved by the NRC in ML24179A326 [25].

Successive 5th and 6th Inspection Intervals The proposed performance monitoring plan for the SGs, applicable to the 5th and 6th ISI intervals, is for 1 out of the 3 Palo Verde units to complete the required ASME Code,Section XI SG examinations on a single SG during each of these intervals (5th and 6th Interval) in addition to the two SG tubesheet blowdown nozzles in the other units. The proposed SG exam population would be 26 of the 75 exams required per interval. This represents a 34.6% performance monitoring sampling percentage for Palo Verde during these intervals, which is greater than the 25% sampling for adequate PM consistent with Required Completed Pending Required Completed Pending Required Completed Pending B-B B2.31 1

1 0

1 0

0 1

1 0

B-B B2.40 2

1 1

2 0

0 2

2 0

B-D B3.130 6

4 2

6 2

0 6

4 0

C-A C1.10 2

0 2

2 0

0 2

0 0

C-A C1.20 1

1 0

1 1

0 1

1 0

C-A C1.30 1

1 0

1 0

0 1

1 0

C-B C2.21 8

4 4

8 4

0 8

4 0

C-B C2.22 4

2 2

4 2

0 4

2 0

Total 75 38 51%

Percentage of 4th Interval SXI Exams Completed Unit 2 Unit 3 Palo Verde SG 4th Interval Section XI Examination Requirements and Completion Status 9

25 15 Item No.

Unit 1 25 14 25 Exams Required Exams Completed ASME Cat.

Enclosure Relief Request 74 17 use of the NRC binomial distribution model, as described in ML23033A667 [9.21] and ML23114A034 [9.22]. The selected unit will distribute the PM examinations across the periods as required by Table IWB-2411-1 or Table IWC-2411-1, as applicable. This will ensure continuous collection of data and allow for timely identification of any service-induced degradation or the emergence of any novel degradation mechanisms. This PM plan is consistent with that of the Constellation Energys PWR SGs in ML23284A259

[24] which was approved by the NRC in ML24179A326 [25].

Pressurizers The PM plan for the pressurizers at Palo Verde is provided separately for the current on-going 4th inspection interval and the successive (5th and 6th) inspection intervals.

Current 4th Inspection Interval As shown in Table 5 below, Palo Verde Units 1, 2 and 3 have collectively completed 12 pressurizer examinations (33% of the required 36 examinations) in the 4th interval to-date. This is more than the 25% sampling required under the NRC binomial distribution model.

Table 5. Palo Verde Pressurizer 4th Interval Section XI Examination Requirements and Completion Status The pressurizer examinations completed during the current, and previous, inspection intervals serve as sufficient PM to support the proposed alternative for the remainder of the current 4th interval for the Palo Verde Units 1, 2 and 3. The examinations performed during the current and previous inspection intervals provide direct evidence of the absence of any service induced degradation, validate the adequacy of the PFM analysis, and confirm the absence of any novel or unexpected degradation. Therefore, no additional pressurizer examinations will be performed during the current 4th inspection interval for any of the Palo Verde units.

Successive 5th and 6th Inspection Intervals The proposed performance monitoring plan for the pressurizers, applicable to the 5th and 6th ISI intervals, is for 1 out of the 3 Palo Verde units to complete all required ASME Code,Section XI pressurizer examinations during each of these intervals. This represents a 33.3% PM sampling percentage for Palo Verde during these intervals, which is greater than the 25% sampling for adequate PM consistent with use of the NRC binomial distribution model described in ML23033A667 [9.21] and ML23114A034 [9.22].

Required Completed Pending Required Completed Pending Required Completed Pending B-B B2.11 2

1 1

2 1

0 2

1 0

B-B B2.12 4

2 2

4 2

0 4

2 0

B-D B3.110 6

1 5

6 1

0 6

1 0

Total 36 12 33%

Exams Required 12 12 12 Palo Verde PZR 4th Interval Section XI Examination Requirements and Completion Status ASME Cat. Item No.

Unit 1 Unit 2 Unit 3 Exams Completed 4

4 4

Percentage of 4th Interval SXI Exams Completed

Enclosure Relief Request 74 18 The selected unit will distribute the PM examinations across the periods as required by Table IWB-2411-1. This will ensure continuous collection of data and allow for timely identification of any service-induced degradation or the emergence of any novel degradation mechanisms. This PM plan is consistent with that of the Constellation Energys Braidwood and Byron units pressurizers in ML24082A185 [26] which was approved by the NRC in ML24194A022 [27].

Scope Expansion During PM Examinations (Applicable to Both SG and PZR Components)

If any new unacceptable indications (i.e., new indications exceeding the acceptance standards of IWB-3500 or IWC-3500, and accepted by analytical evaluation or Repair/Replacement Activity) are identified during the PM examinations, the indications will be evaluated as required by ASME Code,Section XI and the APS corrective action program. The additional examination and successive inspection requirements of ASME Code,Section XI also apply. The number of additional examinations to be performed during the current refueling outage shall be the number of PM examinations included in the inspection item number that were scheduled to be performed during the current inspection period. If additional unacceptable indications are identified, the examinations shall be further expanded to include all remaining welds/components in the inspection item number at the selected Palo Verde unit. Any new unacceptable indications identified as part of the PM examinations at the selected Palo Verde unit will result in all three units reverting to ASME Code,Section XI examination requirements for the remainder of the interval during which the unacceptable indications are identified. ASME Code,Section XI examinations shall resume no later than the first or second refueling outage following discovery of the initial unacceptable indication. The same weld/component with the initial unacceptable indication shall be included for examination at the remaining Palo Verde units within the first or second refueling outage following discovery. If the unacceptable indication is identified during the 5th inspection interval, and no further unacceptable indications are identified during the resumption of ASME Code,Section XI examinations, then the proposed alternative may continue to be applied for the 6th inspection interval for all Palo Verde units. This scope expansion plan is consistent with that of the Constellation Energys PWR SGs in ML23284A259

[24] which was approved by the NRC in ML24179A326 [25].

Conclusion It is concluded that the SG and pressurizer pressure-retaining welds and full penetration welded nozzles are very flaw tolerant. PFM and DFM evaluations performed as part of the technical basis reports [9.1] through [9.4], supplemented by plant-specific evaluations performed as part of this Request for Alternative, demonstrate that using conservative PSI/ISI inspection scenarios for all plants, the NRC safety goal of 1.0x10-6 failures per reactor year is met with considerable margins. Plant-specific applicability of the technical basis to Palo Verde is demonstrated in Attachments 1 through 4. The requested ISI deferrals provide an acceptable level of quality and safety in lieu of the current ASME Code,Section XI 10-year inspection frequency.

Operating and examination experience demonstrates that these components have performed with very high reliability, mainly due to their robust design. In addition to the required PSI examinations for these SG and pressurizer welds, Palo Verde has performed multiple ISI examinations through the current 10-year inspection interval at each plant. Attachment 2 shows the examination history for the SG and pressurizer

Enclosure Relief Request 74 19 welds examined in the two most recent 10-year inspection intervals. Examination coverage for Palo Verde was greater than the minimum percentages established in the references cited. No flaws that exceeded the ASME Code,Section XI acceptance standards were identified during any examinations, as shown in Attachment 2.

As required by the NRC, a PM plan has been included to provide direct evidence of the absence of any service induced degradation, validate the adequacy of the PFM analysis, and confirm the absence of any novel or unexpected degradation.

In addition, it is important to note all other inspection activities, including the system leakage test (Examination Categories B-P and C-H) will continue to be performed in accordance with the ASME Code,Section XI requirements, providing further assurance of safety.

Finally, as discussed in Reference [9.19], for situations where no active degradation mechanism is present, it was concluded that subsequent ISI examinations do not provide additional value after PSI has been performed and the inspection volumes have been confirmed to be free of defects.

Therefore, APS requests the NRC grant this proposed alternative in accordance with 10 CFR 50.55a(z)(1).

DURATION OF PROPOSED ALTERNATIVE:

The proposed alternative is to defer the ISI examinations for these Item Nos. for the SGs and pressurizers at Palo Verde from the current ASME Code,Section XI, Division 1 10-year requirement to for the remainder of the 4th interval, the 5th and 6th intervals to the end of operating license scheduled for June 1, 2045, for Unit 1, April 24, 2046, for Unit 2 and November 25, 2047, for Unit 3.

PRECEDENTS:

The following previous submittal has been made by PSEG Nuclear to provide relief from the ASME Code,Section XI, Examination Category B-B (Item Nos. B2.11 and B2.12) and Category B-D (Item No. B3.110) surface and volumetric examinations based on the Reference 9.1 technical basis report:

Letter from Paul R. Duke, Jr. (PSEG Nuclear) to USNRC, Proposed Alternative for Examination of ASME Section XI, Examination Category B-B, Item Number B2.11 and B2.12, dated August 5, 2020, ADAMS Accession No. ML20218A587

[9.15].

The USNRC issued an SE of the PSEG Nuclear request for alternative on April 12, 2021.

Letter from James G. Danna (USNRC) to Eric. Carr (PSEG Nuclear), Salem Generating Station Unit Nos. 1 and 2 - Authorization and Safety Evaluation for Alternative Request No. SC-I4R-200 (EPID L-2020-LLR-0103), dated April 12, 2021, ADAMS Accession No. ML20218A587 [9.16].

The following is a list of other Relief Requests and other precedents related to inspections of pressurizer welds and components:

Enclosure Relief Request 74 20 Letter from M. G. Kowal (NRC) to M. A. Balduzi (Entergy Nuclear Operations, Inc.), Indian Point Nuclear Generating Unit No. 2 - Relief Request No. RR-01 (TAC No. MD4695), dated September 5, 2007, ADAMS Accession No. ML072130487.

Letter from T. L. Tate (NRC) to Vice President, Operations (Entergy Nuclear Operations, Inc.), Indian Point Nuclear Generating Unit No. 2 - Safety Evaluation for Relief Request No. IP2-ISI-RR-01 (CAC No. MF082), dated September 14, 2016, ADAMS Accession No. ML16179A178.

Letter from H. K. Chemoff (NRC) to D. A. Heacock (Dominion Nuclear Connecticut, Inc.), Millstone Power Station Unit No. 3 - Issuance of Relief Request IR-2-51 through IR-2-60 Regarding Second 10-Year Interval Inservice Inspection Program Plan (TAC Nos. ME3809 through ME3818), dated April 26, 2011, ADAMS Accession No. ML110691154.

Letter from R. L. Emch (NRC) to J. B. Beasley Jr. (Southern Nuclear Operating Company, Inc.), Second Ten-Year Interval Inservice Inspection Program Plan Requests for Relief 13, 14, 15, 21 and 33 for Vogtle Electric Generating Plant Units 1 and 2 (TAC No. MB0603 and MB0604), dated June 20, 2001, ADAMS Accession No. ML011640178.

Letter from N. DiFrancesco (NRC) to M. J. Pacilio (Exelon Nuclear), Braidwood Station Units 1 and 2 - Relief from Requirements of the ASME Code for the Third 10-Year Interval of Inservice Inspection (TAC Nos. ME9748 and ME9749), dated January 30, 2013, ADAMS Accession No. ML13016A515.

Letter from E. C. Marinos (NRC) to D. Jamil (Duke Power Company LLC)),

Catawba Nuclear Station, Unit 1 - Request for Relief 05-CN-004, Limited Weld Examinations During End-of-Cycle 15 Refueling Outage (TAC Nos. MC8337, MC9171, MC9172, MC9173, MC9174, MC9175, MC9176, MC9177, MC9178, and MC9179), dated September 25, 2006, ADAMS Accession No. ML062390020.

Letter from J. Boska (NRC) to K. Henderson (Duke Energy Carolinas, LLC)),

Catawba Nuclear Station, Units 1 and 2 - Proposed Relief Request 11-CN-001 for the Third 10-Year Inservice Inspection Interval (TAC Nos. ME7277, ME7278, ME7279, ME7280, ME7281, ME7282, AND ME7283), dated August 20, 2012, ADAMS Accession No. ML12228A723.

Letter from R. J. Pascarelli (NRC) to K. Henderson (Duke Energy Carolinas, LLC)), Catawba Nuclear Station, Units 1 and 2 - Proposed Relief Request 14-CN-001, American Society of Mechanical Engineers (ASME)Section XI Volumetric Examination Requirements (TAC Nos. MF3527 AND MF3528), dated October 30, 2014, ADAMS Accession No. ML14295A532.

Letter from R. T. Repko (Duke Energy Carolinas, LLC) to NRC, Duke Energy Carolinas, LLC (Duke Energy), McGuire Nuclear Station Units 1 and 2, Docket Nos. 50-369 and 50-370, Relief Request Serial # 11-MN-001, Limited Weld Examinations for Refueling Outage 1EOC20 and 2EOC19, dated September 21, 2011, ADAMS Accession No. ML11279A035.

Letter from J. A. Price (Dominion Nuclear Connecticut, Inc.) to NRC, Dominion Nuclear Connecticut, Inc., Millstone Power Station Unit 3, ASME Section XI Inservice Inspection Program, Relief Requests for Limited Coverage Examinations Performed in the Second 10-Year Inspection Interval, dated April 19, 2010, ADAMS Accession No. ML101130187.

Letter from D. H. Corlett (Progress Energy) to NRC, Shearon Harris Nuclear Power Plant, Unit No. 1, Docket No. 50-400/License No. NPF-63, Second Ten Year Interval Inservice Inspection Program - Final Documentation Including

Enclosure Relief Request 74 21 Requests for Relief in Accordance with 10 CFR 50.55a, dated February 5, 2009, ADAMS Accession No. ML090540055.

Letter from D. H. Corlett (Progress Energy) to NRC, Shearon Harris Nuclear Power Plant, Unit No. 1, Docket No. 50-400/Renewed License No. NPF-63, Response to Request for Additional information Regarding Relief Requests 2R1-018, 2R1-019, 2R1-020, 2R1-021, 2R1-022, 2R2-009, 2R2-010, AND 2R2-011 for the Second Ten Year Interval Inspection Program (TAC Nos. ME0608, ME0609, ME0610, ME0166, ME0612, ME0613, ME0614, AND ME0615), dated September 24, 2009, ADAMS Accession No. ML092740063.

In addition, other studies have been performed by the industry to extend the inspection interval for various components and have been accepted by the NRC.

Based on studies presented in Reference [9.4], the NRC approved extending PWR reactor vessel nozzle-to-shell welds from 10 to 20 years in Reference [9.5].

Based on work performed in BWRVIP-108 [9.6] and BWRVIP-241 [9.8], the NRC approved the reduction of BWR vessel nozzle-to-shell weld examinations (Item No. B3.90 for BWRs from 100% to a 25% sample of each nozzle type every 10 years) in References [9.7] and [9.9]. The work performed in BWRVIP-108 and BWRVIP-241 provided the technical basis for ASME Code Case N-702 [9.10],

which has been conditionally approved by the NRC in Revision 18 of Regulatory Guide 1.147 [9.11].

REFERENCES:

9.1 Technical Bases for Inspection Requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Inside Radius Sections.

EPRI, Palo Alto, CA: 2019. 3002014590.

9.2 Technical Bases for Inspection Requirements for PWR Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head and Tubesheet-to-Shell Welds. EPRI, Palo Alto, CA: 2019. 3002015906.

9.3 Technical Bases for Inspection Requirements for PWR Pressurizer Head, Shell-to-Head, and Nozzle-to-Vessel Welds, EPRI, Palo Alto, CA: 2019. 3002015905.

9.4 Technical Bases for Inspection Requirements for PWT Steam Generator Auxiliary Feedwater Nozzle-to-Shell Welds, EPRI, Palo Alto, CA: 2022. 3002023713.

9.5 PZR and SG Materials.xlsx.

9.6 E-mail from David Van Allen (APS) to Scott Chesworth (SI) on Wed 7/17/2024 3:26 PM, RE: RSG design spec.

9.7 E-mail from David Van Allen (APS) to Scott Chesworth (SI) on Wed 7/17/2024 9:34 AM,

Subject:

RE: RSG design spec.

9.8 E-mail from David Van Allen (APS) to Scott Chesworth (SI) on Wed 7/17/2024 9:28 AM,

Subject:

RE: RSG design spec.

9.9 E-mail from Eric Stanistreet (APS) to Scott Chesworth (SI) on Wed 7/17/2024 9:54 AM,

Subject:

RSG design spec.

9.10 N. Palm (EPRI), BWR Vessel & Internals Project (BWRVIP) Memo No. 2019-016, White Paper on Suggested Content for PFM Submittals to the NRC, February 27, 2019, ADAMS Accession No. ML19241A545.

Enclosure Relief Request 74 22 9.11 USNRC Regulatory Guide 1.245, Revision 0, Preparing Probabilistic Fracture Mechanics Submittals, January 2022.

9.12 USNRC Report NUREG/CR-7278, Technical Basis for the use of Probabilistic Fracture Mechanics in Regulatory Applications, January 2022.

9.13 Letter from Michael T. Markley (USNRC) to Cheryl A. Gayheart (Southern Nuclear), Vogtle Electric Generating Plant, Units 1 & 2 - Relief Request for Proposed Inservice Inspection Alternative VEGP-ISI-ALT-04-04 to the Requirements of ASME Code (EPID L-2020-LLR-0109), dated January 11, 2021, ADAMS Accession No. ML20352A155.

9.14 Letter from James G. Danna (USNRC) to Daniel G. Stoddard (Dominion Energy),

Millstone Power Station Unit 2 - Authorization and Safety Evaluation for Alternative Request No. RR-05-06 (EPID L-2020-LLR-0097), dated July 16, 2021, ADAMS Accession No. ML21167A355.

9.15 Letter from James G. Danna (USNRC) to Eric Carr (PSEG Nuclear), Salem Generating Station Unit Nos. 1 and 2 - Authorization and Safety Evaluation for Alternative Request No. SC-I4R-200 (EPID L-2020-LLR-0103), dated April 12, 2021, ADAMS Accession No. ML20218A587.

9.16 Letter from James Kim (USNRC) to Paul R. Duke, Jr. (PSEG Nuclear), Requests for Additional Information Regarding Salem Generating Station Units Nos. 1 and 2 Regarding Alternative for Examination of ASME Section XI, Category B-B, Item Number B2.11 and B2.12, EPID L-2020-LRR-0103, dated February 11, 2021, ADAMS Accession No. ML21043A144.

9.17 NUREG-0800 - Chapter 5, Branch Technical Position (BTP) 5-3, Revision 2, Fracture Toughness Requirements.

9.18 Letter from Paul R. Duke, Jr. (PSEG Nuclear) to USNRC, Response to Request for Additional Information for Proposed Alternative for Examination of ASME Section XI, Examination Category B-B, Item Number B2.11 and B2.12, dated April 12, 2021, ADAMS Accession No. ML21102A024.

9.19 American Society of Mechanical Engineers, Risk-Based Inspection: Development of Guidelines, Volume 2-Part 1 and Volume 2-Part 2, Light Water Reactor (LWR)

Nuclear Power Plant Components. CRTD-Vols. 20-2 and 20-4, ASME Research Task Force on Risk-Based Inspection Guidelines, Washington, D.C., 1992 and 1998.

9.20 N. G. Cofie, D. Dedhia, S, T. Chesworth, D. J. Shim, and R. Grizzi, Technical Basis for Inspection Optimization and Deferral of PWR Steam Generator Component Examinations, Paper No. PVP2023-105958, Proceedings of the ASME 2023 Pressure Vessels & Piping Conference, PVP2023, July 16-21, 2023, Atlanta, Georgia, USA.

9.21 U S NRC, Performance Monitoring, U S NRC Public Meeting with Constellation Energy Generation, LLC, (Constellation) to Discuss its Requests for Alternatives for Certain Steam Generator Weld Inspections, January 30, 2023, ADAMS Accession No. ML23033A667.

9.22 U S NRC, Probabilistic Fracture Mechanics and Performance Monitoring, U S NRC Public Meeting, April 27, 2023, ADAMS Accession No. ML23114A034.

Enclosure Relief Request 74 23 9.23 D. Widrevitz, (USNRC), Performance Monitoring, Industry/NRC Materials Technical Exchange Meeting, June 14 and 15, 2023, Rockville MD., ADAMS Accession No. ML23158A180.

