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Supplemental Information for License Amendment Request Regarding New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies, with Proposed Changes to Technical Specifications 4.3.1 and 5.6.5
	ML21312A457
Person / Time
Site:	LaSalle
Issue date:	11/04/2021
From:	Gullott D; Exelon Generation Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML21312A456	List: RS-21-115, Supplemental Information for License Amendment Request Regarding New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies, with Proposed Changes to Technical Specifications 4.3.1 and 5.6.5;
References
	RS-21-115
	Download: ML21312A457 (76)
	v • d • e

PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 4300 Winfield Road Warrenville, IL 60555 630 657 2000 Office RS-21-115 10 CFR 2.390 November 4, 2021 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374

Subject:

Supplemental Information for License Amendment Request Regarding New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies, with Proposed Changes to Technical Specifications 4.3.1 and 5.6.5

References:

1. Letter from P. Simpson (Exelon Generation Company, LLC) to Nuclear Regulatory Commission (NRC), License Amendment Request Regarding New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies, with Proposed Changes to Technical Specifications 4.3.1 and 5.6.5, dated June 30, 2021 (Agencywide Documents Access and Management System (ADAMS) Package Accession No. ML21183A169)

2. Letter from B. Vaidya (NRC) to D. Gullott, "LaSalle, Unit Nos. 1 And 2 -

Acceptance Of Requested Licensing Action Re: License Amendment Request Regarding New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies, with Proposed Changes to Technical Specifications Sections 4.3.1 and 5.6.5 (EPID NO. EPID-L-2021-LLA-0124)," dated July 29, 2021.

In Reference 1, Exelon Generation Company, LLC (EGC) submitted a license amendment request to incorporate methodologies found in NEDE-33931P, LaSalle County Station Fuel Storage Criticality Safety Analysis for use at LaSalle County Station (LSCS).

Following staff review of the referenced license amendment request (Reference 2), the NRC raised questions regarding the proprietary markings in NEDE-33931P. As a result, the NRC held a closed meeting on September 2, 2021 between key stakeholders from EGC, General Electric (GE) and the NRC.

During the time between the closed meeting and submittal of this letter, key stakeholders revised NEDE-33931P and NEDO-33931 to ensure the appropriate information was made available for public disclosure and the proprietary information remained as such.

November 4, 2021 U. S. Nuclear Regulatory Commission Page 2 The purpose of this letter is to transmit Revision 1 of NEDO-33931 and NEDC-33931P, non-proprietary and proprietary versions along with and the associated affidavits.

EGC has reviewed the information supporting a finding of no significant hazards consideration and the environmental consideration provided to the NRC in Reference 1. The supplemental information provided in this letter does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration. Furthermore, the supplemental information provided in this letter does not affect the bases for concluding that neither an environmental impact statement nor an environmental assessment needs to be prepared in connection with the proposed amendment.

The following attachments are included with this letter: : Affidavits Supporting Request to Withhold Information from Public Disclosure : NEDC-33931P, "LaSalle County Station Fuel Storage Criticality Safety Analysis,"

Revision 1, dated October 2021. : NEDO-33931, "LaSalle County Station Fuel Storage Criticality Safety Analysis,"

Revision 1, dated October 2021.

In accordance with 10 CFR 50.91, "Notice for public comment; State consultation,"

paragraph (b), a copy of this letter is being provided to the designated State Officials.

There are no regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mr. Jason C. Taken at (630) 657-3660.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 4th day of November 2021.

Gullott, David Digitally signed by Gullott, David M.

M. Date: 2021.11.04 09:43:39 -05'00' David M. Gullott Director, Licensing & Regulatory Affairs Exelon Generation Company, LLC Attachment 2 contains Proprietary Information.

When separated from Attachment 2, this document is decontrolled.

November 4, 2021 U. S. Nuclear Regulatory Commission Page 3 Attachments:

1. Affidavits Supporting Request to Withhold Information from Public Disclosure

2. NEDC-33931P, "LaSalle County Station Fuel Storage Criticality Safety Analysis," Revision 1, dated October 2021.

3. NEDO-33931, "LaSalle County Station Fuel Storage Criticality Safety Analysis," Revision 1, dated October 2021.

cc: U.S. NRC Region III, Regional Administrator U.S. NRC Senior Resident Inspector, LaSalle County Station Illinois Emergency Management Agency - Division of Nuclear Safety

ATTACHMENT 1 Affidavits Supporting Request to Withhold Information from Public Disclosure

Global Nuclear Fuel - Americas AFFIDAVIT I, Brian R. Moore, state as follows:

(1) I am General Manager, Core & Fuel Engineering, Global Nuclear Fuel - Americas, LLC (GNF-A), and have been delegated the function of reviewing the information described in paragraph (2) which is sought to be withheld, and have been authorized to apply for its withholding.

(2) The information sought to be withheld is contained in GNF-A proprietary report, NEDC-33931P, LaSalle County Station Fuel Storage Criticality Safety Analysis, Revision 1, October 2021. GNF-A proprietary information within the text and tables is identified by a dotted underline placed within double square brackets.

((This sentence is an example.{3})) Figures and large objects containing GNF-A proprietary information are identified with double square brackets before and after the object. In all cases, the superscript notation {3} refers to Paragraph (3) of this affidavit, which provides the basis for the proprietary determination.

(3) In making this application for withholding of proprietary information of which it is the owner or licensee, GNF-A relies upon the exemption from disclosure set forth in the Freedom of Information Act (FOIA), 5 USC Sec. 552(b)(4), and the Trade Secrets Act, 18 USC Sec. 1905, and NRC regulations 10 CFR 9.17(a)(4), and 2.390(a)(4) for trade secrets (Exemption 4). The material for which exemption from disclosure is here sought also qualify under the narrower definition of trade secret, within the meanings assigned to those terms for purposes of FOIA Exemption 4 in, respectively, Critical Mass Energy Project v. Nuclear Regulatory Commission, 975 F2d 871 (DC Cir. 1992), and Public Citizen Health Research Group v. FDA, 704 F2d 1280 (DC Cir. 1983).

(4) Some examples of categories of information which fit into the definition of proprietary information are:

a. Information that discloses a process, method, or apparatus, including supporting data and analyses, where prevention of its use by GNF-A's competitors without license from GNF-A constitutes a competitive economic advantage over other companies;

b. Information which, if used by a competitor, would reduce his expenditure of resources or improve his competitive position in the design, manufacture, shipment, installation, assurance of quality, or licensing of a similar product;

c. Information which reveals aspects of past, present, or future GNF-A customer-funded development plans and programs, resulting in potential products to GNF-A;

d. Information which discloses patentable subject matter for which it may be desirable to obtain patent protection.

NEDC-33931P Revision 1 Affidavit Page 1 of 3

The information sought to be withheld is considered to be proprietary for the reasons set forth in paragraphs (4)a. and (4)b. above.

(5) To address 10 CFR 2.390 (b) (4), the information sought to be withheld is being submitted to NRC in confidence. The information is of a sort customarily held in confidence by GNF-A, and is in fact so held. The information sought to be withheld has, to the best of my knowledge and belief, consistently been held in confidence by GNF-A, no public disclosure has been made, and it is not available in public sources. All disclosures to third parties including any required transmittals to NRC, have been made, or must be made, pursuant to regulatory provisions or proprietary agreements which provide for maintenance of the information in confidence. Its initial designation as proprietary information, and the subsequent steps taken to prevent its unauthorized disclosure, are as set forth in paragraphs (6) and (7) following.

(6) Initial approval of proprietary treatment of a document is made by the manager of the originating component, the person most likely to be acquainted with the value and sensitivity of the information in relation to industry knowledge, or subject to the terms under which it was licensed to GNF-A.

(7) The procedure for approval of external release of such a document typically requires review by the staff manager, project manager, principal scientist or other equivalent authority, by the manager of the cognizant marketing function (or his delegate), and by the Legal Operation, for technical content, competitive effect, and determination of the accuracy of the proprietary designation. Disclosures outside GNF-A are limited to regulatory bodies, customers, and potential customers, and their agents, suppliers, and licensees, and others with a legitimate need for the information, and then only in accordance with appropriate regulatory provisions or proprietary agreements.

(8) The information identified in paragraph (2), above, is classified as proprietary because it contains details of GNF-As fuel design and licensing methodology. The development of this methodology, along with the testing, development and approval was achieved at a significant cost to GNF-A or its licensor.

The development of the fuel design and licensing methodology along with the interpretation and application of the analytical results is derived from the extensive experience database that constitutes a major GNF-A asset.

(9) Public disclosure of the information sought to be withheld is likely to cause substantial harm to GNF-A's competitive position and foreclose or reduce the availability of profit-making opportunities. The information is part of GNF-A's comprehensive BWR safety and technology base, and its commercial value extends beyond the original development cost. The value of the technology base goes beyond the extensive physical database and analytical methodology and includes development of the expertise to determine and apply the appropriate evaluation process. In addition, the technology base includes the value derived from providing analyses done with NRC-approved methods.

NEDC-33931P Revision 1 Affidavit Page 2 of 3

The research, development, engineering, analytical, and NRC review costs comprise a substantial investment of time and money by GNF-A.

The precise value of the expertise to devise an evaluation process and apply the correct analytical methodology is difficult to quantify, but it clearly is substantial.

GNF-A's competitive advantage will be lost if its competitors are able to use the results of the GNF-A experience to normalize or verify their own process or if they are able to claim an equivalent understanding by demonstrating that they can arrive at the same or similar conclusions.

The value of this information to GNF-A would be lost if the information were disclosed to the public. Making such information available to competitors without their having been required to undertake a similar expenditure of resources would unfairly provide competitors with a windfall, and deprive GNF-A of the opportunity to exercise its competitive advantage to seek an adequate return on its large investment in developing and obtaining these very valuable analytical tools.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on this 15th day of October 2021.

Brian R. Moore General Manager, Core & Fuel Engineering Global Nuclear Fuel - Americas, LLC 3901 Castle Hayne Road Wilmington, NC 28401 Brian.Moore@ge.com NEDC-33931P Revision 1 Affidavit Page 3 of 3

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ATTACHMENT 3 Non-Proprietary Version NEDO-33931, "LaSalle County Station Fuel Storage Criticality Safety Analysis," Revision 1, dated October 2021

Global Nuclear Fuel NEDO-33931 Revision 1 October 2021 Non-Proprietary Information LaSalle County Station Fuel Storage Criticality Safety Analysis Copyright 2021 Global Nuclear Fuel, All Rights Reserved

NEDO-33931 Revision 1 Non-Proprietary Information INFORMATION NOTICE This is a non-proprietary version of the document NEDC-33931P, Revision 1, which has the proprietary information removed. Portions of the document that have been removed are indicated by an open and closed bracket as shown here (( )).

