ML23265A551

Enclosure 3: WCAP-18830-NP, Turkey Point Fuel Storage Criticality Analysis for 24 Month Cycles

ML23265A551
Person / Time
Site:	Turkey Point
Issue date:	09/22/2023
From:	Westinghouse
To:	Office of Nuclear Reactor Regulation
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ML23265A548	List: ML23265A549 ML23265A551
References
LTR-NRC-23-33
Download: ML23265A551 (204)

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Westinghouse Non-Proprietary Class 3 LTR-NRC-23-23 Enclosure 3 Enclosure 3 WCAP-18830-NP, Turkey Point Fuel Storage Criticality Analysis for 24 Month Cycles (Non-Proprietary)

September 2023 Westinghouse Electric Company 1000 Westinghouse Drive Cranberry Township, PA 16066

© 2023 Westinghouse Electric Company LLC All Rights Reserved

Westinghouse Non-Proprietary Class 3 WCAP-18830-NP September 2023 Revision 0 Turkey Point Fuel Storage Criticality Analysis for 24 Month Cycles

Westinghouse Non-Proprietary Class 3 WCAP-18830-NP Revision 0 Turkey Point Fuel Storage Criticality Analysis for 24 Month Cycles Michael T. Wenner*

Nuclear Design A & Spent Fuel Pool Criticality September 2023 Reviewers: Maxx Villotti*

Nuclear Design A & Spent Fuel Pool Criticality Andrew J. Sheaffer*

Nuclear Design B Approved: Zebulon E. Plotnick*, Manager Nuclear Design A & Spent Fuel Pool Criticality Information included in this material is proprietary and confidential and cannot be disclosed or used for any reason beyond the intended purpose without the prior written consent of Westinghouse Electric Company LLC.

This document is the property of and contains Proprietary Information owned by Westinghouse Electric Company LLC and/or its affiliates, subcontractors and/or suppliers. It is transmitted to you in confidence and trust, and you agree to treat this document in strict accordance with the terms and conditions of the agreement under which it was provided to you. Any unauthorized use of this document is prohibited.

• Electronically approved records are authenticated in the electronic document management system.

Westinghouse Electric Company LLC 1000 Westinghouse Drive Cranberry Township, PA 16066, USA

© 2023 Westinghouse Electric Company LLC All Rights Reserved

Westinghouse Non-Proprietary Class 3 ii RECORD OF REVISIONS Revision Description Completed 0 Original Issue See PRIME TRADEMARK NOTICE ZIRLO, Optimized ZIRLO, PRIMETM, AXIOM, and ADOPTTM are trademarks or registered trademarks of Westinghouse Electric Company LLC, its affiliates and/or its subsidiaries in the United States of America and may be registered in other countries throughout the world. All rights reserved.

Unauthorized use is strictly prohibited.

Metamic' is a trademark of Metamic, LLC. Other names may be trademarks of their respective owners.

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 iii TABLE OF CONTENTS LIST OF TABLES ........................................................................................................................................ v LIST OF FIGURES ..................................................................................................................................... ix LIST OF ACRONYMS, INITIALISMS, AND TRADEMARKS ................................................................ x 1 INTRODUCTION ........................................................................................................................ 1-1 2 BACKGROUND AND OVERVIEW ........................................................................................... 2-1 2.1 ACCEPTANCE CRITERIA ............................................................................................ 2-1 2.1.1 Spent Fuel Pool................................................................................................ 2-1 2.1.2 New Fuel Storage Rack ................................................................................... 2-2 2.2 DESIGN APPROACH ..................................................................................................... 2-2 2.3 COMPUTER CODES...................................................................................................... 2-3 2.3.1 Two-Dimensional Transport Code PARAGON ............................................... 2-3 2.3.2 Scale Code Package (Version 6.2.4) ................................................................ 2-5 2.3.3 Scale 252 Group Cross-Section Library .......................................................... 2-7 2.3.4 NEI-12-16, Revision 4 Checklist..................................................................... 2-7 3 DESIGN AND INPUT DATA ...................................................................................................... 3-1 3.1 REACTOR DESCRIPTION ............................................................................................ 3-1 3.2 FUEL ASSEMBLY DESCRIPTION ............................................................................... 3-2 3.3 ASSEMBLY REACTIVITY CONTROL DESCRIPTION ............................................. 3-3 3.4 FUEL STORAGE DESCRIPTION ................................................................................. 3-5 3.4.1 General Description ......................................................................................... 3-5 3.4.2 Storage Rack Specifications ............................................................................ 3-7 3.4.3 Storage Rack Insert Specifications .................................................................. 3-8 3.4.4 Fuel Rod Baskets ............................................................................................. 3-8 4 ANALYTICAL METHODOLOGY ............................................................................................. 4-1 4.1 DEPLETION ANALYSIS ............................................................................................... 4-1 4.1.1 Depletion Modeling Simplifications & Assumptions ...................................... 4-1 4.1.2 Fuel Depletion Parameter Selection ................................................................ 4-3 4.1.3 Design Basis Models ..................................................................................... 4-11 4.1.4 Final Depletion Parameters ........................................................................... 4-12 4.2 CRITICALITY ANALYSIS .......................................................................................... 4-18 4.2.1 Fuel Category, Storage Arrays and Other Storage ......................................... 4-19 4.2.2 Target keff Determination ............................................................................... 4-22 4.2.3 Keno Modeling Approach, Simplifications & Assumptions ......................... 4-22 4.2.4 Impact of Structural Materials on Reactivity................................................. 4-24 4.2.5 Bias & Uncertainty Description .................................................................... 4-24 4.2.6 Fresh IFBA Credit Analysis ........................................................................... 4-57 4.2.7 Burnup Limit Determination ......................................................................... 4-57 4.2.8 Interface Definitions ...................................................................................... 4-58 4.2.9 Soluble Boron Credit ..................................................................................... 4-60 5 RESULTS AND CONCLUSIONS ............................................................................................... 5-1 5.1 RESULTS APPLICABLE TO ALL CRITICALITY FUEL DESIGNS .......................... 5-1 5.2 STORAGE REQUIREMENTS ....................................................................................... 5-2 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 iv 5.2.1 Curve Fitting Coefficients for Minimum Burnup and IFBA Requirements ................................................................................................... 5-2 5.2.2 Criticality Fuel Design 1.................................................................................. 5-6 5.2.3 Criticality Fuel Design 2.................................................................................. 5-9 5.2.4 Criticality Fuel Design 3................................................................................ 5-13 5.3 FUEL ROD STORAGE BASKET ................................................................................ 5-17 5.4 ALLOWABLE INTERFACE CONFIGURATIONS ..................................................... 5-20 5.4.1 Within Region Interfaces ............................................................................... 5-20 5.4.2 Region I to Region II Interface ...................................................................... 5-20 5.4.3 Cask Area Rack Interfaces ............................................................................. 5-23 5.5 OTHER NORMAL STORAGE CONDITIONS ........................................................... 5-23 5.6 RODDED OPERATIONS ............................................................................................. 5-26 5.7 SOLUBLE BORON CREDIT ....................................................................................... 5-28 5.7.1 Soluble Boron Requirements for Normal Operation ..................................... 5-28 5.7.2 Soluble Boron for Accident Conditions......................................................... 5-29 5.7.3 Soluble Boron Requirements Summary ........................................................ 5-29 5.8 NEW FUEL STORAGE RACK .................................................................................... 5-30 5.8.1 Model Description ......................................................................................... 5-30 5.8.2 Rack Analysis ................................................................................................ 5-33 6 LIMITATIONS OF ANALYSIS ................................................................................................... 6-1 6.1 FUEL LIMITATIONS ...................................................................................................... 6-1 6.2 OPERATIONAL LIMITATIONS .................................................................................... 6-1 6.3 SPENT FUEL POOL STORAGE LIMITATIONS .......................................................... 6-1 7 REFERENCES ............................................................................................................................. 7-1 APPENDIX A VALIDATION OF SCALE 6.2.4 .................................................................................... A-1 APPENDIX B NEI-12-16, REVSION 4 CHECKLIST .......................................................................... B-1 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 v LIST OF TABLES Table 2-1 Isotopes Used in the Nuclear Criticality Safety Analysis ................................................ 2-4 Table 3-1 Reactor General Specifications ...................................................................................... 3-1 Table 3-2 Fuel Design Mechanical Specifications ........................................................................... 3-2 Table 3-3 Non-Mechanical Specifications and Operating History .................................................. 3-3 Table 3-4 RCCA Specifications ....................................................................................................... 3-4 Table 3-5 Pyrex and WABA Specifications ..................................................................................... 3-4 Table 3-6 IFBA Specifications ......................................................................................................... 3-4 Table 3-7 Fuel Rack Specifications ................................................................................................. 3-7 Table 3-8 Material Compositions ..................................................................................................... 3-8 Table 3-9 Metamic and Boral Insert Additional Specifications ....................................................... 3-8 Table 3-10 Fuel Rod Basket Specifications ....................................................................................... 3-9 Table 4-1 Pre-EPU Cycle Average Soluble Boron Concentration (ppm) ........................................ 4-5 Table 4-2 Post-EPU Cycle Average Soluble Boron Concentration (ppm), Blanketed Fuel ............. 4-6 Table 4-3 [ ]a,c .............................................. 4-9 Table 4-4 Criticality Fuel Design 1 Depletion Parameters ............................................................ 4-12 Table 4-5 Criticality Fuel Design 2 and 3 Depletion Parameters ................................................... 4-13 Table 4-6 Limiting Relative Burnup Profiles for Criticality Fuel Design 1................................... 4-14 Table 4-7 Limiting Relative Burnup Profiles for Criticality Fuel Design 2................................... 4-15 Table 4-8 Limiting Relative Burnup Profiles for Criticality Fuel Design 3................................... 4-16 Table 4-9 Limiting Moderator Temp. Profiles (°F) for Criticality Fuel Design 2.......................... 4-17 Table 4-10 Limiting Moderator Temp. Profiles (°F) for Criticality Fuel Design 3 .......................... 4-18 Table 4-11 Fuel Categories Ranked by Reactivity ........................................................................... 4-19 Table 4-12 Biases and Uncertainties for Configuration I-A ............................................................ 4-32 Table 4-13 Biases and Uncertainties for the Cask Area Rack .......................................................... 4-33 Table 4-14 Biases and Uncertainties for Configuration I-C (All I-2 Fuel) - Part 1 ......................... 4-34 Table 4-15 Biases and Uncertainties for Configuration I-C (All I-2 Fuel) - Part 2 ......................... 4-35 Table 4-16 CFD 1 Biases and Uncertainties for Array I-B .............................................................. 4-36 Table 4-17 CFD 1 Biases and Uncertainties for Array I-D .............................................................. 4-37 Table 4-18 CFD 1 Biases and Uncertainties for Array II-A ............................................................. 4-38 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 vi Table 4-19 CFD 1 Biases and Uncertainties for Array II-B* ........................................................... 4-39 Table 4-20 CFD 1 Biases and Uncertainties for Array II-C ............................................................. 4-40 Table 4-21 CFD 1 Biases and Uncertainties for Array II-D ............................................................. 4-41 Table 4-22 CFD 1 Biases and Uncertainties for Array II-E ............................................................. 4-42 Table 4-23 CFD 2 Biases and Uncertainties for Array I-B .............................................................. 4-43 Table 4-24 CFD 2 Biases and Uncertainties for Array I-D .............................................................. 4-44 Table 4-25 CFD 2 Biases and Uncertainties for Array II-A ............................................................. 4-45 Table 4-26 CFD 2 Biases and Uncertainties for Array II-B* ........................................................... 4-46 Table 4-27 CFD 2 Biases and Uncertainties for Array II-C ............................................................. 4-47 Table 4-28 CFD 2 Biases and Uncertainties for Array II-D ............................................................. 4-48 Table 4-29 CFD 2 Biases and Uncertainties for Array II-E ............................................................. 4-49 Table 4-30 CFD 3 Biases and Uncertainties for Array I-B .............................................................. 4-50 Table 4-31 CFD 3 Biases and Uncertainties for Array I-D .............................................................. 4-51 Table 4-32 CFD 3 Biases and Uncertainties for Array II-A ............................................................. 4-52 Table 4-33 CFD 3 Biases and Uncertainties for Array II-B* ........................................................... 4-53 Table 4-34 CFD 3 Biases and Uncertainties for Array II-C ............................................................. 4-54 Table 4-35 CFD 3 Biases and Uncertainties for Array II-D ............................................................. 4-55 Table 4-36 CFD 3 Biases and Uncertainties for Array II-E ............................................................. 4-56 Table 5-1 IFBA Requirements for Fuel Category I-2 ...................................................................... 5-1 Table 5-2 CFD 1 - Coefficients to Calculate the Minimum Required Fuel Assembly Burnup (Bu) as a Function of Enrichment (En) and Cooling Time (Ct) ................................................... 5-3 Table 5-3 CFD 2 - Coefficients to Calculate the Minimum Required Fuel Assembly Burnup (Bu) as a Function of Enrichment (En) and Cooling Time (Ct) ................................................... 5-4 Table 5-4 CFD 3 - Coefficients to Calculate the Minimum Required Fuel Assembly Burnup (Bu) as a Function of Enrichment (En) and Cooling Time (Ct) ................................................... 5-5 Table 5-5 CFD 1 Fuel Category I-3 Burnup Requirements (GWd/MTU) ....................................... 5-6 Table 5-6 CFD 1 Fuel Category I-4 Burnup Requirements (GWd/MTU) ....................................... 5-6 Table 5-7 CFD 1 Fuel Category II-1 Burnup Requirements (GWd/MTU)...................................... 5-7 Table 5-8 CFD 1 Fuel Category II-2 Burnup Requirements (GWd/MTU)...................................... 5-7 Table 5-9 CFD 1 Fuel Category II-3 Burnup Requirements (GWd/MTU)...................................... 5-7 Table 5-10 CFD 1 Fuel Category II-4 Burnup Requirements (GWd/MTU)...................................... 5-8 Table 5-11 CFD 1 Fuel Category II-5 Burnup Requirements (GWd/MTU)...................................... 5-8 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 vii Table 5-12 CFD 1 Fuel Category II-6 Burnup Requirements (GWd/MTU)...................................... 5-8 Table 5-13 CFD 2 Fuel Category I-3 Burnup Requirements (GWd/MTU) ....................................... 5-9 Table 5-14 CFD 2 Fuel Category I-4 Burnup Requirements (GWd/MTU) ....................................... 5-9 Table 5-15 CFD 2 Fuel Category II-1 Burnup Requirements (GWd/MTU).................................... 5-10 Table 5-16 CFD 2 Fuel Category II-2 Burnup Requirements (GWd/MTU).................................... 5-10 Table 5-17 CFD 2 Fuel Category II-3 Burnup Requirements (GWd/MTU).................................... 5-11 Table 5-18 CFD 2 Fuel Category II-4 Burnup Requirements (GWd/MTU).................................... 5-11 Table 5-19 CFD 2 Fuel Category II-5 Burnup Requirements (GWd/MTU).................................... 5-12 Table 5-20 CFD 2 Fuel Category II-6 Burnup Requirements (GWd/MTU).................................... 5-12 Table 5-21 CFD 3 Fuel Category I-3 Burnup Requirements (GWd/MTU) ..................................... 5-13 Table 5-22 CFD 3 Fuel Category I-4 Burnup Requirements (GWd/MTU) ..................................... 5-13 Table 5-23 CFD 3 Fuel Category II-1 Burnup Requirements (GWd/MTU).................................... 5-14 Table 5-24 CFD 3 Fuel Category II-2 Burnup Requirements (GWd/MTU).................................... 5-14 Table 5-25 CFD 3 Fuel Category II-3 Burnup Requirements (GWd/MTU).................................... 5-15 Table 5-26 CFD 3 Fuel Category II-4 Burnup Requirements (GWd/MTU).................................... 5-15 Table 5-27 CFD 3 Fuel Category II-5 Burnup Requirements (GWd/MTU).................................... 5-16 Table 5-28 CFD 3 Fuel Category II-6 Burnup Requirements (GWd/MTU).................................... 5-16 Table 5-29 keff With and Without the Fuel Rod Basket in Region I Storage Configurations (Assessments Performed With Criticality Fuel Design 3) ............................................. 5-18 Table 5-30 keff With and Without the Fuel Rod Basket in Region II Storage Configurations ......... 5-19 Table 5-31 Results for the Region I - Region II Interface Calculations1 ......................................... 5-23 Table 5-32 Results for the Normal Operations with 500 ppm of Soluble Boron ............................. 5-28 Table 5-33 [ ]a,c .......................................................................... 5-29 Table 5-34 [ ]a,c ............................................................. 5-29 Table 5-35 Results for the New Fuel Storage Racks........................................................................ 5-33 Benchmark Values of keff and Respective Uncertainties ............................................... A-23

[ ]a,c ........................ A-25

[

]a,c .................................................................................................... A-29

[

]a,c .................................................................................................................. A-33 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 WCAP-18830-NP

Westinghouse Non-Proprietary Class 3 ix LIST OF FIGURES Figure 3-1 Turkey Point Spent Fuel Pool Layout (Unit 4 is the Same Except a Mirror Image) ............... 3-5 Figure 3-2 Top View of the Turkey Point New Fuel Storage Racks ......................................................... 3-6 Figure 3-3 Side View of the Turkey Point New Fuel Storage Racks ........................................................ 3-6 Figure 3-4 Planar View of Array II-A with One Fuel Rod Storage Basket Model ................................... 3-9 Figure 4-1 Allowable Region I Storage Arrays ....................................................................................... 4-20 Figure 4-2 Allowable Region II Storage Arrays ..................................................................................... 4-21 Figure 4-3 Example of Interfaces between Region II Configurations .................................................... 4-59 Figure 4-4 Region I and Region II Interface Model Example ................................................................ 4-60 Figure 5-1 Allowable Array I-A Region II Interfaces ............................................................................. 5-20 Figure 5-2 Allowable Array I-B- Region II Interfaces ............................................................................ 5-21 Figure 5-3 Allowable Array I-D Region II Interfaces ............................................................................. 5-21 Figure 5-4 New Fuel Storage Rack Model (planar view) ....................................................................... 5-31 Figure 5-5 New Fuel Storage Rack Model (axial view, concrete thickness not to scale)) ...................... 5-32 Figure 5-6 keff as a Function of Water Density for 4.25 wt.% 235U Fuel ................................................. 5-34 Figure 5-7 keff as a Function of Water Density for 5 wt.% 235U Fuel with 16 IFBA Rods ...................... 5-34 Figure A-1 [ ]a,c ........................................... A-49 Figure A-2 [ ]a,c ........................... A-50 Figure A-3 [ ]a,c....................................... A-50 Figure A-4 [ ]a,c ............................... A-53 Figure A-5 [ ]a,c....... A-58 Figure A-6 [

]a,c ....................................................................................................................... A-59 Figure A-7 [ ]a,c . A-59 Figure A-8 [ ]a,c ................... A-62 Figure A-9 [

]a,c ............................................................................................................................ A-63 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 x LIST OF ACRONYMS, INITIALISMS, AND TRADEMARKS 1D One-Dimensional 2D Two-Dimensional 3D Three-Dimensional AEG Average Energy Group at.% Atom Percent BA Burnable Absorber CFD Criticality Fuel Design (used in table titles only)

EALF Energy of Average Lethargy Causing Fission EPU Extended Power Uprate FRSB Fuel Rod Storage Basket GT Guide Tube (or Thimble)

GWd GigaWatt Day HVFD Hafnium Vessel Flux Depression IFBA Integral Fuel Burnable Absorber IT Instrumentation Tube (or Thimble)

LAR License Amendment Request MWd MegaWatt Day MWt MegaWatts Thermal MTU Metric Tons Uranium N/A Not Applicable NFR New Fuel Storage Rack OFA Optimized Fuel Assembly (Westinghouse Fuel Type)

PWR Pressurized Water Reactor RCCA Rod Cluster Control Assemblies SFP Spent Fuel Pool STD Standard (Westinghouse Fuel Type)

TD Percent of Theoretical Density WABA Wet Annular Burnable Absorber wt.% Weight Percent WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 1-1 1 INTRODUCTION The purpose of this report is to document a criticality analysis performed to support fuel management changes supporting 24 month operation at Turkey Point Units 3 and 4 which necessitate an update (to replace) the current analysis of record. The fuel management changes impact the fuel due to changes in fuel features such as PRIME fuel features, AXIOM cladding, and ADOPT fuel pellets, related operational characteristics such as axial burnup shape, as well as the overall neutron poison loaded during operation including soluble boron and using gadolinia as a burnable absorber.

This report documents the criticality safety evaluation for the storage of PWR nuclear fuel assemblies in the NFR and the SFP. The SFP consists of permanent Region I and Region II racks and a removable Cask Area Rack. The NFR and SFP analyses are updated to support fuel with a higher TD (via ADOPT).

The main report includes the overall analysis background, design and input data, methodology, and analysis results and conclusions including the depletion and criticality analysis. Appendix A contains the details of the validation of the SCALE code (Version 6.2.4, Reference 1) utilized for the criticality analysis. Appendix B provides the NEI-12-16, Revision 4 filled out checklist.

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Westinghouse Non-Proprietary Class 3 2-1 2 BACKGROUND AND OVERVIEW Updated storage requirements at Turkey Point are necessitated by fuel management changes. These changes include moving to a fully enriched blanket design (post-EPU) which includes the operational characteristics of fuel through a transition to this design. As a result of this change, fuel storage is split into three Criticality Fuel Designs (whereas it was split into two Criticality Fuel Designs in the Reference 2 analysis, Non-Blanketed and Blanketed). These three Criticality Fuel Designs are Pre-EPU (unblanketed), Pre/Post-EPU with mid enriched blankets, and Post-EPU unblanketed (fully enriched) fuel. Depletion input is separated for each of the Criticality Fuel Designs.

Existing storage patterns, with the exception of an additional storage pattern described herein, are re-evaluated for storage. Consistent with Reference 2, this analysis credits neutron absorber inserts placed into the Region II racks to partially offset an assumed full loss of the original Boraflex neutron absorber.

Credit is taken for the negative reactivity associated with burnup and post-irradiation cooling time.

Additionally, credit is taken for the presence of soluble boron in the spent fuel pool and for the presence of full-length RCCAs placed in selected fuel assemblies (including in Region I). The presence of IFBA rods is also credited for certain fresh fuel storage categories.

To clearly distinguish between the inserts placed into rack cells and the control components inserted into fuel assemblies, the term insert by itself always refers to the Metamic' neutron absorber inserts placed into the Region II racks. The full-length control components are always referred to as RCCAs. Other burnable absorbers placed into assemblies during depletion are always clearly characterized, e.g., as Pyrex inserts, WABA inserts, or hafnium inserts.

The relevant fuel assembly and fuel rack specifications are identical between Turkey Point Unit 3 and Unit 4. When assembly or history specific data is used, both units are considered in the compilation of that data. Therefore, all analyses and conclusions presented in this report apply to both units.

2.1 ACCEPTANCE CRITERIA The goal of this analysis is to provide storage at Turkey Point Unit 3 and Unit 4 which conforms to Reference 3. As a result, this SFP criticality safety analysis ensures that the SFPs operate within the bounds discussed here.

2.1.1 Spent Fuel Pool

1. The effective neutron multiplication factor (keff) of all permissible storage arrangements at a soluble boron concentration of 0 parts per million (ppm) shall be less than 1.0 including all applicable biases and uncertainties with 95 percent probability at a 95 percent confidence level.