9.24 Letter No. RS-23-108 from D. T. Gudger (Constellation Generation Company, LLC) to USNRC, Proposed Alternative for Examinations of Examination Categories B-B, B-D, and C-A Steam Generator Pressure Retaining Welds and Full Penetration Welded Nozzles, dated October 11, 2023, ADAMS Accession No. ML23284A259.

9.25 Letter from J. A. Whited (USNRC) to D. P. Rhoades (Constellation Generation Company, LLC), Braidwood Station, Units 1 and 2; Byron Station, Unit Nos. 1 and 2; Calvert Cliffs Nuclear Power Plant, Units 1 and 2; and R. E. Ginna Nuclear Power Plant - Issuance of Relief Re: Proposed Alternative Request Associated with Steam Generator Examinations (EPIDS L-2023-LLR-0053, L-2023-LLR-0054, L-2023-LLR-0055, L-2023-LLR-0056), dated July 23, 2024, ADAMS Accession No. ML24179A326.

9.26 Letter No. RS-24-024 from M. D. Humphrey (Constellation Generation Company, LLC) to USNRC, Response to Request for Additional Information Regarding Proposed Alternative for Examination of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds (L-2023-LLR-0062), dated March 22, 2024, ADAMS Accession No. ML24082A185.

9.27 Letter from J. A. Whited (USNRC) to D. P. Rhoades (Constellation Generation Company, LLC), Braidwood Station, Units 1 and 2; Byron Station, Unit Nos. 1 and 2; - Issuance of Relief Re: Proposed Alternative Request Associated with Pressurizer Examinations (EPID L-2023-LLR-0062), dated July 22, 2024, ADAMS Accession No. ML24194A022.

Enclosure Relief Request 74 ATTACHMENT 1 PLANT-SPECIFIC APPLICABILITY FOR PRESSURIZERS

Enclosure Relief Request 74 1

Section 9 of Reference [1-1] provides requirements that must be demonstrated to apply the representative stress and flaw tolerance analyses to a specific plant. Plant-specific evaluation of these requirements for Palo Verde is provided in Table 1-1 and indicates that all plant-specific requirements are met. Therefore, the results and conclusions of the EPRI report are applicable to Palo Verde.

Table 1-1. Applicability of Reference [1-1] Representative Analyses to Palo Verde Pressurizer Surge Nozzle and Bottom Head Welds (Item Nos. B2.11, B2.12 and B3.110)

Category Requirement from Reference [1-1]

Applicability to Palo Verde General Requirements The plant-specific pressurizer general transients and cycles must be bounded by those shown in Table 5-6 for a 60-year operating life. It should be noted that the number of cycles were extrapolated to 80 years in the evaluations.

As shown in Table 1-3, the Palo Verde general transients are bounded by the transients listed in Table 5-6 of Reference [1-1].

The materials of the pressurizer surge nozzle, bottom head and shell must be low alloy ferritic steels which conform to the requirements of ASME Code,Section XI, Appendix G, Paragraph G-2110.

The Palo Verde pressurizer shell and bottom head are fabricated from SA-533 Grade B Class 1 material and the surge nozzle is fabricated from SA-541 Class 2 material (per Reference [1-2]).

The maximum RTNDT values for the plates and forgings at the three units are as follows:

Unit 1 Plates +20°F (Table 5.2-16 of Reference [1-3]

Forgings +40°F (Table 5.2-17 of Reference [1-3]

Unit 2 Plates -10°F (Table 5.2-16A of Reference [1-3]

Forgings +40°F (Table 5.2-17A of Reference [1-3]

Unit 3 Plates +20°F (Table 5.2-16B of Reference [1-3]

Forgings +30°F (Table 5.2-17B of Reference [1-3]

All components/ materials are therefore bounded by the value used in the EPRI report.

Both materials are low alloy ferritic

Enclosure Relief Request 74 2

Category Requirement from Reference [1-1]

Applicability to Palo Verde steels that conform to the requirements of ASME Code,Section XI, Appendix G, Paragraph G-2110. SA-533 Grade B Class 1 material is specified in Appendix G. SA-541 Class 2 material is not specified in Appendix G.

However, it is a low alloy steel with similar properties to SA-508-2 which is specified in Appendix G.

Specific Requirements The plant-specific pressurizer surge nozzle, bottom head and shell weld configurations must conform to those shown in Figure 1-1 (Item No.

B2.11) 1-2 (Item No. B2.12) and 1-4 (Item No.

B3.110) of Reference [1-1].

The Palo Verde pressurizer surge nozzle weld configuration is shown in Figure 1-2 and shows conformance with Figure 1-4 of Reference 1-1]. It is also confirmed that the Palo Verde Item No. B2.11 and B2.12 head and shell welds conform to those shown in Figures 1-1 and 1-2 of Reference [1-1].

An example B2.11 weld is shown in Figure 1-5.

The plant-specific dimensions of the pressurizer surge nozzle and shell must be within the range of values listed in Table 9-1 of Reference [1-1].

As shown in Table 1-2, the Palo Verde pressurizer shell and surge nozzle dimensions are within the range of values listed in Table 9-1 of Reference

[1-1].

The plant-specific Insurge/Outsurge transient definitions (temperature difference between the pressurizer shell and the pressurizer surge nozzle fluid temperature and associated number of cycles) must be bounded by those shown in Table 5-10 for a Westinghouse/CE plant, or Table 5-11 for a B&W plant of Reference [1-1].

As shown in Table 1-4, the Palo Verde Insurge/Outsurge transients are bounded by the transients listed in Table 5-10 of Reference [1-1].

Enclosure Relief Request 74 3

Pressurizer Top Head Welds (Item Nos. B2.11, B2.12 and B3.110)

Category Requirement from Reference [1-1]

Applicability to Palo Verde General Requirements The plant-specific pressurizer general transients and cycles must be bounded by those shown in Table 5-6 of Reference [1-1] for a 60-year operating life. It should be noted that the number of cycles were extrapolated to 80 years in the evaluations.

As shown in Table 1-3, the Palo Verde general transients are bounded by the transients listed in Table 5-6 of Reference [1-1].

The materials of the pressurizer top head nozzles, head and shell must be low alloy ferritic steels which conform to the requirements of ASME Code,Section XI, Appendix G, Paragraph G-2110.

The Palo Verde pressurizer top head and shell are fabricated from SA-533 Grade B Class 1 material and the top head nozzles are fabricated from SA-541 Class 2 material (per Reference

[1-2]).

Unit 1 Plates +20°F (Table 5.2-16 of Reference [1-3]

Forgings +40°F (Table 5.2-17 of Reference [1-3]

Unit 2 Plates -10°F (Table 5.2-16A of Reference [1-3]

Forgings +40°F (Table 5.2-17A of Reference [1-3]

Unit 3 Plates +20°F (Table 5.2-16B of Reference [1-3]

Forgings +30°F (Table 5.2-17B of Reference [1-3]

All material RTNDT values are bounded by the value used in the EPRI report.

Both materials are low alloy ferritic steels that conform to the requirements of ASME Code,Section XI, Appendix G, Paragraph G-2110. SA-533 Grade B Class 1 material is specified in Appendix G. SA-541 Class 2 material is not specified in Appendix G.

However, it is a low alloy steel with similar properties to SA-508-2 which is specified in Appendix G.

Enclosure Relief Request 74 4

Category Requirement from Reference [1-1]

Applicability to Palo Verde Specific Requirements The plant-specific pressurizer top head nozzles, head and shell weld configurations must conform to those shown in Figure 1-1 (Item No.

B2.11), 1-2 (Item No. B2.12) and 1-4 (Item No.

B3.110) of Reference [1-1].

The Palo Verde pressurizer spray nozzle and SRV nozzle weld configurations are shown in Figures 1-3 and 1-4, respectively, and show conformance with Figure 1-4 of Reference 1-1]. It is also confirmed that the Palo Verde Item No. B2.11 and B2.12 head and shell welds conform to those shown in Figures 1-1 and 1-2 of Reference [1-1]. An example B2.11 weld is shown in Figure 1-6.

The plant-specific dimensions of the pressurizer top head nozzles and shell must be within the range of values listed in Table 9-1 of Reference

[1-1].

As shown in Table 1-2, the Palo Verde pressurizer shell and top head nozzle dimensions are within the range of values listed in Table 9-1 of Reference

[1-1].

Table 1-2. Range of Geometric Parameters for which the Evaluation is Applicable in Comparison with Palo Verde Dimensions Component Geometric Parameter For a CE Plant (From Table 9-1 of Reference [1-1])

Palo Verde Dimension Pressurizer Shell Inside Diameter (in)

Must be between 90 and 102 96.38 [1-2]

Surge Nozzle NPS of piping or component (e.g.,

reducer) attached to nozzle safe-end (in) (1)

Must be between 10 and 14 12 (Table 5.4-37 of [1-3])

Safety/Relief Nozzle NPS of piping or component (e.g.,

reducer) attached to nozzle safe-end (in) (1)

Must be between 4 and 6 6 (Table 5.4-37 of [1-3])

Spray Nozzle NPS of piping or component (e.g.,

reducer) attached to nozzle safe-end (in) (1)

Must be between 4 and 6 4 (Table 5.4-37 of [1-3])

Note:

1. Depending on the plant-specific configuration, the NPS of the piping (or component) attached directly to the nozzle (i.e., no safe-end) or to a safe-end extension may be used.

Enclosure Relief Request 74 5

Table 1-3. Comparison of Palo Verde General Transients to Requirements in Reference [1-1]

Transient Number of Cycles for 60 Years from Table 5-6 of Reference [1-1]

Palo Verde Unit 1 60-Year Projection Palo Verde Unit 2 60-Year Projection Palo Verde Unit 3 60-Year Projection Heatup /

Cooldown 300 115 / 115(1) 110 / 108(3) 110 / 110(5)

Loss of Load (e.g., Large Step Load Decrease, Loss of Power, Loss of Flow, Reactor Trip, etc.)

360 117(2) 90(4) 87(6)

Notes:

1. Pressurizer Heatup / Pressurizer Cooldown, from Table 5 of Reference [1-4].

2. All Reactor Trips + Loss of Reactor Coolant System Flow, from Table 5 of Reference [1-4].

3. Pressurizer Heatup / Pressurizer Cooldown, from Table 5 of Reference [1-5].

4. All Reactor Trips + Loss of Reactor Coolant System Flow, from Table 5 of Reference [1-5].

5. Pressurizer Heatup / Pressurizer Cooldown, from Table 5 of Reference [1-8].

6. All Reactor Trips + Loss of Reactor Coolant System Flow, from Table 5 of Reference [1-8].

Table 1-4. Comparison of Palo Verde Insurge/Outsurge Transients to Requirements in Reference [1-1]

T (oF)(1)

Number of Cycles for 60 Years from Table 5-10 of Reference

[1-1](2)

Palo Verde Unit 1 60-Year Projection [1-9]

Palo Verde Unit 2 60-Year Projection [1-9]

Palo Verde Unit 3 60-Year Projection [1-9]

330 600 0

0 0

320 3,000 2,463 2,463 2,463 103 1,500 931 931 931 Notes:

1. T is the temperature difference between the pressurizer fluid temperature and the fluid temperature in the surge nozzle.

2. Applicable to Westinghouse and CE plants.

Enclosure Relief Request 74 6

Figure 1-1. Palo Verde Pressurizer Vessel [1-6]

Figure 1-2. Palo Verde Pressurizer Surge Nozzle (B3.110) Weld Detail [1-7]

Enclosure Relief Request 74 7

Figure 1-3. Palo Verde Pressurizer Spray Nozzle (B3.110) Weld Detail [1-7]

Figure 1-4. Palo Verde Pressurizer SRV Nozzle (B3.110) Weld Detail [1-7]

Enclosure Relief Request 74 8

Figure 1-5. Palo Verde Pressurizer Lower-Head to Shell Nozzle (B2.11) Weld Detail [1-10]

Figure 1-6. Palo Verde Pressurizer Upper-Head to Shell Nozzle (B2.11) Weld Detail [1-11]

Enclosure Relief Request 74 9

References 1-1.

Technical Bases for Inspection requirements for Pressurizer Vessel Head, Shell-to-Head and Nozzle-to-Vessel Welds. EPRI, Palo Alto, CA: 2019. 3002015905.

1-2.

PZR and SG Materials.xlsx.

1-3.

PVNGS Palo Verde Nuclear Generating Station Units 1, 2, and 3, Updated Final Safety Analysis Report, Revision 22A, February 2024.

1-4.

SI Calculation No. FP-PV-326, Palo Verde Unit 1 FP4 Update Through 11/1/2023-RFO 24, Revision 0.

1-5.

SI Calculation No. FP-PV-325, Palo Verde Unit 2 FP4 Update Through 4/30/2023-RFO 24, Revision 0.

1-6.

4INT-ISI-1 (PDF Page 91), Unit 1, Zone 5, Pressurizer, Rev. 1.

1-7.

APS Document No. 102-07950-MLL/MDD,

Subject:

Palo Verde Nuclear Generating Station Unit 1, Docket No. STN 50-528, Renewed Operating License Number NPF-41, Relief Request 64 - Unit 1 Impractical Examinations for the Third 10-Year Inservice Inspection Interval, July 17, 2019.

1-8.

SI Calculation No. FP-PV-324, Palo Verde 2022 Unit 3 FP4 Update Through 10/31/2022-RFO 23, Revision 0.

1-9.

SI Calculation No. 2300243.303, Palo Verde Pressurizer Insurge/Outsurge Transients, Revision 1.

1-10. Drawing No. 78373-641-001, Lower Vessel Assembly and Heater Holes, Arizona Public Service I 96 ID Pressurizer, Revision 0.

1-11. Drawing No. 78373-601-001, Top Head Details & Assembly, Arizona Public Service I 96 ID Pressurizer, Revision 0.

Enclosure Relief Request 74 ATTACHMENT 2 EXAMINATION HISTORY

Enclosure Relief Request 74 1

The examination history of the Palo Verde pressurizers and replacement steam generators is provided in the tables below. Acceptable indications noted in the tables below are fabrication related indications and found to be code acceptable. ASME Section XI exams have not detected age related growth of the indications.

Table 2-1. Palo Verde Unit 1 Pressurizer Examination History Item No.

Component ID Exam Date Interval/

Period Exam Results(1)

Coverage Relief Request B2.11 5-2 10/14/1999 2nd/1st NRI 100%

n/a B2.11 5-2 10/20/2008 3rd/1st NRI 100%

n/a B2.11 5-2 10/13/2011 3rd/1st NRI 100%

n/a B2.11 5-2 4/19/2022 4th/2nd NRI 100%

n/a B2.12 5-3 10/14/1999 2nd/1st NRI 100%

n/a B2.12 5-3 10/13/2011 3rd/1st NRI 100%

n/a B2.12 5-3 4/20/2022 4th/2nd NRI 100%

n/a B2.12 5-4 10/13/2011 3rd/1st NRI 100%

n/a B2.12 5-4 4/20/2022 4th/2nd NRI 100%

n/a B2.12 5-6 4/23/2016 3rd/3rd NRI

>90%

n/a B2.12 5-6 10/21/2002 2nd/2nd NRI 100%

n/a B2.12 5-7 4/23/2016 3rd/3rd NRI

>90%

n/a B2.11 5-8 10/21/2002 2nd/2nd NRI 100%

n/a B2.11 5-8 10/21/2008 3rd/1st NRI 100%

n/a B2.11 5-8 4/23/2016 3rd/3rd NRI 97.6%

n/a B3.110 5-9 4/11/2001 2nd/1st NRI 94.5%

n/a B3.110 5-9 5/12/2016 3rd/3rd NRI 65%

RR 64 B3.110 5-9 4/16/2022 4th/2nd NRI 65.2%

n/a B3.110 5-10 10/22/2002 2nd/2nd NRI 100%

n/a B3.110 5-10 4/9/2013 3rd/2nd NRI 81%

RR 64 B3.110 5-11 4/9/2001 2nd/1st NRI 92%

n/a B3.110 5-11 10/12/2011 3rd/1st NRI 75%

RR 64 B3.110 5-12 10/21/2008 3rd/1st NRI 75%

RR 64 B3.110 5-12 10/12/2011 3rd/1st NRI 75%

RR 64 B3.110 5-13 10/21/2002 2nd/2nd NRI 100%

n/a B3.110 5-13 4/4/2013 3rd/2nd NRI 75%

RR 64 B3.110 5-14 10/21/2008 3rd/1st NRI 75%

RR 64 B3.110 5-14 5/5/2016 3rd/3rd NRI 75%

RR 64 Notes:

1. NRI = no recordable indications; AI = indications identified but determined to be acceptable.

Enclosure Relief Request 74 2

Table 2-2. Palo Verde Unit 1 RSG Examination History Item No.

Component ID Exam Date Interval/

Period Exam Results(1)

Coverage Relief Request B3.130 3-100 4/6/2010 3rd/1st AI 93.1%(2) n/a B3.130 3-100 10/13/2020 4th/1st AI 93.1%

n/a B3.130 3-101 10/16/2017 3rd/3rd NRI 92.7%(2) n/a B3.130 3-101 10/17/2023 4th/2nd NRI 92.7%

n/a B3.130 3-102 10/16/2017 3rd/3rd NRI 92.7%(2) n/a B3.130 3-102 10/17/2023 4th/2nd NRI 92.7%

n/a B2.40 3-107 10/20/2023 4th/2nd NRI 100%

n/a B2.31 3-108 10/14/2023 4th/2nd NRI 91.8%

n/a B3.130 4-100 4/6/2010 3rd/1st NRI 95%

n/a B3.130 4-100 10/14/2020 4th/1st AI 93.1%

n/a B3.130 4-101 10/26/2014 3rd/2nd NRI 92.7%(2) n/a B3.130 4-102 10/26/2014 3rd/2nd NRI 92.7%(2) n/a B2.40 4-106 4/16/2016 3rd/3rd AI 100%

n/a B2.40 4-107 10/25/2014 3rd/2nd NRI

>90%

n/a B2.31 4-108 10/25/2014 3rd/2nd NRI

>90%

n/a C2.21 41-102 10/20/2017 3rd/3rd NRI 70%

no C2.21 41-102 10/20/2023 4th/2nd NRI 100%

n/a C2.22 41-102-IR 10/19/2017 3rd/3rd NRI 96.9%

n/a C2.22 41-102-IR 10/19/2023 4th/2nd NRI 100%

n/a C2.21 41-103 10/20/2017 3rd/3rd NRI 70%

no C2.21 41-103 10/20/2023 4th/2nd NRI 100%

n/a C2.22 41-103-IR 10/19/2017 3rd/3rd NRI 96.9%

n/a C2.22 41-103-IR 10/19/2023 4th/2nd NRI 100%

n/a C1.30 41-104 10/19/2017 3rd/3rd AI 96.8%

n/a C1.10 41-105 10/19/2017 3rd/3rd NRI 100%

n/a C1.10 41-106 10/23/2017 3rd/3rd AI 100%

n/a C1.20 41-107 10/20/2017 3rd/3rd AI 100%

n/a C1.20 41-107 4/30/2022 4th/2nd NRI 100%

n/a C2.21 41-109 10/20/2017 3rd/3rd NRI 100%

n/a C2.21 41-110 10/13/2017 3rd/3rd NRI 100%

n/a C2.21 41-114 10/21/2017 3rd/3rd NRI 100%

n/a C2.21 41-114 4/30/2022 4th/2nd NRI 100%

n/a C2.21 41-115 10/21/2017 3rd/3rd NRI 100%

n/a C2.21 41-115 4/30/2022 4th/2nd NRI 100%

n/a C2.21 42-102 10/25/2014 3rd/2nd NRI

>90%

n/a C2.21 42-103 10/25/2014 3rd/2nd NRI

>90%

n/a Notes:

1. NRI = no recordable indications; AI = indications identified but determined to be acceptable.

2. Revised examination coverage per Level 3 Evaluation Report No. 18-02415-001 (3/14/2018).

Enclosure Relief Request 74 3

Table 2-3. Palo Verde Unit 2 Pressurizer Examination History Item No.