IMPORTANT NOTICE REGARDING CONTENTS OF THIS REPORT Please Read Carefully The design, engineering, and other information contained in this document are furnished for the purpose of supporting LaSalle County Station evaluation of spent fuel pool criticality. The use of this information by anyone other than LaSalle County Station, or for any purpose other than that for which it is furnished by GNF is not authorized; and with respect to any unauthorized use, GNF makes no representation or warranty, express or implied, and assumes no liability as to the completeness, accuracy, or usefulness of the information contained in this document, or that its use may not infringe privately owned rights.

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NEDO-33931 Revision 1 Non-Proprietary Information Revision Summary Revision Date Summary 0 April 2021 Initial issue 1 October 2021 Revised marked proprietary content iii

NEDO-33931 Revision 1 Non-Proprietary Information TABLE OF CONTENTS

1.0 INTRODUCTION

............................................................................................................... 1 2.0 REQUIREMENTS .............................................................................................................. 1 3.0 METHOD OF ANALYSIS ................................................................................................. 1 3.1 Cross-Sections ......................................................................................................................... 2 3.2 Geometry Treatment ................................................................................................................ 2 3.3 Convergence Checks ............................................................................................................... 3 3.4 Validation and Computational Basis ....................................................................................... 3 3.5 In-Core k Methodology .......................................................................................................... 6 3.6 Definitions ............................................................................................................................... 7 3.7 Assumptions and Conservatisms ............................................................................................. 8 4.0 FUEL DESIGN BASIS ........................................................................................................ 9 4.1 GNF3 Fuel Description.......................................................................................................... 10 4.2 Fuel Model Description ......................................................................................................... 13 5.0 CRITICALITY ANALYSIS OF SPENT FUEL STORAGE RACKS ......................... 14 5.1 Description of Spent Fuel Storage Racks .............................................................................. 14 5.1.1 Unit 1 ......................................................................................................................... 14 5.1.2 Unit 2 ......................................................................................................................... 16 5.2 Spent Fuel Storage Rack Models ........................................................................................... 17 5.3 Design Basis Lattice Selection .............................................................................................. 20 5.4 Normal Configuration Analysis ............................................................................................. 24 5.4.1 Analytical Models ...................................................................................................... 24 5.4.2 Results ........................................................................................................................ 24 5.5 Bias Cases .............................................................................................................................. 26 5.5.1 Depletion Bias Cases ................................................................................................. 26 5.5.2 Normal Bias Cases ..................................................................................................... 26 5.5.3 Abnormal/Accident Bias Cases ................................................................................. 27 5.5.4 Results ........................................................................................................................ 30 5.6 Uncertainties .......................................................................................................................... 33 5.6.1 Tolerance Analytic Models ........................................................................................ 33 5.6.2 Uncertainty Results .................................................................................................... 34 5.7 Maximum Reactivity ............................................................................................................. 37 6.0 INTERFACES BETWEEN UNIT 1 AND UNIT 2 STORAGE POOLS...................... 38

7.0 CONCLUSION

S ................................................................................................................ 38

8.0 REFERENCES

.................................................................................................................. 39 iv

NEDO-33931 Revision 1 Non-Proprietary Information APPENDIX A MCNP-05P CODE VALIDATION ................................................................ 40 A.1 Trend Analysis ......................................................................................................................... 45 A.2 Bias and Bias Uncertainty Calculation - Single Sided Tolerance Limit.................................. 49 APPENDIX B LEGACY FUEL STORAGE JUSTIFICATION .......................................... 52 B.1 Legacy Non-GNF Fuel Justification ........................................................................................ 52 B.2 Legacy GNF Fuel Justification ................................................................................................. 53 v

NEDO-33931 Revision 1 Non-Proprietary Information LIST OF TABLES Table 1 - Summary kmax(95/95) Result ......................................................................................... 1 Table 2 - Summary of the Critical Benchmark Experiments ........................................................ 4 Table 3 - Area of Applicability Covered by Code Validation ....................................................... 5 Table 4 - Lattice Dimensions....................................................................................................... 11 Table 5 - Cell Dimensions ........................................................................................................... 11 Table 6 - Channel Dimensions .................................................................................................... 12 Table 7 - Fuel Stack Density as a Function of Gadolinia Concentration .................................... 13 Table 8 - Storage Rack Model Dimensions ................................................................................. 20 Table 9 - Unit 1 GNF3 Fuel Parameter Ranges Studied in Spent Fuel Rack .............................. 21 Table 10 - Unit 2 GNF3 Fuel Parameter Ranges Studied in Spent Fuel Rack ............................ 22 Table 11 - Unit 1 In-Rack k Results - Normal Configurations ................................................. 25 Table 12 - Unit 2 In-Rack k Results - Normal Configurations ................................................. 25 Table 13 - Unit 1 Rack Periphery Study Results ......................................................................... 27 Table 14 - Unit 2 Rack Periphery Study Results ......................................................................... 27 Table 15 - Unit 1 Results for Misplaced Bundles ....................................................................... 28 Table 16 - Unit 2 Results for Misplaced Bundles ....................................................................... 28 Table 17 - Unit 1 Spent Fuel Storage Rack Bias Summary ........................................................ 31 Table 18 - Unit 2 Spent Fuel Storage Rack Bias Summary ........................................................ 32 Table 19 - Unit 1 Spent Fuel Storage Rack Tolerance and Uncertainty k Results ................... 35 Table 20 - Unit 2 Spent Fuel Storage Rack Tolerance and Uncertainty k Results ................... 36 Table 21 - Unit 1 Spent Fuel Storage Rack Results Summary .................................................... 37 Table 22 - Unit 2 Spent Fuel Storage Rack Results Summary .................................................... 37 Table 23 - MCNP-05P Results for the Benchmark Calculations ................................................ 40 Table 24 - Trending Parameters .................................................................................................. 45 Table 25 - Trending Results Summary ........................................................................................ 48 Table 26 - Bias and Bias Uncertainty for MCNP-05P with ENDF/B-VII .................................. 50 Table 27 - Recommended Bias and Bias Uncertainty in Criticality Analyses ............................ 51 Table 28 - Summary Non-GNF Fuel k Compared to GNF3 Design Basis ............................... 52 Table 29 - Limiting Cold As-Designed Eigenvalue of all GNF Bundles at LaSalle ................... 53 vi

NEDO-33931 Revision 1 Non-Proprietary Information LIST OF FIGURES Figure 1 - GNF3 Lattice Configuration ....................................................................................... 10 Figure 2 - Channel 1/8 Cross-Sections ........................................................................................ 12 Figure 3 - GNF3 MID Lattice in MCNP-05P.............................................................................. 14 Figure 4 - Unit 1 Spent Fuel Storage Rack Typical Example ..................................................... 15 Figure 5 - Unit 2 Spent Fuel Storage Rack Typical Example ..................................................... 17 Figure 6 - Unit 1 Storage Rack Model Schematic ....................................................................... 18 Figure 7 - Unit 1 Zoomed Storage Rack Model Schematic ........................................................ 18 Figure 8 - Unit 2 Storage Rack Model Schematic ....................................................................... 19 Figure 9 - Unit 2 Zoomed Storage Rack Model Schematic ........................................................ 19 Figure 10 - Unit 1 Spent Fuel In-Rack versus In-Core Eigenvalues ........................................... 23 Figure 11 - Unit 2 Spent Fuel In-Rack versus In-Core Eigenvalues ........................................... 23 Figure 12 - Finite Misplaced Bundle Model Example ................................................................ 29 Figure 13 - Scatterplot of knorm versus EALF ............................................................................. 46 Figure 14 - Scatterplot of knorm versus wt.% 235U ....................................................................... 46 Figure 15 - Scatterplot of knorm versus wt.% 239Pu ...................................................................... 47 Figure 16 - Scatterplot of knorm versus H/X ................................................................................ 47 Figure 17 - Normality Test of knorm Results ................................................................................ 49 vii

NEDO-33931 Revision 1 Non-Proprietary Information ACRONYMS Term Definition 2D Two-Dimensional AOA Area of Applicability BAS Base Lattice BOL Beginning-of-Life BWR Boiling Water Reactor CFR Code of Federal Regulations EALF Energy of the Average Lethargy Causing Fission

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

GEH GE-Hitachi Nuclear Energy Americas LLC GNF Global Nuclear Fuel - Americas, LLC HTC Haut Taux de Combustion H/X Hydrogen-to-Fissile Ratio LCS LaSalle County Station MID Mid Lattice MOX Mixed Uranium-Plutonium Oxide NCA Nuclear Critical Assembly NEI Nuclear Energy Institute NRC Nuclear Regulatory Commission SCCG Standard Cold Core Geometry UO2 Uranium Dioxide VAN Vanished Lattice viii

NEDO-33931 Revision 1 Non-Proprietary Information

1.0 INTRODUCTION

This report describes the criticality analysis and results for the LaSalle County Station (LCS) Unit 1 and Unit 2 spent fuel racks. It includes sufficient detail on the methodology and analytical models utilized in the criticality analysis to verify that the storage rack systems have been accurately and conservatively represented. This report includes analysis of Boral spent fuel racks in LCS Unit 1 spent fuel pool, and Boraflex spent fuel racks with no credit for the Boraflex neutron absorber and credit for NETCO-SNAP-IN neutron absorbing inserts in LCS Unit 2 spent fuel pool. This analysis covers the current GNF3 fuel product line and all legacy fuel stored in LCSs spent fuel pools.

The racks are analyzed using the MCNP-05P Monte Carlo neutron transport program and ENDF/B-VII.0 cross-section library. The methodology used in this analysis is the peak Standard Cold Core Geometry (SCCG) in-core eigenvalue (k) criterion. A maximum SCCG, uncontrolled peak in-core k of 1.275 as defined by the lattice physics code TGBLA06 (Reference 1) is set as the limit for this analysis. As demonstrated in Table 1, the analysis resulted in a storage rack maximum k-effective (kmax(95/95)) less than 0.95 for normal and credible abnormal operation with tolerances and uncertainties taken into account.

Table 1 - Summary kmax(95/95) Result Region kmax(95/95)

Unit 1 Boral Spent Fuel Rack 0.89232 Unit 2 Boraflex Spent Fuel Rack 0.93900 with NETCO-SNAP-IN Inserts 2.0 REQUIREMENTS Title 10 of the Code of Federal Regulations (CFR) Part 50 defines the requirements for the prevention of criticality in fuel storage and handling at nuclear power plants. 10 CFR 50.68 details specifically that the storage rack kmax(95/95) for spent fuel storage racks must be demonstrated to be 0.95 for normal and credible abnormal operation with tolerances and computational uncertainties taken into account. The Standard Review Plan (Reference 2) outlines the standards that must be met for these analyses. All necessary requirements are met in this analysis. Nuclear Energy Institute (NEI) 12-16 (Reference 3) is used as the guidance document for this analysis.

3.0 METHOD OF ANALYSIS In this evaluation, in-core k values and exposure dependent, pin-by-pin isotopic specifications are generated using the GE-Hitachi Nuclear Energy Americas LLC (GEH)/GNF lattice physics production code TGBLA06. TGBLA06 solves Two-Dimensional (2D) diffusion equations with diffusion parameters corrected by transport theory to provide system multiplication factors and perform burnup calculations.

