ML110380092

Areva Np Inc. Technical Report, Document No. ANP-2858NP-003, Palisades SFP Region 1 Criticality Evaluation with Burnup Credit.

ML110380092
Person / Time
Site:	Palisades
Issue date:	01/31/2011
From:	AREVA NP
To:	Office of Nuclear Reactor Regulation
References
PNP 2011-002 ANP-2858NP-003
Download: ML110380092 (145)

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ATTACHMENT 6 AREVA NP INC. TECHNICAL REPORT DOCUMENT NO. ANP-2858NP-003 PALISADES SFP REGION 1 CRITICALITY EVALUATION WITH BURNUP CREDIT NON-PROPRIETARY 144 pages follow

A AREVA AREVA NP Inc.

Technical Report Document No.: ANP - 2858NP - 003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Page 1

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Record of Revision Revision Pages/Sections/

No. Paragraphs Changed Brief Description I Change Authorization 000 All Original Release 001 Re-issue complete document Incorporated Entergy comments 002 Re-issue complete document Incorporates voids replacing Carborundum absorber material, more conservative swelling model, new AREVA (proprietary) burnup credit methodology, and Regions I D and IE with 3-of-4 and 4-of-4 loading configurations, respectively.

003 Re-issue complete document Incorporates Entergy comments.

t I t I Page 2

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table of Contents Page RECORD OF REVISION .......................................................................................................................... 2 LIST O F TABLES ..................................................................................................................................... 6 LIST O F FIGURES ................................................................................................................................... 9 1.0 EXECUTIVE SUM MARY ....................................................... I............................................... 11

2.0 INTRODUCTION

...................... ................................................................................................... 11 3.0 ANALYTICAL M ETHODS ........................................................................................................ 13 3.1 Com puter Program s and Standards ............................................................................ 13 3.2 Analytical Requirements and Assum ptions ................................................................ 13 3.3 Com putational Models and M ethods .......................................................................... 15 3.3.1 Bounding Fuel Assem bly Description ....................................................... 15 3.3.2 Region 1 Rack Data ................................................................................... 15 3.3.3 Material Specification ................................................................................. 19 3.3.4 Models for Degradation of Carborundum Plates .................. 19 3.3.5 Swelling M odel .......................................................................................... 19 3.4 Analytical Model Conservatisms ................................................................................ 22 3.5 Tolerances, Penalties, Biases, and Uncertainties ....................................................... 23 3.5.1 Method Discussion of Tolerances, Biases, and Uncertainties ................... 23 3.5.2 System and Tolerance Effects .................................................................. 24 3.5.3 System and Tolerance Results ................................................................ 25 3.5.4 Sum mary of Bias and Uncertainty Values ............................................... 26 4.0 RACK ANALYSIS ........................................................................................................................ 28 4.1 Region 1A (2-of-4 Configuration) ................................................................................ 29 4.1.1 M isload Conditions ................................................................................... 29 4.1.2 Conservatisms .......................................................................................... 30 4.2 Region 1B (3-of-4 Configuration) ................................................................................ 30 4.2.1 M isload Conditions ................................................................................... 31 4.2.2 Conservatisms .......................................................................................... 31 4.3 Region 1C (4-of-4 Configuration) .............................................................................. 32 4.3.1 M isload Conditions ................................................................................... 33 Page 3

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table of Contents (continued)

Page 4.3.2 Conservatisms .......................................................................................... 33 4.4 Region 1 D (3-of-4 Configuration) .............................................................................. 33 4.4.1 Misload Conditions ................................................................................... 34 4.4.2 Conservatisms .......................................................................................... 35 4.5 Region 1 E (4-of-4 Configuration) ................................................................................ 35 4.5.1 Misload Conditions .................................................................................. 36 4.5.2 Conservatisms .......................................................................................... 36 4.6 Non-Fuel Bearing Components (NFBC) ..................................................................... 37 4.6.1 Misload Conditions ................................................................................... 38 4.7 Rack Interactions ........................................................................................................ 38 4.7.1 Regions 1A, 1B, and 1C Interaction Effects Results .................................. 39 4.7.2 Region 1 D and 1 E Interaction Effects Results ......................................... 41 4.7.3 Regions 1B and IC, 1D and 1E, with Region 2 Interaction Effects Results .. 44 5.0

SUMMARY

AND CONCLUSIONS .......................................................................................... 45 6.0 LICENSING REQUIREMENTS ............................................................................................... 45 7 .0 R EF ER ENC E S ............................................................................................................................ 48 APPENDIX A : KENO-V.A BIAS AND BIAS UNCERTAINTY ............................................................ 50 A.1 Statistical Method for Determining the Code Bias ..................................................... 50 A.2 Area of Applicability Required for the Benchmark Experiments .................................. 52 A.3 Description of the Criticality Experiments Selected ..................................................... 53 A.4 Results of Calculations with SCALE 4.4a ................................................................... 56 A.5 Trending Analysis ........................................................................................................ 58 A.6 Bias and Bias Uncertainty .......................................................................................... 68 A.7 Effect of Removal of the 11 MOX Benchmarks ......................................................... 69 A.8 Area of Applicability for the Benchmark Experiments ................................................ 71 A.9 Bias Summary and Conclusions ................................................................................ 72 A.10 Additional Analyses ................................................................................................... 73 A.1 1 Description of the HTC and Fission Product Experiments ......................................... 75 A.12 Area of Applicability ................................................................................................... 83 Page 4

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table of Contents (continued)

Page A.13 Results of Calculations with SCALE 4.4a ................................................................... 83 A.14 Trending Analysis and Lower Tolerance Band ............................................................ 91 A.15 Normality Evaluation and Lower Tolerance Limit ....................................................... 96 A.16 Nonparametric Statistical Evaluation .......................................................................... 99 A.17 Effect of Removing HTC Phase 2 and Phase 4 Cases ................................................. 100 A.18 Establishing the Bias and Bias Uncertainty ................................................................... 105 A.19 Results and Conclusions ............................................................................................... 106 APPENDIX B: CASMO CALCULATIONS FOR BURNUP .................................................................. 107 B.1 BUC Calculational Method ............................................................................................ 108 B.2 Legacy Fuel Storage ..................................................................................................... 115 APPENDIX C : KENO.V-A TOLERANCE CALCULATIONS ............................................................... 116 C.1 System Bias (Aksys and osys) .......................................................................................... 116 0

C.2 Statistical Tolerance Studies for Akto, and toj ................................................................ 132 APPENDIX D: SPACER GRID, FUEL ROD PITCH, GUIDE BAR, AND GEOMETRY CHANGES DURING FUEL GROWTH EFFECTS ........................................................................... 135 D .1 S pa ce r G rids ................................................................................................................. 135 D.2 Fuel Rod Pitch Tolerance .............................................................................................. 137 D .3 G u id e Ba rs .................................................................................................................... 13 7 D.4 Geometry Changes during Rod Growth ........................................................................ 139 APPENDIX E: EVALUATION OF CASMO3 FISSION PRODUCT UNCERTAINTY ............................ 140 E .1 Intro d u ctio n .................................................................................................................... 14 0 E.2 Method of Derivation ..................................................................................................... 140 E.3 Example Calculation ...................................................................................................... 142 E.4 Overall Uncertainty of 18 CASMO3 Fission Products ................................................... 144 Page 5

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit List of Tables Page TABLE 3-1: BATCH Xl DIMENSIONS AND TOLERANCES ........................................................... 15 TABLE 3-2: DIMENSIONS OF PALISADES REGION 1 RACKS ...................................................... 16 TABLE 3-3: 'C' NOMINAL RACK WITH BIAS/UNCERTAINTIES .................................................... 25 TABLE 3-4: 'E' NOMINAL RACK 4-OF-4 WITH BIAS/UNCERTAINTIES ....................................... 26 TABLE 3-5: K9 5195 DETERMINATION BASED UPON CALCULATED BIAS/UNCERTAINTY ........... 26 TABLE 3-6: 5% DEPLETION REACTIVITY UNCERTAINTY PENALTY .......................................... 27 TABLE 3-7: FISSION PRODUCT WORTH UNCERTAINTY PENALTY .......................................... 27 TABLE 4-1: REGION 1A K95/ 95 DETERMINATION FOR BORON DILUTION ................................... 29 TABLE 4-2: REGION 1A K95/ 95 DETERMINATION FOR MISLOAD CONDITIONS ......................... 30 TABLE 4-3: REGION 1B (3-OF-4 LOADING) REQUIREMENTS .................................................... 30 TABLE 4-4: REGION 1B K95/95 DETERMINATION FOR BORON DILUTION ................................... 31 TABLE 4-5: REGION 1B K95/95 DETERMINATION FOR MISLOAD CONDITIONS .......................... 31 TABLE 4-6: REGION 1C (4-OF-4 LOADING) REQUIREMENTS ..................................................... 32 TABLE 4-7: REGION 1C K95/95 DETERMINATION FOR BORON DILUTION ................................... 32 TABLE 4-8: REGION 1C K95/95 DETERMINATION FOR MISLOAD CONDITIONS .......................... 33 TABLE 4-9: REGION 1D (3-OF-4 LOADING) REQUIREMENTS ..................................................... 34 TABLE 4-10: REGION 1D K95 /95 DETERMINATION FOR BORON DILUTION ................................. 34 TABLE 4-11: REGION 1D K95 /95 DETERMINATION FOR MISLOAD CONDITIONS ....................... 35 TABLE 4-12: REGION 1E (4-OF-4 LOADING) REQUIREMENTS .................................................. 35 TABLE 4-13: REGION 1E K95/95 DETERMINATION FOR BORON DILUTION ................................. 36 TABLE 4-14: REGION 1 E K95195 DETERMINATION FOR MISLOAD CONDITIONS ......................... 36 TABLE 4-15: NFBC REACTIVITY EVALUATION FOR 3-OF-4 BUC RACK ..................................... 37 TABLE 4-16: NFBC REACTIVITY EVALUATION FOR 4-OF-4 BUC RACK ....................... 38 TABLE 4-17: INTERACTION RESULTS FOR REGIONS 1A, 1B, AND 1C RACKS ......................... 41 TABLE 4-18: INTERACTION RESULTS FOR REGIONS 1D AND 1E CONFIGURATION ......... 42 TABLE A-i: RANGE OF VALUES OF KEY PARAMETERS IN SPENT FUEL POOL ..................... 52 TABLE A-2: DESCRIPTIONS OF THE CRITICAL BENCHMARK EXPERIMENTS ......................... 53 TABLE A-3: RESULTS FOR THE SELECTED BENCHMARK EXPERIMENTS ............................... 56 TABLE A-4: TRENDING PARAM ETERS .......................................................................................... 58 Page 6

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit List of Tables (continued)

Page TABLE A-5:

SUMMARY

OF TRENDING ANALYSIS ....................................................................... 61 TABLE A-6: RANGE OF VALUES OF KEY PARAMETERS IN BENCHMARK EXPERIMENTS .......... 72 TABLE A-7: HTC PHASE 1 EXPERIMENTAL PARAMETERS ............................. 75 TABLE A-8: HTC PHASE 2 EXPERIMENTAL PARAMETERS ......................................................... 76 TABLE A-9: HTC PHASE 3 EXPERIMENTAL PARAMETERS ......................................................... 77 TABLE A-10: HTC PHASE 4 EXPERIMENTAL PARAMETERS ....................................................... 78 TABLE A-1 1: SCALE 4.4A RESULTS FOR LEU-MISC-THERM-005 BENCHMARKS ..................... 80 TABLE A-12: LEU-COMP-THERM-050 EXPERIMENTAL PARAMETERS ..................................... 81 TABLE A-13: LEU-COMP-THERM-050 EXPERIMENTAL PARAMETERS ..................................... 82 TABLE A-14: AREA OF APPLIABILITY

SUMMARY

....................................................................... 83 TABLE A-15: CRITICALITY RESULTS FOR THE BENCHMARK EXPERIMENTS .......................... 84 TABLE A-16: RESULTS

SUMMARY

FOR WEIGHTED TRENDING ANALYSIS ............................. 91 TABLE A-17: RESULTS

SUMMARY

FOR NON-WEIGHTED TRENDING ANALYSIS .................... 92 TABLE A-18: RESULTS

SUMMARY

FOR CHI-SQUARED NORMALITY TEST ............................. 97 TABLE A-19: RESULTS

SUMMARY

FOR CHI-SQUARED NORMALITY TEST FOR N=90 .............. 104 TABLE B-i: DEPLETION MODELING CONSIDERATIONS ............................................................... 107 TABLE B-2: AXIAL MODERATOR TEMPERATURE DISTRIBUTION ................................................ 109 TABLE B-3: 25, 30, AND 48 GWD/MTU BURNUP PROFILES - 336.81 CM HEIGHT ....................... 110 TABLE C-1: CASMO-3 NODAL VALUES OF KINF - 48 GWD/MTU AT 4.54% ................................... 117 TABLE C-2: 'C' RACK W ALL BOW ING RESULTS ............................................................................. 118 TABLE C-3: 'E' RACK W ALL BOW ING RESULTS ............................................................................. 119 TABLE C-4: 'C' RACK EFFECT OF RESIDUAL CARBON WITH LOADING PATTERN .................... 120 TABLE C-5: 'C' RACK EFFECT OF RESIDUAL CARBON WITH WALL BOWING ............................ 121 TABLE C-6: 'E' RACK EFFECT OF RESIDUAL CARBON WITH LOADING PATTERN .................... 121 TABLE C-7: 'E' RACK EFFECT OF RESIDUAL CARBON WITH WALL BOWING ............................ 122 TABLE C-8: FABRICATED BOX MODEL DIMENSIONS .................................................................... 123 TABLE C-9: INTER-BOX MODEL DIM ENSIONS ................................................................................ 123 TABLE C-10: 'C' RACK RESULTS FOR PFFC STORAGE ................................................................ 127 TABLE C-11: E-RACK CONTROL BLADE STORAGE RESULTS ...................................................... 130 TABLE C-12: ELEVATOR AND FUEL INSPECTION STATION RESULTS ........................................ 131 Page 7

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit List of Tables (continued)

Page TABLE C-13: RACK 'C' NOMINAL TOLERANCE RESULTS .............................................................. 132 TABLE C-14: RACK 'E' NOMINAL TOLERANCE RESULTS .............................................................. 133 TABLE C-15: 'C' RACK NOMINAL FUEL TOLERANCES ................................................................... 134 TABLE C-16: 'E' RACK NOMINAL FUEL TOLERANCES ................................................................... 134 TABLE D-1: SPAC ER G R ID RESULTS .............................................................................................. 136 TABLE E-1: CASMO3 FISSION PRODUCT AND ACTINIDE CROSS-SECTION UNC E R TA INT IE S ......................................................................................................... 143 TABLE E-2: OVERALL UNCERTAINTY OF 18 CASMO3 FISSION PRODUCTS .............................. 144 Page 8

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit List of Figures Page FIGURE 2-1: PALISADES FUEL STORAGE AREAS ....................................................................... 11 FIGURE 3-1: SKETCH OF MODEL OF 'C' RACK ............................................................................ 17 FIGURE 3-2: SKETCH OF MODEL OF 'E' RACK ............................................................................ 18 FIGURE 3-3: PHOTOGRAPH OF DISTORTED PLATE ................................................................... 20 FIG URE 3-4: FUEL SW ELLING MO DEL ........................................................................................... 21 FIGURE 3-5: 'C' RACK INNER WALL BOWING MODEL ................................................................. 22 FIGURE 4-1: REGION 1B ADJACENT TO REGION 1A ................................................................... 39 FIGURE 4-2: REGION lB ADJACENT TO REGION 1C ................................................................. 40 FIGURE 4-3: REGION 1C ADJACENT TO REGION 1A .................................................................... 40 FIGURE 4-4: ALLOWABLE REGION 1 E CONFIGURATIONS WITH MIXED LOADINGS ............... 43 FIGURE 6-1: 3-OF-4 FUEL LOADING PATTERN FOR REGIONS 1B AND ID ............................... 45 FIGURE 6-2: NINE 2-BY-2 GROUPINGS POSSIBLE WITHIN A 4-BY-4 MATRIX ........................... 46 FIGURE A-I: WEIGHTED TREND OF KEFF VERSUS EALF FOR THE BENCHMARK E XPE R IME NT S ............................................................................................................... 62 FIGURE A-2: WEIGHTED TREND OF KEFF VERSUS ENRICHMENT (2 35U) FOR THE BENCHMARK EXPERIM ENTS .................................................................................. 63 FIGURE A-3: WEIGHTED TREND OF KEFFVERSUS H/X FOR THE BENCHMARK E XPE R IME NT S ............................................................................................................... 63 FIGURE A-4: WEIGHTED TREND OF KEFF VERSUS SOLUBLE BORON FOR THE BENCHMARK EXPERIM ENTS .................................................................................. 64 FIGURE A-5: WEIGHTED TREND OF KEFF VERSUS FISSILE ISOTOPIC CONTENT FOR THE BENCHMARK EXPERIMENTS ......................................................................... 65 FIGURE A-6: NON-WEIGHTED TREND OF KEFF VERSUS FISSILE ISOTOPIC CONTENT FOR THE BENCHMARK EXPERIMENTS ................................................................. 65 FIGURE A-7: PLOT OF STANDARD RESIDUALS WITH EALF AS WEIGHTED TRENDING PA RA ME TE R .................................................................................................................. 66 FIGURE A-8: PLOT OF STANDARD RESIDUALS WITH H/X AS WEIGHTED TRENDING PA RA ME TE R .................................................................................................................. 66 FIGURE A-9: PLOT OF STANDARD RESIDUALS WITH EALF AS NON-WEIGHTED TRENDING PARAM ETER .......................................................................................... 67 FIGURE A-10: PLOT OF STANDARD RESIDUALS WITH FISSILE ISOTOPIC CONTENT AS NON-WEIGHTED TRENDING PARAMETER ............................................................. 67 Page 9

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit List of Figures (continued)

Page FIGURE A-11: NORMAL PROBABILITY PLOT FOR THE NORMALIZED KEFF DATASET .............. 68 FIGURE A-12: NORMAL PROBABILITY PLOT FOR THE NORMALIZED KEFF DATASET W ITH N = 8 9 ................................................................................................................... 70 FIGURE A-13: OVERVIEW OF NORMALIZED KEFF VERSUS PIN PITCH ..................................... 88 FIGURE A-14: OVERVIEW OF NORMALIZED KEFF VERSUS H/X .................................................. 89 FIGURE A-15: OVERVIEW OF NORMALIZED KEFF VERSUS EALF .............................................. 90 FIGURE A-16: TREND OF KNORM VERSUS PIN PITCH WITH LOWER TOLERANCE BAND ...... 93 FIGURE A-17: TREND OF KNORM VERSUS H/X WITH LOWER TOLERANCE BAND ..................... 94 FIGURE A-18: TREND OF KNORM VERSUS EALF WITH LOWER TOLERANCE BAND .................. 95 FIGURE A-19: FREQUENCY DISTRIBUTION COMPARISON FROM CHI-SQUARED TEST ...... 98 FIGURE A-20: NORMALIZED KEFF VERSUS PIN PITCH FOR N=90 ................................................. 101 FIGURE A-21: NORMALIZED KEFF VERSUS MODERATING RATIO FOR N=90 .............................. 102 FIGURE A-22: NORMALIED KEFF VERSUS EALF FOR N=90 ........................................................... 103 FIGURE B-i: BURNUP PROFILES FOR CYCLES 18- 21 FOR BURNUPS 30-34 GWD/MTU ........ 111 FIGURE C-1: SKETCH OF KENO-V.A MODEL AT EDGE OF REGION 2 RACKS ............................ 124 FIGURE C-2: SKETCH OF A PORTION OF THE 'C'-REGION 2 MODEL .......................................... 125 FIGURE C-3: SKETCH OF A PORTION OF THE REGION 1E -REGION 2 MODEL ......................... 126 FIGURE C-4: AS-MODELED CONTROL BLADE IN E-RACK CELL .................................................. 130 FIG URE D-i: SKETC H O F G UIDE BA R ............................................................................................. 138 Page 10

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 1.0 EXECUTIVE

SUMMARY

This report contains the criticality evaluation of the Palisades Spent Fuel Storage Racks for the Region 1 racks that contain Carborundum tm ' plates (Reference [1]) as a poison. There are indications of swelling and of boron loss through attenuation measurements. This evaluation assumes total boron loss from the Carborundum'ý` plates, burnup credit, and a swelling model. The same soluble boron credit that was used in Region 2 is assumed for the Region 1 evaluations. Rack interaction effects are evaluated and found to be acceptable.

2.0 INTRODUCTION

The Palisades Nuclear Plant (PNP) requires a criticality analysis to address the Spent Fuel Storage Racks (SFSR) that are currently designated as Region 1 and contain Carborundum'f boron carbide (B4C) neutron.

absorbing plates that are degraded. These fuel storage locations at Palisades are shown in Figure 2-1.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit This study determines the maximum K-effective (klr) of different regions for the effects associated with fuel storage in the Palisades Region 1 Spent Fuel Storage racks relative to a conservative treatment of the degradation of the Carborundum plates. The five regions are:

1) Region 1A - Region 1 Main Spent Fuel Pool with 2-of-4 checkerboard loading of fuel and empty cells, for fuel having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent with no burnup credit.

2) Region IB - Region 1 Main Spent Fuel Pool with 3-of-4 loading having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent and burnup credit as shown in Table 4-3.

3) Region 1C - Region 1 Main Spent Fuel Pool with 4-of-4 loading having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent and burnup credit as shown in Table 4-6.

4) Region ID - Region 1 North Tilt Pit with 3-of-4 loading having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent and burnup credit as shown in Table 4-9.

5) Region 1E - Region 1 North Tilt Pit with 4-of-4 loading having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent and burnup credit as shown in Table 4-12.

This report includes the burnup credit analysis for Regions IB, IC, ID, and 1E. For all five regions (including Region IA), it defines the acceptable geometries and demonstrates that the reactivity effects of the rack and fuel assembly manufacturing tolerances, the reactivity effects of pool moderator temperature variations, swelling in the poison plates, complete loss of the absorber material contained within the walls, and accident conditions are acceptable. The analysis for Region 2 that was approved in Reference

[2] remains valid.

Criticality results and Licensing Requirements are summarized in Sections 5.0 and 6.0, respectively.

Page 12

A ARE VA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 3.0 ANALYTICAL METHODS The analytical methods are discussed in this section. It briefly describes computer programs, licensing requirements, and computer models used for this analysis.

3.1 Computer Programs and Standards The KENO-V.a computer code (Reference [3]), a part of the SCALE 4.4a package, was used to calculate the keff of 100 critical systems (criticality benchmark experiments). The 44 group cross section set 44GROUPNDF5 was used by the SCALE driver module CSAS25, which used modules BONAMI-2 and NITAWL to perform spatial and energy self-shielding of the cross sections for use in KENO-V.a. While

'holes' were used in the geometry models, they were modeled to preclude the error described in NRC Information Notice 2005-13, "Potential Non-conservative Error in Modeling Geometric Regions in the KENO-V.a Criticality Code," May 17, 2005.

The CASMO-3 computer code (Reference [4]), a multi-group two dimensional transport theoiy program was used to calculate isotopic compositions at given burnups for the assemblies. CASMO-3 is primarily a cross section generator with depletion capability. The code handles a geometry consisting of cylindrical fuel rods of varying compositions in a square pitch array. Typical fuel storage rack geometries can also be handled.

3.2 Analytical Requirements and Assumptions The purpose of the spent fuel storage racks is to maintain the fresh (i.e. unirradiated) and irradiated assemblies in a safe storage condition. The current licensing basis as defined by the existing Technical Specification Requirements and federal code requirements, 10 CFR 50.68(b), specifies the normal and accident parameters associated with maintaining the fresh and irradiated assemblies in a safe storage condition. Code of Federal Regulations, Title 10, Pail 50.68(b) defines the criticality accident requirements associated with the spent fuel racks and states the following: "If credit is taken for soluble boron, the k-effective of the spent fuel storage racks loaded with fuel of the maximum fuel assembly reactivity must not exceed 0.95, at a 95 percent probability, 95 percent confidence level, if flooded with borated water, and the k-effective must remain below 1.0 (subcritical) at a 95 percent probability, 95 percent confidence level, if flooded with unborated water."

The current analysis basis for Region 2 from Reference [5] is a maximum keff of less than 1.0 when flooded with unborated water, and less than or equal to 0.95 when flooded with water having a soluble boron concentration of 850 ppm. In addition, the ker in accident or abnormal operating conditions is less than 0.95 with 1350 ppm of soluble boron.

This analysis demonstrates that the effective neutron multiplication factor, klf, is less than 1.0 with the racks loaded with fuel of the highest anticipated reactivity, and flooded with unborated water at a temperature corresponding to the highest reactivity. In addition, the analysis demonstrates that kef is less than or equal to 0.95 with the racks loaded with fuel of the highest anticipated reactivity, and flooded with borated water at a temperature corresponding to the highest reactivity. The maximum calculated klff included a margin for uncertainty in reactivity calculations including manufacturing tolerances and is shown to be less than 0.95 with a 95% probability at a 95% confidence level with soluble boron credit.

Reactivity effects of abnormal and accident conditions were also evaluated to assure that under all credible abnormal and accident conditions, the kff will not exceed the regulatory limit of 0.95 under Page 13

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit borated conditions or a limit of 1.0 with unborated water. The double contingency principal of ANS-8.1/N 16.1-1975 (and the USNRC letter of April 1978; see fourth bullet below) specifies that it shall require at least two unlikely, independent and concurrent events before a criticality accident is possible.

This principle precludes the necessity of considering the simultaneous occurrence of multiple accident conditions.

Applicable codes, standard and regulations or pertinent sections thereof, include the following:

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

" Code of Federal Regulations, Title 10, Part 50.68(b), "Criticality Accident Requirements."

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

USNRC letter of April 14, 1978, to all Power Reactor Licensees - OT Position for Review and Acceptance of Spent Fuel Storage and Handling Applications (GL-78-0l 1), including modification letter dated January 18, 1979 (GL-79-004).

" L. Kopp, "Guidance on the Regulatory Requirements for Criticality Analysis of Fuel Storage at Light-Water Reactor Power Plants," NRC Memorandum from L. Kopp to T. Collins, August 19, 1998. (Reference [6])

" USNRC Regulatory Guide 1.13, "Spent Fuel Storage Facility Design Basis," Rev. 2, March 2007.

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

Code benchmarking was performed according to the general methodology described in Reference [7] that is also briefly described in Section A. 1. The critical experiments selected to benchmark the computer code system are discussed in Section A.3. The results of the criticality calculations, the trending analysis, the basis for the statistical technique chosen, the bias, and the bias uncertainty are presented in Sections A.4, A.5, and A.6.

Page 14

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 3.3 Computational Models and Methods This section describes the basic models used to evaluate the five regions in the PNP SFSR. Results using these models are described in later sections.

3.3.1 Bounding Fuel Assembly Description Batch X1 with an initial nominal planar average enrichment of 4.54 wt% 2 35 U is used to bound the possible enrichments and different fuel types in the storage rack evaluations. Table 3-1.

shows the dimensions of the bounding Xl model employed in this report. Reference [8]

provides a discussion of the appropriate biases required to bound the other assembly designs.

Some legacy fuel (e.g. Batches A-K) had lumped burnable absorber pins in empty tubes and/or had fuel rods replaced with either stainless steel rods or empty pin cells. Special consideration was given to these fuel assemblies in the burnup credit analysis. This is described in Section B.2. Fuel end details are not modeled. Fuel in the racks are modeled as surrounded by full (12 inches) water reflection at top and bottom. Reference [8] also shows that a zone loaded assembly has an equivalent or less reactivity than an assembly with a constant enrichment equal to the average of the assembly.

Table 3-1: Batch Xl Dimensions and Tolerances Parameter Nominal Tolerance Units in in Pitch 0.55 Pellet OD 0.3600 Clad ID 0.3670 Clad OD 0.417

1. Guide Bars 8 Effective Area* 0.1586 in2

1. Instrument Tubes I IT ID 0.3670 IT OD 0.417 Active Fuel 132.6 +0.29 Density, %TD I I I I

• Represents a conservatively small area for this parameter.

[ ]

3.3.2 Region 1 Rack Data Region 1 of the Palisades spent fuel storage pool comprises two rack designs. The main region consists of six 'C' racks for storage of 372 fuel assemblies. Regions IA, 1B, and IC are rack type 'C'. Another rack, the 'E' rack is placed in the 'North Tilt Pit' and can hold 50 Page 15

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit assemblies on a slightly wider pitch than the 'C' racks. Regions ID and 1E are rack type 'E'.

Table 3-2 lists the dimensions of the two racks. Figure 3-1 and Figure 3-2 provide sketches of each rack type, which illustrate the geometries used in KENO-V.a for each fuel cell. The actual comers of the box walls are rounded whereas the sketch is squared off. A single SS-304 separation rod of -0.25" OD is placed at each comer of the 'C' rack. A set of two similar SS-304 separation rods is placed before the rounded section of each comer of the 'E' rack. The fuel box in the rack is primarily SS-304, absorber material, and moderator. The standard SS-304 mixture of the SCALE composition library is used for this material. For this evaluation of Regions 1A, 1B, 1C, 1D, and IE, the absorber material was assumed to be degraded as described in Section 3.3.4.

Table 3-2: Dimensions of Palisades Region I Racks Region 1 Rack Type 'C' Rack 'E' Rack Dimension Nominal, in Tolerance, in Nominal, in Tolerance, in Cell Pitch-x 10.25 +0.04/-0.04 11.25 +0.04/-0.04 Cell Pitch-y 10.25 +0.04/-0.04 10.69 +0.04/-0.04 Box ID 8.56 +0.00/-0.12 9.00 +0.00/-0.12 Box OD 9.56 +0.12/-0.00 10.00 +0.12/-0.00 Box Wall Thickness, Inside 0.125 +0.010/-0.010 0.125 +0.010/-0.010 Box Wall Thickness, Outside 0.125 +0.010/-0.010 0.125 +0.010/-0.010 Page 16

A AR EVA Document No.: ANP-2858NP-003 Palisades SEP Region 1 Criticality Evaluation with Burnup Credit Figure 3-1: Sketch of Model of 'C' Rack Absor 0.21" 000000000000000 000000000000000 000000000000000

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A ARE EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure 3-2: Sketch of Model of 'E' Rack Abor 00000 00000*0000 0.1"000000000000000

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 3.3.3 Material Specification The fuel materials include the uranium oxide pellets, the clad material, and the moderator surrounding the cladding. All materials in the base model are assumed to be at 273 K. The moderator for the base case is assumed to be unborated water with a density of 1.0 g/cc. The fuel pellets are assumed to have a [ ] TD to correspond to the highest nominal density of past, current, or proposed pellets. No dish or chamfer is included in the density, thus the fuel column is conservatively modeled as a solid cylinder of fuel.

The fuel box in the rack is primarily SS-304, absorber material and moderator. The standard SS-304 mixture of the SCALE composition library is used for this material. The absorber material composition is based upon an assumption of the degraded condition of the B4C absorber material.

3.3.4 Models for Degradation of Carborundum Plates Evidence of stuck assemblies and recent attenuation testing of the absorber plates in Region 1 has indicated a reduction in the absorption capability of the flux trap between the fuel locations in the Region I rack. A possible cause is leaching of boron from the B4C absorber plates due to a combination of gamma irradiation of the phenol material and water in the absorber region of the box. An alternate, or complementary, cause of the loss of attenuation capability could be swelling of the box walls that reduce the moderator between the fuel assembly and the wall and between the walls of the flux trap. Either condition can reduce the effectiveness of the absorber plates. To bound the boron loss, both 'C' and 'E' rack models were developed with extensive voiding. There is a void between the fuel assembly envelope and the inner rack wall. There is a void between the inner and outer rack walls (that is, no poison material or water), and the space outside the outer rack wall is all void (no water or structural material);

thus, water occurs only inside the assembly envelope.

3.3.5 Swelling Model There is also evidence of swelling of the stainless steel wall next to the assembly cell that contains the Carborundum plates. The nature of the swelling is a central bulge (side to side) on one face of the fuel cell and is shown in Figure 3-3.

Page 19

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure 3-3: Photograph of Distorted Plate In order to bound the distortion, the effect of moving the cell walls toward or away from the fuel requires examination; see Figure 3-4. Three different possible configurations were examined. In the first, the outer stainless steel wall is displaced to the outer edge of the rack cell. The second is where the stainless steel wall on the interior moves inward until it rests against the fuel pins; and the third is where movement of both walls occurs.