Component ID Exam Date Interval/

Period Exam Results(1)

Coverage Relief Request B2.11 5-2 4/7/1999 2nd/1st NRI 100%

n/a B2.11 5-2 10/9/2009 3rd/1st NRI 100%

n/a B2.11 5-2 10/15/2021 4th/1st NRI 100%

n/a B2.12 5-3 10/9/2009 3rd/1st NRI 100%

n/a B2.12 5-3 10/15/2021 4th/1st NRI 100%

n/a B2.12 5-4 10/15/2021 4th/1st NRI 100%

n/a B2.12 5-6 3/25/2002 2nd/2nd NRI 100%

n/a B2.12 5-6 4/24/2014 3rd/3rd NRI

>90%

n/a B2.12 5-7 4/24/2014 3rd/3rd NRI

>90%

n/a B2.11 5-8 3/25/2002 2nd/2nd NRI 96%

n/a B2.11 5-8 10/17/2006 2nd/3rd NRI 96%

n/a B2.11 5-8 4/24/2014 3rd/3rd NRI

>90%

n/a B3.110 5-9 10/12/2000 2nd/2nd NRI 90%

n/a B3.110 5-9 10/29/2009 3rd/1st NRI 65.2%

RR 58 B3.110 5-9 4/13/2017 3rd/3rd NRI 65.2%

RR 58 B3.110 5-9 10/20/2021 4th/1st NRI 65.2%

n/a B3.110 5-10 3/25/2002 2nd/2nd NRI 83%

n/a B3.110 5-10 4/11/2011 3rd/2nd NRI 80.8%

RR 58 B3.110 5-11 10/11/2000 2nd/2nd NRI

>90%

n/a B3.110 5-11 10/8/2009 3rd/1st NRI 74.7%

RR 58 B3.110 5-12 10/17/2006 2nd/3rd NRI 95%

n/a B3.110 5-12 4/17/2017 3rd/3rd NRI 74.7%

RR 58 B3.110 5-13 3/25/2002 2nd/2nd NRI 83%

n/a B3.110 5-13 4/11/2011 3rd/2nd NRI 74.7%

RR 58 B3.110 5-14 10/17/2006 2nd/3rd NRI 95%

n/a B3.110 5-14 4/17/2017 3rd/3rd NRI 74.7%

RR 58 Notes:

1. NRI = no recordable indications; AI = indications identified but determined to be acceptable.

Enclosure Relief Request 74 4

Table 2-4. Palo Verde Unit 2 RSG Examination History Item No.

Component ID Exam Date Interval/

Period Exam Results(1)

Coverage Relief Request B3.130 3-100 5/6/2008 3rd/1st NRI 93.1%(2) n/a B3.130 3-100 10/19/2021 4th/1st NRI 93.1%

n/a B3.130 3-101 10/31/2006 2nd/3rd NRI 100%

n/a B3.130 3-101 10/17/2012 3rd/2nd AI 92.7%(2) n/a B3.130 3-102 10/17/2012 3rd/2nd AI 92.7%(2) n/a B3.130 4-101 10/31/2006 2nd/3rd NRI 100%

n/a B3.130 4-101 10/28/2015 3rd/3rd AI 92.7%(2) n/a B3.130 4-102 10/28/2015 3rd/3rd AI 92.7%(2) n/a B2.31 4-105 10/29/2015 3rd/3rd AI 97.1%(2) n/a B2.40 4-106 10/16/2006 2nd/3rd AI 100%

n/a B2.40 4-106 10/29/2015 3rd/3rd NRI

>90%

n/a B2.40 4-107 10/29/2015 3rd/3rd AI

>90%

n/a C2.21 41-102 10/13/2006 2nd/3rd NRI 100%

n/a C2.21 41-102 10/16/2012 3rd/2nd NRI 100%

n/a C2.21 41-103 10/13/2006 2nd/3rd NRI 100%

n/a C2.21 41-103 10/16/2012 3rd/2nd NRI 100%

n/a C1.30 41-104 10/16/0212 3rd/2nd AI 96.8%

n/a C1.10 41-105 10/26/2006 2nd/3rd NRI 100%

n/a C1.10 41-105 4/21/2011 3rd/2nd AI 100%

n/a C1.10 41-106 10/27/2006 2nd/3rd AI 100%

n/a C1.10 41-106 4/19/2011 3rd/2nd NRI 100%

n/a C1.20 41-107 10/28/2006 2nd/3rd NRI 93.9%

n/a C1.20 41-107 4/18/2011 3rd/2nd NRI 100%

n/a C1.20 41-107 10/28/2021 4th/1st NRI 100%

n/a C2.21 41-109 4/22/2011 3rd/2nd NRI 100%

n/a C2.21 41-110 10/16/2012 3rd/2nd NRI 100%

n/a C2.21 41-114 10/28/2021 4th/1st NRI 100%

n/a C2.21 41-115 10/28/2021 4th/1st NRI 100%

n/a C2.21 42-114 10/26/2015 3rd/3rd NRI 100%(2) n/a C2.21 42-115 10/26/2015 3rd/3rd AI 100%(2) n/a Notes:

1. NRI = no recordable indications; AI = indications identified but determined to be acceptable.

2. Revised examination coverage per Level 3 Evaluation Report No. 18-02415-001 (3/14/2018).

Table 2-5. Palo Verde Unit 3 Pressurizer Examination History Item No.

Component ID Exam Date Interval/

Period Exam Results(1)

Coverage Relief Request B2.11 5-2 4/5/2000 2nd/1st NRI 100%

n/a B2.11 5-2 4/13/2006 2nd/3rd AI

>90%

n/a B2.11 5-2 10/16/2010 3rd/1st NRI 100%

n/a B2.11 5-2 4/16/2021 4th/2nd NRI 100%

n/a B2.12 5-3 4/5/2000 2nd/1st NRI 100%

n/a B2.12 5-3 10/16/2010 3rd/1st NRI 100%

n/a B2.12 5-3 4/16/2021 4th/2nd NRI 100%

n/a B2.12 5-4 10/16/2010 3rd/1st NRI 100%

n/a B2.12 5-4 4/16/2021 4th/2nd NRI 100%

n/a B2.12 5-6 4/5/2003 2nd/2nd NRI 91%

n/a B2.12 5-6 4/21/2015 3rd/3rd NRI 100%

n/a B2.12 5-7 4/21/2015 3rd/3rd NRI 100%

n/a B2.11 5-8 4/4/2003 2nd/2nd NRI 100%

n/a B2.11 5-8 4/9/2006 2nd/3rd NRI 96%

n/a

Enclosure Relief Request 74 5

Item No.

Component ID Exam Date Interval/

Period Exam Results(1)

Coverage Relief Request B2.11 5-8 4/15/2015 3rd/3rd NRI 96%

n/a B3.110 5-9 10/5/2001 2nd/2nd NRI

>90%

n/a B3.110 5-9 10/17/2016 3rd/3rd NRI 65.2%

RR 63 B3.110 5-9 10/15/2019 4th/1st NRI 65.2%

n/a B3.110 5-10 4/5/2003 2nd/2nd NRI 100%

n/a B3.110 5-10 10/19/2013 3rd/2nd NRI 80.8%

RR 63 B3.110 5-11 10/13/2001 2nd/2nd NRI

>90%

n/a B3.110 5-11 10/19/2010 3rd/1st NRI 74.7%

RR 63 B3.110 5-12 4/9/2006 2nd/3rd NRI 95%

n/a B3.110 5-12 10/22/2016 3rd/3rd NRI 74.7%

RR 63 B3.110 5-13 4/4/2003 2nd/2nd NRI 95%

n/a B3.110 5-13 10/18/2013 3rd/2nd NRI 74.7%

RR 63 B3.110 5-14 4/9/2006 2nd/3rd NRI 95%

n/a B3.110 5-14 10/19/2010 3rd/1st NRI 74.7%

RR 63 Notes:

1. NRI = no recordable indications; AI = indications identified but determined to be acceptable.

Enclosure Relief Request 74 6

Table 2-6. Palo Verde Unit 3 RSG Examination History Item No.

Component ID Exam Date Interval/

Period Exam Results(1)

Coverage Relief Request B3.130 3-100 4/16/2009 3rd/1st AI 93.1%(2) n/a B3.130 3-100 10/10/2019 4th/1st NRI 93.1%

n/a B3.130 3-101 10/19/2013 3rd/2nd NRI 92.7%(2) n/a B3.130 3-101 10/17/2022 4th/2nd NRI 92.7%

n/a B3.130 3-102 10/11/2013 3rd/2nd NRI 92.7%(2) n/a B3.130 3-102 10/17/2022 4th/2nd NRI 92.7%

n/a B2.40 3-106 10/18/2022 4th/2nd NRI 100%

n/a B2.40 3-107 10/21/2013 3rd/2nd NRI

>90%

n/a B2.40 3-107 10/17/2022 4th/2nd NRI

>90%

n/a B2.31 3-108 4/21/2018 3rd/3rd AI 96.5%

n/a B2.31 3-108 10/15/2022 4th/2nd NRI 96.5%

n/a B3.130 4-100 4/15/2009 3rd/1st AI 93.1%(2) n/a B3.130 4-100 10/11/2019 4th/1st NRI 93.1%

n/a B3.130 4-101 10/13/2016 3rd/3rd AI 92.7%(2) n/a B3.130 4-102 3/24/2012 3rd/2nd NRI 100%

n/a B3.130 4-102 10/13/2016 3rd/3rd AI 92.7%(2) n/a B2.40 4-106 10/13/2016 3rd/3rd AI 100%

n/a B2.40 4-107 3/28/2012 3rd/2nd NRI 100%

n/a C2.21 41-102 10/20/2022 4th/2nd NRI 100%

n/a C2.22 41-102-IR 3/24/2012 3rd/2nd NRI 100%

n/a C2.22 41-102-IR 10/20/2022 4th/2nd NRI 100%

n/a C2.21 41-103 3/24/2012 3rd/2nd NRI 100%

n/a C2.21 41-103 10/20/2022 4th/2nd NRI 100%

n/a C2.22 41-103-IR 3/24/2012 3rd/2nd NRI 100%

n/a C2.22 41-103-IR 10/20/2022 4th/2nd NRI 100%

n/a C1.30 41-104 10/22/2013 3rd/2nd AI

>90%

n/a C1.30 41-104 10/19/2022 4th/2nd NRI

>90%

n/a C1.10 41-105 3/26/2012 3rd/2nd NRI 100%

n/a C1.10 41-106 3/29/2012 3rd/2nd AI 100%

n/a C1.20 41-107 5/1/2021 4th/2nd NRI 100%

n/a C2.21 41-109 3/29/2012 3rd/2nd NRI 100%

n/a C2.21 41-110 3/28/2012 3rd/2nd NRI 100%

n/a C2.21 41-114 10/15/2016 3rd/3rd NRI 100%

n/a C2.21 41-114 5/1/2021 4th/2nd NRI 100%

n/a C2.21 41-115 10/15/2016 3rd/3rd NRI 100%

n/a C2.21 41-115 5/1/2021 4th/2nd NRI 100%

n/a Notes:

1. NRI = no recordable indications; AI = indications identified but determined to be acceptable.

2. Revised examination coverage per Level 3 Evaluation Report No. 18-02415-001 (3/14/2018).

Enclosure Relief Request 74 ATTACHMENT 3 SI CALCULATION NO. 2300243.301, FINITE ELEMENT MODEL DEVELOPMENT AND THERMAL/MECHANICAL STRESS ANALYSIS OF PVNGS UNITS 1, 2, 3 STEAM GENERATOR COMPONENTS, REVISION 0

s CALCULATION PACKAGE File No.: 2300243.301P Project No.: 2300243 Quality Program Type:

Nuclear Commercial PROJECT NAME:

PVNGS Inspection Optimization CONTRACT NO.:

PV1025387 CLIENT:

Arizona Public Service Co. (APS)

PLANT:

Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, 3 CALCULATION TITLE:

Finite Element Model Development and Thermal/Mechanical Stress Analysis of PVNGS Units 1, 2, 3 Steam Generator Components Document Revision Affected Pages Revision Description Project Manager Approval Signature & Date Preparer(s) &

Checker(s)

Signatures & Date 0

1 - 55 A A-2 Initial Issue Scott Chesworth 12/12/2024 Preparer:

Thomas M. Washko 12/12/2024 Checker:

Younes Marih 12/12/2024 1

6, 7, 8, 10, 14, 33, 34, 37, 43, 44 Incorporated additional discussion and clarifications as documented in APS Comment Form Scott Chesworth 4/14/2025 Preparer:

Scott Chesworth 4/14/2025 Checker:

Nathaniel Cofie 4/14/2025 2

8 Removed discussion of Tubesheet Blowdown Nozzle Components41-100, 41-101,42-100, and 42-101 since APS will not be seeking relief for these components using this technical basis Scott Chesworth 5/5/2025 Preparer:

Scott Chesworth 5/5/2025 Checker:

Nathaniel Cofie 5/5/2025 PROPRIETARY INFORMATION This document contains Structural Integrity; client; or supplier proprietary information. This document may not be disclosed, wholly or in part, to any third parties without the prior written consent of Structural Integrity Associates, Inc.

File No.: 2300243.301P Revision: 2 Page 2 of 55 F0306-01R4 This document contains Structural Integrity; client; or supplier proprietary information. This document may not be disclosed, wholly or in part, to any third parties without the prior written consent of Structural Integrity Associates, Inc.

PROPRIETARY INFORMATION NOTICE THIS DOCUMENT CONTAINS PROPRIETARY INFORMATION. THE CLIENT MAY USE THE INFORMATION CONTAINED IN THIS DOCUMENT SOLELY FOR THEIR OWN INTERNAL PURPOSES. IF THE DOCUMENT IS SUBMITTED TO THE NUCLEAR REGULATORY COMMISSION (NRC), STRUCTURAL INTEGRITY ASSOCIATES, INC. WILL PROVIDE PROPRIETARY AND NON-PROPRIETARY VERSIONS OF THE DOCUMENT FOR NRC USE ALONG WITH THE REQUIRED LETTER STATING THE PERMITTED USE BY THE NRC. THIS DOCUMENT MAY NOT BE DISCLOSED, WHOLLY OR IN PART, TO ANY THIRD PARTIES WITHOUT THE PRIOR WRITTEN CONSENT OF STRUCTURAL INTEGRITY ASSOCIATES, INC.

This entire document is considered Proprietary. Proprietary References are identified with a P in the SI File Number.

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Table of Contents 1.0 OBJECTIVE..............................................................................................................6 2.0 TECHNICAL APPROACH.........................................................................................6 2.1 Finite Element Model.....................................................................................6 2.2 Pressure / Thermal Stress Analyses..............................................................6 3.0 DESIGN INPUTS.......................................................................................................6 4.0 ASSUMPTIONS........................................................................................................7 5.0 CALCULATIONS.......................................................................................................8 5.1 Finite Element Model.....................................................................................8 5.1.1 Material Properties.........................................................................................8 5.2 Pressure / Thermal Stress Analyses..............................................................9 5.2.1 Thermal Heat Transfer Analyses....................................................................9 5.2.2 Thermal Stress Analyses.............................................................................10 5.3 Differences Between Units 1, 3 and Unit 2...................................................10 6.0 RESULTS OF ANALYSIS........................................................................................10

7.0 REFERENCES

........................................................................................................10 COMPUTER FILES LISTING...................................................................... A-1

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List of Tables Table 1. Dimensions Used in Model(1)................................................................................13 Table 2. Materials of Components Used in Model(1)(2).........................................................14 Table 3: Material Properties for SA-533, Grade B, Class 1, 2 Low Alloy Steel(2)(3)...............15 Table 4: Material Properties for SA-508, Class 3, 3a Low Alloy Steel(2)(3)............................16 Table 5: Material Properties for Inconel 690 (SB-168)(2)(3)...................................................17 Table 6: Material Properties for SA-508, Class 1a / SA-106, Grade B Carbon Steel(2)(3).....18 Table 7: Material Properties for SA-336, Class F12(2)(3)......................................................19 Table 8: Material Properties for SA-335, P11(2)(3)................................................................20 Table 9: Material Properties for Alloy 600(2)(3).....................................................................21 Table 10: Material Properties for Type 309 / 308L Stainless Steel(2)(3)................................22 Table 11: Modulus of Elasticity for Thick Perforated Plates (SA-508, Class 3)....................23 Table 12: Thermal Properties for Air [8]..............................................................................24 Table 13: Thermal Properties for Water(1)...........................................................................25 Table 14: Plant Heatup / Cooldown Transient(1)(3)...............................................................26 Table 15: Plant Loading at 5% / min Transient(1)(3)..............................................................27 Table 16: Plant Unloading at 5% / Min Transient(1)(3)..........................................................28 Table 17: Reactor Trip, Loss of Flow, Loss of Load Transients (Envelope)(1)(3)...................29 Table 18: Steam Generator Mass Flow Rates....................................................................30 Table 19: Economizer Feedwater Heat Transfer Coefficients.............................................31 Table 20: Downcomer Feedwater Heat Transfer Coefficients..............................................32 Table 21: Path Locations(1)(2)..............................................................................................33 Table 22: Path Location Data.............................................................................................35

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List of Figures Figure 1. General Modeled Dimensions.............................................................................36 Figure 2. 3-D Finite Element Model....................................................................................37 Figure 3. 3-D Primary Side Finite Element Model and Mesh...............................................38 Figure 4. Example of Applied Thermal Boundary Conditions for Thermal Transient Analyses39 Figure 5. Example of Applied Mechanical Boundary Conditions and Pressure for Thermal Stress Analyses (includes end cap pressures on nozzles).................................40 Figure 6. Example of Temperature Contour, Heatup/Cooldown Transient (Time = 18,735 seconds)............................................................................................................41 Figure 7. Example Stress Contours, Heatup/Cooldown Transient (Time = 18,735 seconds)42 Figure 8 Path Locations, Lower Steam Generator.............................................................43 Figure 9 Path Locations, Middle and Upper Steam Generator...........................................44 Figure 10. Path Location 1, Hot Leg Inlet Nozzle Top Weld................................................45 Figure 11. Path Location 3, Cold Leg Outlet Nozzle Top Weld...........................................46 Figure 12. Path Locations 5 and 6, Stay Cylinder Bottom Hot Leg and Cold Leg................47 Figure 13. Path Locations 7,8, Stay Cylinder Top; Locations 9,10 Primary Shell Top; Location 11 Tube Sheet Top to Stub Barrel......................................................................48 Figure 14. Path Locations 12 Stub Barrel to Lower Shell, 13 Lower Shell to Intermediate Shell

..........................................................................................................................49 Figure 15. Path Locations 14 Inter. Shell to Bottom of Transition Cone and 15 Transition Cone to Upper Shell...................................................................................................50 Figure 16. Path Location 16 Upper Shell to Top Head Torus..............................................51 Figure 17. Path Location 17, Top Head Torus to Top Head Dome (Radial Direction).........52 Figure 18. Path Location 18, FW Nozzle Top Weld to SG Shell Stub Barrel (Unit 2); 19 - FW Nozzle Weld to Branch Boss (Unit 1, 3); 20 - FW Nozzle Inside Radius - Top....53 Figure 19. Path Location 21, Top Downcomer Blowdown Nozzle Top Weld to SG Shell....54 Figure 20. Path Location 23 - Downcomer FW Nozzle Top Weld to SG Shell.....................55 Figure 21. Path Location 27, 28, 29 - Mainsteam Nozzle, Top Weld to SG Shell, Inside Radius,

Inside to Outside - Top.......................................................................................56

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1.0 OBJECTIVE Arizona Public Service (APS) plans to request relief from the Nuclear Regulatory Commission (NRC) to increase the inspection interval of several steam generator (SG) welds at Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, 3. The SGs at PVNGS are CE Model 80 design which is not addressed in the Reference [2a, 2b] EPRI technical basis reports. The CE Model 80 SG configuration at PVNGS includes a stay cylinder welded to the bottom head with a divider plate that is mechanically attached to the stay cylinder and the bottom head as shown in Figure 1. This bottom head design is different from that considered in Reference [2b], which has the traditional divider plate configuration. In addition, the SGs at PVNGS have two main steam nozzles oriented at an angle on the top head rather than a single main steam nozzle at top dead center of the top head considered in Reference [2a].