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NEDO-33931 Revision 1 Non-Proprietary Information The fuel storage criticality calculations are then performed using MCNP-05P, the GEH/GNF proprietary version of MCNP5 (Reference 4). MCNP-05P is a Monte Carlo program for solving the linear neutron transport equation for a fixed source or an eigenvalue problem. The code implements the Monte Carlo process for neutron, photon, electron, or coupled transport involving all these particles, and computes the eigenvalue for neutron-multiplying systems. For the present application, only neutron transport was considered.

3.1 Cross-Sections TGBLA06 uses ENDF/B-V cross-section data to perform coarse-mesh, broad-group, diffusion theory calculations. It includes thermal neutron scattering with hydrogen using an S(,) light water thermal scattering kernel.

MCNP-05P uses pointwise (i.e., continuous) cross-section data, and all reactions in a given cross-section evaluation (e.g., ENDF/B-VII.0) are considered. For the present work, thermal neutron scattering with hydrogen was described using S(,) light water thermal scattering kernel. The cross-section tables include all details of the ENDF representations for neutron data. The code requires that all the cross-sections be given on a single union energy grid suitable for linear interpolation; however, the cross-section energy grid varies from isotope to isotope. The libraries include very little data thinning and utilize resonance integral reconstruction error tolerances of 0.001%.

3.2 Geometry Treatment TGBLA06 is a 2D lattice design computer program for Boiling Water Reactor (BWR) fuel bundle analysis. It assumes that a lattice is uniform and infinite along the axial direction and that the lattice geometry and material are reflecting with respect to the lattice boundary along the transverse directions.

MCNP-05P implements a robust geometry representation that can correctly model complex components in three dimensions. An arbitrary three-dimensional configuration is treated as geometric cells bounded by first and second-degree surfaces and some special fourth-degree elliptical tori. The cells are described in a cartesian coordinate system and are defined by the intersections, unions and complements of the regions bounded by the surfaces. Surfaces are defined by supplying coefficients to the analytic surface equations or, for certain types of surfaces, known points on the surfaces. Rather than combining several pre-defined geometrical bodies in a combinatorial geometry scheme, MCNP-05P has the flexibility of defining geometrical shapes from all the first and second-degree surfaces of analytical geometry and elliptical tori and then combining them with Boolean operators. The code performs extensive checking for geometry errors and provides a plotting feature for examining the geometry and material assignments.

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NEDO-33931 Revision 1 Non-Proprietary Information 3.3 Convergence Checks The use of TGBLA06 as a depletion code in this criticality analysis is consistent with its use for BWR fuel design and its associated users manual. Convergence checks are encoded in the standard error routines and the absence of error messages was confirmed in all code output.

In this analysis, the following criticality code parameters were specified. At a minimum, all MCNP-05P cases were run with 20,000 neutrons per generation, 200 cycles skipped, and 500 total cycles run. Some cases were run for more cycles skipped in order to meet all the converge checks.

For this analysis, the following MCNP-05P convergence checks were reviewed and confirmed passed for each case:

Sampling of all cells that contain fissionable material

Matching of first and second half eigenvalue

Fission source entropy check 3.4 Validation and Computational Basis MCNP-05P has been compared to ((` ` ` ` ` ` ` )) critical experiments for validation purposes using ENDF/B-VII.0 nuclear cross-section data. The experiments cover a number of moderator-to-fuel ratios and poison materials that represent material and geometric properties similar to that of BWR fuel lattices both in and out of fuel racks. The critical experiments to which MCNP-05P has been compared are provided in Table 2. All are either low-enriched Uranium Dioxide (UO2) or Mixed Uranium-Plutonium Oxide (MOX) pin lattice in water experiments. The area of applicability (AOA) considered covered by this validation is listed in Table 3, along with the parameters which characterize the spent fuel rack system for comparison. The critical experiment modeling results, along with the calculation of the associated bias and bias uncertainty terms at the 95/95 confidence level using NUREG-6698 (Reference 5) guidance are provided in Appendix A. The study concluded that the appropriate bias to apply to systems covered by this AOA is ((` ` ` ` ` ` ` )), and the appropriate uncertainty of that bias is

((` ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information Table 2 - Summary of the Critical Benchmark Experiments Experiment Experiments Year Where

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NEDO-33931 Revision 1 Non-Proprietary Information Table 3 - Area of Applicability Covered by Code Validation Validation Spent Fuel Rack Parameters Area of Applicability Characteristics Fissionable Material Uranium, Plutonium Uranium, Actinides Chemical Form UO2, MOX UO2, MOX Enrichment (wt.% 235U) wt.% 235U 4.9 wt.% 235U 4.9 Enrichment (wt.% 239Pu) wt.% 239Pu 5.3 wt.% 239Pu 4.9 Physical Form Solid Compound Solid Compound Temperature ~20°C up to ~100°C 4-126°C Moderator (in fuel region) H2O H2O Physical Form Solution Solution Temperature ~20°C up to ~100°C 4-126°C Reflector (in fuel region) H2O H2O Physical Form Solution Solution Temperature 20°C 4-126°C None/Boron/Gadolinium Boron/Gadolinium/

Absorbers Stainless Steel/Copper Fission Products Neutron Energy Spectrum Thermal Thermal Energy of Average Lethargy 3.604E-07 6.8E 8.6 E-7 Causing Fission (MeV) (Limiting In-rack k Case)

Table 3 demonstrates that the AOA of this validation encompasses the majority of storage characteristics of new fuel in the spent fuel storage racks. ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

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` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

For the storage of spent fuel, however, it is appropriate to add additional uncertainty terms to the kmax(95/95) result. Specifically, these items are:

Uncertainty in fuel depletion calculations Consistent with NEI 12-16, a conservative approximation of the fuel depletion uncertainty was quantified by assessing the reactivity difference between a Beginning-of-Life (BOL) system and the exposure dependent, peak reactivity system of interest. Specifically, the cold, in-core, BOL reactivity of the spent fuel rack design basis bundle with no gadolinium present was compared to the reactivity of the exposed design basis bundle at its cold, in-core, peak reactivity statepoint. Both reactivities are calculated for comparison in the rack system. Five percent of the difference in reactivities between these two cases is included as an uncertainty to the spent fuel rack studies in Table 19 and Table 20 to cover the depletion isotopic benchmarking gap including gap for minor actinides and fission products.

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NEDO-33931 Revision 1 Non-Proprietary Information

TGBLA06 eigenvalue uncertainty An additional uncertainty is also added to the fuel rack studies related to eigenvalue calculations performed using TGBLA06. A bias of ((` ` ` ` ` ` ` )) and a 95/95 bias uncertainty of

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

````````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) This uncertainty is applied to the spent fuel racks kmax(95/95) value to cover uncertainty in the assignment of in-core k values to fuel lattices.

3.5 In-Core k Methodology The design of the fuel storage racks provides for a subcritical multiplication factor for both normal and credible abnormal storage conditions. In all cases, the storage rack eigenvalue must be 0.95.

To demonstrate compliance with this limit, the in-core k method is utilized.

The peak in-core k criterion method relies on a well-characterized relationship between infinite lattice k (in-core) for a given fuel design and a specific fuel storage rack k (in-rack) containing that fuel.

The use of an infinite lattice k criterion for demonstrating compliance to fuel storage criticality criteria has been used for all General Electric-supplied storage racks and is currently used for re-rack designs at several plants. This report demonstrates that the methodology is also appropriate for use at the LCS by presenting the following:

A well-characterized, linear relationship between infinite lattice k (in-core) and fuel storage rack k (in-rack)

The use of a design basis lattice with a conservative rack efficiency and in-core k for all criticality analyses The analysis performed to calculate the lattice k to confirm compliance with the above criterion uses the Nuclear Regulatory Commission (NRC)-approved lattice physics methods encoded into the TGBLA06 engineering computer program. One of the outputs of the TGBLA06 solution is the lattice k of a specific nuclear design for a given set of input state parameters (e.g., void fraction, control state, fuel temperature).

Compliance of fuel with specified k limits will be confirmed for each new lattice as part of the bundle design process. Documentation that this has been met will be contained in the fuel design information report, which defines the maximum lattice k for each assembly nuclear design. The process for validating that specific assembly designs are acceptable for storage in the LCS fuel storage racks is provided below.

1. Identify the unique lattices in each assembly design.

2. Deplete the lattices in TGBLA06 using the following conditions:

a. Assembly aligned according to LCS-specific lattice spacing and zero leakage

b. ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

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NEDO-33931 Revision 1 Non-Proprietary Information

c. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

d. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

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i. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

ii. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

f. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

g. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

3. `````````````````````````````````````````````````````````````````````````````````````````

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a. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

b. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

c. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

d. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

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f. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

4. Ensure that the k values obtained from Step 3 for each lattice are less than or equal to the k limit of 1.275.

Justification for the storage of all legacy fuel at LCS is provided in Appendix B.

3.6 Definitions Fuel Assembly - is a complete fuel unit consisting of a basic fuel rod structure that may include large central water rods. Several shorter rods may be included in the assembly. These are called part-length rods. A fuel assembly includes the fuel channel.

Gadolinia - The compound Gd2O3. The gadolinium content in integral burnable absorber fuel rods is usually expressed in weight percentage gadolinia.

Lattice - An axial zone of a fuel assembly within which the nuclear characteristics of the individual rods are unchanged.

Base Lattice (BAS)- An axial zone of a fuel assembly located in the bottom half of the bundle within which all possible fuel rod locations for a given fuel design are occupied.

Mid Lattice (MID) - ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information Vanished Lattice (VAN) - An axial zone of a fuel assembly typically in the upper half of the bundle within which a number of possible fuel rod locations are unoccupied.

Rack Efficiency - The ratio of a particular lattice statepoint in-rack eigenvalue (k) to its associated lattice nominal in-core eigenvalue (k). This value allows for a straightforward comparison of a racks criticality response to varying lattice designs within a particular fuel product line. A lower rack efficiency implies increased reactivity suppression capability relative to an alternate design with a higher rack efficiency.

Design Basis Lattice - The lattice geometry, exposure history, and corresponding fuel isotopics for a fuel product line that result in the highest rack efficiency in a sensitivity study of reasonable fuel parameters at the desired in-core reactivity. This lattice is used for all normal, abnormal, and tolerance evaluations in the fuel rack analysis.

3.7 Assumptions and Conservatisms The fuel storage rack criticality calculations are performed with the following assumptions to ensure the true system reactivity is always less than the calculated reactivity:

1. ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

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2. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

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3. Design basis lattices with in-core k values greater than the proposed 1.275 in-core k limit are used for all criticality analyses.

4. ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

````````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) Sensitivity studies of the storage system reactivity to these depletion parameters are presented in Section 5.5. ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information

5. For conservatism, only positive reactivity differences from nominal conditions determined from depletion sensitivity and abnormal configuration analyses are added as biases to the final storage rack kmax(95/95).