To model the three swelling configurations, bowing in the outer wall was modeled by relocating the stainless steel outer wall until it contacts the adjacent cell. In this case, the outer walls cover a larger area and the stainless steel was thinned to conserve mass. Void filled the area formerly occupied by the wall. Bowing in the inner wall was modeled by relocating the stainless steel inner wall to the edge of the row of fuel pins, thus reducing the area covered by the inner walls. The mass of stainless steel was conserved by adding 'tabs' (protrusions) at the four inner corners, as shown in Figure 3-5 for the 'C' rack; similar modifications were made for the 'E' rack model. The third configuration is where both the inner and outer walls were bowed. Comparison of results showed that there was no identifiable trend as to one model being more restrictive than another. This would be expected since all cases use the same mass of wall material and same void volume; water occurs only inside the assembly envelope and with no moderation in the gap region, there is no distinction as to flux-exposure due to the physical placement of the wall material. Therefore, no penalty is taken for wall bowing and all cases are run at nominal configurations. However, the effect of residual carbon (from the degraded Carborundum plates) was examined separately with respect to the allowable rack loading patterns and the three swelling models (see Sections C. 1.2 and C. 1.3, respectively).

An additional penalty (Aksys) is assessed where necessary to bound the results of this study.

Page 20

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure 3-4: Fuel Swelling Model Spacer Rod Nominal, no wall swelling Weld 0@¢@@@@¢@@@ e 01@':2L 0`2L Wall swelling nodes t 0o ,=,= mm'='+

q ewlel P2, @01r".0021 ,' Q= L Page 21

A AREVA Document No.: ANP-2858NP-003 Palisades SEP Region 1 Criticality Evaluation with Burnup Credit Figure 3-5: 'C' Rack Inner Wall Bowing Model 3.4 Analytical Model Conservatisms This section lists the major conservatisms associated with this evaluation.

1) No credit is taken for intermediate spacer grids, or end fittings (see Appendix D).

2) No credit is taken for any absorber material in the Carborundum>' plates or moderator material in the gap region.

3) No credit is taken for the presence of residual gadolinia in the burned fuel assemblies.

4) A conservative fuel enrichment tolerance of 0.05 wt% is considered in the tolerance evaluation.

5) The only moderator material is contained within the fuel assembly envelope, and above/below the storage rack.

6) For the tolerance calculations, the four-of-four loading configuration bounds the three-of-four loading configuration as shown in Tables B-12 and B-13 of Reference [8].

Page 22

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 3.5 Tolerances, Penalties, Biases, and Uncertainties This section describes the tolerances, penalties, uncertainties, and biases utilized in the analysis of Racks

'C' (Regions 1A, 1B, and IC) and 'E' (Regions ID and IE). The penalties that pertain to the rack design tolerances and system parameters are discussed in detail in Appendix C. Additionally, the KENO-V.a bias with its associated uncertainty is discussed in Appendix A. The results of these sections are summarized in this subsection.

3.5.1 Method Discussion of Tolerances, Biases, and Uncertainties Criticality analysis methodology involves the computation of a base kff for the Spent Fuel Storage Rack (SFSR) using a code such as KENO-V.a. A KENO-V.a code bias plus uncertainty on the bias is determined based on comparison to measured critical fuel configurations (i.e., critical benchmarks; see Appendix A) is then applied to the base absolute keff. The bias is not assembly specific but can be dependent on the type of fuel involved (U0 2 versus MOX for example) or on intervening absorber materials. Typically, a bias is determined using critical benchmark calculations that are appropriate for the type of rack and fuel being analyzed. There is an uncertainty component on the bias that is the result of both measured and calculated uncertainties associated with the critical configurations analyzed.

The uncertainty on the bias may be statistically combined with other uncertainties as it is independent. The results of the benchmark evaluation provides a calculated bias of 0.00516 +

0.00526 (bias +/- Cybias) with a single-sided confidence factor C of 1.927 from the 100 experiments included in the validation.

Reactivity penalties due to fuel and rack structural tolerances and other uncertainties are determined by difference calculations and applied to the base k~ff plus bias (See Appendix C).

When Monte-Carlo codes are used in difference calculations an answer is provided with an associated uncertainty and the uncertainty on the difference calculation must be considered at the 95/95 confidence level.

The K 9 5 /95 for the evaluation is calculated using the following formulation:

K 9 5/95 = keff + biasm + A + [C 2( k 2 +".m2 + +-Akto 2 2

+ys2) 1 + Cto1 ]A/, + AkBu + Akfp, where, keff = the KENO-V.a calculated result; biasm = the bias associated with the calculation methodology underpredicting the benchmarks; Aksys =summation of Ak values associated with the variation of system and base case modeling parameters, e.g. moderator temperature and geometry biases; C = confidence multiplier based upon the number of benchmark cases; Gk, Gm, sys = standard deviation of the calculated keff, methodology bias, and system Aksys; Page 23

A ARE VA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Akto, (Y,.l = statistical combination and standard deviation of statistically independent Ak values due to manufacturing tolerances, e.g. fuel enrichment, cell pitch, etc.;

AkBu = 5% depletion reactivity uncertainty penalty for Burnup Credit cases; Akfp = overall uncertainty in fission product worth (burned fuel only, see Section E.4).

3.5.2 System and Tolerance Effects System and tolerance effects are calculated for several combinations of conditions. They include:

" Three-out-of-four and four-out-of-four fuel loading configurations.

" Rack C (Regions lB and 1C) and Rack E (Regions ID and 1E) configurations.

KENO-V.a is used for all the system and tolerance calculations. A two by two cell KENO-V.a model is used to calculate these effects.

3.5.2.1 System Effects The system effects are different conditions from the base model of the fuel and rack that could result in a higher calculated ker. These effects are considered additive unless otherwise noted.

The system effects are listed below.

1) Rack to Rack Interaction Model (see Section 4.7),

2) Effect of Control Blade Insertion during Depletion (see Section C. 1.1),

3) Effect of Residual Carbon in degraded Carborundum -(see Section C. 1.3),

4) Moderator Temperature Effect (see Section C. 1.7).

5) Storage of Control Blades in E-Rack (see Section C. 1.9).

3.5.2.2 Fuel and Rack Tolerance Effects The fuel and rack tolerances that are examined for the nominal (non-swollen) racks are listed below:

1) Centered to Off-Centered Assembly in Fuel Cell

2) Fuel Tolerance - Enrichment, +/-0.05 weight percent U-235

3) Fuel Tolerance - Theoretical Density, [ ]

4) Fuel Tolerance - Pellet OD, [ ]

Page 24

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit

5) Fuel Tolerance - Clad Inner Dimension, [ ]

6) Fuel Tolerance - Clad Outer Dimension, [ ]

7) Fuel Tolerance - Instrument Tube Dimension, ID, [ ]

8) Fuel Tolerance - Instrument Tube Dimension, OD, [ ]

9) Rack Tolerance - Box Inner Dimension, -0.12"

10) Rack Tolerance - Inner Box Wall Thickness, +/-0.0 10"

11) Rack Tolerance - Outer Box Wall Thickness, +/-0.010"

12) Rack Tolerance - Box Outer Dimension, +0.12"

13) Rack Tolerance - Cell Pitch, +/-0.04"

14) Rack Tolerance -Stainless Steel Separation Rod, OD, +/-0.005" Note that, since the base assumption is that no Carborundum material remains, tolerances for the absorber material are not required. See Appendix D for the effect of fuel rod pitch tolerance.

3.5.3 System and Tolerance Results Table 3-3 and Table 3-4 summarize the tolerance and uncertainty values obtained in the evaluation. Only positive bias/uncertainty values have been extracted from the various evaluations previously described, excluding values that are less than 0.0002, as they are statistically indistinguishable. Detailed results can be found in Appendix C. The additive biases are generally related to the rack configuration or environment that is defined in the equation as Aksys. The parameters related to randomly varying manufacturing tolerances for fuel and/or racks are statistically combined and defined in the equation as Akto 01 Table 3-3: 'C' Nominal Rack with Bias/Uncertainties Description Ak a of Ak Storage Pool Model Configuration Bias Interaction Model I - -

TOTAL (Arithmetic Sum of Penalties) 0 0 Tolerance Uncertainty Ak Fuel Tolerance - Enrichment +0.05 wt% 0.0023 0.0001 Fuel Tolerance - Theoretical Density [ 0.0003 0.0001 Fuel Tolerance - Clad OD [ 0.0015 0.0001 Rack Tolerance - Inner Box Wall Thickness Outside, -0.01" 0.0028 0.0001 Rack Tolerance - Outer Box Wall Thickness Outside, -0.01" 0.0027 0.0001 TOTAL (Statistical Combination of Uncertainties) 0.0048 0.0002 Page 25

A AREVA Document No.: ANP-28,58NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table 3-4: 'E' Nominal Rack 4-of-4 with BiaslUncertainties Description Ak a of Ak Storage Pool Model Configuration Bias Interaction Model I TOTAL (Arithmetic Sum of Penalties) 0 0 Tolerance Uncertainty Ak Fuel Tolerance - Pin Pitch [ 0.0004 0.0002 Fuel Tolerance - Enrichment +0.05 wt% 0.0026 0.0001 Fuel Tolerance - Theoretical Density [0.0005 0.0001 Fuel Tolerance - Clad OD [ 0.0019 0.0002 Rack Tolerance - Cell Pitch -0.04" 0.0011 0.0001 Rack Tolerance - Inner Box Wall Thickness Inside, -0.01" 0.0022 0.0001 Rack Tolerance - Outer Box Wall Thickness Inside, -0.01" 0.0021 0.0002 Rack Tolerance - SS Rod OD +0.005" 0.0011 0.0002 TOTAL (Statistical Combination of Uncertainties) 0.0047 0.0004 3.5.4 Summary of Bias and Uncertainty Values Table 3-5 and Table 3-6 summarize the variables shown in the formula in Section 3.5.1 for each of the regions examined. In addition, Table 3-7 summarizes the uncertainty penalty for fission product worth in burned fuel that is discussed in detail in Appendix E; the values listed are for 850 ppm dissolved boron.

Table 3-5: K95195 Determination Based Upon Calculated Bias/Uncertainty biasm Akys am Aktol a of Aktol Rack 'C' 2-of-4 0.00516 0.0030 0.00526 0.0048 0.0002 (Region IA)

Rack 'C' 3-of-4 0.00516 0.0040 0.00526 0.0048 0.0002 (Region 1B)

Rack 'C' 4-of-4 0.00516 0.0010 0.00526 0.0048 0.0002 (Region IC)

Rack 'E' 3-of-4 0.00516 0.0065 0.00526 0.0047 0.0004 (Region ID) I I I Rack 'E' 4-of-4 0.00516 0.0040 0.00526 0.0047 0.0004 (Region IE)

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table 3-6: 5% Depletion Reactivity Uncertainty Penalty Enrichment Rack Bumup (wt %) Loading Pattern (GWD/MTU) AkBu 4.54 C-Rack, 3-of-4 30 0.0103 4.54 C-Rack, 4-of-4 25 0.0105 4.54 C-Rack, 4-of-4 48 0.0180 4.54 E-Rack, 3-of-4 19 0.0067 3.30 E-Rack, 4-of-4 25 0.0104 4.54 E-Rack, 4-of-4 38 0.0143 Table 3-7: Fission Product Worth Uncertainty Penalty Page 27

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 4.0 RACK ANALYSIS In order to determine depletion and bumup credit, the following methodology was used:

Appendix B presents the methodology and calculation of depletion and burnup credit in detail. This methodology addresses the applicability of NUREG/CR-6801 (Reference [9]) for axial burnup profiles, the use of 5% reactivity decrement from zero burnup to burnup of interest, and the use of CASMOý3 to generate the fuel assembly isotopic compositions at specified burnups.

The current analysis basis for Region 2 from Reference [5] is a maximum k~ff of less than 1.0 when flooded with unborated water, and less than or equal to 0.95 when flooded with water having a boron concentration of 850 ppm. In addition, the kff in accident or abnormal operating conditions is less than 0.95 with 1350 ppm of soluble boron. This same basis is used for Regions 1A, IB, IC, ID, and IE, and was also used in Reference [8] for Region IA. The following abnormal conditions are considered for Regions 1A, IB, IC, ID, and 1E:

1. The deboration of the pool,

2. Misplacement of a fresh assembly within a cell that should be empty or replacement of a burnup credit (BUC) assembly,

3. Drop of a fuel assembly outside the rack but adjacent to the rack,

4. Off-center assembly (addressed in Section 3.5),

5. The 'straight deep drop' accident,

6. T-Bone drop accident, and

7. Rack interactions.

Page 28

A ARE EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit The deboration of the SFSR is considered the baseline case and the K 9 5/9 5 is calculated at both 0 ppm boron and 850 ppm boron. All other abnormal conditions are evaluated at 1350 ppm boron. Two

'misload' conditions are evaluated: misplacement of a fresh assembly into an empty cell in a partially (2-of-4 or 3-of-4) loaded rack and misplacement of a fresh assembly where a burned assembly should reside in a partially or fully loaded rack configuration. The misload is important to evaluate since empty cells are used to control reactivity. The misload condition bounds the drop outside the rack module because the misloaded assembly can increase the number of face adjacent fuel assemblies by at least four, whereas outside the rack will at most be two face adjacent assemblies to the dropped assembly. The off-center assembly, which is a horizontal movement of the assembly within the rack, is included in the tolerance evaluation. The drop accident within an empty cell is represented by the misload condition. In the

'straight deep drop', the assembly drops through the base of the rack to reside on the bottom of the fuel pool; this condition is bounded by the misloaded assembly condition. The T-Bone drop accident has an assembly lying on top of the rack structure and is effectively isolated from assemblies in the rack due to the distance provided by the end fittings and the rack height above the active fuel in the rack. Thus, the T-bone accident is also bounded by the misloaded condition.

The analysis for each of the regions is presented in this section for the unborated and borated condition (boron dilution event). The assembly misload conditions are presented for the borated condition of 1350 ppm boron. In addition, non-fissile components are addressed relative to being placed into empty cells and rack interface effects are addressed.

4.1 Region IA (2-of-4 Configuration)

Region 1A is analyzed with soluble boron credit, but without burnup credit. The acceptance criteria with credit for soluble boron are K 9 5/9 5 <1.0 without soluble boron and <0.95 with 850 ppm of soluble boron.

Region 1A is defined as Main Spent Fuel Pool with 2-of-4 fresh fuel loading having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent. The results are presented in Table 4-1 for the Region 1A geometry.

Table 4-1: Region 1A K95 /95 Determination for Boron Dilution Assembly Dissolved Enrichment, Average Boron, keff Ok K 9 5/95 Criterion wt% U235 Burnup, ppm GWD/MTU 4.54 0 850 0.8242 0.0003 0.8436 !50.95 4.54 0 0 0.9144 0.0004 0.9358 < 1.0 4.1.1 Misload Conditions It is necessary to examine the accident condition of misloading a fresh assembly into the empty location in a '2-of-4' loading pattern. For this, it is assumed that the fresh assembly has an enrichment of 4.54%. A soluble boron concentration of 1350 ppm is used. The fresh misloaded fuel assembly is placed into a designated non-fuel position near the center of the matrix (8x8). The'results are shown in Table 4-2.

Page 29

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table 4-2: Region 1A K95 /95 Determination for Misload Conditions Assembly Dissolved Enrichment, Average Boron, kff Ok K 95 /95 Criterion wt% U235 Burnup, ppm GWD/MTU 4.54 0 1350 0.9078 0.0004 0.9292 <0.95 4.1.2 Conservatisms The major conservatisms are complete voiding within the cell walls and outside of the assembly envelope, and 1350 ppm boron rather than 1720 ppm minimum boron (a Technical Specification Requirement).

4.2 Region 1B (3-of-4 Configuration)

Region 1B is analyzed with soluble boron credit. The acceptance criteria with credit for soluble boron are K 9 5/9 5 <1.0 without soluble boron and <0.95 with 850 ppm of soluble boron. Region IB is defined as Main Spent Fuel Pool with 3-of-4 loading having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent and burnup credit as shown in Table 4-3. The results are presented in Table 4-4 for the Region lB geometry.

Table 4-3: Region 1B (3-of-4 Loading) Requirements Nominal planar average U-235 Burnup > Burnup enrichment (GWD/MTU) (GWD/MTU) with (wt%) 10% Uncertainty

<2.10 0 0 2.40 3.7 4.1 2.60 6.1 6.7 2.80 8.6 9.5 3.00 11.1 12.2 3.20 13.5 14.9 3.40 16.0 17.6 3.60 18.4 20.2 3.80 20.9 23.0 4.00 23.4 25.7 4.20 25.8 28.4 4.40 28.3 31.1 4.54 30.0 33.0 Page 30

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table 4-4: Region 1B K95 /95 Determination for Boron Dilution Assembly Dissolved Enrichment, Average Boron, kff Uk K95/95 Criterion wt% U235 Burnup, ppm GWD/MTU 2.10 0 850 0.8414 0.0003 0.8608 < 0.95 4.54 30 850 0.8434 0.0003 0.8752 < 0.95 4.54 30 0 0.9220 0.0003 0.9547 < 1.0 4.2.1 Misload Conditions It is necessary to examine the accident condition of misloading a fresh assembly into the empty location in a '3-of-4' loading pattern, which bounds misloading of a fresh assembly where a burned assembly should reside. For this, it is assumed that the fresh assembly has an enrichment of 4.54%. A soluble boron concentration of 1350 ppm is used for the misloading case. The fresh misloaded fuel assembly is placed into a designated non-fuel position near the center of the matrix (8x8). The results are shown in Table 4-5..

Table 4-5: Region 1B K95 /95 Determination for Misload Conditions Assembly Dissolved Enrichment, Average Boron, keff (Fk K9 ,/95 Criterion wt% U235 Burnup, ppm GWD/MTU 2.10 0 850 0.8414 0.0003 0.8608 < 0.95 4.54 30 850 0.8434 0.0003 0.8752 < 0.95 4.54 30 1350 0.8908 0.0003 0.9235 < 0.95 4.2.2 Conservatisms The major conservatisms are complete voiding within the cell walls and outside of the assembly envelope, and 1350 ppm boron rather than 1720 ppm minimum boron (a Technical Specification Requirement).

Page 31

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 4.3 Region 1C (4-of-4 Configuration)

Region IC is analyzed with soluble boron credit. The acceptance criteria with credit for soluble boron are K 95/9 5 <1.0 without soluble boron and <0.95 with 850 ppm of soluble boron. Region 1C is defined as the Region 1 Main Spent Fuel Pool with 4-of-4 loading having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent and burnup credit as shown in Table 4-6. The results are presented in Table 4-7 for the Region 1C geometry.

Table 4-6: Region IC (4-of-4 Loading) Requirements Nominal planar average U-235 Burnup > Burnup (GWD/MTU) enrichment (GWD/MTU) with 10% Uncertainty (wt%)

<1.35 0 0 2.40 18.8 20.7 2.60 22.3 24.5 2.75 25.0 27.5 2.80 25.6 28.2 3.00 28.2 31.0 3.20 30.8 33.9 3.40 33.4 36.7 3.60 35.9 39.5 3.80 38.5 42.4 4.00 41.1 45.2 4.20 43.6 48.0 4.40 46.2 50.8 4.54 48.0 52.8 Table 4-7: Region 1C K95/95 Determination for Boron Dilution Assembly Dissolved Enrichment, Average Boron, kff Ok K 95 /9 5 Criterion wt% U235 Burnup, ppm GWD/MTU 1.35 0 850 0.8292 0.0002 0.8456 < 0.95 2.75 25 850 0.8698 0.0002 0.8987 < 0.95 4.54 48 850 0.8709 0.0002 0.9079 < 0.95 4.54 48 0 0.9463 0.0002 0.9837 < 1.0 Page 32

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 4.3.1 Misload Conditions It is necessary to examine the accident condition of misloading a fresh assembly into a designated location in a 4-of-4 loading patterns. For this, it is assumed the fresh assembly has an enrichment of 4.54%. A soluble boron concentration of 1350 ppm is used for the misloading case. The fresh misloaded fuel assembly is placed into a position near the center of the matrix (8x8). The results are shown in Table 4-8.

Table 4-8: Region 1C K95/95 Determination for Misload Conditions Assembly Dissolved Enrichment, Average Boron, keff 1k K95/95 Criterion wt% U235 Burnup, ppm GWD/MTU 1.35 0 850 0.8292 0.0002 0.8456 < 0.95 2.75 25 850 0.8698 0.0002 0.8987 < 0.95 4.54 48 850 0.8709 0.0002 0.9079 < 0.95 4.54 48 1350 0.8583 0.0003 0.8957 < 0.95 4.3.2 Conservatisms The major conservatisms are complete voiding within the cell walls and outside of the assembly envelope, and 1350 ppm boron rather than 1720 ppm minimum boron (a Technical Specification Requirement).

4.4 Region 1D (3-of-4 Configuration)

Region 1D is analyzed with soluble boron credit. The acceptance criteria are K95/95 < 1.0 without soluble boron and < 0.95 with 850 ppm of soluble boron. Regions ID and IE are contained within a five by ten rectangular array of cells with Region 2 racks placed on both ends of the rack as shown in Figure 2-1 in the North Tilt Pit. Region ID is defined as North Tilt Pit with 3-of-4 loading, having a nominal planar average U-235 enrichments less than or equal to 4.54 weight percent, and with burnup credit as shown in Table 4-9. The results are presented in Table 4-10 for Region ID.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table 4-9: Region 1D (3-of-4 Loading) Requirements Burnup ( Burnup Nominal planar average U-235 (GWD/MTTU) (GWD/MTU) with enrichment 10% Uncertainty (wt%)

<2.35 0.0 0.0 2.40 0.4 0.5 2.60 2.2 2.4 2.80 3.9 4.3 3.00 5.6 6.2 3.20 7.4 8.1 3.40 9.1 10.0 3.60 10.8 11.9 3.80 12.6 13.8 4.00 14.3 15.7 4.20 16.1 17.7 4.40 17.8 19.6 4.54 19.0 20.9 Table 4-10: Region 1D K95 /95 Determination for Boron Dilution Assembly Dissolved Enrichment, Average Boron, keff Gk K 95/95 Criterion wt% U-235 Burnup, GWD/MTU ppm 2.35 0 850 0.8336 0.0003 0.8555 < 0.95 4.54 19 850 0.8653 0.0003 0.8956 < 0.95 4.54 19 0 0.9445 0.0003 0.9761 < 1.0 4.4.1 Misload Conditions It is necessary to examine the accident condition of misloading a fresh assembly into the empty location in a '3-of-4' loading pattern, which bounds misloading of a fresh assembly where a burned assembly should reside. For this, it is assumed the fresh assembly has an enrichment of 4.54%. A soluble boron concentration of 1350 ppm is used for the misloading case. The fresh misloaded fuel assembly is placed into a designated non-fuel position near the center of the matrix (8x8). The results are shown in Table 4-11.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table 4-11: Region ID K95/95 Determination for Misload Conditions Assembly Dissolved Enrichment, Average Boron, ken yk K9,/9, Burnup, Criterion wt% U235 GWD/MTU ppm 2.35 0 850 0.8336 0.0003 0.8555 < 0.95 4.54 19 850 0.8653 0.0003 0.8956 _<0.95 4.54 19 1350 0.8835 0.0003 0.9151 _<0.95 4.4.2 Conservatisms The major conservatisms are complete voiding within the cell walls and outside of the assembly envelope, and 1350 ppm boron rather than 1720 ppm minimum boron (a Technical Specification Requirement).

4.5 Region IE (4-of-4 Configuration)

Region IE is analyzed with soluble boron credit. The acceptance criteria are K 95/95 < 1.0 without soluble boron and < 0.95 with 850 ppm of soluble boron. Regions ID and 1E are contained within a five by ten rectangular array of cells with Region 2 racks placed on both ends of the rack as shown in Figure 2-1 in the North Tilt Pit. Region IE is defined as North Tilt Pit with 4-of-4 loading, having a nominal planar average U-235 enrichments less than or equal to 4.54 weight percent, and with burnup credit as shown in Table 4-12. The results are presented in Table 4-13 for Region 1E.

Table 4-12: Region IE (4-of-4 Loading) Requirements Nominal planar Burnup > Burnup average U-235 (GWDIMTU) (GWD/MTU) with enrichment 10% Uncertainty (wt%)

<1.48 0.0 0.0 2.40 12.6 13.9 2.60 15.4 16.9 2.80 18.1 19.9 3.00 20.9 23.0 3.20 23.6 26.0 3.30 25.0 27.5 3.40 26.0 28.7 3.60 28.1 31.0 3.80 30.2 33.3 4.00 32.3 35.6 4.20 34.4 37.9 4.40 36.5 40.2 4.54 38.0 41.8 Page 35

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table 4-13: Region 1E K95 /95 Determination for Boron Dilution Assembly Dissolved Enrichment, Average Boron, kff Ok K 95/95 Criterion wt% U-235 Burnup, GWD/MTU ppm 1.48 0 850 0.8145 0.0002 0.8338 < 0.95 3.30 25 850 0.8661 0.0003 0.8979 < 0.95 4.54 38 850 0.8756 0.0003 0.9116 < 0.95 4.54 38 0 0.9516 0.0003 0.9883 < 1.0 4.5.1 Misload Conditions It is necessary to examine the accident condition of misloading a fresh assembly into a designated location in a 4-of-4 loading patterns. For this, it is assumed the fresh assembly has an enrichment of 4.54%. A soluble boron concentration of 1350 ppm is used for the misloading case. The fresh misloaded fuel assembly is placed into a position near the center of the matrix (8x8). The results are shown in Table 4-14.

Table 4-14: Region 1E K95/95 Determination for Misload Conditions Assembly Dissolved Enrichment, Average Boron, ker 1k K95/95 Criterion wt% U235 Burnup, GWD/MTU ppm 1.48 0 850 0.8145 0.0002 0.8338 < 0.95 3.30 25 850 0.8661 0.0003 0.8979 < 0.95 4.54 38 850 0.8756 0.0003 0.9116 < 0.95 4.54 38 1350 0.8715 0.0004 0.9082 < 0.95 4.5.2 Conservatisms The major conservatisms are complete voiding within the cell walls and outside of the assembly envelope, and 1350 ppm boron rather than 1720 ppm minimum boron (a Technical Specification Requirement).

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 4.6 Non-Fuel Bearing Components (NFBC)

There are several NFBC that may potentially be inserted into the racks. Only Rack C is evaluated for storage of NFBC described in this section. The four components are:

1. Heavy Test Assembly - a Standard Assembly with lead (Pb) pellets rather than UO2 ,

2. Test Gauge Assembly - comprised of stainless steel angles and plates to allow testing the box inner dimension,

3. Stainless Steel Dummy Assembly - an assembly containing only SS-304 Replacement Rods (no fuel rods), and

4. Vessel Fluence Capsule (Surveillance Capsule) and Carrier (bounded by a hollow stainless steel box, 7.75" on the outside and 5.48" on the inside, comprised of a SS304 shell and a water-filled center; total mass, -522 Kg or 1100 lbs).

For the 3-of-4 BUC portion of the rack, the most reactive configuration at the nominal 850 ppm boron concentration is the 4.54% enriched fuel at 30 GWD/MTU, as indicated in Table 4-4. Placement of NFBC is considered in both an open cell and as a replacement for a fuel assembly. These results are shown in Table 4-15.

Table 4-15: NFBC Reactivity Evaluation for 3-of-4 BUC Rack Description I kfr I k K 95 /95 BASE RACK 'C' 3-of-4 8x8 Array Model 0.8434 0.0003 0.8752 Dummy Assembly Results Component I in empty cell 0.8451 0.0003 0.8769 Component I replacing assembly 0.8400 0.0003 0.8718 Component 2 in empty cell 0.8429 0.0003 0.8747 Component 2 replacing assembly 0.8404 0.0003 0.8722 Component 3 in empty cell 0.8450 0.0003 0.8768 Component 3 replacing assembly 0.8401 0.0003 0.8719 Stainless Steel Block/Tubes Component 4 SS Square Shell in Water cell with 7.75" OD 0.8457 0.0003 0.8775 and 5.48" ID in empty cell SS Square Shell in Water cell with 7.75" OD 0.8393 0.0003 0.8711 and 5.48" ID replacing assembly The analysis of the Heavy Test Assembly, the Test Gauge Assembly, the Stainless Steel Dummy Assembly, and the Surveillance Capsule, when placed in an empty location in the 3-of-4 pattern, showed a small increase in reactivity due to displacement of the borated water. Current restrictions for these components, when placed in an empty cell, state that they must be at least 10 locations away from another NFBC; this restriction shall be maintained, as indicated in Section 6.0. Each NFBC is unique (one of a kind), and when isolated, do not significantly impact system reactivity. Values of K95/95 associated with them are much less than the allowable limit of 0.95 at 850 ppm dissolved boron. These values indicate that the NFBC may be safely placed in an empty cell in Region IB. In addition, any non-fuel component composed of primarily SS that displaces less than 30 in2 of water in any plane within the active fuel can be stored face adjacent to fuel in a designated empty cell as long as the NFBC is at least ten locations away from another non-fuel bearing component that is face adjacent to fuel.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit For the 4-of-4 BUC portion of the rack, the most reactive configuration examined for a 4-of-4 arrangement at the nominal 850 ppm boron concentration is the 4.54% enriched fuel at 48 GWD/MTU, as indicated by Table 4-7. Placement of a NFBC is considered as a replacement for a fuel assembly. Results are summarized in Table 4-16 and show that the NFBC may safely replace a fuel assembly in Region IC.

Table 4-16: NFBC Reactivity Evaluation for 4-of-4 BUC Rack Description keff Crk K9 1/9s BASE RACK 'C' 4-of-4 8x8 Array Model 0.8709 0.0002 0.9079 Dummy Assembly Results Component 1 replacing assembly 0.8679 0.0002 0.9049.

Component 2 replacing assembly 0.8673 0.0002 0.9043 Component 3 replacing assembly 0.8669 0.0002 0.9039 Stainless Steel Block/Tubes Component 4 SS Square Shell in Water cell with 7.75" OD and 5.48" ID 70.8675 0.0003 0.9045 4.6.1 Misload Conditions A misloading of a NFBC (other than the heavy test assembly or the test gauge assembly) into a designated empty cell in Region 1A or lB that is within 10 cells of another NFBC (other than the Heavy Test Assembly or the Test Gauge Assembly) loaded into a designated empty cell, is bounded by a fuel misloading described in Sections 4.1.1 and 4.2.1 above, for Regions IA and 1B, respectively. A fuel assembly is more reactive than an NFBC.

4.7 Rack Interactions The interactions evaluated are:

" Between Region IA and Region 2 (This was analyzed in Reference [8], and is still valid).

• Between Region lB and IA.

• Between Region lB and 1C.

• Between Region 1C and IA.

" Between Region 1D and IE.

" Between Region lB and Region 2.

" Between Region IC and Region 2.

• Between Region 1D and Region 2.

• Between Region 1E and Region 2.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit The detailed models to perform this study are defined and discussed in detail in Appendix C. 1.4.

Interaction between any two regions is examined by evaluating the two regions together. If keff increases above the maximum of either individual region, then there is an effect. The most severe tolerance values were used for evaluation of interactions between regions; this is a conservative approach.

The fuel elevator and fuel inspection stations, which will handle fresh fuel, are located in a region adjacent to the C-rack. Fresh fuel assemblies at these stations are nominally water isolated from the rack due to distance. However, a fresh assembly may be inadvertently placed next to the C-rack. This would be bounded by either a misload described above or the interactions described below. Therefore, the presence of the fuel elevator and fuel inspection station does not cause additional restrictions to the acceptable fuel loading patterns.

4.7.1 Regions 1A, 1B, and 1C Interaction Effects Results The interaction between the loading zones (2-of-4, 3-of-4, and 4-of-4) is examined.

For the nominal 850 ppm boron concentration, the case with the highest value of keff from KENO-V.a for the 4-of-4 loading has an enrichment of 4.54% and a bumup of 48 GWD/MTU; for the 3-of-4 loading, it is 4.54% enrichment and a burnup of 30 GWD/MTU (see Table 4-4 and Table 4-7, respectively). For 2-of-4 loadings, fresh fuel with a maximum enrichment of 4.54% is allowed. All interaction cases were generated at 850 ppm dissolved boron. These situations are examined in various combinations. The 4-of-4 with 3-of-4 situation was examined in the empty cell of the 3-of-4 arrangement adjacent to the 4-of-4 region. The situation with the full row of the 3-of-4 adjacent to the 4-of-4 would not be allowed since it would create another 4-of-4 cluster that would have to comply with the 4-of-4 loading restrictions. (See Figure 4-1, Figure 4-2, and Figure 4-3.)