2. The keff of all permissible storage arrangements when crediting soluble boron shall yield results not exceeding 0.95, including all applicable biases and uncertainties with 95 percent probability at a 95 percent confidence level.

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Westinghouse Non-Proprietary Class 3 2-2

3. The keff when crediting soluble boron shall not exceed 0.95 under all postulated accident conditions, including a margin for all applicable biases and uncertainties with 95 percent probability at a 95 percent confidence level.

2.1.2 New Fuel Storage Rack

1. The effective neutron multiplication factor (keff) of the fresh fuel in the fresh fuel storage racks shall not exceed 0.95, at a 95% probability, 95% confidence level, assuming the racks are loaded with fuel of the maximum fuel assembly reactivity and flooded with full density unborated water.

2. The New Fuel Storage Rack shall not exceed a keff of 0.98, at a 95% probability, 95% confidence level, when under optimum moderation conditions. In the optimum moderation evaluation, the rack is assumed to be loaded with fuel of the maximum fuel assembly reactivity and filled with low-density hydrogenous fluid.

The maximum keff must account for all appropriate biases and uncertainties.

2.2 DESIGN APPROACH As discussed in Section 2, in order to qualify the existing racks for appropriate placement of fuel under Pre-EPU and Post-EPU conditions, fuel assemblies are separated into three Criticality Fuel Designs.

Within each Criticality Fuel Design, fuel is stored in approved storage patterns, with individual assembly descriptions given by fuel Category. Each fuel Category has a set of minimum burnup requirements which are a function of the Criticality Fuel Design, storage configuration, initial enrichment 1 and post irradiation cooling time. In addition, a fuel category is included which credits the inclusion of IFBA absorber rods for fresh fuel.

The fuel categories are ranked by reactivity within the appropriate storage region of the SFP in Table 4-11. The relative placement of assemblies from the fuel categories as well as the number and location of reactivity suppressing devices necessary to meet the acceptance criteria are determined.

Acceptable combinations of fuel categories and reactivity suppressing devices are termed storage configurations or storage arrays in this document. Storage configurations allowed by this analysis are presented in Figure 4-1 and Figure 4-2 for Regions I and II of the SFP, respectively. It is important to note that each 2x2 array is analyzed with fuel of the maximum allowable reactivity for the category.

Therefore, fuel of a lower reactivity (i.e., greater burnup) may also be placed in the array. It is not necessary to use all defined arrays in the arrangement of assemblies in the spent fuel pool.

Three storage rack designs are available in the Turkey Point SFPs. Region I, a flux trap style rack design, Region II, a constructed/developed cell design, and the Cask Area Rack, a removable flux trap style rack.

The Region II rack design is not symmetric due to the geometry of the constructed vs. developed cells within the rack. As a result, for any storage configuration in Region II, sensitivity calculations are performed to ensure the bounding assembly placement is applied for storage locations where the 1

Initial enrichment is the enrichment of the central zone region of fuel, excluding axial cutbacks\blankets and prior to reduction in 235U content due to fuel depletion.

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Westinghouse Non-Proprietary Class 3 2-3 constructed or developed cells create slightly different configuration geometry. Furthermore, this report documents enrichment and burnable absorber (IFBA) requirements for the NFR.

2.3 COMPUTER CODES The analysis methodology employs the following computer codes and cross-section libraries: (1) the two dimensional (2-D) transport lattice code PARAGON Version 1.4.3, as documented in WCAP-16045-P-A, Qualification of the Two-Dimensional Transport Code PARAGON (Reference 4) and its cross-section library based on Evaluated Nuclear Data File Version VI.3 (ENDF/B-VI.3), and (2) Scale Version 6.2.4, (Reference 1), with the ENDF/B-VII.1 252 group cross-section library.

2.3.1 Two-Dimensional Transport Code PARAGON PARAGON is used in this application to simulate in-reactor fuel assembly depletion to generate isotopics for burnup credit. PARAGON is the Westinghouse Electric Company LLC state-of-the-art 2D lattice transport code for PWR applications. It is part of the Westinghouse core design package and provides lattice cell data for 3D core simulator codes.

This data includes macroscopic cross-sections, microscopic cross-sections for feedback adjustments, pin factors for pin power reconstruction calculations, and discontinuity factors for a 3D nodal method solution of the diffusion equation. PARAGON uses the collision probability theory within the interface current method to solve the integral transport equation. Throughout the calculation, PARAGON uses the exact heterogeneous geometry of the assembly and the same energy groups as in the cross-section library to compute the multi-group fluxes for each micro-region location of the assembly. In order to generate the multi-group data, PARAGON goes through four steps of calculations: resonance self-shielding, flux solution, burnup calculation, and homogenization. The 70-group PARAGON cross-section library is based on the ENDF/B-VI.3 basic nuclear data. It includes explicit multigroup cross-sections and other nuclear data without any lumped fission products or pseudo cross-sections. PARAGON and its 70-group cross-section library are benchmarked, qualified, and licensed both as a standalone transport code and as a nuclear data source for a core simulator in a complete nuclear design code system for core design, safety, and operational calculations. The list of fuel isotopes modeled in PARAGON and subsequently modeled in the criticality analysis is given in Table 2-1.

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Westinghouse Non-Proprietary Class 3 2-4 Table 2-1 Isotopes Used in the Nuclear Criticality Safety Analysis a,c Additional qualification of PARAGON for use in spent fuel pool applications has been performed at Westinghouse. The Electric Power Research Institute (EPRI) has developed PWR reactivity depletion benchmarks using a large set of measured flux data (flux maps) in Reference 5.

A guide for application of the EPRI depletion benchmarks for use in burnup credit calculations is given by way of example in Reference 6, with this methodology repeated by Westinghouse in EPRI Depletion Benchmark Calculations Using PARAGON (Reference 7). Results of this analysis provide additional confidence in the usage of PARAGON for SFP reactivity calculations and provide a sound basis for usage of the 5% decrement approach for depletion uncertainty showing that the depletion isotopics generated with PARAGON, and input into CSAS5 input models in Scale is conservative for determining depletion uncertainty. This is now supported by guidance in Reference 9 via endorsement of Reference 8 with limitations and conditions.

PARAGON is generically approved for depletion calculations (Reference 4). PARAGON has been chosen for this spent fuel criticality analysis because it has all the attributes needed for burnup credit applications.

There are no Safety Evaluation Report limitations for the use of PARAGON in UO2 criticality analysis.

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Westinghouse Non-Proprietary Class 3 2-5 2.3.2 Scale Code Package (Version 6.2.4)

The Scale system was developed for the U.S. Nuclear Regulatory Commission (NRC) to standardize the method of analysis for evaluation of nuclear fuel facilities and shipping package designs (Reference 1). In this SFP criticality analysis, the Scale code package is used to calculate the reactivity of fissile systems in SFP conditions. Specifically, the Scale package is used to analyze infinite arrays for all storage arrays in the SFPs, finite rack modules and SFP representations to evaluate interfaces, soluble boron requirements, and postulated accident scenarios to demonstrate that the requirements in Section 2.1 are met.

The Scale package includes the control module Criticality Safety Analysis Sequence with KENO V.a (CSAS5), which provides reliable and efficient means of performing keff calculations for systems that are routinely encountered in engineering practice, especially in the calculation of keff of 3D system models.

Updated structurally from prior versions, CSAS5 implements the modern material and cross section processing module XSProc to process material input and provide a temperature resonance-corrected cross section library based on the physical characteristics of the problem being analyzed. XSProc calls several lower level functional modules, some of which perform simple functions that were not called out as separate from CSAS5 in past versions.

XSProc was developed for the Scale 6.2 release to prepare data for continuous-energy and multigroup calculations. XSProc expands material input from Standard Composition Library definitions into atom number densities (calling the integrated MixMacros module) and, for multigroup calculations, performs cross section resonance self-shielding, energy group collapse, and spatial homogenization. XSProc implements capabilities for problem-dependent temperature interpolation, calculation of Dancoff factors (calling the integrated Dancoff module), resonance self-shielding using Bondarenko factors with full-range intermediate resonance treatment, as well as use of continuous energy resonance self-shielding in the resolved resonance region. XSProc integrates and enhances the capabilities previously implemented independently in BONAMI, CENTRM, PMC, WORKER, ICE, and XSDRNPM, along with some additional capabilities that were provided by MIPLIB and SCALELIB in prior Scale release. For this work XSProc utilizes the following modules in addition to MixMacros and Dancoff (CENTRM and PMC are called via the CentrmPmc module):

• BONAMI: The BONAMI module is used to perform Bondarenko calculations for resonance self-shielding. BONAMI obtains problem-independent cross sections and Bondarenko shielding factors from a multigroup (MG) AMPX master library, and it creates a MG AMPX working library of self-shielded, problem-dependent cross sections. Several options may be used to compute the background cross section values using the narrow resonance or intermediate resonance approximations, with and without Bondarenko iterations. A novel interpolation scheme is used that avoids many of the problems exhibited by other interpolation methods for the Bondarenko factors. BONAMI is most commonly used in automated SCALE sequences and is fully integrated within the Scale cross section processing module, XSProc. During the execution of a typical Scale computational sequence using XSProc, Dancoff factors for uniform lattices of square- or triangular-pitched units are calculated automatically for BONAMI by numerical integration over the chord length distribution. Heterogeneous effects are treated using equivalence theory based on an escape cross section for arrays of slabs, cylinders, or spheres.

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Westinghouse Non-Proprietary Class 3 2-6

• CENTRM: CENTRM computes continuous-energy neutron spectra for infinite media, 1D) systems, 2D unit cells in a lattice, by solving the Boltzmann transport equation using a combination of pointwise and multigroup nuclear data. CENTRM is primarily used to calculate problem-specific fluxes on a fine energy mesh to generate self-shielded multigroup cross sections for subsequent radiation transport computations. Several calculation options are available, including a slowing-down computation for homogeneous infinite media, 1D discrete ordinates in slab, spherical, or cylindrical geometries; a simplified two-region solution; and 2D method of characteristics for a unit cell within a square-pitch lattice.

• PMC: PMC generates problem-dependent multigroup cross-sections from an existing AMPX multigroup cross-section library, a point wise nuclear data library, and a pointwise neutron flux file produced by the CENTRM continuous-energy transport code. In the Scale sequences, PMC is used primarily to produce self-shielded multigroup cross-sections over a specified energy range such as the resolved resonance energy range of individual nuclides in the system of interest. The self-shielded cross-sections are obtained by integrating the point wise nuclear data using the CENTRM problem-specific, continuous-energy flux as a weight function for each spatial zone in the system.

• KENO: The KENO module is a Monte Carlo criticality program used to calculate the keff of 3-D models using continuous energy or multigroup cross-sections and is called by CSAS5 once XSProc is complete. Flexible geometry features and the availability of various boundary condition prescriptions in KENO allow for accurate and detailed modeling of fuel assemblies in storage racks, either as infinite arrays or in actual SFP models. The version used in this work, KENO V.a, contains a simplified geometry package appropriate for use herein. Anisotropic scattering is treated by using discrete scattering angles using Pn Legendre polynomials. KENO uses problem-specific cross-section libraries, processed for resonance self-shielding and for the thermal characteristics of the problem.

For this work, the option parm=centrm is used as input, for which the CENTRM/PMC modules are executed to process shielded multi-group cross sections using continuous energy flux spectra calculated with the recommended type of continuous energy transport solver for the designated type of cell. An infinite homogeneous medium calculation is used for those materials not called out for special processing, using 2D Method of Characteristics for a LATTICECELL consisting of cylindrical fuel rods in a square lattice, and using 1-D discrete Sn transport for all other LATTICECELLs and MULTIREGION cells.

The criticality sequence of Scale 6.2.4 is validated using fresh UO2 critical experiments and Haut Taux de Combustion (HTC) critical experiments to form an experiment benchmark suite applicable to fresh and spent fuel criticality calculations. See Reference 10 for an overview of the HTC criticals. Additional details of the validation are found in APPENDIX A. The validation shows that Scale 6.2.4 is an accurate tool for calculation of keff for SFP applications. The benchmark calculations use the same computer platform and cross-section libraries that are used for the design basis calculations. The validation considers both fresh UO2 and fuel with plutonium designed to have an actinide composition similar to burned fuel.

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Westinghouse Non-Proprietary Class 3 2-7 2.3.3 Scale 252 Group Cross-Section Library The 252-group ENDF/B-VII.1 library included in the Scale package is available for general purpose criticality analyses and is used for this work. The validation of the ENDF/B-VII.1 252-group library with the Scale Version 6.2.4 CSAS5 module is documented in APPENDIX A.

2.3.4 NEI-12-16, Revision 4 Checklist A filled out NEI-12-16, Revision 4 checklist is given in APPENDIX B.

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Westinghouse Non-Proprietary Class 3 3-1 3 DESIGN AND INPUT DATA This section describes the physical characteristics of Turkey Point Units 3 & 4 that are important to SFP criticality safety. Pertinent reactor characteristics and associated fuel design and fuel management history are discussed in Section 3.1. The physical characteristics of the SFPs are discussed in Section 3.4.

3.1 REACTOR DESCRIPTION Section 3.1 provides data on the design and operation of Turkey Point Units 3 & 4 as well as the fuel designs and fuel management of the plant. Table 3-1 provides basic data on the type of reactor and the fuel types that comprise Turkey Point Units 3 & 4.

Turkey Point Units 3 & 4 are Westinghouse PWRs utilizing fuel with a 15 x 15 lattice. Both the Westinghouse Standard (STD) and Optimized Fuel Assembly (OFA) Westinghouse fuel designs have been employed. All fuel assemblies used at Turkey Point Units 3 & 4 incorporate a 15 x 15 square array of 204 fuel rods with 20 guide tubes (GT) and 1 instrument tube (IT).

Various OFA fuel types are differentiated by the grids and composition of structural materials. All zirconium based assembly materials are modeled as Optimized ZIRLO material in criticality models.

Westinghouse has shown the impact of differing Zirconium based structural materials is of no practical significance. Each fuel rod contains a column of enriched UO2 fuel pellets. The pellets are pressed and sintered and are dished on both ends.

Table 3-1 Reactor General Specifications 1 Reactor type Westinghouse Historic & current reactor power (MWt) 2300-2644 Fuel lattice 15 x 15 Fuel Type 1 Westinghouse Standard Fuel Assembly (STD)

Fuel Type 2 Westinghouse Optimized Fuel Assembly (OFA) 1 This analysis intends to cover the main fuel types, namely STD and OFA for 15x15 fuel. Variations of these main fuel types have been and are in use which include changes to grid and structural materials, such DRFA, LOPAR and Upgrade (current OFA variation) fuel.

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Westinghouse Non-Proprietary Class 3 3-2 3.2 FUEL ASSEMBLY DESCRIPTION The neutronically important mechanical features of the two fuel designs are listed in Table 3-2.

Table 3-2 Fuel Design Mechanical Specifications Assembly type STD OFA Tolerance 2 Rod array size 15 x 15 15 x 15 Rod pitch, in 0.563 0.563 [ ]a,c Active fuel length, in 144 144 Total number of fuel rods 204 204 Fuel cladding outer dimension (OD), in 0.4220 0.4220 +/-[ ]a,c Fuel cladding inner dimension (ID), in 0.3734 0.3734 +/-[ ]a,c Fuel cladding thickness, in 0.0243 0.0243 +/-[ ]a,c Pellet diameter, in 0.3659 0.3659 +/-[ ]a,c Number of GT/IT 20/1 20/1 GT/IT OD, in 0.546 0.533 +/-[ ]a,c GT/IT ID, in 0.512 0.499 +/-[ ]a,c Percent theoretical density, nominal 3 95.0 - 96.5 95.0 - 96.5 See Table 3-3 Non-mechanical fuel features which are important to criticality safety and how they impact the number of distinct fuel designs are considered in this analysis. Operational characteristics of every cycle operated at Turkey Point Units 3 & 4 were reviewed. All cycles can be categorized conservatively into one of the following Criticality Fuel Designs. Table 3-3 outlines the key non-mechanical features and fuel management history of each of the fuel designs.

2 Tolerances are the same for both designs.

3 Historical values, bounding values are modeled as seen in Table 3-3.

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Westinghouse Non-Proprietary Class 3 3-3 Table 3-3 Non-Mechanical Specifications and Operating History Criticality Fuel Design 1 2 3 Assembly type STD/OFA STD/OFA STD/OFA Max. TD 97.5 98.3 98.3 Max. operating power, MWt 2300 2644 2644 Axial blanket enrichment No Blanket 2.6 wt.% Fully Enriched Axial blanket length, in N/A 8 N/A Burnable absorber (BA) Type Pyrex/WABA IFBA/WABA IFBA/Gad BA material B2O3-SiO2 ZrB2 ZrB2 BA max. loading 12.5 wt.% 1.25X 1.25X Max BA length, in 144 128 128 Maximum number of rods / fingers 12 148 148 Note:

1. The Max. TD for Criticality Fuel Designs are chosen for conservatism and to bound potential future operation (in the case of Criticality Fuel Designs 2 and 3).

2. Criticality Fuel Design 2 Pre-EPU fuel contains WABA in some cycles. See Section 4.1.2.2.6 for additional details.

3. Gadolium absorber is acceptable for use in CFD 2 and 3. See Section 4.1.2.2.6 for additional details.

Burnup limits are generated for each listed Criticality Fuel Design. For each, design basis input is separately determined (for depletion analysis) as given in Section 4.1.4 3.3 ASSEMBLY REACTIVITY CONTROL DESCRIPTION Table 3-4 shows specifications and tolerances for the full length RCCA used in the analysis. In this report RCCA always refers to full length RCCAs. Part length control elements are not credited in this report.

Note also that while RCCAs are listed as burnable absorbers, RCCAs are not present in assembly during any depletion analyses.

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Westinghouse Non-Proprietary Class 3 3-4 Table 3-4 RCCA Specifications Parameter Value Material Silver-Indium-Cadmium Silver content, wt.% 80 +/-[ ]a,c Indium content, wt.% 15 +/-[ ]a,c Cadmium content, wt.% 5 +/-[ ]a,c Poison OD, inch 0.3900 +/-[ ]a,c Poison length in active fuel region, inch 141.75 Clad inner diameter, inch 0.4005 +/-[ ]a,c Clad outer diameter, inch 0.4390 +/-[ ]a,c Clad material SS Poison density, gm/cm3 10.17 Table 3-5 provides the specifications for the Pyrex and Wet Annular Burnable Absorber (WABA). Pyrex burnable absorbers are only modeled in the Criticality Fuel Design 1 depletion analysis. See Section 4.1.2.2.6 for additional details regarding WABA usage. Table 3-6 Contains the IFBA specifications.

Table 3-5 Pyrex and WABA Specifications Parameter Pyrex WABA Burnable absorber (BA) material Borosilicate Glass B4 C BA inner diameter, inch 0.2440 0.2780 BA outer diameter, inch 0.3890 0.3180 BA clad material, inch SS Zr BA inner clad thickness, inch 0.0065 0.0210 BA inner clad OD, inch 0.2360 0.2670 BA outer clad thickness, inch 0.0188 0.0260 BA outer clad OD, inch 0.4310 0.3810 BA length, inch 144 120 Table 3-6 IFBA Specifications Parameter Value BA Material ZrB2 10 B abundance / loading (mg/in) [ ]a,c IFBA Thickness (in) [ ]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 3-5 Reference 2 discusses the HVFD absorbers that have been used to reduce the fluence at critical weld locations along the core vessel for the purpose of vessel life extension. Hafnium is used as the absorbing material because of its high neutron absorption and slow depletion characteristics. The hafnium insert is a hafnium rod encased in zircaloy cladding. The hafnium region of the inserts is part-length with the remaining rod length being structural material. The hafnium inserts are designed to be placed in the guide tubes of an assembly similar to discrete burnable absorbers. Hafnium inserts are not modeled in the analysis herein but will be addressed as was done in Reference 2 in Section 4.1.2.2.6.

3.4 FUEL STORAGE DESCRIPTION 3.4.1 General Description Each SFP at Turkey Point is identical from the criticality design perspective. Figure 3-1 shows the rack layout in the pools. The 11x12 NEW REGION 1 rack is called the Cask Area Rack in this analysis. The minimum separation between rack modules is 1.15 inches. Storage is delineated by Region I, II and the Cask Area Rack. Region I racks are the 10X11, and 8X11 storage racks.

Figure 3-1 Turkey Point Spent Fuel Pool Layout (Unit 4 is the Same Except a Mirror Image)

Figure 3-2 and Figure 3-3 show the top and side views of the New Fuel Storage Rack. As can be seen from the top view, the rack is L-shaped with a 10 x 3 array against an 8 x 3 array making for storage of 54 assemblies. The side view is shortened. The side view shows two column-like items, which are funnel type devices used to assure the fuel assemblies are correctly placed in the rack. Between the bottom WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 3-6 funnel and top funnel, the rack is open. The funnels are 2 feet 9 inches long. Section 3.4.2 summarizes applicable dimensions considered in the fuel racks.

Figure 3-2 Top View of the Turkey Point New Fuel Storage Racks Figure 3-3 Side View of the Turkey Point New Fuel Storage Racks WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 3-7 3.4.2 Storage Rack Specifications The storage cell characteristics that are used in the criticality analysis are summarized in Table 3-7 for the Region I, Region II, Cask Area Rack, and New Fuel Storage Racks. Note that the poison areal density listed for Regions I and II is not used in the analysis since it is assumed that the Boraflex has completely degraded. The Boraflex material is replaced with water. There is no credible mechanism that would allow the 10B to escape without the whole material dissolving so replacing the Boraflex with water is appropriate (i.e., if there is any Boraflex material remaining, it would also contain the neutron absorbing 10 B).

Table 3-7 Fuel Rack Specifications Value New Fuel Parameter Region I Region II Cask Area 4 Rack 8.75 8.80 8.75 9.00 Cell ID, inch

[ ]a,c [ ]a,c [ ]a,c [ ]a,c 0.075 0.075 0.075 Wall thickness, inch -

[ ]a,c [ ]a,c [ ]a,c 10.60 9.00 21.0 Cell pitch, inch a,c a,c See Section 4.2.3

[ ] [ ] [ ]a,c Poison cavity thickness, 0.090 0.064 0.083 inch [ ]a,c [ ]a,c [ ]a,c 0.078 0.051 0.075 Poison thickness, inch -

[ ]a,c [ ]a,c [ ]a,c Sheathing thickness, 0.02 0.02 0.0235 inch [ ]a,c [ ]a,c [ ]a,c 7.50 7.50 Sheathing width, inch a,c See Section 4.2.3 -

[ ] [ ]a,c Poison areal density, 0.020 0.012 10 [ ]a,c -

B gm/cm2 (modeled as 0) (modeled as 0)

Table 3-8 describes the material composition of all structural and absorber materials used.

4 See Section 4.2.3 for details regarding Cask Area Rack Modeling.

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Westinghouse Non-Proprietary Class 3 3-8 Table 3-8 Material Compositions Component Density (gm/cm ) 3 Material wt.%

Rack 7.940 SS304 100.0 Sheathing 7.940 SS304 100.0 B4 C 21.101 Metamic 2.657 Al 78.899 Boral B4 C 28.023 2.653 (in cask area) Al 71.977 3.4.3 Storage Rack Insert Specifications Both Boraflex and Metamic absorber inserts are utilized at Turkey Point Units 3 & 4 in Region I and II.

Due to the known degradation of Boraflex, no credit for this absorber insert is taken and its presence is replaced by moderator. The physical characteristics for the Metamic and Boral (Cask Area Rack) neutron absorber inserts are summarized in Table 3-9.