6. Neutron absorption in spacer grids, concrete, activated corrosion and wear products (CRUD),

and axial blankets is ignored to limit parasitic losses in non-fuel materials.

7. TGBLA06 defined lumped fission products and Xe-135 are both conservatively ignored for MCNP-05P in-rack k calculations.

8. ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

````````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

9. Only 10B is modeled in the rack poison panel/insert. Each panel/insert is assumed to contain the minimum areal density, 0.022 g/cm2 for Unit 1 and 0.0086 g/cm2 for Unit 2. All other material is ignored. Ignoring the other materials conservatively limits neutron absorption in the panel/insert.

10. For Unit 2, no credit is taken for the Boraflex in the storage racks in the analysis, and all material between the inner cell walls is modeled as water. This modeling is reasonable because there is small amount of structure material associated with the Boraflex.

4.0 FUEL DESIGN BASIS This rack criticality analysis covers the GNF3 fuel product line and all legacy fuel stored at LCS.

Justification the storage of all legacy fuel at LCS is provided in Appendix B. The description of GNF3 fuel is in Sections 4.1. The GNF3 fuel bundle is used to determine the design basis bundle in Section 5.3.

All fuel is UO2 with some fuel rods containing gadolinia, Gd2O3.

This criticality analysis covers reconstituted fuel where a rod containing fuel is replaced with another fueled or non-fueled rod. This analysis does not cover reconstituted fuel where there are missing rod locations that are not part of the normal fuel product line design.

This criticality analysis also covers the storage of non-fuel items such as channels in spent fuel rack locations because this analysis covers peak reactivity fuel in every rack cell location.

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NEDO-33931 Revision 1 Non-Proprietary Information 4.1 GNF3 Fuel Description The GNF3 fuel lattice configuration is a 10x10 fuel rod array ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) as shown in Figure 1 with corresponding dimensions in Table 4 and Table 5. Figure 1 also demonstrates the part-length rod locations. Fuel channel dimensions are provided in Figure 2 and Table 6. Pellet stack density is in Table 7. ((` ` ` ` ` ` ` ` ` ` ` ` ` ` `

````````````````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

((

` ` ` ` ` ))

Figure 1 - GNF3 Lattice Configuration Page 10

NEDO-33931 Revision 1 Non-Proprietary Information Table 4 - Lattice Dimensions Dimension Item mm in

((` ` ` ` ` ` ` ` ` ` ` ` ` ````` `````

Channel

```````````````````` ` ````` `````

`````````````` ` ``` ``````

Fuel Rod ``````````````````` ` ````` ``````

``````````````````` ` ```` ``````

Pellet `````````````` ` ```` ` ` ` ` ` ` ` ` ` ` ))

`````````````

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `````````````` ` `````````````

```` `````````````````

`````````````` ` `````````````

))

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ````` `````

Bundle Lattice `````````````` ` ```` `````

``````````````````````` ` ````` ` ` ` ` ` ` ` ` ` ))

Table 5 - Cell Dimensions Lattice Channel 1/2 Wide Gap, Q 1/2 Narrow Gap, R Control Blade Pitch, S Type Name mm in mm in mm in

((` ```` ```` ````` ```` ````` `````` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information

((

` ` ` ` ` ))

Figure 2 - Channel 1/8 Cross-Sections Table 6 - Channel Dimensions Channel Name 93AV Channel Section Zone 1 Zone 2 Dimension mm in mm in

((` ` ` ` ` ` ` ` ` ` ` ` ` `

``` ```` ````` ```` `````

``

`````````````` ``` ```` `````

```````````` ``` ````` `````

````````````````

``` ```` ` ` ` ` ` ` ` ` ` ))

`

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NEDO-33931 Revision 1 Non-Proprietary Information Table 7 - Fuel Stack Density as a Function of Gadolinia Concentration Gadolinia Concentration ((` ` ` ` ```` ```` ```` ```` ```` ```` ````

(wt. fraction)

Pellet Density ```````

`````` `````` `````` `````` `````` `````` ``````

(g/cc) ` ` ` ))

4.2 Fuel Model Description The fuel models considered include 2D geometric modeling of all fuel material, cladding, water rods, and channels. In the depletion model, appropriate depletion time steps are used consistent with depletion timesteps used in BWR core design analyses. ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

````````````````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

Pin specific isotopic modeling as a function of exposure is performed based on the lattice physics code TGBLA06. To obtain the isotopic composition of the fuel pins, each lattice design considered is burned at reactor operating conditions ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) and depleted through to a final exposure of ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

````````````````````````````````````````````````````````````````````````````````````````````````````

````````````````````````````````````` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) The isotopics utilized exclude Xe-135 and TGBLA06 defined lumped fission products ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) An example of a GNF3 MID lattice model in MCNP-05P is depicted in Figure 3.

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NEDO-33931 Revision 1 Non-Proprietary Information

((

` ` ` ))

Figure 3 - GNF3 MID Lattice in MCNP-05P The fuel loadings considered for each lattice span a range of exposures, average enrichments, number of gadolinia rods, gadolinia concentrations, and void histories considered to be reasonably representative of any LCS fuel design. The lattice type and exposure history that results in the worst-case rack efficiency for an in-core k greater than the proposed limit is then used to define the design basis lattice. This lattice is assumed to be stored in every location in the rack being analyzed. Details on the determination of the design basis lattice using the process outlined above are presented in Section 5.3.

5.0 CRITICALITY ANALYSIS OF SPENT FUEL STORAGE RACKS 5.1 Description of Spent Fuel Storage Racks 5.1.1 Unit 1 The fuel storage racks are free-standing in the spent fuel storage pool. A typical fuel assembly storage rack is shown in Figure 4. The spent fuel racks are designed to maintain the stored spent fuel in a space geometry that precludes the possibility of criticality.

The poison wall rack design is a honeycomb array of identical stainless steel boxes. They are made of full length 0.090-inch thick sheets which provide smooth wall storage cells. The boxes are 6x6x169 inches. The racks have a nominal 6.264-inch center-to-center distance between fuel assemblies placed in the storage racks. A 0.079-inch thick sheets of neutron poison material with a minimum areal density of 0.022 g 10B/cm2 is captured between the side walls of each box and sheathing welded to the sides of the box.

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NEDO-33931 Revision 1 Non-Proprietary Information The boxes are welded together along the corner edges. The Boral sheets are axially centered on the active fuel region of the stored fuel assemblies and extend to the ends of the natural or slightly enriched uranium end caps. Each sheet is contained vertically by the sheathing. No poison material is provided on the periphery of the rack array.

Figure 4 - Unit 1 Spent Fuel Storage Rack Typical Example Page 15

NEDO-33931 Revision 1 Non-Proprietary Information 5.1.2 Unit 2 The fuel storage racks are free-standing in the spent fuel storage pool. A typical fuel assembly storage rack is shown in Figure 5. The spent fuel racks are designed to maintain the stored spent fuel in a space geometry that precludes the possibility of criticality. The racks will maintain this subcritical array when subjected to maximum earthquake conditions, dropped fuel assembly accident conditions, and any uplift forces generated by the fuel handling equipment.

The poison wall rack design is a honeycomb array of identical stainless steel boxes. They are made of full-length 0.090-inch thick sheets which provide smooth wall storage cells. The boxes are 6x6x168 inches. The racks have a nominal 6.255-inch center-to-center distance between fuel assemblies placed in the storage racks, and 0.075-inch thick sheets of Boraflex neutron poison material, which are not credited in this analysis, between the side walls of all adjacent boxes. To provide space for the poison sheet between boxes, a double row of matching flat round raised areas are coined in the side walls of all boxes. The raised dimension of these locally formed areas on each box wall is half the thickness of the poison sheet. The boxes are fused together at all these local areas. The poison sheets are scalloped along their edges to clear these areas. The sheets are axially centered on the active fuel region of the stored fuel assemblies. Each sheet is contained vertically by a stop plate at the bottom of the poison.

The plate is welded on one of the adjacent box walls. A 0.031-inch thick sheet of stainless steel which is welded to the box intermittently all around, between adjacent racks at the East-West and North-South walls.

Neutron-absorbing inserts have been placed in all cells accessible by fuel in the Unit 2 spent fuel pool.

These rack inserts with a minimum areal density of 0.0086 g 10B/cm2 are chevron in shape and held in place by the force of the insert against the stainless steel wall of the cell. The inserts provide the pool neutron-absorbing criticality control to maintain the Unit 2 spent fuel pool subcritical without the credit of Boraflex.

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NEDO-33931 Revision 1 Non-Proprietary Information Figure 5 - Unit 2 Spent Fuel Storage Rack Typical Example 5.2 Spent Fuel Storage Rack Models This analysis covers a bounding storage configuration of maximum reactivity fuel in every storage location for each of the unique LCS Unit 1 and Unit 2 rack designs.

A 2D infinite storage array with periodic boundary conditions is modeled to conservatively represent the nominal spent fuel pool configuration. Images of single elements of the model are provided in Figures 6 to 9. Dimensions and tolerances are presented in Table 8. This single element is used to define a 10x10 rack array with periodic boundary conditions for each LCS unit. This array is used in the design basis bundle selection process in Section 5.3.

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information

((

` ` ` ` ` ))

Figure 6 - Unit 1 Storage Rack Model Schematic

((

` ` ` ` ` ))

Figure 7 - Unit 1 Zoomed Storage Rack Model Schematic Page 18

NEDO-33931 Revision 1 Non-Proprietary Information

((

` ` ` ` ` ))

Figure 8 - Unit 2 Storage Rack Model Schematic

((

` ` ` ` ` ))

Figure 9 - Unit 2 Zoomed Storage Rack Model Schematic Page 19

NEDO-33931 Revision 1 Non-Proprietary Information Table 8 - Storage Rack Model Dimensions Unit 1 Unit 1 Unit 2 Unit 2 nominal tolerance nominal tolerance (inch) (+inch) (inch) (+inch)

Rack pitch 6.264 0.030 6.255 0.040 Rack cell inner dimension 6.050 0.030 6.000 0.020 Rack cell wall thickness 0.090 0.004 0.090 0.005 Boral panel thickness 0.079 0.007 - -

Boral panel width (( - -

Boral sheathing wall thickness - -

Boral sheathing width - -

Boral sheathing inside space )) - -

Insert wing thickness - - 0.065 0.005 Insert wing width - - (( ))

5.3 Design Basis Lattice Selection Table 9 and Table 10 define the lattice designs and exposure histories that were explicitly studied in the spent fuel storage rack to determine the geometric configuration and isotopic composition that results in the worst rack efficiency for each LCS unit. Note that void state is not a relevant parameter for zero exposure peak reactivity cases, and therefore, only a single result is presented for these fuel loadings. The highest rack efficiency with an in-core k greater than the proposed limit of 1.275 is found to result from the parameters defined in Case 3 for Unit 1 and Unit 2. The geometry and isotopics defined for this case are used to define all bundles in the remaining spent fuel rack analyses.

