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HI-2220020, Revision 2, Non Proprietary Version of Criticality Safety Analysis of SFP for Callaway Nuclear Generating Station
	ML22299A235
Person / Time
Site:	Callaway
Issue date:	10/21/2022
From:	Anton S; Holtec
To:	; Office of Nuclear Reactor Regulation
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ML22299A232	List: ML22299A233; ML22299A235; ULNRC-06774, Affidavits for Withholding;
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	ULNRC-06774 Hl-2220020, Rev 2
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Enclosure 2 to ULNRC-06774 Page 1 of 141 ENCLOSURE2 CRITICALITY SAFETY EVALUATION REPORT (NON-PROPRIETARY VERSION)

The following pages provide the non-proprietary version of the criticality safety analysis report provided by HOLTEC International supporting the license amendment request submitted in Ameren Missouri letter ULNRC-06723 dated August 29, 2022 (ADAMS Accession No. ML2224A122).

HI-2220020, "Non-Proprietary Version of Criticality Safety Analysis of SFP for Callaway Nuclear Generating Station," Revision 2 dated October 21, 2022

[NON-PROPRIETARY]

140 pages follow this cover sheet

HOLTEC INTERNATIONAL Nuclear Power Division Sponsoring Company Hl-2220020 Company Record Number Report 3225 Project No.

2 21 Oct 2022 Revision No.

Issue Date Copyright Record Type Proprietary Classification Nuclear No Quality Class Export Control Applicability Record

Title:

Non Proprietary Version of Criticality Safety Analysis of SFP for Callaway Nuclear Generating Station Prepared by:

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S.Anton, 20 Oct 2022 V.Makodym, 21 Oct 2022 D.Mitra-Majumdar, 21 Oct 2022 Signature histories are provided here for reference only. Company electronic signature records are traceable via the provided Verification QR Code and are available for review within the secure records management system. A valid Verification QR Code and the presence of this covering page indicates this record has been approved and accepted.

Proprietary Classification This record does not contain confidential or Proprietary Information. The Company reserves all copyrights.

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Criticality Safety Analysis of SFP for Callaway Proprietary Information Revision Log HOL TEC INT E RNATIO N A L Revision Description of Changes 0

Initial issue.

1 The client comments are incorporated, and changes are marked by a revision bar.

2 Revision bars from previous revision were removed. Proprietary markings were added, no technical changes.

Proprietary Information Proprietary Information is annotated in this document by placing the information in bold square brackets [ ]. The annotation of the proprietary information corresponds to the specific reasons(s) for claiming the information as proprietary as delineated in the respective Affidavit executed by the owners of the information. The annotations used are provided as follows:

1) Holtec proprietary information - denoted with "4a,4b" superscript, which provides the reference the corresponding subsection of the Holtec Affidavit providing the reason(s)

2) Westinghouse proprietary information - denoted with "W" superscript.

Corresponding reason(s) are delineated in the Westinghouse Affidavit

3) Framatome proprietary information - denoted with "F" superscript.

Criticality Safety Analysis of SFP for Callaway Proprietary Information EXECUTIVE

SUMMARY

HOL TEC IN TE RN ATION A L This report documents the criticality safety analyses of the spent fuel pool performed for the Callaway Unit 1, which contains a single type of BORAL' 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 of the spent fuel racks.

The analysis of fuel irradiation during core operation is performed with CASMOS Version 2.08.00, a multigroup two-dimensional transport theory code based on the Method of Characteristics, using the ENDF/8-VII Library. The criticality calculations are performed with MCNPS Version 1.51, a three-dimensional continuous energy Monte Carlo code, using continuous energy cross-section data predominantly based on ENDF/B-VII.

To account for different temperatures, [

)4a, 4b 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 (kett) 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, all 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 Proprietary Information Table of Contents HOLTEC IN TERNA T IONAL EXECUTIVE

SUMMARY

........................................................................................................................................... 11 1.0 PURPOSE................................................................................................................................................... 1 2.0 ACCEPTANCE CRITERIA.............................................................................................................................. 2 3.0 METHODOLOGY........................................................................................................................................ 3 3.1 GENERAL APPROACH......................................................................................................................................... 3 3.2 COMPUTER CODES AND CROSS-SECTION LIBRARIES................................................................................................. 3 3.2.1 CASM05 Overview................................................................................................................................... 3 3.2.2 MCNP5 Overview..................................................................................................................................... 4 3.3 ANALYSISMETHODS.......................................................................................................................................... 5 3.3.1 Design Basis Fuel Assembly Design.......................................................................................................... 7 3.3.2 Fuel Assembly Parameters....................................................................................................................... 7 3.3.3 Spent Fuel Rack Parameters.................................................................................................................... 8 3.3.4 Spent Fuel Pool Water Temperature...................................................................................................... 10 3.3.5 Fuel Assembly Radial Positioning and Orientation................................................................................ 11 3.3.6 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 lnterface............................................................................................................... 23 3.4.4 Region 1 to Region 1 lnterface............................................................................................................... 25 3.4.5 Region 2 to Region 2 lnterface............................................................................................................... 25 3.4.6 Combined Qualifications........................................................................................................................ 25 3.5 NORMAL CONDITIONS...................................................................................................................................... 25 3.5.1 Fuel Movement Operations................................................................................................................... 25 3.5.2 Fuel Insertion and Removal Operations................................................................................................. 26 3.5.3 Storage of Fuel Rod Storage Rack.......................................................................................................... 26 3.5.4 Storage of Fuel Assemblies with Missing Rods...................................................................................... 27 3.5.5 Storage of Low-Burned Fuel Assemblies................................................................................................ 27 3.6 ABNORMAL AND ACCIDENT CONDITIONS............................................................................................................. 28

3. 6.1 Loss of SFP Cooling................................................................................................................................. 28 3.6.2 Dropped Assembly-Horizontal............................................................................................................. 29 3.6.3 Dropped Assembly-Vertical into a Storage Cell................................................................................... 29 3.6.4 Mislocated Fuel Assembly...................................................................................................................... 29 3.6.5 Misloaded Fuel Assembly....................................................................................................................... 29 3.6.6 Incorrect Loading Curve......................................................................................................................... 30 3.6.7 Rack Movement..................................................................................................................................... 30 3.6.8 Boron Dilution........................................................................................................................................ 30 3.7 MARGIN EVALUATION...................................................................................................................................... 31

3. 7.1 Neutron Absorber Aging Effects............................................................................................................. 31

3. 7.2 BORAL rM Panel 108 Areal Density............................................................................................................ 32

3. 7.3 Criticality Analysis Safety Margin.......................................................................................................... 32 3.8 PERMITTED FUTURE FUEL ASSEMBLIES................................................................................................................ 33 4.0 ASSUMPTIONS........................................................................................................................................ 48 5.0 INPUT DATA............................................................................................................................................ 50 Hl-2220020 Rev. 2 Page Ill of VII Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT E RNAl IO NAL 5.1 FUEL ASSEMBLY 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 SFP OPERATING PARAMETERS........................................................................................................................... 51 5.6 MATERIAL COMPOSITIONS................................................................................................................................ 51

5. 7 FUEL ROD STORAGE 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 FUEL ASSEMBLY DESIGN............................................................................................................... 68 7.2 REACTIVITY EFFECT OF FUEL ASSEMBLY PARAMETERS............................................................................................. 68 7.3 REACTIVITY EFFECT OF SFR PARAMETERS............................................................................................................ 68 7.3.1 Reactivity Effect of the 8£ 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 7.6.1 Reactivity Effect of Core Operating Parameters.................................................................................... 69 7.6.2 Reactivity Effect of Cooling Time........................................................................................................... 70 7.6.3 Reactivity Effect of /BA and Fuel Inserts................................................................................................. 70 7.6.4 Reactivity Effect of Axial Burn up Profiles............................................................................................... 71 7.6.5 Reactivity Effect of Depletion Related Fuel Assembly 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 keff Calculation with Borated Water...................................................................................... 72 7.8 SFR INTERFACES............................................................................................................................................. 72 7.9 NORMAL CONDITIONS...................................................................................................................................... 73

7. 9.1 Storage of Fuel Rod Storage Rack.......................................................................................................... 73 7.9.2 Storage of Fuel Assemblies with Missing Rods...................................................................................... 73 7.10 ACCIDENT CONDITIONS.................................................................................................................................... 74 7.10.1 Misloaded Fuel Assembly....................................................................................................................... 74 7.10.2 Incorrect Loading Curve......................................................................................................................... 74 7.10.3 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-1 APPENDIX B

SUMMARY

OF KEY PARAMETERS................................................................................................ 8-l APPENDIX C RG 1.240 COMPLIANCE.............................................................................................................. C-1 Hl-2220020 Rev. 2 Page IV of VII Copyright © 2022 Ho/tee International, all rights reserved

List of Tables Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TE RNATIONA L Table 3 Summary of Area of Applicability of the MCNP5 Benchmark............................................. 34 Table 3 MCNP5 Benchmark Analysis for Various Fuel and Water Subsets of Experiments..... 35 Table 3 Significant Trending Analysis for Callaway Parameters......................................................... 36 Table 3 Summary of MCNP5 Code Validation Bias and Bias Uncertainty...................................... 37 Table 3 List of Spent Fuel Isotopes................................................................................................................ 38 Table 3 Bounding Axial Burnup Profiles for Westinghouse 17x17 Fuel Type [15]...................... 39 Table 3 Bounding Axial Burnup Profiles from NUREG/CR-6801 [26]............................................... 40 Table 5 Specification of the Fuel Assembly Parameters [20]............................................................... 52 Table 5 PWR 17x17 Fuel Assembly Manufacturing Tolerances.......................................................... 53 Table 5 PWR 17x17 Fuel Assembly Depletion Related Geometry Changes.................................. 53 Table 5 Core Operating Parameters.............................................................................................................. 54 Table 5 Specification of the Fuel Inserts [20]............................................................................................. 55 Table 5 Specification of the Integral Burnable Absorbers.................................................................... 56 Table 5 Specification of the Callaway SFR Parameters.......................................................................... 57 Table 5 SFP Operating Parameters [19], [29], [34], [35]......................................................................... 58 Table 5 Material Compositions of the Major Design Components.................................................. 59 Table 5-1 O - Fuel Rod Storage Rack Parameters............................................................................................. 62 Table 7 Bounding Fuel Assembly Design.................................................................................................... 77 Table 7 Reactivity Effect of Fuel Assembly Parameters.......................................................................... 78 Table 7 Reactivity Effect of SFR Parameters............................................................................................... 79 Table 7 Reactivity Effect of SFP Water Temperature.............................................................................. 81 Table 7 Reactivity Effect of Fuel Assembly Radial Positioning............................................................ 82 Table 7 Reactivity Effect of Core Operating Parameters....................................................................... 83 Table 7 Reactivity Effect of Cooling Time................................................................................................... 84 Table 7 Reactivity Effect of Irradiation with the IBA and Fuel Inserts............................................... 85 Table 7 Reactivity Effect of Axial Burnup Profile....................................................................................... 86 Table 7 Reactivity Effect of Depletion Related Fuel Assembly Geometry Changes.................. 87 Table 7 Determination of Depletion Uncertainty, Burnup Uncertainty and MAFP Bias.......... 88 Table 7 Summary of the Analysis for Region 2 (Spent Fuel)............................................................. 90 Table 7 Summary of the Loading Curves for Callaway SFP............................................................... 95 Table 7 Loading Curves Confirmatory Calculations.............................................................................. 96 Table 7 Summary of the Analysis for Region 1 (Fresh Fuel).............................................................. 97 Table 7 Summary of the Analysis for Normal Conditions with Soluble Boron Credit............. 98 Table 7 Summary of the Analysis for the SFR Interfaces.................................................................... 99 Table 7 Summary of the Analysis for the FRSR.................................................................................... 100 Table 7 Summary of the Analysis for Fuel Assemblies with Missing Rods................................ 101 Table 7 Deleted................................................................................................................................................. 102 Table 7 Maximum kett Calculation for the Fuel Mislead Accident................................................. 103 Table 7 Maximum kett Calculation for the Incorrect Loading Curve Accident.......................... 106 Table 7 SFP Boron Dilution Accident Analysis...................................................................................... 107 Hl-2220020 Rev. 2 Page V of VII Copyright © 2022 Ho/tee tnternotionol, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TE RNATIO NAL Table 7 Reactivity Effect of the BORAL' Panel 10B Areal Density................................................. 108 Table 7 Margin Evaluation............................................................................................................................ 109 Table 7 Reactivity Effect of the 84C Particle Size.................................................................................. 110 Table B Summary of the Standard Key Parameters.............................................................................. B-2 Table B Summary of Key Parameters for the Burnup Credit.............................................................. B-3 List of Figures Figure 1 Callaway SFR Permissible Loading Configurations................................................................... 1 Figure 3 Radial Cross-Section View of the MCN PS Design Basis Model of the SFR.................. 41 Figure 3 Design Basis Calculation of a kett Value...................................................................................... 42 Figure 3 Determination of the Total Correction Factor......................................................................... 43 Figure 3 Radial Cross-Section View of the MCNPS Model for the SFR Interfaces...................... 44 Figure 3 Potential Interfaces between the Loading Regions............................................................... 45 Figure 3 Radial Cross-Section View of the MCNP5 Model for the FRSR......................................... 46 Figure 3 MCNPS Model of the Heterogeneous BORAL' Panel.........................................................47 Figure 5 Considered PWR 17x17 Fuel Assembly Layouts..................................................................... 63 Figure 5 Planar Cross-Section of the Callaway SFR................................................................................. 64 Figure 5-3 -Axial Cross-Section of the Callaway SFR.................................................................................... 65 Figure 5 Fuel Assembly Layouts with Missing Rods................................................................................ 66 Figure 7 Loading Curves for Uniform Loading of Spent Fuel Assemblies (Region 2).............. 111 Figure 7 Total Reaction Rate Distribution for Region 1 to Region 2 Interface........................... 112 Figure 7-3 -Total Reaction Rate Distribution for Region 1 (2x2) to Region 2 lnterface................ 112 Figure 7 BORAL' Panel 10B Areal Density as a Function of ~k......................................................... 113 Hl-2220020 Rev. 2 Page VI of VII Copyright © 2022 Holtec lnternotional, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information List of Abbreviations ACPL Holtec approved computer program list BPR burnable poison rod ccw component cooling water system CFR U.S. Code of Federal Regulations FRSR fuel rod storage rack IBA integral burnable absorber IFBA integral fuel burnable absorber ID 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. 2 Copyright © 2022 Ho/tee lnternotional, all rights reserved HOL TEC INT E RNA T IONAL Page VII of VII

Criticality Safety Analysis of SFP for Callaway Proprietary Information 1.0 PURPOSE HOL TEC INT E RNAII ONAL 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 BORAL' spent fuel rack designed for storage of the PWR 17x17 fuel assemblies. The criticality safety analysis of record for the 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 [2] 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 of the 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 2x2 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.

Fresh Spent Spent Fresh Spent Spent Region 1 Region 2 Figure 1 Callaway SFR Permissible Loading Configurations Hl-2220020 Rev. 2 Page 1 of 118 Copyright © 2022 Holtec International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information Additionally, the criticality evaluations are performed for the following:

Normal conditions:

o credible interface conditions in the spent fuel pool; o

fuel movement, insertion, and removal operations; o

storage of fuel rod storage racks; HOL TEC INT E RN Al IONAL o

specific Callaway fuel inventory, such as the fuel assemblies with the missing rods; o

fuel assembly reconstitution activities; Abnormal and accident conditions.

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.

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

2.0 ACCEPTANCE CRITERIA Codes, standard, and regulations or pertinent sections thereof that 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 Proprietary Information Power Plants, NEI 12-16, Revision 4, Nuclear Energy Institute.

HOLTEC INT E RNA f lONA L The objective of this analysis is to ensure that the effective neutron multiplication factor (kett) of the SFP 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 unboratcd water and docs not exceed 0.95 for the pool flooded with borated water, all for 95% probability at a 95% confidence level, in accordance with 10 CFR 50.68(b)(4).

3.0 METHODOLOGY 3.1 General Approach The analysis is performed in a manner such that the results arc below the regulatory limit with a 95% probability at a 95% confidence level. The calculations arc 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 arc used to determine the final kett used to show compliance with the regulatory limits for both normal and accident conditions.

The accident calculations arc 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 arc 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 (depiction) 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]. CASMO5 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 arc provided in the input model, and the atom densities for actinides and fission products in the isotopic composition of spent fuel are determined by CASMO5.

