Text

Attachment 5 to Enclosure 1 - Criticality Safety Evaluation Report
	ML22242A293
Person / Time
Site:	Callaway
Issue date:	08/29/2022
From:	; Ameren Missouri, Holtec, Union Electric Co
To:	; Office of Nuclear Reactor Regulation
Shared Package
ML22242A122	List: ML22242A123; ML22242A124; ML22242A125; ML22242A126; ML22242A127; ML22242A293; ULNRC-06723, Attachment 4 to Enclosure 1 - Holtec Affidavit for Withholding;
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	ULNRC-06723 HI-2220020, Rev 1
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Attachment 5 to to ULNRC-06723 Page 1 of 140 ATTACHMENT 5 CRITICALITY SAFETY EVALAUTION REPORT (NON-PROPRIETARY VERSION)

The following pages provide the non-proprietary version of the criticality safety analysis report provided by HOLTEC International supporting this license amendment request.

HI-2220020, Criticality Safety Analysis of $FP for Callaway, Revision 1

[NON-PROPRIETARY]

139 pages follow this cover sheet

Criticatity Safety Analysis of SEP for Catlaway RI.

Criticality Safety Analysis of SFP for Callaway HOLT (NTERNATIONAL EC EXECUTIVE

SUMMARY

This report documents the criticality safety analyses of the spent fuel pool performed for the Callaway Unit 1, which contains a single type of BORALTM spent fuel racks designed for storage of the PWR 17x17 fuel assemblies. The criticality evaluations qualify the spent fuel racks loaded with two storage configurations, including uniform loading of spent fuel assemblies with various cooling times and a checkerboard configuration of fresh fuel assemblies and empty storage cells. The purpose of this report is to provide a complete up-to-date criticality safety evaluation based on the latest methodologies consistent with the current NRC expectations. The difference between this analysis and the analysis of record is an extended list of qualified fuel assemblies, simplified loading configurations (regions) that no longer include the MZTR (Mixed-Zone Three-Region) approach, and a new analysis methodology. There is no change ofthe spent fuel racks.

The analysis of fuel irradiation during core operation is performed with CASMO5 Version 2.08.00, a multigroup two-dimensional transport theory code based on the Method of Characteristics, using the ENDF/B-Vll Library. The criticality calculations are performed with MCNP5 Version 1.51, a three-dimensional continuous energy Monte Carlo code, using continuous energy For a storage configuration with spent fuel assemblies, the minimum required burnups as a function of enrichment (a third-order polynomial fit) have been determined, considering various cooling times. All credible normal and accident conditions have been analyzed, and the results of the calculations show that the effective neutron multiplication factor (keff) Of the spent fuel pool loaded with fuel of the highest anticipated reactivity, at a temperature corresponding to the highest reactivity, is less than 1.0 for the pool flooded with unborated water and does not exceed 0.95 for the pool flooded with borated water, alt for 95% probability at a 95% confidence level, in accordance with 10 CFR 50.68(b)(4).

All credible interface conditions in the spent fuel pool have been considered and the storage configurations interface criteria are established. Fuel assembly reconstitution activities and storage of fuel rod storage racks are also considered and qualified.

An evaluation of the potential reactivity effect of a degradation of the BORAL performance, and available margin in the criticality analysis to possibly offset such degradation is also performed.

Criticality Safety Analysis of SFP for Callaway 11111 HOLTEC NTERNAT(ONAL Table of Contents EXECUTIVE

SUMMARY

II 1.0 PURPOSE I 2.0 ACCEPTANCE CRITERIA 2 3.0 METHODOLOGY 3 3.1 GENERALAPPRQACH 3 3.2 COMPUTER CODES AND CROSS-SECTION LIBRARIEs 3 3.2.1 CASMQ5Overview 3 3.2.2 MCNP5 Overview 4 3.3 ANALYSIS METHODS 5 3.31 Design Basis FuelAssembly Design 7 3.3.2 FuelAssembly Parameters 7 3.3.3 Spent Fuel Rack Parameters 8 3.3.4 Spent Fuel Pool Water Temperature 10 3.3.5 FuelAssembly Radio/Positioning and Orientation 11 3.3.5 Spent Fuel Reactivity Calculation 12 3.3. 7 Design Basis Calculations 21 3.4 SPENT FUEL RACK INTERFACES 22 3.4.1 Interfaces between different SFRs 22 3.4.2 Interfaces between Storage Racks and the SFP Wall 23 3.4.3 Region 1 to Region 2 Interface 23 3.4.4 Region to Region I Interface 25 3.4.5 Region 2 to Region 2 Interface 25 3.4.6 Combined Qualifications 25 3.5 NORMALCONDJT1ONS 25 3.5.1 Fuel Movement Operations 25 3.5.2 Fuel Insertion and Removal Operations 26 3.5.3 Storage ofFuel RodStorage Rack 26 3.5.4 Storage ofFuelAssemblies with Missing Rods 27 3.5.5 Storage of Low-Burned FuelAssemblies 27 3.6 ABNORMAL AND ACCIDENT CONDITIONs 28 3.6.1 Loss ofSFP Cooling 28 3.6.2 DroppedAssembly Horizontal 29 3.6.3 Dropped Assembly Verticalinto a Storage Cell 29 3.6.4 Mislocated Fuel Assembly 29 3.6.5 Misloaded FuelAssembly 29 3.6.6 Incorrect Loading Curve 30 3.6.7 RackMovement 30 3.6.8 Boron Dilution 30 3.7 MARGIN EVALUATION 31

3. 7.1 Neutron Absorber Aging Effects 31

3. 72 BORALTM Panel°B Areal Density 32

3. 7.3 Criticality Analysis Safety Margin 32 3.8 PERMITTED FUTURE FUEL ASSEMBLIES 33 4.0 ASSUMPTiONS 48 5.0 INPUTDATA 50 HI-2220020 Rev. I Page 3 of VII Copyright © 2022 Hottec Internationat, ott rights reserved

Criticality Safety Analysis of SFP for Caflaway *RSII HOLTEC INTERNATIONAL 51 FUELASSEMBLY DESIGNS 50 5.2 CoRE OPERATING PARAMETERS 50 5.3 INTEGRAL BURNABLE ABSORBER AND FUEL INSERTS 50 5.4 SPENT FUEL RACK DESIGN 51 5.5 SFPOPERATING PARAMETERS 51 5.6 MATERIAL COMPOSITIONS 51 5.7 FUELRODSTORAGE RACK 51 5.8 FUEL ASSEMBLIES WITH MISSING RODS 51 6.0 COMPUTER PROGRAMS 67 7.0 CALCULATIONS AND RESULTS 68 7.1 DESIGN BASIS FUELASSEMBLY DESIGN 68

7. 2 REACTIVITY EFFECT OF FUEL ASSEM ELY PARAMETERS 68 7.3 REACTIVITY EFFECT OF SFR PARAMETERS 68 7.3.1 Reactivity Effect of the 84C Particle Size 68 7.4 REACTIVITY EFFECT OF SFP WATER TEMPERATURE 69 7.5 REACTIVITY EFFECT OF FUEL ASSEMBLY RADIAL POSITIONING 69 7.6 SPENT FUEL REACTIVITY CALCULATION 69 76.1 Reactivity Effect of Core Operating Parameters 69 7.6.2 Reactivity Effect ofCooling Time 69 7.6.3 Reactivity Effect ofIBA and Fuel Inserts 70 7.6.4 Reactivity Effect ofAxial Burnup Profiles 71 7.6.5 Reactivity Effect of Depletion Related FuelAssembly Geometry Changes 71 7.6.6 Spent Fuel isotopic Content Uncertainty 71 7.7 DESIGN BASIS CALCULATIONS 71

7. 7. 1 Determination of the Spent Fuel Loading Curves 72

7. 7.2 Confirmatory Calculations 72 7.7.3 Maximum keffCalculation with Borated Water 72 7.8 SFRINTERFACES 72 7.9 NORMAL CONDITIONS 73 7.9.1 Storage ofFuel Rodstorage Rack 73 7.9.2 Storage ofFuelAssemblies with Missing Rods 73 7.10 ACCIDENTCONDITIONS 74 7.10.1 Misloaded Fuel Assembly 74 7.10.2 Incorrect Loading Curve 74 720.3 Boron Dilution 74 7.11 MARGIN EVALUATION 76

8.0 CONCLUSION

114

9.0 REFERENCES

116 APPENDIX A NEI 12-16 CRITICALITY ANALYSIS CHECKLIST A-i APPENDIX B

SUMMARY

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL List of Tables Table 3-1 Summary of Area of Applicability of the MCNPS Benchmark 34 Table 3-2 MCNPS Benchmark Analysis for Various Fuel and Water Subsets of Experiments 35 Table 3-3 Significant Trending Analysis for Callaway Parameters 36 Table 3-4 Summary of MCNP5 Code Validation Bias and Bias Uncertainty 37 Table 3-5 List ofSpent Fuel Isotopes 38 Table 3-6 Bounding Axial Burnup Profiles for Westinghouse I 7x1 7 Fuel Type [1 5]

39 Table 3-7 Bounding Axial Burnup Profiles from NUREG/CR-680f [26]

40 Table 5-1 Specification of the Fuel Assembly Parameters [20]

52 Table 5-2 PWR 17x17 Fuel Assembly Manufacturing Toterances 53 Table 5-3 PWR 17x17 FuelAssembly Depletion Related Geometry Changes 53 Table 5-4 Core Operating Parameters 54 Table 5-5 Specification ofthe Fuel Inserts [20]

55 Table 5-6 Specification of the Integral Burnable Absorbers 56 Table 5-7 Specification of the Callaway SFR Parameters 57 Table 5-8 SFP Operating Parameters [19], [29], [34], [35]

58 Table 5-9 Material Compositions ofthe Major Design Components 59 Table 5-10 Fuel Rod Storage Rack Parameters 62 Table 7-1 Bounding Fuel Assembly Design 77 Table 7-2 Reactivity Effect of Fuel Assembly Parameters 78 Table 7-3 Reactivity Effect of SFR Parameters 79 Table 7-4 Reactivity Effect of SFP Waterlemperature 81 Table 7-5 Reactivity Effect of Fuel Assembly Radial Positioning 82 Table 7-6 Reactivity Effect of Core Operating Parameters 83 Table 7-7 Reactivity Effect of Cooling Time 84 Table 7-8 Reactivity Effect of irradiation with the IBA and Fuel inserts 85 Table 7-9 Reactivity Effect of Axial Burnup Profile 86 Table 7-1 0 Reactivity Effect of Depletion Related Fuel Assembly Geometry Changes 87 Table 7-1 1 Determination of Depletion Uncertainty, Burnup Uncertainty and MAFP Bias 88 Table 7-1 2 Summary of the Analysis for Region 2 (Spent Fuel) 90 Table 7-1 3 Summary of the Loading Curves for Caliaway SFP 95 Table 7-14 Loading Curves Confirmatory Calculations 96 Table 7-1 5 Summary of the Analysis for Region 1 (Fresh Fuel) 97 Table 7-16 Summary of the Analysis for Normal Conditions with Soluble Boron Credit 98 Table 7-17 Summary ofthe Analysis for the SFR interfaces 99 Table 7-1 8 Summary of the Analysis for the FRSR 100 Table 7-19 Summary ofthe Analysis for Fuel Assemblies with Missing Rods 101 Table 7-20 Deleted 102 Table 7-21 Maximum keff Calculation for the Fuel Misload Accident 103 Table 7-22 Maximum keff Calculation for the incorrect Loading Curve Accident 106 Table 7-23 SFP Boron Dilution Accident Analysis 107 Hi-2220020 Rev. 1 Page 5 of VII Copyright © 2022 Hottec Internationat, all rights reserved

Criticality Safety Analysis of SFP for CaUaway IRIRI HOLTEC INTERNATIONAL Table 7-24 Reactivity Effect of the BORALTM Panel 10B Areat Density 108 Table 7-25 Margin Evatuation 109 Table 7-26 Reactivity Effect of the B4C Particle Size I 10 Table B-I Summary ofthe Standard Key Parameters B-2 Table 8-2 Summary of Key Parameters for the Burnup Credit B-3 List of Figures Figure 1 -1 Caltaway SFR Permissible Loading Configurations 1 Figure 3-1 Radial CrossSection View ofthe MCNP5 Design Basis Model ofthe SFR 41 Figure 3-2 Design Basis Calculation of a keff Value 42 Figure 3-3 Determination of the Total Correction Factor 43 Figure 3-4 Radial Cross-Section View of the MCNP5 Model for the SFR Interfaces 44 Figure 3-5 Potential Interfaces between the Loading Regions 45 Figure 3-6 Radial Cross-Section View of the MCNP5 Model for the FRSR 46 Figure 3-7 MCNP5 Model of the Heterogeneous BORALTM Panel 47 Figure 5-1 Considered PWR 17x17 Fuel Assembly Layouts 63 Figure 5-2 Planar Cross-Section of the Callaway SFR 64 Figure 5-3 Axial Cross-Section of the Callaway SFR 65 Figure 5-4 Fuel Assembly Layouts with Missing Rods 66 Figure 7-1 Loading Curves for Uniform Loading of Spent Fuel Assemblies (Region 2) 111 Figure 7-2 Total Reaction Rate Distribution for Region 1 to Region 2 Interlace 112 Figure 7-3 Total Reaction Rate Distribution for Region 1 (2x2) to Region 2 Interface 112 Figure 7-4 BORALTM Panel 10B Areal Density as a Function of tk 113 HI-2220020 Rev. 1 Page 6 of VII Copyright © 2022 Hottec internationaL oil rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERN ATIONAL List of Abbreviations ACPL Holtec approved computer program list BPR burnable poison rod ccw component cooling water system CFR U.S. Code of Federat Regulations FRSR fuel rod storage rack IBA integral burnable absorber IFBA integral fuel burnable absorber 1D inner diameter MAFP minor actinides and fission products OD outer diameter PWR pressurized water reactor RCCA rod cluster control assembly RMWST reactor makeup water storage tank RWST refueling water storage tank SFP spent fuel pool SFR spent fuel rack ss stainless steel TCF total correction factor WABA wet annular burnable absorber Hl-2220020 Rev. 1 Page 7 of VII Copyright © 2022 HottecinternationaL att rights reserved

Criticality Safety Analysis of SFP for Callaway IIRW*

HOLTEC INTERNATIONAL 11 PURPOSE This report documents the criticality safety analyses of the spent fuel pool performed for the Callaway Unit 1 The SFP contains a single type of BORALTM spent fuel rack designed for storage ofthe PWR 17x17 fuel assemblies. The criticality safety analysis of record forthe Callaway SFP is documented in [1]. The purpose of the analyses presented in this report is to provide a complete up-to-date criticality safety evaluation for the Callaway SFP based on the latest methodologies consistent with current NRC expectations in [2J and [3], which will result in a replacement of the analysis of record. The difference between this analysis and the analysis of record is an extended list of qualified fuel assemblies, simplified loading configurations (regions) that no longer include the MZTR (Mixed-Zone Three-Region) approach, and a new analysis methodology. There is no change of the spent fuel racks.

The criticality control in the SFRs relies on various combinations ofthe following:

. Fixed neutron absorbers: BORAL poison panels;

. Burnup of spent fuel assemblies;

. Spent fuel cooling time;

. Empty SFR storage cells;

. Soluble boron in the SFP.

Specifically, the criticality evaluations qualify the SFRs loaded with the following configurations, hereinafter referred to as loading regions (see Figure 1-1):

. Region 1 a ZxZ checkerboard pattern with two fresh fuel assemblies and two empty storage cells. No credit of the IBA and soluble boron (under normal conditions) in the SFP is applied;

. Region 2 uniform loading of spent fuel assemblies with a credit of various cooling times and soluble boron in the SFP.

Criticality Safety Analysis of SFP for Callaway HOLT EC INTERNATIONAL Additionally, the criticality evaluations are performed for the following:

. Normal conditions:

0 credible interface conditions in the spent fuel pool; 0 fuel movement, insertion, and removal operations; 0 storage of fuel rod storage racks; 0 specific Callaway fuel inventory, such as the fuel assemblies with the missing rods; 0 fuel assembly reconstitution activities;

. Abnormal and accident conditions.

An evaluation of the potential reactivity effect of a degradation of the BORALTM performance, and available margin in the criticality analysis to possibly offset such degradation is also performed.

A summary of physical changes, technical specification changes and analyticat scope is provided in Appendix A, Appendix B and Appendix C.

2.1 ACCEPTANCE CRITERIA Codes, standard, and regulations or pertinent sections thereofthat are applicable to the analysis include the following:

. Code of Federal Regulations, Title 10, Part 50, Appendix A, General Design Criterion 62, Prevention of Criticality in Fuel Storage and Handling.

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

. USNRC Standard Review Plan, NUREG-0800, Section 9.1.1, Criticality Safety of Fresh and Spent Fuel Storage and Handling, Rev. 3 March 2007.

. us NRC Regulatory Guide RG 1.240, Fresh and Spent Fuel Pool Criticality Analyses, March 2021.

. ANSI ANS-8.17-1984, Criticality Safety Criteria for the Handling, Storage and Transportation of LWR Fuel Outside Reactors.

. USNRC, NUREG/CR-6698, Guide for Validation of Nuclear Criticality Safety Calculational Methodology, January 2001.

. DSS-ISG-2010-01, Revision 0, Staff Guidance Regarding the Nuclear Criticality Safety Analysis for Spent Fuel Pools.

Criticality Safety Analysis of SFP for Callaway HOLTEC NTERNAT1ONAL Power Plants, NEI 1 2-1 6, Revision 4, Nuclear Energy Institute.

The objective of this analysis is to ensure that the effective neutron multiplication factor (keff) of the SFP loaded with fuel of the highest anticipated reactivity, at a temperature corresponding to the highest reactivity, is tess than 1.0 for the pool flooded with unborated water and does not exceed O95 for the pool flooded with borated water, all for 95% probability at a 95% confidence level, in accordance with 1 0 CFR 50.68(b)(4).

3.0 METHODOLOGY 31 General Approach The analysis is performed in a manner such that the results are below the regulatory limit with a 95% probability at a 95% confidence level. The calculations are performed using either the worst-case bounding approach or the statistical analysis approach with respect to the various calculation parameters. The approach considered for each parameter is discussed below. These calculations are used to determine the final keff used to show compliance with the regulatory limits for both normal and accident conditions. The accident calculations are essentially modifications of the design basis cases for the normal conditions but do not introduce a new fuel or rack design change. Therefore, the uncertainty and bias calculations for the normal conditions are applicable and do not need to be repeated for the accident calculations.

3.2 Computer Codes and Cross-Section Libraries 3.2.1 CASMO5 Overview The analysis of fuel irradiation during core operation is performed with CASMO5 Version 2.08.00, which is commonly used in the industry for reactor analysis (depletion) when providing reactivity data for specific 3D simulator codes, and it has been reviewed by the NRC

[4]. CASMO5 is a multigroup two-dimensional transport theory code for burnup calculations of BWR and PWR fuel assemblies based on the Method of Characteristics [5] and it is developed by Studsvik of Sweden [6]. CASMOS allows modeling of a planar cross section of an individual fuel assembly, including all relevant details such as individual pellet and cladding diameters, locations of guide tubes and instrument tube, and material compositions of all materials. The calculations assume a planar and axially infinite array of fuel assemblies. The fuel and absorber dimensions, the operating parameters, an initial enrichment and a maximum burnup are provided in the input model, and the atom densities for actinides and fission products in the isotopic composition of spent fuel are determined by CASMOS. For all CASMO5 depletion calculations, the ENDF/B-Vll Library [71 is used. Although CASMOS has been extensively benchmarked, a code validation (i.e., bias and bias uncertainty) is not considered necessary because it is not used for reactivity calculations. Nonetheless, to ensure that CASMO5 produces reliable and predictable results, the uncertainty on the irradiated fuel isotopic composition (i.e.,

Criticality Safety Analysis of SFP for Callaway iii*i HOLT EC INTERN ATONA L uncertainties associated with depletion, such as uncertainty in computation of the isotopic inventory by the depletion code, uncertainty in cross-sections (both actinides and fission products), etc.