Figure 4-1: Region 1B Adjacent to Region 1A 51, A

Empty cell Region 1A (4.54% fresh fuel), 2-of-4 Region 1B (4.54% and a burnup of 30 GWD/MTU), 3-of-4 Page 39

A ARE VA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure 4-2: Region lB Adjacent to Region 1C I I Empty cell Region 1B (4.54% and a burnup of 30 GWD/MTU), 3-of-4 Region 1C (4.54% and a burnup of 48 GWD/MTU), 4-of-4 Figure 4-3: Region 1C Adjacent to Region IA This configuration is not allowed as it creates a non-allowed 3-of-4 pattern.

This conservatively bounds the allowable pattern.

Empty cell Region 1A (4.54% fresh fuel), 2-of-4 Region 1C (4.54% and a burnup of 48 GWD/MTU), 4-of-4 Page 40

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Placing one configuration up against another frequently creates a non-allowed configuration at the boundary. These are examined here only to show that they do not result in an unacceptably high reactivity causing a new accident condition to be analyzed. Any loading pattern is to be carefully examined to ensure against unacceptable loading configurations.

Results are summarized in Table 4-17.

Table 4-17: Interaction Results for Regions 1A, 1B, and IC Racks Case Description keff C'k K 95/ 95 Base - Region 1A, 4.54%, 0 GWD/MTU 0.8242 0.0003 0.8436 Base - Region IB, 4.54%, 30 GWD/MTU 0.8434 0.0003 0.8752 Base - Region IC, 4.54%, 48 GWD/MTU 0.8709 0.0002 0.9079 Region lB adjacent to Region IA 0.8266 0.0003 0.8584 Region lB adjacent to Region IC 0.8657 0.0003 0.9057 Region 1C adjacent to Region 1A (4-of-4 next to 2-of-4) 0.8517 0.0003 0.8917 Results indicate that the boundary interaction depicted in Figure 4-1, with Region IB adjacent to Region IA, is less reactive than Region 1B by itself. In addition, each 2x2 array at the boundary is configured in the acceptable 2x2 checkerboard pattern. Figure 4-2 illustrates the acceptable boundary interaction with Region 1B adjacent to Region IC where the designated empty cell in the 3-of-4 loading pattern is placed on the boundary adjacent to the 4-of-4 loading pattern; results show that the overall reactivity is bounded by the limit for Region IC.

At the boundary itself, each 2x2 array includes two fuel assemblies from Region 1C and only one from Region I B, such that the Table 4-3 burnup restrictions for 3-of-4 loading are satisfied. Finally, the boundary interaction illustrated in Figure 4-3 places Region IC adjacent to Region I A, but creates a non-allowed 3-of-4 pattern at the boundary, such that a fresh fuel assembly is face adjacent to another fuel assembly. This configuration bounds the allowable pattern and results indicate that the overall reactivity remains bounded by the limit for Region 1C. However, the interface between Region 1A and IC in Figure 4-3 creates a 3-of-4 (Region IB) pattern which must satisfy the requirements of Table 4-3, too, leaving a less reactive configuration. The restriction of Item 1) f) of Section 6.0, must also be adhered to.

4.7.2 Region 1D and 1E Interaction Effects Results The '4-of-4' configuration is assumed to have an enrichment of 4.54% and a burnup of 38 GWD/MTU. For the '3-of-4' configuration, fuel is modeled at an enrichment of 4.54% and 19 GWD/MTU. All cases were at 850 ppm dissolved boron. Several possible combinations and general conclusions are drawn from those cases.

Due to the finite size of the E-Rack and the repeating pattern within the 3-of-4 configuration, the layouts shown in Figure 4-4 were developed. The base case is the 4-of-4 case with burned fuel, 4.54% and 38 GWD/MTU. All cases were run at 850 ppm dissolved boron. The reserved locations shown in Figure 4-4 denote fixed-location assemblies that were not explicitly modeled in the KENO-V.a calculations. These assemblies are found to be less reactive than the limiting assemblies. Examining the burnup table provided in Table 4-12 shows that for the more limiting 4-of-4 configuration, a burnup of approximately 28.35 GWD/MTU is required for 3.3 wt% legacy fuel. Both fixed-location assemblies have initial Page 41

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit enrichments less than 3.3 wt% and burnup greater than 30 GWD/MTU. Thus excluding them simplifies the analysis and produces a slightly more conservative calculated reactivity. Results are summarized in Table 4-18.

Table 4-18: Interaction Results for Regions 1D and 1E Configuration Case Description ke!ff O'k K 95/9 5 Base - Region ID, 4.54%, 19 GWD/MTU 0.8653 0.0003 0.8956 Base - Region IE, 4.54%, 38 GWD/MTU 0.8756 0.0003 0.9116 Mixed 1 (see Figure 4-4) 0.8625 0.0003 0.9010 Mixed 2 0.8584 0.0003 0.8969 Mixed 3 0.8649 0.0003 0.9034 Mixed 4 0.8725 0.0003 0.9110 Mixed 5 0.8508 0.0003 0.8893 Mixed 6. 0.8492 0.0003 0.8877 Comparing the mixed loading results with the base 4-of-4 results, it is apparent that the 4-of-4 loading is driving reactivity. The most reactive mixed case is still less reactive than the 4-of-4 case used to set the loading curve.

The analysis of boundary interactions between the 4-of-4 and 3-of-4 layouts in the E-Rack has explicitly analyzed six allowable configurations; results show that all analyzed configurations remain bounded by the limit for Region 1E (0.9116). Other configurations are also possible within the restriction of Item 1) f) of Section 6.0.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Bumup Credit Figure 4-4: Allowable Region 1E Configurations with Mixed Loadings Mixed I Mixed 2 53 54 55 56 57 58 59 60 61 62 53 54 55 56 57 58 59 60 61 62 A A B B C C D D E E Mixed 3 Mixed 4 53 54 55 56 57 58 59 60 61 62 53 54 55 56 57 58 59 60 61 62 A A B B C C D D E E Mixed 5 Mixed 6 53 54 55 56 57 58 59 60 61 62 53 54 55 56 57 58 59 60 61 62 A A B B C C D D E E Empty cell Region 1 E (4.54% and a burnup of 38 GWD/MTU), 4-of-4 Region ID (4.54% and a burnup of 19 GWD/MTU), 3-of-4 Reserved (not explicitly modeled, but conservative)

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A ARE VA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 4.7.3 Regions 1B and 1C, 1D and 1E, with Region 2 Interaction Effects Results The interaction between the C-Rack and E-Rack loading zones do not require additional restrictions on loading patterns. All analyses to date have demonstrated that when examining adjacent non-contiguous zones, the rack with the highest value of krff dominates. This was evaluated at distances as close as 0.1 inches and at distances greater than 10 inches, as shown in Table 4-14 of Reference [8]. The gap size between the racks was not found to impact the total reactivity of either rack. For example, in Table 4-14 of Reference [8] three different cases were reported with different gaps between E-Rack and Region 2 (0.1, 3.3, and

>I0inches). The results showed:

0.1 inch gap k1ef = 0.8016 +/- 0.0003 3.3 inch gap lffO= 0.8017 +/- 0.0003

>10 inch gap. ker= 0.8015 +/- 0.0003 The same table showed that the E-Rack model gave a value of kff= 0.8139 +/- 0.0003 and the Region 2 model gave a value of klff= 0.7426 +/- 0.0002. It is seen that the values of keff were dominated by that of the E-Rack, demonstrating that the value of klffis driven by the higher value between the two racks. It also shows that the thickness of moderator between the racks does not impact this conclusion.

That the amount of moderator between the regions is not impacting the interaction results is of significance here. The primary difference between this previous model and the current model is the reduction in moderator in the gaps between the cell walls. While the earlier model also had residual carbon in the absorber material, the Reference [8] analysis examined both deborated and borated moderator conditions, and showed that the conclusion of non-interaction was still valid. As such, it is concluded that the more restrictive assumptions of this analysis of wide voids and no boron or carbon absorber do not raise new interaction concerns with Region 2.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 5.0

SUMMARY

AND CONCLUSIONS This report documents the criticality safety analysis for the Palisades Region 1 fuel pool storage and shows that all requirements are met. The Region lA, 1B, IC, ID, and 1E racks are analyzed to allow storage of fuel applying a burnup credit (Regions 1B, 1C, 1D, and 1E, only), a complete loss of boron in the Carborundum*' plates, and complete voiding of the gaps between the rack walls. A minimum margin of 0.0117Ak is calculated for the boron dilution events with respect to 10CFR50.68 criteria, both borated and unborated. All abnormal conditions meet the 0.95 criterion at 1350 ppm of boron with a minimum margin of 0.0208 Ak.

6.0 LICENSING REQUIREMENTS This analysis requires that the Technical Specifications for the Region 1 SFSR be modified to accommodate fuel in the manner defined by this document. Final wording of the Technical Specifications may differ from the wording presented here as long as the intent of the requirements remains the same.

The following requirements apply to Region 1.

1) Change the Region 1 definition to the following new regions a) Region 1A - Region 1 Main Spent Fuel Pool with checkerboard loading of fuel and empty or non-fuel bearing component cells for fuel having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent. This region should not contain any face adjacent fuel.

b) Region IB - Region 1 Main Spent Fuel Pool with 3-of-4 loading having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent and meeting the requirements set forth in Table 4-3 (see Figure 6-1).

Figure 6-1: 3-of-4 Fuel Loading Pattern for Regions 1B and 1D Empty cell

<.4.54 wt% U-235Aseby Assembly c) Region IC - Region 1 Main Spent Fuel Pool with 4-of-4 loading with no required empty cells, having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent and

'meeting the requirements set forth in Table 4-6.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit d) Region ID - Region 1 North Tilt Pit with 3-of-4 loading having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent and meeting the requirements set forth in Table 4-9 (see Figure 6-1).

e) Region 1E - Region 1 North Tilt Pit with 4-of-4 loading with no required empty cells, having nominal planar average U-235 enrichments less than or equal to 4.54 weight percent and meeting the requirements set forth in Table 4-12.

f) Regions 1A, IB & 1C in the main pool and Regions 1D & 1E in the North Tilt Pit can be distributed in Region 1 in any manner providing that any 2-by-2 grouping of cells and the assemblies in them meet the requirements above for the number of cells occupied. For example, for a 4 x 4 group of cells, all of the configurations shown in Figure 6-2 must be examined against the above requirements:

Figure 6-2: Nine 2-by-2 Groupings Possible within a 4-by-4 Matrix

2) Non-fuel bearing components a) Any component with non-fissile material can be stored in any designated fuel location in Region 1A, 1B, 1C, 1D, or 1E without restriction.

b) If a non-fissile material meets the criteria for a non-fuel bearing component (NFBC) as listed below it can be stored face adjacent to fuel in a designated empty cell in Region 1A or lB.

i) The gauge dummy assembly and the lead dummy assembly can be stored face adjacent to fuel in any designated empty cells with no minimum required separation distance.

ii) A component composed of primarily SS that displaces less than 30 in2 of water in any plane within the active fuel can be stored face adjacent to fuel in a designated empty cell as long as the NFBC is at least ten locations away from another non-fuel bearing component that is face adjacent to fuel.

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A ARE EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit c) Control blades can be stored in both fueled and unfueled locations in Regions 1D and 1E, with no limitation on the number.

3) Legacy Fuel Storage a) For fuel in batches A through K stored in Region 1, a 1.0 GWD/MTU penalty must be subtracted from the burnup value, as indicated by the core monitoring system, prior to applying the requirements set forth in Licensing Requirement I (above).

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A ARE VA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit

7.0 REFERENCES

1. "Quality Assurance Data Final Report, Boron Carbide Neutron Absorbing Plate, NUS Corporation Purchase Order No. PT-5097-9 SI," Research & Development Division, The Carborundum Company, Niagara Falls, New York, September, 1977.

2. NRC Letter to Palisades Nuclear Plant, Docket No. 50-255/License No. DPR-20, "Palisades Plant -

Issuance of Amendment To Change Enrichment Limits in Fuel Pool (TAC MB 1362)," ML020440048 2002-02-26.

3. SCALE4.4a, "A Modular Code System for Performing Standardized Computer Analysis for Licensing Evaluation," NUREG/CR-0200, Revision 6, May 2000, Oak Ridge National Laboratory (ORNL).

4. M. Edenius, et al., "CASMO A Fuel Assembly Burnup Program," STUDSVIKiNFA-89/3, Studsvik AP, Nyk6ping, Sweden, November 1989.

5. EA-SFP-99-03, "Palisades New Fuel Storage, Fuel Pool and Fuel Handling Criticality Safety Analysis,"

10/23/2000.

6. L. Kopp, "Guidance on the Regulatory Requirements for Criticality Analysis of Fuel Storage at Light-Water Reactor Power Plants," NRC Memorandum from L. Kopp to T. Collins, August 19, 1998, ML072710248.

7. Nuclear Regulatory Commission, "Guide for Validation of Nuclear Criticality Safety Calculational Methodology," NUREG/CR-6698, January 2001.

8. Palisades Nuclear Plant, Docket No. 50-255, License No. DPR-20, "License Amendment Request for Spent Fuel Pool Region I Criticality, Enclosure 4" ML083360624, November 25, 2008.

9. Nuclear Regulatory Commision, "Recommendations for Addresing Axial Burnup in PWR Burnup Credit Analysis," NUREG/CR-6801, March 2003.

10. NRC Letter to Palisades Nuclear Plant, "Supplemental Information Needed for Acceptance of Requested Licensing Action (TAC ME2162)," ML092860363, October 15, 2009.

11. Shearon Harris Nuclear Power Plant, Unit No. 1 Docket No. 50-400/License No. NPF-63 Request for License Amendment, Framatome ANP, Inc 77-5069740-NP-00, "Shearon Harris Criticality Evaluation."

ML052510504, 2005-08-31.

12. Palisades Plant, Docket No. 50-255/License No. DPR-20, "Palisades Plant - Issuance of Amendment RE:

Spent Fuel Pool Region I Storage Requirements (TAC No. ME 161)," ML090160238, 2009-02-06.

13. Bierman, S.R., Durst, B.M., Clayton, E.D., "Critical Separation Between Subcritical Clusters of 4.29 Wt% 235U Enriched U02 Rods in Water With Fixed Neutron Poisons," Battelle Pacific Northwest Laboratories, NUREG/CR-0073 (PNL-2615).

14. Baldwin, M. N., et al., "Critical Experiments Supporting Close Proximity Water Storage of Power Reactor Fuel," BAW-1484-7, July 1979.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit

15. Hoovler, G. S., et al., "Critical Experiments Supporting Underwater Storage of Tightly Packed Configurations of Spent Fuel Pins," BAW- 1645-4, November, 1981.

16. "Dissolution and.Storage Experimental Program with U[4.75]02 Rods," Transactions of the American Nuclear Society, Vol. 33, pg. 362, 1979.

17. Nuclear Energy Agency, "International Handbook of Evaluated Criticality Safety Benchmark Experiments." NEA/NSC/DOC(95)03, Nuclear Energy Agency, Organization for Co-operation and Development, 2002.

18. D'Agostino, R.B. and Stephens, M.A., Goodness-of-fit Techniques. Statistics, Textbooks and Monographs, Volume 68. New York, New York, 1986.

19. ANSI/ANS-57.2 - "Design Requirements for Light Water Reactor Spent Fuel Storage Facilities at Nuclear Power Plants," American Nuclear Society, 1983.

20. Rosenkrantz W.A., Introduction to Probability and Statistics for Scientists and Engineers, McGraw-Hill, New York, NY, 1989.

21. ANSI/N 15.15-1974 - "Assessment of the Assumption of Normality," American Nation Standards Institute, New York, NY, 1974.

22. Owen, D.B., Handbook of Statistical Tables, Addison-Wesley, Reading, MA, 1962.

23. NUREG/CR-6979, "Evaluation of the French Haut Taux de Combustion (HTC) Critical Experiment Data," September 2008.

24. EMF-96-029(P)(A), "Reactor Analysis System for PWRs," January 1997.

25. BAW- 10180A, "NEMO-NODAL Expansion Method Optimized - Revision 1," March 1993.

26. US NRC "Safety Evaluation (SE) of Framatome ANP Topical Report BAW-10231 P, 'Copernic Fuel Rod Design Computer Code' (TAC NO. MA6792)," April 18, 2002, ML020070158.

27. S.F. Mughabghab, "Atlas of Neutron Resonances", (Fifth edition, ISBN-13: 978-0-444-52035-7) Elsevier BV, Amsterdam, The Netherlands, 2006.

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit APPENDIX A: KENO-V.A BIAS AND BIAS UNCERTAINTY The purpose of this analysis is to determine the statistical bias and associated uncertainty for the keff results calculated by the SCALE 4.4a computer code, based on criticality benchmark experiments typical of spent fuel pool geometry, fuel pins, absorbers, moderators, and reflectors. The scope of this report is limited to the validation of the KENO-V.a module and CSAS25 driver in the SCALE 4.4a code package for use with the 44 energy group cross-section library 44GROUPNDF5. These results were previously accepted in Reference [11]

(p. 20, Section 4.2), but have been updated to add three new cases, delete three cases, and update the statistics analysis.

This calculation is performed according to the general methodology described in Reference [7] (NUREG/CR-6698 "Guide for Validation of Nuclear Criticality Safety Methodology") that is also briefly described in Section A. 1. The critical experiments selected to benchmark the computer code system are discussed in Section A.3. The results of the criticality calculations, the trending analysis, the basis for the statistical technique chosen, the bias, and the bias uncertainty are presented in Sections A.4 through A.6. The area of applicability is documented in Section-A.8 and final results are surmnarized in Section A.9.

One perceived inadequacy in the selection of critical experiments described in Section A.3 is that they are lacking.

in higher actinide and fission product concentrations, which are typical of burned fuel assemblies (see Reference

[10]). This weakness raises the issue of whether or not the calculated bias and uncertainty summarized in Section A.9 are conservative for use in spent fuel pool criticality analysis, including the use of burnup credit. For 'further investigation, additional analysis.was performed using a selection of criticality benchmark cases representing significant actinide and fission product concentrations. These additional cases are described in Section A. I I and analytical results are presented in Sections A. 13 to A. 18. Final results for the actinide and fission product benchmarks are summarized in Section A. 19 and compared with the original results summarized in Section A.9; it is conclusively shown that the original results remain conservative. Therefore, the additional analyses described in Sections A. 10 through A. 19 supplement, but do not supercede the original analysis, described in Sections A. I through A.9.

A.1 Statistical Method for Determining the Code Bias As presented in Reference [7], the validation of the criticality code must use a statistical analysis to determine the bias and bias uncertainty in the calculation of k,ff. For each criticality benchmark experiment and kff calculation, the total uncertainty (ar) is defined as the statistical combination of the experimental (a,,p) and calculational (ocaic) uncertainties, as shown below.

Oat = OccOe The weighted-mean of keff(keff ), the variance about the mean (s2),and the average total uncertainty of the benchmark experiments (U2), are calculated using the weighting factors 1/aj 2,where ai is the total combined uncertainty (at) for the ith benchmark in the dataset (see Eq. 4, 5, and 6 in Reference [7]). Use of the weighting factors reduces the "weight" of data with higher uncertainty. Non-weighted results are also evaluated for comparison with those obtained by the weighted analysis. The variance about the mean (S2) and the average total experimental uncertainty (U2 ) are statistically combined to obtain the square root of the pooled variance (Sp),

defined as (Eq. 7 from Reference [7]):

SP = P 2 C-2 Page 50

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Determination of the kff bias and uncertainty requires evaluation of the distribution of data and investigation of possible trends. Trends are identified by regression analysis to determine key parameters including the slope, intercept, coefficient of detennination, the T-value associated with the Student's T-distribution, and a check for normality of the distribution of residuals in order to evaluate goodness-of-fit. These key parameters are used to establish the statistical significance of the calculated trend. If a trend is found to have statistical significance, then a one-sided lower tolerance band may be used to determine the bias and uncertainty. Both weighted and non-weighted trends are investigated. This method provides a fitted curve (KL(X)), above which 95% of the true population of keff is expected to lie, with a 95% confidence level.

If no trends of statistical significance are found and the data is normally distributed, then the bias and uncertainty can be based on a single-sided lower tolerance limit technique. This method defines a lower tolerance limit (KL) above which 95% of the true population of kff is expected to lie, with a 95% confidence level. The KL is defined in terms of the weighted-average of the data (k eff ), the 95/95 single-sided lower tolerance factor (C 9 5 /95 -

dependent on the size of the observed population), and the square-root of the pooled variance (Sp), as shown below.

KL = keff - C 95 / 95 Sp In this case, the statistical bias and uncertainty are defined as shown below.

Bias = keff - 1, forkeff -1, otherwise, Bias= 0 Uncertainty C95/95SP Finally, if the data is not normally distributed, then a nonparametric analysis can be employed. This method considers the size of the observed population and determines the mth lowest value (keffm < 1) and the associated uncertainty (m') to determine a limiting value (KL), above which 95% of the true population of keff is expected to lie, with a95% confidence level. Here, the sample size must exceed 59 in order to attain a 95/95 confidence interval, otherwise additional Non-Parametric Margin (NPM - defined by NUREG/CR-6698, see Reference [7])

must be included in the KL, as shown below.

KL = keffm Om - NPM Bias= keff m - 1 Uncerta int y = a m + NPM Regardless of the method employed, the Area of Applicability (AOA) must also be defined based on evaluation of key parameters of the criticality experiments that are included in the validation. Key parameters fall into three categories: materials, geometry, and neutron energy spectrum. In general, use of the criticality evaluation is restricted to the range of parameters identified in the AOA.

Page 51

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit A.2 Area of Applicability Required for the Benchmark Experiments The spent fuel pool at Palisades will primarily contain commercial nuclear fuel in uranium oxide pins in a square-pitched array. This fuel is characterized by the typical parameter values provided in Table A- 1. These typical values were used as primary criteria for selection of the appropriate benchmark experiments for determination of the code bias.

Table A-1: Range of Values of Key Parameters in Spent Fuel Pool Parameter Range of Values Fissile material UO2 rods Physical/Chemical Form Enrichment natural to 5.05 wt% U-235 Moderation/Moderator Heterogeneous/Water Lattice Square Pitch 1.2 to 1.45 cm Clad Zircaloy Soluble Boron Anticipated Absorber/Materials Stainless steel, Boron H/X ratio 0 to 445 Reflection Water, Stainless Steel Neutron Energy Spectrum (Energy of the 0.25 to 2.5 eV Average Lethargy Causing Fission)

Benchmark calculations have been generated based on selected critical experiments, chosen, in so far as possible, to bound the range of variables in the spent fuel rack designs. In spent fuel pool criticality analyses, the most significant physical parameters affecting criticality are:

" the fuel enrichment;

• the absorber materials; and,

" the lattice spacing.

Other parameters have a smaller effect but have also been included in the analysis. These physical parameters influence the spectral response, which is computed by KENO-V.a, as the EALF (Energy of the Average Lethargy causing Fission). The expected range of this parameter is also listed in Table A-I above.

Page 52

A ARE VA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit A.3 Description of the Criticality Experiments Selected The set of criticality benchmark experiments has been constructed to accommodate large variations in the range of parameters of the rack configurations and also to provide adequate statistics for accurate determination of the code bias. Thus, one hundred critical configurations were selected from various sources, including the International Handbook of Evaluated Criticality Safety Benchmark Experiments (Reference [17]), and previous validation analyses done with configurations from References [13], [14], [15], and [16].

Of the one-hundred criticality benchmarks, most (89) are lattices of low-enriched U0 2 fuel rods moderated by water with a range of moderating ratios (H/X) consistent with the AOA defined in Table A- 1. A set of 11 MOX benchmarks have also been included, in order to establish the functionality and validate the cross-section data of the major plutonium isotopes (Pu-239, Pu-240, Pu-241, and Pu-242). The data analysis will demonstrate that the MOX benchmark results impose no undue bias on the UO 2 results (see Section A.7). A brief description of the selected benchmark experiments, including the name of the SCALE 4.4a input files that have been constructed to model them, is presented in Table A-2. This table includes the references where a detailed description of the experiments and their experimental parameters are specified.

Table A-2: Descriptions of the Critical Benchmark Experiments Experiment Measured Cr exp Brief Description Neutron Absorber Reflector Case Name kf I I NUREG/CR-0073 PNL ex eriments (Reference [131), LEU-COMP-THERM-002 and -009 (Reference [171) c004 0.9997 0.0020 UO2 pellets with 4.31 wt% 23SU. None Water and acrylic c005b 1.0000 0.0021 Cluster of fuel rods on a 25.4 mm 0.625 cm Al plates plates as well as a c006b 1.0000 0.0021 pitch. Moderator; water or 0.625 cm Al plates biological shield c007a 1.0000 0.0021 borated water. 0.302 cm SS-304L serve as primary cOO8b 1.0000 0.0021 Various separation distances used plates reflector material.

c009b 1.0000 0.0021 between clusters. Those so 0.298 cm SS-304L A minor cOlOb 1.0000 0.0021 indicated have plates of neutron absorber plates with contribution comes cO1 lb 1.0000 0.0021 absorbing material poison placed 1.05 wt% or 1.62 from the channel c012b 1.0000 0.0021 between clusters of fuel rods. For wt% B that supports the c013b 1.0000 0.0021 additional details on the 0.485 cm SS-304L rod clusters and cOl4bmodels - - experiments and the computer used, see Reference 13 plates the 9.52steel carbon mm tank c029b 1.0000 0.0021 Zircaloy-4 absorber wall.

c03Ob 1.0000 0.0021 plates c03lb 1.0000 0.0021 BORAL absorber plates BAW-1484-7 experiments (Re"ference [14]), LEU-COMP-THERM-011 and -051 (Reference ((17,1) aclp 1 1.0010 0.0018 Enrichments of 2.459 wt% 235U None Water and aclp2 1.0009 0.0032 3x3 array of fuel clusters. 1037 ppm boron aluminum base aclp3 1.0009 0.0032 Various B 4C pins and stainless 764 ppm boron plate are the aclp4 1.0010 0.0017 steel and boron-aluminum sheets None primary reflective aclp5 1.0010 0.0017 were used as neutron absorbers. None materials in the aclp6 1.0010 0.0017 Cases so indicated also had None experiments.

aclp7 1.0010 0.0017 dissolved boron in the water None Minor contribution aclp8 1.0010 0.0017 moderator. None from the steel tank aclp9 1.0010 0.0018 None walls acp 10 1.0010 0.0020 143 ppm boron aclpl1a 1.0010 0.0024 510 ppm boron Page 53

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Experiment Measured a exp Brief Description Neutron Absorber Reflector Case Name k~ff aclpI lb 1.0010 0.0024 514 ppm boron ac lIc 1.0010 0.0024 501 ppm boron aclp I I d 1.0010 0.0024 493 ppm boron aclpI le 1.0010 0.0024 474 ppm boron aclplI f 1.0010 0.0024 462 ppm boron aclplI g 1.0010 0.0024 432 ppm boron aclp 12 1.0010 0.0019 217 ppm boron aclpl3 1.0010 0.0019 15 ppm boron aclpl3a 1.0010 0.0019 28 ppm boron aclp14 1.0010 0.0019 92 ppm boron aclp 17 1.0010 0.0024 487 ppm boron aclpl 8 1.0010 0.0020 197 ppm boron aclpl9 1.0010 0.0027 634 ppm boron aclp20 1.0010 0.0021 320 ppm boron aclp21 1.0010 0.0019 72 ppm boron IctO1 1c3 1.0009 0.0032 769 ppm boron Ict011 c5 1.0009 0.0032 762 ppm boron IctO0 Ic6 1.0009 0.0032 753 ppm boron BAW-1645-4 experiments (Reference 1151) 235 rcon01 1.0007 0.0006 2.46 wt% U. 435 ppm boron Water and rcon02 1.0007 0.0006 5x5 array of fuel cluster. Rod 426 ppm boron aluminum base rcon03 1.0007 0.0006 pitch between 1.2093 cm and 406 ppm boron plate are the rcon04 1.0007 0.0006 1.4097 cm. Cases so indicated 383 ppm boron primary reflective rcon05 1.0007 0.0006 also had dissolved boron in the 354 ppm boron materials in the rcon06 1.0007 0.0006 water moderator. 335 ppm boron experiments.

rcon07 1.0007 0.0006 361 ppm boron Minor contribution rcon09 1.0007 0.0006 886 ppm boron from the steel tank walls.

rconl0 1.0007 0.0006 871 ppm boron rconl1 1.0007 0.0006 852 ppm boron rconl2 1.0007 0.0006 834 ppm boron rconl3 1.0007 0.0006 815 ppm boron rcon 14 1.0007 0.0006 781 ppm boron rcon 15 1.0007 0.0006 746 ppm boron rcon 17 1.0007 0.0006 1156 ppm boron rconl78 1.0007 0.0006 1141 ppm boron rconl8 1.0007 0.0006 1123 ppm boron rcon219 1.0007 0.0006 1107 ppm boron rcon20 1.0007 0.0006 1093 ppm boron rcon21 1.000 0.0006 1068 ppm boron rcon28 1.0007 0.0006 121 ppm boron CEA Valduc Critical Mass Laboratory Experiments (Reference [161) mdisOl 1.0000 0.0014 4.75 wt% 235U. None The actual mdis02 1.0000 0.0014 CEA Valduc Critical Mass reflector mdis03 1.0000 0.0014 Laboratory experiments. A key boundaries vary mdis04 1.0000 0.0014 aspect of these experiments was from case to mdis05 1.0000 0.0014 to examine the reactivity effects case.

mdis06 1.0000 0.0014 of differing densities of mdis07 1.0000 0.0014 hydrogenous materials within a Page 54

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Experiment Measured a exp Brief Description Neutron Absorber Reflector Case Name krff mdis08 1.0000 0.0014 cross shaped channel box placed mdis09 1.0000 0.0014 between a two by two array of mdisl0 1.0000 0.0014 fuel rod assemblies. The mdisl 1 1.0000 0.0014 assemblies each consisted of an mdisl2 1.0000 0.0014 18 x 18 array of aluminum alloy mdisl3 1.0000 0.0014 clad UO 2 fuel pellet columns, mdisl4 1.0000 0.0014 The reader is referred to mdisl5 1.0000 0.0014 Reference [16] for a description mdisl6 1.0000 0.0014 of the critical mass experiments mdis17 1.0000 0.0014 and the computer models used mdisl8 1.0000 0.0014 ,for these validation cases.

mdisl8 1.0000 0.0014 _____________________________

mdis 19 1.0000 0.0014 LEU-COMP-THERM-022, -024, -025 E'x'periments (Reference-. 17 ,,, ,WI leuct022-02 1.0000 0.0046 9.83 and 7.41 wt% enriched None Water is the leuct022-03 1.0000 0.0036 U0 2 rods of varying numbers in primary reflector.

leuct024-01 1.0000 0.0054 hexagonal and square lattices in Minor leuct024-02 1.0000 0.0040 water moderator. contribution from leuct025-01 1.0000 0.0041 the steel tank leuct025-02 1.0000 0.0044 walls.

MIX-COMP-TIHERM-002,MOX Experiment ','(Reference '[171):: ... .... .........

epri70b 1.0009 0.0047 Experiments with mixtures of 687.9 ppm boron Reflected by water epri70un 1.0024 0.0060 natural UO2 -2wt%PuO2 (8%Pu- 1.7 ppm boron and Al.

epri87b 1.0024 0.0024 240). 1090.4 ppm boron epri87un 1.0042 0.0031 Square pitched lattices, with 0.9 ppm boron epri99b 1.0029 0.0027 1.778 cm, 2.2098 cm, and 767.2 ppm boron epri99un 1.0038 0.0025 2.5146 cm pitch in borated or 1.6 ppm boron pure water moderator.

IVIIA_-UIVI-l1 IIEIKVI-UU3 IVIUIA khxperiment (tteerence II "u saxtn 104 1.0000 0.0023 Experiments with mixtures of Reflected by water (case 6) natural UO 2-6.6wt%PuO, and Al.

saxtn56b 1.0000 0.0054 mixed-oxide (MOX), square-(case 3) pitched, partial moderator height saxtn792 1.0049 0.0027 lattices.