For all CASMO5 depletion calculations, the ENDF/B-Vi'I Library [7] is used.

Although CASMO5 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 Proprietary Information HOL TEC INT E RNA I IO NAL 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 MCNPS Overview MCNPS 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. MCNPS calculations use continuous energy cross-section data predominantly based on ENDF/B-VII [9]. To account for different temperatures,

[

)4a, 4b The convergence of a Monte Carlo criticality problem is sensitive to the following parameters:

(1) number of histories per cycle, (2) the number of cycles skipped before averaging, (3) the total number of cycles and (4) the initial source distribution. All MCNPS calculations are performed with a minimum of 12,000 histories per cycle, a minimum of 400 skipped cycles before averaging, and a minimum of 400 cycles that are accumulated. The initial source is specified as the fueled regions (assemblies) and confirmed to converge. It is a well-known fact [11] that kett (eigenvalue), which is an integral quantity, converges much faster than the fission source spatial distribution (eigenfunction).

However, a convergence of the spatial source distribution is important for estimating local quantities, such as pin power. To assist users in assessing the convergence of the fission source spatial distribution, MCNPS computes a quantity called the Shannon entropy of the fission source distribution, Hsrc [8]. The Shannon entropy [11] is a well-known concept from information theory that has been shown to be an effective diagnostic measure for characterizing convergence and provides a single number for each cycle to help characterize convergence of the fission source distribution. It has been found that the Shannon entropy converges to a single steady-state value as the source distribution approaches stationarity. Therefore, the convergence of the power iteration process is ensured using the Shannon entropy, as implemented in MCNPS [8]. Since the eigenvalue (kett) converges faster than the fission source distribution, the convergence of the kett is assured by the convergence of the source distribution, The Shannon entropy convergence has been checked for each calculation.

3.2.2. 1 MCNPS Validation The benchmarking of MCNPS-1.51 is based on the guidance in [2] and [12], and includes calculations for a total of 562 critical experiments with fresh UO2 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 MCNPS-1.51 and continuous energy ENDF/B-VII data library to perform criticality safety Hl-2220020 Rev. 2 Page 4 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TER NAl IO NA L calculations is documented in [13].

The validation confirms the accuracy of the calculational methodology to predict subcriticality. Validation includes identification of the difference between calculated and experimental neutron effective multiplication factor (kett), called the bias. The range of the benchmark parameters used to validate the calculational methodology primarily defines the area of applicability (AOA), 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 [13] are evaluated in Table 3-3 for the specific parameters used in the current analysis.

Based on the results presented in Table 3-2 and Table 3-3, the maximum MCNP5 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 kett-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 Fuel Designs and Fuel Assembly Parameters:

The bounding PWR 17x17 fuel assembly designs are used in the design basis analyses.

See Subsection 3.3.1; Fresh and/or spent fuel with a uniform enrichment are considered, i.e., the same bounding enrichment is assumed along the entire active length for each fuel pin. Lower enriched blankets are neglected. See Section 4.0; The maximum fuel enrichment of 5.0 wt% 235U is used for fresh fuel assemblies; No credit is considered for fuel-related integral burnable absorbers, such as Gd2O3 (Gadolinia-bearing rods) or ZrB2 (IFBA rods);

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT E RNAl IONAL For spent fuel, the isotopic composition is determined using the bounding axial burnup profile, core operating parameters and bounding condition of the 18As and reactivity control devices. See Subsection 3.3.6.

Bounding Storage Rack Parameters:

2x2 array of SFR storage cells in view of fabricated cells with the attached 80RAL' absorber panels and developed cells is used in the design basis analyses.

Periodic boundary conditions are considered at the periphery, thus creating a laterally infinite array of storage cells; The minimum 108 loading of the 80RAL' absorber material is used, i.e., the reactivity effect is conservatively treated as a bias rather than an uncertainty. See Subsection 3.3.3.

Bounding SFP Moderator Temperature:

The bounding SFP moderator temperature and density are used for all design basis calculations. The calculations include NJOY corrected cross-sections and S(a,~) cards.

See Subsection 3.3.4.

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

The fuel assembly is explicitly modeled in terms of fuel stack, cladding, instrument tube and guide tubes. The fuel assembly design parameters are nominal values; The storage rack cells are explicitly modeled in terms of steel box, poison panel and sheathing.

The SFR design parameters are nominal values, except for the 80RAL' absorber panel length and 108 loading; All materials are assumed at the same temperature as the SFP moderator; The bounding fuel assembly positioning in the SFR storage cell is considered.

See Subsection 3.3.5.

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 -J ((Tf + (TD is called the 95/95 uncertainty.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TE RNAl IO NAL The established maximum Llkcalc is then either statistically combined with the other uncertainties to determine the maximum kett value or the bounding parameter's value is incorporated into the design basis model.

Such bounding approach provides analysis simplicity and additional safety margin. The MCNP5 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 GAIA 17x17 (GAi).

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 applied to all fresh and spent fuel assemblies in the SFR model (if applicable).

According to [3], the manufacturing tolerances on the fuel cladding thickness and guide/instrument tube thickness have been shown in a generic study to be insignificant and do not require analysis. 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 OD; Case 3.3.2.2:

Maximum cladding OD; 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 OD; Case 3.3.2.6:

Maximum fuel pellet OD; Case 3.3.2.7:

Criticality Safety Analysis of SFP for Callaway Proprietary Information Case 3.3.2.8:

Maximum fuel density; Case 3.3.2.9:

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

HOL TEC INT E RN A f'IO NAL Separate depletion calculations are performed for Cases 3.3.2.1 through 3.3.2.9 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 (BORAL') 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 fuel region vary, thus slightly exposing active fuel above the top end of the absorber panel.

[

)WAaAb Since the bounding 10B loading of the BORAL' absorber material is used in the calculations, the 10B loading tolerance is not analyzed.

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 of the SFR parameters are considered:

Case 3.3.3.0:

Reference case.

All rack parameters are nominal except the BORAL' 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:

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TE RNArlO NA L Case 3.3.3.9:

Minimum poison thickness. Note that the poison material composition is adjusted to maintain the poison 10B areal density and estimate a net effect of the panel thickness; 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. 7 BORAL TM Panel 84C Particle Size BORAL' 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 BORAL' material that was eventually used for fabrication of the SFRs for Callaway. Based on the results of sieve analyses, a typical distribution of the 84C particle size in BORAL' is the following:

0-45 µm:

45 - 180 µm:

180 - 300 µm:

1.5% - 4.9%

81.2% - 93.5%

4. 7% - 13.9%

over 300 µm:

0%

In order to investigate the reactivity effect of the 84C particle size, calculations for the heterogeneous poison panels (84C particles in aluminum matrix) are performed. Inside the heterogeneous model of the poison panel, [

J4a, 4b 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 BORAL' with 84C particle size of 45 µm; Case 3.3.3.1.2:

Heterogeneous BORAL' with 84C particle size of 180 µm.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT E RNATI ONAL While there is a small fraction of the 84( particles with more than 180 µm in size, the mean particle size of 84( powder used in manufacturing process for 8ORAL' is significantly less than 180 µm, hence 180 µm used as an upper bound value for all particles in the 8ORAL ' material is a reasonable and conservative assumption. The results are compared to estimate a difference between the homogeneous and heterogeneous model with the variable 84C particle size.

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

[3], 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 8ORAL' poison, the minimum SFP water temperature and maximum density are expected to produce the maximum reactivity condition.

[

]4a, 4b Studies are performed to demonstrate the reactivity effect of the moderator temperature and density over the temperature range specified in Table 5-8 [

] 4a, 4b, 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:

Reference case. Temperature of 4 °C [

Case 3.3.4.1:

Minimum nominal temperature of 20 °C [

]4a, 4b; Case 3.3.4.2:

Maximum possible temperature of 120 °C [

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT E RNAT IONAL Case 3.3.4.3:

Maximum possible temperature of 120 °C with 10% void, i.e., a reduction in the water density by 10% (boiling conditions, [

)4a, 4b.

The bounding moderator temperature and density [

J4a, 4b are considered in all design basis calculations.

3.3.5 Fuel Assembly Radial Positioning and Orientation 3.3.5. 7 Fuel Assembly Radial Positioning A fuel assembly 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 Proprietary Information HOLTEC INT E RN A rlO NA L 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 Fuel Assembly 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 then specified as input data into MCNP5. Table 3-5 provides a list of spent fuel isotopes credited in MCNP5. All volatile and gaseous nuclides have been removed from the isotopic composition.

Also, the short-lived isotopes with a half-time less than a day, with a few exceptions like 243Pu (T112 = 4.956 hours0.0111 days 0.266 hours 0.00158 weeks 3.63758e-4 months ),

240U (T112 = 14.1 hours1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months ) and 242Am (T112 = 16.02 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months ) have not been considered. Therefore, the spent fuel isotopes in Table 3-5 at the reactor shutdown are representative and conservative for 0 hours0 days 0 hours 0 weeks 0 months cooling time. The isotopic content of 239Np is added to the isotopic content of 239Pu, essentially assuming an instant decay of 239Np to 239Pu, though this decay has a half-life of about 2.4 days. This is conservative since it increases the amount of the fissile isotope 239Pu.

Isotopic compositions are calculated in CASMOS for a range of enrichments with a burnup step up to 2.5 GWd/mtU, and for cooling times from O hours to 20 years. Note that for intermediate burnups, the isotopic composition is determined by linear-linear interpolation. Previous studies have shown that the burnup increment of 2.5 GWd/mtU is sufficiently small to permit this linear interpolation approach [15].

Assembly average isotopic compositions are extracted from the CASMOS output files and used in the MCNP models, i.e., applied equally to all fuel rods or fuel rod segments with the corresponding burnup. [

J4a, 4b Therefore, assembly average isotopic compositions are used for spent fuel assemblies.

Criticality Safety Analysis of SFP for Callaway Proprietary Information 3.3.6. 1 Core Operating Parameters HOL TEC INT E R NA I IONAL 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 [3], 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; Case 3.3.6.1.1:

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 100 K; Case 3.3.6.1.4:

Moderator temperature is decreased by 100 K; 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 Cooling 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 3.3.6.2.0:

Reference case. Cooling time of O hours; Case 3.3.6.2.1:

Cooling time of 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months ; 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 ; Case 3.3.6.2.4:

Cooling time of 1 year; Case 3.3.6.2.5:

Criticality Safety Analysis of SFP for Callaway Proprietary Information Case 3.3.6.2.6:

Cooling time of 10 years; Case 3.3.6.2.7:

Cooling time of 20 years.

Separate depletion calculations are performed for the cooling times above.

3.3.6.3 Integral and Removable Burnable Absorbers HOLTEC INT E RNATI ONAL 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 Al20rB4C or SiOz-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 10B, 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 ~k 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 Lip 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 Proprietary Information HOLTEC INT E RN Al IONAL Typically, at full power, most RCCAs are completely withdrawn from the active region of the fuel, while some RCCAs may be inserted only slightly into the active region. According to [19], the Control Bank D insertion during full power operation below 212 steps ( ~ 7.5 inches) is uncommon, [

]w,F_

Based on the core follow logs from Cycle 1 to Cycle 25 provided in [19], the burnup-weighted cycle-average Control Bank D insertion depth does not exceed 212 steps for all cycles except Cycles 1-2, while the tips of Control Bank C, which is typically only used for shutdown operation, are well above the active fuel region most of the reactor operation history. For Cycles 1-2, the maximum cycle-average Control Bank D insertion depth is determined, and the insertion depths considered in the analysis for the Hf-Zr and Ag-In-Cd RCCAs are presented in Table 5-5. [

]4a, 4b 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 UO2-Gd2O3 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 ~k 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:

The maximum number of Pyrex rods and WABA rods (see Table 5-5) are conservatively considered to be present along the entire length of the active fuel region; The Pyrex and WABA rods are conservatively considered to be present in the core for the entire fuel assembly irradiation history; Hl-2220020 Rev. 2 Page 15 of 118 Copyright © 2022 Holtec International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN T E R NAl lO NAL The maximum number of RCCA rods are inserted into the top part of the active fuel region for the entire fuel assembly irradiation history. Based on the maximum insertion depth during the full power operation in Table 5-5, an insertion of 8 inches is assumed for Ag-In-Cd RCCA, which corresponds to the topmost segment of the 18 segments considered in the axial burnup distribution. For Hf-Zr RCCA, an insertion of 12 inches (3 out of 36 axial segments) is assumed;

. [

JW.4a, 4b The IBA are conservatively considered to be present along the entire length of the active region; The integral and removable burnable absorbers are modeled with nominal dimensions.

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:

[

]w IFBA rods; Case 3.3.6.3.6:

[

]w IFBA rods; Case 3.3.6.3.7:

WABA rods and [

]w IFBA rods; Case 3.3.6.3.8:

WABA rods and [

]w 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 Hl-2220020 Rev. 2 Page 16 of 118 Copyright © 2022 Holtec International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TERNA "I IQNAL increased neutron loss and therefore decreased neutron flux towards the top and bottom end of 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 profiles for a large number of assemblies from different plants.

The source of profiles is the axial burnup database documented in [24] 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 1034 for the Westinghouse 17x17 assemblies with an enrichment range of 1.60 - 4.62 wt% 235U and a burnup range of 2.1 - 53.5 GWd/mtU. [

J4a, 4b The example bounding axial burn up profiles for WE 17x17 fuel generated for several burn up 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 burn up profile; Case 3.3.6.4.2:

Bounding WE 17x17 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 Hl-2220020 Rev. 2 Page 17 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TE RNATI ONAL databases. However, due to the large number and variety of profiles in these databases, any 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 [15] and [26] are applicable for the burnup credit in the Callaway SFP.

3.3.6.5 Reactivity Effect of Depletion Related Fuel Assembly 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:

Pellet densification: With the irradiation of the fuel assembly the pellet density initially increases and then decreases over depletion. While the fuel density is changing, this is solely due to changes in pellet dimensions as the mass within the fuel is unchanged [3],

hence the fuel to moderator ratio is not affected.

No additional calculations are therefore required.

Crud buildup: Crud buildup on the cladding increases the fuel to moderator ratio and reduces reactivity. No additional calculations are therefore required.

Fuel rod growth and creep:

Both clad creep down and fuel rod growth have the potential to decrease the fuel to moderator ratio in the geometry, thus potentially increasing reactivity.

To address clad creep down, the fuel rod cladding model is changed by reducing the clad ID such that the pellet-to-clad gap is only 0.001 inches, while simultaneously reducing the clad OD to preserve overall clad volume. Then, to address clad thinning due to fuel rod growth, the clad OD is further reduced to allow for the maximum possible fuel rod growth provided in Table 5-3.

Grid growth: Growth of the grid spacers (and corresponding increase in pitch between fuel rods) decrease the fuel to moderator ratio in the geometry, thus potentially increasing reactivity. The maximum grid growth is provided in Table 5-3. Despite a grid may experience uneven growth on outer strips and not evenly spread across the fuel rod cells, it is conservatively applied to all fuel rods in the lattice.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TE RNA TIONAL 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 3.3.6.5.0:

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 kett value.

Therefore, 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.

3.3.6.6 Spent Fuel Isotopic 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.

Uncertainty depl = [ ( kcalc, -

kcalc,) + 2 X

( a} + <Ti)] X 0.05 Equation 3.3-2 where kcatc1

- calculated kett value for spent fuel; kcatc2

- calculated kett value for fresh fuel; a,

- standard deviation of calculated kett value for spent fuel; a2

- standard deviation of calculated kett 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.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ERNA l IONAL The established depletion uncertainty covers all 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.

3.3.6.6.2 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 burn up 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 balded, 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.

BiasMAFP = [ ( kcalc, - kca1cJ + 2 X

( o-f + o-})] X 0.015 Equation 3.3-3 where kcaic1

- calculated kett value for spent fuel with all actinides and fission products; kca1c2

- calculated kett value for spent fuel with the major actinides only; a,

- standard deviation of kca1c1 ;

cr2

- standard deviation of kca1c2 -

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT E RNAl IO NAI 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 burn up 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 burn up, but all minor actinides 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 [27], 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. 1 Calculation of a Maximum ketr Value Applying all the considerations from the previous sections, the calculated kett value (kca1c) is determined using the design basis model, as summarized in Figure 3-2. The maximum kett 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.

k:}1 = kcalc + TCF Equation 3.3-4 where kcalc

- calculated kett value, as described in Figure 3-2; 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 MCNPS code bias and bias uncertainty associated with borated water (see Paragraph 3.2.2.1) are applied. The determined maximum kett values are used to show compliance with the regulatory limit.