The objective of this calculation is to develop a representative finite element model (FEM) of the PVNGS SG. The model will then be used to determine the stresses due to thermal transients with appropriate pressure loading. Through-wall stresses will be extracted at locations of interest and stored in computer files that will be used in a separate fracture mechanics evaluation.

2.0 TECHNICAL APPROACH 2.1 Finite Element Model An FEM is developed using the ANSYS finite element analysis software package [3]. The FEM is a 3-dimensional (3-D) half model of the SG that includes the following components:

x primary top and bottom heads (and cladding) x secondary shell (lower, intermediate, transition, upper, torus) x tubesheet x

support skirt x

primary inlet, primary outlet, economizer feedwater, downcomer blowdown, downcomer feedwater, recirculation, and main steam nozzles Figure 2 and Figure 4 illustrate these components. (Note: Model assumptions are listed in Section 4.0.)

2.2 Pressure / Thermal Stress Analyses Stress analyses are performed for thermal transients with internal pressure. For thermal loads due to thermal transients, thermal analyses are performed to determine the temperature distribution time-histories for each transient. These temperature distributions are then used as input to perform stress analyses for each transient. For internal pressure, appropriate internal pressures for each transient are interpolated for each time step and applied to the stress analyses for each transient. Stress results are saved for use in future evaluations.

3.0 DESIGN INPUTS The PVNGS CE Model 80 SG components listed in Section 2.1 are included in the model. Thermal sleeves are included for the downcomer feedwater and recirculation nozzles.

Geometry data is shown in Table 1 and Figure 1 and are obtained from the Reference [5] inputs, particularly the Reference [5c] through [5s] drawings. Dimensions not shown on the drawings are scaled from the drawings as necessary.

For this evaluation, four basic transients are analyzed per design inputs [1, 5t]:

x Plant Heatup/Cooldown

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x Plant Loading at 5%/min x

Plant Unloading at 5%/min x

Reactor Trip, Loss of Flow, Loss of Load (Enveloped)

These transients are consistent with those analyzed in Reference [2a, 2b]. For each of these transients, the temperatures with corresponding heat transfer coefficients are applied versus time to the thermal transient analysis. The thermal transient analysis results and corresponding pressures are applied in the subsequent stress analysis evaluation. Further details are discussed in the following sections.

44.0 ASSUMPTIONS A number of assumptions are made during development of the FEM and the thermal / pressure stress evaluations, which are listed as follows:

x The head-to-tubesheet weld, shell-to-tubesheet weld, shell circumferential welds, and head circumferential welds and nozzle to secondary shell welds are not specifically modeled. The material properties between the base metal and the weld material are similar enough that the effect of this assumption will be minimal.

x The SG vessel penetrations for small nozzles, manways and snubber lugs are not modeled. Nor are any internal components (e.g., square bend tubes, tube support plates, feed ring) modeled, other than the tubesheet and the primary divider plate.

x The divider plates are not welded to the lower head, instead they are held in place by a series of seat bars, which are welded to the lower head and attachment plates (per the Reference [5]

design inputs). The seat bars and attachment plates are not specifically modeled. Instead, the divider plate is directly attached to the stay cylinder, the lower head and the tubesheet. The divider plates will only be included in the thermal analyses but will be removed for the stress analyses as they are neither pressure boundaries nor structural components.

x Heat transfer coefficients during thermal transients are representatively assumed to be 10,000 BTU/hr-ft²-°F for the inside surfaces of the primary side, and 5,000 BTU/hr-ft²-°F for both the inside surfaces of the water and steam portions of the secondary side.

x All thermal transients are assumed to start and end at a steady-state uniform temperature.

x The stress-free reference temperature for thermal stress calculation is assumed to be an ambient temperature of 70°F, which is used for thermal strain calculations. This assumption is typical for stress analyses in similar components.

x All outside surfaces are assumed to be fully insulated and the insulation itself is treated as perfect, with zero heat transfer capability. This assumption is typical for stress analyses in similar components.

x The base of the model (i.e., the bottom of the support skirt and the bottom of the air elements) are assumed to be in contact with the floor support steel which is at a constant 120°F, per the Design Specification [5t].

x The perforations in the tubesheet are not specifically modeled. Instead, equivalent material properties (i.e. modulus elasticity and Poissons ratio) are calculated and applied to the perforated region of the tubesheet (see Section 5.1.1 for additional details). Equivalent material properties similar to those used in References [2a, 2b] are used in this evaluation.

x The metal densities and Poissons ratios are assumed to be temperature independent.

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x Given the hollow region in the stay cylinder air elements will be modeled inside the stay cylinder and the support (see Section 5.1.1 for additional details). The air elements will only be included in the thermal analyses but will be removed for the stress analyses. It is assumed that this region is essentially stagnant with no forced air movement.

x The transient definitions for Unit 2 are assumed to be the same as those for Units 1 and 3 [5t].

x The Unit 1 and 3 economizer feedwater nozzle welds onto an integral branch, while the Unit 2 nozzle welds directly into the SG stub barrel. Refer to Reference [5b], file page 113 for Units 1 and 3, Detail 3 and Reference [5a], file page 105, Detail 3 for Unit 2. For this analysis, one model is created based on Unit 1 and 3, however, the results for weld locations of all three units will be evaluated.

x The Unit 2 primary side has two welds on the stay cylinder and no dollar weld on the lower shell, while the Units 1 and 3 stay cylinder have one weld and a dollar weld on the lower shell adjacent to the SG support attachment. One model is used to represent all three units. The welds are not specifically modeled and base material properties are used. The most critical location in the stay cylinder was used to represent all three units. The effect of this assumption on the results is minimal.

x The Unit 2 blowdown nozzle was welded with carbon steel materials, while the Units 1 and 3 blowdown nozzles were welded with Alloy 82 materials. The welds are not specifically modleed and base material properties were used. The effect of this assumption on the results is minimal.

x Weld CW303, connecting the Top Head Torus (Item 29) to the Top Head Dome (Item 34) (refer to Reference [5b], file page 95), is detailed in Reference [16], file page 306. For evaluation purposes, the weld results will be provided in a radial direction.

x The Tubesheet Downcomer Nozzles (associated with welds41-100, 41-101,42-100 and 42-101) are not modeled since APS will not be seeking relief for these components using this technical basis.

55.0 CALCULATIONS 5.1 Finite Element Model An FEM of the PVNGS SG is developed using the ANSYS finite element analysis software package [1].

Details of the modeled components are discussed in Section 2.1, and the modeled dimensions are shown in Table 1 and Figure 1.

The 3-D half model is constructed using SOLID185 8-Node, and SOLID186 20-Node Structural elements. The thermal equivalent elements for the thermal transient analyses are SOLID70 and SOLID90 respectively. The constructed model is shown in Figure 3.

5.1.1 Material Properties The SG model was created using the materials summarized in Table 2.

The material properties were obtained from the relevant tables in the 1989 Edition of ASME Code,Section III, Appendices [6]. Temperature dependent material properties used in the finite element analysis are listed in Table 3 through Table 11.

Determination of Perforated Tubesheet Equivalent Material Properties Equivalent modulus of elasticity (E) and Poissons ratio values are obtained from Reference [7] and DSSOLHGWRWKHSRUWLRQRIWKHSHUIRUDWHGWXEHVKHHW7KHOLJDPHQWHIILFLHQF\\ KS LV

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calculated using the minimum ligament width (h = 1.0 - 0.758 = 0.242) and the pitch of penetration pattern (p = 1.0). The effective elastic constants (E*/E = 0.207, * = 0.406, and G*/G = 0.169) are interpolated from the data provided in Table A.2 of Reference [7] using a Poissons Ratio of 0.3. The effective Youngs modulus (E*) and effective shear modulus (G*) are calculated using the Youngs modulus of the tubesheet material (see Table 4 and Table 11).

The values of effective Youngs modulus in perforated plate thickness direction (Ez*) and effective transverse shear modulus (Gz*) are calculated based on the effective Youngs modulus in perforated plate thickness direction ratio (Ez*/E = 0.460) and effective transverse shear modulus ratio (Gz*/G =

0.314) interpolated using the data in Table 4.1 of Reference [7]. The shear modulus (G), effective shear modulus (G*), and the effective transverse shear modulus (Gz*) are calculated at 600°F. For simplicity 600°F is selected for the shear modulus as the normal operating temperature is 610°F. Using the shear modulus at 600°F will have an insignificant effect on the stress results.

Since the tubesheet thickness direction is in the global Y direction of the model, the effective Youngs modulus in thickness direction (Ez*) is applied to EY in ANSYS and the effective Youngs modulus (E*)

is applied to EX and EZ in ANSYS. Similarly, the effective Poissons ratio (*) is applied to NUXY and 18<=LQ$16<6DQG3RLVVRQ¶VUDWLRLVDSSOLHGWR18;=LQ$16<67KHHIIHFWLYHVKHDUPRGXOL* 

is applied to GXZ in ANSYS and the effective transverse shear modulus (Gz*) is applied to GXY and GYZ in ANSYS.

The material properties for the perforated tubesheet are listed in Table 4 and Table 11.

Determination of Air Thermal Material Properties Air elements are modeled inside the stay cylinder and support. Temperature dependent density, thermal conductivity and specific heat for air at room pressure (14.5 psia) are developed using Reference [8]. The resulting values are shown in Table 12.

55.2 Pressure / Thermal Stress Analyses 5.2.1 Thermal Heat Transfer Analyses The thermal transients listed in Table 14 through Table 17 are applied to the interior surface nodes of the tubesheet, primary and secondary shells and nozzles. Per Section 4.0, a heat transfer coefficient of 10,000 BTU/hr-ft²-°F is applied to the inside surfaces of the primary side and 5,000 BTU/hr-ft²-°F is applied to the inside surfaces of the secondary side.

Per Section 4.0, no heat transfer coefficients or temperatures are applied to the insulated outside surfaces, and the base of the support skirt and air elements are held at a constant 120°F. Figure 4 shows representative plots of the thermal loads applied for Plant Loading transient.

Heat transfer coefficients are calculated based on the following equation [9].

= 0.023..

where:

R = V x ID / ( x x g)

V = FLOW / ([ó,'2) h = inside film coefficient (btu / hr - ft2 - °F)

R = Reynolds number

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C = fluid conductivity ( btu / hr - ft - °F)

P = Prandtl number ID = Inside diameter (ft)

V = fluid velocity ( ft / sec )

= dynamic viscosity ( lbf sec / ft2 )

= specific volume ( ft3 / lb )

g = 32.2 ft / sec2 FLOW = fluid flow rate ( ft3 / sec )

An additional time is added to the end of each transient to ensure that any lagging peak stresses are captured, followed by a steady state load step.

5.2.2 Thermal Stress Analyses Symmetric boundary conditions are applied to the symmetry plane. The nodes at the base of the support skirt are vertically restrained. Appropriate internal pressure for each transient is also applied to the interior surfaces of the model. The bottom face of the support skirt and air elements are held at a constant 120°F. The reference temperature for the thermal strain calculation is assumed to be 70°F.

Figure 5 shows an example plot of the pressure load and boundary conditions applied for the Plant Loading transient thermal stress analyses.

55.3 Differences Between Units 1, 3 and Unit 2 It was determined that the most significant significant difference between Units 1, 3 and Unit 2 are the economizer feedwater nozzle design and thickness of the attaching stub barrel. As discussed in the Section 4.0 assumptions, both locations/designs were evaluated using one analysis. Other differences between Units 1, 3 and Unit 2 are also discussed in Section 4.0.

6.0 RESULTS OF ANALYSIS An FEM of the PVNGS SG with components previously described is developed. The stress results due to thermal transients and internal pressure have been run and are stored to be used for future fracture mechanics evaluations.

Representative temperature contour and stress contour plots for the Heatup/Cooldown are shown in Figure 6 and Figure 7, respectively. The time shown in Figure 6 is when the maximum total stress intensity occurs. Figure 8 and Figure 9 show the locations of the stress paths in the SG. These paths are selected to align with the welds/components examined as part of PVNGS ISI program as shown in Table 21. Path location data is provided in Table 22. Figure 10 through Figure 21 show detailed path locations where stresses are extracted.

The input and output files used in this evaluation are listed in Appendix A. All stresses are extracted in either a cylindrical coordinate system with y along the hoop direction of the SG and z along the axial direction of the SG or spherical coordinate system where y and z are in the hoop directions.

7.0 REFERENCES

File No.: 2300243.301P Revision: 2 Page 11 of 55 F0306-01R4 This document contains Structural Integrity; client; or supplier proprietary information. This document may not be disclosed, wholly or in part, to any third parties without the prior written consent of Structural Integrity Associates, Inc.

1. E-mail from David Van Allen (APS) to Scott Chesworth (SI) on Tue 9/17/2024 7:37 AM, "

Subject:

FW: Palo Verde SG transients-(Design Engineering Support Requested)," with Attachment "Palo Verde SG Transients.xlsx", SI File No. 2300243.208.

2. EPRI Technical Basis Reports.

a. Technical Bases for Inspection Requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Inside Radius Sections. EPRI, Palo Alto, CA:

2019. 3002014590.

b. Technical Bases for Inspection Requirements for PWR Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head, and Tubesheet-to-Shell Welds. EPRI, Palo Alto, CA: 2019. 3002015906.

3. ANSYS Mechanical APDL (UP20170403) and Workbench (March 31, 2017), Release 18.1, SAS IP, Inc.

4. ASME Boiler and Pressure Vessel Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, 2017 Edition.

5. Design Input from Arizona Public Service.

Technical Manuals:

a. 02-MN725-A00240-2 (PVIMG000000001, REV. 2), RSG Technical Manual, (Unit 2), SI File No. 2300243.202, (Note: this document contains drawings).

b. MN725-A01211, RSG Technical Manual, Revision 3, (Units 1 and 3), SI File No.

2300243.202, (Note: this document contains drawings).

Drawings:

c.

MN725-A00357 (PV-DWF-100-010, REV. 1), Primary Head Machined, PROPRIETARY SI File No. 2300243.204P.

d. MN725-A00277 (PV-DWF-11-005, REV. 1), Tube Sheet Details U02, PROPRIETARY SI File No. 2300243.204P.

e. MN725-A00419 (PX-DWD-10-061, REV. 3), Primary Nozzles U31, PROPRIETARY SI File No. 2300243.204P.

f.

MN725-A00607 (PX-DWF-10-010, REV. 3), Unit 1 Primary Head Machining, PROPRIETARY SI File No. 2300243.204P.

g. MN725-A00707, Tube Sheet Detail Unit 01 (PX-DFW-11-010), PROPRIETARY SI File No. 2300243.204P.

h. MN725-A01075 (PX-DWF-13-013, REV. 1), Recirculation Noz Unit 01, PROPRIETARY SI File No. 2300243.204P.

i.

MN725-A01231 (PZ-DWF-10-010, REV. 0), Unit 3 Primary Head Details, PROPRIETARY SI File No. 2300243.204P.

j.

MN725-A01372 (PZ DWF 13-014, REV. 0), Primary Head Machined Unit 03, PROPRIETARY SI File No. 2300243.204P.

k.

MN725-A01093 (PX-DWF-12-014), Downcomer FW Nozzle Details U01, PROPRIETARY SI File No. 2300243.204P.

File No.: 2300243.301P Revision: 2 Page 12 of 55 F0306-01R4 This document contains Structural Integrity; client; or supplier proprietary information. This document may not be disclosed, wholly or in part, to any third parties without the prior written consent of Structural Integrity Associates, Inc.

l.

MN725-A00615 (PX-DWF-11-003), Unit 31 Feedwater Nozzle, PROPRIETARY SI File No. 2300243.204P.

m. MN725-A000475 (PV-DWF-13-011), Main Steam Nozzle, PROPRIETARY SI File No.

2300243.204P.

n. MN725-A00430 (PX-DWD-12-057), Downcomer Feedwater Nozzle U31, PROPRIETARY SI File No. 2300243.204P.

o. MN725-A000423 (PX-DWD-11-055), Feedwater Nozzle, PROPRIETARY SI File No.

2300243.204P.

p. MN725-A00420 (PX-DWD-12-057), Downcomer Feedwater Nozzle Unit 31, PROPRIETARY SI File No. 2300243.204P.

q. MN725-A00417 (PX-DWD-12-068), Downcomer Blowdown Nozzle, PROPRIETARY SI File No. 2300243.204P.

r.

MN725-A000256 (PV-DWF-11-003), Unit 2 FW Nozzle, PROPRIETARY SI File No.

2300243.204P.

s.

MN725-A000254 (PV-DWF-12-014), Downcomer Feedwater Nozzle Assembly, PROPRIETARY SI File No. 2300243.204P.

Design Specifications:

t.

31 MN725-A01166, Design Specification For Replacement Steam Generators For The Aps Palo Verde NGS Unit 1 and 3, SI File No. No.1100527.205.

6. ASME Boiler and Pressure Vessel Code,Section III, Division 1 - Appendices 1989 Edition.

7. Thomas Slot, "Stress Analysis of Thick Perforated Plates," Technomics, 1972.

8. Temperature Dependent Air Properties per Website https://www.engineeringtoolbox.com.

9. Textbook, Principles of Heat Transfer, 3rd Edition, Frank Kreith.

10. SI Calculation No. 1300729.306P, Revision 0, Greens Function Analysis of the Steam Generator Auxiliary Feedwater Nozzle.

11. Water - Prandtl Number vs. Temperature and Pressure (engineeringtoolbox.com)

12. Water - Specific Volume vs. Temperature (engineeringtoolbox.com)

13. Crane Technical Paper No. 410, Flow of Fluids Through Valves, Fittings and Pipe, 2011.

14. Water - Thermal Conductivity vs. Temperature (engineeringtoolbox.com)

15. ASME Boiler and Pressure Vessel Code,Section II, Materials, Part D - Properties, 2019 Edition.

16. RSG #1 Ansaldo PSE, SI File No. 2300243.204.

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Table 1. Dimensions Used in Model(1)

Description Dimensions

((in)

Inside Diameter of Secondary Intermediate Shell 193.0 Inside Diameter of Secondary Lower Shell 193.0 Outside Diameter of Secondary Intermediate Shell 202.68 Outside Diameter of Stub Barrel 204.01(2) 202.68(3)

Inside Radius of Lower Primary Head (to Base Metal) 91.75 Inside Radius of Lower Primary Head 91.75 Outside Diameter of Lower Primary Head 101.05 Thickness of Lower Primary Head 9.3 Cladding Thickness on Primary Side 0.16 Tubesheet Thickness 25.0 Notes:

1. Dimensions are obtained from the Reference [5] inputs, particularly the Reference [5c] through

[5s] drawings. Dimensions not shown on the drawings are scaled from the drawings as necessary.

2. Applicable to Units 1 and 3.

3. Applicable to Unit 2.

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Table 2. Materials of Components Used in Model(1)(2)

Component Material [5t]

Tubesheet, Stub Barrel SA-508 Class 3a Support, Stay Cylinder SA-508 Class 3 Primary Head with/without Integral Nozzles/Manways SA-508 Class 3 Primary Inlet Nozzle Safe-End SA-508 Class 1a Divider Plate SB-168, Inconel 690 Cladding: Primary Nozzle Safe End 309/308L stainless steel Cladding: Tube Sheet Primary Side Alloy 600 strip Cladding: Primary Head Interior Surface Alloy 600 or 309/308L stainless steel Lower Shell, Intermediate Shell SA-533 Gr B Cl 2 Shell Cone SA-508 Class 3a Upper Shell, Top Head Torus and Steam Dome with or without Integral Nozzle SA-533 Gr B Cl 1 42" Primary Side Inlet SA-508 Class 3 30" Primary Side Outlet SA-508 Class 3 32" Steam Outlet Nozzle w/Integ. Flow Limiter SA-508 Class 1a 14" (Economizer) Feedwater Inlet SA-508 Class 3a 14" (Economizer) Feedwater Inlet Safe-End SA-508 Class 1a 6" Downcomer Feedwater Inlet SA-508 Class 3a 6" Downcomer Feedwater Inlet - Thermal Liner SA-335 P11 6 Downcomer Feedwater Transition Piece SA-508 Class 1a 4" Recirculation SA-508 Class 3 4" Recirculation - Thermal Liner SA-106 Gr B 6" Downcomer Blowdown SA-336 Class F12 4 Recirculation Nozzle Safe End(3)

SA-508 Class 1a Notes:

1. The model also contains a Material 3 which was not used.

2. Model assumptions are listed in Section 4.0.

3. The 4" Recirculation Nozzles are not subject to exams and not scoped into the program. Ref.

ASME Section XI, Table C-B, note 5 and IWC-1222(a)(1).