Figure 10 and Figure 11 present graphs that demonstrate the linear nature of the in-rack to in-core results over all rack efficiency cases studied in the rack system. Figures also provide infinite in-rack and in-core eigenvalue pairs ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) to allow for the linear relationship to be demonstrated over a large range of exposures.

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NEDO-33931 Revision 1 Non-Proprietary Information Table 9 - Unit 1 GNF3 Fuel Parameter Ranges Studied in Spent Fuel Rack Average Number Peak-Lattice Void Lattice Gadolinia Reactivity TGBLA06 MCNP-05P of Rack Case Enrichment Concentration Exposure Defined Defined Type (%) Gadolinia Efficiency (Gd wt. %) In-Core k In-Rack k (wt.% 235U) Rods (GWD/ST) 1 ((` ` ` `` ``` `` ` `` ``````` 0.85341 ((` ` ` ` ` ` `

2 ``` `` ``` `` ` `` ``````` 0.86474 ```````

3 ``` ` ``` `` ` `` ``````` 0.87195 ```````

4 ``` `` ``` `` ` `` ``````` 0.85454 ```````

5 ``` `` ``` `` ` `` ``````` 0.84002 ```````

6 ``` `` ``` `` ` `` ``````` 0.86127 ```````

7 ``` ` ``` `` ` `` ``````` 0.86599 ```````

8 ``` `` ``` `` ` `` ``````` 0.85353 ```````

9 ``` ` ``` `` ` `` ``````` 0.86310 ```````

10 ``` `` ```` `` ` `` ``````` 0.85171 ```````

11 ``` `` ```` ` ` `` ``````` 0.85429 ```````

12 ``` `` ```` `` ` `` ``````` 0.85378 ```````

13 ``` ` ```` ` ` ` ``````` 0.85716 ```````

14 ``` ` ```` `` ` ` ``````` 0.85448 ```````

15 ``` ` ```` ` ` ` ``````` 0.83824 ```````

16 ``` ` ``` ` ` ` ``````` 0.83236 ```````

17 ``` ` ``` ` ` ` ``````` 0.83010 ```````

18 ``` ` ``` ` ` ` ``````` 0.82894 ```````

19 ``` `` ```` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) 0.81981 ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information Table 10 - Unit 2 GNF3 Fuel Parameter Ranges Studied in Spent Fuel Rack Average Number Peak-Lattice Void Lattice Gadolinia Reactivity TGBLA06 MCNP-05P of Rack Case Enrichment Concentration Exposure Defined Defined Type (%) Gadolinia Efficiency (Gd wt. %) In-Core k In-Rack k (wt.% 235U) Rods (GWD/ST) 1 ((` ` ` `` ``` `` ` `` ``````` 0.89691 ((` ` ` ` ` ` `

2 ``` `` ``` `` ` `` ``````` 0.90894 ```````

3 ``` ` ``` `` ` `` ``````` 0.91664 ```````

4 ``` `` ``` `` ` `` ``````` 0.88390 ```````

5 ``` `` ``` `` ` `` ``````` 0.89579 ```````

6 ``` `` ``` `` ` `` ``````` 0.89851 ```````

7 ``` ` ``` `` ` `` ``````` 0.90921 ```````

8 ``` `` ``` `` ` `` ``````` 0.90202 ```````

9 ``` `` ```` `` ` `` ``````` 0.89685 ```````

10 ``` ` ``` `` ` `` ``````` 0.90651 ```````

11 ``` `` ```` ` ` `` ``````` 0.89891 ```````

12 ``` `` ```` `` ` `` ``````` 0.89916 ```````

13 ``` ` ```` ` ` ` ``````` 0.90095 ```````

14 ``` ` ```` `` ` ` ``````` 0.90000 ```````

15 ``` ` ```` ` ` ` ``````` 0.87696 ```````

16 ``` ` ``` ` ` ` ``````` 0.87442 ```````

17 ``` ` ``` ` ` ` ``````` 0.87198 ```````

18 ``` `` ```` ` ` ` ``````` 0.86407 ```````

19 ``` ` ``` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) 0.86872 ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information

((

CCCCC))

Figure 10 - Unit 1 Spent Fuel In-Rack versus In-Core Eigenvalues

((

CCCCC))

Figure 11 - Unit 2 Spent Fuel In-Rack versus In-Core Eigenvalues Page 23

NEDO-33931 Revision 1 Non-Proprietary Information 5.4 Normal Configuration Analysis 5.4.1 Analytical Models The most reactive normal configuration was determined by studying the reactivity effect of the following credible normal scenarios:

Storage of non-channeled assemblies

Eccentric loadings o Unit 1 When neutron absorber panels with an areal density above 0.01 g 10B/cm2 are present on all four sides of the fuel assembly, a centrally located positioning of the fuel assembly in the storage cell is the most reactive configuration.

Therefore, no eccentric loading cases were performed for Unit 1 consistent with NEI 12-16.

o Unit 2

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

``````````````````````````````````````````````````````

``````````````````````````````````````````````````

```````````````

o ``````````````````````````````

o ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

Pool moderator temperature variation As the non-channeled assembly evaluation demonstrated a decrease in reactivity when compared to nominal, channeled storage conditions, the remaining normal configuration studies are performed with channeled bundles. This is applicable to both units.

5.4.2 Results The results of the study are provided in Table 11 and Table 12. This information demonstrates that none of the normal configurations analyzed increase the system reactivity by a statistically significant amount over the nominal loading pattern. The in-rack k associated with this nominal combination of conditions is 0.87195 for Unit 1 and 0.91664 for Unit 2 and are both hereafter referred to as kNormal. This configuration will be used for all abnormal and tolerance studies that are performed on an infinite basis. Any small, positive reactivity differences from this nominal condition are included in the calculation of the system bias in Section 5.5.

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NEDO-33931 Revision 1 Non-Proprietary Information Table 11 - Unit 1 In-Rack k Results - Normal Configurations MCNP-05P Term Configuration In-Rack k Uncertainty (1)

Base Nominal - centered, channeled, ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) 0.87195 ((` ` ` ` ` ` `

kN1 Non-channeled assemblies 0.86892 ```````

kN3a ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` 0.87221* ```````

kN3b ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) 0.87159 ```````

Moderator temperature increase to 126oC with 20% void kN4a 0.82811 ```````

(=0.7508 g/cc) kN4b Moderator temperature decrease to 4oC (=1.0 g/cc) 0.87216* ` ` ` ` ` ` ` ` ` ` ` ))

Largest positive reactivity increase from nominal case for each term is included in roll-up of kBias.

Table 12 - Unit 2 In-Rack k Results - Normal Configurations MCNP-05P Term Configuration In-Rack k Uncertainty (1)

Base Nominal - centered, channeled, ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) 0.91664 ((` ` ` ` ` ` `

kN1 Non-channeled assemblies 0.91124 ```````

kN2a Eccentric loading, ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) 0.91628 ```````

kN2b Eccentric loading, ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) 0.91163 ```````

Eccentric loading, ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

kN2c 0.91451 ```````

` ` ))

kN3a ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) 0.91639 ```````

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

kN3b 0.91610 ```````

` ))

Moderator temperature increase to 126oC with 20% void kN4a 0.88423 ```````

(=0.7508 g/cc) kN4b Moderator temperature decrease to 4oC (=1.0 g/cc) 0.91736* ` ` ` ` ` ` ` ` ` ` ` ))

Largest positive reactivity increase from nominal case for each term is included in roll-up of kBias.

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NEDO-33931 Revision 1 Non-Proprietary Information 5.5 Bias Cases 5.5.1 Depletion Bias Cases The following configurations related to the depletion conditions of the stored bundles were explicitly considered, where each description defines a condition all bundles in storage experience over their entire exposure histories. These bound the conditions the bundles actually experience.

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

```````````````````````````````````````````````

``````````````````````````````````````````````````````

`````````````````````````````````````````````

``````````````````````````````````````````````

````````````````````````````````````````````````````````````````````````````````````

```````````````````````````````````

````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

The following potential reactivity effect of changes that occur during depletion are considered:

a. Fuel rod changes (clad creep, fuel densification/swelling)

Clad Creep - ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

``````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

Fuel Pellet Densification - ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

``````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

b. Material dependent grid growth

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

```````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` .` ` ` ` ))

5.5.2 Normal Bias Cases The following bias cases are included for normal conditions. As noted in Tables 11 and 12, (from Section 5.4.2) cases with positive reactivity increases from the nominal cases are included in roll-up of kBias and are therefore included in Table 17 and Table 18.

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NEDO-33931 Revision 1 Non-Proprietary Information

No Boral/inserts on rack periphery There is a possibility that assemblies loaded in storage cells on the sides that will not be surrounded by neutron absorbing Boral panels or inserts. ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

```````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) Results are provided in Table 13 and Table 14. The reactivity increase from this study is included in the final kBias term.

Table 13 - Unit 1 Rack Periphery Study Results MCNP-05P Description keff Uncertainty k (1)

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ``````` ``````` ` ` ` ` ` ))

No Boral panels on rack periphery ((` ` ` ` ` ` ` ``````` ` ` ` ` ` ` ` ` ` ` ` ))

Table 14 - Unit 2 Rack Periphery Study Results MCNP-05P Description keff Uncertainty k (1)

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ``````` ``````` ` ` ` ` ` ))

No Inserts on rack periphery ((` ` ` ` ` ` ` ``````` ` ` ` ` ` ` ` ` ` ` ` ))

Missing rack insert A missing insert from the 10x10 infinite array was analyzed to cover the periodic removal of an insert for inspection or an insert being accidently removed during fuel movement.

The relative reactivity increase from this condition is included in the bias table in Table 18.

This scenario is applicable to Unit 2 only.

5.5.3 Abnormal/Accident Bias Cases Additionally, perturbations of the normal spent fuel rack configurations were considered for credible accident scenarios. The scenarios considered are presented in the bulleted lists that follow, which explanations of the abnormal condition provided below each listing of similar configurations.

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NEDO-33931 Revision 1 Non-Proprietary Information The most limiting of these abnormal/accident conditions is included in the final kBias terms in Tables 17 and 18.

Dropped/damaged fuel The dropped/damaged fuel scenario ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

```````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) The relative reactivity increase from this abnormal condition is included in Table 17 and Table 18.

Abnormal positioning of fuel assembly outside the fuel storage rack Misplaced bundles outside the rack is analyzed on an edge of the rack ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

```````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) The calculation was then reperformed several times with misplaced bundles outside of the rack wall ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) spanning the width of a rack cell. Further misplaced bundles positions were subsequently analyzed at various distances from the rack again moving the misplaced bundles laterally across the width of a rack cell ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) The most limiting result generated is used to determine the k from the base case eigenvalue as shown in Table 15 and Table 16. The ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) is depicted in Figure 12.