3.3. 7.2 Determination of the Spent Fuel 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 (kett), 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 kett when determining the burnup vs. enrichment curves for the loading configurations with spent fuel.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TE R N A"l IONAL 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 of calculations 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 ket1 is not exceeded.

The minimum required burnups are then matched by a third-order polynomial fit as a function of enrichment.

3.3. 7.3 Maximum kett Calculation 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 (ket1) is 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 ket1 values are used to show compliance with the regulatory limit. A discussion of the 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 of different regions within a rack; Interfaces of the same region within a rack.

3.4.1 Interfaces between different SF Rs All storage racks in the Callaway SFP contain neutron absorber panels on the exterior surfaces facing adjacent racks (29]. 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 Hl-2220020 Rev. 2 Page 22 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT E RN A l IONAL (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 Interfaces between Storage Racks and the SFP Wall All storage racks in the Callaway SFP also contain neutron absorber panels on the exterior surfaces facing the SFP wall [29], and are separated from the wall by a water gap. 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:

A 16x12 array of the SFR storage cells is used, containing two 8x12 arrangements for the different loading regions, which is large enough (i.e., 4 or more rows of storage cells for each region as recommended in [3]) to eliminate the impact of the outer edge of the model on the interface reactivity; The periodic boundary conditions discussed in Section 3.3 are still used, even though this may result_ in additional interfaces at the model boundaries. This is _conservative, since it would amplify the reactivity effect from any interface condition.

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 riot 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 Proprietary Information HOLTEC INT E RNATI ONAL 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.

[

J4a, 4b 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 Hl-2220020 Rev. 2 Page 24 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT E RN A i IONAL between the fresh assemblies in the Region 1 pattern. However, in the interest of clarity and 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 kett 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 above just 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 8, Section 8-4.0. 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 8, Section 8-4.0, 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 Hl-2220020 Rev. 2 Page 25 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT E RN ATION A L fuel transfer system cart for transporting fuel into containment is located at a reasonable 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.

To verify this, the reactivity calculations are performed for the FRSR in Table 5-10, using the 2x2 rack model discussed in Section 3.3. The uniform storage of the FRSRs loaded with the fresh fuel rods of highest permissible enrichment are considered. The FRSR radial positioning is evaluated according to the discussions in Subsection 3.3.5. Since the cladding condition of the fuel rods loaded into the FRSR is unknown, the cladding is conservatively neglected, i.e., bare Hl-2220020 Rev. 2 Page 26 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TE RNAfl ON A L stack of the fuel pellets is modeled inside each storage tube of the FRSR. 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 fuel lattice with the missing rods using the 2x2 rack model discussed in Section 3.3. Conservatively, a partially vanished fuel pin (i.e., a severed fragment of a fuel rod left behind during failed reconstitution efforts) is neglected, and the calculation model assumes a vacant water cell along the entire active fuel length.

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 fuel rods, at some point, a negative effect of the loss of the fissile materials becomes dominant. According to studies in [30], the most reactive configurations involved missing rods

( ~ 10% of total) in the inner regions of the assemblies, and the maximum increase in kett value is shown to be less than 0.015 with the guide tubes present and less than 0.019 with the guide tubes removed. 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. 2 Page 27 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INTERNAl lONAL 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 already 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 SFR);

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

Incorrect loading curve (multiple mislead);

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 kett 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 SFP 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 Proprietary Information 3.6.2 Dropped Assembly - Horizontal HOLTEC INT ERNA T IONAL 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 Assembly - Vertical 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 misleading of a fresh assembly discussed in Subsection 3.6.5.

The vertical drop is therefore bounded by the misleading 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% mu) is accidentally mislocated or dropped outside of a storage rack adjacent to the other fuel assemblies. Considering that all exterior storage rack walls include the attached BORAL' neutron absorber panels [29] 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 mislead (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 mislead of a single fresh fuel assembly of the highest permissible enrichment (5.0 wt% mu) is considered in a storage cell that provides the largest positive reactivity increase. The following cases are evaluated:

Case 3.6.5.1:

Misleading into an empty storage cell in Region 1; Case 3.6.5.2:

Misleading into one of the storage cells intended to store a spent fuel assembly in Region 2.

The mislead 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 mislead (also see Subsection 3.6.6).

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT E RN A l IONAL boron concentration is determined for each case that ensures that a maximum kett value does not exceed the regulatory limit.

Additionally, the mislead 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 misleads are precluded by the double contingency principle, a multiple mislead 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 mislead of spent fuel assemblies, which were intended to be loaded into Region 2 with 20 years of cooling time, is considered for Region 2 with O hours 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 kett 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 SFP 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 Hl-2220020 Rev. 2 Page 30 of 118 Copyright © 2022 Ho/tee Jnternotional, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TE RNArlONA L can occur to reduce the boron concentration to the level needed to maintain kett less than or equal to 0.95. The methodology related to the boron dilution accident follows the general equation for a constant-volume boron dilution, which is conservative:

where F

Ct = C0e -vt Ct

- boron concentration at time t; C0

- initial boron concentration; V

- credited volume of water in the SFP; F

- flow rate of unborated water into the SFP.

Equation 3.6-1 This equation assumes the unborated water flowing into the SFP mixes instantaneously with water in the SFP. The volume of water in the SFP is conservatively set as the volume of water above the top of the SFRs, as shown in Table 5-8. For convenience, the above equation may be re-arranged to permit calculating the time required to dilute the soluble boron from its initial concentration to a specified minimum concentration, which is given below.

V C0 t =-ln-F Ct Equation 3.6-2 If Vis expressed in gallons and Fin gallons per minute (gpm), the time, t, will be in minutes.

3. 7 Margin Evaluation 3.7.1 Neutron Absorber Aging Effects The SFR design in the Callaway SFP contains the BORAL' poison panels constricted in-between the steel box and steel sheathing. lndustrywide, there have been no indications of a loss of BORAL' material of a nature that diminished neutron-absorbing capability [31].

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 BORAL' poison areal density, an evaluation of the potential reactivity effect of such lower areal density, and an evaluation of available margin in the criticality analysis to offset such effect is performed and documented in the following subsections.. If an unanticipated BORAL' 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.

Criticality Safety Analysis of SFP for Callaway Proprietary Information 3.7.2 BORAL' Panel 10B Areal Density HOL TEC INT ER N A f IONAL The evaluation of the reactivity effect in terms of b.k per three changes in BORAL' 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 b.k 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 prevail in the SFR BORAL' panels, which provides additional margin.

3.7.3 Criticality Analysis Safety Margin The following calculations are performed to estimate available margins in the criticality analysis:

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TE RN Al l ONAL 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 SFP (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 it's 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 SFP for Callaway Proprietary Information HOLTEC INT E RNAIIO NAL Table 3 Summary of Area of Applicability of the MCNPS Benchmark Parameter Design Application Benchmarks [13]

Fissionable Material 23su, 239Pu, 241 Pu Isotopic Composition 235U/U, wt%

2.0 - 5.0 Pu/(U+Pu), wt%

n/a

- Physical Form UO2

- Fuel Density, g/cm3

~ 10.6312 Moderator Material (Coolant)

H

- Physical Form H2O

- Density, g/cm3 around 1.0 Reflector Material H

- Physical Form H2O

- Density, g/cm3 around 1.0 Reflector Reflective or Periodic Boundary, Water Reflector Absorber and Separating Material Soluble None, Boron (0 - 2165 ppm)

Rod n/a Plate Water, Steel, Baral Geometry

- Lattice type Square Lattice Pitch, cm 1.26 Temperature, K 277.2 - 349.8 Neutron Energy Thermal spectrum EALF, eV 0.0883 - 0.7640

~

1 [

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 3 MCNPS Benchmark Analysis for Various Fuel and Water Subsets of Experiments No.of Bias Normality Experiment Description Bias1 Linear Correlation exp.

Uncertainty2 X2 (Pd(x2;d))

1 [

Page 35 of 118 4a, 4b

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N ATIONAL Table 3 Significant Trending Analysis for Callaway Parameters Experiment Linear Correlation Analysis Analysis Parameter Description Parameter Value 1 Trend Bias -

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 Proprietary Information HOL TEC INT ER N ATIONAL Table 3-4-Summary of MCNPS Code Validation Bias and Bias Uncertainty Applicable Pure Water Borated Water Description Loading Bias1 Bias Bias1 Bias Regions Uncertainty Uncertainty Fresh Fuel 1

0 0.0054

-0.0007 0.0078 Spent Fuel 2

-0.0003 0.0083 0

0.0092

(-0.0014)

(-0.0011) 1 The values in parentheses are based on trending analyses in Table 3-3.

1 Deleted Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 3 List of Spent Fuel lsotopes1 MCNP ZAID [8]

2[

~~

3 The isotopes considered as the major actinides are balded [28].

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT E RNAl IONAL Table 3-6-Bounding Axial Burnup Profiles for Westinghouse 17x17 Fuel Type [15)

Axial Assembly Average Burnup (GWd/mtU)

Segment 7.5 17.5 27.5 37.5 i:: 45 (18 = Top)

Relative Burnup per Segment1 4a, 4b 1

2 3

4 5

6 7

8 9

10 11 12 13 14 15 16 17 18 1 Segment burnup divided by assembly average burnup.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TE RNAT IONAL Table 3 Bounding Axial Burnup Profiles from NUREG/CR-6801 [26]

1 Burnup Ranges (GWd/mtU)

> 46 42-46 38-42 34-38 30-34 26-30 22-26 18-22 14-18 10-14 6-10

<6 1

0.582 0.666 0.660 0.648 0.652 0.619 0.630 0.668 0.649 0.633 0.658 0.631 2

0.920 0.944 0.936 0.955 0.967 0.924 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 1.150 1.208 1.019 1.091 1.135 4

1.105 1.081 1.080 1.104 1.103 1.097 1.103 1.094 1.215 0.857 1.070 1.133 5

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 1.112 1.106 1.101 1.109 1.048 1.208 0.754 0.989 1.069 7

1.105 1.086 1.092 1.108 1.102 1.103 1.112 1.064 1.197 0.785 0.978 1.053 8

1.100 1.085 1.090 1.105 1.097 1.112 1.119 1.095 1.189 1.013 0.989 1.047 9

1.095 1.084 1.089 1.102 1.094 1.125 1.126 1.121 1.188 1.185 1.031 1.050 10 1.091 1.084 1.088 1.099 1.094 1.136 1.132 1.135 1.192 1.253 1.082 1.060 11 1.088 1.085 1.088 1.097 1.095 1.143 1.135 1.140 1.195 1.278 1.110 1.070 12 1.084 1.086 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 1.251 1.120 1.073 15 1.050 1.069 1.057 1.056 1.059 1.047 1.041 1.049 0.756 1.193 1.101 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 0.833 0.811 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 Proprietary Information HOL TEC INT E RNA'l IO NAL Figure 3 Radial Cross-Section View of the MCNPS Design Basis Model of the SFR Hl-2220020 Rev. 2 Page 41 of 118 Copyright © 2022 Ho/tee International, all rights reserved 4a, 4b

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT E RNAl IONAL I

Bounding fuel assembly design (Subsection 3.3.1)

Given cooling time Given enrichment Bounding COP (Paragraph 3.3.6.1)

Bounding IBA and fuel inserts (Paragraph 3.3.6.3)

Uniform/bounding axial burnup profile (Paragraph 3.3.6.4)

-I* *---------+J

- Spe-nt-f-uel-!s-_o-top-ic_ l _____ ~

pq!!i!qp&p composot,ons j

Spent Fuel

~--------------------------

Bounding fuel assembly design (Subsection 3.3.1)

Bounding SFR parameters (Section 3.3)

Bounding assembly radial positioning (Subsection 3.3.5)

Given 2x2 SFR loading configuration (Section 1.0)

Unborated (or borated) SFP moderator Infinite array of SFR storage cells (Section 3.3)

Page 42 of 118

Hl-2220020 Rev. 2 Criticality Safety Analysis of SFP for Callaway Proprietary Information Figure 3 Determination of the Total Correction Factor Copyright © 2022 Ho/tee International, all rights reserved HOLTEC IN f ER N ATIONAL Page 43 of 118 4a, 4b

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TER N ATIONAL Figure 3 Radial Cross-Section View of the MCNPS Model for the SFR Interfaces Hl-2220020 Rev. 2 Page 44 of 118 Copyright © 2022 Ho/tee lnternotional, all rights reserved 4a,4b

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N ATIONAL

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER NAl IONA I Figure 3 Radial Cross-Section View of the MCNPS Model for the FRSR Hl-2220020 Rev. 2 Page 46 of 118 Copyright © 2022 Holtec International, all rights reserved 4a,4b

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TER NA I IONAL Figure 3 MCNPS Model of the Heterogeneous BORAL ' Panel Hl-2220020 Rev. 2 Page 47 of 118 Copyright © 2022 Ho/tee International, all rights reserved a, 4b

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N ATIONAL 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 3.3.

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:

Assumption, Approach C, or R Justification (Note 1)

The provided tolerance for the fuel rod pitch in Table 5-2 is too large to be applicable to each fuel cell in the The fuel rod pitch tolerance is adjusted by the lattice, and it is of typical magnitude 1

number of the rod-to-rod gaps across the fuel R

of the assembly width tolerance.

Therefore, this tolerance is divided assembly width.

by the number of the rod-to-rod gaps across the fuel assembly width and conservatively applied to all fuel rods in the lattice.

2 No credit is taken for 234U and 236U in fresh C

The model neglects additional fuel.

neutron absorption.

Dishing and chamfering of the fuel pellets are The amount of fissile materials is 3

neglected, i.e., fuel is always modeled as solid C

increased.

cylinder inside the cladding.

Fresh and/or spent fuel with a uniform The same bounding enrichment is enrichment are considered. Lower enriched assumed along the entire active 4

blankets are neglected. Therefore, there is no C

length for each fuel pin, which axial or planar variation in fuel enrichment increases the amount of fissile along the entire active fuel length.

material.

Annular pellets used for axial blankets of 5

some rods are neglected, i.e., solid fuel stack C

The amount of fissile materials is is considered along the entire active fuel increased.

length.

6 7

8 9

10 11 Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC I NT ER N ATIONAL Assumption, Approach C, orR Justification (Note 1)

All fuel cladding and guide/instrument tube The model neglects the trace material is modeled as pure zirconium, while C

elements in the alloy which may the actual fuel cladding consists of one of provide additional neutron several zirconium alloys.

absorption.

The amount of material, which may Minor parts, such as grid straps and minor provide additional neutron structural rack components, are neglected and R

absorption, is reduced. The soluble replaced by water.

boron requirements are increased by additional 50 ppm in accordance with Paragraph 5.1.1 of [3].

While it may neglect some reflection All fuel and rack structures above and below from steel structures in those areas, the active region of the fuel assembly are C

it also neglects the absorption in those steel structures, and maximizes neglected and replaced by unborated water.

the axial water reflection. See Paragraph 5.1.1 of [3].

The hardening of the spectrum is In the depletion calculations with burnable applied to axial sections that do not absorbers (I8A and fuel inserts), the burnable C

contain absorbers, which increases absorber is modeled over the entire active the reactivity effect associated with length.

the presence of these absorbers.

See Paragraph 4.2.1 of [3].

No credit is taken for any residual I8A that The amount of neutron absorbers is may remain after irradiation of the fuel C

reduced. See Paragraph 5.1.6 of [3].

assembly.

8ORAL' panel has an inner core consisting of 84C and aluminum between two outer layers consisting The BORAL rM absorber panel is modeled as a R

of aluminum only. Considering the single sheet of homogeneous material.

poison 108 areal density is maintained, such simplification is expected to provide a statistically negligible effect on results.

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

Criticality Safety Analysis of SFP for Callaway Proprietary Information 5.0 INPUT DATA 5.1 Fuel Assembly Designs HOL TEC INT ER N Al IONAL 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 (VS), Westinghouse 17x17 Vantage+ (V + ), and Framatome GAIA 17x17 (GAi).

The mechanical design of STD, OFA and VS assemblies includes fuel cladding, guide and instrument tubes made of Zircaloy-4'. V+ fuel offers several design changes relative to fuel stack configuration and structural material (ZIRLO'). GAi fuel cladding, guide and instrument tubes are made of MS'.

Apart from the structural material and annular pellets (see Section 4.0), the only difference between VS and V+ fuel designs that is relevant to the criticality analysis is the instrument tube size, hence V+ with a lower instrument tube thickness (i.e., increased amount of moderator) is conservatively considered in the analysis, and the results are applicable to both VS and V+ fuel assembly designs. 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 Callaway 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, WABA 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 (ZrB2).