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Table 3: Material Properties for SA-533, Grade B, Class 1, 2 Low Alloy Steel(2)(3)

(Lower Shell, Intermediate Shell, Upper Shell, Top Head Dome, Top Head Torus)

Temperature

(°F)

Modulus of Elasticity (E)

(106 psi)

Coefficient of Thermal

([SDQVLRQ

(10-6 in/in/°F)

Thermal Conductivity (K)

(10-4 BTU/in-s-°F)

Specific Heat (C)(4)

(BTU/lb-°F) 70 29.2 7.02 5.16 0.107 100 29.0(1) 7.06 5.23 0.109 150 28.8(1) 7.16 5.35 0.113 200 28.5 7.25 5.42 0.115 250 28.3(1) 7.34 5.49 0.118 300 28.0 7.43 5.51 0.121 350 27.7(1) 7.50 5.51 0.123 400 27.4 7.58 5.51 0.126 450 27.2(1) 7.63 5.49 0.130 500 27.0 7.70 5.44 0.133 550 26.7(1) 7.77 5.37 0.135 600 26.4 7.83 5.32 0.139 650 25.9(1) 7.90 5.25 0.142 700 25.3 7.94 5.16 0.144 Notes:

1. Value linearly interpolated from [6].

2. 'HQVLW\\ OELQ3 [15, Table PRD], assumed temperature independent.

3. 3RLVVRQ¶V5DWLR DVVXPHGWHPSHUDWXUHLQGHSHQGHQW

4. Calculated per Note 1 of Table I-4.0 [6].

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Table 4: Material Properties for SA-508, Class 3, 3a Low Alloy Steel(2)(3)

(Support, Primary Head, Tubesheet, Stub Barrel, Stay Cylinder, Primary Inlet Nozzle, Primary Outlet Nozzle, Economizer Feedwater Nozzle, Recirculation Nozzle, Shell Cone, Downcomer Feedwater Nozzle)

Temperature

(°F)

Modulus of Elasticity (E)

(106 psi)

Coefficient of Thermal

([SDQVLRQ

(10-6 in/in/°F)

Thermal Conductivity (K)

(10-4 BTU/in-s-°F)

Specific Heat (C)(4)

(BTU/lb-°F) 70 27.8 6.41 5.05 0.107 100 27.6(1) 6.50 5.09 0.110 150 27.4(1) 6.57 5.16 0.113 200 27.1 6.67 5.19 0.116 250 26.9(1) 6.77 5.19 0.119 300 26.7 6.87 5.19 0.121 350 26.5(1) 6.98 5.19 0.124 400 26.2 7.07 5.16 0.127 450 26.0(1) 7.15 5.12 0.129 500 25.7 7.25 5.09 0.132 550 25.4(1) 7.34 5.05 0.134 600 25.1 7.42 4.98 0.137 650 24.9(1) 7.52 4.93 0.140 700 24.6 7.59 4.86 0.142 Notes:

1. Value linearly interpolated from [6].

2. 'HQVLW\\ OELQ3 [15, Table PRD], assumed temperature independent.

3. 3RLVVRQ¶V5DWLR DVVXPHGWHPSHUDWXUHLQGHSHQGHQW

4. Calculated per Note 1 of Table I-4.0 [6].

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Table 5: Material Properties for Inconel 690 (SB-168)(2)(3)

(Divider Plate)

Temperature

(°F)

Modulus of Elasticity (E)

(106 psi)

Coefficient of Thermal

([SDQVLRQ

(10-6 in/in/°F)

Thermal Conductivity (K)

(10-4 BTU/in-s-°F)

Specific Heat (C)(4)

(BTU/lb-°F) 70 30.3 7.73 1.57 0.112 100 30.1(1) 7.76 1.62 0.113 150 29.8(1) 7.80 1.69 0.115 200 29.5 7.85 1.76 0.117 250 29.3(1) 7.89 1.83 0.119 300 29.1 7.93 1.90 0.121 350 29.0(1) 7.98 1.97 0.122 400 28.8 8.02 2.04 0.124 450 28.6(1) 8.06 2.11 0.125 500 28.3 8.09 2.18 0.127 550 28.2(1) 8.13 2.25 0.128 600 28.1 8.16 2.31 0.128 650 27.9(1) 8.20 2.38 0.130 700 27.6 8.25 2.45 0.131 Notes:

1. Values linearly interpolated from [6].

2. 'HQVLW\\ 80 lb/in3 [15, Table PRD], assumed temperature independent.

3. 3RLVVRQ¶V5DWLR DVVXPHGWHPSHUDWXUHLQGHSHQGHQW

4. Calculated per Note 1 of Table I-4.0 [6].

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Table 6: Material Properties for SA-508, Class 1a / SA-106, Grade B Carbon Steel(2)(3)

(Recirculation Nozzle Safe-End, Primary Inlet Nozzle Safe-End, Feedwater Nozzle Safe-End, Steam Outlet Nozzle, Downcomer Feedwater Nozzle Transition Piece, Recirculation Nozzle Thermal Liner)

Temperature

(°F)

Modulus of Elasticity (E)

(106 psi)

Coefficient of Thermal

([SDQVLRQ

(10-6 in/in/°F)

Thermal Conductivity (K)

(10-4 BTU/in-s-°F)

Specific Heat (C)(4)

(BTU/lb-°F) 70 29.5 5.60 6.94 0.107 100 29.3(1) 5.73 6.92 0.109 150 29.1(1) 5.91 6.85 0.112 200 28.8 6.09 6.76 0.116 250 28.6(1) 6.27 6.69 0.119 300 28.3 6.43 6.57 0.122 350 28.0(1) 6.59 6.48 0.125 400 27.7 6.74 6.39 0.128 450 27.5(1) 6.89 6.27 0.130 500 27.3 7.06 6.16 0.133 550 27.0(1) 7.18 6.04 0.136 600 26.7 7.28 5.93 0.137 650 26.1(1) 7.40 5.81 0.140 700 25.5 7.51 5.69 0.143 Notes:

1. Values linearly interpolated from [6].

2. 'HQVLW\\ 80 lb/in3 [15, Table PRD], assumed temperature independent.

3. 3RLVVRQ¶V5DWLR DVVXPHGWHPSHUDWXUHLQGHSHQGHQW

4. Calculated per Note 1 of Table I-4.0 [6].

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Table 7: Material Properties for SA-336, Class F12(2)(3)

(Downcomer Blowdown Nozzle)

Temperature

(°F)

Modulus of Elasticity (E)

(106 psi)

Coefficient of Thermal

([SDQVLRQ

(10-6 in/in/°F)

Thermal Conductivity (K)

(10-4 BTU/in-s-°F)

Specific Heat (C)(4)

(BTU/lb-°F) 70 29.7 5.60 5.60 0.106 100 29.5(1) 5.73 5.63 0.108 150 29.3(1) 5.91 5.65 0.112 200 29.0 6.09 5.65 0.115 250 28.8(1) 6.27 5.63 0.118 300 28.5 6.43 5.60 0.121 350 28.2(1) 6.59 5.56 0.123 400 27.9 6.74 5.53 0.127 450 27.7(1) 6.89 5.46 0.129 500 27.5 7.06 5.42 0.132 550 27.2(1) 7.18 5.35 0.134 600 26.9 7.28 5.25 0.136 650 26.6(1) 7.40 5.16 0.138 700 26.3 7.51 5.09 0.142 Notes:

1. Values linearly interpolated from [6].

2. 'HQVLW\\ 80 lb/in3 [15, Table PRD], assumed temperature independent.

3. 3RLVVRQ¶V5DWLR DVVXPHGWHPSHUDWXUHLQGHSHQGHQW

4. Calculated per Note 1 of Table I-4.0 [6].

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Table 8: Material Properties for SA-335, P11(2)(3)

(Downcomer Feedwater Nozzle Thermal Liner)

Temperature

(°F)

Modulus of Elasticity (E)

(106 psi)

Coefficient of Thermal

([SDQVLRQ

(10-6 in/in/°F)

Thermal Conductivity (K)

(10-4 BTU/in-s-°F)

Specific Heat (C)(4)

(BTU/lb-°F) 70 29.7 5.42 4.93 0.106 100 29.5(1) 5.53 4.98 0.109 150 29.3(1) 5.71 5.05 0.113 200 29.0 5.89 5.07 0.116 250 28.8(1) 6.09 5.09 0.119 300 28.5 6.26 5.09 0.122 350 28.2(1) 6.43 5.09 0.125 400 27.9 6.61 5.07 0.127 450 27.7(1) 6.77 5.05 0.130 500 27.5 6.91 5.02 0.133 550 27.2(1) 7.06 4.98 0.136 600 26.9 7.17 4.93 0.138 650 26.6(1) 7.30 4.86 0.140 700 26.3 7.41 4.81 0.144 Notes:

1. Values linearly interpolated from [6].

2. 'HQVLW\\ 80 lb/in3 [15, Table PRD], assumed temperature independent.

3. 3RLVVRQ¶V5DWLR DVVXPHGWHPSHUDWXUHLQGHSHQGHQW

4. Calculated per Note 1 of Table I-4.0 [6].

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Table 9: Material Properties for Alloy 600(2)(3)

(Cladding: Tube Sheet Primary Side)

Temperature

(°F)

Modulus of Elasticity (E)

(106 psi)

Coefficient of Thermal

([SDQVLRQ

(10-6 in/in/°F)

Thermal Conductivity (K)

(10-4 BTU/in-s-°F)

Specific Heat (C)(4)

(BTU/lb-°F) 70 31.0 6.76 1.99 0.115 100 30.8(1) 6.90 2.01 0.117 150 30.5(1) 7.07 2.06 0.119 200 30.2 7.20 2.11 0.121 250 30.1(1) 7.31 2.15 0.122 300 29.9 7.40 2.22 0.124 350 29.7(1) 7.50 2.27 0.124 400 29.5 7.57 2.34 0.127 450 29.3(1) 7.64 2.38 0.127 500 29.0 7.70 2.45 0.128 550 28.9(1) 7.77 2.50 0.130 600 28.7 7.82 2.57 0.132 650 28.5(1) 7.88 2.62 0.132 700 28.2 7.94 2.69 0.134 Notes:

1. Values linearly interpolated from [6].

2. 'HQVLW\\ 80 lb/in3 [15, Table PRD], assumed temperature independent.

3. 3RLVVRQ¶V5DWLR DVVXPHGWHPSHUDWXUHLQGHSHQGHQW

4. Calculated per Note 1 of Table I-4.0 [6].

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Table 10: Material Properties for Type 309 / 308L Stainless Steel(2)(3)

(Cladding: Primary Nozzle Safe End, Channel Head Interior Surface)

Temperature

(°F)

Modulus of Elasticity (E)

(106 psi)

Coefficient of Thermal

([SDQVLRQ

(10-6 in/in/°F)

Thermal Conductivity (K)

(10-4 BTU/in-s-°F)

Specific Heat (C)(4)

(BTU/lb-°F) 70 28.3 8.81 1.48 0.115 100 28.1(1) 8.87 1.53 0.118 150 27.9(1) 8.95 1.60 0.121 200 27.6 9.02 1.64 0.121 250 27.3(1) 9.06 1.71 0.123 300 27.0 9.10 1.78 0.126 350 26.8(1) 9.12 1.85 0.128 400 26.5 9.14 1.90 0.128 450 26.2(1) 9.16 1.97 0.130 500 25.8 9.18 2.04 0.132 550 25.6(1) 9.20 2.11 0.133 600 25.3 9.21 2.15 0.134 650 25.1(1) 9.23 2.22 0.136 700 24.8 9.25 2.29 0.137 Notes:

1. Values linearly interpolated from [6].

2. 'HQVLW\\ 80 lb/in3 [15, Table PRD], assumed temperature independent.

3. 3RLVVRQ¶V5DWLR DVVXPHGWHPSHUDWXUHLQGHSHQGHQW

4. Calculated per Note 1 of Table I-4.0 [6].

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Table 11: Modulus of Elasticity for Thick Perforated Plates (SA-508, Class 3)

(see Table 2 for associated components)

Temperature

(°F)

Effective Modulus of Elasticity (E*)

(106 psi)

Effective Modulus of Elasticity in Thickness Direction (Ez*)

(106 psi) 70 5.75 12.78 100 5.71 12.71 150 5.66 12.59 200 5.60 12.46 250 5.56 12.37 300 5.52 12.28 350 5.47 12.16 400 5.42 12.05 450 5.36 11.93 500 5.31 11.82 550 5.25 11.68 600 5.19 11.54 650 5.14 11.43 700 5.09 11.31

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Table 12: Thermal Properties for Air [8]

(Present on the external ambient side of the stay cylinder)

Temperature

(°F)

'HQVLW\\

(10-5 lb/in³)

Thermal Conductivity (K)

(10-7 BTU/in-s-°F)

Specific Heat (C)

(BTU/lb-°F) 70 4.334 3.472 0.2402 100 4.103 3.637 0.2404 150 3.768 3.905 0.2408 200 3.484 4.167 0.2414 250 3.235 4.424 0.2422 300 3.021 4.671 0.2430 350 2.830 4.914 0.2441 400 2.668 5.153 0.2452 450 2.523 5.387 0.2464 500 2.373 5.616 0.2477 550 2.276 5.843 0.2491 600 2.147 6.065 0.2505 650 2.070 6.282 0.2520 700 1.968 6.498 0.2535

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Table 13: Thermal Properties for Water(1)

(Present between thermal liner and nozzle on secondary side)

Temperature

(°F)

Pr Gr PrGr Thermal Conductivity (K)

(10-7 BTU/in-s-°F)

'HQVLW\\

(10-5 lb/in³)

Specific Heat (C)

(BTU/lb-°F) 70 6.82 4.84E+05 3.30E+06 6.51E-05 0.0361 0.4 100 4.54 1.86E+06 8.44E+06 8.18E-05 0.0359 0.4 150 3.21 8.88E+06 2.85E+07 9.75E-05 0.0354 0.4 200 1.88 1.59E+07 2.99E+07 1.13E-04 0.0348 0.4 250 1.52 3.60E+07 5.45E+07 1.24E-04 0.0340 0.4 300 1.15 5.60E+07 6.44E+07 1.34E-04 0.0331 0.4 350 1.03 9.25E+07 9.48E+07 1.40E-04 0.0322 0.4 400 0.90 1.29E+08 1.16E+08 1.45E-04 0.0311 0.4 450 0.88 1.93E+08 1.69E+08 1.48E-04 0.0298 0.4 500 0.85 2.57E+08 2.18E+08 1.50E-04 0.0038 0.4 550 0.95 3.82E+08 3.61E+08 1.52E-04 0.0266 0.4 600 1.04 5.06E+08 5.26E+08 1.53E-04 0.0246

0.4 Notes

1. Data are from the precalculated values available in Reference [10], Section 3.2.1, Water Gap Thermal Conductivity.

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Table 14: Plant Heatup / Cooldown Transient(1)(3)

Pct Power Time (hrs)

Time (sec)

T Hot

(°F)

T Cold

(°F)

T SG Secondary

(°F)

T Econ FW (°F)

T Down FW (°F)

P Primary (psig)

P Secondary (psig)

HTC Primary(2)

(BTU/hr-ft2-°F)

HTC Secondary(2)

(BTU/hr-ft2-

°F)

HTC Econ FW ID(2)

(BTU/hr-ft2-°F)

HTC Down FW ID(2)

(BTU/hr-ft2-°F) 0 0

0 70 70 70(4) 70(4) 70(4) 60(5) 0 0

0 0

0 0

2 7200 275 275 275 275 275 60(5) 0 10000 5000 5000 5000 0

5.2 18735 575 575 564.5 564.5 564.5 2235 1155 10000 5000 5000 5000 0

13.9 50000 575 575 564.5 564.5 564.5 2235 1155 10000 5000 5000 5000 0

17.1 61520 252 252 247 247 247 0

0 10000 5000 5000 5000 0

18.9 68000 70 70 70 70 70 0

0 10000 5000 5000 5000 0

19.9 71600 70 70 70 70 70 0

0 10000 5000 5000 5000 Notes:

1. Transient definition based on References [1] and [5t] (Reference [1] takes precedence where values differ).

2. Values conservatively assumed.

3. Primary includes Hot and Cold legs. Secondary includes both liquid and steam space, i.e. shell above tubesheet.

4. 0°°F (rather than 70°°F) was used in the analysis, but is not considered to have any significant impact on the results.

5. 100 psig (rather than 60 psig) was used in the analysis, but is not considered to have any significant impact on the results.

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Table 15: Plant Loading at 5% / min Transient(1)(3)

Pct Power Time (hrs)

Time (sec)

T Hot

(°F)

T Cold

(°F)

T SG Secondary

(°F)

T Econ FW (°F)

T Down FW (°F)

P Primary (psig)

P Secondary (psig)

HTC Primary(2)

(BTU/hr-ft2-°F)

HTC Secondary(2)

(BTU/hr-ft2-

°F)

HTC Econ FW ID(2)

(BTU/hr-ft2-°F)

HTC Down FW ID(2)

(BTU/hr-ft2-°F) 0 0

0 564 564.5 549 549 549 2235 1014 10000 5000 5000 5000 0

0 0.001 564 564.5 549 549 40 2235 1014 10000 5000 5000 105 10 2

120 570 563.5 550.3 550.3 40 2275 1026 10000 5000 5000 105 15 3

180 573 563.0 551.0 551.0 40 2275 1032 10000 5000 5000 105

>15

>3 180.001 573 563.0 551.0 40 551.0 2275 1032 10000 5000 25.9 5000

>15

>3.1 366.001 582 561.4 553.0 40 553.0 2275 1052 10000 5000 25.9 5000

>15

>3.1 366.002 582 561.4 553.0 230 553.0 2275 1052 10000 5000 174.0 5000 50 10 600 594 559.5 555.5 385 553 2275 1076 10000 5000 358.2 5000 50

>10 600.001 594 559.5 555.5 385 385 2275 1076 10000 5000 358.2 282 95 19 1140 621 555 561 443 443 2235 1131 10000 5000 414.9 288 100 20 1200 624 554.5 562 450 450 2235 1137 10000 5000 414.9 288

>100 30 1800 624 554.5 562 450 450 2235 1137 10000 5000 414.9 288 Notes:

1. Transient definition based on References [1] and [5t] (Reference [1] takes precedence where values differ).

2. Values conservatively assumed.

3. Primary includes Hot and Cold legs. Secondary includes both liquid and steam space, i.e. shell above tubesheet.

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Table 16: Plant Unloading at 5% / Min Transient(1)(3)

Pct Power Time (hrs)

Time (sec)

T Hot

(°F)

T Cold

(°F)

T SG Secondary

(°F)

T Econ FW

(°F)

T Down FW (°F)

P Primary (psig)

P Secondary (psig)

HTC Primary(2)

(BTU/hr-ft2-°F)

HTC Secondary(2)

(BTU/hr-ft2-

°F)

HTC Econ FW ID(2)

(BTU/hr-ft2-°F)

HTC Down FW ID(2)

(BTU/hr-ft2-°F) 100 0

0 624 564.5 566 450 450 2235 1177 10000 5000 415 288 87.5 2.5 150 616.5 563.25 564.4 440 440 2195 1163 10000 5000 415 288 50 10 600 594 559.5 559.5 385 385 2195 1123 10000 5000 221 282

<50

>10 600.001 594 559.57 559.5 385 559.5 2195 1123 10000 5000 221 5000 30.5 13.9 834 582.3 557.6 557.0 330 557.0 2195 1102 10000 5000 25.9 5000 30.5 13.9 834.001 582.3 557.5 557.0 40 557.0 2195 1102 10000 5000 25.9 5000 15 17 1020 573 556 555.0 40 555.0 2195 1085 10000 5000 5000 5000

<15 17 1020.001 573 556 554.9 554.9 100 2195 1085 10000 5000 5000 72.5

<15 17.5 1050 571.5 555.75 554.6 554.6 100 2199 1082 10000 5000 5000 72.5 0

20 1200 564 554.5 553 553.0 100 2199 1069 10000 5000 5000 72.5 0

22.5 1350 564 554.5 553 553.0 100 2235 1055 10000 5000 5000 72.5 0

30 1800 564 554.5 553 553 100 2235 1055(4) 10000 5000 5000 72.5 Notes:

1. Transient definition based on References [1] and [5t] (Reference [1] takes precedence where values differ).

2. Values conservatively assumed.

3. Primary includes Hot and Cold legs. Secondary includes both liquid and steam space, i.e. shell above tubesheet.

4. 1069 psig (rather than 1055 psig) was used in the analysis, but is not considered to have any significant impact on the results.