Table 15 - Unit 1 Results for Misplaced Bundles MCNP-05P Description keff Uncertainty k (1)

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ``````` ``````` ` ` ` ` ` ))

Misplaced bundles, in the most limiting location ((` ` ` ` ` ` ` ``````` ` ` ` ` ` ` ` ` ` ` ` ))

Table 16 - Unit 2 Results for Misplaced Bundles MCNP-05P Description keff Uncertainty k (1)

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ``````` ``````` ` ` ` ` ` ))

Misplaced bundles, in the most limiting location ((` ` ` ` ` ` ` ``````` ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information

((

` ` ` ` ` ))

Figure 12 - Finite Misplaced Bundle Model Example The following abnormal configurations are also considered bounded, with the justification provided:

Dropped bundle on rack For a drop on the rack, the fuel assembly will come to rest horizontally on top of the rack with a minimum separation distance from the fuel in the rack of more than 12 inches. At this separation distance, the fissile material will be separated by enough neutron mean free paths to preclude neutron interactions that increase keff, and the overall effect on reactivity will be insignificant.

Rack sliding due to seismic event which causes water gap between racks to close The racks modeled in this analysis are infinite in extent with no inter-module water gaps.

This essentially assumes all racks are close-fitting and bounds possible reactivity effects of rack sliding.

Loss of spent fuel pool cooling Normal sensitivity analysis results demonstrate that system reactivity decreases as moderator density decreases and pool temperature increases; therefore, reactivity effects of loss of spent fuel pool cooling are bounded by the nominal reactivity results.

Storage of fuel adjacent to the Unit 2 defective fuel rack

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

```````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information 5.5.4 Results The results of the bias studies are provided in Table 17 and Table 18. The k term in the tables represent the difference between the system reactivity with the specified bias case and kNormal. kB6 is the MCNP-05P bias from Section 3.4. The total contribution from these independent conditions to the kmax(95/95) of the spent fuel rack is calculated using Equation 1. In this equation, each k value must be both positive and the largest for its respective term to be considered.

n k Bias = k Bi i =1 (1)

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NEDO-33931 Revision 1 Non-Proprietary Information Table 17 - Unit 1 Spent Fuel Storage Rack Bias Summary MCNP-05P k In-Rack Term Description Uncertainty k* Uncertainty keff (1) (2)+

kB1 ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` 0.85889 ((` ` ` ` ` ` ` -0.01306 ((`

kB2a ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` 0.87186 ``````` -0.00009 `

``````````````````````````````````````

kB2b ```````

`` 0.87216 ``````` 0.00021 kB3a ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` 0.87270 ``````` 0.00075 ```````

kB3b ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` 0.87139 ``````` -0.00056 `

``````````````````````````````````````

kB4a `

` 0.87188 ``````` -0.00007

``````````````````````````````````````

kB4b `

` ` ` ` ` ` )) 0.87094 ``````` -0.00101 kB5 Depleted with clad creep 0.87211 ` ` ` ` ` ` ` ` ` ` ` )) 0.00016 ` ` ` ` ` ` ` ` ` ` ))

kB6 MCNP-05P bias ((` ` `````` ` ` ` ` ` ))

((` ` ` ` ` ` ` ` ` ` `

kB7 Dropped/damaged fuel 0.87200 0.00005 ((` ` ` ` ` ` ` ` ` ` ` ))

))

kB8 Misplaced assembly side of pool ((` ` ``````` ```````

kB9 No Boral panels on rack periphery ` ` ``````` ` ` ` ` ` ` ` ` ` ` ` ))

kN3b^ ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) 0.87221 ((` ` ` ` ` ` ` 0.00026 ((` ` ` ` ` ` `

Moderator temperature decrease to kN4b^ 0.87216 ` ` ` ` ` ` ` ` ` ` )) 0.00021 ` ` ` ` ` ` ` ` ` ` ` ))

4°C kBias ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

For conservatism, only positive values that are the largest for their respective term are considered.

((` ` `` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

^

From Table 11.

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NEDO-33931 Revision 1 Non-Proprietary Information Table 18 - Unit 2 Spent Fuel Storage Rack Bias Summary MCNP-05P k In-Rack Term Description Uncertainty k* Uncertainty keff (1) (2)+

kB1 ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` 0.90304 ((` ` ` ` ` ` ` -0.01360 ((`

kB2a ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` 0.91670 ``````` 0.00006 `

```````````````````````````````````````

kB2b 0.91696 ``````` 0.00032 ```````

`

kB3a ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` 0.91772 ``````` 0.00108 ```````

kB3b ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` 0.91627 ``````` -0.00037 `

kB4a ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` 0.91706 ``````` 0.00042 ```````

```````````````````````````````````````

kB4b 0.91650 ``````` -0.00014 `

`

kB5 Depleted with clad creep 0.91694 ` ` ` ` ` ` ` ` ` ` ` )) 0.00030 ` ` ` ` ` ` ` ` ` ` ` ))

kB6 MCNP-05P bias ((` ` ``````` ` ` ` ` ` ))

kB7 Dropped/damaged fuel 0.91643 ((` ` ` ` ` ` ` ` ` ` ` )) -0.00021 ((` ` ` ` ` ` ` ` ` ` ` ))

kB8 Misplaced assembly side of pool ((` ` ``````` ```````

kB9 No inserts on rack periphery ` ` ``````` ` ` ` ` ` ` ` ` ` ` ` ))

kB10 Missing rack insert 0.92003 ((` ` ` ` ` ` ` 0.00339 ((` ` ` ` ` ` `

kN4b^ Moderator temperature decrease to 4°C 0.91736 ` ` ` ` ` ` ` ` ` ` ` )) 0.00072 ` ` ` ` ` ` ` ` ` ` ` ))

kBias ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

For conservatism, only positive values that are the largest for their respective term are considered.

((` ` ` ` ` ` ` ` ` ` ` ` `` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

^

From Table 12.

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NEDO-33931 Revision 1 Non-Proprietary Information 5.6 Uncertainties 5.6.1 Tolerance Analytic Models The following tolerance study configurations were explicitly considered for the spent fuel rack:

Fuel enrichment increases by ((` ` ` ` ` ` ` ` ` ` ` ` ` ` )) 235U

Fuel pellet density increased by ((` ` ` ` ` ` ` ` ` )) of nominal value

Gadolinia concentration decreased by ((` ` ` ` ` ` ` ` ` ` ` ` ))

Rod cladding thickness increased by ((` ` ` ` ` ` ` )) and rod cladding outer diameter increase by

((` ` ` ` ` ` ))

Rod cladding thickness decreased by ((` ` ` ` ` ` ` )) and rod cladding outer diameter decrease by

((` ` ` ` ` ` ))

Channel thickness increase by ((` ` ` ` ` ` ))

Channel thickness decrease by ((` ` ` ` ` ` ))

Fuel pellet outer diameter increase by ((` ` ` ` ` ` ` ` ` ))

Fuel pellet outer diameter decrease by ((` ` ` ` ` ` ` ` ` ))

Fuel rod pin pitch increase by ((` ` ` ` ` ` ` ` ))

Fuel rod pin pitch decrease by ((` ` ` ` ` ` ` ` ))

Rack wall thickness increase by 0.004 inches (Unit 1), 0.005 inches (Unit 2)

Rack wall thickness decrease by 0.004 inches (Unit 1), 0.005 inches (Unit 2)

Rack pitch increase by 0.03 inches (Unit 1), 0.04 inches (Unit 2)

Rack pitch decrease by 0.03 inches (Unit 1), 0.04 inches (Unit 2)

Boral panel thickness decrease by 0.007 inches (Unit 1)

Rack insert thickness decrease by 0.005 inches (Unit 2)

Boral panel width decrease by (( ))

Rack insert width increase by (( ))

Rack insert width decrease by (( ))

Rack insert thickness increase by 0.005 inches (Unit 2)

Neutron absorber sheathing thickness increase by (( ))

Neutron absorber sheathing thickness decrease by (( ))

All the tolerances used in these analyses are at least 2 design limits. The models developed for these studies were all based on the normal configuration presented in Section 5.4.

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NEDO-33931 Revision 1 Non-Proprietary Information 5.6.2 Uncertainty Results The results of the tolerance studies and uncertainties are provided in Table 19 and Table 20 for Units 1 and 2 respectively. The values are summed using Equation 2 which is adopted from NEI 12-16 (Reference 3).

The kT term in the tables represent the difference between the system reactivity with the specified tolerance perturbation and kNormal. In Equation 2, a kTi value must be both positive and the largest for its respective term to be considered.

The kU terms in the tables represent the uncertainty contributions to kmax(95/95) of the spent fuel rack and from the problem and code specific uncertainties which are combined with the tolerance contributions (kTi) using Equation 2.

(2)

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NEDO-33931 Revision 1 Non-Proprietary Information Table 19 - Unit 1 Spent Fuel Storage Rack Tolerance and Uncertainty k Results MCNP-05P k Term Description In-Rack keff Uncertainty k* Uncertainty (1) (2)+

kT1 Fuel enrichment increase 0.87490 ((` ` ` ` ` ` ` 0.00295 ((` ` ` ` ` ` `

kT2 Fuel pellet density increase 0.87269 ``````` 0.00074 ```````

kT3 Gadolinia wt.% decrease 0.87789 ``````` 0.00594 ```````

kT4a Rod clad thickness/outer diameter increase 0.86550 ``````` -0.00645 `

kT4b Rod clad thickness/outer diameter decrease 0.87826 ``````` 0.00631 ```````

kT5a Channel thickness increase 0.87240 ``````` 0.00045 ```````

kT5b Channel thickness decrease 0.87221 ``````` 0.00026 `

kT6a Pellet outer diameter increase 0.87149 ``````` -0.00046 `

kT6b Pellet outer diameter decrease 0.87202 ``````` 0.00007 ```````

kT7a Fuel rod pin pitch increase 0.87367 ``````` 0.00172 ```````

kT7b Fuel rod pin pitch decrease 0.87032 ``````` -0.00163 `

kT8a Rack wall thickness increase 0.87196 ``````` 0.00001 `

kT8b Rack wall thickness decrease 0.87226 ``````` 0.00031 ```````

kT9a Rack pitch increase 0.87042 ``````` -0.00153 `

kT9b Rack pitch decrease 0.87334 ``````` 0.00139 ```````

kT11 Boral panel thickness decrease 0.87176 ``````` -0.00019 `

kT12 Boral panel width decrease 0.87382 ``````` 0.00187 ```````

kT14a Sheathing thickness increase 0.87215 ``````` 0.00020 ```````

kT14b Sheathing thickness decrease 0.87177 ` ` ` ` ` ` ` ` ` ` ` )) -0.00018 ` ` ` ` ` ))

Critical benchmark bias uncertainty (95/95) kU1 ((` ` ``````` `

(MCNP-05P versus critical experiments) kU2 TGBLA06 eigenvalue uncertainty (95/95) ` ` ``````` ` ` ` ` ` ))

Uncertainty on kNormal kU3 - ((` ``````` `

(2 x 1 value for base term in Table 11) kU4 Uncertainty of k bias contributors (2) - ` ``````` `

kU5 Uncertainty of k tolerance contributors (2) - ` ``````` `

kU6 Uncertainty in fuel depletion - ` ``````` ` ` ` ` ` ))

kUncertainty ((` ` ` ` ` ` ` ` ` ` ` ` ))

For conservatism, only positive values that are the largest for their respective term are considered.