Table 3-9 Metamic and Boral Insert Additional Specifications Parameter Metamic Boral Material Al-B4C Al-B4C 10 B loading, g/cm2 0.016 [ ]a,c [ ] a,c Thickness, inch 0.073 [ ]a,c 0.075 [ ] a,c Width, inch 8.35 [ ]a,c 7.50 Length (in active fuel region), inch [ ]a,c 144 Note that the insert length used in the analysis is shorter than the active fuel length, i.e., it is assumed that the lower 6 inches of the active fuel length are not covered by the insert. The Metamic inserts are modeled as having the minimum length and minimum width allowed by the tolerances, and the nominal thickness.

The uncertainty in thickness is considered in the analysis. See Section 4.2.3 assumptions for additional details about the Metamic insert modeling.

3.4.4 Fuel Rod Baskets Fuel rod baskets are used to store loose fuel rods as needed. The baskets consist of regular arrays of stainless steel tubes. Individual fuel rods are placed in these tubes. The specifications of the fuel rod baskets are given in Table 3-10. A planar view of a Region II KENO model with one storage basket in a Region II configuration is shown in Figure 3-4.

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Westinghouse Non-Proprietary Class 3 3-9 Figure 3-4 Planar View of Array II-A with One Fuel Rod Storage Basket Model Table 3-10 Fuel Rod Basket Specifications Parameter Value Tube array 8x8 (no corner and adjacent storage locations)

Number of tubes 52 5 Tube OD, inch 0.625 Tube thickness, inch 0.035 Tube pitch, inch 0.937 Tube material SS 5

64 rods less three at each corner as seen in Figure 3-4.

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Westinghouse Non-Proprietary Class 3 4-1 4 ANALYTICAL METHODOLOGY This section describes the methodology used to determine acceptable storage criteria for the SFP racks, the Fuel Rod Storage Basket, and the Cask Area Rack. The results of these calculations are discussed in Section 5. The New Fuel Storage Rack analysis is described in Section 5.8. When not explicitly stated, calculations assumed nominal characteristics for the fuel and the fuel storage cells. The effect of the manufacturing tolerances is accounted for by combining the reactivity effects associated with manufacturing tolerances (rack, fuel, etc.) with other uncertainties as discussed below.

All calculations are performed using an explicit model of the fuel and storage cell geometry. KENO three-dimensional calculations model a 2-by-2 array of cells surrounded by periodic boundary conditions.

The three-dimensional KENO models assume 30 cm of water above and below the active fuel length.

Additional KENO models with more than four cells and different boundary conditions are generated to investigate the effect of eccentric fuel assembly positioning and interfaces between racks. These models are discussed in the appropriate sections to follow.

There have only been two assembly designs used at Turkey Point, the 15x15 STD and 15x15 OFA fuel designs. Over the years, different variations of OFA fuel have been used at Turkey Point. The various OFA fuel types are differentiated by the grids and the composition of structural materials. The presence of grids are not included in the analysis herein as discussed in Section 4.1.2.3.

As seen in Table 3-2, the only additional differences between fuel designs are the slightly differing GT/IT inner and outer diameter. As a result and supported by the work in Reference 2, the STD fuel design is chosen as the design basis fuel design.

4.1 DEPLETION ANALYSIS This section describes the methods used to determine the conservative and bounding inputs for the generation of isotopic number densities, which are then used in subsequent Monte Carlo simulations for the criticality analyses. [

]a,c 4.1.1 Depletion Modeling Simplifications & Assumptions There are several different combinations of fuel designs including differing mechanical designs, operating conditions, and BA types that need to be considered when performing the depletion analysis. To facilitate the analysis, three design basis fuel assembly criticality fuel designs are determined, one for unblanketed Pre-EPU fuel, one for Pre-EPU and Post-EPU mid enriched blanket design fuel, and one for a Post-EPU fully enriched fuel design.

Depletion calculations are performed for each unique Criticality Fuel Design considering previous operating history as well as planned operation for mid and fully enriched fuel designs using the 2D PARAGON lattice transport code (Reference 4). General modeling assumptions for depletion calculations are given. Deviations are specifically addressed:

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Westinghouse Non-Proprietary Class 3 4-2

• Each assembly is represented by 26 axial nodes (3D isotopics are generated from the compilation of 26 separate, node specific PARAGON calculations)

• The 26 nodes are chosen to capture the important axial features to ensure the end effect is properly captured. As a result, due to the blanket and cutback zones, there are 20 central 6 zones, with 4 zone following (top and bottom), followed further by a 2 and final 6 zone on both top and bottom of the assembly.

• Input for each 2D axial node is a function of its own bounding combination of operating parameters, including axial power, moderator density, and fuel temperature.

• Reflective boundary conditions are applied to the X and Y surfaces of the fuel assembly model to simulate an infinite array.

• Depletion conditions are chosen to conservatively maximize the reactivity at a given burnup (hardened spectrum, higher plutonium production, etc.).

• Once the fuel assembly is depleted to a desired assembly-average burnup, it is allowed to decay to conservatively increase reactivity to its peak value after discharge. The 135Xe concentration is set to zero.

• All neutronically important fission products are explicitly represented; there are no lumped fission products.

• For fuel assemblies which contain IFBA and have operated, the residual 10B concentration is set to zero.

• For Pre-EPU fuel without blankets, isotopics are generated for 2.0, 3.0 and 4.0 wt.% U-235 fuel, while for Post-EPU fuel (for which Post-EPU blanketed fuel bounds Pre-EPU blanketed fuel) isotopics are generated at 2.0, 3.0, 4.0 and 5.0 wt.% U-235.

• [

]a,c

• In general, depletion isotopics for use in the Criticality Analysis are generated every 2000 MWd/MTU.

• Criticality Fuel Design 2 will encompass blanketed Post-EPU operation (inclusive of input) as well as blanketed Pre-EPU operation (assumption). See section 4.1.2.2.6 for a discussion of absorber input related to this assumption.

• Gadolinium is conservatively not included in the depletion models.

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Westinghouse Non-Proprietary Class 3 4-3 4.1.2 Fuel Depletion Parameter Selection 4.1.2.1 Fuel Isotopic Generation Strategy This section outlines how parameters are selected for use in the fuel depletion calculations to generate isotopic number densities. For the purposes of this analysis, the isotopic number densities generated are differentiated by criticality fuel design, fuel enrichment, burnup, and decay time after discharge.

Isotopic number densities generated to support burnup credit in this analysis are based on conservative and bounding in-reactor operating conditions by depletion of 2-D axial nodes in infinite reactor geometry as discussed in Section 4.1.2.2. Once the fuel has been depleted to a desired burnup, it is decayed to its most reactive state (100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />) and any residual Xenon is removed. The isotopic inventory from PARAGON is then brought to cold conditions, 68°F and 14.7 psia. Credit is then taken for the decay of 241 Pu to 241Am (decay credit).

[

]a,c Based on the Turkey Point Units 3 & 4 fuel management, fuel isotopic number densities are calculated at enrichments of max. fresh (if less than 2 wt.%), 2, 3 and 4 wt.% 235U for Criticality Fuel Design 1. For Criticality Fuel Design 2 and 3, enrichments of max. fresh (if less than 2 wt.%), 2, 3, 4 and 5 wt.% 235U were modeled as well. Decay times of 10, 15 and 20 years were determined for Criticality Fuel Design 1 and 2.5, 5, 10, 15, 20 and 25 years for Criticality Fuel Designs 2 and 3. Fresh fuel modeled in this analysis conservatively excludes 234U and 236U.

4.1.2.2 Reactor Operation Parameters The reactivity of the depleted fuel in the SFP is determined by the in-reactor depletion conditions. The conditions experienced in the reactor impact the isotopic composition of fuel being discharged to the SFP.

Reference 8 provides practical guidance for criticality safety analysts in line with current recommendations. Reference 8 heavily draws upon Reference 11 which provides discussion on the core operation parameters important to SFP criticality. This section outlines the parameters used in generating the fuel isotopics for the criticality fuel designs and why they are appropriate for use in this analysis. The operating conditions of the fuel selected for modeling are provided in Section 4.1.4.

4.1.2.2.1 Soluble Boron Concentration The soluble boron concentration in the reactor during operation impacts the reactivity of fuel being discharged to the SFP. Because boron is a strong thermal neutron absorber, its presence hardens the neutron energy spectrum in the core, creating more plutonium.

Based on guidance from Reference 11, establishment of a bounding value for the maximum average boron per cycle based on boron let-down curves would enable more straightforward application of the depletion analyses, a constant cycle average soluble boron concentration (Equation 4-1) which assumes 19.9 at% 10B in place of a soluble boron letdown curve is considered appropriately conservative. To WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-4 determine the maximum cycle average soluble boron concentration, fuel management strategies for Turkey Point Units 3 & 4 have been reviewed. Table 4-1 provides the cycle average soluble boron concentration for Pre-EPU cycles for Units 3 and 4, while Table 4-2 provides the same for Post-EPU cycles including projected fuel management with unblanketed fuel.

=1

=

Equation 4-1

where,

= the cycle average soluble boron concentration i = the ith burnup step average soluble boron concentration

= the burnup step number

= the total number of burnup steps in the cycle

= the step burnup

= the cycle burnup

[

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-5 Table 4-1 Pre-EPU Cycle Average Soluble Boron Concentration (ppm)

Unit 3 Unit 4 Cycle #

(ppm) Blanket (ppm) Blanket Cycle 1 505 No 505 No Cycle 2 532 No 445 No Cycle 3 422 No 345 No Cycle 4 413 No 451 No Cycle 5 432 No 206 No Cycle 6 426 No 540 No Cycle 7 453 No 401 No Cycle 8 724 No 401 No Cycle 9 584 No 403 No Cycle 10 691 No 684 No Cycle 11 709 No 706 No Cycle 12 571 No 611 No Cycle 13 593 No 578 No Cycle 14 611 Yes 672 No Cycle 15 715 Yes 543 No Cycle 16 668 Yes 708 Yes Cycle 17 662 Yes 692 Yes Cycle 18 753 Yes 729 Yes Cycle 19 711 Yes 738 Yes Cycle 20 808 Yes 768 Yes Cycle 21 692 Yes 746 Yes Cycle 22 793 Yes 749 Yes Cycle 23 759 Yes 709 Yes Cycle 24 745 Yes 773 Yes Cycle 25 603 Yes 686 Yes WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-6 Table 4-2 Post-EPU Cycle Average Soluble Boron Concentration (ppm),

Blanketed Fuel Cycle # Unit 3 Unit 4 Cycle 26 790 797 Cycle 27 882 817 Cycle 28 743 795 Cycle 29 779 797 Cycle 30 757 748 Cycle 31 834 814 Cycle 32 816 781 Cycle 33 N/A 853 Projected Criticality Fuel Design 3 Transition and Equilibrium Cycles, Unblanketed Fuel (mixed in transition)

Transition 1 987 Transition 2 985 Equilibrium 1 995 Equilibrium 2 987 4.1.2.2.2 Fuel Temperature The fuel temperature during operation impacts the reactivity of fuel being discharged to the SFP.

Increasing fuel temperature increases resonance absorption in 238U due to Doppler broadening which leads to increased plutonium production, increasing the reactivity of the discharged fuel. Therefore, utilizing a higher fuel temperature is more conservative.

The temperature input for this analysis is calculated by the FIGHTH code (Reference 12), which determines the fuel temperatures used as input to PARAGON for depletion calculations. FIGHTH calculates the steady state radial temperature distribution at each burnup, given the local value of the heat generation rate in the rod, the moderator temperature, and coolant flow rate. The FIGHTH model accounts for radial variations of the heat generation rate, thermal conductivity, thermal expansion in the fuel pellet, elastic deflection for the cladding, and pellet-clad gap conductance. The FIGHTH code is used in the development of cross-sections for in-core calculations as part of the standard reload methodology.

As discussed, the important input parameters used by FIGHTH for determining fuel temperature are power level, moderator temperature, and coolant flow rate. [

]a,c Selection of moderator temperature is performed as discussed in Section 4.1.2.2.5. [

] a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-7 4.1.2.2.3 Operating History and Specific Power Reference 8 states that the power density, moderator and fuel temperature are inter-related, and that depletion at high power, moderator temperature and fuel temperature is typically conservative (noting that a small reactivity increase may be observed from a low power coast down at end of life, and also that this is excluded from load follow which has other contributing factors). Reference 8 draws on the technical guidance in Reference 11.

Ultimately, Reference 11 indicates that the selection of a high operating power, and therefore specific power to maximize fuel temperature (and moderator temperature), appropriate as the subordinate parameter is acceptable and recommends a 0.002 k bias to account for any operating history impacts, as a result, a 0.002 k bias is taken on operational history.

Final depletion input utilizes conservative Criticality Fuel Design dependent values discussed in Section 4.1.4.

4.1.2.2.4 Axial Relative Power As discussed in NUREG/CR-6801, Recommendations for Addressing Axial Burnup in PWR Burnup Credit Analyses (Reference 13), as fuel is operated in the reactor, the axial center of each assembly generates more power than the ends. This leads to the burnup of each assembly varying along its length.

Because the axial center of each assembly generates most of the power, the burnup in the axial center of the assembly is greater than the assembly average. At the same time, the ends of the assembly are less burned than the assembly average. When the burnup difference between the axial center and end of an assembly is large enough, reactivity becomes driven by the end of the assembly rather than the axial center, as the under depletion of the ends (the end-effect) overcomes the reactivity loss due to neutron leakage.

This section describes the methodology used to determine the limiting axial relative power input for distributed profile simulations.

Criticality Fuel Design 1 (Pre-EPU Non-Blanketed Fuel)

For Criticality Fuel Design 1, limited data is available compared to more recently operated assemblies encompassing Criticality Fuel Designs 2 and 3. The same analysis supporting Reference 2 was used for Criticality Fuel Design 1. Briefly, a total of 1361 measured axial burnup profiles (discharge) for non-blanketed fuel from both Unit 3 and 4 were examined. Data was only available from 12 equally spaced axial nodes. Relative burnup of the 10th, 11th and 12th nodes were compared as well as the 11th plus 12th and 12th plus 1/2 of the 11th. Candidate assembly profiles using these metrics were identified for those with the minimum relative burnup for each of these relative burnups. Distinct profiles were identified at different burnups which were conservative in terms of reactivity (of an all cell model). The different burnup of these candidate assemblies led to the burnup bin structure used for Criticality Fuel Design 1.

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Westinghouse Non-Proprietary Class 3 4-8 Criticality Fuel Designs 2 (Pre and Post EPU Blanketed Fuel) & 3 (Post-EPU Non-Blanketed Fuel)

For Criticality Fuel Designs 2 and 3, input is derived from planned or operated assembly axial relative burnup profiles from all post EPU cycles (Unit 3, cycles 26-32 and Unit 4, cycles 27 through 33) as well as the transition to 24 month cycle models (2) and equilibrium cycle models (2). These profiles will be used along with the uniform axial burnup profile as one of the conservative input parameters to develop isotopics to ultimately calculate the minimum burnup requirements provided in Section 5.

As driven by the end-effect, the following methodology was used to ensure that the appropriate axial burnup profiles were selected for this analysis. Fuel management calculations containing readily available data discussed herein were utilized to develop a database of axial burnup profiles specific to Turkey Point Units 3 & 4. [

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-9 Table 4-3 [ ]a,c a,c For the reasons discussed herein, it is typical for fuel modeled assuming a uniform axial burnup profile to be more reactive early in life than fuel modeled with a distributed profile. To address this, isotopics were created for fuel assuming both a uniform profile (for burnup bin 1) and distributed profile (for the design basis fuel). These isotopics were used during the Monte Carlo calculations to determine the minimum burnup requirements to ensure the limiting profile (uniform vs design basis distributed) has been used.

4.1.2.2.5 Moderator Temperature Criticality Fuel Design 1 (Pre-EPU Non-Blanketed Fuel)

For Criticality Fuel Design 1, a bounding constant temperature is applied along the entire length of the assembly as discussed in Reference 2 (See Table 4-4).

Criticality Fuel Designs 2 (Pre and Post EPU Blanketed Fuel) & 3 (Post-EPU Non-Blanketed Fuel)

Moderator temperature input is axially varying along the fuel assembly. This section describes the methods used to determine limiting axial moderator temperature profiles. These profiles will be used WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-10 together with axial distributed and uniform burnup profiles to calculate the isotopics used in generating the burnup requirements provided in Sections 5.2.2, 5.2.3 and 5.2.4. Note that Criticality Fuel Design 1 input is more conservative and is a constant conservative value based on the maximum assembly exit temperature (the same as in Reference 2) along the entire assembly.

Selecting an appropriate moderator temperature profile is important as it impacts the moderator density and therefore the neutron spectrum during depletion as discussed in References 8 and 11. An appropriate moderator temperature ensures the impact of moderator density on the neutron spectral effects is bounded, conservatively biasing the isotopic inventory of the fuel.

[

]a,c 4.1.2.2.6 Burnable Absorber Usage Burnable absorber usage at Turkey Point Units 3 & 4 has been considered for this analysis and conservative assumptions have been used to bound the effects of BAs on fuel isotopics. The BAs that have been evaluated include both discrete and integral BAs. Criticality Fuel Design 1 contained PYREX or WABA. Criticality Fuel Designs 2 and 3 may contain IFBA and Gadolinium absorbers. Criticality Fuel Design 2 also contained WABA during Pre-EPU operation. Gadolinium as outlined in Reference 8 can be addressed by simply ignoring its presence in the analysis (its a net reducer to reactivity) and is handled as thus herein. IFBA is included in maximum expected number, length and concentration in depletion analysis for Criticality Fuel Designs 2 and 3 as given in Section 4.1.4.

WABA Considerations As indicated, WABA was used in Pre-EPU operation (blanketed and unblanketed) which is covered by Criticality Fuel Designs 1 and 2. Reference 2 analysis indicated that 12 PYREX fingers (maximum loaded) was more conservative than 20 WABA fingers. As a result, 12 PYREX is used in depletion models. Criticality Fuel Design 2 isotopics are conservatively derived for Post-EPU conditions with a maximum expected IFBA impact, but do not include WABA. It is assumed that all conservative Post-EPU (e.g., 148 IFBA at 1.25X) input is bounding of Pre-EPU operation with WABA. No Post EPU operation contained WABA and future fuel will be Criticality Fuel Design 3.

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Westinghouse Non-Proprietary Class 3 4-11 HVFD Considerations In Turkey Point Units 3 and 4 operations, HVFD absorbers have been inserted in a few highly burned fuel assemblies on the core periphery during the third cycle of operation. These part-length absorber inserts are present only near the mid-plane of the fuel assembly's axial length to reduce the fluence at critical weld locations along the core vessel for the purpose of vessel life extension. HVFDs have not been used since Cycles 23 and 24 at Units 3 and 4, respectively, and they will not be used in EPU fuel. The accumulated burnup under the HVFD is always less than 4 GWd/MTU.

For all assemblies which contained hafnium inserts, the distributed burnup profiles are limiting. The significantly under burned top nodes of the fuel assemblies are most important to the determination of the keff of the problem. The HVFDs push the neutron flux out of the middle of the core and toward the ends of the fuel during fuel depletion. The elevated flux in the top portion of the core causes the nodes that are most important to reactivity to be more depleted than they would have been without HVFDs. The over depletion of the top nodes causes the reactivity of a fuel assembly that contained an HVFD in its third cycle to be bounded by the same fuel assembly that is depleted without an HVFD which also assumed a bounding distributed burnup profile. Note that selection of limiting axial burnup profiles for pre-EPU fuel described in Section 4.1.2.2.4 included shapes from assemblies with HVFDs.

4.1.2.3 Fuel Assembly Physical Changes with Depletion Reference 8 discusses fuel assembly physical changes with depletion, and specifically calls out the need to address the potential reactivity impact from fuel rod changes (clad creep, fuel densification/swelling) and material dependent grid growth. Appendix B of Reference 8 is based on Westinghouse methodology and indicates that holistically the impact of fuel rod changes with depletion are conservative. [

]a,c 4.1.3 Design Basis Models Criticality Fuel Designs 1, 2 and 3 were identified in Section 2 and will be modeled separately as three separate design basis assemblies. With only discharge shapes utilized for Criticality Fuel Design 1, the axial burnup profiles identified are the design basis profiles for that design. However, the selection of the final axial profile to be utilized for Criticality Fuel Designs 2 and 3 is described herein. The combination of the Criticality Fuel Design along with the associated depletion input for each design (including the axial burnup profile) constitute the design basis models.

In general, for each Burnup Bin, within each Criticality Fuel Design, a reactivity comparison would be made for an all cell storage model within the burnup bin for each Candidate Profile. [

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-12

[

]a,c 4.1.4 Final Depletion Parameters This section outlines the parameters used in the final depletion calculations. The depletion parameters used to generate the conservative, depleted isotopics for Criticality Fuel Designs 1 are given in Table 4-4.

The depletion parameters used to generate the conservative, depleted isotopics for Criticality Fuel Designs 2 and 3 are given in Table 4-5. Table 4-6, Table 4-7 and Table 4-8 contain the Limiting Axial Burnup Profiles modeled for Criticality Fuel Designs 1, 2 and 3 respectively. Table 4-9 and Table 4-10 contain the limiting axial moderator temperature profiles modeled with Criticality Fuel Designs 2 and 3, respectively (a single bounding value is used for Criticality Fuel Design 1 as indicated in Table 4-4).

Table 4-4 Criticality Fuel Design 1 Depletion Parameters Parameter Value(s)

Core Power (MW) 2990, 2714 Core Loading (MTU) 73.206 Pyrex Rods (maximum) 12 Pyrex Length (in) 144 Pyrex Exposure (GWd/MTU) 23.2 Blanket Length (in) N/A Blanket Type (in) N/A Min Cutback Length (in) N/A Max Cycle Average Boron (ppm) [ ]a,c Fuel Pellet Theoretical Density (%) [ ]a,c Min Single Pump Flow (gpm) 88500 (default)

Moderator Temperature °F 630.5, 624.1 Relative Power (axial) Table 4-6 Notes: (1) Pyrex is inserted for the maximum observed burnup.

(2) Core power and Moderator Temperature contain two values, the first is for up to 37.6 GWd/MTU and the second is up to the maximum burnup analyzed.

Cutback is the distance between the end of the IFBA and the start of the blanket.

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Westinghouse Non-Proprietary Class 3 4-13 Table 4-5 Criticality Fuel Design 2 and 3 Depletion Parameters Parameter Value(s)

Core Power (MW)* [ ]a,c Core Loading (MTU) 73.000 IFBA Pattern 148 IFBA Length (in) 128 IFBA Loading (mg/in) [ ]a,c WABA Pattern 0 Blanket Length (in) 8 Blanket Type (in) Annular^

Min Cutback Length (in) 0 Max Cycle Average Boron (ppm) [ ]a,c Fuel Pellet Theoretical Density (%) [ ]a,c Min Single Pump Flow (gpm) 86900 CFD 2 CFD 3 Blanket Enrichment (w/o) 2.6 Full Relative Power (axial) Table 4-7 Table 4-8 Temperature Profile (axial) Table 4-9 Table 4-10

• Used in Burnup Bin 1, 2 and 3, respectively.

^Annular used in the depletion models. Solid used in the criticality models.

Cutback is the distance between the end of the IFBA and the start of the blanket.