The burnable absorber rods contain a certain amount of 10B, in the form of Al2O3-84C or SiOrB2O3 in annular pellets inside a Zircaloy or SS cladding. The control rods consist of highly neutron absorbing material inside the SS cladding.

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).

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

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 design specifications for the Gd and IFBA rods are shown in Table 5-6.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TER N ATIONAL The absorber material of IBA and burnable absorber rods is axially centered if absorber length is lower than the active fuel length (except for some IFBA rods loaded in Cycles 7 through 11 with the axial offset by 3 inches).

5.4 Spent Fuel Rack Design The SFP contains a single type of BORAL' SFR designed 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 SS 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 Table 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 [13].

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).

5. 7 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 Proprietary Information HOLTEC INT ER N ATIONAL Table 5-1 -Specification of the Fuel Assembly Parameters [20)

Fuel Assembly Design Westinghouse Westinghouse Westinghouse Framatome STD OFA v+1 GAIA (21)

Fuel Assembly Data Fuel Rod Array 17x17 Number of fuel rods 264 Distance from Bottom of Fuel Assembly to Beginning of Active Length, inches Active Fuel Length, inches Fuel Rod Pitch, inches Axial Blanket Length, inches Fuel Rod Data Clad OD, inches Clad ID, inches Clad Material Pellet ID, inches Pellet OD, inches As-Built U02 Density (Max %TD)

......c;uide/lnstrument Tube Data Number of Guide Tube

I--

24 Guide Tube OD, inches Guide Tube ID, inches Guide Tube Material Number of Instrument Tube 1

W, F

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC I NT ER N ATIONAL Table 5 PWR 17x17 Fuel Assembly Manufacturing Tolerances Parameter Value1 Reference Fuel Rod Pitch, inches

-W,F

[20]

Pellet OD, inches

[20], [21]

Clad OD, inches

[21]

Fuel Enrichment, wt% 235U

[20], [21]

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

ZrB2 Coating Loading,%

[20]

Table 5 PWR 17x17 Fuel Assembly Depletion Related Geometry Changes Parameter Value Reference Maximum Fuel Rod Growth, inches r

,w,F

[21]

Maximum Fuel Grid Growth, inches L

J

[20]

1 Bounding values for all fuel assembly types are summarized.

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 5 Core Operating Parameters Parameter Value Maximum Core Moderator Temperature, K Maximum Fuel Temperature, K Reactor Specific Power, W/gU Soluble Boron Concentration (cycle average)\\ ppm 1150 In-Core Assembly Pitch, inches 8.466 1 Upper bound burnup-weighted cycle average soluble boron concentration.

- V,F HOL TEC IN TER N Al IONAI Reference (21]

(20]

(19]

Page 54 of 118

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 5 Specification of the Fuel Inserts [20)

Parameter Pyrex Maximum Number of Rods per Assembly1 20 Maximum Insertion Depth2, inches Burnable Absorber Material Absorber Content, wt%

Burnable Absorber Density, g/cc Burnable Absorber Composition, wt%

Si 0

,oB

,,B Al C

Inner Clad Material Inner Clad ID, inches Inner Clad OD, inches Burnable Absorber ID, inches Burnable Absorber OD, inches Outer Clad Material Outer Clad ID, inches Outer Clad OD, inches Burnable Absorber Length, inches 1 See Figure 5-1 for the fuel inserts layouts.

2 See Subparagraph 3.3.6.3.2.

3 [

4 Hl-2220020 Rev. 2 Full Borosilicate Glass (SiO2-B2O3)

Ag-In-Cd Page 55 of 118 w

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 5 Specification of the Integral Burnable Absorbers Parameter Value IFBA Rods [20]

ZrB2 Coating Loading, mg 10B/inch 10B Enrichment of ZrB2, 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]

Gadolinia Loading, wt% Gd2O3 Number of the Gd rods Gd Stack Length, inches Gd Rods Layout See Figure 5-1 Burnable Absorber Composition See Table 5-9 Hl-2220020 Rev. 2 Copyright © 2022 Ho/tee International, all rights reserved HOL TEC INT ER N ATIONAL w

F Page 56 of 118

1 [

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TER N A T IONAL Table 5 Specification of the Callaway SFR Parameters Parameter Value [1], [29), [32), [33]

Rack Type PWR BORAL' Number of Racks 18 Storage Rack Material Stainless Steel Rack Height (Top of Baseplate to Top of Rack),

169 +/- [

]4a, 4b inches Distance from Rack Baseplate to Bottom of Neutron 2.6875 +/- [

]4a, 4b Absorber, inches Storage Cell ID, inches 8.77 +/- [

]4a, 4b Storage Cell Pitch, inches 8.99 +/- [

]4a, 4b Storage Cell Box Wall Thickness, inches 0.075 +/- [

]4a, 4b Inner Sheathing Thickness, inches 0.035 +/- [

]4a, 4b Peripheral Sheathing Thickness, inches 0.075 (nom.)

Neutron Absorber Panel BORAL' Type Al+ 84C Thickness, inches 0.101 +/- [

]4a, 4b Width, inches 7.5 +/- [

]4a, 4b Length, inches 145 [

]4a, 4b 10B Areal Density (g/cm2) 0.0324 (nom.), [

]4a, 4b

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N ATIONAi Table 5 SFP Operating Parameters [19], [29], [34], [35]

Parameter Value Maximum Moderator Temperature, °F 170 (76.67 °(} 1 Soluble Boron Concentration, ppm 2165 Minimum Water Level (Volume) in the SFP, inches

-19.5 (401295 gal)

Water Volume above the SFRs2, gal 242932 Water Volume in the RMWST (0 ppm}, gal 153032 Soluble Boron Concentration in the RWST, ppm 2350 Total CCW System Volume, gal 78000 Maximum Blow-Down Rate, gpm 208.5 Probable Maximum Precipitation3, gpm 483 Maximum Operator Response Time for Internal Flooding Events, min 35 SFP Boron Concentration Surveillance Interval, days 7

Annunciator Setpoint for Low SFP Level (Volume), inches

-1.31 (417506 gal)

Annunciator Setpoint for High SFP Level (Volume), inches

+8.69 (426930 gal)

SFP Water Overflow Level, inches

+20.69 (437048 gal) 1 A temperature range of 4 - 120 °C is considered in the analysis.

2 Calculated for the minimum water level above the top of the SFRs of 23 feet (i.e., S97.56" x 340.22" x 276").

3 Calculated for an all-season 6-hour rainfall with an accumulation of 25.4 inches.

1 [

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N A flONAL Table 5 Material Compositions of the Major Design Components Element MCNP ZAID [8]

Weight Fraction Stainless Steel (Density - 7.84 g/cm3) 24050 0.0079050 24052 0.1585266 Cr 24053 0.0183218 24054 0.0046467 Mn 25055 0.0200100 26054 0.0389826 26056 0.6345800 Fe 26057 0.0149174 26058 0.0020200 28058 0.0671977 28060 0.0267760 Ni 28061 0.0011834 28062 0.0038348 28064 0.0010082 Zirconium (Density - 6.55 g/cm3) 40090 0.5070612 40091 0.1118009 Zr 40092 0.1727810 40094 0.1789110 40096 0.0294379 BORAL' C[

]4a, 4b) 5010

-4a,41 B

5011 C

6000 Al 13027

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN T ER N ATIONAL Table 5 Material Compositions of the Major Design Components Element MCNP ZAID [8]

Weight Fraction Pure Water (Density - 1.0 g/cm3) 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

1002 0.0000257 8016 0.8853540 0

8017 0.0022921 5010 0.0000922 B

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 IFBA C[

Jw) w 5010 B

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC I NT ER N ATIONA L Table 5 Material Compositions of the Major Design Components Element MCNP ZAID [8]

Weight Fraction Fresh U021 (5.0 wt% mu, Density-10.6312 g/cm3) 92235 0.0440800 u

92238 0.8374200 0

8016 0.1185000 Fresh U02-Gd2031 (5.0 wt% mu, [

]F) 92235

-F u

92238 0

8016 64152 64154 64155 Gd 64156 64157 64158 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 Proprietary Information Table 5 Fuel Rod Storage Rack Parameters Parameter Value (19)

Fuel Rod Array Number of Storage Tubes Normal Storage Tube OD, inches Normal Storage Tube Thickness, inches Enlarged Storage Tube OD, inches Enlarged Storage Tube Thickness, inches Storage Tube Pitch, inches Storage Tube Material Hl-2220020 Rev. 2 Copyright © 2022 Ho/tee International, all rights reserved HOL TEC INT ER N ATIONAL i--w Page 62 of 118

Hl-2220020 Rev. 2 Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N ATIONAL W,F Figure 5 Considered PWR 17x17 Fuel Assembly Layouts Page 63 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC I NT ER N A 'l IONAL Inner Sheathing External Sheathing Box Poison

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-. --)1 1,

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Criticality Safety Analysis of SFP for Callaway Proprietary Information Poison Sheathing I

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Missing Pin Iii]

Iii m

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G75 Page 66 of 118

Criticality Safety Analysis of SFP for Callaway Proprietary Information 6.0 COMPUTER PROGRAMS HOLTEC INT ER N A1 IONAL Holtec International maintains an active list of QA validated computer codes on the Company's 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-2115064 Code name (listed in the ACPL)

CASMOS MCNPS Python SX Code version# (approved in the ACPL) 2.08.00 1.51 1.0 Code name and versions used in previous revisions of the report (if different than listed N/A above)

All calculations were performed on computers under Windows at Holtec's offices.

Criticality Safety Analysis of SFP for Callaway Proprietary Information 7.0 CALCULATIONS AND RESULTS HOL TEC INT ER N Al IONAL 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 Callaway 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% mu 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 GAi 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% mu 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% mu 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 Reactivity Effect of the 84C Particle Size The calculations are performed for all storage configurations listed in Chapter 1.0 to estimate a reactivity effect of the heterogeneous 8ORAL' panel model with the variable 84C 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% mu and fuel burnups along the expected region-Hl-2220020 Rev. 2 Page 68 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N ATIONAL specific loading curve at the cooling time of O hours are considered. The results presented in Table 7-26 demonstrate that [

)4a, 4b 7.4 Reactivity Effect of SFP Water Temperature As discussed in Subsection 3.3.4, the reactivity effect of SFP water temperature and density 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 O hours 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 Operating 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 O hours 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 concentrati.on 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.

Criticality Safety Analysis of SFP for Callaway Proprietary Information 7.6.2 Reactivity Effect of Cooling Time HOL TEC IN TER N A l lONAL 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 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 IBA 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.

Based on the results, [

J4a, 4b Hence more abundant and representative WABA inserts are justified 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 [

J4a, 4b_

The reactivity effect of the Hf-Zr RCCA (strong absorber) is also small at low burnup but substantially increases at higher burnups. [

J4a, 4b The comparison of the IBA configurations with [

bounding.

Hl-2220020 Rev. 2

Criticality Safety Analysis of SFP for Callaway Proprietary Information In accordance with [3], [

]W,4a, 4b_

7.6.4 Reactivity Effect of Axial Burnup Profiles HOL T EC I N T ER N ATIONAL 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% mu 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 7-1 0 are considered as bias and bias uncertainty for determination of the maximum kett 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% mu 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 7-11.

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 model.

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 Proprietary Information 7.7.1 Determination of the Spent Fuel Loading Curves HOLTEC IN TER N ATIONAL 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 kett 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 kett 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 kett 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 Maximum kett Calculation with Borated 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 kett 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.

Since all loading curves are established to meet the target kett (see Paragraph 3.3.7.2), there is no particular cooling time that would be bounding for the interface analysis.

For instance, an increase of the credited cooling time in Region 2 is compensated by a decrease of the burnup requirement, so the kett value is maintained. Therefore, all qualified combinations of the burnup Hl-2220020 Rev. 2 Page 72 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TER N Al IONAL and cooling time are equivalent as the spent fuel assembly parameters in the transitional pattern. However, since with the increase of fuel burnup the reactivity-dominating area shifts from the axial center towards the assembly ends, a lower burned fuel (higher cooling time requirement) may be more appropriate for the interface analysis with fresh fuel. Nevertheless, to ensure bounding condition near the interface between spent and fresh fuel assemblies, both the lowest and highest cooling times (i.e., 0 and 20 years) are considered for spent fuel. For the same reason, both the bounding axial burnup profile and flat profile are considered.

As far as the fuel assembly positioning in the storage cells, both the cell centered and eccentric fuel positioning (i.e., where all assemblies are moved towards the interface as permitted by the rack geometry) are considered. [

J4a, 4b 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 kett 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.

[

]4a, 4b 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. Conservatively, the isotopic composition at the cooling time of O hours is used. Since Hl-2220020 Rev. 2 Page 73 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC I NT ER N A l IONAL the fuel burnup of assembly R87 is low, it is assumed to be stored in Region 1, while all other 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 mislead and determine the minimum required soluble boron concentration in the SFP. 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 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 rack geometry, are considered. Additional calculations are performed to estimate the reactivity effect of a single fresh fuel assembly mislead [

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.

7.10.2 Incorrect 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 Taple 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.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N A l IONAL The calculations show that the required dilution volume to reduce the soluble boron content down to the minimum concentration required for the normal conditions exceeds the total volume of the normal makeup source to the SFP (i.e., RMWST) by more than a factor of 2. The alternate source of makeup to the SFP is the RWST, which contains borated water with the boron concentration that exceeds the minimum concentration in the SFP. Therefore, normal operations, or hypothetical equipment and human performance deficiencies associated with the boron dilution event, cannot credibly challenge the SFP boron concentration used in the analysis.

In case of the high flow rate accident, the SFP volume would increase rapidly, and the High-Level Alarm Setpoint would be reached in several minutes (or even less, if the SFP water level before the accident is above the Low-Level Alarm Setpoint as expected). However, even if the level indication is neglected, only a small fraction of water volume ( ~ 11 %) needed to dilute to the minimum concentration gets to the SFP before overflow without any response. At this point, the SFP overflow is detected in the fuel building sumps with the control room notification.

Considering a maximum operator response time to arrest the cause of a flooding event that is verified by the internal flooding analysis for Callaway [35], the flow rate required to challenge this response time after the SFP overflow is determined. The result shown in Table 7-23 is more than an order of magnitude greater than the highest break flow rate in the internal flooding analysis and an order of magnitude greater than rainwater flow rate if the station maximum precipitation over the entire fuel building roof is funneled directly into the SFP.

The CCW system is a potential source for the low flow rate boron dilution, but the total amount of water is bounded by the RMWST. Therefore, even if both trains of CCW were completely mixed with the SFP, it is not credible for this dilution mechanism as well to challenge the SFP boron concentration used in the analysis.

Small dilution flow around pump seals and valve stems or mis-aligned valves could possibly occur in the normal soluble boron control system or related systems. Such failures might not be immediately detected. The leakage rate from these water sources that can cause an undetected challenge to the credited concentration is determined and presented in Table 7-23. Unless simultaneous failures allowed both supply and return of water (excluded by double contingency), this case is bounded by the high flow rate accident. Emergency makeup from alternative sources, like Essential Service Water or Firewater, is possible during accidents.

However, such circumstances would inherently involve enhanced operator attention to SFP level to avoid overflow.

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 SFP for Callaway Proprietary Information 7.11 Margin Evaluation HOLTEC INT ER N Al IONAL The BORAL' 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 O 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 BORAL' panel 10B areal densities as well as the final polynomial fits for the areal density as a function of ilk 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 margin for each considered configuration is calculated as a sum of the lowest individual margins. Specifically, the calculation case with no IBA during irradiation is considered for spent fuel, and the calculation case for [

]w is considered for fresh fuel with the IBA.

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

cs QI "'

a...

E~

i E

-5 '$.

c,

.. "ti

-~ i i 3: "

w --

5.0 0

2.0 5

3.5 30 5.0 45 Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7 Bounding Fuel Assembly Design HOLTEC INT ER N A flONAL Framatome Westinghouse Westinghouse Westinghouse GAIA STD OFA V+

(Reference)

Maximum Reactivity kcalc 1 kcatc Ak kcalc Ak kcatc Ak Region 1 0.8323 0.8314

-0.0009 0.8441 0.0118 0.8446 0.0123 V+

Region 2 (0 hours0 days 0 hours 0 weeks 0 months ) 0.9587 0.9566

-0.0020 0.9525

-0.0062 0.9526

-0.0060 GAIA 0.9552 0.9535

-0.0017 0.9491

-0.0061 0.9492

-0.0060 GAIA 0.9586 0.9571

-0.0015 0.9542

-0.0044 0.9543

-0.0043 GAIA 1 All values are calculated kett-The standard deviation (o) of the calculations is up to 0.0004.