3.2.2 MCNP5 Overview MCNP5 Version 1.51 [8], a three-dimensional continuous energy Monte Carlo code developed at Los Alamos National Laboratory, is used for the criticality analyses. This code offers the capability of performing full three-dimensional calculations of the spent fuel storage racks. It has a long history of successful use in fuel storage criticality evaluations and has all of the necessary features for evaluation of the Callaway SFP. MCNP5 calculations use continuous energy 3.2.2. 1 MCNP5 Validation The benchmarking of MCNP5-1.51 is based on the guidance in [2] and [12], and includes calculations for a total of 562 critical experiments with fresh U02 fuel, fresh MOX fuel, and fuel with simulated actinide composition of spent fuel (Haut Taux de Combustion (HTC) experiments),

chosen, in so far as possible, to bound the range of variables in the SFP designs. Validation of MCNP5-1.51 and continuous energy ENDF/B-Vll data library to perform criticality safety calculations is documented in [13]. The validation confirms the accuracy of the calculational Hl-2220020Rev. 1 Page 4 of 118 Copyright © 2022 Hottec Internationat, all rights reserved

Criticality Safety Analysis of SFP for Callaway HOLT EC NTERN AflONAL methodology to predict subcriticality. Validation includes identification of the difference between calculated and experimental neutron effective multiplication factor (keff), called the bias. The range of the benchmark parameters used to validate the calculational methodology primarily defines the area of applicability (AQA), which establishes the limits of the systems that can be analyzed using the validated criticality safety methodology. The applicable range of key parameters for the design application and benchmarks are summarized in Table 3-1.

The results of the benchmarking calculations for the full set of all 562 experiments and various subsets are presented in Table 3-2 along with an estimate of significance of the observed trends.

Following the guidance in [2], the statistical treatment used to determine those values considered the variance of the population about the mean and used appropriate confidence factors and trend analysis. This is also consistent with the requirement in [3]. Trend analyses are performed for various subsets and parameters in [13], and the determined significant trends are presented in Table 3-2. In order to determine the maximum bias and bias uncertainty that are applicable to the criticality calculations in this report, the trend equations from [131 are evaluated in Table 3-3 for the specific parameters used in the current analysis.

Eased on the results presented in Table 3-2 and Table 3-3, the maximum MCNPS code validation bias and bias uncertainty associated with the appropriate benchmark subsets are determined for each loading region separately for unborated and borated water, and summarized in Table 3-4. The appropriate maximum bias and bias uncertainty are applied to all calculations to determine the maximum keff.

3.3 Analysis Methods As discussed in Section 3.1, the calculations are performed using either the worst-case bounding approach or the statistical analysis approach with respect to the various calculation parameters.

These bounding inputs and assumptions for the fuel and storage rack models are summarized below:

Bounding Fuet Designs and FuetAssembty Parameters:

Criticality Safety Analysis of SFP for Callaway *1R1I HOLTEC INTERNATIONAL Bounding Storage Rack Parameters:

Bounding SFP Moderator Temperature:

In addition to the conservative inputs and assumptions discussed above, the base MCNP5 model used for the analysis is made as follows (with variations evaluated in the following subsections):

in order to determine the reactivity effect for the parameter of interest with a 95%

probability at a 95% confidence level, two calculations with a reference and modified__parameter are performed, and the following Equation 3.3-1 is applied, where

+/-2 x v1i2 + cr is called the 95/95 uncertainty.

1kcaic _ (1CCaIC2 _ 1caici) +/-2 X + g) Equation 3.3-1 Hi-2220020 Rev. 1 Page 6 of 11$

Criticality Safety Analysis of SFP for Callaway HOLT EC INTERN ATIONA The established maximum Lkcaic IS then either statistically combined with the other uncertainties to determine the maximum keff value or the bounding parameters value is incorporated into the design basis model.

Such bounding approach provides analysis simplicity and additional safety margin. The MCNPS design basis model is shown in Figure 3-1. Additional details and analysis methodology discussions are provided in each subsection below.

3.3.1 Design Basis Fuel Assembly Design The Callaway SFP contains various fuel assembly designs. The reactivity calculations are performed for the representative fuel types in Table 5-1, which bound all variations of the fuel designs in the Callaway SFP, using the 2x2 rack model discussed in Section 3.3. The following cases are evaluated:

. Case 3.3.1.1: Westinghouse 17x17 Standard (STD);

. Case 3.3.1.2: Westinghouse 17x17 Optimized (OFA);

. Case 3.3.1.3: Westinghouse 17x17 Vantage+ (V+);

. Case 3.3.1.4: Framatome GAlA 17x17 (GAl).

The fuel assembly designs that show the highest reactivity are used in all design basis criticality calculations.

3.3.2 Fuel Assembly Parameters The reactivity effects of the fuel assembly parameters due to manufacturing tolerances are evaluated using the 2x2 rack model discussed in Section 3.3. The variation of these parameters (see Table 5-2) is d to all fresh and spent fuel assem in the 5r D The following variations of the parameters are therefore considered for the bounding fuel assembly design:

. Case 3.3.2.0: Reference case. All fuel parameters are nominal;

. Case 3.3.2.1: Minimum cladding CD;

. Case 3.3.2.2: Maximum cladding CD;

. Case 3.3.2.3: Minimum fuel rod pitch;

. Case 3.3.2.4: Maximum fuel rod pitch;

. Case 3.3.2.5: Minimum fuel pellet CD;

. Case 3.3.2.6: Maximum fuel pellet CD;

Criticality Safety Analysis of SF? for Callaway HOLT EC INTERNAT1OAL

. Case 3.32.8: Maximum fuel density;

. Case 3.3.2.9: Maximum 10B loading in the IFBA rods (spent fuel).

Separate depletion calculations are performed for Cases 3.3.2.1 through 33.2.9 so that the effect of the tolerance during depletion is accounted for. The reactivity effect of each parameter is determined using Equation 3.3-1. The maximum positive (if any) reactivity effect for each parameter is then selected and this maximum value is statistically combined with the other maximum values from every tolerance calculation to determine the combined reactivity effect of the fuel manufacturing tolerances.

3.3.3 Spent Fuel Rack Parameters The minimum neutron absorber (BORALTM) panel length is slightly larger than the active fuel length, while the distance from the bottom of a fuel assembly to the beginning of active fl

. . .. . . . I,,

ctive 3 the end of the The reactivity effects of the SFR parameters due to manufacturing tolerances are evaluated using the 2x2 rack model discussed in Section 3.3. Since a laterally infinite array of storage cells is used in the design basis calculations, a thicker stainless steel sheathing on the outside of the SFR is not included in the model, hence its manufacturing tolerances are not considered. In accordance with [3], the following variations ofthe SFR parameters are considered:

. Case 3.3.30: Reference case. All rack parameters are nominal except the BORALTM panel length and 10B loading;

. Case 3.3.3.1: Minimum storage cell ID;

. Case 3.3.3.2: Maximum storage cell ID;

. Case 3.3.3.3: Minimum storage cell pitch;

. Case 3.3.3.4: Maximum storage cell pitch;

. Case 3.3.3.5: Minimum storage cell wall thickness;

. Case 3.3.3.6: Maximum storage cell wall thickness;

. Case 3.3.3.7: Minimum sheathing thickness;

. Case 3.3.3.8: Maximum sheathing thickness; HI-2220020 Rev. I Page 8 of 11$

Criticality Safety Analysis of SEP for Callaway HOLTEC INTERNATiONAL

. Case 3.3.3.9:

. Case 3.3.3.10: Minimum poison width.

The reactivity effect of each parameter is determined using Equation 3.3-1. The maximum positive (if any) reactivity effect for each parameter is then selected and this maximum value is statistically combined with the other maximum values from every tolerance calculation to determine the combined reactivity effect of the rack manufacturing tolerances.

3.3.3. 1 BORAL Panet B4C Particte Size BORALTM is a composite of finely ground boron carbide particles dispersed in the metal matrix of pure aluminum to act as a neutron absorber. The BORAL documentation package [14]

includes the results of various inspections and tests performed for each shipment of the BORALTM material that was eventually used for fabrication of the SFRs for Callaway. Based on the results of sieve analyses, a typical distribution of the B4C particle size in BORAL is the following:

. O45im:

. 45-18O&m:

. 180-30c%tm:

. over3OO.im:

In order to investigate the reactivity effect of the B4C particle size, calculations for the heterogeneous poison panels (84C particles in aft minum r

rmd Ii

1-eterc-nene- s model of the onpan The following cases are evaluated using the 2x2 rack model discussed in Section 3.3:

. Case 3.3.3.1 .0: Reference case. Homogeneous BORAL;

. Case 3.3.3.1.1: Heterogeneous BORALTM with B4C particle size of45 rim;

. Case 3.3.3.1.2: Heterogeneous BORALTM with 84C particle size of 180 rim.

Criticality Safety Analysis of SFP for Callaway SR HOLT EC

)NTERN ATIONA L I The results are compared to estimate a difference between the homogeneous and heterogeneous model with the variable B4C particle size.

3.3.4 Spent Fuel Pool Water Temperature The criticality analysis should be performed at the most reactive SFP temperature and density

[31, and the temperature-dependent cross-section effects in MCNP need to be considered. in general, both density and cross-section effects are not necessarily the same for all storage rack scenarios, since configurations with strong neutron absorbers typically show a higher reactivity at lower water temperature, while configurations without such neutron absorbers typically show a higher reactivity at a higher water temperature. Hence for the Callaway SFRs with BORAU poison, the minimum SFP water temperature and maximum density are expected to produce the maximum reactivity condition.

Studies are performed to demonstrate the reactivity effect of the moderator temperature and density over the temperature range specified in Table 5-8 using the temperature adjusted cross-sections and S(ad3) cards. The bounding temperature is determined using the same 2x2 rack model as discussed in Section 3.3. The following studies are performed:

. Case 3.3.4.0:

. Case 3.3.4.1:

. Case 3.3.4.2:

Hi-2220020 Rev. 1 Page 10 of 11$

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL S Case 33.4.3:

The bounding moderator temperature and density using temperature adjusted cross-sections and S(a43) cards are considered in all design basis calculations.

3.3.5 FuelAssembly Radial Positioning and Orientation 3.3.5. 7 FuetAssembty Radiat Positioning A fuel assembty located in the center of a SFR cell is surrounded by equal amounts of water on all sides, and hence the thermalization of the neutrons that occur between the assembly and the poison panel, and also the effectiveness of the poison is equal on all sides. For an eccentric positioning, the effectiveness of the poison is now reduced on those sides where the assembly is located close to the cell walls and increased on the opposite sides. This creates a compensatory situation for a single cell, where the net effect is not immediately clear. However, for a group of storage cells or entire SFR, and for the condition where all assemblies are located closest to the center of this group, the fuel assemblies at the center are now located close to each other, separated by poison plates with a reduced effectiveness since they are not surrounded by water on the outer sides. This may become the dominating condition in terms of reactivity increase.

The fuel assembly radial positioning is evaluated using the 2x2 rack model discussed in Section 3.3, which evaluate more local effects, as well as larger arrays that represent an entire rack, and therefore captures global positioning effects. The following fuel radial positioning configurations are considered:

. Case 3.3.5.0: Reference case. All assemblies are centered in their fuel storage cell of the 2x2 rack model;

. Case 3.3.5.1: All assemblies in the 2x2 rack model are moved as closely to the center of the model as permitted by the rack geometry. This creates a laterally infinite arrangement of 2x2 arrays where the assemblies are close together in each 2x2 array. Note that a configuration with assemblies moved away from the center in each 2x2 array would be equivalent due to the boundary condition and is therefore not separately considered;

. Case 3.3.5.2: All assemblies in the 2x2 rack model are moved towards the same corner of the cell. This creates a laterally infinite arrangement of 2x2 arrays where the assemblies are moved towards the same corner;

. Case 3.3.5.3: All assemblies in the 8x8 rack model are moved as closely to the center of the model as permitted by the rack geometry. This essentially represents the entire SFR and therefore captures global positioning effects. A periodic boundary condition is also used on the periphery of the model.

Criticality Safety Analysis of SFP for Callaway RI.

HOLTEC INTERNATIONAL This neglects the gap between adjacent racks and is therefore conservative and simplifies model generation.

The bounding configuration is conservatively considered in all design basis calculations.

3.3.5.2 FuetAssembty Radial Orientation The rotation of the fuel assembly in the core and/or in the storage rack is possible. However, since the analyzed fuel lattices have uniform radial fuel enrichment and symmetric radial distribution of the IFBA and Gd rods, the fuel assembly orientation is expected to have a negligible effect on reactivity. Therefore, the fuel assembly orientation is not evaluated further in the report.

3.3.6 Spent Fuel Reactivity Calculation To perform the criticality evaluation for spent fuel in MCNP5, the isotopic composition of the fuel material is calculated with the depletion code CASMO5 and thenspecified as input data Assembly average isotopic compositions are extracted from the CASMO5 output files and used in the MCNP models, ** ** . * .

Criticality Safety Analysis of SFP for Callaway I...,

HOLT EC INTERNATIONAL 3.3.6. 7 Core Operating Parameters Principal operating parameters of the fuel discussed here are moderator temperature, fuel temperature, soluble boron concentration in the core, and the power density. Other parameters such as axial burnup distribution and the effect of burnable absorbers are discussed in following paragraphs. Generic studies in [16] and [17] indicate that the operating parameters that result in higher reactivities are the upper bound moderator temperature, fuel temperature, and soluble boron concentration. The power density has a comparatively small effect with no clear trend.

Also, a lower bound power density would be inconsistent with the higher fuel temperature.

Consistent with the guidance in [2] and [31, the upper bound values are therefore used for all four parameters.

To show the effect of the individual parameters and confirm that the selected values are in fact conservative, the following sensitivity studies are performed using the 2x2 rack model discussed in Section 3.3:

. Case 3.3.6.1.0: Reference case. Upper bound values are used for all parameters;

. Case3.3.6.1.1: Fuel temperature is increased by 300 K;

. Case 3.3.6.1.2: Fuel temperature is decreased by 300 K;

. Case 3.3.6.1.3: Moderator temperature is increased by 1 00 K;

. Case 3.3.6.1.4: Moderator temperature is decreased by 1 00 K; I Case 3.3.6.1.5: Soluble boron is increased by 300 ppm;

. Case 3.3.6.1.6: Soluble boron is decreased by 300 ppm;

. Case 3.3.6.1.7: Specific power is increased by 5 MW/mtU;

. Case 3.3.6.1.8: Specific power is decreased by 5 MW/mtU.

Separate depletion calculations are performed for the parameters above.

3.3.6.2 Reactivity Effect of Cooting Time Evaluations are performed to estimate the reactivity effect of cooling time using the 2x2 rack model discussed in Section 3.3. The following cooling times are considered:

. Case 3.3.62.0: Reference case. Cooling time of 0 hours0 days 0 hours 0 weeks 0 months ;

. Case 3.3.6.2.1: Cooling time of48 hours;

. Case 3.3.6.2.2: Cooling time of 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months ;

. Case 3.3.6.2.3: Cooling time of 500 hours0.00579 days 0.139 hours 8.267196e-4 weeks 1.9025e-4 months ;

Criticality Safety Analysis of SFP for Callaway HOLT EC IN TE R N AT 0N A

. Case 33.62.6: Cooling time of 10 years;

. Case 3.36.2.7: Cooling time of 20 years.

Separate depletion calculations are performed for the cooling times above.

3.3.6.3 Integrat and Removabte Burnabte Absorbers Fuel assemblies operated at Callaway can contain various forms of control components during in-core depletion, such as Pyrex, WABA, and RCCA, hereinafter referred to as the fuel inserts. All these components are inserted into the guide tubes of the assembly during depletion.

Additionally, assemblies can contain IBAs, consisting of neutron absorbing material mixed into the fuel pellet (Gadolinia) or added as a coating on the fuel pellet (ZrB2). Below, each of these devices is briefly described, and its reactivity effect is characterized. At the end of this subsection, the approach taken in the burnup credit evaluation is outlined.

3.3.6.3.1 Burnable Poison Rods The rods contain a certain amount of 10B, in the form of Al203-B4C or 5i02-B203 in annular pellets inside a Zircaloy or SS cladding. Axially, the poisoned area is smaller than the active fuel length (see Table 5-5), and it is axially centered. There are different versions of these components with a different amount of °B, which is achieved by varying the number of rods. At the end of the first fuel cycle the 10B is practically depleted, and the component is usually removed from the assembly for the subsequent cycles.

The detailed studies [18] have been performed on the reactivity effect of BPRs. The results of these studies show that the presence of the burnable poison rods results in an increase of the reactivity of the assembly. This is a result of the reduction of water in the assembly (the poison rods replace the water usually present in the guide tubes) and the presence of the neutron absorber, which both cause a hardening of the neutron spectrum, thereby increasing the plutonium production which in turn increases reactivity. The longer the poison rods remain in the assembly, the larger is the resulting increase in reactivity. However, if the poison rods are removed after the first cycle, which is usually the case, the increase in reactivity is limited, with a maximum of 0.012 t2k reported for the studies in [18], compared to an assembly with guide tubes filled with water.

3.3.6.3.2 Rod Cluster Control Assemblies Control rods consist of highly neutron absorbing material inside the SS cladding and they are used for short term reactivity control in the core. Two different RCCA types were utilized in the Callaway reactor core. Specifically, the reactor operation up through Cycle 3 was controlled using the RCCAs made of Hafnium-Zirconium (Hf-Zr), while all subsequent and future cycles utilize the RCCAs made of Silver-Indium-Cadmium (Ag-In-Cd). They are connected to a control rod drive which allows axial movement of the RCCA during the reactor operation.

Criticality Safety Analysis of SFP for Callaway RI..

HOLT EC IN TER N ATION A L TypicaUy,at full power, mostRCCAsare completelywithdrawn from the 3.3.6.3.3 Integral Burnable Absorber IBAs are integral to the fuel rods, and therefore do not replace water in the guide tubes.

Consequently, the spectrum hardening effect of the IBAs during irradiation, and therefore the reactivity effect, is significantly lower compared to the fuel inserts. The impact of burnable absorbers on reactivity has been studied extensively in [23] and the results show that in many cases the reactivity effect is negative, i.e., reducing the reactivity of the assembly. Specifically, it is concluded that for U02-Gd203 rods, the criticality evaluations may conservatively neglect the presence of the IBAs by assuming non-poisoned equivalent enrichment fuel [3]. For IFBA rods, a small positive reactivity effect is identified in [23], with a maximum tXk of 0.01.

3.3.6.3.4 Approach Used in the Burnup Credit Evaluation To confirm the potential reactivity effects of integral and removable burnable absorbers applicable to Callaway fuel, several studies are performed using the 2x2 rack model discussed in Section 3.3 for selected cases where the fuel inserts and/or IBAs are explicitly modeled in the depletion analyses, so that the spent fuel composition transferred to the MCNP criticality calculation (without any residual absorber) contains the effect of the burnable absorbers.

The specific usage of the fuel inserts and IBA at Callaway is considered in accordance with Paragraph 4.2.1 of [3], as follows:

Criticality Safety Analysis of SFP for Callaway HOLTEC JNTERNATIONM.