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Westinghouse Non-Proprietary Class 3 4-14 Table 4-6 Limiting Relative Burnup Profiles for Criticality Fuel Design 1 Node Burnup Range (GWD/MTU) a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-15 Table 4-7 Limiting Relative Burnup Profiles for Criticality Fuel Design 2 a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-16 Table 4-8 Limiting Relative Burnup Profiles for Criticality Fuel Design 3 a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-17 Table 4-9 Limiting Moderator Temp. Profiles (°F) for Criticality Fuel Design 2 a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-18 Table 4-10 Limiting Moderator Temp. Profiles (°F) for Criticality Fuel Design 3 a,c 4.2 CRITICALITY ANALYSIS This section describes the reactivity calculations and evaluations performed in developing the burnup requirements for fuel storage in the Turkey Point Units 3 & 4 SFPs. KENO models generated for Criticality Fuel Designs 1, 2 and 3 were evaluated for different storage arrays within Region 1, 2 and the Cask Area Rack. Assembly initial enrichment, average burnup, and decay time (or fresh IFBA) are varied to determine appropriate storage limits based on resulting reactivity. Reactivity margin is added to the KENO reactivity calculations for the generation of burnup requirements or fresh fuel IBA requirements as discussed in Section 4.2.2 to account for manufacturing deviations. The New Fuel Storage Rack analysis is discussed in Section 5.8.

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Westinghouse Non-Proprietary Class 3 4-19 4.2.1 Fuel Category, Storage Arrays and Other Storage Assembly storage is controlled through the fuel categories assigned to each storage location within the analyzed storage configurations defined in this section. Storage configurations are segmented by SFP Region (I and II). (For the Cask Area Rack, fresh 5 w/o fuel is evaluated for storage in all locations.) Fuel categories are ranked by the maximum allowable reactivity of the individual assembly in a storage cell/location within a storage configuration. A lower fuel category is more reactive than a higher fuel category. Each 2x2 configuration is analyzed with fuel of the maximum allowable reactivity for the category. Unique storage locations were determined for which to assign fuel categories using the desired storage configurations for use in the Turkey Point Units 3 and 4 SFPs.

Table 4-11 gives the fuel categories ranked by reactivity within the appropriate region of the SFP. The cask area rack is discussed separately. The relative placement of assemblies from the fuel categories as well as the number and location of reactivity suppressing devices necessary to meet the acceptance criteria are shown in Figure 4-1 and Figure 4-2 for Regions I and II of the SFP respectively. It is not necessary to use all defined configurations in the spent fuel pool. In all configurations, an assembly of lower reactivity (higher fuel category) can replace an assembly of higher reactivity (lower fuel category) within the same region.

Table 4-11 Fuel Categories Ranked by Reactivity I-1 Higher Reactivity I-2 Region I I-3 Lower Reactivity I-4 II-1 Higher Reactivity II-2 II-3 Region II II-4 II-5 II-6 Lower Reactivity Notes:

1. Fuel Category is ranked by decreasing order of reactivity without regard for any reactivity-reducing mechanisms, e.g., Category I-2 is less reactive than Category I-1, etc. The more reactive fuel categories require compensatory measures to be placed in Regions I and II of the SFP, e.g., use of water filled cells, Metamic inserts, or full length RCCAs.

2. Any higher numbered fuel category can be used in place of a lower numbered fuel category from the same Region.

3. Category I-1 is fresh unburned fuel up to 5.0 wt.% 235U enrichment.

4. Category I-2 is fresh unburned fuel that obeys the IFBA requirements of Equation 5-1.

5. All Categories except I-1 and I-2 are determined from Table 5-2, Table 5-3 and Table 5-4.

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Westinghouse Non-Proprietary Class 3 4-20 Array I-A 1-1 X Checkerboard pattern of Cateiory 1-1 assemblies and empty (water-filled) cells.

X 1-1 Array 1-B 1-4 1-4 Category 1-4 assembly in every ceH. 1-4 1-4 Anayl-C 1-2 1-4 1-2 1-2 Combination of Category 1-2 and 1-4 assemblies. Each Category 1-2 assembly shall contain a full length RCCA. 1-4 1-4 1-4 1-4 1-2 1-2 1-2 1-2 1-2 1-4 1-2 1-2 Array 1-D 1-3 1-3 Category 1-3 assembly in every cell: One of eYery four assemblies contains a full length RCCA. 1-3 1-3 Notf's:

I. In all arrays, an assembly of lower reactivity can replace an assembly of higher reactivity.

2. Category I-1 is fresh unburned fuel up to 5.0 wt.% 235U enrichment.

3. Category I-2 is fresh m1bumed fuel that obeys the IFBA requirements in Equation 5-1.

4. Categories I-3 and I-4 are detennined from requirements in Sections 5.2.2. 5.2.3 and 5.2.4 .

5. Shaded cells indicate that the fuel assembly contains a foll length RCCA.

6. X indicates au empty (water-filled) cell.

7. Atuibutes for each 2x2 anay are as stated in the defmitiou. Diagram is for illustrative pmposes only.

8. An empty (water-filJed) cell may be substituted for any foel containing cell in all storage anays.

Figure 4-1 Allowable Region I Storagf' Arrays WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-21 Ar.-ayll-A 11-1 11-1 X 11-1 Category II-I assembly in three of every four cells; one of every four cells is empty (water filled); the cell diagonal from the empty cell contains a Melamie insert or full length RCCA.

X 11-1 11-1 11-1 Arrayll-B 11-3 11-5 11-3 11-5 Checkerboard of Category II-3 and II-5 assemblies; two of every 11-5 11-3 11-5 11-3 four cells containing a Metamic insert or full length RCCA.

Arrayll-C 11-4 11-4 11-4 11-4 Category II-4 assembly in every cell with two of every four cells 11-4 11-4 11-4 11-4 a Melamie insert containing or full length RCCA.

Array 11-D 11-2 11-2 Category II-2 assembly in eve1y cell with three of every four cells containing a Metamic insert or full length RCCA. 11-2 11-2 Array 11-E 11-6 11-6 Category II-6 assembly in every cell with one of every four cells containing a Metamic insert or full length RCC A. 11-6 11-6 Notes:

l . In all arrays. an assembly of lower reactivity can replace an assembly of higher reactivity.

2. Fuel categories are detennined from requirements in Sections 5.2.2. 5.2.3 and 5.2.4.

3. Shaded cells indicate that the cell contains a Metamic inse11 or the fuel assembly contains a full length RCCA.

4. X indicates an empty (water-filled) cell.

5. Attributes for each 2x2 array are as stated in the definition. Diagram is for illustrative pmposes only.

6. An empty (water-filled) cell may be substituted for any fuel containing cell in all storage anays.

Figure 4-2 Allowable Region II Storage An-ays WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-22 Additional storage at Turkey Point Units 3 and 4 is available in the removable Cask Area Rack. The Cask Area Rack is modeled for unrestricted storage as it is a flux trap style rack with Boral absorber inserts.

Design information for the Cask Area Rack is given in Sections 3.4.2 and 3.4.3, with pertinent modeling assumptions given in Section 4.2.3.

The Fuel Rod Baskets are used to store loose fuel rods as needed. Fuel Rod Basket design information is given in Section 3.4.4 with additional modeling detail and results in Section 5.3. Description and results of other normal conditions for storage are given in Section 5.5.

4.2.2 Target keff Determination As discussed in Section 2.1, this analysis provides storage (burnup or IFBA) requirements such that the Turkey Point Units 3 & 4 SFPs remain subcritical in unborated conditions. To ensure that the burnup requirements generated are appropriate, a target keff value is created for each storage array at different enrichments (maximum fresh, 2, 3 and 4 wt.%, 235U for Criticality Fuel Design 1 and maximum fresh, 2, 3, 4 and 5 wt.% 235U for Criticality Fuel Designs 2 and 3). The target keff value accounts for the reactivity effect of applicable biases and uncertainties and includes administrative margin to ensure safety as shown in Equation 4-3.

Target k eff = ( & ) Equation 4-3

where, Acceptance Criterion = the maximum allowable keff for a storage array (see Section 2.1)

Admin Margin = the administrative margin (0.005 k) taken to provide additional certainty of safe operation (Biases & Uncertainties) = the amount of reactivity that accounts for biases and uncertainties in the reactivity calculation for each storage array The sum of biases are simply additive while the sum of uncertainties are statistically added as the root sum square of the individual reactivity uncertainties.

4.2.3 Keno Modeling Approach, Simplifications & Assumptions As discussed in Section 2.3.2, KENO (Version V.a) is the criticality code used to support this analysis.

KENO is used to determine the absolute reactivity of burned and fresh fuel assemblies loaded in storage arrays. Additionally, KENO is used to determine the reactivity sensitivity of these storage arrays to effects such as manufacturing tolerances, fuel depletion, eccentric positioning, and the allowable temperature range of the SFPs. KENO is also used to model accident scenarios and confirm there is sufficient soluble boron to meet the requirements of Section 2.1.

The methods used to model the fuel in normal and accident scenarios are discussed in the following sections. In KENO, the following modeling approach, modeling simplifications, and modeling assumptions have been made with regard to the fuel assembly:

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Westinghouse Non-Proprietary Class 3 4-23

• [

] a,c

• Only the active fuel length of the assembly is modeled in this analysis.

• In the active fuel length, the only assembly hardware modeled are the GTs and IT. Grids, sleeves, and top and bottom nozzles are not modeled. These are replaced by water. See Section 4.2.4.

• The effective multiplication factor of an infinite radial array of fuel assemblies or assembly patterns is used in the analysis using periodic boundary conditions.

• [ ]a,c Fresh IFBA credit is determined for Fuel Category I-2. See 4.2.1 for a description of fuel categories.

• [

]a,c

• RCCA modeling considering the following:

o [

]a,c

• Metamic inserts are modeled considering the following:

o [

]a,c o Insert thickness variation is included in the list of reactivity uncertainties.

o The Metamic panel is modeled up against the assembly as Metamic inserts are mounted to the assembly.

• Boral inserts are modeled considering the follow:

o Covers active fuel length (nominal length 147 inches) o Nominal 7.5 inch width [ ]a,c o Insert thickness variation is included in the list of reactivity uncertainties.

• Cask Area Rack Modeling Details:

o Cell pitch East/West of 10.10 [ ]a,c o Cell pitch North/South of 10.70 [ ]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-24 o Sheathing width of 7.533 nominal [ ]a,c

• [

]a,c 4.2.4 Impact of Structural Materials on Reactivity Over the years, different fuel types have been developed to meet the needs of the utilities. Differences between the fuel types could include changes in rod pitch, fuel rod dimensions such as pellet and cladding dimensions, and structural components such as grid material and volumes.

Each of the fuel types which have been or are planned to be operated at the plant need to be considered.

The structural materials of each fuel type do not need to be considered in the determination of the bounding fuel assembly design as discussed in Reference 8 in regards to grid material where 50 ppm is added to soluble boron requirements as recommended to neglect modeling grids 1. In addition to this, at least 30 cm of unborated water is modeled above and below the active region of the fuel when performing borated calculations to ensure that the amount of borated water near the fuel is not overestimated since top and bottom nozzles are not modeled.

4.2.5 Bias & Uncertainty Description Reactivity biases are known variations between the real and analyzed system and their reactivity impact is added directly to the calculated keff. Examples include the SFP temperature and code validation biases.

Uncertainties account for allowable variations within the real model whether they are physical (manufacturing tolerances), analytical (depletion uncertainty and validation bias uncertainty), or measurement related (burnup measurement uncertainty). Biases have a greater impact due to their direct 1

Reference 8 indicates this 50 ppm is also sufficient to offset the change in reactivity effect of tolerances under borated conditions (if modeling only unborated conditions for bias and uncertainty calculations).

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Westinghouse Non-Proprietary Class 3 4-25 addition to the total sum of bias and uncertainty. Uncertainties are statistically added as the root sum square of the individual reactivity uncertainties.

In this analysis, the biases and uncertainties are calculated to account for any reactivity effects due to manufacturing tolerances, enrichment, depletion and code accuracy.

4.2.5.1 Bias & Uncertainty Descriptions including Manufacturing Tolerances Reactivity biases and uncertainties as a result of manufacturing tolerances and other SFP characteristics are discussed in this section and the following subsections. KENO is used to quantify reactivity effects.

[

]a,c applied. The fuel and rack tolerances considered in the analysis are:

1. Rack cell ID

2. Rack cell pitch

3. Rack cell wall thickness

4. Fuel rod pitch

5. Fuel clad OD

6. Fuel clad ID

7. GT/IT dimensions

8. Pellet OD

9. Fuel initial enrichment

10. Metamic/Boral thickness

11. Boral Width (Metamic modeled as minimum)

12. Insert Cavity Thickness

13. Insert Sheath Thickness

14. Insert Sheath Width

15. Flux Trap Gap (not explicitly modeled as described herein)

Additional uncertainties included are the following:

1. Burnup measurement uncertainty

2. Depletion uncertainty

3. Code bias uncertainty Biases incorporated include the following:

1. Operational uncertainty bias

2. Fission product and actinide worth bias

3. Eccentric positioning bias

4. Code bias WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-26

5. Fission gas bias

6. Grid growth bias

7. Temperature bias To determine the k associated with each manufacturing tolerances, the keff calculated for the reference condition is compared to the keff from a calculation with the tolerance included. In general, the reactivity effect of each tolerance is calculated as shown in Equation 4-4. Additional details are provided in subsequent subsections for select tolerances.

= 1 + 2.012 + 2 Equation 4-4

where, k1 = keff with the tolerance included kR = keff for the reference case 1 = Monte Carlo standard deviation for the case with the tolerance included R = Monte Carlo standard deviation of the reference case 2.0 = multiplier used to conservatively exceed a one-sided 95/95 tolerance interval 4.2.5.1.1 Cladding Tolerance Reactivity Uncertainty

[

]a,c 4.2.5.1.2 Initial Fuel Enrichment Reactivity Uncertainty

[

]a,c 4.2.5.1.3 Guide Tube and Instrument Tube Reactivity Uncertainty For the GT/IT, the reactivity effect is captured together since they are modeled the same way for both bounding design basis assemblies. Thickness variation is captured in both the inner and outer dimension tolerance evaluation. The reactivity effect of GT/IT dimensions is small.

4.2.5.1.4 Burnup Measurement Uncertainty WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-27 The burnup measurement uncertainty is taken to be the reactivity change associated with a 5 percent change in burnup. [

]a,c 4.2.5.1.5 Depletion Uncertainty The depletion uncertainty takes into account the potential reactivity misprediction of the depletion code.

[

]a,c 4.2.5.1.6 Metamic Insert Thickness Tolerance Uncertainty The metamic insert thickness uncertainty impact was handled by varying the outer location of the metamic insert (the inside edge is against the rack wall).

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Westinghouse Non-Proprietary Class 3 4-28 4.2.5.1.7 Flux Trap Gap Reactivity Uncertainty Flux trap gap tolerance worth is not explicitly calculated; however the rack cell pitch tolerance cases explicitly include the effect of cell pitch and flux trap gap tolerance since the rack pitch would change the flux gap width and vice versa.

4.2.5.1.8 Insert Sheath Width Reactivity Uncertainty Reference 8 indicates that for flux-trap rack designs, the uncertainty due to the manufacturing tolerance on the sheathing width is small but cannot generically be declared negligible. Despite not crediting the Boraflex, insert sheath width tolerance reactivity uncertainty is determined.

4.2.5.1.9 Code Bias Uncertainty An uncertainty in the predictive capability of Scale 6.2.4 and the associated cross-section library is considered in the analysis. The uncertainty from the validation of the calculational methodology is discussed in detail in APPENDIX A.

4.2.5.1.10 Operational Uncertainty Bias

[

]a,c 4.2.5.1.11 Grid Growth Bias The grid growth bias comprises the reactivity impact of grid growth due to irradiation. [

]a,c The fuel assembly grids expand over the course of operation in the reactor, leading to a larger overall assembly envelope. This phenomenon has two separate potential effects on spent fuel pool reactivity. The first effect is due to the change in isotopic inventory due to the larger rod pitch impacting the in-core energy spectrum. The second effect is the reactivity impact due to the potential rod pitch increase during storage. [

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Westinghouse Non-Proprietary Class 3 4-29

[

]a,c 4.2.5.1.12 Fission Product and Minor Actinide Worth Bias A common approach to the validation of cross-sections is by benchmarking critical experiments that are designed to closely represent the configurations of the desired criticality application. The validation of fission products, however, is more difficult because few critical experiments are available. Due to the limited availability of fission product benchmark data, a bias was incorporated in the criticality safety analysis.

Reference 15 presents findings that show for minor actinide and fission product nuclides for which adequate critical experiment data are not available, calculations of keff uncertainty due to nuclear data uncertainties can be used to establish a bounding bias value which was approximately 1.5 percent of the worth of the minor actinides and fission products.

[

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-30 4.2.5.1.13 Fission Gas Bias A bias was generated by determining the reactivity impact of the important isotopes which may not be present in the active assembly region. This impact used Equation 4-4 (the tolerance case is the perturbed case) except the effect is treated as a bias. [

]a,c 4.2.5.1.14 Eccentric Fuel Assembly Positioning Bias The fuel assemblies are assumed to be nominally located in the center of the storage rack cell; however, it is recognized that an assembly could in fact be located eccentrically within its storage cell. Reference 8 indicates that assembly eccentric positioning should be considered in racks without absorber panels on all four sides. Only the Cask Area Rack is crediting absorbers on all four sides therefore, in this analysis, an eccentric positioning bias is determined for Region I and II storage arrays.

To quantify the reactivity effects of eccentrically located fuel within a fuel storage cell, [ a 4 x 4 infinite model is used for all Region I and II storage arrays. Two variations of eccentrically located fuel are simulated within the 4 x 4 model. First is a simulation with all fuel assemblies in the model moved toward a center point as close together as possible. Second is a simulation with all fuel assemblies in the 4 x 4 storage cell moved as far apart (the storage cell corners) as possible. The maximum reactivity difference, as calculated with Equation 4-4 is applied as a bias.

4.2.5.1.15 SFP Temperature Bias The Turkey Point Units 3 & 4 SFPs operate within an allowable range. [

]a,c 4.2.5.1.16 Borated and Unborated Biases and Uncertainties Reference 3 requires each SFP to have keff to be < 0.95 under borated conditions accounting for all applicable biases and uncertainties. [

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Westinghouse Non-Proprietary Class 3 4-31

[

]a,c 4.2.5.2 Bias and Uncertainty Calculation Results Results of the bias and uncertainty analysis for each Criticality Fuel Design for each SFP storage configuration as well as the Cask Area Rack are given here and in subsequent subsections. Storage configuration I-A contains two empty cells and does not require burnup, and as thus, results are given here in Table 4-12. Also, the Cask Area Rack does not require burnup, with biases and uncertainties given in Table 4-13.

Table 4-14 and Table 4-15 contains Biases and Uncertainties performed to support determination of Configuration I-C fresh IFBA credit limits for Category I-2. Configuration I-C contains a mix of Fuel Category I-2 and I-4 assemblies. With the Category I-4 burnup limits set by Array I-B analysis, conservative biases and uncertainties were developed for Configuration I-C. See section 4.2.6 for details of the Fresh IFBA credit analysis and details of the conservative bias and uncertainty selection for Configuration I-C. The remaining Region I and II bias and uncertainty calculations are criticality fuel design specific and given in Sections 4.2.5.2.1, 4.2.5.2.2 and 4.2.5.2.3.

Since Array II-B contains Fuel Category II-3 and II-5 assemblies, bias and uncertainty determination (and determination of the target keff and burnup limits) comprises additional methodology. See Section 4.2.7 for general burnup limit determination methodology. [

]a,c See Section 5.8.2 for new fuel storage rack bias and uncertainty analysis and results.

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Westinghouse Non-Proprietary Class 3 4-32 Table 4-12 Biases and Uncertainties for Configuration I-A a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-33 Table 4-13 Biases and Uncertainties for the Cask Area Rack a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-34 a,c Table 4-14 Biases and Uncertainties for Configuration I-C (All I-2 Fuel) - Part 1 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-35 Table 4-15 Biases and Uncertainties for Configuration I-C (All I-2 Fuel) - Part 2 a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-36 4.2.5.2.1 Criticality Fuel Design 1 a,c Table 4-16 CFD 1 Biases and Uncertainties for Array I-B WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-37 a,c Table 4-17 CFD 1 Biases and Uncertainties for Array I-D WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-38 a,c Table 4-18 CFD 1 Biases and Uncertainties for Array II-A WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-39 a,c Table 4-19 CFD 1 Biases and Uncertainties for Array II-B*

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-40 Table 4-20 CFD 1 Biases and Uncertainties for Array II-C a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-41 Table 4-21 CFD 1 Biases and Uncertainties for Array II-D a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-42 Table 4-22 CFD 1 Biases and Uncertainties for Array II-E a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-43 4.2.5.2.2 Criticality Fuel Design 2 Table 4-23 CFD 2 Biases and Uncertainties for Array I-B a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-44 Table 4-24 CFD 2 Biases and Uncertainties for Array I-D a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-45 a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-46 Table 4-26 CFD 2 Biases and Uncertainties for Array II-B* a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-47 Table 4-27 CFD 2 Biases and Uncertainties for Array II-C a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-48 Table 4-28 CFD 2 Biases and Uncertainties for Array II-D a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-49 a,c Table 4-29 CFD 2 Biases and Uncertainties for Array II-E WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-50 4.2.5.2.3 Criticality Fuel Design 3 Table 4-30 CFD 3 Biases and Uncertainties for Array I-B a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-51 a,c Table 4-31 CFD 3 Biases and Uncertainties for Array I-D WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-52 Table 4-32 CFD 3 Biases and Uncertainties for Array II-A a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-53 Table 4-33 CFD 3 Biases and Uncertainties for Array II-B* a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-54 Table 4-34 CFD 3 Biases and Uncertainties for Array II-C a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-55 a,c Table 4-35 CFD 3 Biases and Uncertainties for Array II-D WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-56 Table 4-36 CFD 3 Biases and Uncertainties for Array II-E a,c 4.2.5.3 Reactivity of Geometry Changes Due to Irradiation

[

]a,c

[

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-57 4.2.6 Fresh IFBA Credit Analysis Configuration I-C contains fuel Categories I-2 and I-4 with four different 2x2 variations (sub-configurations) as defined in Section 4.2.1. Configuration I-B is an all cell of Category I-4 assemblies.

Analysis of Array I-B is used to determine the burnup limits, and hence the isotopics for fuel Category I-4 assemblies. With fuel Category I-4 assemblies set, Array I-C is analyzed as follows:

1. [

]a,c 4.2.7 Burnup Limit Determination

[

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-58

[

. ]a,c 4.2.8 Interface Definitions The interface of storage arrays can require restrictions in addition to those imposed by the infinite array analysis. The allowable interface configurations and reactivity results are given in Section 5.4. The following subsections discuss the methods for the various interface requirements.

4.2.8.1 Within Region Interfaces

[

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-59 Following these rules, eve1y 2x2 configuration matches an analyzed condition and therefore no interface-specific analyses are required. Gaps between the same region rack modules are conservatively neglected, i.e., cells located across a rack-to-rack gap are considered the same as cells directly facing each other within a rack. Tue configurations where Region II cells face Region I rack modules require additional analyses and are discussed in Section 4.2.8.2.

No special considerations need be given to cells facing the pool wall or other racks.

11-4 11-5 ll-3 ll-3 X ll-1 11-4 ll-4 ll-5 ll--3 11-1 ll-1 ll-4 U-5 ll-3 ll--3 X Il-1 11-4 11-4 11-5 ll--3 D-1 ll-1 Figure 4-3 Examplt" oflnterfares between Region II Configurations (Shaded cells contain an inse11 and X indicates an empty (water-filled) cell.)