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7 Reactivity Effect of Fuel Assembly Parameters 2.0wt% 235U 3.5wt% 235U Description kca1c1 4k9s19s2 kcalc 4k9s19s Region 1 Burnup, GWd/mtU Nominal (Reference)

Minimum cladding OD Maximum cladding OD Minimum fuel rod pitch Maximum fuel rod pitch Minimum fuel pellet OD Maximum fuel pellet OD Maximum fuel enrichment Maximum fuel density Statistical combination Region 2 (0 hours0 days 0 hours 0 weeks 0 months )

Burnup, GWd/mtU 5

30 Nominal (Reference) 0.9587 0.9552 Minimum cladding OD 0.9597 0.0018 0.9561 0.0018 Maximum cladding OD 0.9581 0.0003 0.9541

-0.0002 Minimum fuel rod pitch 0.9582 0.0003 0.9544 0.0001 Maximum fuel rod pitch 0.9591 0.0012 0.9565 0.0022 Minimum fuel pellet OD 0.9582 0.0004 0.9543 0.0000 Maximum fuel pellet OD 0.9588 0.0010 0.9550 0.0007 Maximum fuel enrichment 0.9635 0.0057 0.9575 0.0032 Maximum fuel density 0.9605 0.0027 0.9564 0.0021 Maximum IFBA loading (spent fuel) 0.9586 0.0007 0.9552 0.0009 Statistical combination 0.0067 0.0049 1 All values are calculated ke11. The standard deviation (a) of the calculations is up to 0.0004.

HOLTEC I N T ER N A I IONAL 5.0wt% 235U kcalc 4k9s195 0

0.8446 0.8472 0.0037 0.8431

-0.0004 0.8449 0.0014 0.8455 0.0020 0.8445 0.0010 0.8450 0.0015 0.8461 0.0026 0.8473 0.0038 0.0064 45 0.9586 0.9588 0.0012 0.9565

-0.0012 0.9573

-0.0004 0.9597 0.0020 0.9577 0.0001 0.9590 0.0013 0.9601 0.0024 0.9596 0.0020 0.9590 0.0013 0.0043 2 Reactivity effect with a 95% probability at a 95% confidence level, determined using Equation 3.3-1. The maximum statistical combination of reactivity effects is bolded for each loading region.

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7 Reactivity Effect of SFR Parameters 2.0wt% 235U 3.Swt% 235U Description I

I kcalc 1 4k9s19s2 kcalc 4k9st9s Region 1 Burnup, GWd/mtU Nominal (Reference)

Minimum cell ID Maximum cell ID Minimum cell pitch Maximum cell pitch Minimum cell wall thickness Maximum cell wall thickness Minimum sheathing thickness Maximum sheathing thickness Minimum poison thickness Minimum poison width Statistical combination 1 All values are calculated kett-The standard deviation {cr) of the calculations is up to 0.0004.

HOL TEC IN f ER N A I IONAL 5.0wt% 235U kcalc 4k9s19s 0

0.8446 0.8414

-0.0021 0.8486 0.0051 0.8463 0.0028 0.8441 0.0006 0.8439 0.0004 0.8456 0.0021 0.8447 0.0012 0.8452 0.0017 0.8445 0.0010 0.8456 0.0021 0.0068 2 Reactivity effect with a 95% probability at a 95% confidence level, determined using Equation 3.3-1. The maximum statistical combination of reactivity effects is bolded for each loading region.

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7 Reactivity Effect of SFR Parameters 2.0wt% mu 3.5 wt% mu Description kcalc 1 4k9s{952 kcalc 4k9s/95 Region 2 (0 hours0 days 0 hours 0 weeks 0 months )

Burnup, GWd/mtU 5

30 Nominal (Reference) 0.9587 0.9552 Minimum cell ID 0.9594 0.0016 0.9549 0.0006 Maximum cell ID 0.9577

-0.0002 0.9553 0.0010 Minimum cell pitch 0.9593 0.0015 0.9558 0.0014 Maximum cell pitch 0.9579 0.0000 0.9539

-0.0004 Minimum cell wall thickness 0.9585 0.0006 0.9550 0.0007 Maximum cell wall thickness 0.9584 0.0006 0.9550 0.0007 Minimum sheathing thickness 0.9580 0.0002 0.9546 0.0003 Maximum sheathing thickness 0.9590 0.0012 0.9550 0.0006 Minimum poison thickness 0.9581 0.0003 0.9546 0.0003 Minimum poison width 0.9601 0.0023 0.9567 0.0024 Statistical combination 0.0034 0.0031 Hl-2220020 Rev. 2 Copyright © 2022 Holtec International, all rights reserved HOL TEC IN TER NATI ONAL 5.0wt% mu kcalc 4k9s19s 45 0.9586 0.9577 0.0000 0.9588 0.0012 0.9593 0.0016 0.9575

-0.0002 0.9583 0.0006 0.9593 0.0016 0.9584 0.0007 0.9590 0.0013 0.9588 0.0011 0.9593 0.0016 0.0034 Page 80 of 118

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TERNAl IONAL Table 7 Reactivity Effect of SFP Water Temperature Temperature, 2.0wt% 235U 3.Swt% 235U S.0wt% 235U Water Density kcalc 1 4k k,a1c 4k kcalc 4k Region 1 Burnup, GWd/mtU 0

4 °C, 1.0 g/cm3 (Reference) 0.8446 20 °C, 0.9982 g/cm3 0.8426

-0.0020 120 °C, 0.9431 g/cm3 0.8115

-0.0331 120 °C, 0.84879 g/cm3 0.7663

-0.0783 Region 2 (0 hours0 days 0 hours 0 weeks 0 months )

Burnup, GWd/mtU 5

30 45 4 °(, 1.0 g/cm3 (Reference) 0.9587 0.9552 0.9586 20 °C, 0.9982 g/cm3 0.9555

-0.0032 0.9528

-0.0024 0.9571

-0.0015 120 °C, 0.9431 g/cm3 0.9327

-0.0260 0.9326

-0.0227 0.9371

-0.0215 120 °C, 0.84879 g/cm3 0.9108

-0.0479 0.9069

-0.0484 0.9112

-0.0473 1 All values are calculated kett-The standard deviation (o) of the calculations is up to 0.0004.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER NAl IONAL Table 7 Reactivity Effect of Fuel Assembly Radial Positioning 2.0wt% 235U 3.Swt% 235U 5.0wt% 235U Description kcalc 1 Ak kcalc Ak kcalc Ak Region 1 Burnup, GWd/mtU 0

2x2, cell centered (Reference) 0.8446 2x2, eccentric in 0.8420

-0.0026 2x2, eccentric corner 0.8426

-0.0020 8x8, eccentric in 0.8432

-0.0013 Region 2 (0 hours0 days 0 hours 0 weeks 0 months )

Burnup, GWd/mtU 5

30 45 2x2, cell centered (Reference) 0.9587 0.9552 0.9586 2x2, eccentric in 0.9531

-0.0056 0.9508

-0.0044 0.9556

-0.0030 2x2, eccentric corner 0.9522

-0.0065 0.9507

-0.0045 0.9548

-0.0038 8x8, eccentric in 0.9541

-0.0046 0.9527

-0.0025 0.9569

-0.0017 1 All values are calculated kett-The standard deviation (a) of the calculations is up to 0.0004.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT E RN ATIONAL Table 7 Reactivity Effect of Core Operating Parameters 2.0wt%mu 3.5 wt% mu 5.0wt% mu Description kcalc 1 Ak kcalc Ak kcalc Ak Region 2 (0 hours0 days 0 hours 0 weeks 0 months )

Burnup, GWd/mtU 5

30 45 Reference 0.9587 0.9552 0.9586 Increased fuel temperature 0.9593 0.0006 0.9579 0.0027 0.9617 0.0031 Decreased fuel temperature 0.9563

-0.0024 0.9514

-0.0038 0.9537

-0.0049 Increased moderator temperature 0.9579

-0.0008 0.9552 0.0000 0.9595 0.0009 Decreased moderator temperature 0.9493

-0.0094 0.9381

-0.0171 0.9381

-0.0205 Increased soluble boron 0.9597 0.0010 0.9568 0.0016 0.9595 0.0009 concentration Decreased soluble boron 0.9572

-0.0015 0.9534

-0.0018 0.9565

-0.0020 concentration Increased power density 0.9586

-0.0001 0.9546

-0.0006 0.9581

-0.0004 Decreased power density 0.9588 0.0002 0.9545

-0.0007 0.9582

-0.0003 1 All values are calculated keff-The standard deviation (o) of the calculations is about 0.0003.

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7 Reactivity Effect of Cooling Time 2.0wt% mu 3.Swt% 235U Cooling Time kcalc 1 4k kcalc 4k Region 2 Burnup, GWd/mtU 5

30 0 hours0 days 0 hours 0 weeks 0 months (Reference) 0.9588 0.9552 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months 0.9567

-0.0021 0.9538

-0.0014 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 0.9567

-0.0021 0.9531

-0.0021 500 hours0.00579 days 0.139 hours 8.267196e-4 weeks 1.9025e-4 months 0.9544

-0.0044 0.9522

-0.0030 1 year 0.9535

-0.0053 0.9494

-0.0058 5 years 0.9516

-0.0071 0.9407

-0.0146 10 years 0.9495

-0.0093 0.9320

-0.0232 20 years 0.9473

-0.0115 0.9217

-0.0335 1 All values are calculated kett-The standard deviation (a) of the calculations is about 0.0003.

-0.0013 0.9570

-0.0016 0.9562

-0.0024 0.9532

-0.0054 0.9401

-0.0185 0.9290

-0.0296 0.9137

-0.0448 Page 84 of 118

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N Al IONAL Table 7 Reactivity Effect of Irradiation with the IBA and Fuel Inserts 2.0wt% 235U 3.Swt% 235U S.0wt% 235U Description kca1c1 4k kcalc 4k kcalc 4k Region 2 (0 hours0 days 0 hours 0 weeks 0 months )

Burnup, GWd/mtU 5

30 45 No IBA and Inserts (Reference) 0.9373 0.9411 0.9477 Pyrex rods 0.9481 0.0108 0.9508 0.0097 0.9576 0.0099 WABA rods 0.9476 0.0103 0.9498 0.0087 0.9558 0.0081 Ag-In-Cd RCCA rods 0.9372

-0.0002 0.9456 0.0045 0.9533 0.0056 (partial insertion)

Hf-Zr RCCA rods 0.9371

-0.0003 0.9531 0.0120 0.9610 0.0133 (partial insertion)

[

0.9454 0.0081 0.9442 0.0030 0.9498 0.0021

]W

[

0.9485 0.0112 0.9453 0.0042 0.9499 0.0022

]W

[

0.9587 0.0214 0.9552 0.0141 0.9586 0.0109

]W 1 All values are calculated kett-The standard deviation (o) of the calculations is about 0.0003.

Enrichment (wt% 235U) 2.0 3.5 5.0 Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7 Reactivity Effect of Axial Burnup Profile Bounding Bounding NUREG Burnup WE 17x17 Profile Profile (GWd/mtU)

{Reference) kcalc 1 kca1c 4k Region 2 (0 hours0 days 0 hours 0 weeks 0 months ) 5 0.9587 0.9573

-0.0014 30 0.9552 0.9520

-0.0032 45 0.9586 0.9585

-0.0001 1 All values are calculated kett-The standard deviation (o) of the calculations is about 0.0003.

-0.0001 0.9389

-0.0163 0.9478

-0.0108 Page 86 of 118

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TERNATIONAL Table 7 Reactivity Effect of Depletion Related Fuel Assembly Geometry Changes 2.0 wt% 235U 3.5 wt% mu 5.0wt% mu Description kcalc 1 Ak Uncgs/9s2 kcalc Ak Uncgs1gs kcalc Ak Uncgs1gs Region 2 (0 hours0 days 0 hours 0 weeks 0 months )

Burnup, GWd/mtU 5

30 45 Reference 0.9587 0.9552 0.9586 Fuel rod growth and creep 0.9606 0.0019 0.0008 0.9572 0.0020 0.0009 0.9610 0.0025 0.0009 Grid growth 0.9662 0.0075 0.0009 0.9631 0.0079 0.0009 0.9680 0.0094 0.0009 Bias/Stat. combination 0.0094 0.0012 0.Q100 0.0013 0.0119 0.0013 1 All values are calculated kett-The standard deviation (a) of the calculations is about 0.0003.

2 95/95 uncertainty. See Equation 3.3-1. The maximum bias and statistical combination of reactivity effects are balded for each loading region.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN f ER N Al IONAL Table 7 Determination of Depletion Uncertainty, Burnup Uncertainty and MAFP Bias 1: --

5' Spent Fuel1 Depletion Uncertainty, Burnup Uncertainty, GI :::,

a...

(Reference)

Fresh Fuel Reduced Burnup (5%)

E~

i E C....._

-5 *

.. "CJ

-~ i i 3:

kca1c2 kcalc Uncertainty3 kcalc Uncertainty4 w...,

~

Region 2 (0 hours0 days 0 hours 0 weeks 0 months ) 2.0 5

0.9587 0.9682 0.0005 0.9603 0.0024 2.5 15 0.9540 1.0329 0.0040 0.9572 0.0040 3.0 25 0.9464 1.0825 0.0068 0.9520 0.0065 3.5 30 0.9552 1.1213 0.0084 0.9621 0.0077 4.0 35 0.9596 1.1530 0.0097 0.9674 0.0087 4.5 40 0.9595 1.1802 0.Q111 0.9701 0.Q115 5.0 45 0.9586 1.2027 0.Q123 0.9695 0.0118 Region 2 (1 year) 2.0 5

0.9535 0.9682 0.0008 0.9548 0.0022 2.5 15 0.9487 1.0329 0.0043 0.9523 0.0044 3.0 20 0.9642 1.0825 0.0060 0.9692 0.0059 3.5 30 0.9494 1.1213 0.0086 0.9563 0.0077 4.0 35 0.9540 1.1530 0.Q100 0.9627 0.0097 4.5 40 0.9546 1.1802 0.0113 0.9651 0.0114 5.0 45 0.9532 1.2027 0.0125 0.9644 0.0121 Region 2 (5 years) 2.0 5

0.9516 0.9682 0.0009 0.9533 0.0025 2.5 15 0.9438 1.0329 0.0045 0.9477 0.0047 1 Design basis calculations with the upper bound burnup. See Paragraph 3.3.7.2.

2 All values are calculated kett, The standard deviation (a) of the calculations is about 0.0003.

3 See Equation 3.3-2.

4 See Equation 3.3-1.

5 See Equation 3.3-3.

Hl-2220020 Rev. 2 Copyright © 2022 Ho/tee International, all rights reserved MAFP Bias, Major Actinides Only kcalc Bias5 0.9847 0.0004 1.0046 0.0008 1.0116 0.0010 1.0292 0.0011 1.0438 0.0013 1.0535 0.0014 1.0621 0.0016 0.9877 0.0005 1.0045 0.0008 1.0262 0.0009 1.0272 0.0012 1.0401 0.0013 1.0512 0.0015 1.0601 0.0016 0.9857 0.0005 0.9972 0.0008 Page 88 of 118

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N ATIONAL Table 7 Determination of Depletion Uncertainty, Burnup Uncertainty and MAFP Bias 1: 5' 5'

Spent Fuel1 Depletion Uncertainty, Burnup Uncertainty, MAFP Bias, a, u, CL..

(Reference)

Fresh Fuel Reduced Burnup (5%)

Major Actinides Only E:::

i E C..._

ti ~

.. "Cl

-~ i

~ 3:

kcal/

kcalc Uncertainty3 kcalc Uncertainty" kcalc Bias5 I.I.I....