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))`

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NEDO-33931 Revision 1 Non-Proprietary Information Table 20 - Unit 2 Spent Fuel Storage Rack Tolerance and Uncertainty k Results MCNP-05P k Term Description In-Rack keff Uncertainty k* Uncertainty (1) (2)+

kT1 Fuel enrichment increase 0.91920 ((` ` ` ` ` ` ` 0.00256 ((` ` ` ` ` ` `

kT2 Fuel pellet density increase 0.91688 ``````` 0.00024 ```````

kT3 Gadolinia wt.% decrease 0.92219 ``````` 0.00555 ```````

kT4a Rod clad thickness/outer diameter increase 0.91056 ``````` -0.00608 `

kT4b Rod clad thickness/outer diameter decrease 0.92179 ``````` 0.00515 ```````

kT5a Channel thickness increase 0.91690 ``````` 0.00026 ```````

kT5b Channel thickness decrease 0.91637 ``````` -0.00027 `

kT6a Pellet outer diameter increase 0.91697 ``````` 0.00033 ```````

kT6b Pellet outer diameter decrease 0.91636 ``````` -0.00028 `

kT7a Fuel rod pin pitch increase 0.91845 ``````` 0.00181 ```````

kT7b Fuel rod pin pitch decrease 0.91484 ``````` -0.00180 `

kT8a Rack wall thickness increase 0.91756 ``````` 0.00092 ```````

kT8b Rack wall thickness decrease 0.91538 ``````` -0.00126 `

kT9a Rack pitch increase 0.91010 ``````` -0.00654 `

kT9b Rack pitch decrease 0.92291 ``````` 0.00627 ```````

kT11a Rack insert thickness increase 0.91711 ``````` 0.00047 ```````

kT11b Rack insert thickness decrease 0.91574 ``````` -0.00090 `

kT12a Rack insert width increase 0.91677 ``````` 0.00013 ```````

kT12b Rack insert width decrease 0.91655 ` ` ` ` ` ` ` ` ` ` ` )) -0.00009 ` ` ` ` ` ))

Critical benchmark bias uncertainty (95/95) kU1 ((` ` ``````` `

(MCNP-05P versus critical experiments) kU2 TGBLA06 eigenvalue uncertainty (95/95) ` ` ``````` ` ` ` ` ` ))

Uncertainty on kNormal kU3 - ((` ``````` `

(2 x 1 value for base term in Table 12) kU4 Uncertainty of k bias contributors (2) - ` ``````` `

kU5 Uncertainty of k tolerance contributors (2) - ` ``````` `

kU6 Uncertainty in fuel depletion - ` ``````` ` ` ` ` ` ))

kUncertainty ((` ` ` ` ` ` ` ` ` ` ` ))

For conservatism, only positive values that are the largest for their respective term are considered.

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information 5.7 Maximum Reactivity The maximum reactivity of the spent fuel rack considering all biases, and uncertainties, is calculated using Equation 3. The final values are presented in Table 21 and Table 22.

(3)

Table 21 - Unit 1 Spent Fuel Storage Rack Results Summary Term Value kNormal 0.87195 kBias ((` ` ` ` ` ` `

kUncertainty ` ` ` ` ` ` ` ` ` ` ` ))

kmax(95/95) 0.89232 Table 22 - Unit 2 Spent Fuel Storage Rack Results Summary Term Value kNormal 0.91664 kBias ((` ` ` ` ` ` `

kUncertainty ` ` ` ` ` ` ` ` ` ` ` ))

kmax(95/95) 0.93900

((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

``````````````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information 6.0 INTERFACES BETWEEN UNIT 1 AND UNIT 2 STORAGE POOLS The Unit 1 and Unit 2 storage pools are separated by a transfer canal and pit cask well. The separation distance is more than 12 inches. Therefore, they are neutronically decoupled. At this separation distance, the fissile material will be separated by enough neutron mean free paths to preclude neutron interactions that increase keff.

7.0 CONCLUSION

S The LCS spent fuel racks have been analyzed for the storage of GNF3 fuel using the MCNP-05P Monte Carlo neutron transport program and the k criterion methodology. A maximum SCCG, uncontrolled peak in-core eigenvalue (k) of 1.275 as defined by TGBLA06 is specified as the rack design limit for GNF3 fuel in the spent fuel racks. The analyses resulted in a storage rack maximum k-effective (kmax(95/95)) less than the 10 CFR 50.68 limit of 0.95 for normal and credible abnormal operation with tolerances and computational uncertainties taken into account. Justification for the continued storage of all legacy LCS fuel types is in Appendix B.

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NEDO-33931 Revision 1 Non-Proprietary Information

8.0 REFERENCES

1) "MFN-035-99, S. Richards (NRC) to G. Watford (GE), Amendment 26 to GE Licensing Topical Report NEDE-24011-P-A, "GESTAR II" - Implementing Improved GE Steady State Methods (TAC No. MA6481), November 10, 1999.

2) NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, Section 9.1.1, Criticality Safety of Fresh and Spent Fuel Storage and Handling, US NRC, Revision 3, March 2007. (NRC ADAMS Accession Number ML070570006).

3) NEI 12-16 Guidance for Performing Criticality Analyses of Fuel Storage at Light-Water Reactor Power Plants, Revision 4, September 2019. (NRC ADAMS Accession Number ML19269E069)

4) LA-UR-03-1987, MCNP - A General Monte Carlo N-Particle Transport Code, Version 5, April 2003.

5) NUREG/CR-6698, Guide for Validation of Nuclear Criticality Safety Calculational Methodology, US NRC, January 2001. (NRC ADAMS Accession Number ML050250061).

6) J.R. Taylor, An Introduction to Error Analysis, page 268-271, 2nd Edition, University Science Books, 1997.

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NEDO-33931 Revision 1 Non-Proprietary Information APPENDIX A MCNP-05P CODE VALIDATION Table 23 presents the results of the benchmark calculations described in Section 3.4. Note that it is necessary to make an adjustment to the calculated keff value if the critical experiment being modeled was not at a critical state. This adjustment is done by normalizing the kcalc values to the experimental values, which is valid for small differences in keff. This normalization is reported as knorm and is determined using Equation A-1. The combined uncertainty (t) from the measurement and the calculation is also determined using Equation A-2.

(A-1)

(A-2)

Table 23 MCNP-05P Results for the Benchmark Calculations Benchmark Experimental MCNP-05P MCNP-05P Norm. Combined Expt. Eigenvalue Uncertainty Result Result

Experiment Uncertainty Uncertainty (kexp) (exp) (kcalc) (calc) (knorm) (t)

((` `````````````````` ` ` `````` ``````` ``````` ``````` ````````

` `````````````````` ` ` `````` ``````` ``````` ``````` ````````

` `````````````````` ` ` `````` ``````` `````` ``````` ````````

` `````````````````` ` ` `````` ``````` ``````` ``````` ````````

`` `````````````````` ` ` `````` ``````` `````` ``````` ````````

`` `````````````````` ` ` `````` ``````` ``````` ``````` ````````

`` `````````````````` ` ` `````` ``````` `````` ``````` ````````

`` `````````````````` ` ` `````` ``````` ``````` ``````` ````````

`` `````````````````` ` ` `````` ``````` `````` ``````` ````````

`` `````````````````` `` ` `````` ``````` ``````` ``````` ````````

`` `````````````````` `` ` `````` ``````` `````` ``````` ````````

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NEDO-33931 Revision 1 Non-Proprietary Information Benchmark Experimental MCNP-05P MCNP-05P Norm. Combined Expt. Eigenvalue Uncertainty Result Result

Experiment Uncertainty Uncertainty (kexp) (exp) (kcalc) (calc) (knorm) (t)

`` `````````````````` `` ` `````` ``````` ``````` ``````` ````````

`` `````````````````` ` ` `````` ``````` `````` ``````` ````````

`` `````````````````` ` `````` `````` ````` `````` ```````` ````````

`` `````````````````` ` `````` `````` ``````` ``````` ```````` ````````

`` `````````````````` ` `````` `````` ``````` `````` ```````` ````````

`` `````````````````` ` ` `````` ``````` ``````` ``````` ````````

`` `````````````````` ` `````` `````` ``````` `````` ```````` ````````

`` `````````````````` ` ` `````` ``````` ``````` ``````` ````````

`` `````````````````` ` `````` `````` ``````` `````` ``````` ````````

`` `````````````````` `` `````` `````` `````` `````` ```````` ````````

`` `````````````````` `` `````` `````` ``````` ``````` ```````` ````````

`` `````````````````` `` ` `````` ``````` ``````` ``````` ````````

`` `````````````````` `` `````` `````` ``````` `````` ``````` ````````

`` `````````````````` `` `````` `````` ``````` `````` ```````` ````````

`` `````````````````` `` `````` `````` `````` ``````` ```````` ````````

`` `````````````````` `` `````` `````` ``````` ``````` ```````` ````````

`` ````````````````` ` ` `````` ``````` ``````` ``````` ````````

`` ````````````````` ` ` `````` `````` `````` `````` ````````

`` ````````````````` ` ` `````` ``````` `````` ``````` ````````

`` ```````````````` ` ` `````` ``````` ``````` ``````` ````````

`` ``````````````` ` ` `````` `````` `````` `````` ````````

`` ``````````````` ` ` `````` ``````` `````` ``````` ````````

`` ``````````````` ` ` `````` ``````` ``````` ``````` ````````

`` ````````````````````````` ` ` `````` ``````` ``````` ``````` ````````

`` ```````````````````````` ` ` `````` ``````` ``````` ``````` ````````

`` ```````````````````````` ` ` `````` ``````` `````` ``````` ````````

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NEDO-33931 Revision 1 Non-Proprietary Information Benchmark Experimental MCNP-05P MCNP-05P Norm. Combined Expt. Eigenvalue Uncertainty Result Result

Experiment Uncertainty Uncertainty (kexp) (exp) (kcalc) (calc) (knorm) (t)

`` ```````````````````` ` ` `````` ``````` ``````` ``````` ````````

`` ```````````````````` ` ` `````` ``````` `````` ``````` ````````

`` ```````````````````` ` ` `````` ``````` ``````` ``````` ````````

`` ```````````````````` ` ` `````` ``````` `````` ``````` ````````

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NEDO-33931 Revision 1 Non-Proprietary Information Benchmark Experimental MCNP-05P MCNP-05P Norm. Combined Expt. Eigenvalue Uncertainty Result Result

Experiment Uncertainty Uncertainty (kexp) (exp) (kcalc) (calc) (knorm) (t)

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NEDO-33931 Revision 1 Non-Proprietary Information Benchmark Experimental MCNP-05P MCNP-05P Norm. Combined Expt. Eigenvalue Uncertainty Result Result

Experiment Uncertainty Uncertainty (kexp) (exp) (kcalc) (calc) (knorm) (t)

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NEDO-33931 Revision 1 Non-Proprietary Information Benchmark Experimental MCNP-05P MCNP-05P Norm. Combined Expt. Eigenvalue Uncertainty Result Result

Experiment Uncertainty Uncertainty (kexp) (exp) (kcalc) (calc) (knorm) (t)

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A.1 Trend Analysis To determine if any trend is evident in this pool of experiments, the parameters listed in Table 24 were considered as independent variables.

Table 24 - Trending Parameters Energy of the Average Lethargy causing Fission (EALF)

Uranium Enrichment (wt.% 235U)

Plutonium Content (wt.% 239Pu)

Atom ratio of hydrogen to fissile material (H/X)

Each parameter was plotted against the knorm results independently for each case that was analyzed.

These plots are provided in Figure 13 through Figure 16. This scatter plot of data was first analyzed by visual inspection to determine if any trends were readily apparent in the data. During this inspection, the axes of the graphs were modified to different scales to allow for a more thorough review. No clear evidence of a trend, linear or otherwise, was observed from this inspection.

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NEDO-33931 Revision 1 Non-Proprietary Information

((

` ` ` ` ` ))

Figure 13 - Scatterplot of knorm versus EALF

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` ` ` ` ` ))

Figure 14 - Scatterplot of knorm versus wt.% 235U Page 46

NEDO-33931 Revision 1 Non-Proprietary Information

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` ` ` ` ` ))

Figure 15 - Scatterplot of knorm versus wt.% 239Pu

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Figure 16 - Scatterplot of knorm versus H/X Page 47

NEDO-33931 Revision 1 Non-Proprietary Information To further check for trends in the data, a linear regression was performed. The linear regression fitted equation is in the form y(x)= a +bx, where y is the dependent variable (knorm) and x is any of the predictor variables from Table 24. Unweighted knorm values were used in this evaluation, although it is noted that, due to the very similar values reported in Table 23, using weighted values would produce very similar results. This regression was performed using the built-in regression analysis tool in Excel. The fitted lines are included in Figure 13 through Figure 16. Again, it is noted through visual inspection that the trends do not appear to exhibit a strong correlation to the data. A useful tool to validate this claim is the linear correlation coefficient. This is a quantitative measure of the degree to which a linear relation exists between two variables. It is often expressed as the square term, r2, and can be calculated directly using built in functions in Excel. The closer r2 gets to the value of 1, the better the fit of data is expected to be to the linear equation. Results from this linear regression evaluation are summarized in Table 25.

A final method to test for goodness of fit is the chi squared test (2). This method is explained in detail in Reference 6. In general, it can be stated that 2 is an indicator of the agreement between the observed (calculated) and expected (fitted) values for some variable. For linear goodness of fit testing using this method, Equation A-3 is utilized, where the expected value of f(xi) corresponds to the linear fitted equation for the trending parameter, xi.

(A-3)

A more convenient way to report this result is the reduced chi squared value, which is denoted as and is defined by Equation A-4, where d is the degrees of freedom for the evaluation.

(A-4)

If a value of order one or less is obtained for this equation, then there is no reason to doubt the expected (fitted) distribution is reasonable; however, if the value is much larger than one, the expected distribution is unlikely to be a good fit. Results for each trending parameter are summarized in Table 25.

Table 25 - Trending Results Summary Trend Valid Intercept Slope r2 Parameter Trend EALF ((` ` ` ` ` ` ` `````````` ``````` ``` No wt.% 235U ``````` `````````` ``````` ``` No wt.% 239Pu ``````` ``````````` ``````` ``` No H/X ``````` ``````````` ``````` ` ` ` ` ` ` ` )) No The results in Table 25 clearly demonstrate that there are no statistically significant or valid trends of knorm with any of the trending parameters.

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NEDO-33931 Revision 1 Non-Proprietary Information A.2 Bias and Bias Uncertainty Calculation - Single Sided Tolerance Limit As no trends are apparent in the critical experiment results, a weighted single-sided tolerance limit methodology is utilized to establish the bias and bias uncertainty for this AOA and code package combination. Use of this method requires the critical experiment results to have a normal statistical distribution. This was verified using the Anderson-Darling normality test. A graphical image of the results for this normality test, including the p-value for the distribution, is provided in Figure 17.

Because the reported p-value is greater than 0.05, it is confirmed that the data fits a normal distribution, and the single sided tolerance limit methodology is confirmed to be applicable.

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Figure 17 - Normality Test of knorm Results When using this method, the weighted bias and bias uncertainty are calculated using the following equations:

(A-5)

(A-6)

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NEDO-33931 Revision 1 Non-Proprietary Information n

knormi i =1 t2 k norm = n 1

i =1 2

t (A-7)

SP = s2 + 2 (A-8) n 2 = n 1

i =1 2

t (A-9) 2

§ 1 *n 1

¨ ¸ 2 (k norm i k norm )

1 n 1 n i =1 t2 (A-10)

Where:

knorm = Average weighted knorm S P = Pooled standard deviation s 2 = Variance about the mean 2 = Average total variance U = one-sided tolerance factor for n data points at (95/95 confidence/probability level) n = number of data points (((` ` ` ` ` ` ` ` )))

Table 26 summarizes the results of these calculations.

Table 26 Bias and Bias Uncertainty for MCNP-05P with ENDF/B-VII Bias (weighted) ((` ` ` ` ` ` `

Bias Uncertainty (95/95 level) ```````

Variance About the Mean ``````````

Average Total Variance ``````````

Pooled Standard Deviation (1) ``````````

One-Sided Tolerance Factor ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information Using the average weighted bias and pooled standard deviation; the upper one-sided 95/95-tolerance limit (bias uncertainty) was calculated for use in criticality calculations, in accordance with NUREG-6698 guidance. As seen in Figure 17, ((` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` `