4.2.8.2 Region I to Region II Interface I. [

] a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 4-60

4. [

Figure 4-4 shows an example interface model.

a.c Figurt 4-4 Region I and R~on II Interface Model Example 4.2.8.3 Cask Area Rack Interfaces The Cask Area Rack bas sufficient absorber panels that the maximum ~ is much less than the limiting

~ in Region I or Region II. Furthermore, the Cask Area Rack has Boral panels on the exterior of the rack so there is no local increase in reactivity at the rack interface. Consequently, there are no interface loading constraints on the Cask Area Rack/Region I or Cask Area Rack/Region II interface.

4.2.9 Soluble Boron Credit Soluble boron is credited in the Turkey Point Units 3 & 4 SFPs to keep ~tr < 0.95 under all normal and credible accident scenarios. Accident conditions typically considered are the following :

• Misloaded fresh fuel assembly or assemblies in a storage rack

• Inadvertent removal of an absorber inse11

• . Spent fuel pool temperanire greater than nonnal operating range

• Loss of water gap between Region I and Region II due to seismic event

• Dropped fresh fuel assembly

• Misplaced fuel assembly

• Misplacement of Cask Area Rack Past industry experience has shown the potential for a multiple misload accident to varying degrees. Tilis is discussed further in Section 5.7.2.

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-1 5 RESULTS AND CONCLUSIONS This section documents the final storage results of the Turkey Point Units 3 & 4 Spent Fuel Pool and New Fuel Storage Rack criticality safety analysis. Included in this section are the burnup requirements for the fuel storage arrays documented in this analysis and IFBA requirements for Category I-2 fuel. The Area of Applicability (AoA) of the criticality code validation suite is discussed in APPENDIX A.

Assembly storage in the SFP is controlled through the storage arrays defined in Section 4.2.1. An array can only be populated by assemblies of the fuel category defined in the array definition or a lower reactivity fuel category (see Table 4-11).

5.1 RESULTS APPLICABLE TO ALL CRITICALITY FUEL DESIGNS Fresh fuel assembly IFBA requirements (Fuel Category I-2) as well as sample IFBA requirements are given in Equation 5-1 and Table 5-1, respectively. Fuel Category I-1 and I-2 assembly storage is not differentiated by criticality fuel design, while considering the following:

• Fuel assemblies have unrestricted storage in the Cask Area Rack.

• Fuel Category I-1 does not require burnup or fresh IFBA for storage.

• Fuel Category I-2 assembly storage requirements require that they must have not been operated in the reactor and the IFBA loading must exceed the minimum IFBA (# rods per assembly) given by the IFBA requirements equation (Equation 5-1).

• The minimum IFBA length of 122 inches (centered).

for .

Minimum IFBA = Equation 5-1

- 22.222 2 + 272.22 - 711.96 for 3.78 < 5.00 Where En is enrichment in wt.%.

Table 5-1 IFBA Requirements for Fuel Category I-2 Enrichment (wt.% 235U) Minimum Required Number of IFBA Pins En. 3.78 0 3.78 < En. 3.90 16 3.90 < En. 4.10 32 4.10 < En. 4.30 48 4.30 < En. 4.50 64 4.50 < En. 4.75 80 4.75 < En. 4.95 92 4.95 < En. 5.00 100 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-2 A sensitivity study of reduced boral areal density in the Cask Area Rack was performed with the following results:

[

]a,c As a result, storage with areal density as low as 0.0160 g/cm2 is considered acceptable.

5.2 STORAGE REQUIREMENTS Fuel Category I-1 does not require burnup or IFBA credit. All other Fuel Category requirements are given in Section 5.2.1. Sections 5.2.2, 5.2.3 and 5.2.4 contain sample evaluated burnup limits for Criticality Fuel Design 1, 2, and 3, respectively.

5.2.1 Curve Fitting Coefficients for Minimum Burnup and IFBA Requirements For all Fuel Categories except I-1 and I-2, an equation specifying the minimum required burnup as a function of the initial enrichment and post-irradiation cooling time is developed. The uncertainty in the burnup is included in the determination of the minimum burnup requirement and so it is appropriate to use the nominal burnup for comparing to the minimum required burnup determined from the loading curves. The burnup requirements are established as 3rd degree polynomial functions in the form of:

Bu = (A1 + A2*En + A3*En2 + A4*En3)

• exp [ - (A5 + A6*En + A7*En2 + A8*En3)*Ct ] + A9 + A10*En +

A11*En2 + A12*En3 where:

Bu = Minimum required assembly average burnup (GWd/MTU)

En = Initial 235U Enrichment (wt%)

Ct = Post Irradiation Cooling Time (years)

Ai = Fitting Coefficients (see Table 5-2, Table 5-3 and Table 5-4) i = Coefficient index number Separate functional relationships are developed for Criticality Fuel Design 1, 2 and 3. Note that for blanketed assemblies, the enrichment to be used in the loading curve equation is the enrichment of the axial section between the blanket material (the enrichment of the axial blankets is excluded when determining the assembly enrichment for application of the loading curve).

Since the loading curves are exponentials in cooling time, any cooling time between 15 and 25 years is applicable for Criticality Fuel Design 1 and between 0 and 25 years for Criticality Fuel Designs 2 and 3.

No decay timer greater than 25 years can be credited. The loading curves are valid for any enrichment between the Min. Enrich. and 4.0 wt.% for Criticality Fuel Design 1 and the Min. Enrich. and 5.0 wt.%

for Criticality Fuel Designs 2 and 3. Coefficients for loading curves for Criticality Fuel Design 1, Criticality Fuel Design 2 and Criticality Fuel Design 3 are given in Table 5-2, Table 5-3 and Table 5-4, respectively.

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-3 Table 5-2 CFD 1 - Coefficients to Calculate the Minimum Required Fuel Assembly Burnup (Bu) as a Function of Enrichment (En) and Cooling Time (Ct)

Fuel Category Coeff. I-3 I-4 II-1 II-2 II-3 II-4 II-5 II-6 A1 46.1221 -15.5280 -2.0590 26.4195 -279.3938 -3.7782 -29.0518 -29.0518 A2 -51.4825 13.5960 -2.7964 -23.6884 502.6296 0.7172 38.3795 38.3795 A3 18.4391 -3.4175 3.0982 6.8587 -295.7499 2.1165 -13.3538 -13.3538 A4 -2.0048 0.3637 -0.4715 -0.4980 57.1661 -0.3342 1.6937 1.6937 A5 -0.4998 -1.0368 0.2161 -1.4442 -1.1906 0.1433 -0.4574 -0.4574 A6 0.3474 1.3335 -0.3773 1.6753 1.2161 -0.1589 0.5477 0.5477 A7 -0.0487 -0.4940 0.1893 -0.5777 -0.3067 0.0725 -0.1803 -0.1803 A8 0.0000 0.0574 -0.0265 0.0632 0.0251 -0.0095 0.0184 0.0184 A9 -38.3233 -96.9847 6.7162 -96.0974 -37.9204 -26.9895 -36.7528 -36.7528 A10 24.6155 94.9777 -18.9681 92.2715 31.3948 23.9367 38.4104 38.4104 A11 -3.5675 -28.3931 10.8797 -25.2863 -4.7926 -2.6264 -5.8631 -5.8631 A12 0.3160 3.0898 -1.2782 2.5516 0.3281 0.1421 0.2201 0.2201 Min.

2.00 1.80 1.75 1.55 1.50 1.30 1.15 1.15 Enrich.

Notes:

1. All relevant uncertainties are explicitly included in the criticality analysis. For instance, no additional allowance for burnup uncertainty or enrichment uncertainty is required. For a fuel assembly to meet the requirements of a Fuel Category, the assembly burnup must exceed the minimum burnup (GWd/MTU) given by the curve fit for the assembly cooling time and initial enrichment. The specific minimum burnup required for each fuel assembly is calculated from the following equation. The equation is applicable at enrichments greater than or equal to the value shown as Minimum Enrichment.

Bu = (A1 + A2*En + A3*En2 + A4*En3)

• exp [ - (A5 + A6*En + A7*En2 + A8*En3)*Ct ] + A9 + A10*En +

A11*En2 + A12*En3

2. Initial enrichment, En, is the nominal 235U enrichment up to 4.0 wt.%. Decay (cooling) time credit of 15 years may be used for enrichments less than 2.0 wt.%. Decay (cooling) time credit between 15 and 25 years, inclusive, may be used for any enrichment between 2.0 and 4.0 wt.%, inclusive.

3. Cooling time, Ct, is in years. Any cooling time between 15 years and 25 years may be used. An assembly with a cooling time greater than 25 years must use 25 years.

4. This table applies only for pre-EPU non-blanketed fuel assemblies. If a non-blanketed assembly is depleted at EPU conditions, none of the burnup accrued at EPU conditions can be credited (i.e., only burnup accrued at pre-EPU conditions may be used as burnup credit).

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-4 Table 5-3 CFD 2 - Coefficients to Calculate the Minimum Required Fuel Assembly Burnup (Bu) as a Function of Enrichment (En) and Cooling Time (Ct)

Fuel Category Coeff. I-3 I-4 II-1 II-2 II-3 II-4 II-5 II-6 A1 -14.0214 0.7356 -10.3764 0.3023 -13.6425 -1.9201 -15.6064 16.2892 A2 11.4137 -1.1927 7.6199 -3.1468 13.5164 2.9502 16.3820 -17.6207 A3 -2.7518 1.4318 -1.2005 2.3278 -2.5923 0.3686 -3.6279 7.2596 A4 0.2743 -0.1832 0.0789 -0.2523 0.1973 -0.0636 0.3114 -0.7399 A5 2.6169 -0.0485 4.8088 0.2364 -0.1211 -0.3267 -0.2816 -0.4164 A6 -2.1487 0.0236 -3.8345 -0.0738 0.1969 0.3766 0.3303 0.5335 A7 0.5878 0.0034 1.0085 -0.0001 -0.0571 -0.1090 -0.0953 -0.1669 A8 -0.0522 -0.0004 -0.0863 0.0016 0.0050 0.0099 0.0087 0.0160 A9 -27.8139 -51.8296 -29.1782 -57.7979 -41.6737 -51.9529 -40.5392 -67.4031 A10 15.7630 41.0704 21.6958 55.4896 42.2351 52.1289 41.5363 74.8527 A11 -0.7370 -8.3986 -3.2089 -13.5089 -8.9287 -11.9184 -8.8545 -19.0424 A12 -0.0324 0.7265 0.2488 1.2360 0.7680 1.0595 0.7866 1.7507 Min 2.00 1.75 1.75 1.55 1.35 1.30 1.30 1.15 Enrich.

Notes:

1. All relevant uncertainties are explicitly included in the criticality analysis. No additional allowance for burnup uncertainty or enrichment uncertainty is required. For a fuel assembly to meet the requirements of a Fuel Category, the assembly burnup must exceed the minimum burnup (GWd/MTU) given by the curve fit for the assembly cooling time and initial enrichment. The specific minimum burnup required for each fuel assembly is calculated from the following equation. The equation is applicable at enrichments greater than or equal to the value shown as Minimum Enrichment.

Bu = (A1 + A2*En + A3*En2 + A4*En3)

• exp [ - (A5 + A6*En + A7*En2 + A8*En3)*Ct ] + A9 + A10*En +

A11*En2 + A12*En3

2. Initial enrichment, En, is the nominal 235U enrichment up to 5.0 wt.%. Axial blanket material is not considered when determining enrichment. No decay (cooling) time credit may be used for enrichments less than 2.0 wt.%. Decay (cooling) time credit between 0 and 25 years, inclusive, may be used for any enrichment between 2.0 and 5.0 wt.%, inclusive.

3. Cooling time, Ct, is in years. Any cooling time between 0 years and 25 years may be used. An assembly with a cooling time greater than 25 years must use 25 years.

4. Category I-1 is fresh unburned fuel up to 5.0 wt% 235U enrichment.

5. Category I-2 is fresh unburned fuel that obeys the IFBA requirements in Table 5-1.

6. This table applies only for assemblies with a blanket enrichment 2.6 wt% 235U.

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-5 Table 5-4 CFD 3 - Coefficients to Calculate the Minimum Required Fuel Assembly Burnup (Bu) as a Function of Enrichment (En) and Cooling Time (Ct)

Fuel Category Coeff. I-3 I-4 II-1 II-2 II-3 II-4 II-5 II-6 A1 32.2479 -4.1991 12.9596 -8.7984 1.2361 -13.6999 -4.4636 16.9460 A2 -32.5873 0.5751 -16.0005 17.5883 3.9352 13.5880 4.4226 -16.9514 A3 10.8045 1.2741 6.3237 -6.8331 -1.1864 -2.6470 0.3955 6.7299 A4 -1.0774 -0.1682 -0.6838 0.8117 0.1753 0.2090 -0.0894 -0.6660 A5 -0.9953 -0.9249 -0.5872 0.0832 0.0667 0.2213 -0.2197 -0.4412 A6 0.9362 0.8428 0.5836 -0.1491 -0.1430 -0.1129 0.2649 0.5695 A7 -0.2713 -0.2310 -0.1721 0.0770 0.0840 0.0290 -0.0800 -0.1805 A8 0.0260 0.0205 0.0169 -0.0095 -0.0112 -0.0025 0.0078 0.0175 A9 -55.7079 -31.2188 -30.7329 -33.6356 -42.2030 -34.7146 -53.7542 -64.6698 A10 40.9920 22.8793 22.0019 18.4614 34.1725 34.4020 56.0845 70.4969 A11 -8.4183 -2.8703 -3.2299 0.7440 -4.6731 -6.5830 -13.3110 -17.5951 A12 0.7732 0.1971 0.2932 -0.2665 0.2560 0.6009 1.2772 1.6628 Min 2.0 1.75 1.75 1.55 1.35 1.30 1.30 1.15 Enrich.

Notes:

1. All relevant uncertainties are explicitly included in the criticality analysis. No additional allowance for burnup uncertainty or enrichment uncertainty is required. For a fuel assembly to meet the requirements of a Fuel Category, the assembly burnup must exceed the minimum burnup (GWd/MTU) given by the curve fit for the assembly cooling time and initial enrichment. The specific minimum burnup required for each fuel assembly is calculated from the following equation. The equation is applicable at enrichments greater than or equal to the value shown as Minimum Enrichment.

Bu = (A1 + A2*En + A3*En2 + A4*En3)

• exp [ - (A5 + A6*En + A7*En2 + A8*En3)*Ct ] + A9 + A10*En +

A11*En2 + A12*En3

2. Initial enrichment, En, is the nominal 235U enrichment up to 5.0 wt.%. Axial blanket material is not considered when determining enrichment. No decay (cooling) time credit may be used for enrichments less than 2.0 wt.%. Decay (cooling) time credit between 0 and 25 years, inclusive, may be used for any enrichment between 2.0 and 5.0 wt.%, inclusive.

3. Cooling time, Ct, is in years. Any cooling time between 0 years and 25 years may be used. An assembly with a cooling time greater than 25 years must use 25 years.

4. Category I-1 is fresh unburned fuel up to 5.0 wt% 235U enrichment.

5. Category I-2 is fresh unburned fuel that obeys the IFBA requirements from Table 5-1.

6. This table applies only for all unblanketed fuel assemblies.

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-6 5.2.2 Criticality Fuel Design 1 Sample evaluated burnup limits given in Table 5-5 through Table 5-12. Note that depending on rounding, sample coefficients may differ in the last decimal place from that obtained from the coefficients.

Table 5-5 CFD 1 Fuel Category I-3 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 2.0 3.0 4.0 15 0.04 12.68 24.60 20 0.04 12.38 24.04 25 0.04 12.21 23.72 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-6 CFD 1 Fuel Category I-4 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.80 2.0 3.0 4.0 15 0 4.28 17.41 29.12 20 4.21 16.96 28.34 25 4.17 16.63 27.79 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-7 Table 5-7 CFD 1 Fuel Category II-1 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.75 2.0 3.0 4.0 15 0 2.95 14.81 26.50 20 2.92 14.32 25.89 25 2.89 13.99 25.39 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-8 CFD 1 Fuel Category II-2 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.55 2.0 3.0 4.0 15 0 8.26 22.99 35.67 20 8.04 22.65 34.66 25 7.91 22.43 33.91 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-9 CFD 1 Fuel Category II-3 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.50 2.0 3.0 4.0 15 0.84 8.33 23.39 34.42 20 8.33 23.05 32.35 25 8.32 23.00 32.03 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-8 Table 5-10 CFD 1 Fuel Category II-4 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.30 2.0 3.0 4.0 15 0 13.42 28.30 40.55 20 13.08 27.42 39.33 25 12.80 26.78 38.43 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-11 CFD 1 Fuel Category II-5 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.15 2.0 3.0 4.0 15 0 21.38 36.40 50.13 20 20.56 35.17 48.54 25 19.96 34.26 47.14 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-12 CFD 1 Fuel Category II-6 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.15 2.0 3.0 4.0 15 0 21.38 36.40 50.13 20 20.56 35.17 48.54 25 19.96 34.26 47.14 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-9 5.2.3 Criticality Fuel Design 2 Sample evaluated burnup limits given in Table 5-13 through Table 5-20. Note that depending on rounding, sample coefficients may differ in the last decimal place from that obtained from the coefficients.

Table 5-13 CFD 2 Fuel Category I-3 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 2.0 3.0 4.0 5.0 0 0.50 14.83 26.53 37.07 2.5 0.50 14.48 25.53 36.19 5 0.50 14.18 24.73 35.40 10 0.50 13.67 23.55 34.06 15 0.50 13.29 22.79 32.98 20 0.50 12.99 22.29 32.11 25 0.50 12.75 21.97 31.41 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-14 CFD 2 Fuel Category I-4 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.75 2.0 3.0 4.0 5.0 0 0.27 5.14 20.51 31.72 42.04 2.5 5.08 20.00 30.50 40.27 5 5.02 19.54 29.49 38.92 10 4.91 18.76 27.96 37.07 15 4.81 18.12 26.90 35.97 20 4.71 17.61 26.18 35.32 25 4.61 17.19 25.67 34.93 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-10 Table 5-15 CFD 2 Fuel Category II-1 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.75 2.0 3.0 4.0 5.0 0 0.00 4.06 17.56 28.13 37.75 2.5 3.58 17.09 27.01 36.68 5 3.43 16.69 26.10 35.75 10 3.37 16.02 24.76 34.28 15 3.37 15.50 23.88 33.20 20 3.37 15.10 23.30 32.40 25 3.37 14.79 22.92 31.81 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-16 CFD 2 Fuel Category II-2 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.55 2.0 3.0 4.0 5.0 0 0.44 10.34 25.46 35.93 47.65 2.5 10.04 24.80 35.06 45.97 5 9.82 24.22 34.27 44.54 10 9.51 23.28 32.91 42.29 15 9.32 22.58 31.82 40.67 20 9.21 22.05 30.93 39.49 25 9.14 21.66 30.21 38.64 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-11 Table 5-17 CFD 2 Fuel Category II-3 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay 1.35 2.0 3.0 4.0 5.0 Time (yr.)

0 1.33 17.83 34.31 45.13 56.08 2.5 16.95 32.51 43.20 54.13 5 16.24 31.07 41.60 52.46 10 15.21 29.00 39.14 49.79 15 14.52 27.69 37.44 47.82 20 14.08 26.86 36.25 46.37 25 13.78 26.33 35.43 45.29 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-18 CFD 2 Fuel Category II-4 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.30 2.0 3.0 4.0 5.0 0 0.40 18.05 34.31 45.38 57.27 2.5 17.26 32.60 43.52 55.04 5 16.60 31.23 41.96 53.16 10 15.57 29.26 39.53 50.25 15 14.85 28.01 37.82 48.19 20 14.33 27.20 36.60 46.73 25 13.97 26.69 35.75 45.69 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

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Westinghouse Non-Proprietary Class 3 5-12 Table 5-19 CFD 2 Fuel Category II-5 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.30 2.0 3.0 4.0 5.0 0 0.47 18.55 34.91 46.08 58.64 2.5 17.75 33.11 44.15 56.15 5 17.08 31.65 42.53 54.10 10 16.03 29.53 40.05 50.98 15 15.28 28.16 38.31 48.83 20 14.74 27.27 37.10 47.35 25 14.36 26.69 36.25 46.34 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-20 CFD 2 Fuel Category II-6 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.15 2.0 3.0 4.0 5.0 0 0.66 24.31 41.83 53.98 66.83 2.5 23.30 39.65 51.60 63.76 5 22.53 38.01 49.61 61.24 10 21.51 35.85 46.54 57.47 15 20.93 34.63 44.39 54.92 20 20.59 33.94 42.89 53.21 25 20.40 33.55 41.84 52.05 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

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Westinghouse Non-Proprietary Class 3 5-13 5.2.4 Criticality Fuel Design 3 Sample evaluated burnup limits for Criticality Fuel Design 3 are given in Table 5-21 through Table 5-28.

Note that depending on rounding, sample coefficients may differ in the last decimal place from that obtained from the coefficients.

Table 5-21 CFD 3 Fuel Category I-3 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 2.0 3.0 4.0 5.0 0 0.46 15.02 28.87 40.19 2.5 0.46 14.57 27.90 38.68 5 0.46 14.20 27.10 37.65 10 0.46 13.64 25.86 36.47 15 0.46 13.25 25.01 35.92 20 0.46 12.98 24.41 35.67 25 0.46 12.80 24.00 35.55 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-22 CFD 3 Fuel Category I-4 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.75 2.0 3.0 4.0 5.0 0 0.89 5.34 21.36 34.71 45.56 2.5 5.34 20.57 33.60 43.91 5 5.33 19.92 32.64 42.54 10 5.33 18.95 31.13 40.48 15 5.33 18.29 30.02 39.07 20 5.33 17.84 29.21 38.11 25 5.33 17.54 28.61 37.46 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

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Westinghouse Non-Proprietary Class 3 5-14 Table 5-23 CFD 3 Fuel Category II-1 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.75 2.0 3.0 4.0 5.0 0 0.11 3.48 17.53 30.73 40.75 2.5 3.43 16.97 29.64 39.10 5 3.38 16.51 28.74 37.94 10 3.30 15.80 27.37 36.54 15 3.22 15.30 26.42 35.85 20 3.16 14.94 25.78 35.51 25 3.10 14.70 25.33 35.34 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-24 CFD 3 Fuel Category II-2 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.55 2.0 3.0 4.0 5.0 0 0.84 9.67 25.63 39.23 53.74 2.5 9.44 24.91 38.22 52.06 5 9.22 24.30 37.46 50.67 10 8.80 23.37 36.44 48.57 15 8.42 22.73 35.85 47.12 20 8.07 22.28 35.51 46.13 25 7.75 21.97 35.32 45.45 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

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Westinghouse Non-Proprietary Class 3 5-15 Table 5-25 CFD 3 Fuel Category II-3 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.35 2.0 3.0 4.0 5.0 0 0.86 15.26 32.27 45.32 57.00 2.5 14.88 30.82 42.89 55.40 5 14.53 29.66 41.11 54.00 10 13.89 28.02 38.82 51.68 15 13.34 26.97 37.58 49.89 20 12.85 26.31 36.91 48.51 25 12.42 25.89 36.54 47.45 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-26 CFD 3 Fuel Category II-4 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.30 2.0 3.0 4.0 5.0 0 0.15 17.12 34.35 47.70 62.02 2.5 16.19 32.81 45.73 59.77 5 15.45 31.54 44.10 57.87 10 14.39 29.62 41.61 54.93 15 13.72 28.31 39.89 52.85 20 13.30 27.41 38.70 51.38 25 13.03 26.79 37.87 50.34 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

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Westinghouse Non-Proprietary Class 3 5-16 Table 5-27 CFD 3 Fuel Category II-5 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.30 2.0 3.0 4.0 5.0 0 1.22 20.64 39.13 53.18 69.91 2.5 19.99 37.63 51.28 66.95 5 19.43 36.35 49.64 64.52 10 18.49 34.35 47.01 60.91 15 17.78 32.90 45.05 58.49 20 17.23 31.86 43.59 56.86 25 16.80 31.11 42.51 55.77 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

Table 5-28 CFD 3 Fuel Category II-6 Burnup Requirements (GWd/MTU)

Maximum Initial Enrichment, wt.% 235U Decay Time (yr.) 1.15 2.0 3.0 4.0 5.0 0 1.00 23.88 42.04 56.41 72.97 2.5 22.72 39.87 54.17 69.81 5 21.84 38.24 52.28 67.23 10 20.70 36.10 49.35 63.41 15 20.06 34.90 47.27 60.86 20 19.70 34.23 45.80 59.17 25 19.50 33.85 44.76 58.04 Note:

This table is included as an example, the burnup requirements will be calculated using the coefficients provided.