~

3.0 20 0.9582 1.0825 0.0063 0.9634 0.0061 1.0177 0.0009 3.5 30 0.9407 1.1213 0.0091 0.9486 0.0089 1.0153 0.0011 4.0 35 0.9435 1.1530 0.0105 0.9532 0.0105 1.0272 0.0013 4.5 40 0.9431 1.1802 0.0119 0.9543 0.0121 1.0370 0.0014 5.0 45 0.9401 1.2027 0.0132 0.9532 0.0141 1.0439 0.0016 Region 2 (10 years) 2.0 5

0.9495 0.9682 0.0010 0.9514 0.0028 0.9841 0.0005 2.5 10 0.9660 1.0329 0.0034 0.9693 0.0041 1.0126 0.0007 3.0 20 0.9523 1.0825 0.0066 0.9584 0.0070 1.0097 0.0009 3.5 25 0.9605 1.1213 0.0081 0.9675 0.0079 1.0250 0.0010 4.0 35 0.9336 1.1530 0.0110 0.9451 0.0124 1.0156 0.0012 4.5 40 0.9328 1.1802 0.0124 0.9438 0.0119 1.0236 0.0014 5.0 40 0.9586 1.2027 0.0123 0.9699 0.0122 1.0484 0.0014 Region 2 (20 years) 2.0 5

0.9473 0.9682 0.0011 0.9488 0.0024 0.9809 0.0005 2.5 10 0.9622 1.0329 0.0036 0.9659 0.0045 1.0056 0.0007 3.0 20 0.9460 1.0825 0.0069 0.9512 0.0060 0.9997 0.0008 3.5 25 0.9518 1.1213 0.0085 0.9602 0.0092 1.0135 0.0009 4.0 30 0.9534 1.1530 0.0100 0.9632 0.0107 1.0236 0.0011 4.5 35 0.9513 1.1802 0.0115 0.9619 0.0115 1.0299 0.0012 5.0 40 0.9467 1.2027 0.0128 0.9593 0.0136 1.0332 0.0013 Hl-2220020 Rev. 2 Page 89 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN T ER N A T IONAL Table 7-12 -Summary of the Analysis for Region 2 (Spent Fuel)

Enrichment, wt% 235U Reference 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Region 2 (0 hours0 days 0 hours 0 weeks 0 months )

Lower Burnup, GWd/mtU 0

10 20 25 30 35 40 Lower Burnup k,alc 0.9682 0.9784 0.9693 0.9784 0.9821 0.9837 0.9840 Upper Burnup, GWd/mtU 5

15 25 30 35 40 45 Upper Burnup kcalc 0.9587 0.9540 0.9464 0.9552 0.9596 0.9595 0.9586 Uncertainties Depletion Table7-11 0.0005 0.0040 0.0068 0.0084 0.0097 0.0111 0.0123 Burnup Table7-11 0.0024 0.0040 0.0065 0.0077 0.0087 0.0115 0.0118 Fuel tolerances Table 7-2 0.0067 0.0067 0.0067 0.0067 0.0067 0.0067 0.0067 SFR tolerances Table 7-3 0.0034 0.0034 0.0034 0.0034 0.0034 0.0034 0.0034 Geometry change Table 7-10 0.0013 0.0013 0.0013 0.0013 0.0013 0.0013 0.0013 MCNP calculation (2a) 0.0006 0.0006 0.0007 0.0006 0.0007 0.0007 0.0006 MCNP bias (unborated)

Table 3-4 0.0083 0.0083 0.0083 0.0083 0.0083 0.0083 0.0083 MCNP bias (borated)

Table 3-4 0.0092 0.0092 0.0092 0.0092 0.0092 0.0092 0.0092 Statistical combination (unborated) 0.0116 0.0127 0.0147 0.0161 0.0173 0.0196 0.0205 Statistical combination (borated) 0.0122 0.0133 0.0153 0.0166 0.0177 0.0200 0.0208 Biases Geometry change Table 7-10 0.0119 0.0119 0.0119 0.0119 0.0119 0.0119 0.0119 MAFP validation Table 7-11 0.0004 0.0008 0.0010 0.0011 0.0013 0.0014 0.0016 MCNP bias (unborated)

Table 3-4 0.0014 0.0014 0.0014 0.0014 0.0014 0.0014 0.0014 MCNP bias (borated)

Table 3-4 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 TCF (unborated) 0.0253 0.0268 0.0290 0.0305 0.0319 0.0343 0.0354 TCF (borated) 0.0257 0.0271 0.0293 0.0307 0.0320 0.0344 0.0355 Target kett 0.9950 0.9950 0.9950 0.9950 0.9950 0.9950 0.9950 Target k,a1c 0.9697 0.9682 0.9660 0.9645 0.9631 0.9607 0.9596 Interpolated Burnup 0.00 12.09 20.74 28.00 34.22 39.76 44.80 Hl-2220020 Rev. 2 Page 90 of 118 Copyright © 2022 Ho/tee lnternotionol, oll rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INTf:RNATIONAL Table 7-12 -Summary of the Analysis for Region 2 (Spent Fuel)

Enrichment, wt% 235U Reference 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Region 2 (1 year)

Lower Burnup, GWd/mtU 0

10 15 25 30 35 40 Lower Burnup kcalc 0.9682 0.9736 0.9878 0.9728 0.9780 0.9804 0.9779 Upper Burnup, GWd/mtU 5

15 20 30 35 40 45 Upper Burnup kcalc 0.9535 0.9487 0.9642 0.9494 0.9540 0.9546 0.9532 Uncertainties Depletion Table7-11 0.0008 0.0043 0.0060 0.0086 0.Q100 0.0113 0.0125 Burnup Table7-11 0.0022 0.0044 0.0059 0.0077 0.0097 0.0114 0.0121 Fuel tolerances Table 7-2 0.0067 0.0067 0.0067 0.0067 0.0067 0.0067 0.0067 SFR tolerances Table 7-3 0.0034 0.0034 0.0034 0.0034 0.0034 0.0034 0.0034 Geometry change Table 7-10 0.0013 0.0013 0.0013 0.0013 0.0013 0.0013 0.0013 MCNP calculation (2o) 0.0006 0.0006 0.0007 0.0007 0.0007 0.0006 0.0007 MCNP bias (unborated)

Table 3-4 0.0083 0.0083 0.0083 0.0083 0.0083 0.0083 0.0083 MCNP bias (borated)

Table 3-4 0.0092 0.0092 0.0092 0.0092 0.0092 0.0092 0.0092 Statistical combination (unborated) 0.0116 0.0129 0.0141 0.0162 0.0180 0.0196 0.0208 Statistical combination (borated) 0.0122 0.0135 0.0147 0.0167 0.0184 0.0200 0.0211 Biases Geometry change Table 7-10 0.0119 0.0119 0.0119 0.0119 0.Q119 0.0119 0.0119 MAFP validation Table7-11 0.0005 0.0008 0.0009 0.0012 0.0013 0.0015 0.0016 MCNP bias (unborated)

Table 3-4 0.0014 0.0014 0.0014 0.0014 0.0014 0.0014 0.0014 MCNP bias (borated)

Table 3-4 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 TCF (unborated) 0.0254 0.0270 0.0283 0.0307 0.0326 0.0345 0.0357 TCF (borated) 0.0257 0.0273 0.0286 0.0309 0.0327 0.0346 0.0358 Target kett 0.9950 0.9950 0.9950 0.9950 0.9950 0.9950 0.9950 Target kcalc 0.9696 0.9680 0.9667 0.9643 0.9624 0.9605 0.9593 Interpolated Burnup 0.00 11.12 19.48 26.82 33.25 38.86 43.76 Hl-2220020 Rev. 2 Page 91 of 118 Copyright © 2022 Holtec International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N Al IONAL Table 7 Summary of the Analysis for Region 2 (Spent Fuel)

Enrichment, wt% 235U Reference 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Region 2 (5 years)

Lower Burnup, GWd/mtU 0

10 15 25 30 35 40 Lower Burnup kcalc 0.9682 0.9699 0.9835 0.9666 0.9710 0.9706 0.9679 Upper Burnup, GWd/mtU 5

15 20 30 35 40 45 Upper Burnup kcalc 0.9516 0.9438 0.9582 0.9407 0.9435 0.9431 0.9401 Uncertainties Depletion Table7-11 0.0009 0.0045 0.0063 0.0091 0.0105 0.0119 0.0132 Burn up Table7-11 0.0025 0.0047 0.0061 0.0089 0.0105 0.0121 0.0141 Fuel tolerances Table 7-2 0.0067 0.0067 0.0067 0.0067 0.0067 0.0067 0.0067 SFR tolerances Table 7-3 0.0034 0.0034 0.0034 0.0034 0.0034 0.0034 0.0034 Geometry change Table7-10 0.0013 0.0013 0.0013 0.0013 0.0013 0.0013 0.0013 MCNP calculation (2o) 0.0006 0.0006 0.0007 0.0007 0.0007 0.0006 0.0007 MCNP bias (unborated)

Table 3-4 0.0083 0.0083 0.0083 0.0083 0.0083 0.0083 0.0083 MCNP bias (borated)

Table 3-4 0.0092 0.0092 0.0092 0.0092 0.0092 0.0092 0.0092 Statistical combination (unborated) 0.0116 0.0131 0.0143 0.0170 0.0187 0.0204 0.0224 Statistical combination (borated) 0.0123 0.0137 0.0149 0.0175 0.0191 0.0208 0.0227 Biases Geometry change Table 7-10 0.0119 0.0119 0.0119 0.0119 0.0119 0.0119 0.0119 MAFP validation Table7-11 0.0005 0.0008 0.0009 0.0011 0.0013 0.0014 0.0016 MCNP bias (unborated)

Table 3-4 0.0014 0.0014 0.0014 0.0014 0.0014 0.0014 0.0014 MCNP bias (borated)

Table 3-4 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 TCF (unborated) 0.0255 0.0272 0.0285 0.0315 0.0333 0.0351 0.0373 TCF (borated) 0.0258 0.0275 0.0288 0.0316 0.0334 0.0352 0.0374 Target kett 0.9950 0.9950 0.9950 0.9950 0.9950 0.9950 0.9950 Target kcalc 0.9695 0.9678 0.9665 0.9635 0.9617 0.9599 0.9577 Interpolated Burnup 0.00 10.40 18.36 25.58 31.70 36.94 41.83 Hl-2220020 Rev. 2 Page 92 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N Al IONAL Table 7 Summary of the Analysis for Region 2 (Spent Fuel)

Enrichment, wt% 235U Reference 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Region 2 (10 years)

Lower Burnup, GWd/mtU 0

5 15 20 30 35 35 Lower Burnup kcalc 0.9682 0.9998 0.9800 0.9871 0.9629 0.9623 0.9870 Upper Burnup, GWd/mtU 5

10 20 25 35 40 40 Upper Burnup kcalc 0.9495 0.9660 0.9523 0.9605 0.9336 0.9328 0.9586 Uncertainties Depletion Table7-11 0.0010 0.0034 0.0066 0.0081 0.0110 0.0124 0,0123 Burnup Table7-11 0.0028 0.0041 0.0070 0.0079 0,0124 0.0119 0.0122 Fuel tolerances Table 7-2 0.0067 0.0067 0.0067 0.0067 0.0067 0.0067 0.0067 SFR tolerances Table 7-3 0.0034 0.0034 0.0034 0.0034 0.0034 0.0034 0.0034 Geometry change Table 7-10 0.0013 0.0013 0.0013 0.0013 0.0013 0.0013 0.0013 MCNP calculation (2a) 0.0006 0.0006 0.0006 0.0007 0.0006 0.0007 0.0007 MCNP bias (unborated)

Table 3-4 0.0083 0.0083 0.0083 0.0083 0.0083 0.0083 0.0083 MCNP bias (borated)

Table 3-4 0.0092 0.0092 0.0092 0.0092 0.0092 0.0092 0.0092 Statistical combination (unborated) 0.0117 0,0125 0.0149 0,0160 0.0201 0.0206 0.0207 Statistical combination (borated) 0,0124 0.0131 0.0154 0.0165 0.0205 0.0210 0.0211 Biases Geometry change Table 7-10 0.0119 0.0119 0.0119 0.0119 0.0119 0.0119 0,0119 MAFP validation Table7-11 0.0005 0.0007 0.0009 0.0010 0.0012 0.0014 0.0014 MCNP bias (unborated)

Table 3-4 0.0014 0.0014 0.0014 0.0014 0.0014 0.0014 0.0014 MCNP bias (borated)

Table 3-4 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 TCF (unborated) 0.0255 0.0265 0.0291 0.0303 0.0346 0.0353 0.0354 TCF (borated) 0.0259 0.0269 0.0293 0.0305 0.0347 0.0354 0.0355 Target kett 0.9950 0.9950 0.9950 0.9950 0.9950 0.9950 0.9950 Target kcalc 0.9695 0.9685 0.9659 0.9647 0.9604 0.9597 0.9596 Interpolated Burnup 0.00 9.64 17.54 24.22 30.43 35.44 39.82 Hl-2220020 Rev. 2 Page 93 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N Al IONAL Table 7-12 -Summary of the Analysis for Region 2 (Spent Fuel)

Enrichment, wt% 235U Reference 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Region 2 (20 years)

Lower Burnup, GWd/mtU 0

5 15 20 25 30 35 Lower Burnup k,a1c 0.9682 0.9982 0.9749 0.9819 0.9835 0.9821 0.9772 Upper Burnup, GWd/mtU 5

10 20 25 30 35 40 Upper Burnup kcalc 0.9473 0.9622 0.9460 0.9518 0.9534 0.9513 0.9467 Uncertainties Depletion Table7-11 0.0011 0.0036 0.0069 0.0085 0.0100 0.0115 0.0128 Burnup Table7-11 0.0024 0.0045 0.0060 0.0092 0.0107 0.0115 0.0136 Fuel tolerances Table 7-2 0.0067 0.0067 0.0067 0.0067 0.0067 0.0067 0.0067 SFR tolerances Table 7-3 0.0034 0.0034 0.0034 0.0034 0.0034 0.0034 0.0034 Geometry change Table 7-10 0.0013 0.0013 0.0013 0.0013 0.0013 0.0013 0.0013 MCNP calculation (2o) 0.0006 0.0006 0.0007 0.0007 0.0007 0.0007 0.0007 MCNP bias (unborated)

Table 3-4 0.0083 0.0083 0.0083 0.0083 0.0083 0.0083 0.0083 MCNP bias (borated)

Table 3-4 0.0092 0.0092 0.0092 0.0092 0.0092 0.0092 0.0092 Statistical combination (unborated) 0.Q116 0.0127 0.0146 0.0169 0.0185 0.0198 0.0218 Statistical combination (borated) 0.0123 0.0133 0.0151 0.0173 0.0189 0.0202 0.0222 Biases Geometry change Table 7-10 0.0119 0.0119 0.0119 0.0119 0.0119 0.0119 0.0119 MAFP validation Table7-11 0.0005 0.0007 0.0008 0.0009 0.0011 0.0012 0.0013 MCNP bias (unborated)

Table 3-4 0.0014 0.0014 0.0014 0.0014 0.0014 0.0014 0.0014 MCNP bias (borated)

Table 3-4 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 TCF (unborated) 0.0254 0.0267 0.0287 0.0311 0.0329 0.0343 0.0365 TCF (borated) 0.0258 0.0270 0.0289 0.0313 0.0331 0.0344 0.0365 Target kett 0.9950 0.9950 0.9950 0.9950 0.9950 0.9950 0.9950 Target k,a1c 0.9696 0.9683 0.9663 0.9639 0.9621 0.9607 0.9585 Interpolated Burnup 0.00 9.16 16.49 22.99 28.56 33.48 38.06 Hl-2220020 Rev. 2 Page 94 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N A flO N A L Table 7 Summary of the Loading Curves for Callaway SFP Loading Cooling Minimum Burnup (GWd/mtU)

Configuration

Time, as a Function of the Initial Enrichment (wt% 235U)1 (Figure 1-1) years 0

f(x) = +8.0828e-01

x3 -1.1006e+01

x2 +6.0436e+01

x -8.3186e+01 1

f(x) = +S.0216e-01

x3 -7.4933e+00

x2 +4.7443e+01

x -6.8811 e+01 Region 2 5

f(x) = +4.3360e-01

x3 -6.6172e+00

x2 +4.3336e+01

x -6.3595e+01 10 f(x) = +2.5252e-01

x3 -4.6354e+00

x2 +3.5866e+01

x -5.5148e+01 20 f(x) = +3.7094e-01

x3 -5.6482e+00

x2 +3.7748e+01

x -5.5829e+01 1 Linear interpolation of calculated burnups between cooling times for a given fuel assembly enrichment is permitted.

Loading Region (Figure 1-1)

Region 2 Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N A 'l lONAL Table 7 Loading Curves Confirmatory Calculations C :)

)

Cooling GI "'

a...

E~

, E Axial Maximum

Time,

-5 '#.

C...._

kcalc 1 TCF2 Burnup keff i 3:

years 2 3:

w......