The conditions above bound all potential and hypothetical reactivity effects resulting from the integral and removable burnable absorbers. The following cases are evaluated:

. Case 3.3.6.3.0: Reference case. No IBA and inserts (empty guide tubes filled with water);

. Case 3.3.6.3.1: Pyrex rods;

. Case 3.3.6.3.2: WABA rods;

. Case 3.3.6.3.3: RCCA Ag-In-Cd rods (partial insertion);

. Case 3.3.6.3.4: RCCA Hf-Zr rods (partial insertion);

. Case 3.3.6.3.5: 104 IFBA rods;

. Case 3.3.6.3.6: 200 IFBA rods;

. Case 3.3.6.3.7: WABA rods and 104 IFBA rods;

. Case 3.3.6.3.8: WABA rods and 200 IFBA rods.

Separate depletion calculations are performed for the cases above. The bounding configuration is conservatively considered in all design basis calculations.

3.3.6.4 Axial Burnup Distribution Irradiated Fuel Assemblies are not burned evenly over the height of the assembly. Rather, they exhibit an axial burnup distribution, i.e., the burnup of the fuel is a function of the axial location of the fuel within the assembly. In general, the fuel at the top and bottom end of the assembly shows a lower burnup than the fuel in the axial center of the assembly. This is caused by the creased neutron loss and therefore decreased neutron flux towards the top and bottom end of HI-2220020 Rev. 1 Page 16 of 718 Copyright © 2022 Hottec International, ott tight5 reserved

Criticality Safety Analysis of SFP for Callaway iii**

HOLT EC INTERN ATION AL the assembly during irradiation in the reactor core. The reactivity of spent fuel is a strong function of the fuel burnup, with the reactivity decreasing when the burnup increases. For irradiated fuel assemblies, the reactivity at the top and bottom ends is therefore higher than the reactivity in the center of the assembly. Obviously, no axial burnup distribution is applicable in the analysis of fresh fuel. However, when credit is taken for the reduction in reactivity due to the burnup of the fuel, it is important that the axial burnup distribution is accounted for in a conservative way. Therefore, bounding axial burnup profiles need to be established, i.e., axial profiles which maximize the reactivity under the given conditions.

There is no direct or theoretical method to establish a bounding axial burnup profile for a given assembly at a given average burnup. Since the plant-specific axial burnup profiles are not available from the Callaway unit operation, bounding profiles are established based on Subsection 6.E.4.1 of [15] by analyzing databases that contain profites for a large number of assemblies from different plants. The source of profiles is the axial burnup database documented in [241 developed by Yankee Atomic Engineering Corporation (YAEC) and the available axial burnup distributions documented in the CRC [25]. From this database, assembly profiles for the Westinghouse 17x17 fuel type, which is identical or similar to those used at Callaway, are selected for determining the bounding axial burnup profile. The combined total number of profiles is 1 034 for the Westinghouse I 7x1 7 assembliesw 1 -

A A%

235U at ki,rr of 2.1 53.5

/mtU.

I. The example bounding axial burnup for WE 17x17 fuel generated for several burnup points are provided in Table 3-6. Additionally, the bounding axial burnup profiles established in NUREG/CR-6801 [26] and presented in Table 3-7 have been considered.

The calculations are performed to demonstrate the reactivity effect of the axial burnup distribution, using the 2x2 rack model discussed in Section 3.3. The following cases are evaluated:

. Case 3.3.6.4.1: Uniform burnup profile;

. Case 3.3.6.4.2: Bounding WE 1 7x1 7 profile (Table 3-6);

. Case 3.3.6.4.3: Bounding NUREG profile (Table 3-7).

The axial burnup profile that shows the highest reactivity is used in all design basis criticality calculations, unless noted otherwise.

Although the bounding profiles are based on a large number of assembly profiles, it is possible that there are some existing or future assemblies that might be outside the bounds of these databases. However, due to the large number and variety of profiles in these databases, any HI-2220020 Rev. 1 Page 17 of 118 Copyright © 2022 Hottec InternationaL ott rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL assembly exceeding the bounding profile would be considered a rare exception. Furthermore, for all assemblies in the SFR it is assumed that they have the bounding axial burnup distribution.

To have an adverse effect on reactivity it would be necessary that the SFR contains a few of these exceptional assemblies, close to each other, and that all other assemblies in the SFR have the bounding burnup distribution. This is extremely unlikely. Therefore, these databases are considered to be sufficient for the determination of the bounding axial profiles and the profiles established in [1 5] and [26] are applicable for the burnup credit in the Callaway SFP.

3.3.6.5 Reactivity Effect ofDeptetion Related FuetAssembty Geometry Changes During irradiation in light water reactors the fuel assembly undergo small physical changes associated with irradiation and residence time in an operating reactor. Some of those changes are clad thinning due to fuel rod growth and creep, fuel densification, grid growth, and crud buildup on the outside surface of the fuel rod. These fuel assembly geometry changes can affect the neutron spectrum during depletion by changing the fuel to moderator ratio. In the SFP, the effect during depletion may lead to a different isotopic composition and the fuel geometry change can impact reactivity also by the change in the fuel to moderator ratio. These fuel geometry changes are accounted for as follows:

Criticality Safety Analysis of SF? for Callaway 11111 HOLT EC tNTERNATIONAL The calculations are performed to determine the reactivity effect of the fuel geometry changes using the 2x2 rack model discussed in Section 3.3. The following studies are performed:

. Case 33.6.5.0: Reference case. All fuel parameters are nominal;

. Case 3.3.6.5.1 : Fuel rod growth and creep;

. Case 3.3.6.5.2: Grid growth.

Separate depletion calculations are performed for the cases above so that the effect of these changes during depletion is accounted for. The results of the calculations are considered as the bias and bias uncertainty, rather than the uncertainty only, to determine the maximum keff value.

Therefore, the maximum positive (if any) reactivity effect is treated as bias and the 95/95 uncertainty ofthe bias is statistically combined with the other uncertainties.

3.3. 6.6 Spent Fuet l5otopic Content Uncertainty 3.3.6.6.1 Depletion Uncertainty To ensure that CASMO5 produces reliable and predictable results, an uncertainty on the irradiated fuel isotopic composition (i.e., the number densities) equal to 5% of the reactivity decrement is considered in accordance with [2] and [3]. Specifically, the depletion uncertainty is determined using the following Equation 3.3-2, i.e., by multiplying 5% with the reactivity difference (at 95%/95%) between the MCNP calculation with spent fuel at the minimum burnup requirement (i.e., for each point along the burnup versus enrichment curve) and a corresponding MCNP calculation with fresh fuel at the same fuel enrichment.

2 1 dept 1 ) xO.O5Equation3.3-2 I- -I 9 X i* 2 I caic caic I ( 2 where caIc calculated keffvalueforspentfuel; calc2 calculated keff value forfresh fuel; cli - standard deviation of calculated keff value for spent fuel; G2 - standard deviation of calculated keff value for fresh fuel.

The following calculations are performed using the 2x2 rack model discussed in Section 3.3:

. Case 3.3.6.6.1.1: Reference case. Spent fuel with an upper bound burnup that covers the expected burnup requirement for a given enrichment is conservatively considered;

. Case 3.3.6.6.1.2: Fresh fuel of the same enrichment without IBA is used instead of the spent fuel composition.

H1-2220020 Rev. I Page 19 of 118 Copyright C 2022 Hottec Internatwnat oil rights reserved

Criticality Safety Analysis of SFP for Callaway HOLT EC INTERNATIONAL The established depletion uncertainty covers alt uncertainties associated with depletion, such as uncertainty in computation of the isotopic inventory by the depletion code, uncertainty in cross-sections (both actinides and fission products), etc.

33.6.6.2 Burnup Uncertainty The uncertainty of the recorded burnup value is typically less than 5%. in accordance with [3],

an uncertainty of 5% is conservatively used. The following calculations are performed using the 2x2 rack model discussed in Section 3.3:

. Case 3.3.6.6.2.1: Reference case. Spent fuel with an upper bound burnup that covers the expected burnup requirement for a given enrichment is conservatively considered;

. Case 3.3.6.6.2.2: Spent fuel of the same enrichment, but the fuel burnup is 5% lower than the fuel burnup in the reference case.

The burnup uncertainty is determined using Equation 3.3-1 and included in the analysis. An additional margin for burnup uncertainty is therefore not necessary for the verification that a fuel assembly can be placed in a designated storage location.

3.3.6.6.3 MAFP Validation Table 3-5 provides a spent fuel isotopic composition credited in the criticality calculations, where all the major actinides are bolded, while the remaining nuclides (except oxygen) are considered as the minor actinides and fission products. Since the adequate critical experiment data is not available for the MAFP nuclides, a bounding bias value which is 1 .5% of the worth of the minor actinides and fission products is conservatively applied in accordance with [27] and

[28]. This bias is determined using the following Equation 3.3-3, i.e., by multiplying 1.5% with the reactivity difference (at 95%/95%) between an MCNP calculation with the major actinides only and an MCNP calculation with all credited actinides and fission products.

2)

MAFP2 ( çalc I xO.015 Equation 3.3-3 2

cak)+2X ( 2 where CQICI calculated keffvaluefor spentfuelwith allactinides and fission products; calc2 calculated keffvalueforspentfuel with the majoractinidesonly; 01 - standard deviation of catc1 a - standard deviation of calc2 HI-2220020 Rev. 1 Page 20 of 118 Copyright C 2022 Hottec International, alt rights reserved

Criticality Safety Analysis of SFP for Callaway S*SII HOLTEC INTERNATIONAL The following calculations are performed using the 2x2 rack model discussed in Section 3.3:

. Case 3.3.6.6.3.1: Reference case. Spent fuel with an upper bound burnup that covers the expected burnup requirement for a given enrichment is conservatively considered;

. Case 3.3.6.6.3.2: Spent fuel of the same enrichment and burnup, but all minor actinides S

and fission products are removed from the isotopic composition.

Since this term is conservatively applied as a bias, no additional uncertainty needs to be applied.

According to [271, an upper value of 1.5% of the worth is applicable for the spent fuel isotopic compositions consisting of all nuclides in the SFP configuration. Particularly, the MAFP bias estimate is applicable to the current analysis because the computer code, cross-section library as well as the fuel assembly and SFR cell designs are similar to those considered in [27] and [28].

3.3.7 Design Basis Calculations 3.3. 7. 7 Catcutation of a Maximum kff Vatue Applying all the considerations from the previous sections, the calculated keff value (kcaic) IS determined using the design basis model, as summarized in Figure 3-2. The maximum keff value is then determined using Equation 3.3-4, i.e., by adding the total correction factor, which includes all the biases and uncertainties, as summarized in Figure 3-3.

max = + Equation 3.3-4 e?tr catc where caic CalcUlatedkeffvalue,asdeScribedinFigure32, TCF - total correction factor, as described in Figure 3-3.

The TCF is the addition of all biases and the statistical combination of the uncertainties.

Combining the uncertainties statistically is acceptable since they are all independent. For calculations with borated water, the appropriate MCNP5 code bias and bias uncertainty associated with borated water (see Paragraph 3.2.2.1) are applied. The determined maximum keff values are used to show compliance with the regulatory limit.

3.3. 7.2 Determination of the Spent Fuet Loading Curve As discussed in Chapters 1.0 and 2.0, the approach used in this report takes credit for soluble boron under normal conditions. Under this approach, the limiting condition is the non-borated condition and the multiplication factor (keff), including all biases and uncertainties at a 95-percent confidence level, should not exceed 1 .0 for the pool flooded with unborated water.

Conservatively, a target value of 0.995 is used for the maximum keff when determining the burnup vs. enrichment curves for the loading configurations with spent fuel.

Criticality Safety Analysis of SFP for Callaway I*SRI HOLT EC INTERNATIONAL For establishing the loading curves, a two-step process is used. The first step is the generation of the curves as the polynomial functions for each loading region with spent fuel, and the second step is the validation of these curves for the applicable region and loaded content. This approach minimizes the overall number of required calculations, since it only requires a limited number ofcalculations to generate the curves.

For each loading region that includes spent fuel assemblies (see Chapter 1.0), for a given spent fuel cooling time, and selected enrichment values, two calculations with different burnups (upper and lower bound with a span of 5 GWd/mtU) are performed using the 2x2 rack model discussed in Section 3.3. Note that the case with the upper bound burnup has been already used as the reference case in the calculations for depletion/burnup uncertainty and MAFP validation.

Interpolations of the results are performed to determine the burnup that ensures that the target keff S not exceeded. The minimum required burnups are then matched by a third-order polynomial fit as a function of enrichment.

33. 7.3 Maximum keff Catcutation with Borated Water As discussed above, the approach used in this report takes credit for soluble boron under normal conditions. To ensure that the effective neutron multiplication factor (keff) 5 less than the regulatory limit with the storage racks fully loaded with fuel of the highest permissible reactivity and the pool flooded with borated water at a temperature corresponding to the highest reactivity, the calculation with the soluble boron content of 500 ppm is performed for Region 2 using the 2x2 rack model discussed in Section 3.3. Calculations for Region 1 are not made since it does not require the soluble boron credit under normal conditions. The determined maximum keff values are used to show compliance with the regulatory limit. A discussion ofthe boron dilution accident is provided in Subsection 3.6.8.

3.4 Spent Fuel Rack Interfaces With a single type of the SFR, two loading regions (see Chapter 1 .0) and different loading curves, there are four interface conditions that need to be considered in the Callaway SFP:

. Interfaces between different SFRs;

. Interfaces between storage racks and the SFP wall;

. Interfaces ofdifferent regions within a rack;

. Interfaces ofthe same region within a rack.

3.4.1 interlaces between different SFRs I The number of neutron absorber panels between assemblies across any interface between racks is therefore larger than the one analyzed in the design basis model HI-2220020 Rev. 1 Page 22 of 118 Copyright © 2022 Hottec International, ott rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERN ATtONA L (a laterally infinite arrangement of storage cells). This increased number of absorber panels, together with the water gap between racks, would reduce the reactivity at the periphery of the racks, and possibly for entire rack. However, for simplification and conservatism, these gaps and the corresponding potential reduction in reactivity are neglected, and rack cells are always assumed to be in a laterally infinite configuration. Hence no additional calculation of any rack to rack interface is required.

3.4.2 Interlaces between StoraQe Racks and the SFP Wall I As for the rack to rack interface discussed in the previous subsection, the neutron leakage, in this case without another face-to-face assembly, would reduce the reactivity. Again, for simplicity and conservatism, this effect is neglected, hence no additional calculation of any rack to wall interface is required.

3.4.3 Region 1 to Region 2 Interface Three configurations of an interface between Region 1 and Region 2 are evaluated, as follows:

The simplest interface between Region 1 and Region 2 is the straight-line interface between the two regions, where each fresh assembly on the interface line faces a spent fuel assembly across the interface, and each spent fuel assembly on the interface line faces either a fresh assembly or an empty cell across the interface. This configuration is principally shown in Figure 3-5 (b).

This interface is implemented as follows, as shown in the radial cross section of the MCNP model in Figure 3-4:

Since the reactivity of an infinite Region 1 area is very low, this interface is dominated by Region 2, and the results will approach the results for the infinite Region 2 configuration if interfacing of fresh and spent assemblies do not have an overall detrimental effect on reactivity.

Calculations will verify that such a detrimental effect does not occur.

The following calculation is performed to qualify this transitional pattern:

. Case 3.4.3.1: Straight interface of Region 1 and Region 2.

Criticality Safety Analysis of SFP for Callaway HOLT EC INTERNATIONAL However, only qualifying this pattern would be very restrictive since it would only qualify such straight interfaces. This is specifically problematic since the rack-to-rack gaps are conservatively neglected in their effect on reactivity (see previous subsection), hence the straight line would have to continue through the entire pool. That is not a practical approach, options are needed for corners of Region 1 areas facing Region 2 areas, and vice versa. In such situations, a single fresh assembly could now face two spent assemblies, or a single spent fuel assembly could face two fresh assemblies, and that is not covered by the straight-line model.

Additionally, since the reactivity of the Region 1 configuration is fairly low, additional Region 1 to Region 2 interfaces may be acceptable, such as placing individual spent fuel assemblies between the fresh assemblies in the Region 1 pattern. However, in the interest of clarity and HI-2220020 Rev. I Page 24 of 118 Copyright © 2022 Holtec international, alt rights reserved

Criticality Safety Analysis of SFP for Callaway IlK II HOLT EC INTERNATIONAL simplicity, no such configuration is evaluated or qualified, and this is also to be excluded. Again, see Subsection 3.4.6 for the approach taken for implementing this exclusion.

3.4.4 Region 1 to Region 1 Interface Since the reactivity of the Region 1 configuration is fairly low, it may be possible to have additional patterns, in addition to the checkerboard, where two fresh assemblies may be placed face-adjacent to each other. An example of such a pattern is shown in Figure 3-5 (a). However, in the interest of clarity and simplicity, no such configuration is evaluated or qualified.

3.4.5 Region 2 to Region 2 Interface This configuration contains only spent fuel that is adjacent to each other (see Figure 3-5 (e)).

These fuel assemblies are stored under the different Region 2 loading curves based on the cooling times. However, these different cooling times are compensated by the appropriate fuel burnup requirements, which ensure that the calculated keff values remain similar. Further evaluation of any Region 2 to Region 2 interface is therefore not necessary.

3.4.6 Combined Qualifications.

Defining the permissible configurations consistent with the discussions and limitations in the subsections abovejust in terms of Region 1, Region 2, corners, and exclusions would potentially result in ambiguous descriptions, or descriptions that could easily be misinterpreted. Therefore, a different approach is taken, where the permissible content of any rack cell is defined purely on the basis of the content of the face-adjacent cells. The resulting set of definitions is presented in Appendix B, Section B-4.O. Not only does it define and qualify the interfaces consistent with all discussions above, it also implicitly defines the infinite arrangement of Region 2 (uniform spent fuel) and Region 1 (checkerboard of fresh assemblies and empty cells), without the need to use the terms uniform or checkerboard. This avoids the ambiguity of those terms, which are known to have caused problems in the past. In other words, the set of rules in Appendix B, Section B-4.O, is a complete and unambiguous set of rules for the placement of fuel in the spent fuel pool, and no other rules are needed beyond those.

3.5 Normal Conditions The normal conditions considered in the analyses are all those conditions that can normally occur with fuel assembly in the SFP. The normal locations of fuel in the SFRs according to the analyzed cases and patterns are evaluated in Subsection 3.3.7 and Section 3.4. Other normal conditions are discussed in the following subsections.

3.5.1 Fuel Movement Operations.

Fuel movement procedures govern the movement and inspection of the fuel at all times that the fuel is onsite. The fuel assembly is always moved above the SFRs and never moved along the side of the SFR. The fuel assembly placed on a fuel elevator in the Cask Loading Pit or on the fuel transfer system cart for transporting fuel into containment is located at a reasonable HI-2220020 Rev. 1 Page 25 of 118 Copyright © 2022 Hottec InternationaL ott rights reserved

Criticality Safety Analysis of SFP for Callaway II*RR HOLT EC NTERNATtONAL distance away from the SFRs to preclude a criticality concern [19]. All fuel movement operations involve a single fuel assembly that is never in close enough proximity (i.e., directly adjacent) to any other fuel assembly. Therefore, a single fresh fuel assembly in water bounds all situations during normal fuel movement in the pool. Based on previous experience, the reactivity of a single fresh PWR fuel assembly in unborated water is below 0.95 and bounded by reactivity of the array of assemblies in the SFR, hence this condition is considered to be bounded by the design basis calculations, and no further evaluations are required.

3.5.2 Fuel Insertion and Removal Operations Within each loading pattern, the reactivity is maximized by the fact that the axial sections that dominate in reactivity are aligned between neighboring assemblies. For example, for spent fuel assemblies, the dominating area is a low burned upper section of the active region. Since the calculations for the loading regions with face adjacent spent fuel utilize identical assemblies, those dominating regions are perfectly aligned. The same is true for the loading regions with fresh fuel, though the dominating area is in the middle part of the active region with the lowest neutron leakage. When one assembly is being removed from the rack, this alignment is locally disturbed, i.e., the dominating regions are no longer aligned between the assembly that is being removed and the surrounding assemblies, hence the reactivity is reduced.