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Westinghouse Non-Proprietary Class 3 5-17 5.3 FUEL ROD STORAGE BASKET The Fuel Rod Storage Basket (FRSB) modeled in this analysis is an 8x8 array of stainless steel tubes with the three tubes closest to each corner of the array omitted, i.e., the total number of tubes is 8x8 - 4x3 = 52.

Specifications for the FRSB can be found in Section 3.4.4.

It is conservatively assumed that all the tubes in the basket are filled with fresh 5.0 wt.% 235U fuel rods.

The evaluation is performed by evaluating the reactivity impact of substituting fuel rod baskets in place of already analyzed fuel assemblies in the storage arrays. Because the Metamic inserts are mounted to the top of the assembly it is not possible to place a fuel rod basket in a location requiring an insert. Therefore, the number of storage cells modeled as containing fuel rod baskets is varied from 0 (base case) to the total without Metamic inserts. Models were analyzed for Region I and Region II Fuel Categories with fresh and burned fuel. All burned models were of Criticality Fuel Design 3. The results given in Table 5-29 and Table 5-30 show that replacing an analyzed assembly with a fuel rod basket results in a reactivity decrease for all configurations. In Table 5-30, adjacent and diagonal denote if the assemblies in the analyzed bounding configuration contain Metamic inserts which are adjacent to or diagonal to one another when either is allowed in the storage configuration. Permutations of the same number of Fuel Rod Storage Baskets are included. Therefore, a Fuel Rod Storage Basket is acceptable in any cell without Metamic inserts that is not designated as an empty location for the storage configuration. Note that while assessments were performed with Criticality Fuel Design 3, the same trend will be evident with Criticality Fuel Designs 1 and 2.

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Westinghouse Non-Proprietary Class 3 5-18 Table 5-29 keff With and Without the Fuel Rod Basket in Region I Storage Configurations (Assessments Performed With Criticality Fuel Design 3)

Number of Baskets Storage Array Fuel Assembly Description in 2x2 array k-eff sigma 0 0.93832 0.00012 I-A 5.00 wt.% 235U Fresh 1 0.90806 0.00012 2 0.63893 0.00010 0 0.94890 0.00009 1 0.89845 0.00009 2 0.85345 0.00009 1.75 wt.% 235U Fresh 2 0.82926 0.00009 3 0.78991 0.00010 4 0.72136 0.00010 I-B 0 0.93576 0.00009 1 0.88412 0.00010 5.00 wt.% 235U, 46 GWd/MTU, 0 2 0.83815 0.00010 yr cooling 2 0.81444 0.00009 3 0.77494 0.00010 4 0.72136 0.00010 5.00 wt.% 235U, 0 0.94209 0.00006 40 GWd/MTU (Category I-4), 1 0.88834 0.00006 80 IFBA (Category I-2), 1 0.88430 0.00006 I-C 0 yr cooling 2 0.81456 0.00006 Nominal Case of one I-2, three I-4 2 0.83521 0.00006 assemblies 3 0.76774 0.00006 0 0.95735 0.00009 1 0.90272 0.00011 1 0.87773 0.00010 2.05 wt.% 235U Fresh 2 0.82122 0.00010 2 0.82835 0.00010 3 0.72497 0.00010 I-D 0 0.93519 0.00010 1 0.88037 0.00011 5.00 wt.% 235U, 42 GWd/MTU, 0 1 0.86077 0.00010 yr cooling 2 0.79968 0.00010 2 0.81104 0.00011 3 0.72604 0.00010 Notes:

1.) Isotopics used are all within a burnup step of the actual burnup limit. In many cases they are greater than the burnup limit which is conservative.

2.) Results with the same number of FRSB locations for similar input are a geometric variation of FRSB placement within the storage array (e.g., adjacent vs. diagonal).

3.) The I-C storage configuration model used has a lower reactivity than the model used to set the IFBA requirements with I-2 fuel at 5 wt.% which is conservative.

4.) Configuration I-D utilizes fresh 2.05 wt.% fuel while the maximum fresh enrichment was determined to be 2.0 wt.%. The reduction in reactivity with adding FRSBs will not change trend due to this enrichment difference.

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Westinghouse Non-Proprietary Class 3 5-19 Table 5-30 keff With and Without the Fuel Rod Basket in Region II Storage Configurations Number of Storage Baskets in 2x2 Array Fuel Assembly Description array k-eff sigma II-A 0 0.96252 0.00006 1.75 wt% U-235 Fresh, 0 yr cooling 1 0.89977 0.00010 2 0.83081 0.00010 0 0.95582 0.00006 5.00 wt% U-235, 42 GWd/MTU, 1 0.89330 0.00011 0 yr cooling 2 0.82688 0.00009 II-B 1.35 wt% Fresh II-5 0 0.96622 0.00005 U-235 Fresh, 1.50 wt% Fresh II-3 1 0.92561 0.00018 0 yr cooling, 1.35 wt% Fresh II-5 1 0.92086 0.00005 Adjacent 1.35 wt% Fresh II-5 2 0.86881 0.00006 Adjacent 0 0.95091 0.00005 5.00 wt% U-235, Adjacent 1 0.92089 0.00005 70 GWd/MTU, 0 yr cooling Diagonal 2 0.88450 0.00006 II-C Adjacent 0 0.96031 0.00005 1.30 wt% U-235 Fresh, 0 yr Adjacent 1 0.91482 0.00005 cooling Diagonal 2 0.87387 0.00005 Adjacent 0 0.95427 0.00005 5.00 wt% U-235, 62 Adjacent 1 0.91382 0.00005 GWd/MTU, 0 yr cooling Diagonal 2 0.87143 0.00006 II-D 0 0.96308 0.00005 1.55 wt% U-235 Fresh, 0 yr cooling 1 0.90350 0.00009 5.00 wt% U-235, 54 GWd/MTU, 0 0.95279 0.00006 0 yr cooling 1 0.90523 0.00009 II-E 0 0.96509 0.00005 1 0.93122 0.00005 1 0.92912 0.00005 1.15 wt% U-235 Fresh, 0 yr cooling 2 0.89070 0.00006 2 0.90078 0.00006 3 0.85588 0.00007 0 0.94851 0.00006 1 0.91859 0.00006 5.00 wt% U-235, 72 GWd/MTU, 1 0.92033 0.00006 0 yr cooling 2 0.88033 0.00006 2 0.89400 0.00006 3 0.85014 0.00006 Notes:

1.) Isotopics used are all within a burnup step of the actual burnup limit. In many cases they are greater than the burnup limit which is conservative.

2.) Results with the same number of FRSB locations for similar input are a geometric variation of FRSB placement within the storage array (e.g., adjacent vs. diagonal).

3.) For configurations II-B and II-C, only a selection of cases are presented as the number of permutations is large considering the insert location and possible FRSB locations. Reactivity is reduced in all cases.

4.) Configuration II-B fresh case examples contain greater enrichment II-5 and II-3 assemblies than the final determined max fresh enrichments. However, Configuration II-C contains the same geometric layout with all 1.30 wt.% fresh assemblies and is conservative, WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-20 S.4 ALLOWABLE INTERFACE CONFIGURATIONS This section illustrates the allowable interface configurations.

S.4.1 Within Region Interfaces Within region interfaces are acceptable provided the following:

• Each 2x2 array in the Region I or Region II areas of the pool must match one of the analyzed arrays.

• In this context, the term "match" means that the anay has at least the required number of inserts, full length RCCAs or empty cells and that the assemblies have at least the required bumup for the appropriate Fuel Category. .

S.4.2 Region I to Region II Interface Note that in all Region adjacent cells, the placement of an insert/RCCA in an unshaded cell is conservative and acceptable. Also. all interface schematics are representative, Region I and Region II cells do not perfectly align as discussed For Region II assemblies. there is no restriction based on which assembly is in the constructed vs. developed cells.

Anay I-A - Region II lott>dares Storage Anay I-A (Region I) contains checker-boarded fresh fuel of Category 1-1 . Figure 5-1 illustrates the allowable Anay I-A-Region II interfaces. The shaded cells contain an insert and X indicates an empty (water filled) cell. .Anay I-A shall not interface with Array 11-B or Array 11-D.

Arrnl-A 1-AAn-aY Arra~* I-A X 1-1 X 1-1 X 1-1 X 1-1 X I-1 X 1-1 1-1 X 1-1 X 1-1 X I-1 X 1-1 X I-1 X 11-1 X 11-1 X . 11-4 11-4 11-4 11-4 11-6 11-6 11-6 11-6 Il-1 11-1 11-1 11- 1 11-4 11-4 11-4 ll-4 11-6 11-6 ll-6 11-6 Array II-A Anay 11-C An-ay 11-E Figure 5-1 Allowable Anay I-A Region II Interfaces Array 1-B-Rt>gion II Interfaces Region I Anay 1-B contains four burned assemblies with no inserts (Fuel Category 1-4). Figure 5-2 illustrates the allowable Array I-B Region II interfaces. The shaded cells contain an insert and X indicates an empty (water filled) cell. Note that any munber of Catego1y 1-4 fuel assemblies can be substituted with a fresh Category I-2 fuel with an RCC A and IFBA rods. There is no rest1iction on the placement of Catego1y 1-2 fuel at the inte1face.

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Westinghouse Non-Proprietary Class 3 5-21 Arra)* 1-B Arra ' 1B

- Arra,*1-B Arrayl-B Arravl-B 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 11-1 X 11-1 X Il-3 Il-5 Il-3 Il-5 11-4 Il-4 Il-4 ll-4 Il-2 Il-2 ll-2 ll-2 Il-6 Il-6 11-6 11-6 ll-1 ll-1 ll-1 Il-1 Il-5 Il-3 Il-5 Il-3 11-4 Il-4 Il-4 ll-4 Il-2 Il-2 ll-2 11-2 Il-6 Il-6 ll-6 Il-6 Arrayll-A Arrayll-B Array Il-C Arrayll-D Array Il-E Figm*e 5-2 Allowable Array 1-B- Region II lntf'rfaces Array 1-D - Region II Intf'11aces Region I Array I-D consists of fuel assemblies stored in a 2x2 array with one of the fuel assemblies containing a full length RCCA (Fuel Category I-3). Figure 5-3 illustrates the allowable Array I-D Region II interfaces. The shaded cells either contain an insert (Il-1) or a RCCA (1-3) and X indicates an empty (water filled) cell.

Arra1* 1-D Arravl-D Arral' 1-D Arravl-D 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 Il-1 X Il-1 X Il-3 Il-5 Il-3 Il-5 D-3 Il-5 Il-3 11-S 11-3 11-S 11-3 11-S 11-4 Il-4 Il-4 11-4 Il-1 Il-1 Il-1 Il-1 Il-5 Il-3 Il-5 11-3 11-S Il-3 Il-S 11-3 11-5 11-3 11-5 Il-3 Il-4 Il-4 Il-4 Il-4 Array II-A Array 11-B Arrayll-B Arra~* 11-B Array ll-C Ai-ravl-D Ai-rayl-D Arrnl-D A1Tayl-D Arra,* 1-D 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 1-3 Il-4 11-4 Il-4 Il-4 Il-4 11-4 Il-4 Il-4 Il-2 Il-2 Il-2 11-2 Il-2 11-2 11-2 11-2 11-6 11-6 11-6 11-6 Il-4 11-4 11-4 11-4 11-4 Il-4 11-4 Il-4 11-2 11-2 Il-2 11-2 11-2 11-2 Il-2 Il-2 11-6 11-6 Il-6 11-6 An-ay Il-C Arny Il-D Array 11-D Arra~* 11-E Figurf' 5-3 Allowablf' Array I-D Region II Intf'rfaces WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-22 Notes for Figure 5-1, Figure 5-2 and Figure 5-3:

1. In all arrays, an assembly of lower reactivity can replace an assembly of higher reactivity.

2. Shaded cells indicate that the cell contains a Metamic insert or the fuel assembly contains a full length RCCA.

3. X indicates an empty (water-filled) cell.

4. The figures illustrate the least conservative allowable arrays in regard to Metamic placement.

5. Region I and II storage cells do not necessarily align across the interface as shown in the figure.

There are no restrictions associated with cell alignment across the interface.

6. If no fuel is stored adjacent to Region II in Region I, then the interface restrictions are not applicable.

7. Array I-A shall not interface with Array II-B or II-D.

8. Figure 5-1 through Figure 5-3 are applicable only to the Region I - Region II interface. There are no restrictions for the interfaces with the Cask Area Rack.

9. An empty (water-filled) cell may be substituted for any fuel containing cell in all storage arrays.

10. In all region adjacent cells, the placement of an insert/RCCA in an unshaded cell is conservative and acceptable.

What follows are the results of the Region I-Region II interface analysis. As previously stated, the biases and uncertainties for the interface can either be taken from the maximum of the individual storage arrays of both sides of the interface or can be recalculated for the interface configuration. For all acceptable interfaces in this analysis, biases and uncertainties were not recalculated and the interfaces shown are acceptable using the maximum biases and uncertainties from the individual storage arrays on both sides of the interface.

Table 5-31 shows the keff values (including biases and uncertainties) calculated for the allowable interface configurations shown in Figure 5-1 through Figure 5-3.

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Westinghouse Non-Proprietary Class 3 5-23 Table 5-31 Results for the Region I - Region II Interface Calculations1 Minimum Interface Interface Region I Array Region II Array keff + 2 Region USL II-A 0.95924 0.96275 I-A II-C 0.95357 0.95468 II-E2 0.94889 0.94876 II-A 0.87587 0.94077 II-B 0.93872 0.94077 I-B II-C 0.93921 0.94077 II-D 0.91984 0.94077 II-E 0.91790 0.94077 II-A 0.85742 0.93412 II-B 0.89041 0.93412 I-D II-C 0.93379 0.93412 II-D 0.93240 0.93412 II-E 0.93037 0.93412 Notes:

1. Interface keff from the maximum reactivity acceptable case except where noted.

2. The resultant keff of this case is 0.94874, which is acceptable prior to added uncertainty.

With the additional conservatism of the partial (~50%) removal of the Metamic insert, this interface is judged acceptable.

5.4.3 Cask Area Rack Interfaces The Cask Area Rack has sufficient absorber panels that the maximum keff is much less than the limiting keff in Region I or Region II. Furthermore, the Cask Area Rack has Boral panels on the exterior of the rack so there is no local increase in reactivity at the rack interface. Consequently, there are no interface loading constraints on the Cask Area Rack/Region I or Cask Area Rack/Region II interface.

5.5 OTHER NORMAL STORAGE CONDITIONS While the primary purpose of the spent fuel pool is storage of new and spent fuel assemblies, many other activities occur in the pool. The criticality safety analysis is intended to cover the following SFP activities in addition to normal fuel handling and storage activities.

1. Ultrasonic Testing of fuel assembly to determine leaking rods:

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Westinghouse Non-Proprietary Class 3 5-24 The rack cell location to perform ultrasonic testing must be selected based on allowed SFP configurations for the bounding fuel design. This configuration involves raising and lowering the assembly within the rack cell while the inspection is being performed. This is similar to when the assembly is being loaded or unloaded from the rack. Axially offsetting one assembly from the others will reduce the reactivity of the system by reducing the neutronic interaction between assemblies. This configuration is bounded by the analysis.

2. Fuel assembly raised on pedestal or placed in new fuel elevator during fuel inspection (failed and healthy fuel inspections):

No special consideration needs to be made for the new fuel elevator; a single isolated assembly is bounded by the criticality safety analysis. A single assembly will be less reactive than the analyzed storage array I-A.

The fuel assembly must meet allowed SFP configurations for the rack location. The presence of the pedestal will raise the assembly up higher than the surrounding assemblies, this is not unlike when an assembly is inserted or removed from a cell. Axially offsetting one assembly from the others will reduce the reactivity of the system by reducing the neutronic interaction between assemblies. This configuration is bounded by the criticality safety analysis.

3. Reconstitution of fuel assembly:

The removal of a fuel rod will change the moderator to fuel ratio of the assembly and could potentially cause a small increase in reactivity. However, the fuel assembly undergoing reconstitution will be kept at least one cell pitch from other fuel in the pool while the rod is removed. This will serve to isolate the fuel assembly and a single isolated assembly is bounded by the criticality safety analysis.

The lattice configuration with a stainless steel replacement rod is less reactive than the original lattice. Only one fuel rod should be replaced at a time.

4. Fuel rod inspection (eddy current testing, visuals, etc.):

This configuration involves a fuel assembly being placed on a pedestal, a fuel rod being removed from the assembly, inspected, then returned to the assembly or placed in damaged rod storage.

The fuel assembly must meet allowed SFP configurations for the rack location. The presence of the pedestal will raise the assembly up higher than the surrounding assemblies, this is not unlike when an assembly is inserted or removed from a cell. Axially offsetting one assembly from the others will reduce the reactivity of the system by reducing the neutronic interaction between assemblies. The removal of a fuel rod will change the moderator to fuel ratio of the assembly and could potentially cause a small increase in reactivity. However, the fuel assembly undergoing inspection will be kept at least one cell pitch from other fuel in the pool while the rod is removed.

This will serve to isolate the fuel assembly and a single isolated assembly is bounded by the criticality safety analysis.

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Westinghouse Non-Proprietary Class 3 5-25 A single fuel rod is bounded by this analysis.

5. Fuel Rod Storage Basket raised on pedestal during fuel inspection to facilitate damaged fuel rod insertion:

The rack cell in which the FRSB is located must meet the requirements of the criticality analysis.

The raising of the fuel rod storage basket will reduce neutronic interaction with surrounding fuel and the resulting reactivity will be the same or lower than the reactivity of the configurations analyzed. The FRSB is analyzed in Section 5.3.

6. Storage of damaged fuel rods; fuel rod inserted in FRSB or fuel assembly guide tubes:

The FRSB is evaluated for fresh 5.0 wt.% fuel, therefore fuel with any nominal initial enrichment less than 5.0 wt.% and any amount of burnup may be stored in the FRSB.

Fuel rods stored in fuel assembly guide tubes lower reactivity by displacing moderator.

This activity is bounded by the criticality safety analysis.

7. Fuel assembly inspection:

During fuel inspection, the fuel assembly will be raised and lowered in the same rack cell or in another SFP location (e.g., transfer canal, cask lay down area).

The fuel assembly must meet allowed SFP configurations for the rack or other location. This activity is bounded by the criticality safety analysis.

8. Ultrasonic testing fuel assembly cleaning:

This is analyzed by the ultrasonic testing vendor. No special consideration is given here.

9. Bottom nozzle inspections:

The fuel assembly is inspected during normal handling evolutions in the refueling cavity, transfer canal, or cask lay down area.

A single isolated assembly is bounded by the criticality safety analysis. A single assembly will be less reactive than the analyzed storage array I-A.

10. Fuel assembly debris removal:

Debris removal is performed away from other fuel assemblies (e.g., transfer canal cask laydown area)

A single isolated assembly is bounded by the criticality safety analysis. A single assembly will be less reactive than the analyzed storage array I-A.

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Westinghouse Non-Proprietary Class 3 5-26

11. Top Nozzle Separation visual inspection:

The fuel assembly is raised four feet and a camera is used to inspect guide tube sleeves.

The fuel assembly must meet allowed SFP configurations for the rack location. This activity is bounded by the criticality safety analysis.

12. Debris/Trash Storage Baskets:

A debris/trash storage basket may not be stored in a cell that is required to be empty by the criticality analysis (e.g., empty cells in configurations I-A and II-A). In each configuration, the debris/trash storage basket will replace a fuel assembly; the debris/trash storage basket contents listed have no significant fissile material and will therefore reduce the reactivity of the configuration relative to the analysis. This activity is bounded by the criticality safety analysis because the storage basket must be placed in a location intended for a fuel assembly.

13. Physically damaged SFP cells (with pre-existing fuel assembly or with no fuel assembly). Cells that are bent or damaged during fuel handling:

There are two possible usages for damaged cells. The cell may be used for storage of an assembly as intended or credited as an empty cell. Storage of fuel in the damaged cell is permissible if the damage is not in the active fuel region. Credit for an empty cell is permissible since the amount of water and steel is maintained relative to the analysis contained herein.

14. Metamic inserts or RCCAs stored in empty rack cell or stored between racks and SFP wall:

The Metamic inserts or RCCAs stored in empty rack cells or stored between racks and the SFP wall may not be credited as part of a configuration. The addition of a neutron absorber relative to the analyzed configuration is acceptable for usage as an empty cell.

15. A single fuel assembly in transit (e.g., refueling canal, fuel upender, or fuel elevator):

No special consideration needs to be made for the refueling canal, fuel upender, or fuel elevator; a single isolated assembly is bounded by the criticality safety analysis. A single assembly will be less reactive than the analyzed storage array I-A.

5.6 RODDED OPERATIONS Significant rodded operation is not covered by this analysis. While standard operation is performed unrodded, it is allowable to operate at hot full power with rods inserted to the power dependent insertion limits. Operating with control rods inserted into the core impacts the assemblies in the rodded locations.

The insertion of a control rod into an assembly during operation has several effects.

In addition to impacting the neutron spectrum, rodded operation can also affect the axial burnup profile of assemblies. Operation with a control rod inserted in an assembly will shift power down, under-depleting the top of the assembly while the control rod is present. Once the control rod has been withdrawn from WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-27 the assembly, power preferentially moves to the under-depleted top of the assembly, and over time the axial burnup profile developed will return to a profile typical of unrodded operation. Therefore, time-in-life before final discharge of an assembly is an important factor in the impact of rodded operation on assembly reactivity.

Reference 17 defines a significant amount of control rod insertion as more than 20 cm into the core.

Turkey Point Units 3 and 4 have not operated at full power with control rods inserted a significant length into the core. Therefore, there is no significant burnup accrued during depletion with rods inserted in the active fuel height, and no need to account for these effects in burnup limits contained within this analysis.

Any assemblies incurring significant rodded operation going forward must not credit the rodded burnup.

While typical operation for Turkey Point Units 3 & 4 is performed unrodded, there is potential to operate at reduced power levels with rods inserted. Short term reduced power operation may be the result of plant equipment issues or economic considerations. Any impact from short term operation at reduced power levels with rods inserted will be negligible. This does not include regularly scheduled flexible power operations.