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Table 17: Reactor Trip, Loss of Flow, Loss of Load Transients (Envelope)(1)(3)

Time (hrs)

Time (sec)

T Hot

(°F)

T Cold

(°F)

T SG Secondary

(°F)

T Econ FW (°F)

T Down FW (°F)

P Primary (psig)

P Secondary (psig)

HTC Primary(2)

(BTU/hr-ft2-°F)

HTC Secondary(2)

(BTU/hr-ft2-

°F)

HTC Econ FW ID(2)

(BTU/hr-ft2-°F)

HTC Down FW ID(2)

(BTU/hr-ft2-°F) 0.0 0

621.2 564.5 553 450 450 2235 1055 10000 5000 415 288 0.3 20 607.2 568.5 553.7 450 450 2315 1057 10000 5000 415 288 0.8 50 586.2 574.5 554.9 450 450 2435 1059 10000 5000 415 288 1.3 75 569 560 555.8 388 388 2535 1061 10000 5000 406 162 1.7 100 551.2 544.5 557 325 325 1635 1063 10000 5000 319 143 3.0 180 551.2 544.5 560 125 125 1659 1069 10000 5000 203 80.9 6.7 400 551.2 544.5 568 80 80 1725 1086 10000 5000 161 64.1 8.3 500 551.2 544.5 572 80 80 1755 1094 10000 5000 161 64.1 16.7 1000 551.2 554.5 590 80 80 1905 1134 10000 5000 161 64.1 35.0 2100 551.2 554.5 590 80 80 2235 1220 10000 5000 161 64.1 Notes:

1. Transient definition based on References [1] and [5t] (Reference [1] takes precedence where values differ).

2. Values conservatively assumed.

3. Primary includes Hot and Cold legs. Secondary includes both liquid and steam space, i.e. shell above tubesheet.

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Table 18: Steam Generator Mass Flow Rates Normal Operation Location Flow (lbm/hr)

Source of Data Flow out of RSG Steam 9.00E+06 Reference [5t], Table 1 Blowdown 1.00E+05 Reference [5t], Table 2 Total 9.10E+06 Flow into RSG Feedwater 8.19E+06 (90% of total)

Reference [5t], Figures 28,29,32,33 Downcomer 9.10E+05 (10% of total)

Reference [5t], Figures 30,31,34 Total 9.10E+06 Notes:

1. Reference [5t], Figure 29, shows FW flow @ 12% as 1.09E+06 lbm/hr which agrees with above, 9.10E6 x 0.12 = 1.09E6 lbm/hr.

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Table 19: Economizer Feedwater Heat Transfer Coefficients Notes:

1. The HTC for 325°F and 388°F were determined by interpolation of available data.

2. Prandtl number source is Reference [11].

3. Water properties source is Reference [12].

4. Viscosity properties source is Reference [13].

5. Conductivity of water properties, K, source is Reference [14].

6. The HTCs at the same temperatures vary due to differences in flow rate.

Temperature

(°F) 40 80 125 230 325 3856) 385(6) 388 450 HTC (BTU/hr-ft2-

°F) 26 161 203 174 319(1) 221 358 406(1) 415 Pr 11.31 5.82 3.48 1.63 0.94 0.94 0.85 ID (in) 12.5 12.5 12.5 12.5 12.5 12.5 12.5 Flow (lbm/hr) 1.09E6 8.19E6 8.19E6 4.19E6 3.82E6 7.01E6 8.19E6 Flow (lbm/sec) 4.85 36.57 36.91 19.59 19.53 35.81 44.41 K (btu/hr-ft-°F) 0.32 0.34 0.35 0.38 0.39 0.39 0.36 Re 4.23E6 5.35E7 8.92E7 9.73E7 1.67E8 3.06E8 4.26E8 Velocity (ft/sec) 5.691 42.907 43.313 22.988 22.922 42.024 52.109 S.V. (ft3/lb) 0.016019 0.016073 0.016225 0.016848 0.0184 0.0184 0.01952 g (ft/sec2) 32.2 32.2 32.2 32.2 32.2 32.2 32.2 Viscosity (lbf-sec/ft2) 3.26E-5 1.94E-5 1.16E-5 5.44E-6 2.9E-6 2.90E-6 2.43E-6 Pressure (psig) 1155 1155 1155 1155 1155 1155 1155

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Table 20: Downcomer Feedwater Heat Transfer Coefficients Temperature

(°F) 40 80 100 125 325 385(8) 385(8) 450 HTC (BTU/hr-ft2-F) 104.6 64.1 72.5(1) 80.9 143.3(1) 162.1 282.2 288.4(6)

Pr 11.31 5.82 3.48 0.94 0.94 0.85 ID (in) 5.761 5.761 5.761 5.761 5.761 5.761 Flow (lbm/hr) 1.09E6(7) 4.55E5 4.55E5 4.55E5 9.1E5 9.1E5 Flow (lbm/sec) 0.27 2.03 2.05 2.33 4.65 4.93 K (btu/hr-ft-°F) 0.32 0.34 0.35 0.39 0.39 0.36 Re 5.05E5 6.45E6 1.08E7 4.3E7 8.61E7 1.03E8 Velocity (ft/sec) 1.475 11.222 11.328 12.847 25.694 27.258 S.V. (ft3/lb) 0.016019 0.016073 0.016225 0.0184 0.0184 0.01952 g (ft/sec2) 32.2 32.2 32.2 32.2 32.2 32.2 Viscosity (lbf-sec/ft2) 3.26E-5 1.94E-5 1.16E-5 2.9E-6 2.9E-6 2.43E-6 Pressure (psig) 1155 1155 1155 1155 1155 1155 Notes:

1. The HTC for 100°F and 325°F were determined by interpolation of available data.

2. Prandtl number, Pr, source is Reference [11].

3. Water properties, Specific Volume, source is Reference [12].

4. Viscosity properties source is Reference [13].

5. Conductivity of water properties, K, source is Reference [14].

6. This HTC is based on the maximum flowrate during the transient, which conservatively results in higher stresses.

7. The flow rate ramps up from zero to 12% flow; conservatively, the max flow is used for HTC.

8. The HTCs at the same temperatures vary due to differences in flow rate.

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Table 21: Path Locations(1)(2)

Path Description ASME Category Item No.

Component ID(s)

Comment 1

Hot Leg Nozzle-to-SG Shell B-D B3.130 3-100, 4-100 2

Hot Leg Nozzle Inside Radius N/A N/A N/A Note 3 3

Cold Leg Nozzle-to-SG Shell B-D B3.130 3-101, 3-102, 4-101, 4-102 4

Cold Leg Nozzle Inside Radius N/A N/A N/A Note 3 5

Stay Cylinder-to-SG Shell B-B B2.31 3-108 Note 4 6

Stay Cylinder-to-SG Shell B-B B2.31 4-108 Note 4 7

Stay Cylinder-to-Tubesheet B-B B2.40 3-107 Note 5 8

Stay Cylinder-to-Tubesheet B-B B2.40 4-107 Note 5 9

SG Shell-to-Tubesheet (Primary)

B-B B2.40 3-106 10 SG Shell-to-Tubesheet (Primary)

B-B B2.40 4-106 11 SG Shell-to-Tubesheet (Secondary)

C-A C1.30 41-104,42-104 12 Stub Barrel-to-Lower Shell C-A C1.10 41-105 Note 3 13 Lower Shell-to-Intermediate Shell C-A C1.10 42-105 Note 3 14 Intermediate Shell-to-Transition Cone C-A C1.10 41-106 15 Transition Cone-to-Upper Shell C-A C1.10 42-106 16 Upper Shell to Top Head Torus C-A C1.20 41-107 17 Top Head Torus-to-Top Head Dome C-A C1.20 42-107 Note 3 18 Economizer FW Nozzle-to-SG Shell (U2)

C-B C2.21 41-102,41-103, 42-102,42-103 19 Economizer FW Nozzle-to-Branch Boss (U1/3)

C-B C2.21 41-102,41-103, 42-102,42-103 20 Economizer FW Nozzle Inside Radius C-B C2.22 41-102-IR, 41-103-IR, 42-102-IR, 42-103-IR 21 Top Downcomer Blowdown Nozzle-to-SG Shell C-B C2.21 41-110,42-110 22 Top Downcomer Blowdown Nozzle Inside Radius C-B C2.22 41-110-IR, 42-110-IR Note 3 23 DC FW Nozzle-to-SG Shell C-B C2.21 41-109,42-109 24 DC FW Nozzle Inside Radius C-B C2.22 41-109-IR, 42-109-IR Note 3 25 Recirc Nozzle-to-SG Shell N/A N/A N/A Note 3 26 Recirc Nozzle Inside Radius C-B C2.22 N/A Note 3

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Path Description ASME Category Item No.

Component ID(s)

Comment 27 MS Nozzle-to-SG Shell C-B C2.21 41-114,41-115, 42-114,42-115 28 MS Nozzle-to Inside Radius C-B C2.22 41-114-IR, 41-115-IR 29 MS Nozzle-to Inside Radius C-B C2.22 42-114-IR, 42-115-IR Notes:

1.

Refer to Figures 8 through 21 for Path definitions.

2.

Model assumptions are listed in Section 4.0.

3.

Path not used since (a) not a required ASME inspection, (b) exempt from ASME inspection, and/or (c) not included in the APS inspection program.

4.

Unit 2 does not have this weld.

5.

Unit 2 has two welds on the stay cylinder.

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Table 22: Path Location Data Path Number OD (in) t (in)

Stress for Circ.

Cracks Stress for Axial Cracks 1

101.05 9.84266 Syy Szz 2

(Not used)

N/A N/A N/A 3

101.05 9.59219 Syy Szz 4

(Not used)

N/A N/A N/A 5

101.05 9.40963 Syy Szz 6

101.05 9.40963 Syy Szz 7

44.0 6.5 Syy Szz 8

44.0 6.5 Syy Szz 9

101.05 9.37556 Syy Szz 10 101.05 9.37556 Syy Szz 11 204.01(U1,3) 202.68(U2) 5.55284 4.84 Syy Szz 12 202.68 4.84 Syy Szz 13 202.68 4.84 Syy Szz 14 202.68 4.84 Syy Szz 15 243.78 5.78 Syy Szz 16 239.3 3.40711 Syy Szz 17 119.65 rad on dome (see 2nd run for radial) 5.28686 Vert 3.4 Radial Syy Szz Syy and Szz N/A 18 202.68(U2) 4.84 Syy Szz 19 25.5(U1,U3) 6.49606 Syy Szz 20 Path through Inside Nozz Radius 7.7026 Syy Szz 21 202.68 4.84 Syy Szz 22 (Not used)

N/A N/A N/A 23 239.8425 (on cone) 6.49896 Syy Szz 24 (Not used)

N/A N/A N/A 25 (Not used)

N/A N/A N/A 26 (Not used)

N/A N/A N/A 27 120.55 rad on dome 4.3 Syy Szz 28 Path through Inside Nozz Radius 21.34989 Syy Szz 29 Path from Inside Nozzle to Outside of Shell Weld 11.74621 Syy Szz Note: Cladding is excluded from all results.

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Figure 1. General Modeled Dimensions (Dimensions are obtained from the Reference [5] inputs, particularly the Reference [5c] through [5s]

drawings. Dimensions not shown on the drawings are scaled from the drawings as necessary.)

202.68 193.0 42 ID Primary Inlet Nozzle 2 X 30 ID Primary Outlet Nozzles 202.1 101.05 91.75 204.01 Unit 1, 3 82.25 202.68 Unit 2

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Figure 2. 3-D Finite Element Model (Model assumptions are listed in Section 4.0) 32 OD Steam Outlet Nozzles 4 Recirculation Nozzle w/Thermal Liner 6 Downcomer Feedwater Nozzle w/Thermal Liner 6 Downcomer Blowdown Nozzle 14 Feedwater Nozzles 42 ID Primary Inlet Nozzle 30 ID Primary Outlet Nozzles

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Figure 3. 3-D Primary Side Finite Element Model and Mesh Primary Primary Head Primary Primary Head Head Cladding Tubesheet Stay Stay Cylinder Cylinder and and Support Divider Plate Divider Plate (only used in only used in thermal thermal analysis)

Cold Side Cold Side Outlet Hot Side ot Side Ho Inlet

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Heat Transfer Coefficient Bulk Temperature Figure 4. Example of Applied Thermal Boundary Conditions for Thermal Transient Analyses Plant Loading transient shown, loads applied at time = 1,800 seconds.

(Units for HTC is BTU/sec-in2-°F, TBULK is °F)

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Figure 5. Example of Applied Mechanical Boundary Conditions and Pressure for Thermal Stress Analyses (includes end cap pressures on nozzles)

Plant Loading transient shown, loads applied at time = 1,800 seconds.

(Units for pressure is psi)

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Figure 6. Example of Temperature Contour, Heatup/Cooldown Transient (Time = 18,735 seconds)

(Units for temperature is °F)

(Note that the Divider Plate and Air Elements are in still in place.)

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Hoop Stress Axial Stress Figure 7. Example Stress Contours, Heatup/Cooldown Transient (Time = 18,735 seconds)

(Units for stress is psi)

(Note that the Cladding, Divider Plate, Air and Water Elements have been removed.)

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Figure 8 Path Locations, Lower Steam Generator (Model assumptions are listed in Section 4.0) 9 7

8 3

6 5

1 10 11 18-20 12

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Figure 9 Path Locations, Middle and Upper Steam Generator (Model assumptions are listed in Section 4.0) 13 14 23 15 16 17 27, 28 21

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Figure 10. Path Location 1, Hot Leg Inlet Nozzle Top Weld

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Figure 11. Path Location 3, Cold Leg Outlet Nozzle Top Weld

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Figure 12. Path Locations 5 and 6, Stay Cylinder Bottom Hot Leg and Cold Leg

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Figure 13. Path Locations 7,8, Stay Cylinder Top; Locations 9,10 Primary Shell Top; Location 11 Tube Sheet Top to Stub Barrel

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Figure 14. Path Locations 12 Stub Barrel to Lower Shell, 13 Lower Shell to Intermediate Shell

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Figure 15. Path Locations 14 Inter. Shell to Bottom of Transition Cone and 15 Transition Cone to Upper Shell

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Figure 16. Path Location 16 Upper Shell to Top Head Torus

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Figure 17. Path Location 17, Top Head Torus to Top Head Dome (Radial Direction)

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Figure 18. Path Location 18, FW Nozzle Top Weld to SG Shell Stub Barrel (Unit 2); 19 - FW Nozzle Weld to Branch Boss (Unit 1, 3); 20 - FW Nozzle Inside Radius - Top

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Figure 19. Path Location 21, Top Downcomer Blowdown Nozzle Top Weld to SG Shell

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Figure 20. Path Location 23 - Downcomer FW Nozzle Top Weld to SG Shell

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Figure 21. Path Location 27, 28, 29 - Mainsteam Nozzle, Top Weld to SG Shell, Inside Radius, Inside to Outside - Top

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COMPUTER FILES LISTING

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Input File for Thermal-Plus-Pressure Transient Runs and Post-Processing File Name Description PALO-VERDE-SG-GEOM 10-30-2024.inp Input file to construct model for the PWR steam generator primary head, tubesheet, stay cylinder, support skirt, hot leg nozzle, cold leg nozzle, secondary shell, economizer feedwater nozzle, downcomer blowdown nozzle, downcomer feedwater nozzle, recirculation nozzle and mainsteam nozzle finite element model THERMAL.INP Input file for thermal analyses for thermal transients TRNS.mac ANSYS Macro to perform the thermal transient analyses STRESS.INP Input file for stress analyses for thermal transients STR.mac ANSYS Macro to perform the stress analyses THM_#_mntr.inp Thermal analysis load step input file for thermal transients, which also include pressure loading for each load step, # = HUCD for Heatup/Cooldown, LOAD for Plant Loading, UNLD for Plant Unloading, TRIP for Reactor Trip Postpro.INP Input file for post-processing GenStress.mac ANSYS Macro for stress extraction GETPATH.TXT Input file for defining stress paths 1-29 (path 17 in vertical direction).

STR_#_LIN_P$.CSV Output files containing linearized stresses, # = HUCD for Heatup/Cooldown, LOAD for Plant Loading, UNLD for Plant Unloading, TRIP for Reactor Trip, $ = paths 1-29 STR_#_MAP_P$.CSV Output files containing mapped stresses, # = HUCD for Heatup/Cooldown, LOAD for Plant Loading, UNLD for Plant Unloading, TRIP for Reactor Trip, $ = paths 1-29 GETPATH.TXT Input file for defining stress path 17 in radial direction.

STR_#_COE_P17XYZ.CSV Output files containing linearized stresses, # = HUCD for Heatup/Cooldown, LOAD for Plant Loading, UNLD for Plant Unloading, TRIP for Reactor Trip, $ = paths 17, radial direction.

STR_#_MAP_P17XYZ.CSV Output files containing mapped stresses, # = HUCD for Heatup/Cooldown, LOAD for Plant Loading, UNLD for Plant Unloading, TRIP for Reactor Trip, $ = paths 17, radial directions.

Palo Verde Material Properties 09-24-2024.xlsx Excel Spreadsheet to calculate the effective material properties for perforated plate.

PVNGS Transient Def for Analysis12-02-2024.xlsx Transient Definition (Summarized in Table 14 to Table 17).

Enclosure Relief Request 74 ATTACHMENT 4 SI CALCULATION NO. 2300243.302, DETERMINISTIC AND PROBABILISTIC FRACTURE MECHANICS ANALYSES OF PBNGS UNITS 1, 2 AND 3 CE SYSTEM 80 STEAM GENERATOR WELDS AND COMPONENTS, REVISION 0

CALCULATION PACKAGE File No.: 2300243.302P Project No.: 2300243 Quality Program Type:

Nuclear Commercial PROJECT NAME:

PVNGS Inspection Optimization CONTRACT NO.:

PV1025387 CLIENT:

Arizona Public Service (APS)

PLANT:

PVNGS, Units 1, 2 and 3 CALCULATION TITLE:

Deterministic and Probabilistic Fracture Mechanics Analyses of PVNGS Units 1, 2 and 3 CE System 80 Steam Generator Welds and Components Document Revision Affected Pages Revision Description Project Manager Approval Signature & Date Preparer(s) &

Checker(s)

Signatures & Date 0

1 - 25 A A-2 Initial Issue Scott T. Chesworth 12/13/2024 Preparer:

Dilip Dedhia 12/13/2024 Checker:

Nathaniel G. Cofie 12/13/2024 1

11, 14, 17, 20, 21, 22, 23 Incorporated additional discussion and clarifications as documented in APS Comment Form Scott Chesworth 4/14/2025 Preparer:

Scott Chesworth 4/14/2025 Checker:

Nathaniel Cofie 4/14/2025 2

11, 14, 17, 20, 21, 22, 23 Removed discussion of Tubesheet Blowdown Nozzle Components41-100, 41-101,42-100, and 42-101 since APS will not be seeking relief for these components using this technical basis Scott Chesworth 5/5/2025 Preparer:

Scott Chesworth 5/5/2025 Checker:

Nathaniel Cofie 5/5/2025 PROPRIETARY INFORMATION This document contains Structural Integrity; client; or supplier proprietary information. This document may not be disclosed, wholly or in part, to any third parties without the prior written consent of Structural Integrity Associates, Inc.