2.0 0.13 Profiled 0.9675 0.0253 0.9928 0

3.5 28.17 Profiled 0.9635 0.0305 0.9939 5.0 44.88 Profiled 0.9593 0.0354 0.9946 2.0 0.12 Profiled 0.9656 0.0254 0.9909 1

3.5 26.98 Profiled 0.9639 0.0307 0.9946 5.0 43.84 Profiled 0.9582 0.0357 0.9939 2.0 0.00 Profiled 0.9682 0.0255 0.9937 5

3.5 25.61 Profiled 0.9636 0.0315 0.9951 5.0 41.85 Profiled 0.9579 0.0373 0.9952 2.0 0.00 Profiled 0.9682 0.0255 0.9938 10 3.5 24.43 Profiled 0.9632 0.0303 0.9935 5.0 39.86 Profiled 0.9594 0.0354 0.9948 2.0 0.00 Profiled 0.9682 0.0254 0.9937 20 3.5 23.00 Profiled 0.9636 0.0311 0.9947 5.0 38.07 Profiled 0.9585 0.0365 0.9950 Maximum keff 0.9952 1 All values are calculated kett-The standard deviation (a) of the calculations is about 0.0003.

2 Total Correction Factor determined in Table 7-12 is applied.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TER N Al IONAL Table 7 Summary of the Analysis for Region 1 (Fresh Fuel}

Loading Configuration Reference Region 1 (Figure 1-1)

Enrichment, wt% 235U 5.0 Burnup, GWd/mtU 0

kcalc 0.8446 Uncertainties Fuel tolerances Table 7-2 0.0064 SFR tolerances Table 7-3 0.0068 MCNP calculation (2cr) 0.0008 MCNP bias (unborated)

Table 3-4 0.0054 MCNP bias (borated)

Table 3-4 0.0078 Statistical combination (unborated) 0.0108 Statistical combination (borated) 0.0122 Biases MCNP bias (unborated)

Table 3-4 0.0000 MCNP bias (borated)

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N ATIONAL Table 7 Summary of the Analysis for Normal Conditions with Soluble Boron Credit C::::,

Cooling QI "'

a.....

Loading Region E:::

, E Axial Maximum

Time,

-5 '#.

C kcalc 1 TCF2

{Figure 1-1)

.. 'ti Burnup keff

~~

years

~ J C,

LI.I --

2.0 0.13 Uniform 0.8832 0.0257 0.9089 0

3.5 28.17 Profiled 0.9092 0.0307 0.9399 5.0 44.88 Profiled 0.9117 0.0355 0.9472 2.0 0.12 Uniform 0.8811 0.0257 0.9068 1

3.5 26.98 Profiled 0.9087 0.0309 0.9396 5.0 43.84 Profiled 0.9122 0.0358 0.9479 2.0 0.00 Profiled 0.8834 0.0258 0.9092 Region 2 5

3.5 25.61 Profiled 0.9080 0.0316 0.9396 5.0 41.85 Profiled 0.9106 0.0374 0.9480 2.0 0.00 Profiled 0.8834 0.0259 0.9093 10 3.5 24.43 Profiled 0.9077 0.0305 0.9383 5.0 39.86 Profiled 0.9124 0.0355 0.9479 2.0 0.00 Profiled 0.8834 0.0258 0.9092 20 3.5 23.00 Profiled 0.9085 0.0313 0.9397 5.0 38.07 Profiled 0.9122 0.0365 0.9487 Maximum keff 0.9487 1 All values are calculated ketf. The standard deviation (cr) of the calculations is about 0.0003.

2 Total Correction Factor determined in Table 7-12 is applied.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N ATIONAL Table 7-17-Summary of the Analysis for the SFR Interfaces Left Right Spent Fuel Axial Fuel Left Right Maximum Case Enrich.

Assembly kcalc 1 SFR SFR (wt% 235U)

Burnup Positioning SFR TCF2 SFR TCF2 kett Region 1 to Region 2 (0 hours0 days 0 hours 0 weeks 0 months ) Interfaces 2.0 Profiled Centered 0.9604 0.0253 0.0108 0.9857 3.4.3.1 2

1 3.5 Profiled Centered 0.9565 0.0305 0.Q108 0.9870 5.0 Profiled Centered 0.9529 0.0354 0.0108 0.9883 2.0 Profiled Centered 0.9668 0.0253 0.0108 0.9921 3.4.3.2 2

1 3.5 Profiled Centered 0.9632 0.0305 0.0108 0.9937 (2x2) 5.0 Profiled Centered 0.9583 0.0354 0.0108 0.9937 2.0 Uniform Eccentric 0.9099 0.0253 0.0108 0.9352 3.4.3.3 2

1 3.5 Uniform Eccentric 0.9021 0.0305 0.0108 0.9325 (2x2) 5.0 Uniform Eccentric 0.9029 0.0354 0.0108 0.9382 Region 1 to Region 2 (20 years) Interfaces 2.0 n/a Centered 0.9574 0.0254 0.Q108 0.9828 3.4.3.1 2

1 3.5 Profiled Centered 0.9556 0.0311 0.0108 0.9868 5.0 Profiled Centered 0.9514 0.0365 0.Q108 0.9879 2.0 n/a Centered 0.9638 0.0254 0.0108 0.9892 3.4.3.2 2

1 3.5 Profiled Centered 0.9635 0.0311 0.Q108 0.9946 (2x2) 5.0 Profiled Centered 0.9574 0.0365 0.0108 0.9938 2.0 n/a Eccentric 0.9090 0.0254 0.Q108 0.9344 3.4.3.3 2

1 3.5 Profiled Eccentric 0.9005 0.0311 0.0108 0.9316 (2x2) 5.0 Profiled Eccentric 0.8963 0.0365 0.0108 0.9328 1 All values are calculated ke11. The standard deviation (o) of the calculations is up to 0.0004.

2 The higher of the applicable Total Correction Factors determined in Table 7-12 or Table 7-15 is applied.

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7-18 -Summary of the Analysis for the FRSR Description Calculated keff1 Ak 2x2, cell centered (Reference) 0.6847 2x2, eccentric in 0.6832

-0.0016 2x2, eccentric corner 0.6580

-0.0267 8x8, eccentric in 0.6824

-0.0024 1 The standard deviation (o) of the calculations is about 0.0003.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N A I IONAL Table 7-19-Summary of the Analysis for Fuel Assemblies with Missing Rods Fuel Assembly Assumed Burnup Calculated Enrichment Enrichment Assembly (wt% 235U)

(wt% 235U)

(GWd/mtU) kett 1 Region 2 (0 hours0 days 0 hours 0 weeks 0 months ) 804 2.61 3.0 33.625 0.9061 8(65 2.61 3.0 33.662 0.9067 (04 3.1 3.5 32.470 0.9502 (12 3.1 3.5 31.096 0.9447 F34 3.61 4.0 34.543 0.9617 G75 4.38 4.5 49.142 0.9229 Region 1 R87 4.4 4.5 03 0.8450 1 The standard deviation (o) of the calculations is up to 0.0004.

2 Total Correction Factor determined in Table 7-12 or Table 7-15 is applied.

3 Fresh fuel is considered, while the assembly burnup is 23.902 GWd/mtU.

Hl-2220020 Rev. 2 Copyright © 2022 Ho/tee International, all rights reserved Maximum TCF2 kett 0.0290 0.9351 0.0290 0.9357 0.0305 0.9807 0.0305 0.9752 0.0319 0.9936 0.0343 0.9572 0.0108 0.8558 Page 101 of 118

Hl-2220020 Rev. 2 Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7-20-Deleted Copyright © 2022 Holtec International, all rights reserved HOL TEC IN TER N A I IONAL Page102of118

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N A l lONAI Table 7 Maximum kett Calculation for the Fuel Misload Accident Spent Fuel Fuel Soluble Boron Maximum Enrichment Assembly Concentration, kca1c1 TCF2 kett (wt% 235U)

Positioning ppm Region 1 500 0.9516 0.9645 5.0 Eccentric 0.0129 1000 0.8975 0.9105 Region 2 (0 hours0 days 0 hours 0 weeks 0 months ) 500 0.9171 0.9428 2.0 Eccentric 0.0257 1000 0.8576 0.8832 500 0.9306 0.9613 3.5 Eccentric 0.0307 1000 0.8817 0.9123 500 0.9343 0.9697 5.0 Eccentric 0.0355 1000 0.8871 0.9226 Region 2 (20 years) 500 0.9182 0.9440 2.0 Eccentric 0.0258 1000 0.8557 0.8815 500 0.9297 0.9609 3.5 Eccentric 0.0313 1000 0.8782 0.9095 500 0.9303 0.9668 5.0 Eccentric 0.0365 1000 0.8859 0.9225 1 All values are calculated kett, The standard deviation (o) of the calculations is up to 0.0004.

2 Total Correction Factor determined in Table 7-12 or Table 7-15 is applied.

< 500 615.4 709.2

< 500 606.1 689.7 Page 103 of 118

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN T ER N A I I O N A L Table 7 Maximum keff Calculation for the Fuel Misload Accident Spent Fuel Fuel Soluble Boron Interpolated Maximum Soluble Boron Enrichment Assembly Concentration, kca1c1 TCF2 kett Requirement, (wt% 235U)

Positioning ppm ppm Region 1 to Region 2 Interface (0 hours0 days 0 hours 0 weeks 0 months ) 500 0.9596 0.0129 I 0.9853 2.0 Eccentric 0.0257 815.8 1000 0.9037 0.9294 500 0.9623 0.0129 I 0.9930 3.5 Eccentric 0.0307 906.5 1000 0.9095 0.9401 500 0.9630 0.D129/

0.9984 5.0 Eccentric 0.0355 976.4 1000 0.9122 0.9476 Region 1 to Region 2 Interface (20 years) 500 0.9550 0.0129 I 0.9808 2.0 Eccentric 0.0258 777.0 1000 0.8994 0.9252 500 0.9608 0.D129/

0.9921 3.5 Eccentric 0.0313 903.3 1000 0.9087 0.9399 500 0.9601 0.0129 I 0.9966 5.0 Eccentric 0.0365 950.7 1000 0.9084 0.9449 Interface of 2x2 Region 1 within Region 2 (0 hours0 days 0 hours 0 weeks 0 months ) 500 0.9627 0.0129 I 0.9884 2.0 Eccentric 0.0257 834.5 1000 0.9053 0.9310 500 0.9667 0.0129 I 0.9974 3.5 Eccentric 0.0307 955.8 1000 0.9147 0.9454 1000 0.9173 0.D129/

0.9528 5.0 Eccentric 0.0355 1031.2 1500 0.8724 0.9079 Interface of 2x2 Region 1 within Region 2 (20 years) 500 0.9590 0.0129 I 0.9848 2.0 Eccentric 0.0258 795.5 1000 0.9001 0.9259 500 0.9634 0.0129 I 0.9947 3.5 Eccentric 0.0313 936.6 1000 0.9122 0.9435 500 0.9653 0.0129 I 1.0019 5.0 Eccentric 0.0365 997.2 1000 0.9132 0.9497 Hl-2220020 Rev. 2 Page 104 of 118 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT E RNAflONA L Table 7 Maximum kett Calculation for the Fuel Misload Accident Spent Fuel Fuel Soluble Boron Interpolated Maximum Soluble Boron Enrichment Assembly Concentration, kca1c 1 TCF2 keff Requirement, (wt% 235U)

Positioning ppm ppm Interface of 2x2 Region 2 (0 hours0 days 0 hours 0 weeks 0 months ) within Region 1 500 0.9627 0.0257 I 0.9883 2.0 Centered 0.0129 850.1 1000 0.9079 0.9336 500 0.9628 0.0307 I 0.9935 3.5 Centered 0.0129 908.1 1000 0.9096 0.9402 1000 0.9639 0.0355 I 0.9993 5.0 Centered 0.0129 971.4 1500 0.9115 0.9470 Interface of 2x2 Region 2 (20 years) within Region 1 500 0.9611 0.0258 I 0.9870 2.0 Centered 0.0129 839.5 1000 0.9067 0.9325 500 0.9618 0.0313 I 0.9931 3.5 Centered 0.0129 909.7 1000 0.9092 0.9405 500 0.9619 0.0365 I 0.9985 5.0 Centered 0.0129 953.3 1000 0.9085 0.9450 Maximum:

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TERNA"IIONAI.

Table 7-22 -Maximum ke<< Calculation for the Incorrect Loading Curve Accident Loading Soluble Boron Configuration Applied Concentration, kcalc1 TCF2 Maximum Loading Curve keff (Figure 1-1) ppm Region 2 Region 2 500 0.9439 0.9794 0.0355 (0 hours0 days 0 hours 0 weeks 0 months )

(20 years) 1000 0.9022 0.9377 Maximum:

1 All values are calculated kett-The standard deviation (cr) of the calculations is about 0.0003.

2 Total Correction Factor determined in Table 7-12 is applied.

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7 SFP Boron Dilution Accident Analysis Parameters Value Technical Specification Soluble Boron Concentration 2165 Soluble Boron Concentration to Maintain kett of 0.95 550 Technical Specification Minimum Volume Water in SFP 401295 Minimum Volume Water in SFP (credited) 242932 Volume Needed to High-Level Alarm Setpoint 25095 Volume Needed to SFP Overflow 35753 High Flow Rate Accident Evaluation Volume Needed to Dilute to Minimum Concentration 332879 Maximum Operator Response Time 35 Flow Rate Required to Challenge Response Time after 8489 the SFP Overflow Low Flow Rate Accident Evaluation Volume Needed to Dilute to Minimum Concentration 332879 SFP Boron Concentration Surveillance Interval 2101 Flow Rate Required to Challenge Surveillance Interval 26 1 Conservatively increased by 25%.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT E RNATIO NAL Table 7 Reactivity Effect of the BORAL' Panel 108 Areal Density Loading 10B Areal Density, Configuration g/cm2 kcalc 1 dk (Figure 1-1) 0.0300 0.8446 Ref.

0.0285 0.8456 0.0010 Region 1 0.0270 0.8467 0.0021 0.0240 0.8487 0.0041 f(x) = -9.7250e+00

x2 -1.4167e+00

x +2.9979e-02 0.0300 0.9593 Ref.

0.0285 0.9617 0.0025 Region 2 0.0270 0.9629 0.0036 0.0240 0.9682 0.0090 f(x) = +1.6607e+01

x2 -8.2789e-01

x +3.0084e-02

x 1 All values are calculated kett-The standard deviation (u) of the calculations is up to 0.0004.

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7 Margin Evaluation Loading Configuration Description (Figure 1-1)

Reference Region 1 Total Margin Reference Region 2 Total Margin kcalc 1 0.8446 0.9593 1 All values are calculated kett-The standard deviation (cr) of the calculations is up to 0.0004.

-0.0193 Ref. -

4a, 4b

-0.0228 Page 109 of 118

Loading Configuration

{Figure 1-1)

Region 1 Region 2 (0 hours0 days 0 hours 0 weeks 0 months )

Criticality Safety Analysis of SFP for Callaway Proprietary Information Table 7 Reactivity Effect of the 84C Particle Size Description kcalc 1 Ak 5.0 wt% mu, 0 GWd/mtU Homogeneous (Reference) 0.8446 84( particle size of 45 µm 0.8453 0.0007 84( particle size of 180 µm 0.8448 0.0003 2.0 wt% mu, 5 GWd/mtU Homogeneous (Reference) 0.9587 84( particle size of 45 µm 0.9594 0.0007 84( particle size of 180 µm 0.9593 0.0006 3.5 wt% mu, 30 GWd/mtU Homogeneous (Reference) 0.9552 84( particle size of 45 µm 0.9554 0.0001 84( particle size of 180 µm 0.9548

-0.0004 5.0 wt% mu, 45 GWd/mtU Homogeneous (Reference) 0.9586 84( particle size of 45 µm 0.9593 0.0007 84( particle size of 180 µm 0.9594 0.0009 1 All values are calculated kett. The standard deviation (o) of the calculations is up to 0.0004.

2 95/95 uncertainty.

50000 40000

i I 30000

s

E

a.