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Westinghouse Non-Proprietary Class 3 5-28 5.7 SOLUBLE BORON CREDIT Results for soluble boron credit for normal and accident conditions are given here.

5.7.1 Soluble Boron Requirements for Normal Operation The minimum soluble boron concentration to maintain keff < 0.95 for the limiting normal condition including biases, uncertainties, including 50 ppm additional margin is 550 ppm. Results are given in Table 5-32 showing the maximum keff including biases and uncertainties with 500 ppm of soluble boron.

Table 5-32 Results for the Normal Operations with 500 ppm of Soluble Boron KENO Storage Array keff + 2keff + B&U*

I-A 0.87440 I-B/I-C 0.89637 I-D 0.89726 II-A 0.92304 II-B 0.93281 II-C 0.93359 II-D 0.92999 II-E 0.92976

• Includes administrative margin (0.005k).

Significant margin to the limit of 0.95 is available (0.01641 k) but is not determined in terms of ppm soluble boron.

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Westinghouse Non-Proprietary Class 3 5-29 5.7.2 Soluble Boron for Accident Conditions In addition to maintaining keff not to exceed 0.95 during normal operations, soluble boron is used to offset the potential reactivity insertion events in the SFPs. A multiple assembly misload is a postulated accident where assemblies are misloaded in series due to a common cause. [

]a,c Table 5-33 [ ]a,c a,c

• Includes administrative margin (0.005k).

The multiple misload accidents bounds all other accidents listed in Section 4.2.9.

5.7.3 Soluble Boron Requirements Summary Table 5-34 data indicates that 2350 ppm of soluble boron is needed during the most limiting accident analyzed to ensure the Turkey Point Units 3 & 4 SFPs will be less than a keff of 0.95 at a 95 percent probability with 95 percent confidence.

Table 5-34 [ ]a,c Condition Description Required Soluble Boron (ppm)

Normal Operations 550

[ ]a,c 2350 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-30 5.8 NEW FUEL STORAGE RACK The analysis described in the following subsections supports the safe storage of fuel in the New Fuel Storage Rack provided that the fuel meets one of the following conditions:

1. Enriched to 4.25 wt.% 235U or less.

2. Enriched to between 4.25 wt.% 235U and 5.0 wt.% 235U with at least 16 IFBA rods with

[ ]a,c (1.25x) or higher and the IFBA portion of the rod covers at least the 7 central feet of the fuel.

5.8.1 Model Description The SCALE model of the rack is shown in Figure 5-4 and Figure 5-5.

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Westinghouse Non-Proprietary Class 3 5-31 Figure 5-4 New Fuel Storage Rack Model (planar view)

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Westinghouse Non-Proprietary Class 3 5-32 Figure 5-5 New Fuel Storage Rack Model (axial view, concrete thickness not to scale))

The following modeling considerations apply to the New Fuel Storage Rack modeling:

1. UO2 TD of 98.3.

2. [

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-33 5.8.2 Rack Analysis The rack analysis considers both fully flooded and optimal moderation conditions as required by Section 2.1.2. Final results can be seen in Table 5-35.

The results in Table 5-35 indicate acceptance for fuel up to 4.25 wt.% 235U. For enrichments above 4.25 wt.% 235U (nominal), the fuel must contain 16 or more IFBA rods. It is assumed that the IFBA rods have a nominal 10B loading of [ ]a,c Figure 5-6 and Figure 5-7 show the resulting reactivity as a function of moderation (H2O density) for the maximum fresh unpoisoned (4.25 wt.% nominal) and 5.00 wt.% with 16 IFBA representing 4.95 nominal enrichment cases, respectively.

a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 5-34 a,c a.c In sunmiary, the New Fuel Storage Rack Requirements are as follows:

• No rest1ictions up to and including 4.25 wt.% 235U.

• 16 IFBA required for fuel greater than 4.25 wt.% 235 (up to 5.0 wt.% 235 U).

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Westinghouse Non-Proprietary Class 3 6-1 6 LIMITATIONS OF ANALYSIS The following inputs to this analysis will be checked in order to ensure compliance with the criticality safety design basis.

6.1 FUEL LIMITATIONS This analysis is applicable to the Westinghouse 15x15 STD and OFA fuel designs and variations of these designs containing the fuel features found in Table 3-2. Consult Section 3 and 4 for other fuel design limitations.

6.2 OPERATIONAL LIMITATIONS Fuel must be characterized as one of the criticality fuel designs described herein or be stored as fresh fuel.

Core maximum rated thermal power for storage of Criticality Fuel Design 1, 2 and 3 are 2300, 2644 and 2644 MWt, respectively. Consult Section 4.1 for additional operational design limitations. Fuel assemblies that do not meet operational limits and assumptions will be specifically evaluated and classified following the same methodology used in this report.

6.3 SPENT FUEL POOL STORAGE LIMITATIONS

1. Each Metamic insert shall have an areal density greater than or equal to 0.015 10B g/cm2.

2. Each Cask Area Rack Boral panel shall have an areal density greater than or equal to 0.0160 10B g/cm2.

3. The center to center spacing of Region I shall be greater than or equal 10.48 inches, the center to center spacing of Region II shall be greater than or equal to 8.97 inches, and the center to center spacing of the Cask Area Rack shall be greater than or equal to 10.06 for each cell.

Consult Section 4.2 and the additional description herein for any additional limitations.

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Westinghouse Non-Proprietary Class 3 7-1 7 REFERENCES

1. SCALE Code System, ORNL/TM-2005/39, Version 6.2.4, Oak Ridge National Laboratory, Oak Ridge, TN (2020).

2. WCAP-17094-P, Revision 3, Turkey Point Units 3 and 4 New Fuel Storage Rack and Spent Fuel Pool Criticality Analysis, 2011.

3. Code of Federal Regulations, Title 10, Part 50, Section 68, Criticality Accident Requirements.

4. Westinghouse Document WCAP-16045-P-A, Rev. 0, Qualification of the Two-Dimensional Transport Code PARAGON, August 2004.

5. EPRI Report 3002010613, Benchmarks for Quantifying Fuel Reactivity Depletion UncertaintyRevision 1, Adams Number ML18088B397, Electric Power Research Institute, 2017.

6. EPRI Report 3002010614, Utilization of the EPRI Depletion Benchmarks for Burnup Credit ValidationRevision 1, Adams Number ML18088B395, Electric Power Research Institute, 2018.

7. V. Kucukboyaci, EPRI Depletion Benchmark Calculations Using PARAGON, ANS NCSD, October 2013.

8. NEI-12-16, Rev. 4, Guidance for Performing Criticality Analyses of Fuel Storage at Light-Water Reactor Power Plants, Adams Number ML19269E069, Sept. 2019.

9. Regulatory Guide (RG) 1.240, Fresh and Spent Fuel Pool Criticality Analyses, Adams Number ML20356A127, March 2021.

10. NUREG/CR-6979, Evaluation of the French Haut Taux de Combustion (HTC) Critical Experiment Data, U.S. Nuclear Regulatory Commission, Adams Number ML082880452, September 2008.

11. NUREG/CR-6665, Review and Prioritization of Technical Issues Related to Burnup Credit for LWR Fuel, U.S. Nuclear Regulatory Commission, Adams Number ML003688150, February 2000.

12. Westinghouse Document WCAP-9522, FIGHTH - A Simplified Calculation of Effective Temperatures in PWR Fuel Rods for Use in Nuclear Design, May 1979.

13. NUREG/CR-6801, Recommendations for Addressing Axial Burnup in PWR Burnup Credit Analyses, Oak Ridge National Laboratory, Adams Number ML031110292, March 2003.

14. ML19189A111, Final Safety Evaluation by the Office of Nuclear Reactor Regulation Topical Report 3002010613, Benchmarks for Qualifying Fuel Reactivity Depletion WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 7-2 UncertaintyRevision 1 and Topical Report 3002010614, Utilization of the EPRI Depletion Benchmarks for Burnup Credit ValidationRevision 1, U.S. Nuclear Regulatory Commission, 2019.

15. NUREG/CR-7109, An Approach for Validating Actinide and Fission Product Burnup Credit Criticality Safety Analyses-Criticality (keff) Predictions, Oak Ridge National Laboratory, Adams Number ML12116A12, April 2012.

16. DG-1389, Alternative Radiological Source Terms Alternative Radiological Source Terms at Nuclear Power Reactors, Adams Number ML21204A065.

17. NUREG/CR-6759, Parametric Study of Effect of Control Rods for PWR Burnup Credit, Oak Ridge National Laboratory, Adams Number ML020810111, February 2002.

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Westinghouse Non-Proprietary Class 3 A-1 APPENDIX A VALIDATION OF SCALE 6.2.4 A.1 INTRODUCTION This validation suite is intended to be used for fresh and spent fuel storage in the Turkey Point Units 3 &

4 Spent Fuel Pool Criticality Safety Analysis. [

]a,c In order to validate the Scale Version 6.2.4 code system with the 252-group ENDF/B-VII.1 library (referred to hereafter as Scale) for the Turkey Point Units 3 & 4 Spent Fuel Pool criticality safety analysis, guidance from the NRC publications Guide for Validation of Nuclear Criticality Safety Calculational Methodology (Reference A1) and Applying Statistics (Reference A14) were used and, as recommended in Reference A1, the International Handbook of Evaluated Criticality Safety Benchmark Experiments (Reference A2), has been used as the primary source of critical benchmarks for the validation effort. References A3 through A7 were also used as additional sources of critical benchmarks.

Per Reference A1, the following are important parameters when defining the area of applicability of a benchmark suite: fissile isotope, enrichment of the fissile isotope, fuel density, fuel chemical form, type of neutron moderators and reflectors, range of moderator to fissile isotope, neutron absorbers, and physical configurations. Therefore, these were the parameters considered when choosing which critical experiments to include in this validation suite.

This validation suite is designed to cover fresh and spent fuel storage for Turkey Point Units 3 & 4. It also covers the criticality analysis of all normal operations and postulated accidents in the SFPs and fresh fuel storage. The validation is adequate to cover all present and anticipated (non-mixed-oxide) light water reactor (LWR) fuel designs at Turkey Point.

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Westinghouse Non-Proprietary Class 3 A-2 A.2 METHOD DISCUSSION The validation methods recommended in Reference A1 are the basis of this validation of Scale for nuclear criticality safety calculations. The code methodology bias and the uncertainty associated with the bias will be used in combination with other biases and uncertainties, as well as additional subcritical margin to ensure the regulatory requirements are met. Statistical analysis is performed to determine whether trends exist in the bias for four subsets of experiments; fresh fuel with strong absorbers, fresh fuel without strong absorbers, fresh and burnt fuel with strong absorbers, and fresh and burnt fuel without strong absorbers.

No critical experiments containing Gadolinia or Erbia were used because they will not be credited in the Turkey Point Criticality Safety Analysis either as fresh or residual absorbers.

[

] a,c Normality testing for the data subsets is performed as outlined in References A1 and A8 using the Shapiro-Wilk test for data sets with a sample size of 50 or less and the DAgostino normality test for the data sets with a sample size of more than 50. For the cases which fail the normality tests, the non-parametric statistical treatment recommended in Reference A1 is used.

A.2.1 Test for Normality (Goodness-of-Fit Test)

As stated in Reference A1, the statistical evaluation performed must be appropriate for the distribution of the data. A goodness-of-fit test is a procedure designed to examine whether a sample has come from a postulated distribution. Among the methods for testing goodness-of-fit, some are superior to others in their sensitivity to different types of departures from the hypothesized distribution. Some of the tests are quite general in that they can apply to just about any distribution, while other tests are more specific, such as tests that apply only to the normal distribution. [

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-3 A.2.1.1 Shapiro-Wilk Test for Normality References A1 and A8 discuss the Shapiro-Wilk test for normality (W-test). The W-test is applicable when neither the population mean () nor the population standard deviation () is specified. The W-test is considered an omnibus test for normality because of its superiority to other procedures over a wide range of problems and conditions that depend on an assumption of normality. The W-test is superior to the chi-square test (used by USLSTATS from Scale package) in many situations. This analysis thus uses the W-test as recommended in Reference A8 for sample sizes between 3 and 50, the range over which Table T-6b provides the critical value wq (n).

The null and alternative hypotheses are:

H0: The sample comes from a normal distribution.

H1: The underlying distribution is not normal.

The W-test statistic is:

2

= Equation A-1 (1) 2

where, n is the number of experiments in the group, S2 is the dataset variance, and

= =1 (+1) () Equation A-2

where, k = n/2 if n is even or (n-1)/2 if n is odd ai = i coefficients obtained from Table T-6a of NUREG-1475, Applying Statistics (Reference A8) associated with sample size n (1) , (2) , , () is the normalized keff of each experiment arranged in ascending order The null hypothesis H0 of normality is rejected at the level of significance if the calculated value of W is less than the critical value wq (n) obtained from Table T-6b of Reference A8. Note that in this table, the quantile q=.

A.2.1.2 DAgostino Test for Normality Reference A8 discusses the DAgostino test for normality (D test). Like the W-test, the D test is also applicable when neither nor is specified. Like the W-test, the D test is also considered an omnibus test for normality because of its superiority to other procedures over a wide range of problems and WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-4 conditions that depend on an assumption of normality. The D test complements the W-test, which is used for samples no larger than 50, and can be used for any sample size greater than 50.

The null and alternative hypotheses for D test are:

H0: The sample comes from a normal distribution.

H1: The underlying distribution is not normal.

The test statistic is:

= Equation A-3 2 (1)

where, n is the number of experiments S2 is the dataset variance

(+1)

= =1 () Equation A-4 2

(1) , (2) , , () is the normalized keff of each experiment arranged in ascending order The values of the D test (i.e., calculated values of the test statistic D) have a small range, which is defined as the maximum minus the minimum value in a set of values. Thus, for any given size sample, calculations should be carried out to at least five significant digits. The D test involves a comparison of the calculated D value with two quintiles from Table T-14 of Reference A8. The test is two-sided and requires two critical values that bound a noncritical region. For each combination of n and , the critical values are found in Table T-14 under the row that corresponds to n and the columns for q/2(n) and q1- /2(n). If the calculated D is not between these two values, the null hypothesis is rejected.

If the null hypothesis is rejected, a non-parametric treatment may be applied. If the null hypothesis is not rejected, then a technique such as a one-sided tolerance limit described in Reference A1 can be used to determine the appropriate bias and bias uncertainty.

A.2.2 Determination of Bias and Bias Uncertainty The statistical analysis presented in Section 2.4 of Reference A1 is followed for all datasets that passed the appropriate test for Normality. This approach involves determining a weighted mean that incorporates the uncertainties from both the measurement (exp) and the calculation method (calc). The benchmark experiments chosen from References A2, A6, and A7, use the experimental uncertainties presented in References A2, A6 and A7, respectively. Experimental uncertainty is not presented for the experiments contained in NUREG/CR-6361, Criticality Benchmark Guide for Light-Water-Reactor Fuel in Transportation and Storage Packages (Reference A3), so the average value of experimental uncertainties of similar experiments documented in Reference A2 is used. This is consistent with the recommendation WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-5 in Reference A1 that engineering judgment be used to approximate typical experimental uncertainties rather than assume no experimental uncertainty.

If the critical experiment being modeled is at a state other than critical (i.e., k 1.0) then an adjustment is made to the calculated value of keff. This adjustment is done by normalizing the calculated eigenvalue to the experimental value. This normalization assumes that the inherent bias in the calculation is not affected by the normalization, which is valid for small differences in keff. To normalize keff, the calculated keff (kcalc) is divided by the keff evaluated in the experiment (kexp):

= Equation A-5 The normalized keff (knormal)values are used in the subsequent determination of the bias and bias uncertainty, therefore all subsequent instances of keff should be taken to mean the normalized keff value.

The Monte Carlo calculational uncertainty (calc) and experimental uncertainties (exp) are root-sum-squared to create a combined uncertainty ( ) for each experiment:

2 2

= + Equation A-6 A weighted mean keff ( ) is calculated by using the weighting factor 1/2 . The use of this factor reduces the weight of the data with high uncertainty. Within a set of data, the ith member of that set is shown with a subscript i. Henceforth, unless otherwise specified, the combined uncertainty for an ith keff is shown as . The weighted equation variables for the single-sided lower tolerance limit are as follows:

Variance about the mean:

1 1 2 1 2 2 =

1 1 Equation A-7 2

Average total uncertainty:

2

= 1 Equation A-8 2

The weighted mean keff value:

1 2

=

1 Equation A-9 2

The square root of the pooled variance:

2

= 2 + Equation A-10 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-6

where, s2 = variance about the mean n = number of critical experiments used in the validation

= average total uncertainty Bias is determined by the relation:

1.0 <1.0

= Equation A-11 0.0 1.0 Reference A1 states that when a relationship between a calculated keff and an independent variable cannot be determined (no trend exists), a one-sided lower tolerance limit should be used. This method provides a single lower limit above which a defined fraction of the true population of keff is expected to lie, with a prescribed confidence and within the area of applicability. Use of this method requires the experimental results to have a normal statistical distribution. Lower tolerance limits, at a minimum, should be calculated with a 95% confidence that 95% of the data lies above KL. The equation for the one-sided lower tolerance band from Reference A1 is:

= Equation A-12 Or, if 1,

= 1 Equation A-13 Where, SP is the pooled variance, U is the one sided lower tolerance factor (found in Table T-11b of Reference A8 where n is the number of experiments contained in the data set).

USP is then taken as the uncertainty to the untrended bias (untrended bias uncertainty).

A.2.3 Identify Trends in the Data Trends are determined using regression fits to the calculated results. Based on a visual inspection of the data plots, it is determined that a linear fit is sufficient to evaluate whether there is a trend in the bias. In the following equations, x is the independent variable representing the parameter of interest (e.g.,

enrichment). The variable y represents keff. Variables a and b are coefficients for the function where b is the slope and a is the intercept. The function Y(x) represents Kfit(x).

Per Reference A1, the equations used to produce a weighted fit of a straight line to the data are given in this section.

( ) = + Equation A-14 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-7

where, 1 2

=

2 2 2 2 1 1

=

2 2 2 2 2

1 2

= 2 2 2 Once the data has been fit to a line, a determination as to the goodness of fit must be made. Per Reference A1, two steps should be employed when determining the goodness of fit. The first step is to plot the data against the independent variable which allows for a visual evaluation of the effectiveness of the regression fit.

The second step is to numerically determine a goodness of fit after the linear relations are fit to the data.

This adds a useful measure because visual inspection of the data plot will not necessarily reveal just how good the fit is to the data. Per Reference A1, the linear correlation coefficient is one standard method used to numerically measure the linear association between the random variables x and y.

The sample correlation coefficient between x and y (linear-correlation coefficient) is a quantitative measure of the degree to which a linear association exists between two variables. For weighted data, the linear correlation coefficient is:

1 2 ( )( )

= 1 1

Equation A-15 2 2 2 ( ) 2 ( )

where, The weighted mean for the independent parameter is:

1 2

=

1 Equation A-16 2

The weighted mean for the dependent parameter () is k eff .

The value of r2 is the coefficient of determination. It can be interpreted as the percentage of variance of one variable that is predictable from the other variable. The closer r2 approaches the value of 1, the better the fit of the data to the linear equation. Note that the value of a sample correlation coefficient r shows only the extent to which x and y are linearly associated. It does not by itself imply that any sort of causal relationship exists between x and y.

In addition to the linear correlation coefficient, the Students t test is used to determine if the trend in the linear fit of the data is statistically significant. A trend is statistically significant when the slope of the WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-8 linear regression fit (b) is equal to some specified value (b0). For the purposes of this validation suite, the null hypothesis, H0: b0 = 0 is that no statistically significant trend exists (slope is zero) with an alternative hypothesis of H1: b0 0, at a significance level of = 0.05.

In order to determine if the null hypothesis is supported, tscore is calculated and compared to the Students t distribution (t/2,n-2). The tscore for the slope of a regression line is given by:

( 0 )2

=

Equation A-17

( )2

where, SSE is the sum of the squares of the residuals:

= [ ( + )]2 Equation A-18 The null hypothesis is rejected if ltscorel > t/2, n-2.

When H0 is rejected and a statistically significant trend is determined, the trended value of a bias and its associated uncertainty are used when it is more restrictive than the untrended value of the bias. In the area where untrended bias yields more restrictive value, the untrended bias and its associated uncertainty are used.

Per Reference A1, when a relationship between a calculated keff and an independent variable can be determined (the trend exists), a one-sided lower tolerance band may be used. This conservative method provides a fitted curve above which the true population of keff is expected to lie. The equation for the one-sided lower tolerance band from Reference A1 is:

(2,2) 1 ( )2 (2)

() = ( ) 2 + ( 2 + 21 2 Equation A-19

) 1,2 Kfit(x) is the function derived in the trend analysis described above. Because a positive bias may not be conservative, the following equation must be used for all values of x where Kfit(x) >1:

(2,2) 1 ( )2 (2)

() = 1 2 + ( 2

+ 21 2 Equation A-20

) 1,2

where, p = The desired confidence level (0.95)

(2,2)

= The F distribution percentile with degree of fit, n-2 degrees of freedom. The degree of fit is 2 for a linear fit.

n = The number of critical experiment keff values WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-9 x = The independent fit variable xi = The independent parameter in the data set corresponding to the ith keff value

= The weighted mean of the independent variables 21 = The symmetric percentile of the normal distribution that contains the P fraction 1

=

2 2

1,2 = The upper Chi-square percentile For a weighted analysis:

1 2 ( )2

( )2 =

1 1 Equation A-21 2

1 2

=

1 Equation A-22 2

2 2

= + Equation A-23 2 = 1 Equation A-24 2

1 1 2 2 2 ( )

2

=

1 1 Equation A-25 2

Within the equation for KL:

1.0 <1.0

() = 0.0 1.0 Equation A-26 And the uncertainty in the bias is:

(2,2) 1 ( )2 (2) 95/95 () = 2 + ( 2

+ 21 2 Equation A-27

) 1,2 When H0 is rejected and a statistically significant trend is determined, the trended value of a bias and its associated uncertainty should be used while it is more restrictive than the untrended value of the bias. In the area where an untrended bias yields a more restrictive value, the untrended bias and its associated uncertainty shall be used.

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Westinghouse Non-Proprietary Class 3 A-10 A.2.4 Non-Parametric Treatment If the data fails the test for normality, a non-parametric treatment of the data will be necessary. Per Reference A1, the determination of KL, the lower limit of the 95/95 tolerance interval is as follows:

= Equation A-28

where, k min eff is the minimum (smallest) normalized keff in a dataset, uncertainty for k min eff is the pooled Monte Carlo and experimental uncertainty, and NPM is the non-parametric margin, which is added to account for the small sample size.

The non-parametric treatment outlined in Reference A1 uses the order statistics to represent the characteristics of a dataset after it has been ranked (ordered) from the smallest observed keff ( ) to the largest observed keff ( ). The following equation is the general equation that determines the percent confidence that a fraction of the population is above the lowest observed value:

1  !

= 1 =0 (1 ) x 100% Equation A-29

!()!

where:

q is the desired population fraction (normally 0.95) n is the number of data values in one data set m is the rank order indexing from the smallest sample value to the largest (m = 1 for the smallest sample value; m = 2 for the second smallest sample value, etc.).