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PROPRIETARY INFORMATION NOTICE THIS DOCUMENT CONTAINS PROPRIETARY INFORMATION. THE CLIENT MAY USE THE INFORMATION CONTAINED IN THIS DOCUMENT SOLELY FOR THEIR OWN INTERNAL PURPOSES. IF THE DOCUMENT IS SUBMITTED TO THE NUCLEAR REGULATORY COMMISSION (NRC), STRUCTURAL INTEGRITY ASSOCIATES, INC. WILL PROVIDE PROPRIETARY AND NON-PROPRIETARY VERSIONS OF THE DOCUMENT FOR NRC USE ALONG WITH THE REQUIRED LETTER STATING THE PERMITTED USE BY THE NRC. THIS DOCUMENT MAY NOT BE DISCLOSED, WHOLLY OR IN PART, TO ANY THIRD PARTIES WITHOUT THE PRIOR WRITTEN CONSENT OF STRUCTURAL INTEGRITY ASSOCIATES, INC.

This entire document is considered Proprietary. Proprietary References are identified with a P in the SI File Number.

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Table of Contents

1.0 BACKGROUND

AND OBJECTIVE............................................................................5 2.0 DFM EVALUATION...................................................................................................5 2.1 Technical Approach.......................................................................................5 2.2 Design Inputs.................................................................................................5 3.0 PFM EVALUATION...................................................................................................8 3.1 Technical Approach.......................................................................................8 3.2 Design Inputs.................................................................................................8 3.3 Evaluation......................................................................................................8 3.4 Results of PFM Evaluation and Discussions..................................................8

4.0 CONCLUSION

S........................................................................................................9

5.0 REFERENCES

..........................................................................................................9 COMPUTER FILES LISTING...................................................................... A-1

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List of Tables Table 1. PVNGS Unit 1 SG1(1) Inspected Components [3]..................................................11 Table 2. Summary of DFM Design Inputs...........................................................................12 Table 3. Path Description, Geometry and Stress Components...........................................13 Table 4. Transient Cycles...................................................................................................15 Table 5. Results of the PVNGS DFM Evaluation................................................................16 Table 6. Summary of PFM Design Inputs...........................................................................18 Table 7. Probability of Rupture (per year) and Probability of Leakage (per year) at 80 Years for PVGNS Inspection Scenario of (PSI+10+40+70)...............................................19 Table A-1. pc-Crack INPUT/OUTPUT FILES.................................................................... A-2 Table A-2. PROMISE INPUT/OUTPUT FILES................................................................. A-2 List of Figures Figure 1. PVNGS CE System 80 SG Components [4]........................................................21 Figure 2. Path Locations - SG Bottom [4]...........................................................................22 Figure 3. Path Locations - Overall SG [4]...........................................................................23 Figure 4. Weld Residual Stress Distribution.......................................................................24 Figure 5. Semi-Elliptical Axial Crack in a Cylinder Model....................................................24 Figure 6. Semi-Elliptical Circumferential Crack in a Cylinder Model....................................24 Figure 7. Nozzle Corner Crack Model.................................................................................25 Figure 8. ASME Section XI Fracture Toughness Curve for Vessels vs. Experimental Data Points

[14, 15]..............................................................................................................25

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1.0 BACKGROUND

AND OBJECTIVE Arizona Public Service (APS) plans to request relief from the Nuclear Regulatory Commission (NRC) to increase the inspection interval of several steam generator (SG) welds at Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, 3. The SGs at PVNGS are CE Model 80 design which is not addressed in the Reference [1, 2] EPRI technical basis reports. The configuration of the PVNGS System 80 SG is shown in Figure 1. The CE Model 80 SG configuration at PVNGS includes a stay cylinder welded to the bottom head with a divider plate that is mechanically attached to the stay cylinder and the bottom head as shown in Figure 1. This bottom head design is different from that considered in Reference [2], which has the traditional divider plate configuration. In addition, the SGs at PVNGS have two main steam nozzles oriented at an angle on the top head rather than a single main steam nozzle at top dead center of the top head considered in Reference [1].

PVNGS has two SGs per unit. Typical SG welds/components (for Unit 1, SG No. 1) from Reference [3]

are listed in Table 1, along with the associated ASME Code,Section XI Item Numbers from Reference

[5]. Plant-specific stress analyses for the CE System 80 SG at PVNGS Units 1, 2 and 3 have been performed in Reference [4].

The objective of this calculation is to perform deterministic fracture mechanics (DFM) and probabilistic fracture mechanics (PFM) analyses of the PVNGS CE System 80 SG welds and components using the technical approaches from References [1, 2] together with the plant-specific stress analyses results from Reference [4] and other relevant design inputs. The DFM evaluation will determine how long a postulated flaw will take to reach the allowable flaw size while the PFM evaluation will determine the probabilities of failure at these weld locations.

2.0 DFM EVALUATION 2.1 Technical Approach The technical approach used in the DFM evaluation is to postulate an initial flaw size equivalent to the relevant ASME Code,Section XI acceptance standard [5]. The fatigue crack growth (FCG) law from ASME Code,Section XI, Appendix A, Paragraph A-4300 [5], with the through-wall stress distributions from Reference [4] and appropriate fracture mechanics models, is then used to determine the length of time for the postulated initial flaw to grow to a depth of 80% of the wall thickness (assumed to equate to leakage in this evaluation) or the depth at which the allowable fracture toughness (KIC) is reached, whichever is less.

2.2 Design Inputs The design inputs used in the DFM evaluation are summarized in Table 2 and discussed in the following sections.

2.2.1 Geometry The components considered in the evaluation are presented in Table 1 and Figure 1. Component geometry (OD and thickness), along with the paths were stresses were extracted in Reference [4], are provided in Table 3. Figures 2 and 3 show these Stress Paths.

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2.2.2 Initial Crack Size and Shape For all components, an initial crack size of 5.2% of the wall thickness (which corresponds to the most conservative flaw acceptance standard for these components from Tables IWB-3510-1 and IWC-3510-1 of ASME Code,Section XI [5]) was used in the DFM evaluation. This initial crack depth is the maximum from Tables IWB-3510-1 and IWC-3510-1, with an associated crack aspect ratio (half crack length -to-crack depth) of 1.0. This crack shape results in the most conservative initial stress intensity factor (K) at the deepest point of the crack. The aspect ratio is then subsequently allowed to vary during the crack growth process.

2.2.3 Applied Stresses and Transient Cycles 2.2.3.1 Operating Transient Stresses and Cycles The applied stresses consist of through-wall stresses due to pressure and the thermal transients described in Reference [4]. The files for the through-wall stress distributions for the various Stress Paths used in the evaluation are documented in Reference [4]. The stress components used in the evaluation for each Stress Path are shown in Table 3.

Plant-specific projected 60-year transient cycles for PVNGS Units 1, 2 and 3 were obtained from References [6 - 8] and are shown in Table 4. Bounding numbers of cycles for each transient used in this evaluation are also shown in Table 4.

2.2.3.2 Weld Residual Stresses Pressure vessel welds typically receive post-weld heat treatment (PWHT) to reduce the effects of weld residual stresses. In this evaluation, weld residual stresses remaining after PWHT were characterized in the form of a cosine distribution with a peak stress of 8 ksi [9], as shown in Figure 4. This is consistent with the approach used in Reference [2].

2.2.3.3 Cladding Stresses Some Stress Paths shown in Figures 2 and 3 have cladding at the surface. Cladding at the affected locations was modeled in Reference [4] as part of the stress analyses. Hence, the effect of cladding stresses has already been addressed in Reference [4] stress analyses.

2.2.4 Fracture Mechanics Models In this evaluation, all pre-existing flaws were conservatively assumed to be surface flaws. Three different fracture mechanics models were used for axial, circumferential and nozzle corner flaws. For an axial flaw, the stress intensity factor (K) solution for an internal, semi-elliptical crack from API-579/ASME-FFS-1 [10] was used. This model is shown in Figure 5. The aspect ratio (a/c) is allowed to vary during crack growth.

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Similarly, for a circumferential flaw, the K solution for an internal, semi-elliptical crack from API-579/ASME-FFS-1 [10] was used. This model is shown in Figure 6. The aspect ratio (a/c) was allowed to vary during crack growth.

For a nozzle corner crack, a weight function-based K solution from Reference [11] was used. The crack is assumed as a circular-arc crack and the aspect ratio is fixed during crack growth. This model is shown in Figure 7.

These models are consistent with those used in References [1, 2]. A large radius-to-thickness (R/t) ratio was used to represent the stay cylinder-to-head weld since it approached a flat plate rather than a cylinder.

These fracture mechanics models were incorporated into an SI-developed software, TTIFFANY [12], that determines the K distribution due to through-wall stress profiles for both circumferential and axial cracks. The outputs of TIFFANY DUHWKHPD[LPXPDQGPLQLPXP.GLVWULEXWLRQVDVZHOODVWKH.

distribution, for each transient.

2.2.5 Fracture Toughness The materials under consideration are all ferritic steels; therefore, the fracture toughness curve provided in ASME Code,Section XI, Appendix A, Figure A-4200-1 [5] was used for this evaluation. For the transients considered in Reference [4], the minimum temperature experienced across all transients is 70°F from the heatup/cooldown case. However, at this temperature, the pressure is zero. At full power where the maximum K occurs, the temperature is 550°F. This full power temperature will therefore be used to determine the fracture toughness. The maximum RTNDT for the plates and nozzles of PVNGS Units 1, 2 and 3 SGs is 10°F for SG Nos. 1 and 2 at Unit 2 [13, Tables 5.2-21A and 5.2-26A]. The minimum possible temperature to use when entering the ASME Code,Section XI, Figure A-4200-1 [5] is (550°F - 10°F) = 540°F. This temperature is greater than the temperature of the end of the KIC curve shown in Figure A-4200-1, so an upper shelf fracture toughness of at least 22NVL¥LQ003D¥PZDV

used. Figure 8 [14, 15] shows the fracture toughness of vessel steels as a function of temperature and shows that the ASME Code,Section XI fracture toughness is a reasonable lower bound.

2.2.6 Fatigue Crack Growth Law The FCG law for ferritic steels, as defined in ASME Code,Section XI, Appendix A, Paragraph A-4300

[5], was used in the evaluation. The fatigue crack growth calculations are performed using the SI-developed fracture mechanics program pc-CRACK [16].

2.3 Results of Deterministic Fracture Mechanics Evaluation The results of the DFM evaluation are summarized in Table 5. The table shows that the periods required for hypothetical postulated flaws to leak are more than 200 years at all Stress Paths, which indicates that all the evaluated components are very flaw tolerant. Table 5 also shows that the maximum K values for all locations are below the fracture toughness of NVL¥LQ after 80 years with adequate margins.

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3.0 PFM EVALUATION 3.1 Technical Approach The PFM evaluation was performed consistent with the evaluation presented in References [1, 2].

PROMISE, Version 2.0 [17] was used to perform the PFM evaluations. The evaluation considered the specific PSI/ISI scenarios for PVNGS Units 1, 2 and 3.

3.2 Design Inputs The design inputs used for the PFM evaluation are shown in Table 6 and are consistent with those Used in References [1, 2], except for the PSI/ISI scenario, the plant-specific geometry and the operating transients/cycles. For the PVNGS replacement SGs, PSI examinations have been performed followed by ISI examinations over one completed 10-year interval. The PSI/ISI scenario is therefore PSI plus one 10-year ISI examination to be followed by two 30-year ISI deferrals (PSI+10+40+70). This PVNGS plant-specific inspection scenario is shown in Table 6 and was used for the evaluation.

3.3 Evaluation The evaluation was performed using the PPROMISE Code, Version 2.0 [17] for the PVNGS plant-specific inspection scenario as discussed above. Sensitivity studies and inspection coverage are also addressed.

3.4 Results of PFM Evaluation and Discussions The results of the PFM evaluation are presented in Table 7 for the PVNGS plant-specific inspection scenario. This table shows that with PVGNS inspection scenario, the probabilities of rupture and leakage at all locations are below the acceptance criteria of 1.0x10-6 after 80 years of plant operation by at least three orders of magnitude, confirming the very high flaw tolerance of the PVNGS SG components.

In the sensitivity studies performed in References [1, 2], fracture toughness and stress were found to be the critical parameters. It was shown in Tables 8-13 through 8-16 of Reference [1] that by reducing the fracture toughness to 80 ksi and increasing all stresses (including transient stresses) by a factor of 2.2, the acceptance criteria is still met. Similarly, in Tables 8-12, 8-14, 8-16 and 8-18 of Reference [2], it was shown that by reducing the fracture toughness to 80 NVL¥LQ and increasing all stresses (including transient stresses) by a factor of 1.25, the acceptance criteria is met. The base cases used in these sensitivity studies have higher probabilities of rupture and leakage than those determined for the PVNGS-specific components shown in Table 7. Hence, it follows that the same sensitivity studies for the PVNGS components would also result in favorable results compared to the acceptance criteria.

Some SG components at PVNGS have limited inspection coverage. The minimum coverage for the three PVNGS units is associated with an examination performed on an Item No. B2.31 component at Unit 3, which had an inspection coverage of 59.5% [18]. An evaluation was performed in Reference

[19] to address coverage of SG components on a generic basis. It was determined in Table 4 of Reference [19] that coverage as low as 25% is acceptable. The coverages for all PVNGS SG components are above this value and are therefore acceptable.

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4.0 CONCLUSION

S From the PFM and DFM evaluations, the following conclusions are made:

x The DFM evaluation demonstrated that it takes very long operating period (over 200 years) for a postulated initial flaw (with a depth equal to the ASME Code,Section XI acceptance standards) to propagate through 80% of the wall thickness (assumed as equivalent to leakage for this study). After 80 years, the maximum K obtained from the analysis remains below the ASME Code,Section XI allowable fracture toughness, which indicates that the CE Model 80 SG components at PVNGS are very flaw tolerant.

x From the PFM evaluations, it was demonstrated that PVNGS plant-specific inspection scenario of (PSI+10+40+70), the failure probabilities (in terms of both rupture and leakage) are significantly below the acceptance criterion of 1.0x10-6 failures per year after 80 years of operation confirming the high flaw tolerance of the PVNGS SG components.

x Sensitivities studies in PFM evaluation were addressed by comparing the PVNGS specific PFM results with those used in the sensitivity studies in Reference [1, 2] and found to be acceptable.

x The minimum coverage of 59.5% for the SG components at PVNGS exceeds the minimum coverage of 25% justified in Reference [19] and is therefore acceptable.

5.0 REFERENCES

1. Technical Bases for Inspection Requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Nozzle Inside Radius Sections. EPRI, Palo Alto, CA: 2019.

3002014590, ADAMS Accession No. ML19347B107.

2. Technical Bases for Inspection Requirements for PWR Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head, and Tubesheet-to-Shell Welds. EPRI, Palo Alto, CA: 2019. 3002015906, ADAMS Accession No. ML20225A141.

3. PV Units 1_2_3 PZR and SG welds and nozzles.xlsx, SI File No. 2300243.201.

4. SI Calculation 2300243.301P, Rev. 0, Finite Element Model Development and Thermal/Mechanical Stress Analysis of PVNGS Units 1, 2, 3 Steam Generator Components (PROPRIETARY).

5. ASME Boiler and Pressure Vessel Code,Section XI, 2017 Edition.

6. SI Calculation FP-PV-326 Revision 0, Palo Verde Unit 1 FP4 Update Through 11/1/2023 - RFO 24.

7. SI Calculation FP-PV-325 Revision 0, Palo Verde Unit 2 FP4 Update Through 4/30/2023 - RFO 24.

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8. SI Calculation FP-PV-324 Revision 0, Palo Verde 2022 Unit 3 FP4 Update Through 10/31/2022-RFO 23.

9. Simonen, F. A. and Johnson, K. I., Effects of Residual Stresses and Underclad Flaws on the Reliability of Reactor Pressure Vessels, PVP-Vol. 251, Reliability and Risk in Pressure Vessels and Piping, ASME PVP Conference, 1993.

10. API Standard 579-1/ASME FFS-1, Fitness-for-Service, Second Edition, June 2016.

11. Structural Integrity Associates Calculation Package, Stress Intensity Factors (SIFs) for Nozzle Corner Cracks, DEV1801.302, 3/12/2018.

12. SSI-TIFFANY 3.2, Structural Integrity Associates, April 2020.

13. PVNGS Updated FSAR, Revision 22A, February 2024, SI File No. 2300243.211.

14. M. Kirk and M. Erickson, Assessment of the Fracture Toughness of Ferritic Steel Fracture Toughness on or near the Lowe Shelf, Paper No. PVP2015-45850, Proceedings of the ASME Pressure Vessels and Piping Conference, July 19-23, 2015, Boston, MA, USA.

15. Application of Master Curve Fracture Toughness Methodology for Ferritic Steels. EPRI, Palo Alto, CA: 1999. TR-108390, Revision 1.

16. ppc-CRACK 5.0, Version Control No. 5.0.0.0, Structural Integrity Associates, January 2021.

17. Structural Integrity Associates Report DEV1806.402, PROMISE 2.0 Theory and Users Manual, Revision 1.

18. Examination Results, SI File No. 2300243.206.

19. N. G. Cofie, D. Dedhia, S, T. Chesworth, D. J. Shim, and R. Grizzi, Technical Basis for Inspection Optimization and Deferral of PWR Steam Generator Component Examinations, Paper No. PVP2023-105958, Proceedings of the ASME 2023 Pressure Vessels & Piping Conference, PVP2023, July 16-21, 2023, Atlanta, Georgia, USA.

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Table 1. PVNGS Unit 1 SG1(1) Inspected Components [3]

ASME Category ASME Item No.

Component ID Component Description B-B B2.31 3-108 Circumferential Shell Weld B-B B2.40 3-106 Tubesheet to Stay Cylinder Extension Weld B-B B2.40 3-107 Tubesheet to Head B-D B3.130 3-100 Nozzle to Vessel Weld B-D B3.130 3-101 Nozzle to Vessel Weld B-D B3.130 3-102 Nozzle to Vessel Weld C-B C2.21 41-100(2)

Nozzle to tubesheet C-B C2.21 41-101(2)

Nozzle to tubesheet C-B C2.21 41-102 Nozzle to vessel C-B C2.22 41-102-IR Nozzle IR C-B C2.21 41-103 Nozzle to vessel C-B C2.22 41-103-IR Nozzle IR C-A C1.30 41-104 SG1 Shell to Tube Sheet C-A C1.10 41-105 SG1 Shell to Conical Weld C-A C1.10 41-106 SG1 Shell to Conical Weld C-A C1.20 41-107 SG1 Shell to Head C-B C2.21 41-109 SG1 to Nozzle C-B C2.21 41-110 Nozzle to vessel C-B C2.21 41-114 Nozzle to vessel C-B C2.22 41-114-IR Nozzle IR C-B C2.21 41-115 Nozzle to vessel C-B C2.22 41-115-IR Nozzle IR Notes:

1. Unit 1, SG 1 information is typical and considered applicable to other SGs and Units.

2. APS will not be seeking relief for these components using this technical basis.

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Table 2. Summary of DFM Design Inputs Input Value Geometry From Table 3 Initial Crack Size 5.2% of the thickness, c/a = 1 Fracture toughness 220 ksiin Fatigue crack growth law ASME Code,Section XI, Appendix A, Paragraph A-4300 Operating Transient Stresses From Reference [4]

Operating Transient Cycles From Table 4 Residual stresses Cosine curve with 8 ksi peak (Figure 4); 30 ksi maximum and minimum stress

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Table 3. Path Description, Geometry and Stress Components Description of Location ASME Category Item Number Path Number Weld (W) or Nozzle Inside Radius (N)

OD (in) t (in)

Stress for Circ.