(case 5) Moderator: borated or pure saxton52 1.0028 0.0072 water moderator.

(case 1) saxton56 1.0019 0.0059 (case 2)

A.4 Results of Calculations with SCALE 4.4a The critical experiments described in Section A.3 were modeled with the SCALE 4.4a computer system. The resulting kcf and calculational uncertainty, along with the experimental keff and experimental uncertainty are tabulated in Table A-3. Parameters of interest in performing a trending analysis of the bias (including the EALF value calculated by SCALE 4.4a) are also listed in the table.

Page 55

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region I Criticality Evaluation with Burnup Credit Table A-3: Results for the Selected Benchmark Experiments Benchmark Values BecmrausValuesSCALE 4.4a Calculated EALF (eA) Enrichment Boron Boron)

(ppm No. Case Name keff cyp keff Vl es uv3 ___

1 c004 0.9997 0.0020 0.9966 0.0008 0.1126 4.31 0

• 255.92 2 cOO5b 1.0000 0.0021 0.9950 0.0008 0.1128 4.31 0 255.92 3 c006b 1.0000 0.0021 0.9964 0.0008 0.1130 4.31 0 255.92 4 c007a 1.0000 0.0021 0.9973 0.0009 0.1128 4.31 0 255.92 5 c008b 1.0000 0.0021 0.9966 0.0008 0.1135 4.31 0 255.92 6 c009b 1.0000 0.0021 0.9967 0.0008 0.1136 4.31 0 255.92 7 cO01b 1.0000 0.0021 0.9977 0.0008 0.1142 4.31 0 255.92 8 cOl1 b 1.0000 0.0021 0.9949 0.0009 0.1143 4.31 0 255.92 9 cO12b 1.0000 0.0021 0.9967 0.0008 0.1148 4.31 0 255.92 10 cO13b 1.0000 0.0021 0.9969 0.0008 0.1130 4.31 0 255.92 11 cO14b 1.0000 0.0021 0.9958 0.0008 0.1133 4.31 0 255.92 12 c029b 1.0000 0.0021 0.9972 0.0008 0.1126 4.31 0 255.92 13 c030b 1.0000 0.0021 0.9972 0.0009 0.1132 4.31 0 255.92 14 c031b 1.0000 0.0021 0.9993 0.0009 0.1144 4.31 0 255.92 15 ACLP1 1.0010 0.0018 0.9912 0.0007 0.1725 2.46 0 215.57 16 ACLP2 1.0009 0.0032 0.9951 0.0006 0.2504 2.46 1037 215.79 17 ACLP3 1.0009 0.0032 0.9958 0.0006 0.1963 2.46 764 215.83 18 ACLP4 1.0010 0.0017 0.9889 0.0008 0.1912 2.46 0 215.91 19 ACLP5 1.0010 0.0017 0.9906 0.0007 0.1660 2.46 0 215.87 20 ACLP6 1.0010 0.0017 0.9899 0.0009 0.1712 2.46 0 215.87 21 ACLP7 1.0010 0.0017 0.9891 0.0008 0.1496 2.46 0 215.87 22 ACLP8 1.0010 0.0017 0,9873 0.0007 0.1537 2.46 0 215.87 23 ACLP9 1.0010 0.0018 0.9908 0.0008 0.1409 2.46 0 215.87 24 ACLP10 1.0010 0.0020 0.9916 0.0007 0.1495 2.46 143 215.22 25 ACLP11A 1.0010 0.0024 0.9948 0.0007 0.1996 2.46 510 215.32 26 ACLP11B 1.0010 0.0024 0.9947 0.0007 0.1994 2.46 514 215.73 27 ACLP11C 1.0010 0.0024 0.9944 0.0006 .0.2019 2.46 501 215.32 28 ACLP11D 1.0010 0.0024 0.9952 0.0007 0.2028 2.46 493 215.14 29 ACLP11E 1.0010 0.0024 0.9940 0.0006 0.2037 2.46 474 214.70 30 ACLP11F 1.0010 0.0024 0.9932 0.0007 0.2050 2:46 462 214.52 31 ACLP11G 1.0010 0.0024 0.9954 0.0007 0.2045 2.46 432 215.97 32 ACLP12 1.0010 0.0019 0.9930 0.0008 0.1700 2.46 217 215.05 33 ACLP13 1.0010 0.0019 0.9933 0.0008 0.1965 2.46 15 215.67 34 ACLP13A 1.0010 0.0019 0.9902 0.0007 0.1981 2.46 28 215.91 35 ACLP14 1.0010 0.0019 0.9891 0.0008 0.2011 2.46 92 215.83 36 ACLP17 1.0010 0.0024 0.9899 0.0006 0.2053 2.46 487 215.89 37 ACLP18 1.0010 0.0020 0.9886 0.0008 0.1725 2.46 197 215.89 38 ACLP19 1.0010 0.0027 0.9912 0.0006 0.2061 2.46 634 215.89 39 ACLP20 1.0010 0.0021 0.9899 0.0007 0.1730 2.46 320 215.89 40 ACLP21 1.0010 0.0019 0.9883 0.0008 0.1532 2.46 72 216.19 41 IctOll case03 44grp 1.0009 0.0032 0.9962 0.0006 0.1960 2.46 769 216.41 42 IctO11 case05 .44grp 1.0009 0.0032 0.9960 0.0007 0.1971 2.46 762 216.42 43 IctOll case06 44grp 1.0009 0.0032 0.9959 0.0007 0.1989 2.46 753 216.40 44 RCON01 1.0007 0.0006 0.9997 0.0007 2.4282 2.46 435 17.41 45 RCON02 1.0007 0.0006 1.0004 0.0007 .2.4360 2.46 426 17.40 46 RCON03 1.0007 0.0006 0.9985 0.0008 2.4972 2.46 406 17.40 47 RCON04 1.0007 0.0006 0.9983 0.0007 2.4989 2.46 383 17.41 48 RCON05 1.0007 0.0006 1.0002 0.0007 2.4988 2.46 354 17.41 49 RCON06 1.0007 0.0006 0.9982 0.0007 2.5119 2.46 335 17.41 50 RCON07 1.0007 0.0006 0.9984 0.0006 1.6313 2.46 361 17.43 51 RCON09 1.0007 0.0006 0.9973 0.0007 1.4481 2.46 886 44.81 52 RCON10 1.0007 0.0006 0.9982 0.0008 1.4623 2.46 871 44.81 53 RCON11 1.0007 0.0006 0.9958 0.0007 1.5006 2.46 852 44.79 54 RCON12 1.0007 0.0006 0.9979 0.0007 1.4942 2.46 834 44.81 55 RCON13 1.0007 0.0006 0.9971 0.0006 1.4973 2.46 815 44.81 56 RCON14 1.0007 0.0006 0.9967 0.0007 1.5185 2.46 781 44.79 57 RCON15 1.0007 0.0006 0.9980 0.0006 1.5122 2.46 746 44.79 58 RCON16 1.0007 0.0006 0.9954 0.0006 0.4182 2.46 1156 118.47 59 RCON17 1.0007 0.0006 0.9963 0.0007 0.4293 2.46 1141 118.47 Page 56

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Benchmark Values SCALE 4.4a Calculated EALF Enrichment Boron No. CaseNoName Nm Cs keff kf apkeff Values cy-U-35 (eV) U-235) (ppm) H/X 60 RCON18 1.0007 0.0006 0.9929 0.0007 0.4354 2.46 1123 118.44 61 RCON19 1.0007 0.0006 0.9952 0.0007 0.4371 2.46 1107 118.44 62 RCON20 1.0007 0.0006 0.9952 0.0007 0.4367 2.46 1093 118.44 63 RCON21 1.0007 0.0006 0.9945 0.0007 0.4404 2.46 1068 118.44 64 RCON28 1.0007 0.0006 0.9970 0.0008 0.9984 2.46 121 17.44 65 MDIS01 1.0000 0.0014 0.9929 0.0008 0.2822 4.74 0 137.61 66 MDIS02 1.0000 0.0014 0.9862 0.0009 0.2641 4.74 0 137.61 67 MDIS03 1.0000 0.0014 0.9845 0.0009 0.2636 4.74 0 137.61 68 MDIS04 1.0000 0.0014 0.9895 0.0008 0.2513 4.74 0 137.61 69 MDIS05 1.0000 0.0014 0.9901 0.0009 0.2411 4.74 0 137.61 70 MDIS06 1.0000 0.0014 1.0010 0.0008 0.2292 4.74 0 137.61 71 MDIS07 1.0000 0.0014 0.9901 0.0009 0.2250 4.74 0 137.61 72 MDIS08 1.0000 0.0014 0.9858 0.0008 0.2493 4.74 0 137.61 73 MDIS09 1.0000 0.0014 0.9856 0.0009 0.2483 4.74 0 137.61 74 MDIS10 1.0000 0.0014 0.9928 0.0009 0.2221 4.74 0 137.61 75 MDIS11 1.0000 0.0014 1.0029 0.0009 0.2043 4.74 0 137.61 76 MDIS12 1.0000 0.0014 1.0080 0.0008 0.1946 4.74 0 137.61 77 MDIS13 1.0000 0.0014 0.9916 0.0009 0.1947 4.74 0 137.61 78 MDIS14 1.0000 0.0014 0.9887 0.0008 0.2299 4.74 0 137.61 79 MDIS15 1.0000 0.0014 0.9881 0.0010 0.2270 4.74 0 137.61 80 MDIS16 1.0000 0.0014 1.0015 0.0008 0.1905 4.74 0 137.61 81 MDIS17 1.0000 0.0014 0.9987 0.0008 0.1794 4.74 0 137.61 82 MDIS18 1.0000 0.0014 0.9961 0.0008 0.1747 4.74 0 137.61 83 MDIS19 1.0000 0.0014 0.9928 0.0009 0.1747 4.74 0 137.61 84 leuct022-02 1.0000 0.0046 1.0056 0.0013 0.2920 9.83 0 80.00 85 leuct022-03 1.0000 0.0036 1.0048 0.0013 0.1253 9.83 0 151.00 86 leuct024-01 1.0000 0.0054 0.9990 0.0015 1.0568 9.83 0 41.00 87 leuct024-02 1.0000 0.0040 1.0048 0.0014 0.1435 9.83 0 128.00 88 leuct025-01 1.0000 0.0041 0.9851 0.0014 0.4401 7.41 0 66.30 89 leuct025-02 1.0000 0.0044 0.9936 0.0013 0.2015 7.41 0 106.10 90 epri70b (PNL-31) 1.0009 0.0047 0.9995 0.0016 0.7631 0.71 688 146.15 91 epri70un (PNL-30) 1.0024 0.0060 0.9967 0.0015 0.5648 0.71 2 146.20 92 epri87b (PNL-33) 1.0024 0.0024 1.0046 0.0013 0.2780 0.71 1090 308.83 93 epri87un (PNL-32) 1.0042 0.0031 1.0034 0.0013 0.1894 0.71 1 308.99 94 epri99b (PNL-35) 1.0029 0.0027 1.0066 0.0009 0.1802 0.71 767 445.41 95 epri99un (PNL-34) 1.0038 0.0025 1.0088 0.0019 0.1353 0.71 , 2 445.57 96 saxtnl04 (case 6) 1.0000 0.0023 1.0056 0.0017 0.1001 0.71 0 473.11 97 saxtn56b (case 3) 1.0000 0.0054 0.9980 0.0019 0.6523 0.71 337 95.24 98 saxtn792 (case 5) 1.0049 0.0027 1.0027 0.0019 0.1547 0.71 0 249.70 99 saxton52 (case 1) 1.0028 0.0072 0.9987 0.0013 0.8878 0.71 0 73.86 100 saxton56 (case 2) 1.0019 0.0059 0.9997 0.0018 0.5450 0.71 0 95.29 In order to address situations in which the critical experiment being modeled was at other than a critical state (i.e.,

slightly super- or sub-critical), the calculated krff (ka.c) is normalized to the experimental k~ff (kCXp), using the following formula (Eq. 9 from Reference [7]):

k caic k norm -- k6 a k exp Page 57

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit This normalization does not affect the inherent bias in the calculation due to the very small differences in k~ff. In all following calculations, the normalized values of the kff were used in the determination of the code bias and bias uncertainty.

A.5 Trending Analysis The next step of the statistical methodology used to evaluate the code bias for the pool of experiments selected is to identify any trend in the bias (see Chapter 10 of Reference [20]). This is done by using the trending parameters presented in Table A-4.

Table A-4: Trending Parameters Energy of the Average Lethargy causing Fission, EALF (eV) 235 Fuel Enrichment (wt% U)

Atom ratio of the moderator to fuel (H/X)

Soluble Boron Concentration (ppm)

Fissile Isotopic Content, U-235, Pu-239 and Pu-241 (wt% fissile isotopes in HM)

• 2.57 wt% fissile isotopes in HM for MIXED-COMP-THERM-002

• 6.70 wt% fissile isotopes in HM for MIXED-COMP-THERM-003 Except for the fissile isotopic content for the MIXED-COMP-THERM benchmarks, which is obtained from Reference [ 17] (see Table A-4), the values of other parameters are tabulated in Table A-3. The regression analysis employs the nonnalized klff values (korm) and corresponding total uncertainty values (u), which are the values of the dependent variable and the corresponding weighting factors defined by I/a'2 , where cYi= at for the ith data point. Data points consist of the ordered pairs (xi,yi), where yj = kcff for the ith data point. Reference [7]

suggests the use of weighting factors to reduce the importance of data with higher uncertainty. For this application, the weighted trends will be evaluated and the results verified by comparison to the non-weighted trendingresults obtained directly from the Excel LINEST function.

The linear fitting function is defined as: yi = nixi + b, where m and b are the fitting coefficients, slope and intercept, respectively. The slope (in) and intercept (b) are determined by application of the following equations (from Reference [7], page 8):

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit m = !{ -:-*-Y 02 *. _ 7} 2 1b Z 1 xY, X-. Xi 'Y'I A l i 2'i ai 1 i 0' i i C2 i x 2 1

• 0. 9 9 5 2 5=keff For the residuals, there are n - 2 = 98 degrees of freedom, since there are n = 100 data points. The ith value of the regression is expressed as Yi = mxi + b and the weighted sums of the squares for the residuals (SSResiduaI), for the regression (SSRegrcssion), and for the total (SSTotal) are calculated as follows:

(Yi -- 9i) 2 z 2

• 1i Y

SSResiduai Y 2 SSRegression SSTotaI = SSResidual + SSRegression These, in turn, allow calculation of the goodness-of-fit parameters: coefficient of determination (r2), and the Tvalue corresponding to the Student's T-distribution:

r 2 = SSRegression SSTotal Tmva,,ue = n _2 SSRegression SSResidual Page 59

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit The r2 value represents the proportion of the sum of the squares for the y-values about their mean that can be attributed to a linear relation between x and y. The closer that r2 approaches a value of one, the better the fit of the data to the linear equation. Calculated Tvalucs are compared with the critical value of the Student's T-distribution with a significance level of n = 0.05/2 = 0.025 and n - 2 = 98 degrees of freedom, for which the Excel TINV function returns a value of 2.276. The null hypothesis for this test (H0), is that the slope is not statistically significant; thus, a statistically significant trend may exist if: ITValue I >-2.276 . Alternatively, the probability of obtaining a Tvaluc of larger magnitude from a two-tailed T-distribution with the same n - 2 = 98 degrees of freedom is calculated by the Excel TDIST function. In general, a low probability (e.g. p < 0.05) is necessary to confirm that a statistically significant trend exists.

In cases where a statistically significant trend is indicated by the Student's T-test, then the residuals of the regression are tested to determine if the error component is normally distributed with mean zero, which confirms that the statistical test for significance is valid. The Anderson-Darling test described in Reference [ 18] is employed for this purpose. The null hypothesis of normality is rejected if the value of the test statistic (A*)

exceeds the critical value of 0.752, at a significance level of 0.05. Therefore, if A* < 0.752, then the residuals are distributed normally and the statistical test for significance is valid.

Results of the weighted regression analysis and statistical tests are summarized in Table A-5 for all key parameters. In general, it can be seen that the slopes are very small and the correlations are relatively weak, suggesting that the linear trend is not sufficient to account for the variance in the dependent variable (kr.). If the statistical test (Tvauc) indicates a valid trend, however, and if the statistical test is determined to have validity, then the linear trend can be used to define a lower tolerance band. For further verification, non-weighted trending results were calculated using the Excel LINEST function; Table A-5 also summarizes key parameters of the non-weighted trending analysis, which generally confirm the results of the weighted trending analysis.

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-5: Summary of Trending Analysis Weighted Trend Parameter Valid Intercept Slope r2 IT-valuel P-value Goodness-of-fit Tests Trend Not passed, residuals EALF 0.99134 2.2407E-03 0.2195 5.25 8.85E-07 not normal (A*= 1.136) No (eV) and show a pattern -see Figure A-7.

Not passedTvalue is too Enrichment low indicating no

-5.3901E-04 0.0210 1.451 0.150 statistically significant No (wt% 23Su) 0.99685 trend.

Not passed, residuals H/X 0.99682 -1.4183E-05 0.0865 3.047 2.97E-03 not normal (A*=0.853) No and show a pattern -

see Figure A-8.

Boron in Not passed, T,.alue is too moderator 0.99458 1.3862E-06 0.0203 1.426 0.157 low indicating no No (ppm) statistically significant trend.

Fissile Isotopic Not passed, Tvalue is too Content (wt% 0.99582 -1.8893E-04 0.0025 0.500 0.618 low indicating no No fissile isotopes statistically significant in HM) trend.

Non-weighted Trend Parameter Not passed, residuals EALF 0.99401 1.7823E-03 0.0503 2.277 0.025 not normal (A*=].147) No (eV) and show a pattern -

see Figure A-9.

Not passed, Tvaiue is too Enrichment (wt% 23ru) 0.99426 1.8354E-04 0.0049 0.694 0.489 low indicating no lowtindicatigno No 2 5 (wt% 1.J)statistically significant trend.

Not passed, Tvalue is too H/X 0.99444 2.5753E-06 0.0022 0.468 0.641 low indicating no No statistically significant trend.

Boron in Not passed, Tvalue is too moderator 0.99453 1.2523E-06 0.0086 0.921 0.359 low indicating no No statistically significant (ppm) trend.

Fissile Isotopic Passed, residuals are Content (wt% 0.99193 7.8220E-04 0.0806 2.932 0.0042 distributed normally Yes fissile isotopes (A*=0.678) - see in HM) Figure A-10.

In general, the results of the trending analysis have shown very small slopes with no statistical validity, with the exception of the non-weighted trend for fissile isotopic content, suggesting that a single-sided lower tolerance band can be used to establish the bias and uncertainty as a function of this parameter. Although some trends are deemed statistically insignificant, lower tolerance bands are calculated for all variables and overlaid on the data plots to illustrate the effect.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure A- I through Figure A-5 illustrate the normalized keff dataset plotted as a function of each of the five independent variables examined in the weighted trending analysis. The plotted data is overlaid with the linear trend line and the lower tolerance band which bounds 95% of the population with a confidence level of 95%.

However, because the statistical significance of the weighted trends is inadequate, the lower tolerance bands do not adequately bound the data. Table A-5 also shows that the non-weighted fissile isotopic trend has statistical validity. Thus, Figure A-6 illustrates the non-weighted fissile isotopic trend. Plots of standardized residuals are shown in Figure A-7 and Figure A-8 for the weighted EALF and H/X trends. In addition, standardized residuals for the non-weighted trends of EALF and fissile isotopic content are plotted in Figure A-9 and Figure A- 10, respectively.

Figure A-I: Weighted Trend of kff versus EALF for the Benchmark Experiments 1.010 1.005

• a.

1.000 1.0

• C I. *

• C C v- =0.0022x + 0.9931 0.995 2 0 .1.*.

.0

• r =0.219 I

Z 4-0 C CC..

0.985 0.980 -

0.0 0.5 1.0 1.5 2.0 2.5 3.0 EALF (9V)

• Benchmark Data - Lower Tolerance Band -Weighted Unear Trend Page 62

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Bumup Credit Figure A-2: Weighted Trend of k.ff versus Enrichment (235U) for the Benchmark Experiments 1.010 1.005 1.000

• 0.995 0.990 0.985 0.980 0 2 3 4 5 6 7 8 9 10 Enrichment (%)

K

• Benchmark Data - LowrTol.ranc. Band Weighted Linear Trend Figure A-3: Weighted Trend of kff versus H/X for the Benchmark Experiments 1.010 1.005 1.000 0.995 0

z 0.990 0.985 0.980 0 50 100 150 200 250 300 350 400 450 500 Moderating Ratio, HIX

• ench*nrk Date - LowerTolerance Band -Mighted Linear Trend Page 63

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure A-4: Weighted Trend of keff versus Soluble Boron for the Benchmark Experiments 1.010 1.005 1.000 I S a.

• y: IE-06x+0.9946 2

L Sr 0.020 0.995-z0 0.990 0.985 -

0.9804 ______

0 200 400 600 800 1000 1200 1400 Boron (ppmB)

F

• Benchnark Data -Lower Tolerance Band Welghted Unear Trend ]

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Bumup Credit Figure A-5: Weighted Trend of kff versus Fissile Isotopic Content for the Benchmark Experiments 1.010 1.005 1.000 I S0.995

• oy ay- -0.0002x 0.9958 z

0.990 0.980 _____________

2 3 4 5 6 7 9 10 wt-% Fissile Isotopes In HM

. Benchmark Data _- Lower Tolerance Band -Weighted LlnearTrend Figure A-6: Non-weighted Trend of kff versus Fissile Isotopic Content for the Benchmark Experiments 2 3 4 6 7 8 9 10 wt-% Fissile Isotopes In HM I # Benchmark Data - Lower Tolerance Band - Linear Trend Page 65

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure A-7: Plot of Standard Residuals with EALF as Weighted Trending Parameter U

an EALF (eV)

Figure A-8: Plot of Standard Residuals with H/X as Weighted Trending Parameter 3

2 a,

o 4,2 2 20, Modrain20 io 3 3 0 0 5 Page 66

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit.

Figure A-9: Plot of Standard Residuals with EALF as Non-weighted Trending Parameter 0

EALF (eV)

Figure A-10: Plot of Standard Residuals with Fissile Isotopic Content as Non-weighted Trending Parameter wt-% Fissile Isotopes in HM Page 67

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Bumup Credit A.6 Bias and Bias Uncertainty For situations in which no significant trending in bias is identified, the statistical methodology presented in Reference [7] suggests to first check the distribution of the normalized kIff dataset. For this purpose, the D' Test of Normality described in Reference [21 ] is employed. The null hypothesis is that the dataset is distributed normally. The D' test is two-sided, therefore, for a significance level of a = 0.05, the critical values are determined by P = a/2 = 0.025 and P = 1 - a/2 = 0.975; the critical values are tabulated in Table 5 of Reference

[21] for various sample sizes. For a sample size of n = 100, the null hypothesis of normality is accepted if the test statistic satisfies the following relationship: 274.4 < D' < 286.0. Calculation of the test statistic shows that D' =

280.4, which falls between the critical values, therefore, the data is distributed normally.

A visual inspection of the normal probability plot of the normalized klff dataset provides further evidence that the data is distributed normally. Figure A- 11 shows the ordered dataset plotted versus the normal scores defined by the inverse of the standard normal cumulative probability distribution (see Section 8.4 of Reference [20]). From the equation of the linear trend line shown in Figure A- 11, the dataset has an approximate mean value of jt =

0.9948 and standard deviation of about a = 0.005, with a very high coefficient of determination, r2 = 0.9816.

Figure A-11: Normal Probability Plot for the Normalized kcff Dataset 1.010 1.005 1.000 o

I 0.995 0

0.990 0.985 0.980 ý-

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 Normal Scores Thus, the assumption of normality is validated allowing the application of a single-sided lower tolerance limit to determine the bias and uncertainty. For n = 100, the tolerance limit is C 95 /95 = 1.927, from Reference [22].

Results obtained for the weighted-average klff (keff ), the weighted-variance about the mean (S2), the average total uncertainty ( 2), and the square-root of the pooled variance (Sp), are shown below.

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A ARE VA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit y'2

- "0" 0. 9 9 5 2 3 = keff I (y oi )2 1i .i s2=

n lyz1 0Yi

-- 1.6921E - 05 U2 _ n =2.4030E - 06 Sp= Is = V/(1.6921E-05)+(2.4030E-06) = 0.00440 The corresponding non-weighted values are keff = 0.99484, s 2 = 2.5305E-05, (no change in 2,) and Sp.=

0.00526. Here, the non-weighted data is conservative because a larger bias and uncertainty will result. Thus, the bias and bias uncertainty are calculated as shown below.

Bias= keff - 1 = 0.99484- 1 -0.00516 Uncertainty = (C95/95)(Sp) = (1.927)(0.00526) = 0.01014 The corresponding lower tolerance limit is: KL = keff - (C 9 5/9 5)(Sp) = 0.99484 - 0.01014 = 0.98470. When this lower tolerance limit, KL = 0.98470, is compared with the lower tolerance bands of the trended data in Figure A-I through Figure A-6, the lower tolerance limit is conservative for all trended parameters.

A.7 Effect of Removal of the 11 MOX Benchmarks It is readily apparent from Figure A-5 and Figure A-6 that the MOX benchmarks on average have higher normalized ker values than the UO, benchmarks (data at 2.57 and 6.70 wt% fissile isotopes in HM). Indeed, this is shown by the calculation of separate averages, as shown below.

1 89 Yuo 2 = 9 EYi = 0.9 9 4 2 3 =keffU2 100 YMOX =

• Yi =0.99983 = ke.ff MOX i=90 The issue is whether the MOX benchmarks are unduly influencing the bias and lower tolerance limit in the non-conservative direction. First, the null hypothesis of normality is tested for the reduced sample size of n = 89 (UO 2 Page 69

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Bumup Credit only benchmarks). The critical values of the D' distribution with n = 89 are obtained from Table 5 of Reference

[21 ] and substituted into the following relationship, which must be satisfied to accept the null hypothesis of normality: 230.0 < D' < 240.3. Calculation of the test statistic shows that D' = 234.6, which falls between the critical values, therefore, the data is distributed normally.

A visual inspection of the normal probability plot of the normalized klff dataset provides further evidence that the data is distributed normally. Figure A- 12 shows the ordered dataset plotted versus the normal scores defined by the inverse of the standard normal cumulative distribution (see Section 8.4 of Reference [20]).

Figure A-12: Normal Probability Plot for the Normalized keff Dataset with n = 89 1.010 1.005 4 0 t 1.000 y = 0.0048x *-0.9942 o 2 0 r = 0.9787 0.995 0

0.990 0.985 0.980

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 Normal Scores Thus, the assumption of normality is validated allowing the application of a single-sided lower tolerance limit to determine the bias and uncertainty. For n = 89, the tolerance limit is C 95/95 = 1.946, from Reference [22]. Results obtained for the non-weighted-average keg ( keff ), the variance about the mean (S2), the average total uncertainty

( 2 ), and the square-root of the pooled variance (Sp), for the U0 2-only dataset are shown below.

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit 1Zyi = 0. 9 9 4 2 3 = ke n .

s2== i(Y i) 2 .3393E- 5 nI

-2 n 2 n -2.1808E -06 Y2 Sp= + = j(2.3393E-05)+(2.1808E-06) =0.00506' With this data, the bias and bias uncertainty are calculated as shown below.

Bias = ken - 1 = 0.99423 - 1 =-0.00577 Uncertainty = (C95/ 95)(Sp) = (1.946)(0.00506) = 0.00985 The corresponding lower tolerance limit is: KL = keff - (C 9 5 /95 )(Sp) = 0.99423 - 0.00985 = 0.98438. Thus, in comparison to the same results from the mixed dataset (n = 100), the bias is slightly larger in magnitude (0.00577 vs. 0.00516), while the uncertainty is slightly smaller (0.00985 vs. 0.01014), and, the lower tolerance limit is slightly lower, 0.98438 vs. 0.98470. The difference resulting from introduction of the 11 MOX cases is equivalent to 33 pcm in comparison with a KENO sampling uncertainty of approximately 80 pcm ((YENO =

0.0008); this difference is considered insignificant. Therefore, the conclusion that the 11 MOX cases introduce no significant non-conservatism is justified.

A.8 Area of Applicability for the Benchmark Experiments A brief description of the spectral and physical parameters characterizing the set of selected benchmark experiments is provided in Table A-6.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-6: Range of Values of Key Parameters in Benchmark Experiments Parameter Range of Values Geometrical shape Heterogeneous lattices; Rectangular and hexagonal Fuel type UO, rods MOX fuel rods Enrichment (for UO 2 fuel) 2.46 to 9.83 wt % 235U Rod pitch 1.04 to 2.6416 cm H/X 17.4 to 473 EALF 0.11 to 2.51 eV Absorbers Soluble boron Boron in plates Reflectors Water Stainless Steel Aluminum A.9 Bias Summary and Conclusions The mixed dataset of 100 criticality safety benchmarks experiments, 89 low-enriched U0 2, and 11 with MOX, were tested against the null hypothesis of normality and were found to be normally distributed. Thus, a parametric analysis was used to determine the bias and bias uncertainty, which resulted in a lower tolerance limit of KL = 0.98470. In addition, the set of 89 UO2-only benchmark results were also examined, and the change was determined to be insignificant; thus, inclusion of the 11 MOX benchmarks does not introduce any significant difference with respect to the U0 2-only analysis.

A standard trending analysis was also performed using linear regression analysis, including significance testing and goodness-of-fit evaluation. Five independent variables were examined: EALF (eV), enrichment (wt% U-235), moderating ratio (H/X), soluble boron concentration (ppm), and fissile isotopic content (wt% fissile isotopes in HM). Both weighted and non-weighted trends were evaluated. In general, the results of the trending analysis showed very small slopes with no statistical validity, except that the non-weighted trend for fissile isotopic content met the criteria for statistical validity. Although most trends were deemed statistically insignificant, lower tolerance bands were calculated for all variables and overlaid on the data plots to illustrate the effect.

When the lower tolerance limit, KL = 0.98470, is compared with the lower tolerance bands of the trended data, the KL is conservative for all trended parameters. Thus, the bias, bias uncertainty and corresponding lower tolerance limit are calculated as shown below.

Bias= keff - I = 0.99484-1 =-0.00516 Uncertainty = (C 95 /9 5 )(Sp) = (1.927)(0.00526) = 0.01014 KL = keff - (C 95/95)(Sp) = 0.99484 - 0.01014 = 0.98470 Page 72

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit The bias and its uncertainty (95/95 weighted single-sided tolerance limit) was obtained applying the appropriate steps of the statistical methodology presented in Reference [7] (NUREG/CR-6698) taking into account the possible trending of kff with various spectral and/or physical parameters. These results are intended to support the criticality analysis of the Palisades spent fuel pool.

A.1O Additional Analyses This and subsequent sections A. 11 through A. 19 supplement, but do not replace the analysis and results described in Sections A.2 through A.9. The supplemental analysis is performed using a selection of criticality benchmark cases representing significant actinide and fission product concentrations to address a perceived inadequacy in the selection of critical experiments described in Section A.3. The actinide and fission product benchmarks are described in Section A. 11 and analytical results are presented in Sections A. 13 to A. 18. Final results for the actinide and fission product benchmarks are summarized in Section A. 19 and compared with the original results summarized in Section A.9; it is conclusively shown that the original results remain conservative.

In NUREG/CR-6979 Reference [23], Oak Ridge National Laboratory provided an evaluation of the French HTC (Haut Taux de Combustion - French acronym for high burnup) experiments, which determined (with few exceptions) that they are suitable criticality benchmarks. These experiments involved fuel pins in square lattices of array sizes up to 50 x 50, with water moderation and various pin pitches, absorbers, and reflector materials.

For the HTC experiments, the fuel pellets contained a mixture of uranium and plutonium oxides, with isotopic concentrations representative of 4.5% enriched PWR fuel burned to 37.5 GWD/MTU, but without any fission products. The experiments were performed in four phases:

" Phase 1 comprises 18 cases with pure water moderation and various array sizes and pin pitches.

" Phase 2 comprises 20 cases with dissolved gadolinium in water solution, and 21 cases with dissolved boron in water moderator; these cases involve a variety of array sizes and pin pitches.