The smallest observed keff has the rank order index 1 and the largest observed keff has the rank order index equal to the number of observations. Thus, for a desired population fraction of 95% and (rank order index 1), the percent confidence that a fraction of the population of n data points is above the lowest observed value is:

= (1 0.95 ) x 100% Equation A-30 Similarly, for a desired population fraction (q) of 95% and the 2nd lowest keff (rank order index m=2), the percent confidence that a fraction of the population of n data points is above the second lowest observed value is:

= 1 0.95 + (1)! (1 0.95) 0.951 x 100% Equation A-31 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-11 Although 59 experiments would be required to reach a 95/95 tolerance limit for rank order 1 as stated in Reference A1, the recommended non-parametric margin (NPM) correction is 0.0 for confidence values greater than 90 percent, as also indicated in Table 2.2 of Reference A1.

Within the equation for KL:

1.0 <1.0

= Equation A-32 0.0 1.0 And the uncertainty in the bias is:

= 2 + 2 Equation A-33

where, 2 is the Monte Carlo uncertainty from the selected rank order case 2 is the experimental uncertainty from the selected rank order case A rank order of 2 may be used in determination of the percent of confidence that a fraction of the population is above the lowest observed value if the sample size is greater than 93. This effectively means that the second lowest keff is used for the determination of the Bias and Bias uncertainty. Employing the aforementioned methods will produce a particularly conservative bias and bias uncertainty and negate the need for any further trending analysis for a non-parametric data set.

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Westinghouse Non-Proprietary Class 3 A-12 A.3 DESCRIPTION OF CRITICAL EXPERIMENTS Many studied series of the critical experiments allow using a simplified model with some zones homogenized or omitted. Only the complete model provided in Section 3.0 of each evaluated series of experiments is used for keff determination.

A.3.1 [

]a,c

[

]a,c A.3.2 [

]a,c

[

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-13

[

]a,c A.3.3 [

]a,c

[

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Westinghouse Non-Proprietary Class 3 A-14 A.3.4 [

]a,c

[

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Westinghouse Non-Proprietary Class 3 A-15 A.3.5 [

]a,c

[

]a,c A.3.6 [

]a,c

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Westinghouse Non-Proprietary Class 3 A-16

[

]a,c A.3.7 [

]a,c

[

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Westinghouse Non-Proprietary Class 3 A-17 A.3.8 [

]a,c

[

]a,c A.3.9 [

]a,c

[

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Westinghouse Non-Proprietary Class 3 A-18

[

]a,c A.3.10 [

]a,c

[

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Westinghouse Non-Proprietary Class 3 A-19

[

]a,c A.3.11 [

]a,c

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Westinghouse Non-Proprietary Class 3 A-20

[

]a,c A.3.12 [

]a,c

[

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Westinghouse Non-Proprietary Class 3 A-21

[ ]a,c A.3.13 [

]a,c

[

]a,c A.3.14 [

]a,c

[

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Westinghouse Non-Proprietary Class 3 A-22

[

]a,c A.3.15 [

]a,c

[

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Westinghouse Non-Proprietary Class 3 A-23

[

]a,c Benchmark Values of keff and Respective Uncertainties a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-24 A.3.16 [

]a,c

[

]a,c A.3.17 [ ]a,c NUREG/CR-6361 (Reference A3) is intended as a guide for performing criticality benchmark calculations for LWR fuel applications. It documents 180 critical experiments and includes recommendations for selecting suitable experiments and determining the calculational bias and bias uncertainty. When selecting experiments, preference is given to Reference A2 because it is more current than Reference A3. [

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-25

[ ]a,c a,c

[

]a,c A.3.18 HTC Experiments The HTC experiments are a series of experiments performed with mixed oxide rods designed to have a U and Pu isotopic composition representative to that of U(4.5%)O2 PWR fuel with 37,500 MWd/MTU burnup. No fission products are included in the composition. Up to this point, all the experiments modeled in this suite represent fresh fuel; the HTC experiments are included to ensure the validation suite covers spent fuel as well. The HTC critical experiment set was taken from two phases:

• Phase 1 - Water-Moderated and Reflected Simple Arrays (Reference A5)

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Westinghouse Non-Proprietary Class 3 A-26

• Phase 2 - Reflected Simple Arrays Moderated by Water Poisoned with Gadolinium or Boron (Reference A6)

• Phase 3 - Pool Storage (Reference A7)

Reference A4 is an ORNL evaluation of the HTC experiments. [

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Westinghouse Non-Proprietary Class 3 A-27

[

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Westinghouse Non-Proprietary Class 3 A-28 A.4 RAW CALCULATION RESULTS

[

]a,c Definitions of kcalc, kexp, knormal and their associated uncertainties are explained in Section A.2.

[

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Westinghouse Non-Proprietary Class 3 A-29

[ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-30 Table A-3 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-31 Table A-3 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-32 Table A-3 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-33

[ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-34 Table A-4 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-35 Table A-4 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-36

[ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-37 Table A-5 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-38 Table A-5 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-39 Table A-5 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-40

[ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-41 Table A-6 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-42 Table A-6 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-43 Table A-6 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-44 Table A-6 [ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-45

[ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-46 A.4.1 [ ]a,c

[

]a,c

[

]a,c a,c

[

]a,c A.4.2 [ ]a,c

[

]a,c

[

]a,c a,c

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Westinghouse Non-Proprietary Class 3 A-47 Note that the quintiles, Dq(n), of the distribution of the D' statistic in Reference A8 are provided only for even n. For the odd n, linear interpolation is used between adjacent values.

A.4.3 [ ]a,c

[

]a,c

[

]a,c a,c

[

]a,c A.5 TRENDING ANALYSIS The regression fits and goodness of fit tests similarly described in A.2.1 are applied to each subset of data for each of the following parameters when appropriate:

• Energy of Average Lethargy Causing Fission (EALF, eV)

• Enrichment (wt.% 235U)

• Pin Pitch (cm)

• Soluble Boron Concentration (ppm) 10

• B Areal Density of Poison Plates (g/cm2)

Only statistically significant trends in the data are of importance. The null hypothesis is that the slope of the trend is zero (no trend) and is tested to determine if there is 95% confidence that the calculated slope is a more accurate representation than a zero slope. The equations from Reference A1 are applied to the results to calculate the fitting coefficients. A test statistic is calculated and compared to the two-tailed Student's t distribution with 95% confidence and n-2 degrees of freedom (n represents number of experiments). The two-tailed inverse of the Student's t distribution can be extracted from an EXCEL function, T.INV.2T (0.05, (n-2)), for =0.05 (95% confidence level). If the absolute value of the test statistic is greater than the Student's t distribution critical value t0 95(n-2), this indicates that a statistically significant trend exists. If a trend in a parameter is found, Reference A1 recommends the use of a one-sided tolerance band for bias uncertainty determination. The width of the tolerance band is the bias uncertainty.

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Westinghouse Non-Proprietary Class 3 A-48 It is noted that AEG was not evaluated. AEG and EALF both account for energy differences in the experiments; however since AEG is associated with energy groups, these groups are not distributed equally which produces more error in determining if there is statistical significance. As noted in Appendix A Section A.1.1 of Reference A15 the spectrum range can be quantified be either EALF or AEG, therefore either is sufficient.

A.5.1 [ ]a,c

[

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Westinghouse Non-Proprietary Class 3 A-49 Table A-11 [

]a,c Statistical Data Parameter a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-50 a,c a,c Figure A-3[ ]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-51

[

]a,c A.5.1.1 [ ]a,c

[

]a,c

[ ]a,c a,c

[

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Westinghouse Non-Proprietary Class 3 A-52 A.5.1.2 [ ]a,c

[

]a,c

[ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-53

[

]a,c a,c

[

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Westinghouse Non-Proprietary Class 3 A-54 Table A-14 [

IParametl'r a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-55

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Westinghouse Non-Proprietary Class 3 A-56

[

]a,c

[ ]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-57

[

]a,c

[ ]a,c a,c

[

]a,c A.5.1.3 [ ]a,c

[

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Westinghouse Non-Proprietary Class 3 A-58

[

]a,c A.5.2 [ ]a,c

[

]a,c Table A-17 [

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Westinghouse Non-Proprietary Class 3 A-59 a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-60 A.5.2.1 [ ]a,c

[

]a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-61

[ ]a,c a,c

[

]a,c A.5.3 [ ]a,c

[

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Westinghouse Non-Proprietary Class 3 A-62 Table A-19 a,c A.5.4

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a.c WCAP--18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-63

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]a,c a,c WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 A-64

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Westinghouse Non-Proprietary Class 3 A-65

[

]a,c

[ ]a,c a,c

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Westinghouse Non-Proprietary Class 3 A-66 A.6 AREA OF APPLICABILITY

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Westinghouse Non-Proprietary Class 3 A-67

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Westinghouse Non-Proprietary Class 3 A-68 A.7 VALIDATION

SUMMARY

[

]a,c Summary of Biases and Bias Uncertainties Determination a,c

[

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Westinghouse Non-Proprietary Class 3 A-69 A.8 REFERENCES A1. NUREG/CR-6698, Guide for Validation of Nuclear Criticality Safety Calculational Methodology, Science Applications International Corporation, January 2001.

A2. International Handbook of Evaluated Criticality Safety Benchmark Experiments, NEA/NSC/DOC (95) 03, September 2013.

A3. NUREG/CR-6361, Criticality Benchmark Guide for Light-Water-Reactor Fuel in Transportation and Storage Packages, U.S. Nuclear Regulatory Commission, 1997.

A4. NUREG/CR-6979, Evaluation of the French Haut Taux de Combustion (HTC) Critical Experiment Data, U.S. Nuclear Regulatory Commission, September 2008.

A5. F.Fernex, Programme HTC - Phase 1: Réseaux de crayons dans leau pure (Water-moderated and reflected simple arrays) Réévaluation des expériences, DSU/SEC/T/2005-33/D.R., Institut de Radioprotection et de Sûreté Nucléaire, 2008.

A6. F.Fernex, Programme HTC - Phase 2: Réseaux simples en eau empoisonnée (bore et gadolinium) (Reflected simple arrays moderated by poisoned water with gadolinium or boron)

Réévaluation des expériences, DSU/SEC/T/2005-38/D.R., Institut de Radioprotection et de Sûreté Nucléaire, May 2008.

A7. F.Fernex, Programme HTC - Phase 3: Configurations stockage en piscine (Pool storage)

Réévaluation des expériences, DSU/SEC/T/2005-37/D.R., Institut de Radioprotection et de Sûreté Nucléaire, May 2008.

A8. D. Lurie et al. Applying Statistics, NUREG-1475, Revision 1, U.S. Nuclear Regulatory Commission, March 2011.

A9. R.I. Smith et al., Clean Critical Experiment Benchmarks for Plutonium Recycle in LWRs, Volume I, EPRI NP-196, Electric Power Research Institute, April 1976.

A10. S.R. Bierman, Criticality Experiments with Neutron Flux Traps Containing Voids, PNL-7167, Pacific Northwest Laboratory, April 1990.

A11. L.W. Newman, Urania-Gadolinia: Nuclear Model Development and Critical Experiment Benchmark, DOE/ET/34212-41 (BAW-1810), Babcock & Wilcox, April 1984.

A12. T.C. Engelder et al., Spectral Shift Control Reactor Basic Physics Program, Critical Experiments on Lattices Moderated by D2O-H2O Mixtures, BAW-1231, Babcock & Wilcox Company, December 1961.

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Westinghouse Non-Proprietary Class 3 A-70 A13. T.C. Engelder et al., Spectral Shift Control Reactor Basic Physics Program, Measurement and Analysis of Uniform Lattices of Slightly Enriched UO2 Moderated by D2O-H2O Mixtures, BAW-1273, Babcock & Wilcox Company, November 1963.

A14. NUREG-1475, Rev. 1, Applying Statistics, U.S. Nuclear Regulatory Commission, March 2011 A15. NEI-12-16, Rev. 4, Guidance for Performing Criticality Analyses of Fuel Storage at Light-Water Reactor Power Plants WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 B-1 APPENDIXB NEI-12-16, REVSION 4 CHECKLIST Appendix B contains a reproduction of the NEI-12-16, Revision 4 APPENDIX C: CRITICALTIY ANALYSIS CHECKLIST, filled out for this analysis.

Subject Included Notes/Explanatlon/WCAP Location 1.0 Introduction and Overview Purpose of submittal YES Section 1 Changes requested YES Section 2 Summary of physical changes YES Section 2 Section 5 (Tech. Spec. markups included in Section 2.4 of YES Summary of Tech Spec changes the LAR)

Summary of analytical scope YES Section 1, 2 2.0 Acceptance Criteria and Regulatory Guidance Summary of requirements and guidance YES Section 2.1 Requirements documents referenced YES Section 2.1 Guidance documents referenced YES Section 2.2 and various Acceptance criteria described YES Section 2.1 and various 3.0 Reactor and Fuel Design Description Describe reactor operating parameters YES Section 3.1 Criticality Fuel Designs discussed in Section 2, more YES Describe all fuel in pool details throughout.

Geometric dimensions (Nominal and YES Tolerances) Section 3.2 Schematic of guide tube patterns YES Section 3.4.4 contains a modeling figure Section 3 and subsections, additional material YES assumptions are discussed in Section 4.1.1 and Material compositions 4.2.3 Describe future fuel. to be covered YES Section 2 and throughout for Criticality Fuel Design 3.

Geometric dimensions (Nominal and YES Tolerances) Section 3 and subsections Schematic of guide tube patterns NO Same as past fuel (variations of the same)

Material compositions YES Section 3 Describe all fuel inserts YES Section 3.3 Geometric dimensions (Nominal and YES Tolerances) See also Sections 4.1.1 and 4.2.3 Schematic (axial/cross-section) NO PYRX/WABA and IFBA in standard locations Material compositions YES See also sections 4.1.1 and 4.2.3 Describe non-standard fuel NO Not Applicable WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 B-2 Geometric dimensions NO Not Applicable Section 3.4.4 for Fuel Rod Baskets. Rack Inserts in Section YES Describe non-fuel items in fuel cells 3.4.3.

Nominal and tolerance dimensions YES See previous 4.0 Spent Fuel Pool/Storage Rack Description New fuel vault & Storage rack description YES Section 3.4 and subsections Nominal and tolerance dimensions YES Schematic (axial/cross-section) YES Material compositions YES Spent fuel pool, Storage rack description YES Section 3.4.2 Nominal and tolerance dimensions YES Overall pool axial cross section included. Tech. Specs.

NO Schematic (axial/cross-section) contain rack cross section.

Material compositions YES Other Reactivity Control Devices (Inserts) YES Section 3.4.3 Nominal and tolerance dimensions YES See also Sections 4.1.1 and 4.2.3 Schematic (axial/cross-section) NO No schematic given. Model details provided.

Material compositions YES Section also Sections 4.1.1 and 4.2.3 5.0 Overview of the Method of Analysis New fuel rack analysis description YES Section 5.8 and subsections Storage geometries YES Bounding assembly design(s) YES Integral absorber credit YES Dry, optimum moderation and fully flooded for fully Accident analysis YES loaded NFV. No additional accident analyses Spent fuel storage rack analysis description YES Section 4.2 and subsections Storage geometries YES Bounding assembly design(s) YES See also sections 4.1.3 and 4.1.4 Soluble boron credit YES See also Section 5.7 Boron dilution analysis NO Unchanged.

Burnup credit YES Section 4 throughout.

Decay/Cooling time credit YES Section 4.1.2.1 Integral absorber credit YES IFBA credit Other credit YES RCCAs can replace Metamic in Region 1, See section 4.2.1 Fixed neutron absorbers YES Boral and Metamic inserts used. See also Section 3.4.3.

Not included herein. Included in the LAR. (Section 2.1 of NO Aging management program the LAR)

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Westinghouse Non-Proprietary Class 3 B-3 Accident analysis YES Section 4.2.9 and 5.7.

Temperature increase YES Engineering judgement - Multiple Misload bounding Assembly drop YES Engineering judgement - Multiple Misload bounding Single assembly misload YES Multiple Misload bounding Multiple misload YES No, unchanged. Change in boron from TS to limits are the NO Boron dilution same.

Other NO Not Applicable Fuel out of rack analysis YES Section 5.5 Handling YES Movement YES Inspection YES 6.0 Computer Codes, Cross Sections and Validation Overview Code/Modules Used for Calculation of keff YES Section 2.3.2 Cross section library YES Section 2.3.3 All included in depletion plus additional modeled YES Description of nuclides used materials (structural/absorber).

Convergence checks YES Section 4.2.3 Code/Module Used for Depletion Calculation YES Section 2.3.1 Cross section library YES Description of nuclides used YES Convergence checks YES Yes, implicit in code warning/error checks.

Validation of Code and Library YES Appendix A Major Actinides and Structural Material YES Materials Appendix A Minor Actinides and Fission Products YES Section 4.2.5.1.12 Absorbers Credited YES 7.0 Criticality Safety Analysis of the New Fuel Rack Rack model YES Section 5.8 Boundary conditions YES See also section 4.2.3 uniform starting source, convergence checks as YES Source distribution previously described.

Geometry restrictions YES See Section 5.8 for modeling details.

Limiting fuel design YES As in Reference 2 (Analysis in Section 5.8)

Fuel density YES Burnable Poisons YES WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 B-4 Fuel dimensions YES Axial blankets YES Limiting rack model YES See Section 5.10. Entire Set of Racks Modeled.

Storage vault dimensions and materials YES See also Section 3.4.

Temperature NO Temperature bias included in rackup.

Limiting positioning considered from supporting NO Multiple regions/configurations Reference 2 analysis. See Section 5.8.

Flooded YES Low density moderator YES Nominal model is eccentrically placed to increase YES Eccentric fuel placement reactivity.

See section 5.8 and subsections. Refer to Section 4.2.5 Tolerances YES and subsections for basic descriptions.

Fuel geometry YES Fuel pin pitch YES Fuel pellet OD YES Fuel clad OD YES Fuel content YES Enrichment YES Density NO Bounding Value Utilized Integral absorber NO Bounding Value Utilized Rack geometry YES Rack pitch YES Cell wall thickness YES No explicit uncertainty. Models locate fuel in reactive Storage vault dimensions/materials NO location with the cell. See Section 5.8.1 for modeling details.

Code uncertainty YES Biases YES Temperature YES Code bias YES Moderator Conditions YES Fully flooded and optimum density YES moderator 8.0 Depletion Analysis for Spent Fuel Depletion Model Considerations YES Section 4.1 and subsections Not explicit, but standard design steps to begin and then NO Time step verification up to 2 GWd/MTU steps thereafter.

Within code warning error disposition. If not converged a NO Convergence verification warning would result.

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Westinghouse Non-Proprietary Class 3 B-5 Simplifications YES Non-uniform enrichments NO N/A B-10 zeroed, No residual absorber, 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> post YES Post Depletion Nuclide Adjustment operation cooling time.

Cooling Time YES Depletion Parameters YES Burnable Absorbers YES Integral Absorbers YES Soluble Boron YES Fuel and Moderator Temperature YES Power YES Control rod insertion NO Not Applicable. See Section 5.6 Atypical Cycle Operating History NO Not Applicable. See Section 5.6 9.0 Criticality Safety Analysis of Spent Fuel Pool Storage Racks Rack model YES Section 4.2 Periodic as described in Section 4.2. Any deviation YES Boundary conditions (interfaces) is discussed.

initial uniform sampling. See earlier for source YES Source distribution convergence.

Geometry restrictions YES See Section 4.2 Design Basis Fuel Description YES Section 4.1.3 and 4.1.4 Fuel density YES Burnable Poisons YES Fuel assembly inserts YES Fuel dimensions YES Axial blankets YES Configurations considered YES Section also Section 4.2.1 Soluble boron credit for normal and accident conditions NO Borated only, 50 ppm soluble boron added.

Unborated YES Multiple rack designs YES See also Section 3.4.2 Alternate storage geometry YES Fuel Rod Storage Baskets Reactivity Control Devices YES Section 3.3, 3.4.3, 4.2.1 and 4.2.3 Fuel Assembly Inserts YES Storage Cell Inserts YES Storage Cell Blocking Devices NO N/A Axial burnup shapes YES 4.1.2.2.4 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 B-6 Uniform/Distributed YES Nodalization YES See also Section 4.1.1 Yes. Section 4.1.4 describes annular fuel in criticality YES Blankets modeled models is modeled as solid.

Tolerances/Uncertainties YES Section 4.2.5 Fuel geometry YES Fuel rod pin pitch YES Fuel pellet OD YES Cladding OD YES Axial fuel position NO Fuel conservatively assumed at all same axial height.

Fuel content YES Enrichment YES Density NO Upper tolerance applied explicitly.

Assembly insert dimensions and materials YES See also Sections 3.4.3 and 4.2.3 Rack geometry YES Flux-trap size (width) NO Tolerances given on rack pitch change flux trap size.

Rack cell pitch YES Rack wall thickness YES Neutron Absorber Dimensions YES See also Sections 3.4.3 and 4.2.3 Rack insert dimensions and materials YES See also Sections 3.4.3 and 4.2.3 Code validation uncertainty YES Appendix A Used in developing each uncertainty impact as described YES in Section 4.2.5 (also very small, individual uncertainties Criticality case uncertainty not consequential as separate rackup item.)

Depletion Uncertainty YES Burnup Uncertainty YES Biases YES Section 4.2.5 No specific additional bias but design basis fuel is a NO Design Basis Fuel design conservative model.

Code bias YES Temperature YES Eccentric fuel placement YES Incore thimble depletion effect NO Effect is small and analysis is overall conservative.

NRC administrative margin YES 0.005 as indicated in rackups and throughout.

Modeling simplifications YES Section 4.2.3 Identified and described YES 10.0 Interface Analysis Interface configurations analyzed YES Section 4.2.8 WCAP-18830-NP September 2023 Revision 0

Westinghouse Non-Proprietary Class 3 B-7 Between dissimilar racks YES Between storage configurations within a rack YES Interface restrictions YES Section 5.4 11.0 Normal Conditions Fuel handling equipment YES Section 5.5 Administrative controls YES Fuel inspection equipment or processes YES Fuel reconstitution YES 12.0 Accident Analysis Boron dilution NO No update. See Section 3 of the LAR.

Normal conditions NO Accident conditions NO Single assembly misload NO*

• Judgement given that multiple misload is bounding.

Fuel assembly misplacement NO*

• Judgement given that multiple misload is bounding.

Neutron Absorber Insert Misload NO*

• Judgement given that multiple misload is bounding.

Multiple fuel misload YES Section 5.7.2 and 5.7.3 Dropped assembly NO*

• Judgement given that multiple misload is bounding.

Temperature NO*

• Judgement given that multiple misload is bounding.

Seismic event/other natural phenomena NO*

• Judgement given that multiple misload is bounding.

13.0 Analysis Results and Conclusions Summary of results YES Section 5 Burnup curve(s) YES Section 5 linear interpolation acceptable as indicated in Section YES Intermediate Decay time treatment 5.1.

New administrative controls NO Technical Specification markups YES Included in Section 2.4 of the LAR.

14.0 References YES Section 7 Appendix A: Computer Code Validation:

Code validation methodology and bases YES Section A.2 New Fuel YES See Appendix A for multiple validation sets.

Depleted Fuel YES See Appendix A for multiple validation sets.

MOX fuel not considered. HTC covers burned fuel while NO MOX MOX has a much higher Pu concentration.

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Westinghouse Non-Proprietary Class 3 B-8 HTC YES See Appendix A Convergence YES As determined in supporting analysis.

Trends YES Sections A.2.3, A.6 Bias and uncertainty YES Section A.2.2 Range of applicability YES Section A.7 Analysis of Area of Applicability Coverage YES As determined in supporting analysis.

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