``````````````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) As shown in Table 26, the MCNP-05P bias uncertainty (95/95) ((` `

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` )) Table 27 summarizes the recommended bias and bias uncertainty to be used in criticality calculations.

Table 27 - Recommended Bias and Bias Uncertainty in Criticality Analyses for MCNP-05P with ENDF/B-VII Bias ((` ` `

Bias Uncertainty (95/95) ` ` ` ` ` ` ` ` ` ` ` ))

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NEDO-33931 Revision 1 Non-Proprietary Information APPENDIX B LEGACY FUEL STORAGE JUSTIFICATION This appendix provides justification for the storage of legacy GNF and legacy non-GNF fuel designs stored in the LCS Units 1 and 2 spent fuels.

B.1 Legacy Non-GNF Fuel Justification The legacy non-GNF lattice previously determined to have the highest (most limiting) in-rack eigenvalue in the LCS Units 1 and 2 spent fuel pools is modeled using the GNF codes and methods outlined in the main body of this report. The resulting peak nominal in-rack reactivity for the limiting non-GNF lattice is compared to the nominal in-rack reactivity for the GNF3 design basis lattice.

The non-GNF lattice previously determined by LCS to have the highest nominal in-rack reactivity is lattice A10T-4444L-12G40 which is in a 10x10 ATRIUM-10 fuel bundle. Because the Unit 2 rack model in the main analysis resulted in more limiting in-rack reactivities compared to those for Unit 1, the Unit 2 racks, which credit absorber in the rack inserts without credit for the Boraflex, is used for this study (as described in Section 5.1.2).

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``````````````````````````````````````````````````````````````````````````````````````````````````

` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ))` `

Consistent with the analysis in the main body of this report, the criticality calculation is performed using MCNP-05P at its cold, in-core, peak reactivity statepoint.

As shown in Table 28, the in-rack nominal reactivity of the legacy A10T-4444L-12G40 lattice is bounded by the GNF3 design basis lattice determined in this analysis. Thus, the limiting legacy non-GNF lattice at LCS is covered by the design basis lattice determined in Section 5.3.

Table 28 - Summary Non-GNF Fuel k Compared to GNF3 Design Basis Region In-Rack Nominal Reactivity A10T-4444L-12G40 Lattice with LCS Unit 2 Racks 0.91332 GNF3 Design Basis Lattice with LCS Unit 2 Racks 0.91664 The results of this study confirm that all non-GNF legacy fuel bundles are safe for storage in LCS Units 1 and 2 spent fuel pools.

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NEDO-33931 Revision 1 Non-Proprietary Information B.2 Legacy GNF Fuel Justification Exposure dependent, maximum, uncontrolled in-core k results for each GNF fuel assembly in the LCS spent fuel pool are confirmed to be less than 1.275. The in-core k values have been calculated using the process for validating that specific assembly designs are acceptable for storage in the LCS fuel storage racks, as outlined in Section 3.5. The margin to safety was also confirmed to exist in the storage rack by analyzing the peak reactivity legacy fuel lattice of all GNF product lines in the LCS spent fuel pool and core under normal conditions of storage, as outlined in Section 5.4. The GNF lattice with the highest in-core reactivity value is presented in Table 29. This information demonstrates that all fuel assemblies currently in the LCS spent fuel pool have considerable margin to the reactivity of the GNF3 design basis bundle used in this analysis. Any GNF3 bundles in the LCS core or spent fuel pool are covered by the design basis bundle study in Section 5.3.

Because the GNF3 design basis bundle with an in-core k value of 1.275 was shown to be below the 10 CFR 50.68 0.95 in-rack k-effective limit when analyzed in the storage racks, and because the legacy GNF fuel types are less reactive than this design basis bundle both in-core and in-rack, it is confirmed that all legacy fuel bundles are safe for storage in the LCS spent fuel pools.

Table 29 - Limiting Cold As-Designed Eigenvalue of all GNF Bundles at LaSalle Bundle Bundle Name In-Core k

((` ` ` ` `````````````````````````````````` ` ` ` ` ` ` ` ` ` ` ))

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v t e Letter Sequence Supplement
EPID:L-2021-LLA-0124, Order (Granting Motion to Extend Hearing Requests Deadline) (Approved, Closed)
Initiation Request, Request, Request, Request, Request, Request, Request, Request, Request, Request Acceptance Supplement Administration Withholding Request Acceptance, Withholding Request Acceptance Meeting, Meeting Questions 6 May 2022 18 May 2022 Answers 17 June 2022 12 October 2022 Results Approval, Approval Other: ML22214A004
MONTHYEAR2022-11-03 [Table View]

RS-21-115, Supplemental Information for License Amendment Request Regarding New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies, with Proposed Changes to Technical Specifications 4.3.1 and 5.6.5

Text

Subject:

References:

1.0 INTRODUCTION

7.0 CONCLUSION

8.0 REFERENCES

1.0 INTRODUCTION

7.0 CONCLUSION

8.0 REFERENCES

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