• Phase 3 comprises 26 cases of various array sizes separated into 2x2 sub-arrays by water gaps of varying width; some cases include absorber plates of various materials placed in the water gaps.

" Phase 4 is similar to Phase 3, but with thick lead or steel shielding material surrounding the fuel pin array, with a total of 71 cases.

Thus, there are a total of 156 experimental cases designed to approximate fuel handling, storage rack, and spent fuel cask conditions providing a basis for validation of criticality results, which are particularly applicable for methods that use actinides for burnup credit. However, eleven cases are rejected on the basis of the ORNL assessment and these will not be included in the bias determination; leaving 145 HTC cases. Of the eleven cases, three are from Phase 3 and the remaining eight are from Phase 4. All of the rejected cases were designed to have zero water gap between poison panels attached to adjacent assemblies, but the calculated k1ff values reported in Reference [23] were higher than those calculated for cases with water-filled gaps between the assemblies. These results are indicative of some discrepancy between the actual experimental configuration and the analytic model; therefore, the results are rejected based on the recommendation of ORNL.

While the fuel pellets in the HTC experiments incorporated certain of the major actinides to simulate burned fuel, no actual fission products were represented. Thus, in order to evaluate the effect of certain fission products, three additional sets of fission product criticality benchmarks described in the International Handbook of Evaluated Criticality Safety Benchmark Experiments, Reference [ 17], were selected:

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit

• LEU-MISC-THERM-005 comprises 12 critical configurations of low-enriched UO 2 fuel rods partially submerged in a solution of uranyl-nitrate which is poisoned with certain pseudo-fission-product elements:

samarium, cesium, rhodium, and europium.

• LEU-COMP-THERM-050 comprises 18 critical configurations of low-enriched U0 2 fuel rods partially covered with water, serving as both moderator and reflector. At the center of the fuel rod array is a Zircaloy tank containing a solution of Sm-149, which occupies 5x5=25 lattice positions. Eleven of the 18 experiments involve various concentrations of Sm-149 in solution with various fuel array sizes. Seven additional experiments were performed with natural boron solutions or with pure water in the Zircaloy tank.

LEU-COMP-THERM-079 comprises 10 critical configurations of low-enriched UO 2 fuel rods arranged in a triangular pitched array, and partially covered with water to provide both reflection and moderation.

Certain of the fuel rods could be opened to allow placement of rhodium foils between the fuel pellets.

The number and thicknesses of the rhodium foils varies as the array size is also varied.

With the addition of the 40 fission product benchmark experiments and the 145 remaining HTC cases, there are a total of 185 criticality benchmarks for the verification analysis. It was ultimately determined, however, that the LEU-MISC-THERM-005 experiments could not be analyzed appropriately with the standard SCALE 4.4a protocol used for modeling typical spent fuel pool rack geometries. This determination reduces the total number of cases from 185 to 173, which are included in the statistical analysis to establish the criticality bias and the applicable uncertainty.

Of the 145 HTC cases that remain, some may be considered less applicable than others in terms of spent fuel pool criticality analysis. For instance, the 20 cases in Phase 2 which employ dissolved gadolinium may not be directly applicable. In addition, the 63 cases remaining in Phase 4 with lead or steel reflectors are more applicable to storage cask modeling. Removal of these cases would reduce the remaining number of the HTC cases to 62; those which are most directly applicable to spent fuel pool analysis. However, retention of all 145 cases is beneficial in demonstrating the versatility and robustness of the code for handling a wider range of material, geometry, and spectral challenges, which is also the reason for including the fission product benchmarks.

Initially, data from the HTC and fission product benchmarks will be compared with the original database described in Section A.3. These comparisons will help to determine whether to treat the HTC and fission product cases separate from the original database, or whether to pool all the data together. Finally, the effect of eliminating the 83 HTC cases which are deemed less applicable will also be evaluated in Section A. 17.

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A AREVA Document No.: ANP-2858NP-003 Palisades SEP Region 1 Criticality Evaluation with Burnup Credit A.11 Description of the HTC and Fission Product Experiments Detailed descriptions of the HTC criticality experiments are found in Reference [23]. For these experiments, the fuel columns are 90 cm in length, and contain a mixture of uranium and plutonium oxides whose isotopic concentrations are representative of 4.5% enriched PWR fuel burned to 37.5 GWD/MTU, but without any fission products. Zircaloy-4 is the fuel pin cladding material. For Phase 1, all pins are arranged in square lattices with pitches varying from 1.3 to 2.3 cm, where each individual experiment uses a single pin pitch. For each experiment, the number of pins varies from 600 (in a 25x24 array) to 2500 (in a 50x50 array). The fuel lattice is placed inside a tank and partially submerged under water; criticality is controlled by adjusting the water height to obtain near-critical conditions. Phase 1 includes 18 cases with experimental parameters that are summarized in Table A-7; the tabulated EALF (Energy of the Average Lethargy causing Fission) values are those calculated by KENO-V.a.

Table A-7: HTC Phase 1 Experimental Parameters Pin Gad. Boron Assy. Refl.

Case Experiment ch o. n Absorber Reflector Rap Number Numberime t (cm)b(g/l)

Ratio e Conc. Conc. Gap Material Material Gap

( (cm) (cm) 1 2327 2.3 1149 0.069 0 0 0 None Water 0 2 2335 2.3 1150 0.066 0 0 0 None Water 0 3 2336 2.3 1150 0.066 0 0 0 None Water 0 4 2337 1.9 728 0.085 0 0 0 None Water 0 5 2339 1.9 728 0.083 0 0 0 None Water 0 6 2340 1.9 728 0.082 0 0 0 None Water 0 7 2341 1.7 547 0.103 0 0 0 None Water 0 8 2342 1.7 547 0.101 0 0 0 None Water 0 9 2343 1.7 547 0.100 0 0 0 None Water 0 10 2345 1.5 387 0.143 0 0 0 None Water 0 11 2347 1.5 387 0.138 0 0 0 None Water 0 12 2348 1.5 387 0.136 0 0 0 None Water 0 13 2349 1.3 246 0.267 0 0 0 None Water 0 14 2352 1.3 246 0.243 0 0 0 None Water 0 15 2353 1.3 246 0.239 0 0 0 None Water 0 16 2355 1.7 547 0.102 0 0 0 None Water 0 17 2357 1.7 547 0.100 0 0 0 None Water 0 18 2361 1.7 547 0.102 0 0 0 None Water 0 Phase 2 is similar to Phase 1 except that the pin pitches vary from 1.3 to 1.9 cm and the number of pins varies from 784 (in a 28x28 array) to 2500 (in a 50x50 array). Water serves as both moderator and reflector, containing either dissolved natural gadolinium or dissolved natural boron as an absorber material. As in Phase 1, criticality is controlled by adjusting the water height to obtain near-critical conditions. There are 20 cases using dissolved gadolinium in the moderator, and 21 cases using dissolved boron. Table A-8 summarizes the experimental parameters from the 41 cases included in Phase 2; the tabulated EALF values are those calculated by KENO-V.a..

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-8: HTC Phase 2 Experimental Parameters Gad. Pin RadeBroi.sy Case Experiment H/X EALF Gad. Boron Assy. Absorber Reflector Refl.

Number Pitch Ratio e Conc. Conc. Gap Material Material Gap Number (cm) (g/l) (g/l) (cm) (cm) 1 2405 1.3 247 0.263 0.052 0 0 Gad. Soln. Water 0 2 2406 1.3 247 0.258 0.052 0 0 Gad. Soln. Water 0 3 2407 1.3 247 0.281 0.100 0 0 Gad. Soln. Water 0 4 2408 1.3 247 0.278 0.099 0 0 Gad. Soln. Water 0 5 2409 1.3 247 0.273 0.099 0 0 Gad. Soln. Water 0 6 2410 1.3 247 0.296 0.151 0 0 Gad. Soln. Water 0 7 2411 1.3 247 0.289 0.148 0 0 Gad. Soln. Water 0 8 2412 1.3 247 0.307 0.200 0 0 Gad. Soln. Water 0 9 2415 1.3 247 0.303 0.197 0 0 Gad. Soln. Water 0 10 2417 1.5 387 0.173 0.196 0 0 Gad. Soln. Water 0 11 2419 1.5 387 0.165 0.147 0 0 Gad. Soln. Water 0 12 2420 1.5 387 0.164 0.147 0 0 Gad. Soln. Water 0 13 2422 1.5 387 0.157 0.098 0 0 Gad. Soln. Water 0 14 2423 1.5 387 0.155 0.098 0 0 Gad. Soln. Water 0 15 2425 1.5 387 0.150 0.048 0 0 Gad. Soln. Water 0 16 2427 1.5 387 0.147 0.048 0 0 Gad. Soln. Water 0 17 2430 1.7 548 0.107 0.048 0 0 Gad. Soln. Water 0 18 2434 1.9 729 0.088 0.048 0 0 Gad. Soln. Water 0 19 2436 1.7 548 0.114 0.097 0 0 Gad. Soln.

• Water 0 20 2433 1.7 548 0.107 0.048 0 0 Gad. Soln. Water 0 Boron Pin RedfBroiAsy Case Experiment Pin H/X EALF Gad. Boron Assy. Absorber Reflector Refl.Ga Cs Nubr Pitch Rai Cone. Conc. Gap Material Mtra a NNumber umber (cm)Ratio (eV) g (g/) (cm) Material (cm) 1 2437 1.3 247 0.257 0 0.100 0 Bor. Soln. Water 0 2 2438 1.3 247 0.254 0 0.106 0 Bor. Soln. Water 0 3 2441 1.3 247 0.266 0 0.205 0 Bor. Soln. Water 0 4 2444 1.3 247 0.274 0 0.299 0 Bor. Soln. Water 0 5 2446 1.3 247 0.286 0 0.400 0 Bor. Soln. Water 0 6 2447 -1.3 247 0.283 0 0.399 0 Bor. Soln. Water 0 7 2448 1.3 247 0.293 0 0.486 0 Bor. Soln. Water 0 8 2449 1.3 247 0.300 0 0.587 0 Bor. Soln. Water 0 9 2459 1.5 387 0.171 0 0.595 0 Bor. Soln. Water 0 10 2468 1.5 388 0.164 0 0.499 0 Bor. Soln. Water 0 11 2470 1.5 387 0.160 0 0.393 0 Bor. Soln. Water 0 12 2471 1.5 387 0.154 0 0.295 0 Bor. Soln. 'Water 0 13 2473 1.5 387 0.148 0 0.200 0 Bor. Soln. Water 0 14 2475 1.5 387 0.143 0 0.089 0 Bor. Soln. Water 0 15 2478 1.7 548 0.104 0 0.090 0 Bor. Soln. Water 0 16 2483 1.7 548 0.108 0 0.194 0 Bor. Soln. Water 0 17 2485 1.7 548 0.112 0 0.286 0 Bor. Soln. Water 0 18 2487 1.7 548 0.117 0 0.415 0 Bor. Soln. Water 0 19 2482 1.7 548 0.106 0 0.100 0 Bor. Soln. Water 0 20 2490 1.9 730 0.090 0 0.220 0 Bor. Soln. Water 0 21 2492 1.9 1 730 0.086 1 0 0.110 0 Bor. Soln. Water 0 Phase 3 of the HTC criticality experiments considers the effects of inter-assembly gap width and of various absorber plates located in the inter-assembly gaps. Phase 3 cases consist of a 2x2 array of fuel assemblies with a Page 76

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region'1 Criticality Evaluation with Burnup Credit fixed 1.6 cm pin pitch, using the same fuel pins previously described for Phases 1 and 2. Experimental configurations without absorber plates examine the effects of inter-assembly gaps from zero to 18 cm, and assembly fuel rod array sizes of 25x25 to 13x 13. Configurations with absorber plates consider the effects of inter-assembly gaps for 25x25 and 25x24 rod assemblies with borated stainless steel, BORALO (borated aluminum), or cadmium/SS (Cd/SS) absorber plates. Phase 3 includes 26 cases with experimental parameters that are summarized in Table A-9; the tabulated EALF values are those calculated by KENO-V.a.

Table A-9: HTC Phase 3 Experimental Parameters Case Experiment Pin H/X EALF Gad. Boron Assy. Absorber Reflector Refl.

Number Number c Ratio e Conc. Conc. Gap Material Material (cm) ( (g/l) (g/I) (cm) (cm) 1 2518 1.6 466 0.125 0 0 3.5 B-SS Water 0 2

• 2520 1.6 466 0.143 0 0 0.0 B-SS Water 0 3 2521 1.6 466 0.131 0 0 2.0 B-SS Water 0 4 2522 1.6 466 0.126 0 0 3.0 B-SS Water 0 5 2523 1.6 466 0.137 0 0 1.0 B-SS Water 0 6* 2514 1.6 466 0.132 0 0 0.0 BORAL"' Water 0 7 2511 1.6 466 0.131 0 0 2.0 Cd/SS Water 0 8* 2524 1.6 466 0.141 .0 0 0.0 Cd/SS Water 0 9 2525 1.6 466 0.135 0 0 1.0 Cd/SS Water -0 10 2526 1.6, 466 0.131 0 0 1.5 Cd/SS Water 0 11 2527 1.6 466 0.139 0 0 0.5 Cd/SS Water 0 12 2509 1.6 466 0.114 0 0 18.0 None Water 0 13 2531 1.6 466 0.113 0 0 14.5 None Water 0 14 2532 1.6 466 0.113 0 0 11.0 None Water 0 15 2533 1.6 466 0.112 0 0 10.0 None Water 0 16 2534 1.6 466 0.112 0 0 9.0 None Water 0 17 2535 1.6 466 0.110 0 0 8.0 None Water 0 18 2536 1.6 466 0.107 0 0 6.0 None Water 0 19 2537 1.6 466 0.105 0 0 4.0 None Water 0 20 2538 1.6 466 0.103 0 0 4.0 None Water 0 21 2539 1.6 466 0.106 0 0 2.0 None Water 0 22 2541 1.6 466 0.108 0 0 1.0 None Water 0 23 2544 1.6 466 0.116 0 0 0.0 None Water 0 24 2547 1.6 466 0.154 0 0 0.0 None Water 0 25 2548 1.6 466 0.129 0 0 4.0 None Water 0 26 2549 1.6 466 0.117 0 0 10.0 None Water 0 Cases 2, 6, and 8 are not recommended for inclusion in criticality benchmark calculations (ORNL - see Reference [23]).

Phase 4 of the HTC criticality experiments is similar to Phase 3, except with thick lead or steel reflector plates placed around the outside of the 2x2 fuel assembly array. Experimental configurations without absorber plates examine the effects of inter-assembly gaps from zero to 12 cm, and reflector plate gaps of zero to 2 cm.

Configurations with absorber plates consider the effects of inter-assembly gaps from zero to 3.5 cm with borated stainless steel (B-SS), BORAL', or cadmium/SS (CdISS) absorber plates, and reflector plate gaps of zero to 2 cm.

Phase 4 includes 38 cases with lead reflector plates and 33 additional cases with steel reflector plates.

Experimental parameters for each case are summarized in Table A-10; the tabulated EALF values are those calculated by KENO-V.a.

Page 77

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-1O: HTC Phase 4 Experimental Parameters Lead CaePitchCoc Experiment Pin H/X EALF Gad. Boron Co. Assy.

Ga Absorber Reflector Refl.

Case Number e Con. Cone. Gap Material Material Gap Number (cm) Ratio (eV) (g/I) (g/I) (cm) (cm) 1* 2562 1.6 466 0.156 0 0 0.0 B-SS Lead 0.0 2 2563 1.6 466 0.153 0 0 0.5 B-SS Lead 0.0 3 2564 1.6 466 0.149 0 0 1.0 B-SS Lead 0.0 4 2565 1.6 466 0.145 0 0 1.5 B-SS Lead 0.0 5 2566 1.6 466 0.141 0 0 2.0 B-SS Lead 0.0 6 2567 1.6 466 0.136 0 0 3.0 B-SS Lead 0.0 7 2568 1.6 466 0.134 0 0 3.5 B-SS Lead 0.0 8 2569 1.6 466 0.141 0 0 2.0 B-SS Lead 0.5 9 2570 1.6 466 0.139 0 0 2.0 B-SS Lead 1.0 10 2571 1.6 466 0.138 0 0 2.0 B-SS Lead 1.5 11 2572 1.6 466 0.137 0 0 2.0 B-SS Lead 2.0 12

• 2586 1.6 466 0.137 0 0 0.0 BORAL' Lead 0.0 13

• 2587 1.6 466 0.137 0 0 0.0 BORAL' Lead 0.0 14

• 2588 1.6 466 0.136 0 0 0.0 BORAL' Lead 0.5 15 2624 1.6 466 0.132 0 0 1.0 BORAL' Lead 0.0 16 2625 1.6 466 0.135 0 0 0.5 BORAL-k' Lead 0.0 17

• 2577 1.6 466 0.152 0 0 0.0 Cd/SS Lead 0.0 18 2578 1.6 466 0.145 0 0 1.0 Cd/SS Lead 0.0 19 2579 1.6 466 0.138 0 0 2.0 Cd/SS Lead 0.0 20 2580 1.6 466 0.135 0 0 2.5 Cd/SS Lead 0.0 21 2581 1.6 466 0.137 0 0 2.0 Cd/SS Lead 0.5 22 2582 1.6 466 0.135 0 0 2.0 Cd/SS Lead 1.0 23 2583 1.6 466 0.134 0 0 2.0 Cd/SS Lead 1.5 24 2584 1.6 466 0.133 0 0 2.0 Cd/SS Lead 2.0 25 2621 1.6 466 0.132 0 0 3.0 Cd/SS Lead 0.0 26 2622 1.6 466 0.130 0 0 3.5 Cd/SS Lead 0.0 27 2550 1.6 466 0.180 0 0 0.0 None Lead 0.0 28 2551 1.6 466 0.170 0 0 1.0 None Lead 0.0 29 2552 1.6 466 0.162 0 0 2.0 None Lead 0.0 30 2553 1.6 466 0.147 0 0 4.0 None Lead 0.0 31 2554 1.6 466 0.137 0 0 6.0 None Lead 0.0 32 2555 1.6 466 0.131 0 0 8.0 None Lead 0.0 33 2556 1.6 466 0.127 0 0 10.0 None Lead 0.0 34 2557 1.6 466 0.125 0 0 12.0 None Lead 0.0 35 2558 1.6 466 0.160 0 0 2.0 None Lead 0.5 36 2559 1.6 466 0.158 0 0 2.0 None Lead 1.0 37 2560 1.6 466 0.157 0 0 2.0 None Lead 1.5 38 2561 1.6 466 0.156 0 0 2.0 None Lead 2.0 Page 78

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-1O: HTC Phase 4 Experimental Parameters (cont'd)

Steel Experiment Pin H/X EALF Gad. Boron Assy. Absorber Reflector Refl.

Case Number Pitch Ratio (eV) Cone. Cone. Gap Material Material Gap Number (cm) ( (g/I) (g/I) (cm) (cm) 1* 2602 1.6 466 0.156 0 0 0.0 B-SS Steel 0.0 2 2603 1.6 466 0.153 0 0 0.5 B-SS Steel 0.0 3 2604 1.6 466 0.149 0 0 1.0 B-SS Steel 0.0 4 2605 1.6 466. 0.145 0 0 1.5 B-SS Steel 0.0 5 2606 1.6 466 0.142 0 0 2.0 B-SS Steel 0.0 6 2607 1.6 466 0.141 0 0 2.0 B-SS Steel 0.5 7 2608 1.6 466 0.139 0 0 2.0 B-SS Steel 1.0 8 2609 1.6 466 0.138 0 0 2.0 B-SS Steel 1.5 9 2610 1.6 466 0.137 0 0 2.0 B-SS Steel 2.0 10 2611 1.6 466 0.137 0 0 3.0 B-SS Steel 0.0 11 2612 1.6 466 0.134 0 0 3.5 B-SS Steel 0.0 12

• 2589 1.6 466 0.137 0 0 0.0 BORAL0 Steel 0.0 13 2626 1.6 466 0.135 0 0 0.5 .BoRAL'91 Steel 0.0 14

• 2613 1.6 466 0.153 0 0 0.0 Cd/SS Steel 0.0 15 2614 1.6 466 0.146 0 0 1.0 Cd/SS Steel 0.0 16 2615 1.6 466 0.139 0 0 2.0 Cd/SS Steel 0.0 17 2616 1.6 466 0.138 0 0 2.0 Cd/SS Steel 0.5 18 2617 1.6. 466 0.136 0 0 2.0 Cd/SS Steel 1.0 19 2618 1.6 466 0.135 0 0 2.0 Cd/SS Steel 1.5 20 2619 1.6 466 0.134 0 0 2.0 Cd/SS Steel 2.0 21 2620 1.6 466 0.136 0 0 2.5 Cd/SS Steel 0.0 22 2590 1.6 466 0.179 0 0 0.0 None Steel 0.0 23 2591 1.6 466 0.171 0 0 1.0 None Steel 0.0 24 2592 1.6 466 0.162 0 0 2.0 None Steel 0.0 25 2593 1.6 466 0.160 0 0 2.0 None Steel 0.5 26 2594 1.6 466 0.159 0 0 2.0 None Steel 1.0 27 2595 1.6 466 0.158 0 0 2.0 None Steel 1.5 28 2596 1.6 466, 0.157 0 0 2.0 None Steel 2.0 29 2597 1.6 466 0.147 0 0 4.0 None Steel 0.0 30 2598 1.6 466 0.136 0 0 6.0 None Steel 0.0 31 2599 1.6 466 0.130 0 0 8.0 None Steel 0.0 32 2600 1.6 466 0.127 0 0 10.0 None Steel 0.0 33 2601 1.6 466 0.125 0 0 12.0 None Steel 0.0 Cases 1, 12 - 14, and 17 with the lead reflector, and cases 1, 12, and 14 with the steel reflector, are not recommended for inclusion in criticality benchmark calculations (ORNL - see Reference [23]).

Page 79

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit The LEU-MISC-THERM-005 fission product experiments include 12 critical configurations consisting of 333 UO 2 fuel rods enriched to 5% U-235 and arranged in a 1.50 cm square-pitched lattice; detailed descriptions of the various cases are provided in Reference [ 17]. For each experiment, the fuel array is partially submerged in a solution of uranyl-nitrate with a uranium enrichment of 6% U-235. Added to the uranyl-nitrate solution, are certain pseudo-fission-product elements: samarium, cesium, rhodium, and europium. While the isotopic composition of the pseudo-fission-product elements is natural, some fission product nuclides are present.

Chemical concentrations of the pseudo-fission-products were adjusted to simulate a burnup of 30 GWD/MTU.

Varying combinations of pseudo-fission-products are introduced for each experiment and criticality is controlled by adjusting the solution height to obtain near-critical conditions.

The focus of these experiments is the application of burnup credit to fuel reprocessing operations. Therefore, the applicability to spent fuel pool criticality analysis may be questionable. Nonetheless, the cases were run and SCALE 4.4a calculational results are summarized in Table A- 11; the tabulated EALF values are those calculated by KENO-V.a. It was concluded that the analysis gave results not suitable for use in determining the code bias; all are about 1% Ak/k less than the nominal value of 1.000. This is due to the use of the Nordheim Integration Method in NITAWL for processing resonances in the 44-group ENDF-V data. The assumptions used by NITAWL do not allow it to handle a mixed heterogeneous fissile material problem. Therefore, Table A-1I1 results cannot be used to determine a code bias for situations where SCALE4.4a is used with the NITAWL cross-section processor.

Table A-11: SCALE 4.4a Results for LEU-MISC-THERM-005 Benchmarks Case Number Calculated kff Calculated a EALF (eV) 1 0.9900 0.0003 0.117 2 0.9907 0.0003 0.118 3 0.9906 0.0003 0.120 4 0.9908 0.0003 0.120 5 0.9909 0.0003 0.120 6 0.9913 0.0003 0.120 7 0.9909 0.0003 0.121 8 0.9907 0.0003 0.121 9 0.9912 0.0003 0.121 10 0.9909 0.0003 0.121 11 0.9901 0.0003 0.121 12 0.9903 0.0003 0.121 Page 80

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation withBurnup Credit The LEU-COMP-THERM-050 fission product experiments include 18 critical configurations consisting of low-enriched (4.738% U-235) UO, fuel rods arranged in a 1.30 cm square-pitched lattice partially covered with water, serving as both moderator and reflector. Criticality is controlled by adjusting the water level to obtain near-critical conditions. At the center of the fuel rod array is a Zircaloy tank containing a solution of Sm-149, which occupies 5x5=25 lattice positions. Eleven experiments involve various concentrations of Sm- 149 in solution with various fuel array sizes. Five additional experiments were performed with natural boron solutions of various concentrations in the Zircaloy tank, and with various fuel array sizes. Two more were performed with pure water in the Zircaloy tank. Detailed descriptions of the various cases are provided in Reference [17], where the maximum calculated reactivity worth of the Sm-149 or boron solution is on the order of 5.3% Ak/k. Here again, the geometry is rather non-representative of a spent fuel pool criticality analysis, but the cases were run to test the ability of the code and cross-section library to accurately evaluate criticality with significant absorption by samarium. Experimental parameters for each case are summarized in Table A-12; the tabulated EALF values are those calculated by KENO-V.a.

Table A-12: LEU-COMP-THERM-050 Experimental Parameters CasePin X EALF Sm-149 Boron Name Pitch (c)Ratio (eV)(gl Concentration Concentration (cm) (g/l) (g/1)

LCT-050-1 1.3 122 0.204 0 0 LCT-050-2 1.3 122 0.195 0 0 LCT-050-3 1.3 122 0.213 0 0.822 LCT-050-4 1.3 122 0.202 0 0.822 LCT-050-5 1.3 122 0.228 0 5.03 LCT-050-6 1.3 122 0.219 0 5.03 LCT-050-7 1.3 122 0.214 0 5.03 LCT-050-8 1.3 122 0.213 0.1048 0 LCT-050-9 1.3 122 0.201 0.1048 0 LCT-050-10 1.3 122 0.199 0.1048 0 LCT-050-1 1. 1.3 122 0.221 0.2148 0 LCT-050-12 1.3 122 0.208 0.2148 0 LCT-050-13 1.3 122 0.205 0.2148 0 LCT-050-14 1.3 122 0.214 0.6262 0 LCT-050-15 1.3 122 0.212 0.6262 0 LCT-050-16 1.3 122 0.217 0.6262 0 LCT-050-17 1.3 122 0.216 0.6262 0 LCT-050-18 1.3 122 0.215 0.6262 0 Page 81

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit The LEU-COMP-THERM-079 fission product experiments include 10 critical configurations of low-enriched (4.3 1% U-235) UO 2 fuel rods arranged in a triangular pin pitch of 2.00 or 2.80 cm; the array is covered with water to provide both reflection and moderation. Criticality is achieved by adjusting the number of fuel rods to obtain near-critical conditions; the total number of fuel rods in each experiment varies from 158 to 257. The 36 centrally located fuel rods could be opened to allow placement of rhodium (Rh-103) foils between the fuel pellets. The number and thicknesses of the rhodium foils vary as the array size is also varied, such that the calculated reactivity worth of the rhodium ranges from 0% for cases with no rhodium, to a maximum of 3.5% Ak/k. Thus, the distribution of rhodium within the fuel rods is rather non-physical, but the cases were run to test the ability of the code and cross-section library to evaluate criticality with significant absorption by rhodium. Detailed descriptions of the various cases are provided in Reference [ 17]. Experimental parameters for each case are summarized in Table A- 13 where the tabulated EALF values are those calculated by KENO-V.a.

Table A-13: LEU-COMP-THERM-050 Experimental Parameters Case Pin Pitch

• H/X EALF Number of Foil Thickness Number (cm) Ratio (eV) Rhodium Foils (microns)

LCT-079-1 1.86 131 0.307 0 0 LCT-079-2 1.86 131 0.308. 0 0 LCT-079-3 1.86 131 0.311 31 25 LCT-079-4 1.86 131 0.314 31 50 LCT-079-5 1.86 131 0.319 31 105 LCT-079-6 2.61 332 0.109 0 0 LCT-079-7 2.61 332 0.109 0 0 LCT-079-8 2.61 332 0.110 31 25 LCT-079-9 2.61 332 0.111 31 50 LCT-079-10 2.61 332 0.112 31 105

" The triangular pin pitches of 2.0 and 2.8 cm are converted to equivalent square pin pitches having the same v'322 moderating ratio (H/X), by equating the unit areas of a hexagon and a square: - 2 a =b Page 82

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit A.12 Area of Applicability Key parameters and their ranges were evaluated in detail for both the HTC and fission product benchmark experiments. From the detailed evaluation, parameters judged to be of paramount significance for spent fuel pool criticality analysis are summarized in Table A-14, including key physical and spectral characteristics.

Table A-14: Area of Appliability Summary Characteristics Comment Fissile Material UO2 and UO/PuO2 (Spent) Fuel Rods Moderation Water with H/X ratio of 122 - 1150 Reflection Water or thick steel or lead plates submerged in water Soluble boron or dissolved gadolinium in water, and borated steel or aluminum Absorption (BORALO') plates or plates of cadmium with steel cladding submerged in water.

Some additional cases with elemental samarium and rhodium simulating fission products and low-enriched UO2 fuel.

Geometry Square-pitched Lattice Pin Pitch 1.30 - 2.61 cm Neutron Energy Spectrum EALF of 0.066 - 0.319 eV A.13 Results of Calculations with SCALE 4.4a The critical experiments described in Section A. 10 were modeled with the SCALE 4.4a code package with the CSAS25 driver executing the KENO-V.a module using the 44-group cross-section library 44GROUPNDF5.