Also, in case of a partially loaded fuel assembly (e.g., fuel assembly reconstitution), some fissile material in the SFR cell is replaced with water. This increases the neutron moderation and, eventually, increases the effectiveness of the surrounding thermal neutron absorber panels. This way, due to the reduced amount of fissile material and the increased neutron absorption, the reactivity of the SFR during the insertion/removal operation is reduced, and it is always bounded by the fully loaded condition. The exposed end of the partially loaded fuel assembly is surrounded by a large volume of water, hence effectively neutronically decoupled from the SFR contents. Therefore, no further evaluations are required.

3.5.3 Storage of Fuel Rod Storage Rack The purpose of the FRSR is to collect and store individual fuel rods extracted from other fuel assemblies. Typically, the FRSR contains a limited number of storage cells at a regular square or hexagonal array with the lattice pitch, that is larger than the fuel rod pitch in the PWR assembly.

Since the maximum number of fuel rods in the FRSR is well bounded by the number of rods in the fuel assembly, the amount of fissile material in the FRSR and its reactivity is expected to be significantly lower.

Criticality Safety Analysis of SFP for Callaway HOLT EC INTERNATJONA L The MCNP5 model of the SFR with the FRSR is shown in Figure 3-6.

It should be noted that the purpose of this analysis is to demonstrate that the reactivity of the SFR loaded with the FRSRs in a bounding configuration is substantially lower than the bounding reactivity determined for any of the qualified loading regions. Hence the available margin is well sufficient to offset any potential uncertainties related to the FRSR tolerances, and no attempt is made to quantify them. The discussion in Subsection 3.5.2 is also applicable to the FRSR.

3.5.4 Storage of Fuel Assemblies with Missing Rods Several fuel assemblies have undergone partial reconstitution (i.e., removing part or whole fuel rod without replacing it with a stainless-steel dummy rod). The fuel lattices of such assemblies are provided in Section 5.8. Since a loss of the fuel pin increases the amount of moderator in the undermoderated PWR assembly, a small increase in reactivity is expected. To ensure that the available safety margin is sufficient to offset a potential reactivity effect of the missing rods, the calculation is performed for each fi

the r

rods * . . 1

.__ J : c Conn ...i f

During fuel assembly reconstitution activities, a larger number of fuel rods can be potentially removed as well as the different layouts of the missing rods can appear, in comparison with the lattices in Section 5.8. Near the center of the assembly lattice, the removal of a rod increases the moderation level for adjacent rods and results in an increase in reactivity, while closer to the edge of the assembly, the removal of a rod increases moderation near the thermal neutron poison panels and, in many cases, decreases the reactivity. With the increase in the number of removed t -- - +k. 4 I When the fuel reconstitution is performed in Region 1, there is plenty of margin to offset a reactivity increase due to reconstitution with no limit on the number of missing rods.

Therefore, fuel assembly reconstitution activities are restricted to the Region 1 configuration, and further evaluations are not required.

3.5.5 Storage of Low-Burned Fuel Assemblies The Callaway SFP inventory includes fuel assemblies that for various reasons have been discharged from the reactor core before they achieved sufficient burnup. Such assemblies may need to be loaded into Region 1 storage configurations. However, the fuel assemblies initially loaded in Cycle 1 (i.e., Westinghouse STD) are susceptible to Top Nozzle Separation failure, thus their relocation within the pool is currently prohibited. For all those assemblies, the minimum burnup requirement has been determined based on the assembly-specific enrichment and Hl-2220020 Rev. 1 Page 27 of 118 Copyright © 2022 Hottec InternationaL att rights reserved

Criticality Safety Analysis of SFP for Callaway ISIRI HOLT EC iNTERNATIONAL cooling time using the loading curves generated in Paragraph 3.3.7.2, and compared with the actual burnups of those assemblies. It was identified that only one fuel assembly that does not meet the burnup requirement is of Westinghouse STD design, but this fuel assembly is atready stored in the checkerboard configuration (Region 1). In summary, it is therefore concluded that the specification of Region 1 and Region 2 allows the storage of all assemblies without the need for any additional assembly-specific evaluations for low burnup.

3.6 Abnormal and Accident Conditions The following accident conditions are considered in the following subsections for the Callaway SFP:

. Loss of SFP cooling;

- . Dropped assembly resting horizontally on the SFR;

. Assembly dropped vertically into a storage cell;

. Mislocated fuel assembly (a fuel assembly in the wrong location outside the S FR);

. Misloaded fuel assembly (a fuel assembly in the wrong location within the SFR);

. Incorrect loading curve (multiple misload);

. Rack movement;

. Boron dilution.

Note that by virtue of the double contingency principle [3], two unlikely independent and concurrent incidents or postulated accidents are beyond the scope of the required analysis. This principle precludes the necessity of considering the simultaneous occurrence of multiple accident conditions.

The maximum keff value calculations performed for the accident conditions include the same total correction factors as those used for the design basis models for the normal conditions, as discussed in Paragraphs 3.3.7.1 and 3.3.7.3. Previous analyses showed that the tolerance and uncertainty calculations performed separately for accident conditions produce similar results, hence the normal condition results are considered applicable. The calculations are performed using borated water with several soluble boron concentrations, and the soluble boron requirement, that results in a reactivity equal or lower than the regulatory limit of 0.95, is interpolated between these calculations.

3.6.1 Loss of SFP Cooling Under the accident conditions (loss of cooling), the SEP water temperature could be elevated beyond the normal operating range. The reactivity effect of the SFP temperature over a range of credible values is evaluated in Subsection 3.3.4. All design basis calculations consider the bounding SFP water temperature and density. Therefore, no further calculations are necessary.

Criticality Safety Analysis of SFP for Callaway 11111 HOLTEC NTERNATIONAL 3.6.2 Droped Assembly Horizontal For the case in which a fuel assembly is assumed to be dropped on top of the SFR, the fuel assembly will come to rest horizontally on top of the rack with a minimum separation distance from the active fuel region of more than 12 inches, which is sufficient to preclude neutron coupling (i.e., an effectively infinite separation). Consequently, the horizontal fuel assembly drop accident will not result in an increase in reactivity.

3.6.3 Dropped AssemblyVertical into a Storage Cell It is also possible to vertically drop an assembly into a location that might be occupied by another assembly. Such a vertical impact would at most cause a small compression of the stored assembly, if present, or result in a small deformation of the baseplate for an empty cell.

These deformations could potentially increase reactivity. However, the reactivity increase would be small compared to the reactivity increase created by the misloading of a fresh assembly discussed in Subsection 3.6.5. The vertical drop is therefore bounded by the misloading accident and no separate analysis is performed.

3.6.4 Mislocated Fuel Assembly The fuel assembly mislocation accident could possibly occur if a fresh fuel assembly of the highest permissible enrichment (5.0 wt% 235U) is accidentally mislocated or droppçoutside of a storage rack adjacent to the other fuel assemblies. Considering that and taking into account a high neutron leakage at the edges of the storage rack, the accidental mislocation of a fresh fuel assembly outside the rack is bounded by the fresh assembly misload (see Subsection 3.6.5).

Therefore, no further calculations are necessary.

3.6.5 Misloaded Fuel Assembly As discussed in Chapter 1.0, the SFP racks are qualified for various configurations of fresh fuel assemblies, spent fuel assemblies, and empty storage cells. It is possible that a fuel assembly that is not qualified for a given loading region could accidently be placed in that region. For instance, the fresh fuel assembly may be inadvertently placed into the storage cell intended for spent fuel in the Region 2 configuration. As a bounding approach, the misload of a single fresh fuel assembly of the highest permissible enrichment (5.0 wt% 235U) is considered in a storage cell that provides the largest positive reactivity increase. The following cases are evaluated:

. Case 3.6.5.1: Misloading into an empty storage cell in Region 1;

. Case 3.6.5.2: Misloading into one of the storage cells intended to store a spent fuel assembly in Region 2.

The misload accident evaluations are performed using the model discussed in Section 3.3, but an 8x8 array of storage cells with the periodic boundary conditions is considered, which effectively represents a multiple misload (also see Subsection 3.6.6). The minimum soluble HI-2220020 Rev. i wage 29 of 118 Copyright © 2022 Hotteclnternational, ott rights reserved

Criticality Safety Analysis of SFP for Callaway 11111 HOLTEC INTERNATIONAL boron concentration is determined for each case that ensures that a maximum keffvalue does not exceed the regulatory limit.

Additionally, the misload accident evaluations are performed for Case 3.6.5.1 using the interface models discussed in Section 3.4.

3.6.6 Incorrect Loading Curve While several independent fuel assemblies misloads are precluded by the double contingency principle, a multiple misload could occur as a result of an incorrect application of the loading curves. As a bounding approach, spent fuel assemblies with the lowest burnup requirement are assumed to be accidentally loaded into all storage cells qualified for spent fuel in the loading regions with the highest burnup requirement. The following cases are evaluated:

. Case 3.6.6.1: Multiple misload of spent fuel assemblies, which were intended to be loaded into Region 2 with 20 years of cooling time, is considered for I

Region 2 with 0 hours0 days 0 hours 0 weeks 0 months of cooling time.

The incorrect loading curve accident evaluations are performed using the model discussed in Section 3.3. The minimum soluble boron concentration is determined for each case that ensures that a maximum keff value does not exceed the regulatory limit.

3.6.7 Rack Movement In the event of seismic activity, there is a hypothetical possibility that the storage rack arrays may slide and come closer to each other. In the worst-case scenario, two racks may touch each other at the baseplate, reducing the physical separation of the fuel assemblies along the rack interface, but still maintaining a minimum water gap width. The worst-case racks movement scenario for the entire SFP is when the water gap width between all SFRs is as low as allowed by the baseplate. This accident condition is bounded by the evaluations of the design basis cases discussed in Section 3.3 since the design basis models consider all the racks at their closest approach, i.e., a laterally infinite arrangement of 2x2 arrays so that the gap between the racks is neglected. Therefore, no further evaluations are necessary.

3.6.8 Boron Dilution None of the previously discussed accidents would cause a simultaneous boron dilution event.

The only hypothetical scenario is a seismic-related pipe break and rack movement. However, as discussed in Subsection 3.6.7, rack movement is bounded by the design basis model, hence there is no safety concern. Therefore, in accordance with [3], as long as the accident does not also result in a dilution of soluble boron, the analysis of a simultaneous boron dilution event is not required, per the double-contingency principle.

Significant loss or dilution of the soluble boron concentration in the SEP is extremely unlikely, however, the guidance presented in [3] requires that the boron dilution analysis should determine that sufficient time is available to detect and suppress the worst dilution event that HI-2220020Rev. 1 Page 30 of 118 Copyright © 2022 Hottec International, attrights reserved

Criticality Safety Analysis of SFP for Callaway HOLT EC INTERNATIONAL 3.7 Margin Evaluation 3.7.1 Neutron Absorber Aging Effects The SFR design in the Callaway SFP contains the BORALTM poison panels constricted in-between the steel box and steel sheathing. Industrywide, there have been no indications of a loss of BORALTM material of a nature that diminished neutron-absorbing capability [311. However, Callaway is subject to a License Renewal commitment to perform in situ areal density measurements a test method that has historically underestimated panel performance, occasionally to the point of test failure.

For the purpose of operational support of the potential of lower BORALTM poison areal density, an evaluation of the potential reactivity effect of such lower areal density, and an evaluation of available macgin in the criticality analysis to offset such effect is performed and documented in the following subsections. If an unanticipated BORALTM poison areal density is identified, this information can be utilized to demonstrate operability, and to determine what technical, operational and licensing actions may need to be taken.

HI-2220020 Rev. 1 Page3l of 118 Copyright C 2022 Holtec Internotionot, alt rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL 3.7.2 BORALTM Panel 108 Areal Density The evaluation of the reactivity effect in terms of LXk per three changes in BORALTM panel areal density: 5%, 10% and 20% reductions from the minimum allowed, is performed. For all cases, the reduction is assumed to be uniform throughout the pool. The areal densities are then matched by a second-order polynomial fit as a function of tk such that the increase can be compared to any compensatory actions or assumptions. Note that the design basis analysis is already performed with the minimum BORAL panel areal density (treated as a bias), while the nominal areal density is expected to prevait in the SFR BORAL panels, which provides additional margin.

3.7.3 CriticalityAnalysis Safety MjgIr The following calculations are performed to estimate available margins in the criticality analysis:

Criticality Safety Anatysis of SFP for Callaway HOLTEC INTERNATIONAL

. Case 3.79:

Note that no attempt is made here to quantify a negative reactivity associated with presence of the residual IBA in the spent fuel isotopic composition. Also, as discussed in Paragraph 3.3.7.3, only 500 ppm of soluble boron is credited for the normal conditions, which is significantly lower than a typical soluble boron content in the SEP (Table 5-8).

3.8 Permitted Future Fuel Assemblies The criticality analysis documented in this report qualifies all currently stored and/or known future fuel assembly designs. As discussed in Subsection 3.3.1, the bounding fuel design is determined and used in all design basis calculations. In the future, new assembly designs may need to be qualified that have not been explicitly addressed by the criticality analysis in this report. In general, the qualification of these new assembly designs is governed by the criteria in the Callaway technical specification (summarized in Appendix B). While a change of the fuel assembly array configuration and/or instrument/guide tube patterns is not expected, since its not typical for PWR, any such change as well as a change of the geometric dimensions and material compositions, which are important to criticality but not bounded by the design basis model, would require an additional evaluation.

Criticality Safety Analysis of SEP for Callaway HOLTEC INTERNATIONAL Table 3-1 Summary of Area of Applicability of the MCNP5 Benchmark Parameter Design Application Benchmarks [13]

Fissionable Material Isotopic Composition 235u/u, wt% I Pu/(U÷Pu), wt%

Physical Form I

Fuel Density, g/cm3 I Moderator Material (Coolant)

Physical Form Density, g/cm3 Reflector Material Physical Form I Density, 9/cm3 LI 1 Reflector 1 I I

Absorber and Separating Material Soluble I

Criticality Safety Analysis of SFP for Callaway ImRI HOLT EC NTERNATIO NAL Table 3-2 MCNPS Benchmark Analysis for Various Fuel and Water Subsets of Experiments No. of Bias Normality Residuals Experiment Description Bias1 Linear Correlation exp. Uncertainty2 Normality, x2 (Pu(x2;d)) (Pd(f;d))

All experiments I I

AU except those with Gadolinium, Cadmium and Lead3 I Fresh U02 Fuel with Fresh Water Fresh U02 Fuel with ZLJ iZ LE I

Borated Water I HTC + MOX Fuel with Fresh Water HTC + MOX Fuel with Borated Water j

Criticality Safety Analysis of SFP for Callaway iii*

HOLTEC INTERN ATIONA Table 3-3 Significant Trending Analysis for Callaway Parameters Experiment . . Analysis Analysis Parameter

. . Linear Correlation Description Parameter Value Trend Bias Fresh U02 Fuel with Fresh Water HTC + MOX Fuel with Fresh Water HTC + MOX Fuel with Borated Water 1 The maximum or minimum parameter value that provides the most negative bias is used. The positive bias values are conservatively neglected.

Criticality Safety Analysis of SFP for Callaway VIII.

HOLTEC INTERNATIONAL Table 3-4 Summary of MCNP5 Code Validation Bias and Bias Uncertainty Applicable Pure Water BoradWater Description Loading

Bias , Bias Regions Bias Bias Uncertainty Uncertainty Fresh Fuel I I I

SpentFuel 2 U[

I I 1

The values in parentheses are based on trending analyses in Table 3-3.

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATtONAL List of Spent Fuel Isotopes1 MCNPZAID[8]

I I I I I I I I *I I I

FFF*HLz:+/-ELi:

I 1 I I

I I I

E I I I zr z*

I I

i: z z: J: ::z. Ltz:.J I F--

I HH I I I II I I i_i .zEJET I I I I

.1

¶ETLJ I

I I

1 Deleted 3

The isotopes considered as the major actinides are bolded [281.

H[-2220020 Rev. I Page 38 of 11$

CrIticality Safety Analysis of SFP for Callaway HOLTEC INTERNATiONAL Table 3-6 Bounding Axial Burnup Profiles for Westinghouse 17x17 Fuel Type [15]

Assembly Average Burnup (GWd/mtU)

Axial Segment (18 = Top) 73 1 1 7.5 f

275 j 37.5 1

45 Relative Burnup per Segment1 I I 2

3 4

5 6

7 I I 8 I I 9 I 10 I I 11 I I 12 I I 13 I 14 I 15 I 16 17 I

I EEZ:

18 I I I

Segment burnup divided by assembly average burnup.

Criticality Safety Analysis of SFP for Callaway HOLT EC NTERNATJONA L Table 3-7 Bounding Axial Burnup Profiles from NUREG/CR-6801 [26]

1 urnuange (GWd/mtU) 46 14246

> 38-42 34-38 30-34 26-30 22-26 18-22 14-78 10-14 6-10 < 6 I 0.582 0666 0.660 0.648 0.652 0.619 0.630 0.668 0.649 0633 0.658 0.631 0.920 0.944 L 0.936 0.955 0.967 024 0.936 1 .034 1 .044 0.989 1 .007 1.007 3 1.065 1.048 1.045 1.070 1.074 1.056 1.066 1150 1.208 1.019 1.091 1135 1.105 1.081

+/- 1.080 1.104 1.103 1.097 1.103 1.094 1.215 0.857 1.070 1.133 1.113 1.089 1.091 1.112 1.108 1.103 1.108 1.053 1.214 0.776 1.022 1.098 6 1.110 1.090 1.093 1.1 12 1.106 1.101 1.109 1.048 1208 0.754 0.989 1.069 1.105 1.086 1.092 1.108 1.102 1.103 1.112 1.064 1.197 0.785 L978 1.053 1.085 1.090 1.105 1.097 1.112 1.119 1.095 1.189 1.013 0.989 1.047 U

1.095 1.084 I 1.089 1.102 1.094 1.125 1.126 1.121 1.188 1.185 1.031 1.050

12. 1.091 1.084 1.088 1.099 1.094 1.136 1.132 1.135 1.192 1.253 1.082 1.060

.Li 1.085 1.088 1.097 1.095 1.143 1.135 1.140 1.195 1278 1.110 1.070 1.084 1.086 i 1.086 1.095 1.096 1.143 1.135 1.138 1.190 1.283 1.121 1.077 13 1.080 1.086 1.084 1.091 1.095 1.136 1.129 1.130 1.156 1.276 1.124 1.079 14 1.072 1.083 1.077 1.081 1.086 1.115 1.109 1.106 1.022 1251 1.120 1.073 1.050 L_ 1.069 1.057 1.056 1.059 1.047 1.041 1.049 0.756 1193 1101 1.052 16 0.992 1.010 0.996 0.974 0.971 0.882 0.871 0.933 0.614 1.075 1.045 0.996 17 0833 0.81 1 0.823 0.743 0.738 0.701 0.689 0.669 0.481 0.863 0.894 0.845 18 0.515 0.512 0.525 0.447 0.462 0.456 0.448 0.373 0.284 0.515 0.569 0.525 1

AxIal Segment (18 = Top)

Criticality Safety Analysis of SFP for Callaway II*II HOLTEC INTERNATIONAL Withheld from public disclosure under 10 CFR 2.390 Figure 3-1 Radial Cross-Section View of the MCNP5 Design Basis Model of the SFR HI-2220020Rev.1 Page4l of 118 Copyright © 2022 Hoitec InternationaL all rights reserved

Criticality Safety Analysis of SFP for Callaway Ri.

HOLTEC INTERNATIONAL I Bounding fuel Given enrichment Bounding COP Bounding IBA and I I assembly design (Subsection 3.3.1)

(Paragraph 33.6.1) fuel inserts (Paragraph 3.3.6.3)

I I I I .;

I I I.