Cracks Stress for Axial Cracks Hot Leg Nozzle-to-SG Shell B-D B3.130 1

W 101.05 9.84 Syy Szz Hot Leg Nozzle Inside Radius N/A N/A 2(1)

N 101.05 11.15 Syy Szz Cold Leg Nozzle-to-SG Shell B-D B3.130 3

W 101.05 9.59 Syy Szz Cold Leg Nozzle Inside Radius N/A N/A 4(1)

N 101.05 10.68 Syy Szz Stay Cylinder-to-SG Shell B-B B2.31 5

W 101.05 9.41 Syy Szz Stay Cylinder-to-SG Shell B-B B2.31 6

W 101.05 9.41 Syy Szz Stay Cylinder-to-Tubesheet B-B B2.40 7

W 44.30 6.5 Syy Szz Stay Cylinder-to-Tubesheet B-B B2.40 8

W 44.30 6.5 Syy Szz SG Shell-to-Tubesheet (Primary)

B-B B2.40 9

W 101.05 9.38 Syy Szz SG Shell-to-Tubesheet (Primary)

B-B B2.40 10 W

101.05 9.38 Syy Szz SG Shell-to-Tubesheet (Secondary)

C-A C1.30 11 W

204.01 5.55 Syy Szz Stub Barrel-to-Lower Shell C-A C1.10 12(1)

W 202.68 4.84 Syy Szz Lower Shell-to-Intermediate Shell C-A C1.10 13(1)

W 202.68 4.84 Syy Szz Intermediate Shell-to-Transition Cone C-A C1.10 14 W

202.68 4.84 Syy Szz Transition Cone-to-Upper Shell C-A C1.10 15 W

243.78 5.78 Syy Szz Upper Shell to Top Head Torus C-A C1.20 16 W

239.30 3.41 Syy Szz

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Description of Location ASME Category Item Number Path Number Weld (W) or Nozzle Inside Radius (N)

OD (in) t (in)

Stress for Circ.

Cracks Stress for Axial Cracks Top Head Torus-to-Top Head Dome C-A C1.20 17(1)

W 119.65 3.49 Syy Szz Economizer FW Nozzle-to-SG Shell (U2)

C-B C2.21 18 W

202.68 4.84 Syy Szz Economizer FW Nozzle-to-Branch Boss (U1/3)

C-B C2.21 19 W

25.5 6.50 Syy Szz Economizer FW Nozzle Inner Radius C-B C2.22 20 N

100.00 7.70 Syy Szz Top Downcomer Blowdown Nozzle-to-SG Shell C-B C2.21 21 W

202.68 4.84 Syy Szz Top Downcomer Blowdown Nozzle Inner Radius C-B C2.22 22(1)

N 100.00 6.83 Syy Szz DC FW Nozzle-to-SG Shell C-B C2.21 23(1)

W 239.84 6.50 Syy Szz DC FW Nozzle Inner Radius C-B C2.22 24(1)

N 100.00 8.01 Syy Szz Recirc Nozzle-to-SG Shell N/A N/A 25(1)

W 243.56 5.78 Syy Szz Recirc Nozzle Inner Radius C-B C2.22 26 N

100.00 7.48 Syy Szz MS Nozzle-to-SG Shell C-B C2.21 27 W

120.55 4.30 Syy Szz MS Nozzle-to Inside Radius C-B C2.22 28 N

100.00 21.35 Syy Szz MS Nozzle-to Inside Radius C-B C2.22 29 N

100.00 11.75 Syy Szz Note:

1. Path not used since (a) not a required ASME inspection, (b) exempt from ASME inspection, and/or (c) not included in the APS inspection program.

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Table 4. Transient Cycles Transient(s) Considered in Reference [4]

Projected Unit 1

60-Year Cycles [6]

Projected Unit 2

60-Year Cycles [7]

Projected Unit 3 60-Year Cycles [8]

Bounding 60-Year Cycles Minimum Pressure (psi)

Maximum Pressure (psi)

RCS Heatup / RCS Cooldown 86 / 86 78 / 78 78 / 78 120 0

1155 Pressurizer Heatup / Pressurizer Cooldown 115 / 115 110 / 108 110 / 110 120 0

1155 Loading (40°F @ 875 gpm FW to SG-1 or SG-2) 8 57 63 120 1014 1137 Unloading (100°F @ 875 gpm FW to SG-1(or SG-2) 40 1

1 120 1055 1177 All Reactor Trips 107 85 83 120 1055 1220

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Table 5. Results of the PVNGS DFM Evaluation Case ID (1)

Years to Leak Max. K at 80

<HDUVNVL¥LQ

P1A

>200 10.54 P1C

>200 33.30 P2N(2)

>200 42.66 P3A

>200 9.63 P3C

>200 32.32 P4N(2)

>200 40.96 P5A

>200 31.12 P5C

>200 29.34 P6A

>200 30.59 P6C

>200 28.87 P7A

>200 18.64 P7C

>200 9.05 P8A

>200 15.14 P8C

>200 9.05 P9A

>200 17.35 P9C

>200 14.02 P10A

>200 32.35 P10C

>200 31.03 P11A

>200 26.09 P11C

>200 22.56 P12A(2)

>200 14.94 P12C(2)

>200 22.56 P13A(2)

>200 15.50 P13C(2)

>200 23.21 P14A

>200 13.54 P14C

>200 24.01 P15A

>200 24.38 P15C

>200 22.18 P16A

>200 15.07 P16C

>200 18.20 P17A(2)

>200 16.00 P17C2)

>200 15.47

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Case ID(1)

Years to Leak Max. K at 80

<HDUVNVL¥LQ

P18A

>200 6.22 P18C

>200 26.98 P19A

>200 81.88 P19C

>200 118.70 P20N

>200 131.74 P21A

>200 8.43 P21C

>200 29.29 P22N

>200 48.07 P23A(2)

>200 7.25 P23C(2)

>200 26.62 P24(21)N

>200 76.15 P25A(2)

>200 7.01 P25C(2)

>200 27.00 P26N

>200 48.16 P27A

>200 7.66 P27C

>200 15.22 P28N

>200 12.09 P29N

>200 24.13 Notes:

1. The Case ID terminology is as follows: P1 through P29 represent the crack paths (see Figures 2 and 4); A for axial part-through-wall crack; C for circumferential part-through-wall crack; N for nozzle corner crack.

2. For information only since path location (a) not a required ASME inspection, (b) exempt from ASME inspection, and/or (c) not included in the APS inspection program.

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Table 6. Summary of PFM Design Inputs Input Value No. of Realizations Epistemic = 1, Aleatory = 10 million No. of cracks per weld 1, constant Crack depth distribution PVRUF Crack length distribution NUREG/CR-6817-R1

)UDFWXUHWRXJKQHVVNVL¥LQ

Normal (200,5)

Inspection coverage 100%

PSI Yes ISI 10, 40, and 70 years POD Curve BWRVIP-108, Figure 8-6 Fatigue crack growth law and threshold A-4300, log-normal, Second Parameter = 0.467 Operating Transient Stresses From Reference [4]

Operating Transient Cycles From Table 4 Uncertainties on transients None Weld residual stresses (ksi)

Cosine Curve (8, 8), constant (not random)

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Table 7. Probability of Rupture (per year) and Probability of Leakage (per year) at 80 Years for PVGNS Inspection Scenario of (PSI+10+40+70)

PSI/ISI Scenario PSI+10+40+70 Case ID(1)

Prob. Leak

@ 80 Prob. Rupture

@ 80 P1A 1.25E-09 1.25E-09 P1C 1.25E-09 1.25E-09 P2N(2) 1.25E-10 1.25E-10 P3A 1.25E-09 1.25E-09 P3C 1.25E-09 1.25E-09 P4N(2) 1.25E-10 1.25E-10 P5A 1.25E-09 1.25E-09 P5C 1.25E-09 1.25E-09 P6A 1.25E-09 1.25E-09 P6C 1.25E-09 1.25E-09 P7A 1.25E-09 1.25E-09 P7C 1.25E-09 1.25E-09 P8A 1.25E-09 1.25E-09 P8C 1.25E-09 1.25E-09 P9A 1.25E-09 1.25E-09 P9C 1.25E-09 1.25E-09 P10A 1.25E-09 1.25E-09 P10C 1.25E-09 1.25E-09 P11A 1.25E-09 1.25E-09 P11C 1.25E-09 1.25E-09 P12A(2) 1.25E-09 1.25E-09 P12C(2) 1.25E-09 1.25E-09 P13A(2) 1.25E-09 1.25E-09 P13C(2) 1.25E-09 1.25E-09 P14A 1.25E-09 1.25E-09 P14C 1.25E-09 1.25E-09 P15A 1.25E-09 1.25E-09 P15C 1.25E-09 1.25E-09 P16A 1.25E-09 1.25E-09 P16C 1.25E-09 1.25E-09 P17A(2) 1.25E-09 1.25E-09 P17C(2) 1.25E-09 1.25E-09

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PSI/ISI Scenario PSI+10+40+70 Case ID(1)

Prob. Leak

@ 80 Prob. Rupture

@ 80 P18A 1.25E-09 1.25E-09 P18C 1.25E-09 1.25E-09 P19A 1.25E-09 1.25E-09 P19C 1.25E-09 8.75E-09 P20N 1.25E-10 1.25E-10 P21A 1.25E-09 1.25E-09 P21C 1.25E-09 1.25E-09 P22N 1.25E-10 1.25E-10 P23A(2) 1.25E-09 1.25E-09 P23C(2) 1.25E-09 1.25E-09 P24N(2) 1.25E-10 1.25E-10 P25A(2) 1.25E-09 1.25E-09 P25C(2) 1.25E-09 1.25E-09 P26N 1.25E-10 1.25E-10 P27A 1.25E-09 1.25E-09 P27C 1.25E-09 1.25E-09 P28N 1.25E-10 1.25E-10 P29N 1.25E-10 1.25E-10 Notes:

1. The Case ID terminology is as follows: P1 through P29 represent the crack paths (see Figures 2 and 4); A for axial part-through-wall crack; C for circumferential part-through-wall crack; N for nozzle corner crack.

2. For information only since path location (a) not a required ASME inspection, (b) exempt from ASME inspection, and/or (c) not included in the APS inspection program.

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Figure 1. PVNGS CE System 80 SG Components [4]

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Figure 2. Path Locations - SG Bottom [4]

(The Unit 2 primary side has two welds on the stay cylinder and no dollar weld on the lower shell, while the Units 1 and 3 stay cylinder have one weld and a dollar weld on the lower shell adjacent to the SG support attachment. One model is used to represent all three units. The welds are not specifically modeled and base material properties are used. The most critical location in the stay cylinder was used to represent all three units. The effect of this assumption on the results is minimal.)

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Figure 3. Path Locations - Overall SG [4]

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Figure 4. Weld Residual Stress Distribution Figure 5. Semi-Elliptical Axial Crack in a Cylinder Model Figure 6. Semi-Elliptical Circumferential Crack in a Cylinder Model

-10

-5 0

5 10 0

0.2 0.4 0.6 0.8 1

x/t Stress (ksi) p

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Figure 7. Nozzle Corner Crack Model Figure 8. ASME Section XI Fracture Toughness Curve for Vessels vs. Experimental Data Points [14, 15]

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COMPUTER FILES LISTING

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Table A-1. pc-Crack INPUT/OUTPUT FILES File Name Description Pxyznn.(pcf, rpt) x - W for weld, N for Nozzle y - C for circumferential, A for axial orientation nn - Path number

• .pcf - Input file

• .rpt - Output file Table A-2. PROMISE INPUT/OUTPUT FILES Zip File Name Description Pxyznn.(pcf, rpt) x - W for weld, N for Nozzle y - C for circumferential, A for axial orientation nn - Path number

• .vnz3 - Input file

• .rpt - Output file

Enclosure Relief Request 74 ATTACHMENT 5 RESULTS OF INDUSTRY SURVEY

Enclosure Relief Request 74 1

Overall Industry Inspection Summary for Steam Generator Code Items B2.31, B2.32, B2.40, B3.130, C1.10, C1.20, and C1.30 The results of an industry survey of past inspections of SG nozzle-to-shell welds, inside radius sections and shell welds are summarized in Reference [5-1]. Table 5-1 provides a summary of the combined survey results for Item Nos. B2.31, B2.32 (see Table Note 3), B.240, B3.130, C1.10, C1.20, and C1.30. The results of the industry survey identified numerous steam generator (SG) examinations being performed with no service-induced flaws being detected. Performing these examinations adversely impact outage activities including worker exposure, personnel safety, and radwaste. A total of 74 domestic and international boiling water reactor (BWR) and pressurized water reactor (PWR) units responded to the survey and provided information representing all PWR plant designs currently in operation in the United States. This included 2-loop, 3-loop, and 4-loop PWR designs from each of the PWR nuclear steam supply system (NSSS) vendors (i.e.,

Babcock and Wilcox (B&W), Combustion Engineering (CE), and Westinghouse). A total of 1374 examinations for the components of the affected Item Nos. were conducted, with 1148 of these specifically for PWR components. The majority of PWR examinations were performed on SG welds.

A relatively small number of flaws were identified during these examinations which required flaw evaluation. None of these flaws were found to be service-induced. For Item No. B2.40, examinations at two units at a single plant site identified multiple flaws exceeding the acceptance criterion of ASME Code Section XI; however, these were determined to be subsurface-embedded fabrication flaws and non-service-induced (see Table Note 1). For Item No. C1.20, two PWR units reported flaws exceeding the acceptance criteria of ASME Code,Section XI. In the first unit, a single flaw was identified, and was evaluated as an inner diameter surface imperfection. Reference [5-3] indicates that this was a spot indication with no measurable through-wall depth. This indication is therefore not considered to be service-induced but rather fabrication-related.

A flaw evaluation per IWC-3600 was performed for this flaw and it was found to be acceptable for continued operation. In the second unit, multiple flaws were identified (see Table Note 2). As discussed in References [5-4] and [5-5], these flaws were most likely subsurface weld defects typical of thick vessel welds and not service-induced. A flaw evaluation for IWC-3600 was performed for these flaws and they were found to be acceptable for continued operation.

Enclosure Relief Request 74 2

Table 5-1. Summary of Survey Results for SG Nozzle-to-Shell, Inside Radius Section, and Shell Weld Components Item No.

No. of Examinations No. of Reportable Indications BWR PWR Total BWR PWR Total B2.31 0

30 30 0

0 0

B2.32 (Note 3) 0 13 13 0

0 0

B2.40 0

183 183 0

Note 1 Note 1 B3.130 0

135 135 0

0 0

C1.10 140 305 445 0

0 0

C1.20 54 319 373 0

Note 2 Note 2 C1.30 32 163 195 0

0 0

Totals 226 1148 1374 0

Notes 1 and 2 Notes 1 and 2 Notes:

1. Two PWR W-2 Loop units at a single plant reported multiple subsurface embedded fabrication flaws.

2. A single PWR W-2 Loop unit reported multiple flaws [5-4, 5-5].

3. Item No. B2.32 was evaluated in the Reference [5-1] technical basis and included in the industry survey, but is not contained in the scope of this alternative request.

Enclosure Relief Request 74 3

Overall Industry Inspection Summary for Steam Generator Code Items C2.21, C2.22, and C2.32 The results of an industry survey of past inspections of SG main steam (MS) and feedwater (FW) nozzles are summarized in Reference [5-2]. Table 5-2 provides a summary of the combined survey results for Item Nos. C2.22, C2.21, and C2.32 (see Table Note 1). The results identify that SG MS and FW Nozzle-to-Shell Welds and Nozzle Inside Radius Section examinations being performed with no service-induced flaws being detected. Performing these examinations adversely impact outage activities including worker exposure, personnel safety, and radwaste. A total of 74 domestic and international BWR and PWR units responded to the survey and provided information representing all PWR plant designs currently in operation in the U.S. This included 2-loop, 3-loop, and 4-loop PWR designs from each of the PWR NSSS vendors (i.e., B&W, CE, and Westinghouse). A total of 727 examinations for Item Nos. C2.21, C2.22, and C2.32 (see Table Note 1) components were conducted, with 563 of these specifically for PWR components. The majority of the PWR examinations were performed on SG MS and FW nozzles. Only one PWR examination identified two (2) flaws that exceeded ASME Code,Section XI acceptance criteria. The flaws were linear indications of 0.3 and 0.5 in length and were detected in a MS nozzle-to-shell weld using magnetic particle examination techniques. The indications were dispositioned by light grinding (ADAMS Accession No. ML13217A093).

Table 5-2. Summary of Survey Results for SG Main Steam and Feedwater Nozzle Components Plant Type Number of Units Number of Examinations Number of Reportable Indications BWR 27 164 0

PWR 47 563 2

Totals 74 727 (Note 1) 2 Notes:

1. Item No. C2.32 was evaluated in the Reference [5-2] technical basis and included in the industry survey, but is not contained in the scope of this alternative request.

Overall Industry Inspection Summary for Pressurizer Code Items B2.11, B2.12, B2.21, B2.22 and B3.110 The results of an industry survey of past inspections of pressurizer welds are summarized in Reference [5-6]. Table 5-3 provides a summary of the combined survey results for Item Nos. B2.11, B2.12, B2.21, B2.22 and B3.110. The results identify that pressurizer examination of the items adversely impact outage activities including worker

Enclosure Relief Request 74 4

exposure, personnel safety, and radwaste. A total of 74 domestic and international PWR units responded to the survey and provided information representing all PWR plant designs currently in operation in the U.S. This included 2-loop, 3-loop, and 4-loop PWR designs from each of the PWR nuclear steam supply system (NSSS) vendors (i.e.,

Babcock and Wilcox (B&W), Combustion Engineering (CE), and Westinghouse). A total of 1,162 examinations for the components of the affected Item Nos. were conducted on PWR pressurizer components.

A small number of flaws were identified during these examinations which required flaw evaluation. None of these flaws were found to be service induced. Out of a total of 1,162 examinations identified by the plants that responded to the survey that have been performed on the above item numbers, only four examinations (for Item No. B2.11), at two units of a single plant site, identified flaws exceeding the acceptance criteria of ASME Code,Section XI. Flaw evaluations were performed to show acceptability of these indications and follow-on examinations showed no change in flaw sizes since the original inspections. No other indications were identified in any in-scope components.

Table 5-3. Summary of Survey Results for Pressurizer Components Item No.

No. of Examinations No. of Reportable Indications B2.11 269 4 (1)

B2.12 269 0

B2.21 4

0 B2.22 30 0

B3.110 590 0

Note:

(1) Flaw evaluations were performed to show acceptability of these indications and follow-on examinations showed no change in flaw sizes since the original inspections. None of these flaws were found to be service induced.

Enclosure Relief Request 74 5

References 5-1.

Technical Bases for Inspection Requirements for PWR Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head and Tubesheet-to-Shell Welds. EPRI, Palo Alto, CA: 2019. 3002015906.

5-2.

Technical Bases for Inspection Requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Inside Radius Sections. EPRI, Palo Alto, CA:

2019. 3002014590.

5-3.

Letter from F. A. Kearney (Exelon) to U. S. NRC, Byron Station Unit 2 90-Day Inservice Inspection Report for Interval 3, Period 3, (B2R17), dated July 29, 2013, Docket No. 50-455, ADAMS Accession Number ML13217A093.

5-4.

Letter from J. M. Sorensen (NMC) to U. S. NRC, Unit 1 Inservice Inspection Summary Report, Interval 3, Period 3 Refueling Outage Dates 1-19-2001 to 2-25-2001 Cycle 20 /

05-26-99 to 02-25-2001, dated May 29, 2001, Docket Nos. 50-282 and 50-306, ADAMS Accession Number ML011550346.

5-5.

Letter from J. P. Solymossy (NMC) to U. S. NRC, Response to Opportunity For Comment On Task Interface Agreement (TIA) 2003-01, Application of ASME Code Section XI, IWB-2430 Requirements Associated With Scope of Volumetric Weld Expansion at the Prairie Island Nuclear Generating Plant (Tac Nos. MB7294 and MB7295), dated April 4, 2003, Docket Nos. 50-282 and 50-306, ADAMS Accession Number ML031040553.

5-6.

Technical Bases for Inspection requirements for Pressurizer Vessel Head, Shell-to-Head and Nozzle-to-Vessel Welds. EPRI, Palo Alto, CA: 2019. 3002015905.