E co 20000 10000 I

I

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TER N Al IONAL Callaway SFP Fuel Inventory vs. Region 2 Loading Curves I

I I

I 0

Callaway Fuel Assemblies O years (97.84%)

1 years (98.31%)

5 years (98.87%)

10 years (99.15%)

~

20 years (99.15%)

o-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

2.0 2.5 3.0 3.5 4.0 4.5 5.0 Enrichment. wt% 235u Figure 7 Loading Curves for Uniform Loading of Spent Fuel Assemblies {Region 2)

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N A 'f IONAL 4a, 4b Figure 7-2 -Total Reaction Rate Distribution for Region 1 to Region 2 Interface 4a, 4b Figure 7-3-Total Reaction Rate Distribution for Region 1 (2x2) to Region 2 Interface Hl-2220020 Rev. 2 Page 112 of 118 Copyright © 2022 Ho/tee International, all rights reserved

0.030 0.029 0.028 N

E u

0, i-

'iii C

OJ 0.027 0

iii OJ,_

<(

co 0.026 0.025 0.024 0.000 Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N ATIONAL Reactivity Effect of BORAL' Panel Areal Density 0.002 0.004 b.k Region 1, Lattice u

..,.... Region 1, Lattice u, f(x)

Region 2. Lattice u

Criticality Safety Analysis of SFP for Callaway Proprietary Information

8.0 CONCLUSION

HOLTEC IN TER N ATIONAL The criticality safety analyses have been performed for the Callaway SFP that contains a single type of BORAL' 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 GAi and Westinghouse V+, respectively, with fuel enrichment up to 5.0 wt% 235U. 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 (kett) 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 7-13 as well as in Figure 7-1. The results of the calculations show that the effective neutron multiplication factor (kett) 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 ppm 1), 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 1 is required to ensure that the effective neutron multiplication factor (kett) 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 108 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 50 ppm in accordance with Paragraph 5.1.1 of [3].

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N Al IONAL The key criticality analysis parameters for Callaway, 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-4.0, to assure placement of assemblies in the racks is in accordance with the analyses presented here.

Criticality Safety Analysis of SFP for Callaway Proprietary Information

9.0 REFERENCES

HOL TEC INT ER N Al IONAL

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

[2] "Staff Guidance Regarding the Nuclear Criticality Safety Analysis for Spent Fuel Pools," US NRC, DSS-ISG-2010-01, 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] "CASMO5 A Fuel Assembly Burnup Program, User's Manual," Studsvik Scandpower, Inc.,

SSP-07 /431, Revision 10.

[7] "ENDF/B-VII.0 586 Group Neutron Data Library for CASMO-5 and CASMO-5M," 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-03-1987 (2003, Revised 2/1/2008).

[9] "ENDF/B-Vll.0 Evaluated Nuclear Data Library," December 15, 2006.

[1 OJ Holtec International Report Hl-2156450, Revision 2 (proprietary).

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

[12] "Guide for Validation of Nuclear Criticality Safety Calculational Methodology," USN RC, NUREG/CR-6698, January 2001.

[13] "Nuclear Group Computer Code Benchmark Calculations," Holtec International, Hl-2104790, Revision 3 (proprietary).

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N ATIONAL

[14] "BORAL Documentation Package," DOC-70384-3, Project 70384, Holtec International, June 1999 (proprietary).

[15] "Safety Analysis Report HI-STAR 100 Cask System," Holtec International, USNRC Docket 71-9261, Hl-951251, Revision 20 (proprietary).

[16] "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.

[17] M. D. DeHart, "Sensitivity and Parametric Evaulations of Significant Aspects of Burnup Credit for PWR Spent Fuel Packages," Oak Ridge National Laboratory, ORNL/TM-12973, May 1996.

[18] "Parametric Study of the 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 Inputs for Callaway Spent Fuel Pool Criticality Analysis," NED20220010, Ameren Missouri, February 8, 2022.

[20] "Westinghouse Inputs for Callaway Spent Fuel Pool Criticality Analysis," NED20220012, Ameren Missouri, February 22, 2022.

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

[22] "Parametric Study of the 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-1937, 1997.

[25] "Summary Report of Commercial Reactor Criticality Data for McGuire Unit 1," B00000000-01717-5705-00063, 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-2011/514, NUREG/CR-7109, USNRC Office of Nuclear Regulatory Research, April 2012.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N A flONAL

[28] Bias Estimates Used in Lieu of Validation of Fission Products and Minor Actinides in MCNP Keff Calculations for PWR Burnup Credit Casks, ORNL/TM-2012/544, NUREG/CR-7205, USNRC Office of Nuclear Regulatory Research, September 2015.

[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/TM-2002/255, NUREG/CR-6835, USN RC Office of Nuclear Material Safety and Safeguards, September 2003.

[31] "Overview of BORAL Performance Based Upon Surveillance Coupon Measurements," EPRI Report 1021052, Palo Alto, CA, December 2010.

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

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

[34] "Ameren Spent Fuel Pool Levels for Dilution Event Analysis," NED20220013, 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 Proprietary Information HO L T EC INT ER N A1 IONAL APPENDIX A NEI 12-16 CRITICALITY ANAL VSIS 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.

Subject Included Notes / Explanation 1.0 Introduction and Overview Purpose of submittal YES/NO Chapter 1.0 Chanqes requested YES/NO Chapter 1.0 Summary of physical chanqes YES/NO Chapters 1.0 and 8.0, Appendix B Summary of Tech Spec chanqes YES/NO Chapters 1.0 and 8.0, Aooendix B Summary of analytical scope YES/NO Chapter 1.0, Section 3.3 2.0 Acceptance Criteria and Regulatory Guidance Summary of requirements and guidance YES/NO Chapter 2.0 Requirements 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, Paraqraph 3.3.6.1 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 guide tube patterns YES/NO Material compositions YES/NO Describe all fuel inserts YES/NO Section 5.3, Paraqraph 3.3.6.3 Geometric dimensions (nominal and YES/NO tolerances)

Schematic (axial/cross-section)

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TER N ATIONAL Subject Included Notes / Explanation Describe non-standard fuel YES/NO Sections 5.7 and 5.8, 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 Spent fuel pool, storage rack description YES/NO Section 5.4, Subsection 3.3.3 Nominal and tolerance dimensions YES/NO Section 5.4, Subsection 3.3.3 Schematic (axial/cross-section)

YES/NO Fiqure 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 Bounding assembly design(s)

Integral absorber credit Accident analysis Spent fuel storage rack analysis description YES/NO Storaqe qeometries YES/NO Chapter 1.0, Section 3.3 Boundinq assembly desiqn(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 Empty storage cells, Chapter 1.0 Fixed *neutron absorbers YES/NO Chapter 1.0, Section 3.3, Subsection 3.3.3 Aqinq manaqement proqram YES/NO Subsection 3.7.1 Accident analysis YES/NO Section 3.6 Temperature increase YES/NO Subsection 3.6.1 Assembly drop YES/NO Subsections 3.6.2 and 3.6.3 Hl-2220020 Rev. 2 Page A-2 of 7 Copyright © 2022 Ho/tee lnternotionot, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC IN TER N A l IONAL Subject Included Notes / Explanation Sinqle assembly misload YES/NO Subsection 3.6.5 Multiple misload 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 Handlinq 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 kett 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 Convergence 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 Description of nuclides used YES/NO Subsection 3.3.6 Convergence checks YES/NO Not applicable Validation of code and library YES/NO Paragraph 3.2.2.1, Subparaqraph 3.3.6.6.1 Major actinides and structural materials YES/NO Paragraph 3.2.2.1 Minor actinides and fission products YES/NO Subparagraph 3.3.6.6.3 Absorbers credited YES/NO Paragraph 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 Limiting fuel design Fuel density Burnable poisons Fuel dimensions Axial blankets

Limiting rack model Storage vault dimensions and materials Temperature Multiple regions/configurations Flooded Low density moderator Hl-2220020 Rev. 2 Page A-3 of 7 Copyright © 2022 Holtec International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INT ER N Al IONAL Subject Included Notes / Explanation Eccentric fuel placement Tolerances Fuel geometry Fuel pin pitch Fuel pellet OD Fuel clad OD Fuel content Enrichment Density Integral absorber Rack geometry Rack pitch Cell wall thickness Storaqe 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 Converqence verification YES/NO Not applicable Simplifications YES/NO Subsection 3.3.6, Chapter 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 lnteqral absorbers YES/NO Section 5.3, Subparaqraph 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 operatinq history YES/NO Subparaqraph 3.3.6.3.2 9.0 Criticality Safety Analysis of Spent Fuel Pool Storaqe Racks Rack model YES/NO Section 3.3 Hl-2220020 Rev. 2 Page A-4 of 7 Copyright © 2022 Ho/tee International, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOL TEC INl ER NATI ONAL Subject Included Notes / Explanation Boundary conditions YES/NO Section 3.3 Source distribution YES/NO Subsection 3.2.2 Geometry restrictions YES/NO Not applicable Design basis fuel description 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 Confiqurations 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 Un borated YES/NO Chapter 1.0, Paragraph 3.3.7.2, Subsections 7.7.1 and 7.7.2 Multiple rack desiqns YES/NO Section 5.4 Alternate storaqe qeometry YES/NO Not aoolicable Reactivity control devices YES/NO Not aoolicable Fuel assembly inserts Storage cell inserts Storage cell blocking devices Axial burnup shapes YES/NO Paragraph 3.3.6.4 Uniform/distributed YES/NO Paragraph 3.3.6.4, Subsections 7.6.4, 7.7.2 and 7.7.3 Nodalization YES/NO Paragraph 3.3.6.4 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 Fuel qeometrv YES/NO Subsection 3.3.2, Figure 3-3 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 Subsection 3.3.2, Section 7.2 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 Density YES/NO Subsection 3.3.2, Section 7.2 Assembly insert dimensions and YES/NO Subparagraph 3.3.6.3.4 materials Rack geometry YES/NO Subsection 3.3.3, Figure 3-3, Section 7.3 Hl-2220020 Rev. 2 Page A-5 of 7 Copyright © 2022 Ho/tee lnternotional, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N Al IONAL Subject Included Notes / Explanation 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 aoolicable Code validation uncertainty YES/NO Paraqraph 3.2.2.1, Fiqure 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 Paragraph 3.2.2.1, Fiqure 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, Chapter 4.0 10.0 Interface Analysis Interface configurations 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 11.0 Normal Conditions Fuel handling equipment YES/NO Bounded by normal storage conditions.

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TER N A l IONAL 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 12.0 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 DroDDed 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 13.0 Analysis Results and Conclusions Summary of results YES/NO Chapter 8.0 Burnup curve(s)

YES/NO Table 7-13, Fiqure 7-1 Intermediate decay time treatment YES/NO New administrative controls YES/NO Table 7-12, Chapter 8.0, Appendix B, Subsections 3.5.4 and 3.5.5 Technical Specification markups YES/NO 14.0 References YES/NO Chapter 9.0 ADDendix A: Computer Code Validation:

Code validation methodoloav and biases YES/NO Paraqraph 3.2.2.1 New fuel YES/NO Paraqraph 3.2.2.1, Table 3-2 Depleted fuel YES/NO Paraqraph 3.2.2.1, Table 3-2 MOX YES/NO Paragraph 3.2.2.1, Table 3-2 HTC YES/NO Paragraph 3.2.2.1, Table 3-2 Converqence YES/NO Trends YES/NO Paraqraph 3.2.2.1, Table 3-3 Bias and uncertainty YES/NO Paraqraph 3.2.2.1, Table 3-4 Ranqe of applicability YES/NO Paraqraph 3.2.2.1, Table 3-1 Analysis of area of applicability coverage YES/NO Paragraph 3.2.2.1, Table 3-1 Hl-2220020 Rev. 2 Page A-7 of 7 Copyright © 2022 Ho/tee International, all rights reserved

APPENDIX B Criticality Safety Analysis of SFP for Callaway Proprietary Information

SUMMARY

OF KEY PARAMETERS Table of Contents HOLTEC INT ER N A I IONAL B-

1.0 INTRODUCTION

...................................................................................................................................... B-2 B-2.0 STANDARD KEY PARAMETERS................................................................................................................ B-2 B-3.0 KEY PARAMETERS FOR THE BURNUP CREDIT......................................................................................... B-3 B-4.0 PROPOSED RULES FOR PERMISSIBLE LOADING...................................................................................... B-4 Hl-2220020 Rev. 2 Page B-1 of 4 Copyright © 2022 Ho/tee International, all rights reserved

B-1.0 Criticality Safety Analysis of SFP for Callaway Proprietary Information INTRODUCTION HOLTEC INT ER N A l IONAL 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: BORAL' 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 17x17 fuel assembly. The key parameters for the criticality safety analysis in the main body of the report are presented in the following sections.

B-2.0 STANDARD KEY PARAMETERS For the burnup credit analyses, the parameters provided in Table 8-1 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 Summary of the Standard Key Parameters Parameter Limiting Value WF Impact

~

Fuel cladding OD, inches Bias and Uncertainty Fuel rod pitch, inches Bias and Uncertainty Fuel pellet OD, inches Bias and Uncertainty Fuel enrichment, wt% 235U Bias and Uncertainty Fuel density, g/cm3 Bias Distance from Bottom of Fuel Assembly to Bias Beginning of Active Length, inches Hl-2220020 Rev. 2 Page B-2 of 4 Copyright © 2022 Ho/tee lnternotional, all rights reserved

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INT ER N Al IONAL B-3.0 KEV PARAMETERS FOR THE BURNUP CREDIT In additional to the parameters presented in Section B-2.0, 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 Summary of Key Parameters for the Burnup Credit Parameter Limiting Value Impact Core Operating Parameters Maximum fuel temperature, K W, F Bias Maximum core moderator temperature, K

~

Bias Soluble boron concentration (cycle average), ppm

.::; 1150 Bias Fuel Inserts and IBA WF Irradiation duration with fuel inserts, GWd/mtU No restriction _

Bias WABA1 absorber content, wt% 84(

Bias WABA absorber ID, inches WABA absorber OD, inches Bias Number of the IFBA rods Bias IFBA1 ZrB2 coating loading, mg 10B/inch Bias Burnup-weighted cycle-average RCCA insertion

!, 8 Bias (potential) depth during full power operation2, inches Depletion Related Fuel Geometry Changes

W, F Fuel rod growth, inches Bias and Uncertainty Fuel grid growth, inches Bias and Uncertainty Other Parameters Axial burnup profile No restriction Bias Burnup uncertainty, %

!, 5 Uncertainty Cooling time for Region 2, years

~ 0, 1, 5, 10, and 20 Different loading curves 1 [

]4a, 4b 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.

8-4.0 Criticality Safety Analysis of SFP for Callaway Proprietary Information PROPOSED RULES FOR PERMISSIBLE LOADING HOLTEC IN TER N ATIONAL 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.

A cell can either

a.

Contain a Region 1 assembly; or

b.

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 1 assembly 4.1.1 None of the face-adjacent cells may contain a Region 1 assembly; 4.1.2 A minimum of two (2) of the face-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 Proprietary Information HO L TEC IN TER N Al IONAL APPENDIX C RG 1.240 COMPLIANCE The table below provides a summary that confirms compliance with clarifications and exceptions to the guidance in NEI 12-16 [3], 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.

Item Subject Notes / Explanation C.1.x 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 to justify 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 simplifications 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 doesn't 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., IBA parameters for evaluation.

with the cutback regions are neglected) or neglected (e.g.,

blankets).

Item C.1.x g

h i

j k

I Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC INl ER N A1 IONAI.

Subject Notes / Explanation Section 5.1.6 discusses a conservative approach to Not applicable modeling integral burnable absorbers using nominal dimensions combined with a minimum absorber loading...

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.

... 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.

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 j!VOid confounding effects that obscure trends or that lead conditions.

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

Item C.1.x m

n 0

p q

Criticality Safety Analysis of SFP for Callaway Proprietary Information HOLTEC IN TER N ATIONAL Subject Notes / Explanation Section A.2.2 states that startup critical data from boiling-Not applicable water reactors (BWRs) can be used to benchmark depletion codes and compute a bias and bias uncertainty...

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...

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 pools 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 require justification 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 or applicants are responsible for justifying use of the guidance in NEI 12-16, Revision 4, in any such applications.

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.

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.

v t e Letter Sequence Request
EPID:L-2022-LLA-0132, License Amendment Request Regarding Proposed Technical Specification Changes for Spent Fuel Storage (LDCN 22-0015) (Approved, Closed)
Initiation Request, Request, Request, Request, Request Acceptance, Acceptance Supplement, Supplement, Supplement, Supplement Administration Withholding Request Acceptance, Withholding Request Acceptance Questions 24 January 2023 Answers 21 February 2023 Results Approval Other: ML23052A045, ML23052A046, ML23052A047, ULNRC-06796, Enclosure 6 - Affidavit for Withholding by Kimberly Manzione
MONTHYEAR2022-06-30 [Table View]

ML22299A235

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Title:

SUMMARY

SUMMARY

8.0 CONCLUSION

9.0 REFERENCES

SUMMARY

8.0 CONCLUSION

9.0 REFERENCES

SUMMARY

1.0 INTRODUCTION

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