Table A-15 provides a tabulation of all results, including the experimental values, the calculated values, and the normalized values (knorm), where the calculated values (kcajc) are normalized to the experimental values (kl.x) as shown below (Reference [7], equation 9). The normalized keff values (knorm) are used in all subsequent calculations for determination of the kcff bias and bias uncertainty.

knorrn = kcalc / kexp In addition, the total error (a,) is calculated as the statistical combination of the errors associated with the experimental method (aexp) and the calculational method (acac), as shown below (Reference [7], equation 3). The total error values (a,) are used in all subsequent calculations of the keff bias and bias uncertainty. It should be noted that the tabulated values of at are truncated to show only the significant digits. To avoid round-off error, however, the downstream calculations include additional significant figures that are inherent in the result of this and other intermediate calculations.

at = Oexp + al2 Page 83

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-1 5: Criticality Results for the Benchmark Experiments Number Case Experimental Values Calculated Values knorm 6, Name kexp _

__exp _calc kcalc I HTC-2327 1.0000 0.0006 1.0019 0.0002 1.0019 0.0006 2 HTC-2335 1.0000 0.0006 1.0015 0.0002 1.0015 0.0006 3 HTC-2336 1.0000 0.0006 1.0010 0.0002 1.0010 0.0006 4 HTC-2337 1.0000 0.0006 1.0012 0.0002 1.0012 0.0006 5 HTC-2339 1.0000 0.0006 1.0005 0.0002 1.0005 0.0006 6 HTC-2340 1.0000 0.0006 1.0006 0.0002 1.0006 0.0006 7 HTC-2341 1.0000 0.0006 0.9999 0.0002 0.9999 0.0006 8 HTC-2342 1.0000 0.0006 0.9994 0.0002 0.9994 0.0006 9 HTC-2343 1.0000 0.0006 1.0000 0.0002 1.0000 0.0006 10 HTC-2345 1.0000 0.0006 0.9991 0.0003 0.9991 0.0007 11 HTC-2347 1.0000 0.0006 0.9979 0.0003 0.9979 0.0007 12 HTC-2348 1.0000 0.0006 0.9983 0.0002 0.9983 0.0006 13 HTC-2349 1.0000 0.0006 0.9961 0.0002 0.9961 0.0006 14 HTC-2352 1.0000 0.0006 0.9956 0.0002 0.9956 0.0006 15 HTC-2353 1.0000 0.0006 0.9957 0.0002 0.9957- 0.0006 16 HTC-2355 1.0000 0.0006 0.9996 0.0002 0.9996 0.0006 17 HTC-2357 1.0000 0.0006 0.9992 0.0002 0.9992 0.0006 18 HTC-2361 1.0000 0.0006 1.0026 0.0002 1.0026 0.0006' 19 HTC-2405 1.0000 0.0017 0.9968 0.0002 0.9968 0.0017 20 HTC-2406 1.0000 0.0017 0.9969 0.0002 0.9969 0.0017 21 HTC-2407 1.0000 0.0017 0.9970 0.0002 0.9970 0.0017 22 HTC-2408 1.0000 0.0017 0.9967 0.0002 0.9967 0.0017 23 HTC-2409 1.0000 0.0017 0.9972 0.0002 0.9972 0.0017 24 HTC-2410 1.0000 0.0017 0.9964 0.0002 0.9964 0.0017 25 HTC-2411 1.0000 0.0017 0.9964 0.0002 0.9964 0.0017 26 HTC-2412 1.0000 0.0017 0.9965 0.0002 0.9965 0.0017 27 HTC-2415 1.0000 0.0017 0.9966 0.0002 0.9966 0.0017 28 HTC-2417 1.0000 0.0017 0.9997 0.0002 0.9997 0.0017 29 HTC-2419 1.0000 0.0017 0.9997 0.0002 0.9997 0.0017 30 HTC-2420 1.0000 0.0017 0.9997 0.0002 0.9997 0.0017 31 HTC-2422 1.0000 0.0017 0.9998 0.0002 0.9998 0.0017 32 HTC-2423 1.0000 0.0017 0.9996 0.0002 0.9996 0.0017 33 HTC-2425 1.0000 0.0017 1.0003 0.0002 1.0003 0.0017 34 HTC-2427 1.0000 0.0017 1.0001 0.0002 1.0001 0.0017 35 HTC-2430 1.0000 0.0017 1.0025 0.0002 1.0025 0.0017 36 HTC-2434 1.0000 0.0017 1.0032 0.0002 1.0032 0.0017 37 HTC-2436 1.0000 0.0017 0.9994 0.0002 0.9994 0.0017 38 HTC-2433 1.0000 0.0017 1.0020 0.0002 1,0020 0.0017 39 HTC-2437 1.0000 0.0008 0.9962 0.0002 0.9962 0.0008 40 HTC-2438 1.0000 0.0008 0.9958 0.0002 0.9958 0.0008 41 HTC-2441 1.0000 0.0008 0.9960 0.0002 0.9960 0.0008 42 HTC-2444 1.0000 0.0008 0.9973 0.0002 0.9973 0.0008 43 HTC-2446 1.0000 0.0008 0.9970 0.0002 0.9970 0.0008 44 HTC-2447 1.0000 0.0008 0.9969 0.0002 0.9969 0.0008 45 HTC-2448 1.0000 0.0008 0.9983 0.0002 0.9983 0.0008 Page 84

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-1 5: Criticality Results for the Benchmark Experiments (cont'd)

Number Case Experimental Values Calculated Values knorm Name kxp ffcxp kcalc OcaRc 46 HTC-2449 1.0000 0.0008 0.9975 0.0002 0.9975 0.0008 47 HTC-2459 1.0000 0.0008 1.0002 0.0002 1.0002 0.0008 48 HTC-2468 1.0000 0.0008 0.9985 0.0002 0.9985 0.0008 49 HTC-2470 1.0000 0.0008 1.0000 0.0002 1.0000 0.0008 50 HTC-2471 1.0000 0.0008 1.0001 0.0002 1.0001 0.0008 51 HTC-2473 1.0000 0.0008 0.9992 0.0002 0.9992 0.0008 52 HTC-2475 1.0000 0.0008 1.0014 0.0002 1.0014 0.0008 53 HTC-2478 1.0000 0.0008 1.0038 0.0002 1.0038 0.0008 54 HTC-2483 1.0000 0.0008 1.0024 0.0002 1.0024 0.0008 55 HTC-2485 1.0000 0.0008 1.0043 0.0002 1.0043 0.0008 56 HTC-2487 1.0000 0.0008 0.9956 0.0002 0.9956 0.0008 57 HTC-2482 1.0000 0.0008 1.0007 0.0002 1.0007 0.0008 58 HTC-2490 1.0000 0.0008 0.9943 0.0002 0.9943 0.0008 59 HTC-2492 1.0000 0.0008 0.9977 0.0002 0.9977 0.0008 60 HTC-2518 1.0000 0.0011 0.9973 0.0002 0.9973 0.0011 61 HTC-2521 1.0000 0.0011 0.9974 0.0002 . 0.9974 0.0011 62 HTC-2522 1.0000 0.0011 0.9975 0.0002 0.9975 0.0011 63 HTC-2523 1.0000 0.0011 0.9967 .0.0002 0.9967 0.0011 64 HTC-2511 1.0000 0.0011 0.9950 0.0002 0.9950 0.0011 65 HTC-2525 1.0000 0.0011 0.9955 0.0002 0.9955 0.0011 66 HTC-2526 1.0000 0.0011 0.9972 0.0003 0.9972 0.0011 67 HTC-2527 1.0000 0.0011 0.9942 0.0002 0.9942 0.0011 68 HTC-2509 1.0000 0.0008 0.9990 0.0002 0.9990 0.0009 69 HTC-2531 1.0000 0.0008 0.9989 0.0002 0.9989 0.0009 70 HTC-2532 1.0000 0.0008 0.9995 0.0002 0.9995 0.0009 71 HTC-2532 1.0000 0.0008 0.9990 0.0002 0.9990 0.0009 72 HTC-2533 1.0000 0.0008 0.9989 0.0002 0.9989 0.0009 73 HTC-2534 1.0000 0.0008 0.9978 0.0002 0.9978 0.0009 74 HTC-2536 1.0000 0.0008 0.9995 0.0002 0.9995 0.0009 75 HTC-2537 1.0000 .0.0008 1.0003 0.0002 1.0003 0.0009 76 HTC-2538 1.0000 0.0008 1.0001 0.0002 1.0001 0.0009 77 HTC-2539 1.0000 0.0008 0.9998 0.0002 0.9998 0.0009 78 HTC-2541 1.0000 0.0008 0.9999 0.0002 0.9999 0.0009 79 HTC-2544 1.0000 0.0008 0.9985 0.0002 0.9985 0.0009 80 HTC-2547 1.0000 0.0008 0.9998 0.0002 0.9998 0.0009 81 HTC-2548 1.0000 0.0008 1.0001 0.0002 1.0001 0.0009 82 HTC-2549 1.0000 0.0008 0.9991 0.0002 0.9991 0.0009 83 HTC-2563 1.0000 0.0010 1.0006 0.0002 1.0006 0.0010 84 HTC-2564 1.0000 0.0010 1.0006 0.0002 1.0006 0.0010 85 HTC-2565 1.0000 0.0010 1.0008 0.0002 1.0008 0.0010 86 HTC-2566 1.0000 0.0011 1.0003 0.0002 1.0003 0.0011 87 HTC-2567 1.0000 0.0011 1.0006 0.0002 1.0006 0.0011 88 HTC-2568 1.0000 0.0011 1.0007 0.0002 1.0007 0.0011 89 HTC-2569 1.0000 0.0008 0.9995 0.0002 0.9995 0.0008 90 HTC-2570 1.0000 0.0008 0.9990 0.0002 0.9990 0.0008 91 HTC-2571 1.0000 0.0008 0.9983 0.0002 0.9983 0.0008 Page 85

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-15: Criticality Results for the Benchmark Experiments (cont'd)

Number Case Experimental Values Calculated Values knorm Name kexp Icxp kcalc Ucalc 92 HTC-2572 1.0000 0.0008 0.9983 0.0002 0.9983 0.0008 93 HTC-2624 1.0000 0.0008 0.9977 0.0002 0.9977 0.0008 94 HTC-2625 1.0000 0.0008 0.9976 0.0002 0.9976 0.0008 95 HTC-2578 1.0000 0.0008 0.9982 0.0002 0.9982 0.0008 96 HTC-2579 1.0000 0.0008 0.9991 0.0002 0.9991 0.0008 97 HTC-2580 1.0000 0.0008 0.9999 0.0002 0.9999 0.0008 98 HTC-2581 1.0000 0.0008 0.9974 0.0002 0.9974 0.0008 99 HTC-2582 1.0000 0.0008 0.9967 0.0002 0.9967 0.0008 100 HTC-2583 1.0000 0.0007 0.9960 0.0002 0.9960 0.0008 101 HTC-2584 1.0000 0.0007 0.9957 0.0002 0.9957 0.0008 102 HTC-2621 1.0000 0.0006 0.9996 0.0002 0.9996 0.0006 103 HTC-2622 1.0000 0.0006 0.9999 0.0002 0.9999 0.0006 104 HTC-2550 1.0000 0.0019 1.0017

• 0.0002 1.0017 0.0020 105 HTC-2551 1.0000 0.0019 1.0027 0.0002 1.0027 0.0020 106 HTC-2552 1.0000 0.0019 1.0019 0.0002 1.0019 0.0020 107 HTC-2553 1.0000 0.0019 1.0024 0.0002 1.0024 0.0020 108 HTC-2554 1.0000 0.0005 1.0021 0.0002 1.0021 0.0005 109 HTC-2555 1.0000 0.0005 1.0019 0.0002 1.0019 0.0005 110 HTC-2556 1.0000 0.0005 1.0019 0.0002 1.0019 0.0005 I11 HTC-2557 1.0000 0.0005 1.0017 0.0002 1.0017 0.0005 112 HTC-2558 1.0000 0.0016 1.0023 0.0002 1.0023 0.0017 113 HTC-2559 1.0000 0.0016 1.0021 0.0002 1.0021 0.0017 114 HTC-2560 1.0000 0.0016 1.0019 0.0002 1.0019 0.0017 115 HTC-2561 1.0000 0.0016 1.0016 0.0002 1.0016 0.0017 116 HTC-2603 1.0000 0.0011 1.0003 0.0002 1.0003 0.0011 117 HTC-2604 1.0000 0.0011 0.9995 0.0002 0.9995 0.0011 118 HTC-2605 1.0000 0.0011 0.9995 0.0002 0.9995 0.0011 119 HTC-2606 1.0000 0.0007 0.9995 0.0002 0.9995 0.0008 120 HTC-2607 1.0000 0.0007 0.9981 0.0002 0.9981 0.0008 121 HTC-2608 1.0000 0.0007 0.9978 0.0002 0.9978 0.0008 122 HTC-2609 1.0000 0.0007 0.9971 0.0002 0.9971 0.0008 123 HTC-2610 1.0000 0.0007 0.9966 0.0002 0.9966 0.0008 124 HTC-2611 1.0000 0.0007 0.9997 0.0002 0.9997 0.0008 125 HTC-2612 1.0000 0.0010 0.9998 0.0002 0.9998 0.0010 126 HTC-2626 1.0000 0.0007 0.9969 0.0002 0.9969 0.0007 127 HTC-2614 1.0000 0.0014 0.9970 0.0002 0.9970 0.0014 128 HTC-2615 1.0000 0.0006 0.9974 0.0002 0.9974 0.0007 129 HTC-2616 1.0000 0.0006 0.9953 0.0002 0.9953 0.0007 130 HTC-2617 1.0000 0.0006 0.9948 0.0002 0.9948 0.0007 131 HTC-2618 1.0000 0.0006 0.9942 0.0002 0.9942 0.0007 132 HTC-2619 1.0000 0.0006 0.9938 0.0002 0.9938 0.0007 133 HTC-2620 1.0000 0.0008 0.9984 0.0002 0.9984 0.0008 134 HTC-2590 1.0000 0.0014 1.0019 0.0002 1.0019 0.0015 135 HTC-2591 1.0000 0.0014 1.0023 0.0002 1.0023 0.0015 136 HTC-2592 1.0000 0.0016 1.0013 0.0002 1.0013 0.0016 137 HTC-2593 1.0000 0.0016 1.0015 0.0002 1.0015 0.0016 Page 86

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-15: Criticality Results for the Benchmark Experiments (cont'd)

Number Case Experimental Values Calculated Values 1 knorm (t Name kCXp exp kcalc Ocalc 138 HTC-2594 1.0000 0.0016 1.0010 0.0002 1.0010 0.0016 139 HTC-2595 1.0000 0.0016 1.0009 0.0002 1.0009 0.0016 140 HTC-2596 1.0000 0.0016 1.0004 0.0002 1.0004 0.0016 141 HTC-2597 1.0000 0.0016 1.0011 0.0002 1.0011 0.0016 142 HTC-2598 1.0000 0.0003 1.0012 0.0002 1.0012 0.0004 143 HTC-2599 1.0000 0.0003 1.0004 0.0002 1.0004 0.0004 144 HTC-2600 1.0000 0.0003 1.0002 0.0002 1.0002 0.0004 145 HTC-2601 1.0000 0.0003 1.0005 0.0002 1.0005 0.0004 146 LCT-050-1 1.0004 0.0010 0.9964 0.0004 0.9960 0.0011 147 LCT-050-2 1.0004 0.0010 0.9957 0.0004 0.9953 0.0011 148 LCT-050-3 1.0004 0.0010 0.9959 0.0004 0.9955 0.0011 149 LCT-050-4 1.0004 0.0010 0.9964 0.0004 0.9960 0.0011 150 LCT-050-5 1.0004 0.0010 0.9975 0.0004 0.9971 0.0011 151 LCT-050-6 1.0004 0.0010 0.9978 0.0004 0.9974 0.0011 152 LCT-050-7 1.0004 0.0010 0.9979 0.0004 0.9975 0.0011 153 LCT-050-8 1.0004 0.0010 0.9947 0.0004 0.9943 0.0011 154 LCT-050-9 1.0004 0.0010 0.9944 0.0004 0.9940 0.0011 155 LCT-050-10 1.0004 0.0010 0.9942 0.0004 0.9938 0.0011 156 LCT-050-11 1.0004 0.0010 0.9956 0.0004 0.9952 0.0011 157 LCT-050-12 1.0004 0.0010 0.9970 0.0004 0.9966 0.0011 158 LCT-050-13 1.0004 0'0010 0.9969 0.0004 0.9965 0.0011 159 LCT-050-14 1.0004 0.0010 0.9962 0.0004 0.9958 0.0011 160 LCT-050-15 1.0004 0.0010 0.9963 0.0004 0.9959 0.0011 161 LCT-050-16 1.0004 0.0010 0.9972 0.0004 0.9968 0.0011 162 LCT-050-17 1.0004 0.0010 0.9981 0.0004 0.9977 0.0011 163 LCT-050-18 1.0004 0.0010 0.9979 0.0004 0.9975 0.0011 164 LCT-079-1 0.9999 0.0016 0.9953 0.0003 0.9954 0.0016 165 LCT-079-2 1.0002 0.0016 0.9957 0.0003 0.9955 0.0016 166 LCT-079-3 1.0005 0.0016 1.0000 0.0003 0.9995 0.0016 167 LCT-079-4 1.0004 0.0016 1.0014 0.0003 1.0010 0.0016 168 LCT-079-5 1.0004 0.0016 1.0020 0.0003 1.0016 0.0016 169 LCT-079-6 0.9994 0.0008 0.9971 0.0003 0.9977 0.0009 170 LCT-079-7 1.0003 0.0008 0.9979 0.0003 0.9976 0.0009 171 LCT-079-8 1.0008 0.0008 1.0015 0.0002 1.0007 0.0008 172 LCT-079-9 1.0003 0.0008 1.0021 0.0003 1.0018 0.0009 173 LCT-079-10 1.0009 0.0008 1.0029 0.0002 1.0020 0.0008 Page 87

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Bumup Credit The most obvious correlation observed in both the HTC and fission product benchmark results is that determined by pin pitch, which also establishes the moderating ratio (H/X), and drives the spectral response. Therefore, the entire dataset from Table A-15, consisting of all four phases of the HTC results and the fission product benchmark results, are plotted as a function of the following parameters:

• Pin Pitch

• Moderating Ratio, H/X

• Energy of the Average Lethargy causing Fission, EALF In order to visualize the Table A- 15 dataset relative to the results obtained for the original dataset summarized in Table A-3, the original non-HTC data will also be overlaid onto the same plots. These overview plots are illustrated in Figure A-13 to Figure A-15, respectively, for pin pitch, H/X, and EALF.

Figure A-13: Overview of Normalized keff versus Pin Pitch 1.020 1.015 0 1.010 0

1.005 0 0 0 0 Z

0 j

~O S1.000 t-0 01

0. 995 E 0 S 0 +A0 0 0 z A0 0 00 0.990 0 o0 0.985 0 0

00 0.980 t 0.975 0 1 2 3 4 5 6 7 Pin Pitch (cm)

• HTC Phase 1

• HTC Phase 2 Gad

• HTC Phase 2 Boron 0 HTC Phase 3 a HTC Phase 4 Lead

• HTC Phase 4 Steel x LCT-050 + LCT-079 0 Original, Non-HTC Page 88

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Bumup Credit Figure A-14: Overview of Normalized k.f versus H/X 1.020 1.015 1.010 1.005 I 1.000 0.995 0

z 0.990 0.985 0.980 0.975 0 200 400 600 800 1000 1200 1400 Moderating Ratio, H/X M HTC Phase i

• HTC Phase 2 Gad A HTC Phase 2 Boron 0 HTC Phase 3 S HTC Phase 4 Lead

• HTC Phase 4 Steel x LCT-050 + LCT-079 0 Original, Non-HTC Page 89

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Bumup Credit Figure A-15: Overview of Normalized kef versus EALF 1.020 1.015 0 1.010 0

0 -- 0 1.005 00 0 +

0 0 0

• 1.000 0 80 o0

& 0.995 0 0

Z0 0 0.990 0 +0 0.985 0.980 0 0.975 0 0.5 1 1.5 2 2.5 3 EALF (eV)

• HTC Phase 1

• HTC Phase 2 Gad A HTC Phase 2 Boron 0 HTC Phase 3 0 HTC Phase 4 Lead

• HTC Phase 4 Steel x LCT-050 + LCT-079 0 Original, Non-HTC The overview plots of Figure A- 13 to Figure A- 15 illustrate that normalized kcff data obtained from the HTC and fission product criticality experiments is more tightly grouped with less scatter about a mean value close to one, while the original non-HTC data has much larger scatter and a lower mean value. This observation suggests that a lower bias and bias uncertainty would result from the pooling of all data: HTC, fission product, and the original non-HTC data. It is also apparent that the HTC and fission product experiments are generally more highly moderated, resulting in lower EALF values. Rather than pooling all of the data, it was considered prudent to analyze the HTC and fission product data by itself to determine the bias and bias uncertainty, which should show that the original bias summarized in Section A.9 is conservative. Therefore, only the HTC and fission product data is considered in subsequent sections.

Page 90

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit A.14 Trending Analysis and Lower Tolerance Band A linear regression analysis was performed to evaluate any bias based on trend, with the independent variable defined by the following physical or spectral parameters of interest:

• Pin Pitch

" Moderating Ratio, H/X

" Energy of the Average Lethargy causing Fission, EALF The values of these parameters are tabulated in Table A-7 through Table A- 10, Table A- 12 and Table A- 13.

Table A- 15 lists the normalized kcff values (knor) and corresponding total uncertainty values (ot). Reference [7]

suggests the use of weighting factors to reduce the importance of data with higher uncertainty. In this particular application, where the experimental errors are relatively small compared with the variance in the normalized krff results, the use weighting factors is not indicated. For completeness, however, both weighted and non-weighted trends were evaluated and compared.

Results are summaried in Table A- 16 and Table A- 17, for weighted and non-weighted trends, respectively.

Calculated TvaWuos are compared with the critical value of the Student's T-distribution with a significance level of cX

= 0.05/2 = 0.025 and n - 2 = 171 degrees of freedom, for which the Excel TINV function returns a value of 2.261.

The null hypothesis for this test (HO), is that the slope is not statistically significant; thus, a statistically significant trend may exist if: JTvalueI > 2.261. In cases where a statistically significant trend is indicated by the Student's T-test, then the residuals of the regression are tested to determine if the error component is normally distributed with mean zero, which confirms that the statistical test for significance is valid. The Anderson-Darling test described in Reference [18] is employed for this purpose. The null hypothesis of normality is rejected if the value of A*

exceeds the critical value of 0.752, at a significance level of 0.05. Therefore, if A* < 0.752, then the residuals are distributed normally and the statistical test for significance is valid.

Table A-16: Results Summary for Weighted Trending Analysis Parameter Pin Pitch Moderating Ratio (H/X) EALF Slope 0.00353 0.00001 -0.02071 Intercept 0.99325 0.99640 1.00198 r 0.1529 0.1957 0.2181 IT-valuel 5.556 6.450 6.907 Valid Trend? Yes Yes Yes A* 0.502 0.318 0.451 Statistical Test Valid? Yes Yes Yes Page 91

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-17: Results Summary for Non-Weighted Trending Analysis Parameter Pin Pitch Moderating Ratio (H/X) EALF Slope 0.00376 0.00001 -0.01624 Intercept 0.99282 0.99613 1.00141 r2 0.1651 0.2310 0.1713 T-value 5.814 7.166 -5.946 Valid Trend? Yes Yes Yes A* 0.506 0.296 0.330 Statistical Test Valid? Yes Yes Yes Based on the trending results summarized in Table A-16 and Table A-17, valid trends are indicated for pin pitch, moderating ratio (H/X), and EALF; thus, suggesting that a single-sided lower tolerance band can be used to establish the bias and uncertainty as a function of either parameter, whichever is the most limiting. In general, it can be seen that the slopes are very small and the correlations are relatively weak, suggesting that the linear trend is not sufficient to account for the variance in the dependent variable (krff). If the statistical test (Tvaluc) indicates a valid trend, however, and if the statistical test is determined to have validity, then the linear trend can be used to define a bounding limit. Quantitative differences between weighted and non-weighted results are relatively small, which was to be expected, since the weighting factors do not vary too significantly over the range of the data.

Figure A- 16 to Figure A- 18 illustrate the trends of normalized kff versus pin pitch, moderating ratio, and EALF, respectively. Also shown on each plot are the calculated trend, the KL determined by the single-sided lower tolerance band technique, and the lower tolerance limit (KL = 0.99458 - 0.00985 = 0.98473) obtained from the bias and uncertainty determined in Sections A.2 through A.9. Calculational details of the lower tolerance band were obtained from Reference [7].

Page 92

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure A-16: Trend of knorm versus Pin Pitch with Lower Tolerance Band 1.020 1.015 1.010 1.005

. 1.000 Zo 0.995 0.990 0.985 0.980 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 Pin Pitch (cm) 0 HTC Data A LCT-050 Data U LCT-079 Data - Weighted Trend

- Weighted KL - - - Non-weighted Trend - - Non-weighted KL - - Non-HTC K_L Page 93

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure A-17: Trend of knorm versus HIX with Lower Tolerance Band 1.020 1.015 1.010

> 1.005 U

Ip

-* 1.000 M

o 0.995 0.990 0.985 0.980 100 200 300 400 500 600 700 800 900 1000 1100 1200 Moderating Ratio, H/X HTC Data LCT-079 Data U LCT-050 Data - Weighted Trend Weighted K L -- - Non-weighted Trend - - Non-weighted KL - - Non-HTC K_L Page 94

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure A-18: Trend of kno~r versus EALF with Lower Tolerance Band 1.020 1.015 1.010

> 1.005

-* 1.000 zo 0.995 0.990 0.985 0.980 0.05 0.10 0.15 0.20 0.25 0.30 0.35 EALF (eV) 0 HTC Data A LCT-050 Data M LCT-079 Data Weighted Trend

-Weighted KL -- - Non-weighted Trend - - Non-weighted K L - - Non-HTC KL The trends illustrated in Figure A- 16 to Figure A- 18 show single-sided lower tolerance bands that would support a limit of KL = 0.9900, within the AOA defined by Table A-14. When compared with the KL = 0.98473 limit (from Sections A.2 through A.9), it can be seen that the proposed limit (KL = 0.98473) is indeed conservative.

However, due to the limited range of the trends, additional evaluations were performed to ensure that the lower tolerance limit is conservatively established.

Page 95

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit A.15 Normality Evaluation and Lower Tolerance Limit Normality of the kn.o.. data was determined by employing the x2 test. This test separates the data into bins based on magnitude. Letj represent the number of bins, which spans the range of the data being analyzed. Let, Oi represent the observed value, or the actual number of kno0 mvalues in the ith bin. Also, let Ei represent the expected number of knorm values in the ith bin, assuming a normal distribution. Then, the value of the X2 statistic is calculated as shown:

x2 (i -E)

The null hypothesis for this test is that the data is from a normal distribution. If the X 2 statistic is found to be less that the critical value at a significance level of a = 0.05, then there is no reason to believe that the distribution is not from a normal distribution. When the data is sorted into ten bins ( = 10), then only 10 2 = 7 degrees of freedom remain; one degree of freedom is lost by the choice of j, two additional degrees of freedom are lost because the mean value and the standard deviation of the data need to be determined in order to calculate the expected number of data in each bin (Ei). The critical value of the X2 statistic with a = 0.05 and 7 degrees of freedom was found using the Excel function CHIINV: XCritical = 14.07.

For the normalized krff data in Table A- 15, the weighted mean and variance about the mean were evaluated as shown below.

Ski keff = = 0.99898

-12 s

2 =

0nr 1=5.2038E-06

}

n 0cy Corresponding values of the non-weighted mean and variance are keff = 0.99880 and s 2 = 5.5446E - 06, which can be obtained by setting ai = 1.0 for all i's in the above formulas. In Section A. 14, the weighting factors were determined to have relatively little effect on the trending results. Here, the non-weighted values will clearly produce a lower limit, therefore the non-weighted mean and standard deviation (a = s2 = 0.00235 ).were used with the Excel function NORMDIST to determine the cumulative probability as a function of upper kcff bound for each bin. Taking the difference in cumulative probability for adjacent bins times the total number of data (n),

yields the expected number of data in each bin, El. A summary of the bins, frequencies (observed and expected),

and results of the X2 test are found in Table A-18. The X 2 statistic for this test (24.10) was found to exceed the critical value of 14.07; consequently, the data does not follow a normal distribution. This conclusion was further Page 96

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit confirmed using the Anderson-Darling normality test (Reference [17]) resulting in A* = 1.244, which exceeds the critical value of 0.752 for a significance level of a = 0.05.

Table A-18: Results Summary for Chi-squared Normality Test Observed Cumulative Expected E)2 Bin i Low Bound High Bound Frequency Normal Frequency -

Oi Oj ~~Probability Distribution Ei E 1 -inf 0.9942 5 0.02549 4.410 0.079 2 0.9942 0.9954 8 0.07465 8.504 0.030 3 0.9954 0.9966 20 0.17557 17.459 0.370 4 0.9966 0.9978 34 0.33623 27.795 1.385 5 0.9978 0.9990 14 0.53460 34.318 12.030 6 0.9990 1.0002 40 0.72457 32.864 1.550 7 1.0002 1.0014 25 0.86565 24.408 0.014 8 1.0014 1.0026 23 0.94692 14.059 5.686 9 1.0026 1.0038 3 0.98322 6.280 1.713 10 1.0038 +inf 1 1.00000 2.903 1.247

..--- Sum 173 --- X2 24.10 Figure A- 19 illustrates the observed and expected frequency distributions obtained from the X2 test. This figure shows that the distribution of normalized kcff values is skewed in the direction of a higher average value.

Therefore, the non-weighted-average kcff value is expected to produce a higher lower tolerance limit than the lower tolerance bands that were produced by the data trends. To compare, the KL calculation is performed using the values: keff = 0.99880, s = 5.5446E - 06, and the average total uncertainty: 2 = 7.0093E - 07 (Reference

[7], equation 5). In addition, the 95/95 single-sided tolerance factor for n = 100 (conservative) is C 95/95 = 1.927, from Reference [22]. The square root of the pooled variance (Sp) and the single-sided lower tolerance limit (KL) are calculated as shown below.

S= 2 + = I(5.5446E V2 - 06) + (7.0093E - 07) = 0.00250 KL = keff - C 95/95 SP = 0.99880 - (1.927X0.00250) = 0.99398 Page 97

A AREVA Document No.: ANP-2858NP-003 Palisades SEP Region 1 Criticality Evaluation with Bumup Credit Figure A-19: Frequency Distribution Comparison from Chi-squared Test 45 40 35 30 0

, 25 E

zz it 20 5

10

~5 10 0.9936 0.9948 0.9960 0.9972 0.9984 0.9996 Frequency]

1.0008 1.0020 1.0032 1.0044

• ExPected k-effective Frequency

• Observed U ObservedFrequency U Expected Frequenc Comparison of the calculated lower tolerance limit, KL = 0.99398, with the kom, data and the lower tolerance bands plotted in Figure A- 16 to Figure A- 18 shows the lower tolerance bands to be more limiting near the extreme ends of the ranges. Therefore, the lower tolerance limit based on a data sample with an assumed normal distribution is indeed non-conservative due to the trend of the data near the extreme ends of the ranges.

Page 98

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit A.16 Nonparametric Statistical Evaluation In Section A. 15, it was determined that the knorm data sample is not normally distributed, which indicates that a nonparametric approach may be most appropriate. First, the data sample is ranked in ascending order as shown:

k1 < <kn Equation 31 of Reference [7] provides a means for calculation of the confidence level P1,nq, for a population fraction q, and a tolerance limit of rank m (kin), in an ordered data sample of size n. While a population fraction of 95% is required, Reference [7] showed that only 59 cases are required to achieve a confidence level of 95%

when the tolerance limit is based on the lowest observed value (kl). Due to the larger sample size of n = 173, a 95/95 tolerance limit (q = 0.95) can be determined by using the formula below to calculate the mth value which satisfies Pm > 0.95. The results show that a 95/95 tolerance limit can be achieved using the fourth lowest value, but that the confidence level drops to 93.7% using the fifth ranked value. Since the fourth smallest observed value is 0.9942, then it can be stated with 95% confidence that 95% of the true population lies above this value.

Furthermore, having exceeded the 90% confidence level, there is no need to reserve additional nonparametric margin (as defined in Table 2-2 of Reference [7]).

m-1 n1

[rm,n,q =1- j!(n (1- q)jq nm=1- 1 - (0.95)173 = 0.9999 n-173 q= .95 1 72 0.9986 m=2 = 0.9999 - (173X1 - 0.95X0.95) =

n=173 q-0.95 m=3 =0.9986 - (I 72X1 73) (1- 0.95)2 (0.95)171 = 0.9928 n=173 2 q=0.95 Mn=4 = 0.9928 - (171X172X173)( 1 - 0.95)3 (0.95)170 = 0.9755

,=1=73 (2X3) q-0.95 M=5 = 0.9755 - (170)(171X172X173) (1- 0.95)4 (0.95)169 = 0.9368 n-173 (2X3X4) q=0.95 The total uncertainty associated with the fourth smallest value in the population sample is 0.00112, as calculated below.

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Bumup Credit S (011)2 +(o0.0oo2) 2 =0.00112 Finally, the lower tolerance limit, KL, can be calculated as shown below.

KL = 0.9942 - 0.00112 - (O.OO)NPM = 0.99308 From Figure A- 16 and Figure A- 17 and the lower tolerance band calculations for trends based on pin pitch and H/X, respectively, it can be determined that a lower tolerance limit of KL = 0.9925 is bounding for the lower extremes of the ranges identified in Table A-14: a pin pitch of 1.30 cm and moderating ratio of H/X = 122. For the EALF trend illustrated in Figure A-18, however, the upper extreme of the range (0.319 eV) is limiting and a KL = 0.9900 is bounding. The uncertainty term can be intentionally increased, from 0.00112 to 0.0042 in order to obtain an error-adjusted lower tolerance limit of KL = 0.9900, which is bounding for the AOA~defined in Table A-14, based on the calculated trends for pin pitch, H/X, and EALF.

A.17 Effect of Removing HTC Phase 2 and Phase 4 Cases In Section A. 10, it was noted that the HTC Phase 2 and Phase 4 cases may be somewhat less applicable for spent fuel pool criticality analysis, due to dissolved gadolinium in the moderator for Phase 2, and the use of thick lead or steel reflectors in Phase 4. The relevant question is whether removal of these 83 cases would result in a more conservative bias and bias uncertainty (i.e. a reduction of the lower tolerance limit). Of the 90 cases that would remain, the lowest value is 0.9938. Based on a nonparametric statistical treatment for a data sample of 90 cases, 95% of the true population lies above the lowest value of 0.9938, with a confidence level of 99%, as shown by the calculation below (Reference [7], equation 32). Note that the confidence level for the second lowest value in a sample size of 90 is less than the desired 95%.