CASMOS Depletion CalculatIon I I Given cooling I

I time Uniform/bounding I

I axial burnup profile (Paragraph 3.3.6.4) 1 I

I

¶ Spent fuel isotopic I average burnup compositions - - . -.

I .

I

[iJl

]

Bounding fuel Bounding SFR Bounding assembly Bounding SFP assembly design parameters radial positioning temperature (Subsection 3.3.1) (Section 3.3) (Subsection 3.3.5) (Subsection 3.3.3.1)

Bounding fresh fuel enrichment L I I I Unborated (or borated) SFP (Section 3.3) MCNPS CrIticality moderator L.._ Calculation ii Infinite array of SFR storage cells (Section 3.3)

Criticality Safety Analysis of SFP for Callaway HOLT EC NTERNATONAL Withheld from public dscIosure under 10 CFR 2.390 Figure 3-3 Determination of the Total Correction Factor HI222OO2ORev. 1 Page43 of 118 Copyright © 2022 Hottec internationaL attrights reserved

Criticality Safety Analysis of SFP for CaUaway IIII*

HOLTEC INTERNATIONAL Withheld from public disclosure under 10 CFR 2.390 Figure 3-4 Radial Cross-Section View of the MCNP5 Model for the SFR Interfaces HI-2220020 Rev. 1 Page 44 of I 18 Copyright © 2022 Holtec InternationaL att rights reserved

Criticality Safety Analysis of SFP for Callaway HOLT EC INTERNATIONAL Withheld from public disclosure under 10 CFR 2.390 Figure 3-5 Potential Interfaces between the Loading Regions H1-2220020 Rev. 1 Page 45 of 118 Copyright © 2022 Holtec InternationaL ott rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTER N ATIONAL Withheld from public disclosure under 10 CFR 2.390 Figure 3-6 Radial Cross-Section View of the MCNP5 Model for the FRSR Ht-2220020 Rev. 1 Page 46 of I 18 Copyright © 2022 Hottec InternationaL allrights resered

Criticality Safety Analysis of SFP for Callaway 11111 HOLTEC HJTERN ATIONAL Withheld from public disclosure under 10 CFR 2.390 Figure 3-7 MCNPS Model of the Heterogeneous BORALTM Panel HI-2220020 Rev. 1 Page 47 of 118 Copyright © 2022 Hottec InternationaL ott rights reserved

Criticality Safety Analysis of SFP for Callaway I....

HOLT EC INTERNATIONAL 4.0 ASSUMPTIONS A number of assumptions, either for conservatism or to simplify the calculation approach are applied in the analyses. Each assumption is appropriately discussed and justified in the text.

Bounding or sufficiently conservative inputs and assumptions are used essentially throughout the entire analyses, and as necessary, studies are presented to show that the selected inputs and parameters are in fact conservative or bounding. For additional details, a reader is referred to Section 33.

While the fuel assembly and SFR models used in the analyses are very detailed (see Section 3.3),

to assure that the true reactivity will always be less than the calculated reactivity, the following conservative design criteria and simplifications are made:

Criticality Safety Analysis of SFP for Calbway HOLT EC INTERNATIONAL

Assumption, Approach C, or R Justification (Note 1) 6 I I 7 I I 8 I 9 I 10 J I I

11 I

Note 1 C stands for Conservative, and R stands for Reasonable.

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL 5.0 INPUT DATA 5.1 Fuel Assembly Designs The Callaway SFP is designed to accommodate various PWR fuel assembly designs, such as Westinghouse 17x17 Standard (STD), Westinghouse 17x17 Optimized (OFA), Westinghouse 17x17 Vantage 5 (V5), Westinghouse 17x17 Vantage+ (V+), and Framatome GAlA 17x17 (GAl).

The PWR fuel assembly data used in the analysis is presented in Table 5-1 through Table 5-3.

5.2 Core Operating Parameters As discussed in Paragraph 3.3.6.1, the upper bound core operating parameters (conservative) for all Caltaway Unit 1 cycles are used for fuel depletion calculations performed with CASMOS. Core operating parameters are presented in Table 5-4.

5.3 Integral Burnable Absorber and Fuel Inserts During the Callaway reactor operation, some fuel assemblies have made use of fuel inserts, namely Pyrex, WA8A and RCCA. Additionally, assemblies can contain integral burnable absorbers, consisting of neutron absorbing material mixed into the fuel pellet (Gadolinia) or added as a coating on the fuel pellet (Zt82).

The burnable absorber rods contain a certain amount of 108, in the form of A1203-B4C or 5i02-B203 in annular pellets inside a Zircaloy or SS cladding. The control rods consist of highl r

material inside the SS cladding. Specifically, the reactor operation I

1 using the RCCAs made of Hafnium-Zirconium (Hf-Zr), while I utilize the RCCAs made of Silver-Indium-Cadmium (Ag-In-Cd).

The design specifications for the Pyrex, WABA, and RCCA devices are provided in Table 5-5.

tBAs are integral to the fuel rods, and therefore do not replace water in the guide tubes.

Consequently, the spectrum hardening effect of the IBAs during irradiation, and therefore the reactivity effect, is significantly lower compared to the fuel inserts. The design specifications for the Gd and IFBA rods are shown in Table 5-6.

Criticality Safety Analysis of SFP for Callaway HOLTEC I N T E R N AT I 0 N A L 5.4 Spent Fuel Rack Design The SFP contains a single type of BORALTM SFR Uesi9ned for storage of PWR fuel assemblies.

The SFR storage cells are composed of SS boxes with a single fixed neutron absorber panel centered on each side, attached by SS sheathing. The 55 boxes are arranged in an alternating pattern and connected in a rigid structure such that the connection of the box corners form storage cells between them. Neutron absorber panels are also installed on all exterior walls of the SFR.

Figure 5-2 and Figure 5-3 provide a sketch of the storage rack in the radial and axial direction respectively. The SFR design data used in the analysis is presented in Table 5-7.

5.5 SFP Operating Parameters The SFP operating parameters are presented in Table 5-8.

5.6 Material Compositions The material compositions for the principal design components of the fuel assemblies and SFRs are listed in Tabte 5-9. The MCNP nuclide identification number (ZAID), presented for each nuclide in Table 5-9, includes the atomic number and mass number, which are consistent with the ZAIDs used in the benchmarking calculations documented in [13j. The appropriate temperature-specific cross-section library identifier (i.e., ZAID.identifier) is used with all ZAIDs in the MCNP model (see Subsection 3.3.4).

57 Fuel Rod Storage Rack The FRSR parameters are presented in Table 5-10.

5.8 Fuel Assemblies with Missing Rods The fuel lattices for the fuel assemblies with the missing rods are taken from [19] and [1], and presented in Figure 5-4.

Criticality Safety Analysis of SFP for Callaway HOLTEC ENTERN ATIONA L Table 5-1 Specification of the Fuel Assembly Parameters [20]

Westinghouse Westinghouse Westinghouse Framatome Fuel Assembly Design STD OFA V+7 GAIA{21]

j Fuel Assembly Data Fuel Rod Array 1 7x1 7 Number of fuel rods 264 Distance from Bottom of Fuel J

Assembly to Beginning of Active Length,_inches Active Fuel Length, inches Fuel Rod Pitch, inches AxialBlanket Length, inches I If j

J I Fuel Rod Data Clad CD, inches Clad ID, inches Clad Material Pellet ID, inches I I 1 Pellet OD, inches I As-Built U02 Density (Max %TD)

I I Guide/Instrument Tube Data Number of Guide Tube I

Guide Tube OD, inches Guide Tube ID, inches Guide Tube Material I

Number of Instrument Tube Instrument Tube CD, inches I

Instrument Tube lD, inches I

Instrument Tube Material I

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL Table 52 PWR 1 7x1 7 Fuel Assembly Manufacturing Tolerances

j Reference Fuel Rod Pitch, inches [201 Pellet OD, inches [20], [21]

Clad CD, inches

[21]

I. .

Fuel Enrichment, wt% 235U [20],_[21]

Fuel Density, %TD [20], [21]

ZrBCoangLoading, % I I [20]

Table 5-3 - PWR I 7x1 7 Fuel Assembly Depletion Related Geometry Changes I

I Parameter Maximum. Fuel Rod Growth, inches I Value

[21J I ----------

L 1 t Maximum Fuel Grid Growth, inches [20]

I Bounding values for all fuel assembly types are summarized.

[-11-2220020 Rev. 1 Page 53 of 11$

Criticality Safety Analysis of SFP for Callaway IIR*

HOLTEC INTERNATIONAL Table 5-4 Core Operating Parameters Parameter Maximum Core Moderator Temperature, K

[ Value J Reference

[21]

I-I Maximum Fuel Temperature, K [20]

L I

Reactor Specific Power, W/gU [20]

Soluble BoronConcentraon(cycleaverage)pprn [19]

Criticality Safety Analysis of SFP for Callaway iis*

HOLT EC NTERN AT 0 N A L Table 5-5 Specification of the Fuel Inserts [20]

Parameter Hf-Zr Ag-In-Cd Pyrex WABA (RCCA) (RCCA)

MaximumNumber of Rods per Assembly1 Maximum insertion Depth2, inches Burnable Absorber Material Absorber Content, wt%

Burnable Absorber Density, 9/cc I

Burnable Absorber Composition, wt%

Si 0

10B I I B

Al C ,

Inner Clad Material j

Inner Clad ID, inches lnner Clad OD, inches 1--

Burnable Absorber ID, inches

. f.---

Burnable Absorber CD, inches

.---- L. I - I----

1 Outer Clad Material

...- ..----.- --L -

.1 Outer Clad ID, inches I

Outer Clad OD, inches I- I Burnable Absorber Length, inches 1

See Figure 5-1 for the fuel inserts layouts.

2See

rikR HI-2220020 Rev. 1 PageSS of 118 Copyright © 2022 Hottec InternationaL ott rights rese,ved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL Table 5-6 Specification of the Integral Burnable Absorbers Parameter I Value IFBA Rods [20]

ZrB2 Coating Loading, mg 1°B/inch 10B Enrichment of ZtB2, wt%

Number of the IFBA rods IFBA Stack Length, inches IFBA Rods Layout See Figure 5-1 Burnable Absorber Composition See Table 5-9 Gd Rods [21]

Gadotinia Loading, wt% Gd203 Number of the Gd rods Gd Stack Length, inches Gd Rods Layout See Figure 5-1 Burnable Absorber Composition See Table 5-9 Ht-2220020 Rev. 1 Page 56 of 118 Copyright © 2022 Hottec InternationaL all rights resetved

Criticality Safety Analysis of SFP for Callaway I*IRI HOLTEC INTERNATJONA L Table 5-7 SpecificationoftheCallaway SFR Parameters Parameter Value (1], [29], [321, [33]

J Rack Type Number of Racks I

-I Storage Rack Material Rack Height (Top of Baseplate to Top of Rack),

inches Distance from Rack Baseplate to Bottom of Neutron Absorber, inches Storage Cell ID, inches I

Storage Cell Pitch, inches I

Storage Cell Box Wall Thickness, inches Inner SheathingThickness, inches

}

Peripheral Sheathin9 Thickness, inches z -4 Neutron Absorber Panel

...-----....-..-----.---.----. . ,---.-.---.1-_ .

I Type

- - I I

Thickness, inches 1

Width, inches

--. --..--...-.. . . . . --- [ .

Length, inches BArealDensi(g/cm2 Hl-2220020 Rev. 1 Page 57 of 11$

Criticality Safety Analysis of SFP for Callaway HOLTEC iNTERNATIONAL Table 5-8SfPOperating Parameters [1 9], [29], [34], [35]

-- Parameter Value Maximum Moderator Temperature, °F Soluble Boron Concentration, ppm Minimum Water Level (Volume) in the SFP, inches

-;; Volume above theSFRs2 gal Water Volume in theRMWST(Oppm),gal Soluble Boron Concentration in the RWST, ppm TOtaICCW System Volume,gaI . ....,.

MaxLrnum Blow-Down Rate, gpm . - - . ,

ProbableMaxth,umPredpitation3, gprn ,

Maximum Operator Response lime for Internal Flooding Events, mm SFP Boron Concentration Surveillance Interval, days I

Annunciator Setpoint for Low SFP Level (Volume), inches I

Annunciator Setpcnt for High SFP Level (Volume), inches SFPWater Overflow Level, inches

[

Criticality Safety Analysis of SEP for Callaway HOLTEC 1NTERNATIOtiAL Table 54 Material Compositions of the Major Design Components Element

_J_- MCNP ZAID [8]

J Weight Fraction Stainless Steel (Density 7.84 g/cm3) 24050 0.0079050 24052 0.1585266 Cr 24053 0.01 83218 24054 0.0046467 Mn 25055 0.0200100 26054 0.0389826 26056 0.6345800 Fe 26057 0.0149174 26058 0.0020200 28058 0.0671977 28060 00267760 Ni 28061 0.0011834 28062 0.0038348 28064 0.0010082 Zirconium (Density 6.55 g/cm3) 40090 0.5070612 40091 01118009 Zr 40092 , 0.1 727810 40094 0.1789110 40096 0.0294379 BORALTM( . .

I I 5010 B

1 BORALTM material calculated density based on the nominal panel thickness and minimum °8 loading.

Criticality Safety Analysis of SFP for Callaway 11111 HOLTEC INTERNATIONAL Table 5-9 Material Compositions of the Major Design Components Element _

j -

a ZAID [8]

Pure Water (Density f WeightFraction 1 .0 glcm3) 1001 0.1118854 H --

1002 0.0000257 8016 0.8857957 0 ..,. ... - .

8017 0.0022932 Borated Water (500 ppm, Density 1 .0 g/cm3) 1001 0.1118300 H - -- --_

1092_ 0.0000257 8016 0.8853540 0 -......---.-----

8017 0.0022921 5010 0.0000922 8 . . ..( .

5011 0.0004078 Borated Water (1000 ppm, Density 1.0 g/cm3) 1001 0.1117740 H

1002 0.0000257 8016 0.8849110 0 ,,,,

8017 0.0022909 5010 0.0001843 B . ., .. .. . ..

5011 0.0008157 I I 5010 B ..,.... ... - .....

Criticality Safety Analysis of SFP for Caflaway Is..

HOLT EC INTERNATIONAL Table 5-9 Material Compositions of the Major Design Components Element j MCNP ZAID [8]

Fresh U021 (5.0 wt% 235U, Density f Weight Fraction 10.6312 glcm3) 92235 0.0440800 U

92238 0.8374200 0 8016 0.1185000 Fresh UOz-GdzO,1 (5.0 wt% 235U, I 92235 U

92238 0 8016 64752 64154 64155 Gd 64156 64157 64758 64160 1

The design basis case is provided as an example; other fresh fuel compositions may be used.

Criticality Safety Analysis of SFP for Callaway RIIR HOLTEC NTERNATIONAL Table 5-10 Fuel Rod Storage Rack Parameters AEy__

Parameter I

t-Value [19]

p of_Storage Tubes Storage Tube CD fliches Storage Tube Thickness, inches

.I I

Criticality Safety Analysis of SFP for Calbway IIIRI HOLTEC INTERNATIONAL Withheld from public disclosure under 10 CFR 2.390 Figure 5-7 Considered PWR 1 7x1 7 Fuel Assembly Layouts HI-2220020 Rev. I Page 63 of 118 Copyright © 2022 Hottec International, ott tights reserved

Criticality Safety Analysis of SEP for Callaway HOLTEC NIER N A1 0 NA L Withheld from public disclosure under 10 CFR 2.390 Figure 5-2 Planar CrossSection of the Callaway SFR HI-2220020 Rev. 1 Page 64 of 118 Copyright © 2022 Hottec InternationaL all rights reserved

Criticality Safety Analysis of SF? for Calbway HOLTEC N T E R N ATt0 N A L Withheld from public disclosure under 10 CFR 2.390 Figure 5-3 Axial Cross-Section of the Callaway SFR Ht-2220020 Rev. 1 Page 65 of 118 Copyright C 2022 Holtec International, all rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERN AT 0NA L Withheld from public disclosure under 10 CFR 2.390 Figure 5-4 Fuel Assembly Layouts with Missing Rods 1-11-2220020 Rev. 1 Page 66 of 118 Copyright © 2022 Hottec International, allrights reserved

Criticality Safety Analysis of SFP for Callaway I...

HOLTEC NT E R N ATt 0 N A 6.0 COMPUTER PROGRAMS Hoftec International maintains an active list of QA validated computer codes on the Companys network, hereinafter referred to as the ACPL, that are approved for use in safety significant projects. The table below identifies the Code and its version (listed in the ACPL) that has been used in this work effort. For additional details, a reader is referred to Section 3.2.

Generic Report & ACPL Information Generic Report# Hl-2104750, Hl-21 15064 Code name (fisted in the ACPL) CASMO5 MCNP5 Python SX Code version # (approved in the ACPL)

Code name and versions used in previous 2.08.00 j 1.51 J 1.0 revisions of the report (if different than listed N/A above)

All calculations were performed on computers under Windows at Holtecs offices.

Criticality Safety Analysis of SFP for Callaway HOLTEC NTEFNAT 0NAt 7.0 CALCULATIONS AND RESULTS As discussed in Section 3.3 of the main report, the analysis is performed using a combination of bounding analysis parameters and statistical uncertainties. The analysis results and discussions are provided in each section below.

7.1 Design Basis Fuel Assembly Design As discussed in Subsection 3.3.1, all representative PWR fuel designs are evaluated in the Caltaway SFR. In accordance with [3], the evaluations for all storage configurations listed in Chapter 1.0 are performed. Fresh fuel with the maximum fuel enrichment as well as spent fuel with enrichments of 2.0, 3.5 and 5.0 wt% 23U and fuel burnups along the expected region-specific loading curve at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months are considered. The results of the calculations are presented in Table 7-1. Westinghouse V+ fuel assembly shows the highest reactivity at zero burnup; therefore, it is used in all design basis criticality calculations for Region 1. Framatome GAl fuel assembly shows the highest reactivity at spent fuel configurations; therefore, it is used in all design basis criticality calculations for Region 2.

7.2 Reactivity Effect of Fuel Assembly Parameters As discussed in Subsection 3.3.2, evaluations are performed to determine the reactivity effect of the fuel assembly manufacturing tolerances. The bounding fuel designs established in Section 7.1 are considered in all storage configurations listed in Chapter 1.0. Fresh fuel with the maximum fuel enrichment as well as spent fuel with enrichments of 2.0, 3.5 and 5.0 wt% 235U and fuel burnups along the expected region-specific loading curve at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months are considered. The results of the evaluations are presented in Table 7-2. The maximum reactivity effect of the fuel assembly parameters is treated as an analysis uncertainty.

7.3 Reactivity Effect of SFR Parameters As discussed in Subsection 3.3.3, the SFR parameters are evaluated to determine the reactivity effect of the storage rack manufacturing tolerances. Calculations are performed for all storage configurations listed in Chapter 1.0. Fresh fuel with the maximum fuel enrichment as well as spent fuel with enrichments of 2.0, 3.5 and 5.0 wt% 235U and fuel burnups along the expected region-specific loading curve at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months are considered. The results of the evaluations are presented in Table 7-3. The maximum reactivity effect of the storage rack parameters is treated as an analysis uncertainty.

7.3. 1 The calculations are performed for all storage configurations listed in Chapter 1.0 to estimate a reactivity effect of the heterogeneous BORALTM panel model with the variable B4C particle size, as discussed in Paragraph 3.3.3.1. Fresh fuel with the maximum fuel enrichment as well as spent fuel with enrichments of 2.0, 3.5 and 5.0 wt% 235U and fuel burnups along the expected region-HI-2220020 Rev. 1 Page 68 of 118 Copyright © 2022 Hotteclnternotionat, alt rights reserved

Criticality Safety Analysis of SFP for Callaway Is..