=rn- = 1 - (0.95)90 = 0.9901 n=90 q=0.95 M=2 = 0.9901 - (90X1 - 0.95X0.95) 89 = 0.9433 n=90 q=0.95 In order to visualize the data and obtain a qualitative evaluation of potential trends, the normalized kff values for the data sample of n = 90 were plotted as a function of pin pitch, moderating ratio (H/X), and EALF, as shown in Figure A-20 to Figure A-22, respectively. These figures also show the non-error-adjusted lower tolerance limit line at KL = 0.9938, which passes through the lowest value. All three plots suggest relatively flat trends with very small slopes, similar to the trends observed in the larger sized sample, as shown in Figure A- 16 to Figure A-18. Therefore, the trends can be considered insignificant for the determination of an appropriate lower bound.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure A-20: Normalized keff versus Pin Pitch for n=90 1.020 1.015 1.010 1.005 U

Vo 1.000

+.

Z0 0.995 _~

0.990 0.985 l 0.980 I-1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 Pin Pitch (cm)

I HTC Phase 1

• HTC Phase 2 A HTC Phase 3 x LCT-050 Data + LCT-079 Data - - Lower Tolerance Limit (KL)

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure A-21: Normalized keff versus Moderating Ratio for n=90 1.020 1.015 1.010

. 1.005

.1.000 95--°°°

+

I ~+

i 6

o0.995 0.990 0.985 0.980 100 300 500 700 900 1100 Moderating Ratio, H/X N HTC Phase 1

• HTC Phase 2 A HTC Phase 3 x LCT-050 Data + LCT-079 Data - Lower Tolerance Limit (KL)

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure A-22: Normalied keff versus EALF for n=90 1.020 1.015 1.010

.> 1.005

• 1.000 A ao xe:ý' N X +

E - -- - - - - - - -+

o 0.995 0.990 0.985 0.980 -

0.05 0.10 0.15 0.20 0.25 0.30 0.35 EALF (eV) a HTC Phase 1

• HTC Phase 2 A HTC Phase 3 X LCT-050 Data + LCT-079 Data - - Lower Tolerance Limit (KL)

Since no significant trends were identified, the distribution of the data sample was tested for normality. A Y2 test was performed with 7 degrees of freedom, as summarized in Table A-19. TheX 2 statistic for this test (12.44) does not exceed the critical value of 14.07 (see Section A.14); consequently, the data is normally distributed. The non-weighted-mean (keff ), variance about the mean (S2), and average total uncertainty are calculated as shown below (U2).

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table A-19: Results Summary for Chi-squared Normality Test for n=90 Obered Observed Normal Cumulative Expected (Oi- Ei)

Bin i Low Bound High Bound Frequency Probability Frequency - i 0i Distribution Ei 1 -inf 0.9951 6 0.08909 8.019 0.508 2 0.9951 0.9962 17 0.18890 8.982 7.157 3 0.9962 0.9973 10 0.33812 13.430 0.876 4 0.9973 0.9984 14 0.51866 16.248 0.311 5 0.9984 0.9995 11 0.69539 15.905 1.513 6 0.9995 1.0006 17 0.83536 12.597 1.539 7 1.0006 1.0017 8 0.92506 8.073 0.001 8 1.0017 1.0028 5 0.97157 4.186 0.158 9 1.0028 1.0039 1 0.99107 1.756 0.325 10 1.0039 +inf 1 1.00000 0.803 0.048

--- Sum 90 --- X2 12.44 ke- =nki =0.99829 n.i S2 (Z(ki

-kff= 5.6109E- 06 n-2

&2_ = 7.0198E- 07 Z2 The 95/95 single-sided tolerance factor (C95/95) for a sample size of 50 (conservative) is 2.065, from Table 2.1 of Reference [7]. Finally, the square root of the pooled variance (Sp) and the lower tolerance limit (KL) are calculated as shown below.

Sp = js2 c_+2 = V(5.6109E - 06)+ (7.0198E - 07) = 0.00251 KL = keff -C 9 5/9 5 SP 0.99829 - (2.065X0.00251) = 0.99310 Since the lower tolerance limit is larger for the smaller size sample, it can be concluded that retention of the HTC Phase 2 and Phase 4 cases is instrumental in establishing a more conservative limit (0.9900 vs. 0.993 1), even though the applicability of these cases may be somewhat questionable for spent fuel pool criticality analysis.

Furthermore, if the fission product benchmark cases were also deleted, in addition to the HTC Phase 2 and 4 cases, then a similar analysis showed that a lower tolerance limit of KL = 0.9939 would result with n = 62 cases.

Consequently, retention of the fission product benchmarks (LEU-COMP-THERM-050 and LEU-COMP-THERM-079) also produces a more conservative limit (0.9900 vs. 0.9939).

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit A.18 Establishing the Bias and Bias Uncertainty The nonparametric statistical analysis described in Section A. 16 determined an error-adjusted lower tolerance limit of KL = 0.9900, as shown in the calculation below, which follows from equation 33 of Reference [7].

KL = Fourth smallest keff value - Uncertainty for the 4 th smallest keff - Nonparametric Margin (NPM)

KL = 0.9942 - 0.0042 - (O.OO)NPM = 0.9900 In this formulation, the 0.9942 term is actually a 95/95 lower tolerance limit, not an average value, and the error term, 0.0042, is not a tolerance limit. In order to determine the appropriate bias, recall that the limiting trend was versus EALF (Figure A- 18) where the value of the weighted fit at the higher extreme of the range (0.319 eV, from Table A-15) is 0.9954, and the corresponding value of the lower tolerance limit is KL(EALF = 0.319 eV) =

0.9900. Since this extreme is bounding, it is appropriate to consider that the mean value is 0.9954, and the calculational bias is -0.0046, as shown below (from equation 8 of Reference [7]).

Bias = keff - 1= 0.9954 0.0046 The difference between the mean value and the lower tolerance limit at EALF = 0.319 eV can be taken as the bias uncertainty, a product of the square root of the pooled variance and the 95/95 tolerance factor (C 9 5 /9 5 ). From the lower tolerance band analysis (Section A. 14), the square root of the pooled variance for the weighted-fit versus EALF is: (Sp)fit = 0.00219 (Reference [7], equation 30). The 95/95 tolerance factor can also be determined, as follows:

C 9 5 / 9 5 (Sp)fit = C 9 5 / 9 5 (0.00219) = 0.9954 - 0.9900 = 0.0054 C 9 5 / 95 = 2.466 This 95/95 tolerance limit corresponds to about 17 degrees of freedom, according to Table 2.1 of Reference [7].

The calculational bias and bias uncertainty summarized below, can be used in parametric formulations for criticality evaluation, with a corresponding 17 approximate degrees of freedom, or C 95 /9 5 = 2.466.

" Bias = 0.9954 - 1 = -0.0046

" Bias Uncertainty = C 95 /9 5 Sp = (2.466)(0.00219) = 0.0054 Page 105

A ARE VA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit A.19 Results and Conclusions The French HTC criticality experiments and selected fission product experiments from the International Handbook of Evaluated Criticality Safety Benchmark Experiments were modeled with the SCALE 4.4a code package to obtain criticality benchmarks, which were normalized to the experimental results. The resulting normalized kcff data sample was analyzed for trends and tested to determine if the data was distributed normally.

Valid linear trends of statistical significance were identified for the fitting parameters pin pitch, moderating ratio (H/X), and energy of the average lethargy causing fission (EALF). Testing determined that the normalized kcff data sample did not follow a normal distribution. Therefore, a nonparametric statistical analysis was performed, which concluded that 95% of the true population lies above a value of keff = 0.9942, with a confidence level of 95%. The uncertainty associated with this value is 0.00112, including the errors resulting from both the experimental method, and the calculational method. The limiting kff value was compared to the data trends at the extremes of the ranges defined by the Area of Applicability summarized in Table A-14; the uncertainty was intentionally increased from 0.00112 to 0.0042, in order to obtain an error-adjusted lower tolerance limit of KL =

0.9900, which is bounding. Because the confidence level exceeds 90%, the nonparametric margin requirement is zero (NPM = 0.00). The error-adjusted lower tolerance limit of 0.9900 is calculated as shown below.

KL = 0.9942 - 0.0042 - (O.OO)NPM = 0.9900 Based on the limiting trend versus EALF, the calculational bias and bias uncertainty summarized below, can be used in parametric formulations for criticality evaluation, with a corresponding 17 approximate degrees of freedom, or C 9 5 /95 ý 2.466.

" Bias = 0.9954 - 1 = -0.0046

• Bias Uncertainty = C 9 5 /9 5 Sp = (2.466)(0.00219) = 0.0054 Finally, the bias, bias uncertainty, and lower tolerance limit originally proposed for licensing of the Palisades spent fuel pool were -0.00542, 0.00985, and 0.98473 (see Section A.9). Therefore, since the original bias, uncertainty, and tolerance limit are conservative with respect to those determined for the HTC and fission product criticality benchmarks, the original bias and bias uncertainty summarized in Section A.9 remain valid.

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit APPENDIX B: CASMO CALCULATIONS FOR BURNUP This section describes the methods and results for the burnup credit analysis. A summary of key aspects of the bumup credit analysis is given in the following table:

Table B-I: Depletion Modeling Considerations Page 107

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit B.1 BUC Calculational Method The Palisades Region 1 storage rack uses fixed spacing (2-of-4, 3-of-4, or 4-of-4), burnup credit (BUC), and soluble boron (PPM) credit to provide safe storage of discharged fuel assemblies. The application of BUC requires more calculations than the typical fresh fuel rack analysis. For BUC applications the reactivity effect of the following items must be evaluated and factored into the analysis:

• Operating history of the fuel including fuel and moderator temperatures 0 Axial burnup distributions as a function of assembly-average bumup

• 5% uncertainty of reactivity decrement due to burnup 0 Measured burnup uncertainty These parameters contribute to the residual reactivity of the burned fuel with the axial distribution having a significant impact at higher assembly-average bumups.

The details of the BUC methodology are contained in the following sections.

B.1.1 Assembly Operation and Depletion Data I

In order to perform the burnup credit (BUC) SFP storage rack calculations, the design basis fuel assembly must be characterized with in-core depletion calculations. The depletion calculations are intended to maximize the assembly reactivity at a given burnup by conservatively modeling moderator and fuel temperatures during reactor operation. This section documents the reactor operational data needed to perform the CASMO-3 depletion calculations.

The moderator temperatures and fuel temperatures are sensitive to operating temperatures, which are a function of core power level and RCS core flow. A bounding axial temperature profile was calculated based on the maximum allowed inlet temperature of 544 'F and a temperature rise across the assembly of 91 'F. These values are shown in Table B-2. Note that the resulting moderator temperature distribution provides a core exit temperature that is achievable due to the limitations of core inlet temperature (COLR limit). 635 'F is 1.51 0F below the saturation temperature of the lower pressurizer pressure limit of the COLR.

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table B-2: Axial Moderator Temperature Distribution Node Center (cm) Temperature (°C) Temperature (K) 9.36 287.25 560.41 28.06 290.06 563.22 46.78 292.87 566.03 84.20 301.30 574.46 140.42 309.73 582.89 196.46 318.15 591.31 252.61 326.57 599.73 290.03 329.38 602.54 308.75 332.19 605.35 327.45 335.00 608.16 A conservative fuel temperature of 1260 OF (955.4 K) is used for all nodes. This includes a 100 'F allowance to the maximum estimated fuel temperature of 1160 'F (PRISM core averaged at each axialnode). A conservative (higher) moderator and fuel temperature produces more fissile material (i.e., Pu-239).

B.1.2 Assembly Axial Burnup Data for Rack BUC Analysis Typical burnup credit analyses submitted to the US NRC have used a uniform, average burnup distribution over the entire length' of the assembly. Such a uniform distribution underestimates the burnup at the center of the assembly and over estimates the burnup at the top and bottom of the assembly. Thus, to adequately utilize burnup credit the impact of the axial burnup distribution at any given assembly-average bumup must be understood. This requires that an estimate of the reactivity effects-of the axial burnup distribution relative to a uniform distribution be determined and appropriately applied to the results (i.e., an axial burnup distribution penalty factor).

Alternatively, an explicit axial burnup distribution can be modeled in KENO-V.a calculations directly,'which removes the need for application of an axial burnup distribution penalty. The BUC evaluation for the Palisades SFP racks will use the latter approach (i.e., use an explicit axial bumup distribution).

The relative axial distribution provided in Table B-3 is derived from NUREG/CR-6801 (Reference [9]), and has been shown to be applicable to Palisades, based on PRISM (Reference [24]) code output and data reports for Palisades Cycles 18 - 21 (see Figure B-1), which are representative of past and future operations. Note that these axial burmup values are independent of the initial enrichment of the fuel, and generally the bumup in the top of the core is higher for the EOC bumup profiles (lines) than the bounding profile (circles) from NUREG/CR-6801, except for the very top node, which is an axial blanket with reduced enrichment.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table B-3: 25, 30, and 48 GWD/MTU Burnup Profiles - 336.81 cm Height Center Node Node KENO Node KENO Node KENO Axial Top Burnup Node Burnup Node Burnup Node Height He 25 30 Bur 48 Height Height GW GWD/MTU GWD/MTU Burnup cm cm GWD/MTU GWD/MTU GWD/MTU GWD/MTU GWD/MTU GWD/MTU 9.36 18.71 15.75 15.75 18.57 18.57 27.50 27.50 28.06 37.42 23.40 23.40 27.72 27.72 44.02 44.02 46.78 56.13 26.65 26.65 31.68 31.68 51.17 51.17 65.48 74.84 27.58 32.91 53.09 84.20 93.57 27.70 27.67 33.06 33.01 53.47 53.30 102.93 112.28 27.73 33.03 53.33 121.62 131.02 27.80 33.09 53.09 140.42 149.73 27.98 27.98 33.36 33.40 52.85 52.86 159.04 168.44 28.15 33.75 52.66 177.84 187.15 28.30 34.08 52.46 196.46 205.82 28.38 28.35 34.29 34.22 52.27 52.29 215.19 224.53 28.38 34.29 52.13 233.88 243.24 28.23 34.08 51.89 252.61 261.97 27.73 27.33 33.45 32.98 51.50 51.28 271.33 280.68 26.03 31.41 50.45 290.03 299.39 21.78 21.78 26.46 26.46 47.66 47.66 308.75- 318.10 17.23 17.23 21.03 21.03 39.94 39.94 327.45 336.81 11.20 11.20 13.68 13.68 24.58 24.58 Page 110

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure B-1: Burnup profiles for Cycles 18 - 21 for burnups 30-34 GWD/MTU (EOC burnup profiles (lines) and the bounding profile (circles). The locations of the upper and lower blankets are indicated by gray lines.)

0 0

I-0._

.0 0 I.-

0 0 50 100 150 200 250 300 height (cm)

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit B.1.3 Isotopic data direct transfer to KENO B.1.4 I Page 112

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit B.1.5 Loading Curve Generation Method The general objective of the loading curve is to determine the physical requirements for which assemblies of a given initial enrichment loading and assembly-average burnup can be stored in a given storage rack configuration.

The general process for generating a BUC loading curve is to calculate the KENO-V.a BUC data, based on initial assembly enrichments and various burnups. A set of enrichment and bumup points was established in Section 4.0 for the various loading patterns at selected enrichments (see Table 4-3, Table 4-6, Table 4-9, and Table 4-12),

using the process outlined in the previous section. The intermediate enrichments in Table 4-3, Table 4-6, Table 4-9, and Table 4-12 were then developed by linear interpolation between these derived limits. For example, for C-Rack region I B (the 3-of-4 loading pattern), the enrichment/burnup values were determined by interpolating between the 4.54% fuel at 30 GWD/MTU and 2.10% fuel at 0 GWD/MTU. For region IC (the 4-of-4, or fully loaded section), the values were determined by interpolating between 1.35% at 0 GWD/MTU, 2.75% at 25 GWD/MTU, 4.54% at 48 GWD/MTU. For E-rack, the partially loaded (3-of-4 loading pattern) values were determined by interpolating between 2.35% at 0 GWD/MTU and 4.54% at 19 GWD/MTU. For the E-rack, the fully-loaded (4-of-4 loading pattern) values were determined by interpolating between 1.48% at 0 GWD/MTU, 3.30% at 25 GWD/MTU, and 4.54% at 38 GWD/MTU.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Also, for implementing as Technical Specifications, a 10% measurement uncertainty is added to all burnup values in the tables. This conservatively bounds the differences that may occur between the average two-dimensional assembly burnup values, as determined by the incore monitoring system, and the actual burnup.

The loading limits are as shown in Table 4-3, Table 4-6, Table 4-9, and Table 4-12.

B.1.6 Burnup Credit Penalty In accordance with NRC directives (Reference [6]), an additional penalty is taken when burnup credit is applied to account for uncertainty in the depletion. This penalty is 5% of the difference between the reactivity of the assembly when fresh and the reactivity of the assembly at the desired burnup point. This is based on comparing the keff for fresh fuel in a fuel rack to that of burned fuel. KENO-V.a was used to generate cases at fresh conditions, and compared to the KENO-V.a models with burned fuel compositions.

For C-rack with full loading (4-of-4) pattern, KENO-V~a results and calculated penalties are:

4.54% Fuel: 0 GWD/MTU keff = 1.2300 +/- 0.0002 48 GWD/MTU keff = 0.8709 + 0.0002 2.75% Fuel: 0 GWD/MTU keff = 1.0797 + 0.0002 25 GWD/MTU koff = 0.8698 +/- 0.0002 Penalty for 4.54% fuel at 48 GWD/MTU = 0.05*(1.2300 - 0.8709) = 0.0180 Ak Penalty for 2.75% fuel at 25 GWD/MTU = 0.05*(1.0797 - 0.8698) = 0.0105 Ak For C-rack with partial loading (3-of-4) pattern, KENO-V.a results and calculated penalties are:

4.54% Fuel: 0 GWD/MTU krff = 1.0489 +/- 0.0003 30 GWD/MTU keff = 0.8434 +/- 0.0003 Penalty for 4.54% fuel at 30 GWD/MTU = 0.05*(1.0489 - 0.8434) = 0.0103 Ak For E-rack with full loading (4-of-4) pattern, KENO-V.a results and calculated penalties are:

4.54% Fuel: 0 GWD/MTU keff = 1.1622 +/- 0.0003 38 GWD/MTU keff= 0.8756 + 0.0003 3.30% Fuel: 0 GWD/MTU keff = 1.0749 + 0.0003 25 GWD/MTU krff = 0.8661 +/- 0.0003 Penalty for 4.54% fuel at 38 GWD/MTU = 0.05*(1.1622 - 0.8756) = 0.0143 Ak Penalty for 3.30% fuel at 25 GWD/MTU = 0.05*(1.0749 - 0.8661) = 0.0104 Ak For E-rack with partial loading (3-of-4) pattern, KENO-V.a results and calculated penalties are:

4.54% Fuel: 0 GWD/MTU k~ff = 0.9998 +/- 0.0004 19 GWD/MTU krff = 0.8653 +/- 0.0003 Penalty for 4.54% fuel at 19 GWD/MTU = 0.05*(0.9998 - 0.8653) = 0.0067 Ak The calculated penalties are summarized in Table 3-6.

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit B.2 Legacy Fuel Storage Several assemblies are legacy fuel from very early cycles. A number of assemblies may have had lumped burnable absorber pins in empty tubes and other assemblies may have had fuel rods replaced with either stainless steel rods or empty pin cells. These fuel configurations were examined in Section B. 1.3 of Reference [8]. The presence of guide tubes with burnable poison pins or empty pin cells may result in a reactivity increase as much as 0.006 Ak. The effect of actinide buildup due to the presence of burnable poisons during depletion and subsequent burnable poison removal is small and estimated by an additional 0.006 Ak penalty. The continued storage of batches A through K in Region 1 is acceptable, if a 1.0 GWD/MTU penalty is subtracted from the burnup as indicated by the core monitoring system to meet the requirements set forth in Section 6.0 of this report.

This was determined by examining fuel depletions of similar enrichment which indicates that this burnup penalty covers the approximately 0.6% Ak reactivity bias of these assemblies.

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit APPENDIX C: KENO.V-A TOLERANCE CALCULATIONS This appendix includes the details of the system and tolerance studies that define the additional data for the K 95/9 5 equation.

C.1 System Bias (Aksys and asys)

These are the calculations that define the biases on the reactivity calculations that are not considered random variation. Effects that could lead to such biases are:

• effects of control blade insertion during depletion,

• fuel rack swelling,

• the effect of residual carbon (remaining from the degraded Carborundum),

• rack interaction effects,

• modifided fuel assemblies and failed fuel storage,

• the use of NFBC in required empty cells,

• pool temperature,

• fuel assembly compression,

• storage of control blades in E-Rack, aiid

• proximity to the elevator/fuel inspection station.

These effects are represented in the K 9 5/95 equation by Aksys and *sy, (see Section 3.5.1).

C.1.1 Effects of Control Blade Insertion during Depletion Although typical operation is with all control blades fully withdrawn, certain plant maneuvers require operation with some of the control blades either partially or fully inserted, in accordance with Section 2.2 of the Core Operation and Limits Report (COLR). Prolonged operation with control blades either partially or fully inserted is atypical of PWR full power operation and is only typically realized during power ascensions or decents. To conservatively capture the spectral effect resulting from operation with a control blade adjacent to the stored assembly, 1 GWD/MTU burnup of the stored assembly's total burnup is modeled with the adjacent control blade fully inserted. The period of that depletion (in the presence of the control blade) over the life of the stored assembly is chosen to affect the highest keff of the stored assembly.

The effect of operation with control rods inserted for 1 GWD/MTU was examined using CASMO-3 and KENO-V.a. The effect was determined by modeling the assembly in the normal depletion mode in CASMO-3, but for one period with an assembly-average burnup of 1 GWD/MTU with a control rod inserted along all 10 nodes, as well as the 'average assembly' values. The same axial power shape was assumed during rodded operation as in the depletion. The rod insertion was examined at both end of life (EOL) and middle of life (MOL) for both the 30 Page 116

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit GWD/MTU and 48 GWD/MTU depletions of 4.54% enriched fuel. For example, CASMO-3 results obtained for several axial nodes are summarized in Table C-1 for a 4.54% assembly at 48 GWD/MTU.

Table C-1: CASMO-3 Nodal Values of Kinf - 48 GWD/MTU at 4.54%

Node 1 Node 3 Node 5 Node 7 Node 10 Assembly Nodal Bumnup 27.50 51.17 52.86 51.28 24.58 48.00 (GWD/MTU)

Base Case 1.00726 0.90784 0.90672 0.92859 1.10919 0.93727 Blade Inserted 1.00752 0.90831 0.90720 0.92908 1.10940 0.93774 MOL MOL -Ak 0.00026 0.00047 0.00048 0.00049 0.00021 0.00047 Blade Inserted 1.00709 0.90886 0.90765 0.92944 1.10875 0.93786 EOL EOL -Ak -0.00017 0.00102 0.00093 0.00085 -0.00044 0.00059 The results show that an EOL insertion of the rod has a greater effect than a MOL insertion. This is apparently due to the effects burning out with additional depletion; thus, control blade insertion at BOL is also bounded and was not analyzed. The overall effect, though, is very small. While some of the center nodes may show an increase of 0.1% Ak, the overall effect based on the assembly average is about 0.05% Ak. When the isotopes from the cases with control rod insertion are used in KENO-V.a, the effect is little more than the value of 2o uncertainty of the code. The KENO-V.a cases were run at 850 ppm dissolved boron. The effect is small but distinguishable:

Base Case: 48 GWD/MTU, 4-of-4 loading, 4.54%, 850 ppm, keff = 0.8709 +/- 0.0002 MOL Insertion: 48 GWD/MTU, 4-of-4 loading, 4.54%, 850 ppm, klff = 0.8716 +/- 0.0002 EOL Insertion: 48 GWD/MTU, 4-of-4 loading, 4.54%, 850 ppm, keffr 0.8717 - 0.0002 The effect at 30 GWD/MTU with 3-of-4 loading is similar:

Base Case: 30 GWD/MTU, 3-of-4 loading, 4.54%, 850 ppm, keff = 0.8434 +/- 0.0003 MOL Insertion: 30 GWD/MTU, 3-of-4 loading, 4.541%, 850 ppm, kff = 0.8437 + 0.0003 EOL Insertion: 30 GWD/MTU, 3-of-4 loading, 4.54%, 850 ppm, kcff = 0.8434 +/- 0.0003 To account for potential control blade insertion issues, then, a penalty of 0.001 Ak will be added to the final value of K 9 5/95 to account for this phenomenon for the burned fuel. Although KENO-V.a calculations were only generated for C-rack, the penalty is also applicable to E-rack. Fresh fuel values will not need this penalty since, by definition, they have no control blade exposure history.

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit C.1.2 Fuel Rack Swelling As discussed in Section 3.3.5 (Swelling Model), three swelling models were examined. In the first, the outer stainless steel wall is displaced to the outer limit of the cell. The second is where the stainless steel wall on the interior moves inward until it rests against the assembly envelope, and the third is where movement of both walls occurs. In all three models, the metal mass is conserved and the gap between walls is fully voided. For C-rack, cases were run with 4.54% at 48 GWD/MTU and 4-of-4 loading and 30 GWD/MTU with 3-of-4 loading.

Additional cases with fresh 1.35% fuel and 4-of-4 loading were also run. All cases were run at 850 ppm dissolved boron; the results are summarized in Table C-2.

Table C-2: 'C' Rack Wall Bowing Results wt% U-235 Pattern Walls keff a Ak (GWD/MTU)

Nominal 0.8709 0.0002 -

Inner Bow 0.8704 0.0002 -0.0005 4.54 48 4-of-4 Outer Bow 0.8718 0.0002 0.0009 Both Bow 0.8705 0.0002 -0.0004 Nominal 0.8434 0.0003 -

Inner Bow 0.8426 0.0003 -0.0008 4.54 30 3-of-4 Outer Bow 0.8434 0.0003 0.0 Both Bow 0.8435 0.0003 0.0001 Nominal 0.8292 0.0002 -

Inner Bow 0.8296 0.0002 0.0004 1.35 0 4-of-4 Outer Bow 0.8300 0.0002 0.0008 Both Bow 0.8300 0.0002 0.0008 The results show that there is no identifiable trend as to one model being more restrictive than another. The agreement within the same enrichment and burnup groupings shows differences between +0.0009 Ak of the nominal case. This would be expected since all cases use the same mass of wall material, and with no moderation in the gap region, there is no distinction as to flux-exposure due to the physical placement of the wall material.

As such, no penalty will be taken for wall bowing and all cases will be run at nominal configurations.

For E-rack, cases were run with 4.54% at 38 GWD/MTU and 4-of-4 loading and 19 GWD/MTU with 3-of-4 loading. Additional cases with fresh 1.48% fuel and 4-of-4 loading, fresh 2.35% fuel, and 3-of-4 loading were also run. All cases were run at 850 ppm dissolved boron; the results are summarized in Table C-3.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table C-3: 'E' Rack Wall Bowing Results wt% U-235 Pattern Walls keff O" Ak (GWD/MTU)

Nominal 0.8756 0.0003 -

Inner Bow 0.8742 0.0003 -0.0014 4.54 38 4-of-4 Outer Bow 0.8745 0.0003 -0.0011 Both Bow 0.8761 0.0003 0.0005 Nominal 0.8653 0.0003 -

Inner Bow 0.8661 0.0003 0.0008 4.54 19 3-of-4 Outer Bow 0.8649 0.0003 -0.0004 Both Bow 0.8656 0.0003 0.0003 Nominal 0.8145 0.0002 -

Inner Bow 0.8145 0.0003 0.0 1.48 0 4-of-4 Outer Bow 0.8139 0.0002 -0.0006 Both Bow 0.8158 0.0003 0.0013 Nominal 0.8336 0.0003 -

Inner Bow 0.8336 0.0003 0.0 2.35 0 3-of-4 Outer Bow 0.8338 0.0003 0.0002 Both Bow 0.8343 0.0003 0.0007 The results show that there is no identifiable trend as to one model being more restrictive than another. The agreement within the same enrichment and bumup groupings shows differences between +/-0.0014 Ak of the nominal case. This would be expected since all cases use the same mass of wall material, and with no moderation in the gap region, there is no distinction as to flux-exposure due to the physical placement of the wall material.

As such, no penalty will be taken for wall bowing and all cases will be run at nominal configurations.

Section 3.3.5 contains further information on the swelling model.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit C.1.3 Effects of Residual Carbon While the base model takes credit for neither the Carborundum B 4C absorber material nor for any moderator material in the walls of the rack, it is also prudent to examine the effects from having some residual carbon left in the gaps. For this purpose, the poison plates are modeled with their original dimensions but containing only the carbon from the B 4C with a density of 0.2720 g/cc, which is surrounded by void. The effect of residual carbon was examined for all three loading patterns, 4-of-4, 3-of-4, and 2-of-4 (region IA only). It was then examined to see if it impacted the results of wall bowing. The change in reactivity from adding the residual carbon is shown in Table C-4 and Table C-5 for Rack 'C', and in Table C-6 and Table C-7 for Rack 'E'. All cases were run at 850 ppm dissolved boron.

Table C-4: 'C' Rack Effect of Residual Carbon with Loading Pattern wt% U-235 Burnup (GWD/MTU) Pattern Model keff a Ak Void 0.8709 0.0002 -

4.54 48 4-of-4 Carbon 0.8710 0.0002 0.0001 Void 0.8434 0.0003 -

4.54 30 3-of-4 Carbon 0.8452 0.0003 0.0018 Void 0.8242 0.0003 -

4.54 0 2-of-4 Carbon 0.8253 0.0003 0.0011 Void 0.8414 0.0003 -

2.10 0 3-of-4 Carbon 0.8428 0.0003 0.0014 Void 0.8292 0.0002 -

1.35 0 4-of-4 Carbon 0.8293 0.0002 0.0001 Page 120

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table C-5: 'C' Rack Effect of Residual Carbon with Wall Bowing wt% U-235

________(GWD/MTU) Burnup Pattern Model Walls kff a Ak Void Nominal 0.8709 0.0002 -

Carbon Nominal 0.8710 0.0002 0.0001 Void Inner Bow 0.8704 0.0002 -

Carbon Inner Bow 0.8708 0.0002 0.0004 4.54 48 4-of-4 Void Outer Bow 0.8718 0.0002 -

Carbon Outer Bow 0.8716 0.0002 -0.0002 Void Both Bow 0.8705 0.0002 Carbon Both Bow 0.8713 0.0003 0.0008 Void Nominal 0.8434 0.0003 -

Carbon Nominal 0.8452 0.0003 0.0018 Void Inner Bow 0.8426 0.0003 -

Carbon Inner Bow 0.8446 0.0003 0.0020 4.54 30 3-of-4 Void Outer Bow 0.8434 0.0003 -

Carbon Outer Bow 0.8462 0.0003 0.0028 Void Both Bow 0.8435 0.0003 -

Carbon Both Bow 0.8447 0.0003 0.0012 Table C-6: 'E' Rack Effect of Residual Carbon with Loading Pattern wt% U-235 Burnup Pattern Model kff ar Ak (GWD/MTU)

Void 0.8756 0.0003 4.54 38 4-of-4 Carbon 0.8768 0.0003 0.0012 Void 0.8653 0.0003 -

4.54 19 3-of-4 Carbon 0.8672 0.0003 0.0019 Void 0.8336 0.0003 -

2.35 0 3-of-4 Carbon 0.8348 0.0003 0.0012 Void 0.8145 0.0002 -

1.48 0 4-of-4 Carbon 0.8150 0.0003 0.0005 Page 121

A AR EVA Doc'ument No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table C-7: 'E' Rack Effect of Residual Carbon with Wall Bowing wt% U-235 Burnup (GWD/MTU) Pattern Model Walls keff a Ak Void Nominal 0.8756 0.0003 -

Carbon Nominal 0.8768 0.0003 0.0012 Void Inner Bow 0.8745 0.0003 -

Carbon Inner Bow 0.8752 0.0003 0.0007 4.54 38 4-of-4 Void Outer Bow 0.8761 0.0003 -

Carbon Outer Bow 0.8766 0.0003 0.0005 Void Both Bow 0.8742 0.0003 -

Carbon Both Bow 0.8761 0.0003 0.0019 Void Nominal 0.8653 0.0003 -

Carbon Nominal 0.8672 0.0003 0.0019 Void Inner Bow 0.8649 0.0003 -

Carbon Inner Bow 0.8671 0.0003 0.0022 4.54 19 3-of-4 Void Outer Bow 0.8656 0.0003 -

Carbon Outer Bow 0.8673 0.0004 0.0017 Void Both Bow 0.8661 0.0003 -

Carbon Both Bow 0.8673 0.0003 0.0012 For C-rack, the results show that the inclusion of carbon is neutral when the rack is full (i.e., 4-of-4 pattern).