HOLTEC I N T E R N AT 0 N A L specific loading curve at the -.j time of 0 rs are con Ta 7-26 c ?mons:rate 7.4 Reactivity Effect of SFP Water Temperature As discussed in Subsection 3.3.4, the reactivity effect of SEP water temperature and density is evaluated. Calculations are performed for all storage configurations listed in Chapter 10. Fresh fuel with the maximum fuel enrichment as well as spent fuel with enrichments of 20, 3.5 and 5.0 wt% 235U and fuel burnups along the expected region-specific loading curve at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months are considered. The results of the evaluations are presented in Table 7-4 and show that the bounding temperature (and corresponding density) are the minimum temperature and maximum density. Therefore, these values are used in all design basis calculations.

7.5 Reactivity Effect of Fuel Assembly Radial Positioning As discussed in Subsection 3.3.5, the reactivity effect of the fuel radial location is evaluated.

Calculations are performed for all storage configurations listed in Chapter 1.0. Fresh fuel with the maximum fuel enrichment as well as spent fuel with enrichments of 2.0, 3.5 and 5.0 wt% 235U and fuel burnups along the expected region-specific loading curve at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months are considered. The results of the evaluations are presented in Table 7-5, and show that the reference case, i.e., all assemblies centered in their fuel storage cell of a 2x2 array, is bounding. Therefore, the bounding radial position of the fuel assemblies is included in the design basis calculations, and incorporation of the bias and bias uncertainty for the reactivity effect of fuel radial positioning into the TCF is not necessary.

7.6 Spent Fuel Reactivity Calculation 7.6.1 Reactivity Effect of Core Operatinç Parameters As discussed in Paragraph 3.3.6.1, a sensitivity study is performed on the effect of the core operating parameters on the fuel composition in the uniform loading of spent fuel assemblies (Region 2). Fuel enrichments of 2.0, 3.5 and 5.0 wt% 235U and fuel burnups along the expected region-specific loading curve at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months are considered. The results of the calculations are listed in Table 7-6 and confirm that higher moderator and fuel temperature and higher soluble boron concentration result in higher reactivity, while the power density has a small effect. Therefore, conservative high values are used for all parameters in all design basis calculations.

7.6.2 Reactivity Effect of Cooling Time As discussed in Paragraph 3.3.6.2, a sensitivity study is performed on the effect of cooling time on the fuel composition in the uniform loading of spent fuel assemblies (Region 2). Fuel HI-2220020 Rev. 1 Page 69 of 118 Copyright © 2022 Hottec Internationat, att rights reserved

Criticality Safety Analysis of SFP for Callaway I..

HOLTEC INTERNATONA L enrichments of 2.0, 3.5 and 5.0 wt% 235U and fuel burnups along the expected region-specific loading curve (0 hours0 days 0 hours 0 weeks 0 months ) are considered. The results of these calculations are presented in Table 7-7 and confirm that the reactivity decreases with the cooling time.

7.6.3 Reactivity Effect of ISA and Fuel Inserts As discussed in Paragraph 3.3.6.3, a sensitivity study is performed on the effect of the IBA and fuel inserts on the fuel composition in the uniform loading of spent fuel assemblies (Region 2).

Fuel enrichments of 2.0, 3.5 and 5.0 wt% 235U and fuel burnups along the expected region-specific loading curve at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months are considered. The results of the calculations are presented in Table 7-8.

I Hence more abundant and representative WABA inserts arejustified for the design basis depletion calculations.

Due to a common RCCA operation with a low-depth insertion of the control rods during the full power operation, the reactivity effect of the Ag-in-Cd rods though positive at higher burnups is well bounded by the effect of WABAs. Also, considering a shorter height of the IFBA stack in comparison with the active fuel height (due to cutback regions) and low-depth insertion of the Ag-In-Cd rods, an impact of these absorbers during irradiation mostly occurs in different axial regions, hence bounded by The reactivity effect of the Hf-Zr RCCA (

The comparison of the BA configurations with 104 and 200 IFBA rods shows that the latter is bounding.

In accordance with [3],

Criticality Safety Analysis of SFP for Callaway HOLTEC NrERNATIONAL 7.6.4 Reactivity Effect of Axial Burnup Profiles As discussed in Paragraph 3.3.6.4, the reactivity calculations are performed for a comparison of the axially constant burnup and the axial burnup profiles in Table 3-6 and Table 3-7 in the uniform loading of spent fuel assemblies (Region 2). Fuel enrichments of 2.0, 3.5 and 5.0 wt% 235U and fuel burnups along the expected region-specific loading curve at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months are considered. The results of the calculations are listed in Table 7-9. As expected, the WE 17x17 profile is bounding or equivalent in all cases. Therefore, the bounding axial burnup profile (WE 17x17) is used to determine the loading curves, as described in Paragraph 3.3.7.2. Nevertheless, both the bounding axial profile and flat profile are considered in the confirmatory calculations described in Subsection 7.7.2 and in the interface analysis in Section 7.8.

7.6.5 Reactivity Effect of Depletion Related Fuel Assembly Geometry Changes As discussed in Paragraph 3.3.6.5, the reactivity effect of the depletion related fuel geometry changes is evaluated for spent fuel in Region 2 with enrichments of 2.0, 3.5 and 5.0 wt% 35U and fuel burnups along the expected region-specific loading curve at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months .

The results of the evaluations presented in Table 7-10 are considered as bias and bias uncertainty for determination of the maximum keff value. The maximum positive (if any) reactivity effect is treated as bias and the 95/95 uncertainty of the bias is statistically combined with the other uncertainties.

7.6.6 Spent Fuel Isotopic Content Uncertainty The depletion uncertainty calculations, burnup uncertainty calculations and MAFP validation calculations are performed for spent fuel in Region 2, as discussed in Subparagraph 3.3.6.6.1 through Subparagraph 3.3.6.6.3, respectively. Specifically, the fuel enrichments from 2.0 to 5.0 wt% 235U in increments of 0.5 wt% and fuel burnups along the expected region-specific loading curve at various cooling times are considered. The results of these calculations are presented in Table 7-1 1.

7.7 Design Basis Calculations As discussed in Paragraph 3.3.7.1, various evaluations have been performed for all storage configurations listed in Chapter 1.0 to determine the bounding set of parameters, biases and bias uncertainties for the design basis modef. Based on the results of these evaluations, discussed in the previous sections, the design basis calculations for normal conditions have been performed and the TCF values are determined.

Criticality Safety Analysis of SFP for Callaway *IRI HOLT NTERNAT1ONAL EC 7.7.1 Determination of the Spent Fuel Loading Curves The approach to determine the individual points of the loading curves follow the process outlined in Paragraph 3.3.7.2. For various spent fuel cooling time, calculations with different burnups are performed at the spent fuel enrichments from 2.0 to 5.0 wt% 235U in increments of 0.5 wt%. The results of the design basis calculations and TCF values used to generate the loading curves are presented in Table 7-12. Interpolations of the results are performed to determine the burnup that ensures that the target ke IS not exceeded. The minimum required burnups are then matched by a third-order polynomial fit as a function of enrichment. The resulting equations are summarized in Table 7-13, and graphically shown in Figure 7-1 in comparison with the actual Callaway fuel inventory.

7.7.2 Confirmatory Calculations To validate the loading curves, calculations are performed, considering various spent fuel cooling time, for selected fuel enrichments and burnups that are calculated from the polynomial functions. Both the bounding axial burnup profile and flat profile are considered in the loading curve confirmatory calculations, and the most reactive case is reported for each of the incremental enrichment steps. The results of the calculations are summarized in Table 7-14.

The highest maximum ke value in Table 7-14 is consistent with the target value of 0.9950, and below the regulatory limit of 1 .0 for the pool flooded with unborated water.

The results of the calculations for the checkerboard configuration of fresh fuel (Region 1) are summarized in Table 7-15, and confirm compliance with the regulatory limits for the pool flooded with unborated water. It should be noted that the maximum keff value is well below the regulatory limit of 0.95, hence no credit of the soluble boron in the SFP is applied to Region 1.

7.7.3 Mximjmkalculation wi&Brt&Water The calculations with the soluble boron credit are performed for Region 2, considering various spent fuel cooling time, for selected fuel enrichments and burnups that are calculated from the polynomial functions. Both the bounding axial burnup profile and flat profile are considered, and the most reactive case is reported for each of the incremental enrichment steps. The results of the calculations are summarized in Table 7-16. The highest maximum keff value in Table 7-16 is below the regulatory limit of 0.95 for the pool flooded with borated water.

7.8 SFR Interfaces The calculations are performed for the spent fuel rack interfaces as discussed in Section 3.4.

Fresh fuel with the maximum fuel enrichment as well as spent fuel with enrichments of 2.0, 3.5 and 5.0 wt% 235U and fuel burnups calculated using the polynomial functions are considered.

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATION AL As far as the fuel assembly positioning in the storage cells, both the cell centered and eccentric fuel positioning (i.e., where all asserr r,t,+rj1 1ritJ I The results of the calculations are summarized in Table 7-17, where the most reactive cases are reported. The TCF values for both loading regions across the interface are considered, and the maximum one is conservatively used to determine the maximum keff value. Additionally, the spatial distribution plots for the neutron flux and the total reaction rate are generated in order to identify the reactivity-dominating regions.

7.9 Normal Conditions 7.9.1 Storage of Fuel Rod Storage Rack As discussed in Subsection 3.5.3, the calculations are performed to estimate the reactivity effect of the uniform storage of the FRSRs with fresh fuel. The results of the evaluations presented in Table 7-18 confirm that the reactivity of the SFR loaded with the FRSRs is very low, hence the FRSR is qualified for storage in any SFR cells allocated for storage of the fuel assemblies, and no further calculation is necessary.

7.9.2 Storage of Fuel Assemblies with Missing Rods As discussed in Subsection 3.5.4, the calculations are performed to estimate the reactivity effect of the missing fuel pins for all lattices in Figure 5-4 with the assembly specific enrichment (conservatively rounded up to the next available enrichment in the depletion calculations) and burnup. Conservativçjy, the isotopic composition at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months is used. Since the fuel burnup of it is assumed to be stored in Region 1, while all other HI-2220020 Rev. 1 PageZ3 of 118 Copyright © 2022 Hottec Internotionat, ott rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERN ATIO NA assemblies are considered in Region 2. The results of the evaluations presented in Table 7-19 confirm that the reactivity of the SFR loaded with the fuel assemblies with the missing rods is below the regulatory limits, hence these assemblies are qualified for storage in the appropriate SFR cells.

7.10 Accident Conditions 7.10.1 Misloaded Fuel Assembly As discussed in Subsection 3.6.5, the calculations are performed for all storage configurations in Chapter 1.0 to estimate the reactivity effect of a single fresh fuel assembly misload and determine the minimum required soluble boron concentration in the SFP. Fresh fuel with the maximum fuel enrichment as welt as spent fuel with enrichments of 2.0, 3.5 and 5.0 wt% 235U and fuel burnups calculated using the polynomial functions at the cooling time of 0 hours0 days 0 hours 0 weeks 0 months and 20 years are evaluated. Both fuel radial positioning configurations, i.e., where all assemblies are cell centered and all assemblies are moved towards the misloaded assembly as permitted by the rackgeornetry, are considered. Additional calc d to the r activity Several calculations at 500, 1000 and 1500 ppm of soluble boron are performed, and the bounding results used for interpolation of the minimum soluble boron concentrations are summarized in Table 7-21.

7.1 0.2 lncorrect Loading Curve As discussed in Subsection 3.6.6, the calculations are performed to estimate the reactivity effect of an incorrect application of the loading curves and determine the minimum required soluble boron concentration in the SFP. The uniform spent fuel loading (Region 2) is evaluated at the maximum enrichment of 5.0 wt% 235U and 0 hours0 days 0 hours 0 weeks 0 months cooling time, but the spent fuel composition is based on the lowest burnup from the loading curve for 20 years of cooling time (see Subsection 3.6.6).

Several calculations at 500, 1000 and 1500 ppm of soluble boron are performed, and the bounding results used for interpolation of the minimum soluble boron concentrations are summarized in Table 7-22.

7.10.3 Boron Dilution The low and high flow rate boron dilution accident scenarios are analyzed using information in Table 5-8, following the methodology described in Subsection 3.6.8. The results of the boron dilution analysis are presented in Table 7-23.

Hl-2220020 Rev. 1 Page 74of 118 Copyright C 2022 Hottec InternationaL alt rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL Therefore, a boron dilution event resulting in an SFP boron concentration reduction from the technical specification limit to the minimum required concentration established in Paragraph 3.3.7.3 is not considered credible.

Criticality Safety Analysis of SEP for Callaway 11111 HOLTEC NTERNATIONA L 7.7 1 Margin Evaluation The BORALTM degradation and margin evaluation that is used in this report is described in detail in Section 3.7. The calculations are performed for all storage configurations at the maximum fuel enrichment of 5.0 wt% 235U and spent fuel burnup (if applicable) that is calculated from the polynomial functions for 0 years cooling time. This case is bounding and applicable to other combinations of the spent fuel enrichment and minimum required burnup that have a larger margin to the regulatory limit.

The results of the calculations for various GORALTM panel °B areal densities as well as the final polynomial fits for the areal density as a function of Lk are summarized in Table 7-24, and graphically shown in Figure 7-4.

The results for various margins inherent in the criticality analyses are presented in Table 7-25.

The total mar9in for each

ed cc

r I of

The results indicate that potentially significant amounts of margin may be available to address conditions with a reduced BORALTM panel 10B areal densities (up to 20% reduction from the minimum areal density). This may help with operational considerations should such reduction be identified.

Criticality Safety Analysis of SFP for Callaway RRI**

HOLTEC N T E R N AT 0 N A Table 7-1 Bounding Fuel Assembly Design Withheld from public disclosure under 10 CFR 2.390 1-11-2220020 Rev. 1 Page 77 of I 18 Copyright 0 2022 Holtec !nternationa4 ott rights resenied

Criticality Safety Analysis of SFP for CaHaway IRRIl HOLTEC INTERN ATIONAL Table 7- Reactivity Effect of Fuel Assembly Parameters Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. 1 Page 78 of 118 Copyright C 2022 Hottec InternationaL all rights reserved

Criticality Safety Analysis of SFP for Callaway HOLT EC

)NTERNAflONAL Table 7-3 Reactivity Effect of SFR Parameters Withheld from public disclosure under 10 CFR 2.390 HI222OO2ORev. I Page79 of 11$

Criticality Safety Analysis of SFP for Callaway IRII HOLTEC INTERNATI0NAL Table 7-3 Reactivity Effect of SFR Parameters Withheld from public disclosure under JO CFR 2.390 H(-2220020Rev. I Page 80 of 118 Copyright © 2022 Holtec Internationat, all rights reserved

Criticality Safety Analysis of SFP for Callaway 11111 HOLTEC NTERNATtONAL Table 7-4 Reactivity Effect of SIP Water Temperature Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. 1 Page 81 of 118 Copyright © 2022 Hottec InternationaL att rights reserved

Criticality Safety Analysis of SFP for Callaway HOLT EC HJ T ER N ATION AL Table 7-5 Reactivity Effect of Fuel Assembly Radial Positioning Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. 1 Page 82 of I 18 Copyright C 2022 Hottec InternationaL ott rights reserved

Criticality Safety Analysis of SFP for Callaway *IIII HOLTEC INTERNATION AL Table 7-6 Reactivity Effect of Core Operating Parameters Withheld from public disclosure under 10 CFR 2.390 H12220020 Rev. 1 Page 83 of 118 Copyright © 2022 Hottec Internationat. ott rights reserved

Criticality Safety Analysis of SFP for Callaway *IRI HOLTEC INTERNATIONAL Table 7-7 ReactivityEffectofCooling Time Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. 1 Page 84 of 118 Copyright © 2022 Hottec InternationaL all rights reserved

Criticality Safety Analysis of SFP for Callaway IRI*I HOLTEC INTERNATIONAL Table 7-8 Reactivity Effect of Irradiation with thelBAand Fuel Inserts Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. I Page 85 of 118 Copyright © 2022 Holtec InternationaL ott tights reserved

Criticality Safety Analysis of SFP for Callaway 11111 HOLT EC 1NTE R N AT 0N A L Table7-9 Reactivity Effect of Axial Burnup Profile Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. I Page 86 of 118 Copyright © 2022 Hottec International, at! rights reserved

Criticality Safety Analysis of SFP for Callaway 11111 HOLT EC INTERNATIONAL Table 7-1 0 Reactivity Effect of Depletion Related FuelAssembly Geometry Changes t-J Withheld from public disctosure under 10 CFR 2.390 HI-2220020 Rev. 0 Page87 of 118 Copyright © 2022 Holtec internationaL alt rights reserved

Criticality Safety Analysis of SF? for Callaway HOLT EC LNTERNATIONAL

_:!:?ie:71 1 Determination of Depletion Uncertainty, Burnup Uncertaintyand MAE? BIaSJ Withheld from pubtic disclosure under 10 CFR 2.390 HI-2220020Rev.1 Page88oIll8 Copyright © 2022 Hottec InternationaL ati rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC I N T E R N A T 0 ti A L Table 7-1 1 Determination of Depletion Uncertainty. Burnup Uncertainty and MAFP Bias Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. 1 Page 89 of 118 Copyright © 2022 Holtec International, oil rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC NTERNATIONAL Table 7-12 Summary of the Analysis for Region 2 (Spent Fuel)

Withheld from public disclosure under 10 CFR 2.390 H1-222ÜO2ORev.1 Page9Ooffl8 Copyright C 2022 Hottec InternatIonaL ott rights reserved

Criticality Safety Analysis of SFP for Callaway 11111 HOLTEC INTERNATIONAL Table 7-12 Summary ofthe Analysis for Region 2 (Spent Fuel)

Criticality Safety Analysis of SFP for Caltaway lIRIR HOLTEC INTERNATIONAL Table 7-1 2 Summary of the Analysis for Region 2 (Spent Fuel)

Criticality Safety Analysis of SFP for Callaway III*

HOLTEC INTERNATIONAL Table 7-12 Summary of the Analysis for Region 2 (Spent Fuel)

Criticality Safety Analysis of SFP for Callaway HOLTEC NTERNATIONAL Table 7i 2 Summary of the Analysis for Region 2 (Spent Fuel)

Criticality Safety Analysis of SFP for Catlaway IIRR*

HOLTEC iNTERNATIONAL Table 7-1 3 Summary of the Loading Curves for CaHaway SFP Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. 1 Page 95 of I 18 Copyright © 2022 Hottec InternationaL alt right5 reserved

Criticality Safety Anatysis of SFP for Callaway SISIS HOLTEC NTERNATIONA L Table 7-14 Loading Curves Confirmatory Calculations Withheld from public disclosure under 10 CFR 2.390 1-11-2220020 Rev. 1 Page 96 of 118 Copyright © 2022 Hottec International, ott rights reserved

Criticality Safety Analysis of SFP for Callaway HOLT EC INTERNATIONAL Table 7i 5 Summary of the Analysis for Region 1 (Fresh Fuel)

Criticality Safety Analysis of SFP for Callaway *IIII HOLTEC INTERN ATION AL Table 1! -SummaryoftheAnalysisforNormalConditionswithSolubleBoronCredit Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. I Page 98 of 1 18 Copyright © 2022 Holtec International, at! rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC IN TERN AT 0 N A L Tabte7-17 Summary of the Analysis for the SFR Interfaces Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. 1 Page 99 of 118 Copyright © 2022 Hottec Internationat, at! rights re5erved

Criticality Safety Analysis of SFP for Callaway HOLTEC INEERNAflONAL Table 7-1 8 Summary of the Analysis for the FRSR Withheld from pubtic disclosure under 10 CFR 2.390 HI-2220020 Rev. 1 Page 100 of 118 Copyright © 2022 HottecinternotionaL all rights reserved