When the rack is partially full ('3-of-4' or '2-of-4) there is a small but noticeable increase in reactivity.

Therefore, a penalty of 0.003 Ak will be added to the values of K95/ 95 for '3-of-4' and '2-of-4' cases. E-rack results show a small but noticeable reactivity increase for all cases; therefore, a penalty of 0.003 Ak will be added to the values of K 95 /9 5 for all cases.

C.1.4 Rack Interaction Models This section describes the rack interface models to support the results presented in Section 4.7. The Region 2 rack geometry is needed to perform a rack interface model and is more complicated than either of the racks in Region

1. The model must split the rack into unit arrays that in this case requires a portion of the fabricated rack cell to be modeled in the inter-box cell. The cut off portion encompasses a large portion of the Boraflex gap region (henceforth referred to as the gap region).

The fabricated box model is the least complicated because it is simply a stainless steel box with a small slice of the gap region. Table C-8 lists the dimensions in the model.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table C-8: Fabricated Box Model Dimensions Component in Cumulative cm 1/2 cm Cell ID 9.00 9.00 22.860 11.43 Box Wall thickness 0.075 9.15 23.241 11.6205 Gap/wrapper 0.010 9.17 23.292 11.6459 Gap length 7.400 7.400 18.796 9.398 Gap/wrap box I horizontal length 9.17 23.2918 11.6459 Gap/wrap box I vertical length 9.15 23.241 11.6205-The inter-box model is more complicated due to the different geometry of the gap/wrapper on each side. Table C-9 lists the dimensions for the inter-box model.

Table C-9: Inter-Box Model Dimensions Component [ in Cumulative cm 1/2 cm Cell ID 9.066 9.066 23.028 11.51382 Wrapper 0.020 9.106 23.129 11.56462 Gap 0.022 9.15 23.241 11.6205 Gap/wrapper 0.010 9.17 23.292 11.6459 Gap length - 7.400 18.796 9.398 Gap+wrapper 7.44 18.898 9.4488 Gap/wrap box 1 horizontal length 9.17 23.2918 11.6459 Gap/wrap box I vertical length 9.066 23.02764 11.51382 This arrangement works fine for an infinite rack array. However, this model is being developed for an evaluation of the possible coupling between the Region I and Region 2 racks. Thus, edge units must be developed to provide a finite rack array. For this evaluation it is assumed that the Region 2 rack will reside to the left of the Region 1 rack. Thus, right edges are needed to terminate the rack. Figure C-I illustrates an expanded section of the KENO-V.a model of the fabricated and inter-boxes at the edge of the rack.

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A AREVA Document No.: ANP-2858NP-003 Palisades SEP Region 1 Criticality Evaluation with Burnup Credit Figure C-1: Sketch of KENO-V.a Model at Edge of Region 2 Racks C.1.4.1 'C' Rack Interaction Combined Models The 'C' rack interaction model uses the nominal model for the 'C' rack and the Region 2 model discussed previously. The nominal separation distance between the two regions is 2.43" +/- 0.25" that gives a minimum separation of 2.18" (5.5372 cm). The 'C' rack interaction distance uses the minimum separation distance in the model of the two racks. The 'C' rack is modeled as a lOxl0 array in a 2-of-4 loading pattern. The model extends 102.5" in the y direction based upon the 10.25" pitch. The Region 2 rack is modeled as an 1lxl0 array with a y distance of 100.87" based upon the 9.17" pitch. To provide common y-direction values for the joint array, a 1.63" (4.1402 cm) water gap is placed at the top of the array. This is slightly larger than the -1.438" gap between two modules; however, it is within the 0.25" uncertainty in placement. Figure C-2 provides a sketch of the model (note only 2 of the 10 axial rows are shown to enable enlargement of the sketch). The two separated racks have a 12" water reflector in the x and z directions. The y-direction has a periodic condition to simulate an infinite rack in that dimension.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure C-2: Sketch of a Portion of the 'C'-Region 2 Model C.1.4.2 'E' Rack Interaction Combined Models The 'E' rack interaction model uses the nominal model for the 'E' rack and the Region 2 model discussed previously. The nominal separation distance between the two regions is 3.58" +/- 0.25". The 'E' rack interaction distance uses the nominal separation distance in the model of the two racks. The 'E' rack is modeled as a 5x10 array in the loading pattern defined in Section 4.4. The model extends 53.45" in the y direction based upon the 10.69" y-pitch. The Region 2 rack is modeled as a 6x7 array with a y distance of 55.02" based upon the 9.17" pitch. To provide common y-direction values for the joint array, a 1.57" (3.9878) water gap is split over the top and bottom of the 'E' rack. Figure C-3 provides a sketch of the model (note only 2 of the axial rows are shown to enable enlargement of the sketch). The two separated racks have a 12" water reflector on all sides. Note the lack of top/bottom plates in the Region 2 model is assumed to have an insignificant effect on results.

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A AREVA Document No.: ANP-2858NP-003 Palisades SEP Region 1 Criticality Evaluation with Burnup Credit Figure C-3: Sketch of a Portion of the Region I E -Region 2 Model C.1.5 Modified Fuel Assemblies and Failed Fuel Storage There are a number of items besides fuel assemblies in C-Rack. Some contain fuel rods, others are Non-Fuel Bearing Components (NFBC, see Section C. 1.6). Each of these requires consideration on their impact on criticality. Also, they are all currently constrained to the 'fresh fuel' part of the rack where they are loaded in a 2-of-4 arrangement. It is desired that they be allowed storage in the 3-of-4 and 4-of-4 areas of the rack. The items to be examined which contain fuel are:

S Permanent Failed Fuel Rod Storage Container (PFFC) 0 Failed Fuel Container (FCAN)

S Shield Assemblies (low enriched with Stainless Steel rods in outer rows)

S Reconstituted Assemblies S STOR1-5 These are analyzed here in 3-of-4 and 4-of-4 configurations in the C-Rack. For a 4-of-4 arrangement the items are placed in a rack containing 4.54% enriched fuel at 48 GWD/MTU and 850 ppm dissolved boron, with a base case k~ff = 0.8709 +/- 0.0002, and a K 9 5/9 5 value of 0.9079. For a 3-of-4 arrangement the items are placed in a rack Page 126

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit containing 4.54% enriched fuel at 30 GWD/MTU at 850 ppm dissolved boron, with a base case keff = 0.8434 +

0.0003, and a K95/95 value of 0.8752. These will be used as the bases for examining the impact of the above components. For fuel bearing components in a 3-of-4 arrangement, they are only considered to replace a fuel assembly.

PFFC The Permanent Failed Fuel Rod Storage Container has 48 cells to hold failed rods. While it is possible for a cell to hold more than one, it is administratively prohibited from doing so. The PFFC was previously analyzed with 56 rods in both wide- and close-packed arrays with enrichments up to 4.95%. The wide-packed array was essentially an array of 56 fuel rods roughly equivalent to an every-other location of a fuel assembly (hence rods are spaced 2 standard pitches apart). This was found to be more restrictive than the close-packed array that was examined. As such, only the wide-packed array is examined here. Results are summarized in Table C-10.

Table C-1O: 'C' Rack Results for PFFC Storage Description KIf- Gk K 9 5/ 9 5 Base C-Rack 4-of-4, 4.54%, 48 GWD/MTU, 850 ppm 0.8709 0.0002 0.9079 PFFC in fuel location of 4-of-4 0.8691 0.0002 0.9061 Base C-Rack 3-of-4, 4.54%, 30 GWD/MTU, 850 ppm 0.8434 0.0003 0.8752 PFFC in empty cell of 3-of-4 0.8542 0.0003 0.8860 PFFC in fuel location of 3-of-4 0.8407 0.0003 0.8725 The PFFC in a 4-of-4 arrangement has a v'alue of keff less than the base case, so it is bounded by the 4-of-4 analysis, and may replace a fuel assembly in that configuration. The PFFC in a 3-of-4 arrangement replacing a fuel assembly has a value of keff less than the base case, so it is bounded by the 3-of-4 analysis, and may replace a fuel assembly in that configuration. The PFFC in a 3-of-4 arrangement actually is not allowed in an empty cell because it is a fuel bearing component. The results, though, show that if placed in an empty cell, the value of K 95 / 95 is still below the allowable limit and does not create a new un-analyzed accident condition.

Failed Fuel Container (FCAN)

The 'C' rack also contains a 'two-place' arrangement holding a failed fuel pin. The container comprises two stainless steel tubes with a center-to-center separation of 3.5" and a funnel attached to the top of each tube. The separator between the two tubes has subsequently been removed so that the tube/funnels are now separate pieces.

This container can contain up to 4.95 wt% fuel pins, is bounded by the PFFC, and must be stored in a fuel location.

Shield Assemblies The shield assemblies are assemblies that contain low enriched or depleted Uranium rods with two rows of stainless steel rods on two opposite sides of the assembly. The enrichment is about 1.2 wt% for the older SANx assemblies and is only about 0.3 wt% for the later shield assemblies that contain depleted Uranium rods, so the shield assemblies are easily bounded by any of the normal assemblies. SAN8 has been modified by swapping some of the stainless steel rods with fuel rods taken from other assemblies; these rods are high burnup. Other shield assemblies may be modified in a similar manner in the future. Modified shield assemblies remain bounded by the reactivity of an intact donor assembly due to the low enrichment of the other rods. Modified shield Page 127

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit assemblies may be stored in any location that an assembly from which the highest reactive rod was swapped may be stored without violating the criticality safety criterion.

Reconstituted Assemblies These are high bumup reconstituted assemblies that had a few fuel pins removed and replaced with stainless steel or inert (i.e., zirc pellets inside the cladding) pins. Due to the high bumup of these assemblies and the small number of pins involved, these assemblies may be stored in any location that their enrichment and bumup allow.

In comparison to the non-reconstituted fuel assemblies, these have the same geometry and the same amount of water in the fuel assembly envelope. The stainless steel or inert rods act as non-reactive fuel; therefore the assembly reactivity would be lower than a normal assembly with the same enrichment and burnup, since it contains less fuel. As such, they would be bounded by a normal assembly of the same enrichment and bumup.

The assembly-average enrichment and bumup that should be used to determine the allowable placement of reconstituted assemblies should be based on the active fuel pins, and neither parameter should be decreased by averaging-in the number of stainless steel or inert pins. No empty water holes are allowed in these assemblies.

STORI-5 STOR1-4 may be treated as Batch H type assemblies and do not require further analysis. STOR-5 is only partially full and may be used to hold additional rods in the future. As such, it should be handled as a fresh fuel assembly.

C.1.6 NFBC Models NFBC, as described in Section B. 1.2 of Reference [8], were analyzed for storage in the 3-of-4 and 4-of-4 areas of the C-Rack, and the results are shown in Table 4-15 and Table 4-16 of this document.

C.1.7 Moderator Temperature Effects The moderator temperature for the rack analysis was set to 273 K. This was done since an earlier study showed that reactivity was highest at low temperatures, and that reactivity monotonically decreased with increasing temperature. Several check cases were run to verify that this observation is also valid here.

Several KENO-Va cases were re-run at higher temperatures. The 4.54% enriched, 48 GWD/MTU set was examined here, varying moderator temperature up to 200 'F (366.49 K). The following compilation of water density versus temperature was employed:

60 'F 288.72 K, density = 0.999280 g/cc 100 'F = 310.94 K, density = 0.993085 g/cc 160 'F = 344.27 K, density = 0.977332 g/cc 200 °F = 366.49 K, density = 0.962648 g/cc Page 128

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit The base case for comparison is 4.54% at 48 GWD/MTU and 850 ppm dissolved boron with a value of keff =

0.8709 +/- 0.0003. The deck was modified by changing the density and temperature for material 3 (moderator).

The temperatures for other materials were not changed since most do not have a temperature dependence in the tablesets, and those that do show little change in resonance absorption at these relatively small changes in temperature.

The results showed:

60 OF, keff = 0.8705 +/- 0.0002 100 OF, kcff-= 0.8696 + 0.0002 160 OF, keff = 0.8681 +/- 0.0002 200 OF, keff = 0.8666 +/- 0.0002 These results show that reactivity decreases monotonically with increasing moderator temperature. As such, no reactivity penalty needs to be applied due to uncertainty in moderator temperature.

C.1.8 Fuel Assembly Compression The effect of moving the walls toward or away from the fuel was examined in Section C. 1.2. The further question was raised as to what the impact would be if the inward bowing of the wall was sufficient to change the geometry of the fuel assembly. This section, then, examines the effect on reactivity if inner wall bowing was severe enough to compress a fuel assembly.

This analysis assumes that each pin cell is compressed in a uniform manner. That is, the fuel pin does not change dimensions, but the water cell surrounding it decreases by a fixed amount uniformly in the x and y directions.

Two amounts of decrease were chosen, one being a total decrease of 0.2cm (0.1 cm on a side) and 0.1 cm (0.05 cm on a side). Fuel with 48 GWD/MTU bumup and 4.54% enrichment was used as a basis here. The moderator contained 850 ppm of dissolved boron.

The results were:

0.2 cm decrease in cell: kcff = 0.7824 + 0.0002 0.1 cm decrease in cell: kcff = 0.8382 +/- 0.0002 Both are significantly less than the base case value of krff = 0.8709 +/- 0.0002, so any decrease in cell pitch due to assembly compression would result in a decrease in reactivity. As such, this effect will not impact the results of this analysis.

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A AREVA Document No.: ANP-2858NP-003 Palisades SEP Region 1 Criticality Evaluation with Burnup Credit C.1.9 Storage of Control Blades in E-Rack KENO-Va is incapable of exactly modeling the cruciform control blades in their actual configuration - a sort of "X" inside the square rack cell. Control blades are modeled as a "+" inside the rack cell as an approximation.

The AIC material is assumed to be completely depleted and replaced with void. Credit for only the stainless steel cladding is taken in the cell model, which is pictured in Figure C-4.

Figure C-4: As-Modeled Control Blade in E-Rack Cell For the 4-of-4 configuration, two calculations are run. The first is for the rack full of 4.54 wt% burnt fuel at 38 GWD/MTU and 0 ppm of dissolved boron. This case is used as it is the most reactive configuration. As would be expected, reactivity decreases when a fuel assembly is replaced by a control blade. For the 3-of-4 configuration, three cases are run. The first is the limiting 3-of-4 model with 4.54 wt% fuel burnt to 19 GWD/MTU and 0 ppm of dissolved boron. The second case adds a single control blade to the rack, in location B57. The third case fills all available locations with control blades. The results are summarized in Table C-1 1.

Table C-11: E-Rack Control Blade Storage Results 4-of-4 Loading, 4.54 wt%, 38 GWD/MTU, 0 ppmB Control Blades k~ff 1k None (Base) 0.9516 0.0003 1 at C57 0.9365 0.0003 3-of-4 Loading, 4.54 wt%, 19 GWD/MTU, 0 ppmB Control Blades kff gk None (Base)

• 0.9451 0.0001 I at B57 0.9454 0.0001 All empty locations 0.9473 0.0001 This result differs from the deboration result listed in Table 4-10 (0.9445 +

0.0003) because of differences in the number of particle histories, as suggested by the different a values.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit The water displacement is not completely off-set by the additional neutron absorption in stainless steel when control blades are inserted into previously-empty rack cells. Based on these results, a penalty of 0.0025 on klff is required for the 3-of-4 configuration. No penalty is needed for the 4-of-4 configuration.

C.1.10 Proximity to the Elevator/Fuel Inspection Station The fuel elevator and fuel inspection station is adjacent to the C-Rack. The region is surrounded on 3 sides by C-Rack cells, being 2+ cells deep in the 'x' direction and 4 to 6 cells deep in the 'y' direction. There is a concrete wall on the remaining side. There is no voiding around the elevator and inspection station as the elevator is a single walled stainless steel can and the inspection station is open to the pool water. The regions surrounding the inspection station are modeled with both 4-of-4 loading with 4.54% fuel at 48 GWD/MTU and 3-of-4 loading with 4.54% fuel at 30 GWD/MTU. The inspection station is first modeled as being empty, and then it is modeled again with two fuel assemblies surrounded only by water in the near proximity to the fuel in the rack. The elevator and inspection station are separated by significantly more than the 10.25" spacing of the C-Rack, so the model is conservative. Two fuel assemblies are modeled, assuming there is one each in the elevator and in the inspection station. For the 4-of-4 models, the assemblies are modeled adjacent to each other. In the 3-of-4 model, they are examined both being next to each other (which places one next to a rack cell with a fuel assembly and one next to an empty rack cell), and also separated by one rack cell space so that each are next to a fuel assembly.

The dissolved boron content is set to 850 ppm when there are no assemblies in the inspection station. When the two assemblies are modeled, though, the boron concentration is conservatively set to 1350 ppm since the minimum required by Technical Specification 3.7.15 is 1720 ppm. Fresh fuel assemblies are conservatively placed next to the C-Rack. This is conservative since the location of the elevator and inspection station would largely water isolate the assemblies from the rack cells and from each other. Results are summarized in Table C-12.

Table C-12: Elevator and Fuel Inspection Station Results Description krrf Cyk K 9 5 /9 5 Base C-Rack 4-of-4, 4.54%, 48 GWD/MTU, 850 ppm 0.8709 0.0002 0.9079 Empty elevator/inspection station with fuel in a 4-of-4, 0.8269 0.0003 0.8639 4.54%, 48 GWD/MTU, 850 ppm Two assemblies in the inspection station with fuel in a 0.7972 0.0003 0.8342 4-of-4, 4.54%, 48 GWD/MTU, 1350 ppm Base C-Rack 3-of-4, 4.54%, 30 GWD/MTU, 850 ppm 0.8434 0.0003 0.8752 Empty elevator/inspection station with fuel in a 3-of-4, 0.8330 0.0003 0.8648 4.54%, 30 GWD/MTU, 850 ppm Two adjacent assemblies in the inspection station with 0.8291 0.0004 0.8609 fuel in a 3-of-4, 4.54%, 30 GWD/MTU, 1350 ppm Two non-adjacent assemblies in the inspection station with fuel in a 3-of-4, 4.54%, 30 GWD/MTU, 1350 0.7987 0.0003 0.8305 ppm The results show that for the 4-of-4 configuration, the value of K 95 /9 5 is lower than the nominal condition. For the 3-of-4 configuration, the value of K 9 5/95 is slightly higher than the base condition, but is still below the allowable limit. As such, the activities in the elevator/inspection station do not restrict the margin to safety for the C-Rack.

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A AREVA Document No.: ANP-2858NP-003 Palisades SEP Region 1 Criticality Evaluation with Burnup Credit C.2 Statistical Tolerance Studies for Akto, and crto, This section describes the details of the random varying parameters that contribute to Ak,01 and to 0 1. When multiple conditions are run for the same tolerance, the maximum positive value is used and is in bold face. The positive values of these tolerances are listed in the summary tables in Section 3.5.3.

C.2.1 Planar Enrichment and Assembly Placement The planar enrichment study was documented in Section B.2.1 of Reference [8], and showed that the average enrichment model for the 4-of-4 rack loading is conservative, and remains applicable for this application.

C.2.2 Rack Tolerance Studies For the tolerance calculations, the four-of-four loading configuration bounds the three-of-four loading configuration, as shown in Tables B-12 and B-13 of Reference [8]. The detailed results of the rack tolerance calculations are listed in Table C- 13 for the C-Rack and Table C- 14 for the E-Rack using nominal geometry (no swelling).

Note that for the E-Rack tolerances it was necessary to examine the impact of fuel assemblies shifting toward or away from each other in the rack. This was because the E-Rack was designed specifically to hold assemblies which may experience dimensional problems and so were made with wide clearances between the inner wall and envelope of the assemblies; this allows for the assemblies to shift. In C-Rack, the tolerance is very tight (only about 0.155 in) not allowing free movement of the assemblies. The effects in E-Rack from assembly displacement were found to be very minor. The reduced clearance in C-Rack would make this impact even smaller. As such, the shifting of C-Rack fuel was not examined here.

Table C-13: Rack 'C' Nominal Tolerance Results Description of Case I k~ff I 'k Ak to base Base C Rack 4-of-4 1.3321 0.0001 -

Inner Box Wall Thickness Inside +0.01" 1.3294 0.0001 -0.0027 Inner Box Wall Thickness Inside -0.01" 1.3347 0.0001 0.0026 Inner Box Wall Thickness Outside -0.01" 1.3349 0.0001 0.0028 Outer Box Wall Thickness Inside +0.01" 1.3348 0.0001 0.0027 Outer Box Wall Thickness Outside +0.01" 1.3289 0.0001 -0.0032 Outer Box Wall Thickness Outside -0.01 1.3348 0.0001 0.0027 Cell Pitch +0.04" 1.3318 0.0001 -0.0003 Cell Pitch -0.04" 1.3322 0.0001 0.0001 SS rod OD -0.005" 1.332 0.0001 -0.0001 Page 132

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table C-14: Rack 'E' Nominal Tolerance Results Description of Case [ keff I ak J Ak to base Base E Rack 4-of-4 1.2600 0.0002 -

Inner Box Wall Thickness Inside +0.01" 1.2611 0.0001 0.0011 Inner Box Wall Thickness Inside -0.01" 1.2622 0.0001 0.0022 Inner Box Wall Thickness Outside +0.01" 1.2581 0.0001 -0.0019 Inner Box Wall Thickness Outside -0.01" 1.2620 0.0001 0.0020 Outer Box Wall Thickness Inside +0.0 1" 1.2478 0.0002 -0.0022 Outer Box Wall Thickness Inside -0.01" 1.2621 0.0002 0.0021 Outer Box Wall Thickness Outside +0.01" 1.2579 0.0001 -0.0021 Outer Box Wall Thickness Outside -0.01" 1.2621 0.0001 0.0021 Cell Pitch +0.04" 1.2593 0.0002 -0.0007 Cell Pitch -0.04" 1.2611 0.0001 0.0011 SS rod OD +0.005" 1.2611 0.0002 0.0011 SS rod OD -0.005" 1.2591 0.0002 -0.0009 Nominal 6x10 Base

• 1.2730 0.0002 -

Off-Center FA- 4 together 1.2729 0.0001 -0.0001 Off-Center FA- 4 apart 1.2727 0.0001 -0.0003 Off-Center FA - 4 together x 15 1.2725 0.0001 -0.0005 Off-Center FA - 4 apart x 15 1.2720 0.0002 -0.0010 For evaluation of assembly displacement, it was necessary to expand the E-Rack model to a 6x10 matrix; the nominal 6x10 base keff is used for the Ak calculation for off-center FA cases.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit C.2.3 Fuel Assembly Tolerance Results The results of the assembly tolerance calculations are listed in Table C-15 for the 'C' Rack and Table C-16 for the

'E' Rack using nominal rack geometry (no swelling).

Table C-15: 'C' Rack Nominal Fuel Tolerances Description ker Ok Ak to base Base C Rack 4-of-4 1.3321 0.0001 -

Enrichment +0.05 wt% 1.3344 0.0001 0.0023 Enrichment -0.05 wt% 1.3295 0.0001 -0.0026 Theoretical Density [ 1.3324 0.0001 0.0003 Theoretical Density [ ] 1.3316 0.0001 -0.0005 Pellet OD r 1.3320 0.0001 -0.0001 Pellet OD 1.3320 0.0001 -0.0001 Clad ID r 1.3321 0.0001 0.0000 Clad ID ] 1.3320 0.0001 -0.0001 Clad OD 1.3303 0.0001 -0.0018 Clad OD 1.3336 0.0001 0.0015 Instrument Tube ID [ 1.3319 0.0001 -0.0002 Instrument Tube ID [ 1.3321 0.0001 0.0000 Instrument Tube OD [ ] 1.3322 0.0001 0.0001 Instrument Tube OD[ 1.3319 0.0001 -0.0002 Table C-16: 'E' Rack Nominal Fuel Tolerances Description kerr O'k Ak to base Base E Rack 4-of-4 1.2600 0.0002 -

Enrichment +0.05 wt% 1.2626 0.0001 0.0026 Enrichment -0.05 wt% 1.2577 0.0002 -0.0023 Theoretical Density [ ] 1.2605 0.0001 0.0005 Theoretical Density [ ] 1.2594 0.0002 -0.0006 Pellet OD 1.2599 0.0001 -0.0001 Pellet OD 1.2601 0.0002 0.0001 Clad ID 1.2602 0.0002 0.0002 Clad ID 1.2598 0.0002 -0.0002 Clad OD 1.2581 0.0002 -0.0019 Clad OD r 1.2619 0.0002 0.0019 Instrument Tube ID [ L 1.2600 0.0001 0.0000 Instrument Tube ID [ ] 1.2597 0.0001 -0.0003 Instrument Tube OD[ 1.2600 0.0001 0.0000 Instrument Tube OD [ 1.2599 0.0001 -0.0001 Pin Pitch + 1.2604 0.0002 0.0004 Pin Pitch - 1.2595 0.0002 -0.0005 Guide Bar + 1.2600 0.0002 0.0000 Guide Bar - 1.2598 0.0002 -0.0002 Page 134

A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit APPENDIX D: SPACER GRID, FUEL ROD PITCH, GUIDE BAR, AND GEOMETRY CHANGES DURING FUEL GROWTH EFFECTS D.1 Spacer Grids Criticality safety has been ensured in spent fuel racks by performing analyses using such codes as KENO-V.a.

The analyses model fuel assemblies located inside rack storage cells. It has been a typical practice to ignore spacer grids while modeling the fuel assemblies. This has been considered conservative since not modeling them replaces a weak poison (the metal of the spacer grid) with a moderator (water). The question has been asked as to whether this assumption is also valid for borated water, since the spacer grid would then be replaced with a material containing a neutron poison. This section examines this issue for the Palisades spent fuel rack.

The analysis here will start with the KENO-V.a model developed for the 'C' rack. The model will be modified to include the effects of spacer grids. This will be done in three ways.

1. The first will be to smear the mass of the grids over the length of the fuel region in the moderator within the fuel assembly. (Smeared Grid model)

2. The second will be to increase the diameter of the fuel pins to add a mass of zirconium equal to the spacer grids (hence, displace an equal volume of water as do the spacer grids). (Thick Clad model)

3. The third method will model the grids at their respective axial locations. The reactivity change from the 'no-grid' cases will be determined, and a decision made as to whether the exclusion of spacer grids is a conservative or non-conservative assumption. (Explicit model)

The following situations are modeled:

1) The 2-of-4 (i.e., checkerboard) arrangement of fuel, no boron in the Carborundum neutron absorber plates, and no dissolved boron.

2) A 3-of-4 arrangement of fuel, no boron in the Carborundum neutron absorber plates, and no dissolved boron.

1

3) A 4-of-4 (i.e., fully loaded) arrangement of fuel, no boron in the Carborundum neutron absorber plates, and no dissolved boron.

4) A 4-of-4 (i.e., fully loaded) arrangement of fuel, no boron in the Carborundum neutron absorber plates, at 850, 1720, and 2550 ppm dissolved boron.

5) A 4-of-4 arrangement, with 10% of the boron in the Carborundum neutron absorber plates remaining, plus E

850, 1720, and 2550 ppm of dissolved boron.

Results of the analysis are shown in Table D- I and demonstrate that it is conservative (or equivalent) not to model the spacer grids in KENO-V.a for criticality safety analyses. This is valid whether dissolved boron is present or not, or whether residual boron is present in the Carborundum or not.

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A ARE VA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table D-1: Spacer Grid Results Case Model Method Residual Boron Soluble Boron keff Description Content in (ppm)

Carborundum 2-of-4 No grids No boron 0 0.8646 +/- 0.0005 Smeared grids No boron 0 0.8581 +/- 0.0005 Explicit No boron 0 0.8591 +/- 0.0005 3-of-4 No grids No boron 0 1.0556 +/- 0.0005 Smeared grids No boron 0 1.0493 +/- 0.0005 Explicit No boron 0 1.0517 +/- 0.0005 4-of-4 No grids No boron 0 1.1662+/- 0.0004 Smeared grids No boron 0 1.1617 +/- 0.0004 Explicit No boron 0 1.1618 +/- 0.0004 4-of-4 No grids No boron 850 1.0480 +/- 0.0004 Smeared grids No boron 850 1.0441 +/- 0.0004 Thick Clad No boron 850 1.0452 +/- 0.0004 No grids No boron 1720 0.9552 +/- 0.0005 Smeared grids No boron 1720 0.9529 +/- 0.0004 Thick Clad No boron 1720 0.9535 +/- 0.0004 No grids No boron 2550 0.8837 +/- 0.0004 Smeared grids No boron 2550 0.8833 +/-/- 0.0003 Thick Clad No boron 2550 0.8837 +/- 0.0003 4-of-4 No grids 10% Boron remaining 850 0.9188 +/- 0.0005 Smeared grids 10% Boron remaining 850 0.9119 +/- 0.0004 Thick Clad 10% Boron remaining 850 0.9136 +/- 0.0004 Explicit 10% Boron remaining 850 0.9146 +/- 0.0004 4-of-4 No grids 10% Boron remaining 1720 0.8521 +/- 0.0004 Smeared grids 10% Boron remaining 1720 0.8479 +/- 0.0004 Thick Clad 10% Boron remaining 1720 0.8486 +/- 0.0004 Page 136

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Explicit 10% Boron remaining 1720 0.8487 +/-/- 0.0004 4-of-4 No grids 10% Boron remaining 2550 0.7989 +/- 0.0004 Smeared grids 10% Boron remaining 2550 0.7963 +/- 0.0004 Thick Clad 10% Boron remaining 2550 0.7970 +/- 0.0004 Explicit 10% Boron remaining 2550 0.7974 +/- 0.0004 D.2 Fuel Rod Pitch Tolerance Pin pitch tolerance was examined for the E-rack (Table C- 16) and found that a small (0.0004Ak) reactivity increase was seen when the pin pitch increased by 0.005 in. This pin pitch increase is not feasible for the C-Rack due to small clearances between the fuel assembly envelope and inner wall. The most pin pitch could increase would be about 0.001 inch, which based on the small reactivity seen in the E-Rack, would likely produce a reactivity difference <0.0001Ak. As such, it was decided that the very small allowable increase in pin pitch would not produce a noticeable change in reactivity for C-Rack. Also, note that fuel compression, examined in Section C. 1.8, showed large negative reactivity changes when the fuel assembly was compressed.

D.3 Guide Bars Eight guide bars are located at the outer edges of the assembly. The guide bars are irregular shaped pieces of solid Zircaloy-4. Two bars are located on each side of the fuel assembly. Figure D-1 provides a sketch of the cross section of the guide bar. The guide bars were represented in KENO-V.a by determining a minimum equivalent rectangular cross section; therefore adding more water to the under-moderated fuel assembly. The base model uses a cross sectional area of 0.1586 in2 based upon an assumption that less Zr (more water) produces conservative results. A kcff difference of less than or equal to 0.0002 was calculated for +/-0.002" changes in rectangular dimensions with KENO-V.a for fuel assembly tolerances in the E-Rack; since the effects were negligible for E-Rack, guide bar tolerances were not considered for C-Rack.

A series of cases was run to evaluate the rectangular guide bar model, which demonstrated that the equivalent rectangular cross section model was statistically equivalent to cases where the triangular cut-outs were explicitly modeled. Based on this evaluation, no further tolerance study was performed for the guide bars because of the under-moderated nature of the model.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Figure D-1: Sketch of Guide Bar (Figure is not essential - only shape is important)

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A AR EVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit D.4 Geometry Changes during Rod Growth During irradiation, fuel rods undergo geometrical changes, including clad thinning, pellet density changes, and reduction in fuel pellet/clad gap. These effects were previously studied for 14x14 CE fuel, and lessons learned from that study may be applied to the Palisades 15x15 CE fuel design.

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit APPENDIX E: EVALUATION OF CASMO3 FISSION PRODUCT UNCERTAINTY E.1 Introduction E.2 Method of Derivation I

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A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Page 141

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit E.3 Example Calculation Page 142

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit Table E-1: CASMO3 Fission Product and Actinide Cross-Section Uncertainties Page 143

A AREVA Document No.: ANP-2858NP-003 Palisades SFP Region 1 Criticality Evaluation with Burnup Credit E.4 Overall Uncertainty of 18 CASMO3 Fission Products Table E-2: Overall Uncertainty of 18 CASMO3 Fission Products Page 144