Criticality Safety Analysis of SFP for Caflaway *SIRR HOLTEC INTERNATIONAL Table 7-19 Summary of the Analysis for Fuel Assemblies with Missing Rods Withheld from public disclosure under 10 CFR 2.390 HI-2220020Rev. 1 Page 101 of 118 Copyright © 2022 Hottec InternationaL ott rights reserved

Criticality Safety Analysis of SFP for Callaway 11111 HOLTEC INTERN ON AL Table 7-21 Maximum keff Calculation for the Fuel Misload Accident Withheld from public disclosure under 10 CFR 2.390 HI-2220020Rev.1 Page lO3of 11$

Criticality Safety Analysis of SFP for Callaway HOLT EC INTERNATtONAL Table 7-21 Maximum keff Calculation for the Fuel Misload Accident Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. I Page 1 O4of I 18 Copyright © 2022 Hottec Internationat, all rights reserved

Criticality Safety Analysis of SFP for Callaway *SIR*

HOLTEC INTERNAT(ONA L Table 7-21 Maximum keff Calculation for the Fuel Misload Accident Withheld from public disclosure under 10 CFR 2.390 HI-2220020 Rev. 1 Page 105 of 11$

Criticality Safety Analysis of SFP for Callaway *RRIS HOLTEC INTERNATIONAL Table 722 Maximum keff Calculation for the Incorrect Loading Curve Accident Withheld from public disclosure under 10 CFR 2.390 HI-2220020Rev.1 Page lO6of 118 Copytight C 2022 Hottec InternationaL ati rights reserved

Criticality Safety Analysis of SFP for Caliaway HOLTEC N T ER N ATt 0 N A L Table 723 SFP Boron Dilution Accident Analysis Withheld from public disclosure under 10 CFR 2.390 1-11-2220020 Rev. 1 Page 107 of 118 Copyright © 2022 Holteclnternationat, all rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC N T E F? N AT 0 N A L Table 7-24 Reactivity Effect of the BORALTM Panel B Areal Density Withheld from public disclosure under 10 CFR 2390 Ht-2220020Rev.1 PagelO8of 118 Copyright © 2022 Hottec international, all rights reserved

Criticality Safety Analysis of SFP for Cattaway HOLT EC N T E F? N A T 0 N A L Table 725 Margin Evaluation Withheld from public disclosure under 10 CFR 2.390 H1-2220020 Rev. I Page 109 of 118 Copyright © 2022 Hottec International, all rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL Table 7-26 Reactivity Effect of the B4C Particle Size Withheld from pubtic disclosure under 10 CFR 2.390 HI-2220020Rev. 1 PagellOof I 18 Copyright © 2022 Hottec InternationaL all rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC NTERNATIOtJA L Withheld from public disclosure under 10 CFR 2.390 Figure 7-1 Loading Curves for Uniform Loading of Spent Fuel Assemblies (Region 2)

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL Withheld from public disclosure under 10 CFR 2.390 Figure 7-2 Total Reaction Rate Distribution for Region 1 to Region 2 Interface Withheld from public disclosure under 10 CFR 2.390 Figure 7-3 Total Reaction Rate Distribution for Region 1 (2x2) to Region 2 Interface HI-2220020 Rev. 1 Page 112 of 11$

Criticality Safety Analysis of SFP for Callaway 11111 HOLTEC INTERNATIONAL Withheld from public disclosure under 10 CFR 2.390 Figure 7-4 BORALTM Panel 10B Areal Density as a Function of k HI-2220020 Rev. 1 Page 113 of 118 Copyright © 2022 Holtec International, ott rights reserved

Criticality Safety Analysis of SFP for Callaway IS*IR HOLTEC tNTERNATIONAL

8.0 CONCLUSION

The criticality safety analyses have been performed for the Callaway SFP that contains a single type of BORALTM spent fuel racks designed for storage of the PWR 17x17 fuel assemblies. Two storage configurations listed in Chapter 1.0, including uniform loading of spent fuel assemblies with various cooling times and a checkerboard configuration of fresh fuel assemblies and empty storage cells, have been qualified using the bounding fuel assembly designs Framatome GAl and Westinghouse V-i-, respectively, with fuel enrichment up to 5.0 wt% 35U. All credible normal and accident conditions have been analyzed, and the key conclusions are provided below.

For the fresh fuel assemblies in Region 1 under normal conditions, the effective neutron multiplication factor (keff) of the SFP loaded with fuel of the highest anticipated reactivity, at a temperature corresponding to the highest reactivity, is less than 0.95 for the pool flooded with unborated water with 95% probability at a 95% confidence level, in accordance with 10 CFR 50.68(b)(4).

For spent fuel assemblies in Region 2 under normal conditions, considering various cooling times, the minimum required burnups as a function of enrichment (a third-order polynomial fit) have been determined and summarized in Table 7-1 3 as well as in Figure 7-1 The results of the calculations show that the effective neutron multiplication factor (keff) of the spent fuel pool loaded with fuel of the highest anticipated reactivity, at a temperature corresponding to the highest reactivity, is less than 1.0 for the pool flooded with unborated water and does not exceed 0.95 for the pool flooded with borated water (550 ppm1), all for 95% probability at a 95%

confidence level, in accordance with 10 CFR 50.68(b)(4).

Under accident conditions, the minimum soluble boron concentration of 1081.2 ppm is required to ensure that the effective neutron multiplication factor (ken) of the SFP does not exceed 0.95.

All credible interface conditions in the Callaway SFP have been considered and qualified.

Any SFR cell qualified for loading of a fuel assembly is also permitted for storage of the FRSR.

Specific Callaway fuel inventory, such as fuel assemblies with certain missing rods and low-burned fuel assemblies, have been analyzed or evaluated and qualified for storage in the SFP.

Fuel assembly reconstitution activities are restricted to a storage cell in the Region 1 configuration that is face adjacent to empty cells at all sides.

The criticality safety analysis documented in this report also provides information about the potential reactivity effect of lower BORAL panel 10B areal densities (up to 20% reduction from the minimum areal density), and about margin in the analysis to possibly offset such reduction.

1 The soluble boron requirements are increased by additional SO ppm in accordance with Paragraph 5.1.1 of [3].

H1-2220020 Rev. 1 Page 114 of 118 Copyright C 2022 Holtec internationaL att rights reserved

Criticality Safety Analysis of SFP for Callaway HOLT EC INTERNAT(ON AL The key criticality analysis parameters for Catlaway, which must be specifically tracked to ensure continual compliance with the criticality safety analysis, are summarized in Appendix B. This also includes a set of rules to be followed, in Section B-4O, to assure placement of assemblies in the racks is in accordance with the analyses presented here.

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL 91 REFERENCES

[1] Criticality Safety Analysis of Spent Fuel Storage Racks for Union Electric, Holtec International, HI-971790, Revision 4 (proprietary).

[2] Staff Guidance Regarding the Nuclear Criticality Safety Analysis for Spent Fuel Pools, US NRC, DSS-ISG-2010-O1, Revision 0.

[3] Guidance for Performing Criticality Analyses of Fuel Storage at Light-Water-Reactor Power Plants, Nuclear Energy Institute, NEI 12-16, Revision 4.

[4] Final Safety Evaluation by the Office of Nuclear Reactor Regulation Topical Report SSP P01/028-TR, Generic Application of the Studsvik Scandpower Core Management System to Pressurized Water Reactors, Office of Nuclear Reactor Regulation, US NRC, September, 2017.

[5] CASMO5/CASMO5M A Fuel Assembly Burnup Program Methodology Manual, Studsvik Scandpower, Inc., SSP-08/405, Revision 5.

[6] CASMOS A Fuel Assembly Burnup Program, Users Manual, Studsvik Scandpower, Inc.,

SSP-07/431, Revision 10.

[7] ENDF/B-VILO 586 Group Neutron Data Library for CASMO-5 and CASMO-SM, Studsvik Scandpower, Inc., SSP-07/402, Revision 5.

[8] MCNP A General Monte Carlo N-Particle Transport Code, Version 5, Los Alamos National Laboratory, LA-U R I 987 (2003, Revised 2/1/2008).

[9] ENDF/B-VIl.O Evaluated Nuclear Data Library, December 1 5, 2006.

[10] MCNPS Temperature Dependent Library Construction with NJOY, Holtec International, HI-21 56450, Revision 2 (proprietary).

[11] F. B. Brown, A Review of Monte Carlo Criticality Calcutations Convergence, Bias, Statistics, International Conference on Mathematics, Computational Methods and Reactor Physics, Saratoga Springs, NY, LA-UR-08-6558, May 3, 2009.

[1 2] Guide for Validation of Nuclear Criticality Safety Calculational Methodology, USNRC, NUREG/CR-6698, January 2001.

[1 3] Nuclear Group Computer Code Benchmark Calculations, Hottec International, Hl-21 04790, HI-2220020 Rev. 1 Page 1 1 6 of I I 8 Copyright C 2022 Holtec International, alt rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL Revision 3 (proprietary).

[14] BORAL Documentation Package, DOC-70384-3, Project 70384, Holtec International, June 1 999 (proprietary).

[1 5] Safety Analysis Report HI-STAR 1 00 Cask System, Holtec International, USNRC Docket 71-9261, H1-951251, Revision 20 (proprietary).

[1 6] Assessment of Reactivity Margin and Loading Curves for PWR Burnup-Credit Cask Designs, Oak Ridge National Laboratory, NUREG/CR-6800, ORNL/TM-2002/6, March 2003.

[1 7] M. D. DeHart, Sensitivity and Parametric Evaulations of Significant Aspects of Burnup Credit for PWR Spent Fuel Packages, Oak Ridge National Laboratory, ORNLJTM-12973, May 1996.

[18] Parametric Study ofthe Effect of Burnable Poison Rods for PWR Burnup Credit, ORNL-TM 2000/373, NUREG/CR-6761, USNRC Office of Nuclear Regulatory Research, March 2002.

[19] Ameren lnputsforCallawaySpent Fuel PoolCriticalityAnalysis, NED20220010, Ameren Missouri, February 8, 2022.

[20] Westinghouse Inputs for Callaway Spent Fuel Pool Criticality Analysis, NED2022001 2, Ameren Missouri, February 22, 2022.

[21] Inputs for Callaway Spent Fuel Pool Criticality Analysis, Framatome Fuel, FS1-0058769, Revision 2.

[22] Parametric Study ofthe Effect of Control Rods for PWR Burnup Credit, ORNL-TM-2001/69, NUREG/CR-6759, USNRC Office of Nuclear Regulatory Research, February 2002.

[23] Study of the Effect of Integral Burnable Absorbers for PWR Burnup Credit, ORNL-TM 2000/321, NUREG/CR-6760, USNRC Office of Nuclear Regulatory Research, March 2002.

[24] R. J. Cacciapouti and S. Van Volkinburg, Axial Burnup Profile Database for Pressurized Water Reactors, Yankee Atomic Electric Company Report YAEC-1 937, 1997.

[25] Summary Report of Commercial Reactor Criticality Data for McGuire Unit 1, 800000000-01717-5705-00063, Revision 1, U.S. Department of Energy, April 1998.

[26] Recommendations for Addressing Axial Burnup in PWR Burnup Credit Analyses, ORNL/TM-2001/273, NUREG/CR-6801, USNRC Office of Nuclear Regulatory Research, March 2003.

[27] An Approach for Validating Actinide and Fission Product Burnup Credit Criticality Safety Analyses Criticality (Keff) Predictions, ORNL/TM-201 1/514, NUREG/CR-7109, USNRC Office HI-2220020 Rev. 1 Page 117 of 118 Copyright © 2022 Hottec International, ott rights reserved

Criticality Safety Analysis of SFP for Callaway R**IR HOLT EC INTERNATIONAL of Nuclear Regulatory Research, April 2012.

[28] Bias Estimates Used in Lieu of Validation of Fission Products and Minor Actinides in MCNP KeffCatculations for PWR Burnup Credit Casks, ORNL/1M-2012/544, NUREG/CR-7205, USNRC Office of Nuclear Regulatory Research, September2015.

[29] Pool Layout for Spent Fuel Racks, Holtec International, Drawing 1997, Revision 1. [30]

Effects of Fuel Failure on Criticality Safety and Radiation Dose for Spent Fuel Casks, ORNL[FM-2002/255, NUREG/CR-6835, USNRC Office of Nuclear Material Safety and Safeguards, September 2003.

[31] Overview ofBORAL Performance Based Upon Surveillance Coupon Measurements, EPRI Report 1021052, PaloAlto, CA, December2010.

[32] Rack Construction - Region II, Holtec International, Drawing 1998, Revision 1.

[33] Rack Construction - Region 11, Holtec International, Drawing 1999, Revision 1.

[34] Ameren Spent Fuel Pool Levels for Dilution Event Analysis, NED2022001 3, Ameren Missouri, February 28, 2022.

[35] Ameren Supplemental Inputs for Dilution Event Analysis, NED20220033, Ameren Missouri, June 20, 2022.

[36] Fresh and Spent Fuel Pool Criticality Analyses, US NRC Regulatory Guide RG 1 .240, March 2021.

Criticality Safety Analysis of SFP for Callaway RI...

HOLTEC INTERNATIONAL APPENDIXA NEI 12-16 CRITICALITYANALYSIS CHECKLIST The criticality analysis checklist provides a summary of the evaluation that confirms that all the applicable subject areas are addressed in this report, and all the alternative approaches are identified and justified.

The checklist also assists the NRC reviewer in identifying areas of the analysis that conform or do not conform to the guidance in NEI 12-16 [3]. Subsequently, the NRC review can then be more efficiently focused on those areas that deviate from NEI 12-16 and the justification for those deviations.

1 .0 Introduction and Overview 1L: Notes/Explanation f!pe submittal Chapterl.O

çgesrequsted - - - YES/NO Chap.O jjysicalchanes YES/NO Chapters 1.0 and 8.0, Appendix B SummaryofTech Spec chges YES/NO Chapters 1.0 and 8.0,Appendb B Summary of analytical scope YES/NO Chpri.O,Section3.3 2.0 Acceptance Criteria and Regulatory Guidance Summary of requirements and guidance YES/NO Chapter 2.0 Reauirements documents referenced YES/NO Guidance documents referenced YES/NO Acceptance criteria described YES/NO 3.0 Reactor and Fuel Design Description Describe reactor operating parameters YES/NO Section 5.2, Paragraph 33.6.1 Describe all fuel in pool YES/NO Section 5.1, Subsection 3.3.1 Geometric dimensions (nominal and YES/NO Section 5.1, Subsection 3.3.2 tolerances)

Schematic of guide tube patterns YES/NO Section 5.1, Figure 3-1 Material compositions YES/NO Section 5.6 Describe future fuel to be covered YES/NO Section 3.8 Geometric dimensions (nominal and YES/NO tolerances)

Schematic of auide tube patterns YES/NO Material compositions YES/NO Describe all fuel inserts YES/NO Section 5.3, Paraqraph 33.6.3 Geometric dimensions (nominal and YES/NO tolerances)

Criticality Safety Analysis of SEP for Caflaway iii*

HOLTEC INTERNATIONAL Subiect IS w Included ---

NOftXIaI.

Material compositions YES/NO Describe non-standard fuel YES/NO Sections 5.7 and 58, Subsections 3.5.3 and 3.5.4 Geometric dimensions YES/NO Describe non-fuel items in fuel cells YES/NO Not applicable Nominal and tolerance dimensions YES/NO 4.0 Spent Fuel Pool/Storage Rack Description New fuel vault & storage rack description YES/NO Not applicable Nominal and tolerance dimensions Schematic (axial/cross-section)

Material compositions SDent fuel poo1. storaae rack descriDtion YES/NO Section 5A, Subsection 3.3.3 Nominal and tolerance dimensions YES/NO Section 5.4, Subsection 3.3.3 Schematic (axial/cross-section) YES/NO Figure 5-2, Figure 5-3 Material compositions YES/NO Section 5.6 Other reactivity control devices (inserts) YES/NO Not applicable Nominal and tolerance dimensions Schematic (axial/cross-section)

Material compositions 5.0 Overview of the Method of Analysis New fuel rack analysis description YES/NO Not applicable Storage geometries Boundina assembly desian(s) lnteqral absorber credit Accident analysis Spent fuel storaae rack analysis descrintion YES/NO Storage geometries YES/NO Chapter 1.0, Section 3.3 Bounding assembly design(s) YES/NO Subsection 3.3.1 Soluble boron credit YES/NO Chapter 1.0, Paragraph 3.3.7.3 Boron dilution analysis YES/NO Subsection 3.6.8 Burnup credit YES/NO Chapter 1.0, Subsection 3.3.6 Decay/cooling time credit YES/NO Chapter 1.0, Subsection 3.3.6, Paragraphs 3.3.6.2 and 3.3.7.2 Integral absorber credit YES/NO Section 3.3 Other credit YES/NO Emtv storaae cells, Chaoter 1.0 Fixed neutron absorbers YES/NO Chapter 1 .0, Section 3.3, Subsection 3.3.3 Aging management program YES/NO Subsection 3.7.1 Accident analysis YES/NO Section 3.6 Temperature increase YES/NO Subsection 3.6.1 HI-2220020 Rev. 1 PageA-2of7 Copyright C 2022 Holtec Internotionat, alt rights reserved

Criticality Safety Analysis of SFP for Callaway *111I HOLTEC INTERNATIONAL T

Subject :

Included .. Notes/çparItión Assembly drop YES/NO Subsections 3.6.2 and 3.6.3 Single assembly mistoad YES/NO Subsection 3.6.5 Muttiote mist oad YES/NO Subsection 3.6.6 Boron dilution YES/NO Subsection 3.6.8 Other YES/NO Fuel mislocation (Subsection 3.6.4),

Rack movement (Subsection 3.6.7)

Fuel out of rack analysis YES/NO Handling YES/NO Subsection 3.5.2 Movement YES/NO Subsection 3.5.1 Inspection YES/NO Subsection 3.5.2 6.0 Computer Codes, Cross Sections and Validation Overview Code/modules used for calculation of keff YES/NO Subsection 3.2.2 Cross section library YES/NO Subsection 3.2.2 Description of nuclides used YES/NO Section 5.6, Subsection 3.3.6 Converaence checks YES/NO Subsection 3.2.2 Code/module used for depletion calculation YES/NO Subsection 3.2.1 Cross section library YES/NO Subsection 3.2.1 Descriotion of nuclides used YES/NO Subsection 3.3.6 Converqence checks YES/NO Not aolicable Validation of code and library YES/NO Paragraph 3.2.2.1, SuboaraQraoh 3.3.6.6.1 Major actinides and structural materials YES/NO Paraqraph 3.2.2.1 Minor actinides and fission products YES/NO Subparagraph 3.3.6.6.3 Absorbers credited YES/NO ParaaraDh 3.2.2.1 7.0 Criticality Safety Analysis of the New YES/NO Not applicable Fuel Rack Rack model Boundary conditions Source distribution Geometry restrictions Limitinq fuel desian Fuel density Burnable poisons Fuel dimensions Axial blankets Limiting rack model Storae vault dimensions and materials Temperature Multiple regions/configurations Flooded HI-2220020 Rev. 1 PageA-3 of 7 Copyright © 2022 Hottec internationaL ott rights reserved

Criticality Safety Analysis of SEP for Callaway HOLTEC NTERNATONAL Low density moderator Ir!4 zz -

Eccentric fuel placement Tolerances Fuel qeometry Fuel pin pitch Fuel pellet OD Fuel clad CD Fuel content Enrichment Density lnteqral absorber Rack pitch Cell wall thickness Storage vault dimensions/materials Code uncertainty Biases Temperature Code bias Moderator conditions Fully flooded and optimum density moderator 8.0 Depletion Analysis for Spent Fuel Depletion model considerations YES/NO Subsections 3.2.1 and 3.3.6 Time step verification YES/NO Subsection 3.3.6 Convergence verification YES/NO Not applicable Simplifications YES/NO Subsection 3.3.6, Charter 4.0 Non-uniform enrichments YES/NO Section 3.3 Post depletion nuclide adjustment YES/NO Subsection 3.3.6 Cooling time YES/NO Chapter 1.0, Subsection 3.3.6, Paragraphs 3.3.6.2 and 3.3.7.2 Depletion parameters YES/NO Sections 5.2 and 5.3, Subsection 3.3.6 Burnable absorbers YES/NO Section 5.3, Subparaqraph 3.3.6.3.1 Integral absorbers YES/NO Section 5.3, Subparagraph 3.3.6.3.3 Soluble boron YES/NO Section 5.2, Paragraph 3.3.6.1 Fuel and moderator temperature YES/NO Section 5.2, Paragraph 3.3.6.1 Power YES/NO Section 5.2, Paragraph 3.3.6.1 Control rod insertion YES/NO Section 5.3, Subparagraph 3.3.6.3.2 Atypical cycle operating history YES/NO Subparagraph 3.3.6.3.2 9.0 Criticality Safety Analysis of Spent Fuel PoolStora9e Racks Hl-2220020 Rev. 1 PageA-4 of 7 Copyright © 2022 Hottec International, atirights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL Included Rack model YES/NO Section 3.3 Boundary conditions YES/NO Section 3.3 Sourcedistribution YES/NO Subsection 3.22 Geometry restrictions YES/NO Not applicable Design basisfueldescription YES/NO Section 3.3, Section 7.1, Chapter 4.0 Fuel density YES/NO Section 3.3, Subsection 3.3.2, Section 7.2 Burnable poisons YES/NO Section 3.3, Subparagraph 3.3.6.3.3, Subsection 7.6.3 Fuel assembly inserts YES/NO Section 3.3, Subparagraphs 3.3.6.3.1 and 3.3.6.3.2, Subsection 7.6.3 Fuel dimensions YES/NO Section 3.3, Subsection 3.3.2, Section 7.2 Axial blankets YES/NO Section 3.3, Chapter 4.0 Con9urations considered YES/NO Chapter 1.0, Subsection 7.7.2 Borated YES/NO Chapter 1.0, Paragraph 3.3.7.3, Subsection 7.7.3 Unborated YES/NO Chapter 1.0, Paragraph 3.3.7.2, Subsections 7.7.1 and 7.7.2 Multiplerack desjns YES/NO Section5A Afternate stora9e9eomety YES/NO Not appilcable Reactivitycontroldevices YES/NO Not applicable Fuel assembly inserts -

Storagecell inserts -

StorageceHblockindevices -

Axialburnupshapes YES/NO ph33.6.4 Uniform/distributed YES/NO Paragraph 3.3.6.4, Subsections 7.6.4, 7.7.2 and 7.7.3 Nod&ization -- - -- Paph 3.3.64 Blankets modeled YES/NO Section 3.3, Chapter 4.0 Tolerances/uncertainties YES/NO Section 3.3, Paragraph 3.3.7.1, Figure 3-3

FueIgeornet -

!/NQ_ Subsection Fre3-3 Fuel rod pin pitch YES/NO Subsection 3.3.2, Section 7.2 Fuel pellet OD YES/NO Subsection 3.3.2, Section 7.2 Cladding OD YES/NO Subsection33.2, Sedon72 Axial fuel position YES/NO Section 3.3, Subsection 3.3.3 Fuel content YES/NO Subsections 3.3.2 and 3.3.6, Sections 7.2 and 7.6 Enrichment YES/NO Subsection 3.3.2, Section 7.2 De YES/NO Subsection 3.3.2, Section 7.2 Assembly insert dimensions and YES/NO Subparagraph 3.3.6.3.4 materials Hl-2220020 Rev. 1 PageA-5 of 7 Copyright © 2022 Holtec InternationaL ott rights reserved

Criticality Safety Analysis of SFP for Calfaway IRIBI HOLTEC NTERNATIONAL

, - - Subjeci I Included Notes / Explanation Rack aeometrv YES/NO Subsection 3.3.3. Fioure 3-3. Section 7.3 Flux-trap size (width) YES/NO Not applicable Rack cell pitch YES/NO Subsection 3.3.3, Section 7.3 Rack wall thickness YES/NO Subsection 3.3.3. Section 7.3 Neutron absorber dimensions YES/NO Subsection 3.3.3, Section 7.3 Rack insert dimensions and materials YES/NO Not applicable Code validation uncertainty YES/NO Paragraph 3.2.2.1, Figure 3-3 Criticality case uncertainty YES/NO Figure 3-3 Depletion uncertainty YES/NO Subparagraph 3.3.6.6.1, Figure 3-3, Subsection 7.6.6 Burnup uncertainty YES/NO Subparagraph 3.3.6.6.2, Figure 3-3, Subsection 7.6.6 Biases YES/NO Section 3.3, FiQure 3-3 Design basis fuel design YES/NO Bounding fuel is used in the design basis model. Subsection 3.3.1, Section 7.1 Code bias YES/NO Paraaraoh 3.2.2.1. Fioure 3-3 Temperature YES/NO Bounding temperature is used in the design basis model. Section 3.3, Subsections 3.3.4 and 3.6.1, Section 7.4 Eccentric fuel placement YES/NO Bounding fuel placement is used in the design basis model. Subsection 3.3.5, Section 7.5 In-core thimble depletion effect YES/NO Bounding effect is used in the design basis model. Subparagraph 3.3.6.3.4, Subsection 7.6.3 NRC administrative margin YES/NO No additional administrative margin, over and above what is already prescribed by the regulations and quidance documents.

Modeling simplifications YES/NO Section 3.3, Chapter 4.0 Identified and described YES/NO Section 3.3. Chanter 4.0 1 0.0 Interface Analysis Interface confiqurations analyzed YES/NO Sections 3.4 and 7.8 Between dissimilar racks YES/NO Sections 3.4 and 7.8 Between storage configurations within a YES/NO Sections 3.4 and 7.8 rack Interface restrictions YES/NO Chapter 8.0 1 1 .0 Normal Conditions Fuel handling equipment YES/NO Bounded by normal storage conditions.

Criticality Safety Analysis of SFP for Callaway *1RS HOLTEC INTERNATiONAL Subject %

Included Notes / Explanation Administrative controls YES/NO Chapters 1.0, Subsections 3.7.1 and 7.10.3 Fuel inspection equipment or processes YES/NO Bounded by normal storage conditions.

Subsection 3.5.2 Fuel reconstitution YES/NO Subsections 3.5.2 and 3.5.4 1 2O Accident Analysis Boron dilution YES/NO Subsection 3.6.8 Normal conditions YES/NO Subsections 3.6.8 and 7.10.3 Accident conditions YES/NO Subsection 3.6.8 Single assembly misload YES/NO Subsections 3.6.5 and 7.10.1 Fuel assembly misplacement YES/NO Subsection 3.6.4 Neutron absorber insert misload YES/NO Not applicable Multiple fuel misloads YES/NO Subsections 3.6.6 and 7.10.2 Drooaed assembly YES/NO Subsections 3.6.2 and 3.6.3 Temperature YES/NO Subsection 3.6.1 Seismic event/other natural phenomena YES/NO Subsection 3.6.7 1 3.0 Analysis Results and Conclusions Summary of results YES/NO Chapter 8.0 Burnun curve(s) YES/NO Table 7-13. Fiaure 7-1 Intermediate decay time treatment YES/NO New administrative controls YES/NO Table 7-1 2, Chapter 8.0, Appendix 8, Subsections 3.5.4 and 3,5.5 Technical Specification markups YES/NO 14.0 References YES/NO Chapter 9.0 Aopendix A: Computer Code Validation:

Code validation methodology and biases YES/NO Paraqraph 3.2.2.1 New fuel YES/NO Paraaraoh 3.2.2.1, Table 3-2 Depleted fuel YES/NO Paragraph 3.2.2.1, Table 3-2 MOX YES/NO Paraqraph 3.2.2.1, Table 3-2 HTC YES/NO Paraoraoh 3.2.2.1. Table 3-2 Convergence YES/NO Trends YES/NO Paraoraoh 3.2.2.1. Table 3-3 Bias and uncertainty YES/NO Paragraph 3.2.2.1, Table 3-4 Range of applicability YES/NO Paragraph 3.2.2.1, Table 3-1 Analysis of area of applicability coverage YES/NO Paragraph 3.2.2.1. Table 3-1 HI-2220020 Rev. 1 PageA-7of7 Copyright © 2022 Holtec international, ott rights reserved

Criticality Safety Analysis of SFP for Callaway SIIR HOLT EC NTERNAT1ONA L APPENDIX B

SUMMARY

OF KEY PARAMETERS Table of Contents 8-

1.0 INTRODUCTION

8-2 8-2.0 STANDARD KEY PARAMETERS 8-2 8-3.0 KEY PARAMETERS FOR THE 8URNUP CREDIT 8-3 8-4.0 PROPOSED RULES FOR PERMISSIBLE LOADING 8-4 HI-2220020 Rev. 1 Page B-I of 4 Copyright © 2022 Hottec InternationaL ott rights reserved

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL B-1.O INTRODUCTION This appendix documents the key criticality analysis parameters for Callaway, which must be specifically tracked to ensure continual compliance with the criticality safety analysis. As discussed in Chapter 1.0, the criticality safety analysis, that takes credit for various combinations of the following, is provided in the main body of the report:

. Fixed neutron absorbers: BORALTM poison panels;

. Burnup of spent fuel assemblies;

. Spent fuel cooling time;

. Empty SFR storage cells;

. Soluble boron in the SFP.

Changes to the storage rack design, neutron absorber or soluble boron content should be evaluated under another process. Therefore, the focus of the parameters discussed in this appendix is related to the fuel design, SFP fuel arrangement and core operating parameters only. It is also assumed that the fuel design will not vary from the currently used version of the PWR 1 7x1 7 fuel assembly. The key parameters for the criticality safety analysis in the main body of the report are presented in the following sections.

B-2.O STANDARD KEY PARAMETERS For the burnup credit analyses, the parameters provided in Table B-i either have an impact on the analysis uncertainties or have an impact on the analysis directly (bias), and therefore should be treated as parameters that may have an impact to the analysis results.

Table B-I Summary of the Standard Key Parameters Parameter Limiting Value Impact Fuel dadchngOD, inches Bias and Uncertainty Fuel rod pitch, inches Bias and Uncertainty Fuel pellet OR inches . __________________ Bias and Uncertainty Fuel enrichment, wt% 235U Bias and Uncertainty Fuel density, g/cm3 Bias Distance from Bottom of Fuel Assembly to Beginning of Active Length, inches Bias 1

U02 theoretical density.

Criticality Safety Analysis of SFP for Callaway HOLTEC NTF RNATIONA L 83.O KEY PARAMETERS FOR THE BURNUP CREDIT In additional to the parameters presented in Section B-2.O, for the analyses of the loading regions that involve spent fuel with burnup credit, the parameters provided in Table B-2 either have an impact on the analysis uncertainties or have an impact on the analysis directly (bias),

and therefore should be treated as parameters that may have an impact to the analysis results.

Table B-2 Summary of Key Parameters for the Burnup Credit Parameter J Limiting Value Impact Core Operating Parameters Maxirnurnfueltemperature,K Bias

]______________

Maximum core moderator temperature, K Bias Soluble boron concentration (cycle average), ppm Bias Fuel Inserts and IBA Irradiation duration with fuel inserts, GWd/mtU Bias WABA1 absorber content, wt% B4C Bias WABA absorber ID, inches WABA absorber CD, inches Bias Number of the IFBA rods IFBA ZrB2 coating loading, mg10B/inch Bias Burnup-weighted cycle-average RCCA insertion depth during full power operation2, inches Depletion Related Fuel Geometry Changes Fuel rod growth, inches Bias and Uncertainty Fuelgridgrowth, inches Bias and Uncertainty Other Parameters Axial burnup profile Burnup uncertainty, %

Cooling time for Region 2, years Different loading curves 1

WABA and IF8A have been considered in alt depletion analyses for the design basis calculations.

2 The full power operation here means any reactor operation other than the short-term transients (e.g., reactor startup, shutdown, etc.) that may provide a reasonable contribution to the fuel exposure.

Criticality Safety Analysis of SFP for Callaway IIIRI HOLTEC NIERNAHONAL B-4.O PROPOSED RULES FOR PERMISSIBLE LOADING The proposed rules for permissible loading of the spent fuel racks are as follows:

1 . The permissible content for any rack cell depends on the content of the rack cells that are face adjacent to that cell.

2. Rack cells that face each other across a rack-to-rack gap are considered face-adjacent.

3. Acell can either

a. Contain a Region 1 assembly; or Ii Contain a Region 2 assembly; or

c. Be empty.

4. The placement rules are as follows. All requirements applicable to a cell must be met.

4.1 For cells containing a Region I assembly 4.1 .1 None of the face-adjacent cells may contain a Region I assembly; 4.1.2 A minimum oftwo (2) ofthe lace-adjacent cells must be empty; 4.1.3 The remaining face-adjacent cells may contain a maximum of two (2)

Region 2 assemblies. See also rule 4.2.3; 4.1.4 If both remaining face-adjacent cells contain Region 2 assemblies, then rule 4.2.1 is restricted to one (1) Region 1 assembly for those cells.

4.2. For cells containing a Region 2 assembly 4.2.1 A maximum of two (2) of the face-adjacent cells may contain a Region 1 assembly. See also rule 4.1.4; 4.2.2 The remaining face-adjacent cells may be empty or contain a Region 2 assembly; 4.2.3 If two (2) face-adjacent cells contain Region 1 assemblies, then rule 4.1.3 is restricted to one (1) Region 2 assembly for those cells.

Criticality Safety Analysis of SFP for Callaway HOLT INTERNATIONAL EC APPENDIX C RG I .240 COMPLIANCE The table below provides a summary that confirms compliance with clarifications and exceptions to the guidance in NEI 12-16 [31, which are explicitly mentioned in the Regulatory Guide RG 1 .240 [36]. The table assists the NRC reviewer in verifying compliance with RG 1.240.

y....:.

Subject C ..x I Notes I Explanation a Section 1.4 states that the double contingency principle, as All accident events have been applied to criticality accidents, means, in part, that licensees explicitly evaluated in Sections 3.6 do not need to consider the simultaneous occurrence of and 7.10. None of these events is two independent and unlikely conditions... However, if no considered applicable to the controls or documents exist to preclude such a condition, normal condition.

then the licensee or applicant should treat it as part of the normal condition.

b ... Licensees or applicants should establish how they will All the major assumptions and maintain any excess safety margins being used tojustify simplifications in the design basis assumptions or simplifications when they update the calculations provided in Section 3.3 criticality analyses, using their approved methodology, to and Chapter 4.0 are conservative.

accommodate changes in the fuel storage characteristics. No extra margin is used to justify assumptions or simplilications in the design basis model.

c Section 2 discusses acceptance criteria for fresh fuel vault Not applicable storage...

d Section 3.1.3 discusses the treatment of nuclides credited in No lumped fission products are the depletion and criticality analysis; however, it doesnt used.

provide any guidance on the treatment of lumped fission products...

e Section 4.2.3 states that the depletion bias and uncertainty The guidance in Section 4.2.3 of described in this section account for all uncertainties NEI 12-16 is followed.

associated with depletion. If licensees are following the guidance in Section 4.2.3 about treatment of the depletion parameters, the staff would find this approach acceptable.

f ... Each unique axial plane in the bundle designs should be All the axial variations of the fuel evaluated. For example, some bundle designs may use lattice parameters have been different fuel rod pitches at different axial planes. Licensees reviewed and they are either or applicants should justify their selection of lattice considered conservatively (e.g., 1BA parameters for evaluation. with the cutback regions are neglected) or neglected (e.g.,

blankets).

Criticality Safety Analysis of SFP for Callaway HOLTEC INTERNATIONAL 1teni CIx K Subject p Notes I Explanation 9 Section 5.1.6 discusses a conservative approach to Not applicable modeling integral burnable absorbers using nominal dimensions combined with a minimum absorber loading...

h Section 5.2.2 states that credit can be taken for radial Not applicable leakage near the walls of the spent fuel pool for allowing lower burnup fuel requirements on the periphery of the spent fuel pool.

Section 5.2.2.4 provides recommendations on the All eccentric positioning treatment of eccentric positioning for fuel assemblies configurations have been explicitly within spent fuel pool cells Licensees or applicants

... analyzed.

should consider any unique aspects of the configuration being analyzed that may lead to a more limiting eccentric positioning.

j ...

The NRC agrees that the limiting abnormal condition will Both a single assembly misload be the one which requires the highest soluble boron to and multiple misload event have meet regulatory requirements. However, while misloading been analyzed, and a soluble events are typically the limiting abnormal condition, that is boron requirement for the limiting not always the case. Therefore, licensees or applicants accident condition has been should consider all credible abnormal and accident determined.

conditions.

k Section 9.4 lists some parameters that may need to be A cycle burnup averaged soluble verified as part of post irradiation fuel characterization boron concentration has been activities. One of the parameters is soluble boron (burnup used in the depletion calculations averaged). The NRC endorses use of cycle burnup and presumed to be used as a part averaged soluble boron, consistent with Section 4.2.1, but of post irradiation fuel the NRC does not endorse other interpretations of the characterization activities.

phrase burnup averaged, such as averaging across the whole burnup range for a given fuel assembly.

. An important aspect of validation that is not covered in Various subsets of the critical much detail is the importance of selecting appropriately experiments have been evaluated representative benchmarks and critical experiments, in the benchmark analysis, and the especially when performing trend evaluation. Licensees or applicable subsets were used for applicants may need to consider smaller sets of data to different loading regions and avoid confounding effects that obscure trends or that lead conditions.

to conclusions based on data that are not highly representative of the spent fuel pool geometry and compositions of interest.

Hl-2220020 Rev. 1 Page C-2 of 3 Copyright C 2022 Hottec InternationaL dllrights re5erved

Criticality Safety Analysis of SFP for Callaway 11111 HOLTEC INTERNATIONAL Suhct I rIon m Section A.2.2 states that startup critical datafrorn boiling- Not applicable water reactors (BWRs) can be used to benchmark depletion codes and compute a bias and bias uncertainty...

n Section A.4 discusses use of a secondary code as an Not applicable intermediate means to validate the primary code used for the nuclear criticality safety analyses...

0 NEI 12-16, Revision 4, provides many recommendations The fuel assembly designs with the that are based on analyses performed using typical typical geometries and geometries and compositions associated with spent fuel compositions are operated and pols and bundle designs that are currently in widespread stored in the Callaway SFP.

use in the United States (e.g., cylindrical uranium dioxide fuel pellets enclosed in zirconium alloy tubes). Novel configurations and concepts, such as accident-tolerant fuel designs, may requirejustification for continued use of the assumptions. For example, dispositions of specific uncertainties as not significant may no longer be valid, simplifying assumptions may become nonconservative, and additional uncertainties may need to be considered.

Licensees orapplicants are responsible forjustifying use of the guidance in NEI 12-16, Revision 4, in any such applications.

p NEI 12-16, Revision 4, includes some general conclusions All such applicable general based on sensitivity studies performed to support the conclusions are confirmed to guidance Licensees or applicants should ensure that a remain applicable to the design conclusion is applicable to their circumstances before basis model used in the criticality implementing the guidance associated with that calculations.

conclusion.

q Appendix B to NEI 12-16, Revision 4, includes an example The applicable depletion related to supplement the guidance... Licensees or applicants fuel assembly geometry changes should ensure that the example in Appendix B is applicable have been explicitly evaluated in to their circumstances before implementing the guidance Paragraph 3.3.6.5 and as described in the example. Subsection 7.6.5.

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8.0 CONCLUSION

9.0 REFERENCES

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8.0 CONCLUSION

SUMMARY

1.0 INTRODUCTION

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