Argonne National Laboratory
Reduced Enrichment for Research and Test Reactors
Nuclear Engineering Division at Argonne
U.S. Department of Energy

Examples of LEU Conversion Analyses in the RERTR Program


M. M. Bretscher and J. L. Snelgrove


The ORR Whole-Core LEU Fuel Demonstration, conducted as part of the U.S. Reduced Enrichment Research and Test Reactor Program, has been successfully completed. Using commercially-fabricated U3Si2-Al 20%-enriched fuel elements (4.8 g U/cc) and fuel followers (3.5 g U/cc), the 30-MW Oak Ridge Research Reactor was safely converted from an all-HEU core, through a series of HEU/LEU mixed transition cores, to an all-LEU core. There were no fuel element failures and average discharge burnups were measured to be as high as 50% for the standard elements and 75% for the fuel followers. Experimental results for burnup-dependent critical configurations, cycle-averaged fuel element powers, and fuel-element-averaged 235U burnups validated predictions based on three-dimensional depletion calculations. Calculated values for plutonium production and isotopic mass ratios as functions of 235U burnup support the corresponding measured quantities. In general, calculations for 60Co and 198Au reaction rate distributions, differential and integral control rod worths, prompt neutron decay constants, and isothermal temperature coefficients were found to agree with corresponding measured values. Experimentally determined critical configurations for fresh HEU and LEU cores radially reflected with water and with beryllium are well-predicted by both Monte Carlo and diffusion calculations.

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1. INTRODUCTION (Chapters 1 to 6 in one file: 1.04 MB) 1
2. THE 30-MW OAK RIDGE RESEARCH REACTOR (Chapters 1 to 6 in one file: 1.04 MB) 3
   2.1 Description of Facility 3
   2.2 Description of Fuel Elements 3
   2.3 Description of Shim Rods 7
      2.3.1 Poison Section 7
      2.3.2 Follower Section 7
   2.4 Beryllium Reflector Elements 7
   2.5 Experiment Facilities Extraneous to Demonstration 7
      2.5.1 Beam Tubes 7
      2.5.2 Engineering Facilities 10
      2.5.3 Heavy Section Steel Technology Experiment (HSST) 10
      2.5.4 Europium and Iridium Isotope Production 10
      2.5.5 Magnetic Fusion Experiments (MFE) 10
      2.5.6 High Uranium-Loaded Fuel Element Development (HFED) Facility 10
3. SAFETY EVALUATIONS (Chapters 1 to 6 in one file: 1.04 MB)  13
4. THE EXPERIMENTAL PROGRAM (Chapters 1 to 6 in one file: 1.04 MB)      19
   4.1 Introduction 19
   4.2 Low Power Measurements 19
     4.2.1 Reaction Rate Distributions 19
     4.2.2 Control Rod Worths 21
     4.2.3 Prompt Neutron Decay Constant 23
     4.2.4 Critical Assemblies with Fresh Fuel 23
     4.2.5 Isothermal Temperature Coefficient 23
     4.2.6 Reactivity Worths of Experimental Facilities 24
   4.3 Full Power Cores 24
   4.4 Gamma-Scanning of Irradiated Full-Sized Fuel Elements 24
   4.5 137Cs Gamma-Scanning and Mass Spectrometry of Irradiated Fuel Plates 27
5. COMPUTER CODES AND MODELS  (Chapters 1 to 6 in one file: 1.04 MB) 29
   5.1 Multigroup Cross Sections (EPRI-CELL Code) 29
   5.2 Diffusion Calculations (DIF3D Code) 29
   5.3 Burnup Calculations (REBUS-3 Code) 29
   5.4 Monte Carlo Calculations (VIM Code) 32
   5.5 Transport Calculations (TWODANT Code) 33
   5.6 Calculation of Kinetic Parameters (VARI3D) Code 35
   5.7 6Li and 3He Poisons in Beryllium 35
   5.8 3D Model of the ORR 42
    5.8.1 Fuel Elements 42
    5.8.2 Shim Rod Assemblies 42
    5.8.3 Beryllium Reflector 42
    5.8.4 Experimental Facilities 42
    5.8.5 Core Box and Dummy Fuel Elements 43
6. DATA ANALYSIS METHODS  (Chapters 1 to 6 in one file: 1.04 MB) 47
   6.1 Cobalt and Gold Wire Activations 47
   6.2 Differential and Integral Shim Rod Worths 49
   6.3 Determination of Reactor Kinetic Parameters 55
   6.4 Cycle-Averaged Fuel Element Powers and 235U Burnups From Gamma-Scanning Measurements on Full-Sized Fuel Elements
    6.4.1 Methodology 58
    6.4.2 Calibration of the Gamma-Scanning System 62
    6.4.3 Transverse Gradient Corrections 63
    6.4.4 Interpretation of Fuel Follower Gamma-Scanning Measurements Made with a NaI Detector
  6.5 Fuel Element Burnups from Post-Irradiation Mass Spectrometry Measurements 72
7. CALCULATIONS VERSUS MEASUREMENTS   (File 1: 1.6 MB, File 2: 0.85 MB) 79
   7.1 Water and Beryllium-Reflected Criticals with Unirradiated Fuel 79
   7.2 Cobalt and Gold Activity Distributions 84
   7.3 Differential and Integral Shim Rod Worths 84
   7.4 Prompt Neutron Decay Constants 102
   7.5 Isothermal Temperature Coefficient 102
   7.6 Critical Configurations for the 30-MW Operating Cores Used in the Demonstration 106
   7.7 Cycle-Averaged Fuel Element Powers 109
   7.8 Fuel-Element-Averaged 235U Burnups 111
    7.8.1 Results from 137Cs Gamma-Scanning of Full-Sized Fuel Elements 111
    7.8.2 Results from Post-Irradiation Mass Spectrometry Measurements 148
   7.9 Uranium and Plutonium Isotopic Mass Ratios Versus 235U Burnup 148
   7.10 Use of Revised EPRI-CELL Libraries 148
A. Core Configurations Fuel Element Locations and BOC 235U Fuel Element Masses (816 KB) 161
B. Measured Shim Rod Withdrawal Positions at Critical for Each Core and Time Node (B to D in one file: 131 KB) 185
C. Calculated Transverse Gradient Correction Factors  (B to D in one file: 131 KB) 187
D. Models Used for the DIF3D Calculations of the Fresh-Fueled Criticals 179AXS and 179AX6 (B to D in one file: 131 KB) 191
E. Evaluation of Differential Shim Rod Worths from Measured Time-Dependent Flux Profiles (217 KB) 259
F. Evaluation of Fuel Element Powers 235U Masses and Burnups from the Gamma-Scanning of Full-Sized Fuel Elements (57 KB) 273
G. Evaluation of Gold Wire Activation Data for the Water-Reflected Core LEU-1 (519 KB) 303

Manuel M. Bretscher
Argonne National Laboratory 362
9700 South Cass Avenue
Argonne, IL 60439 USA

Phone: (630) 252-8616
Fax: (630) 252-5161

2016 RERTR Meeting

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2015 RERTR Meeting

The 2015 International RERTR Meeting (RERTR-2015) took place in Seoul, Korea on Oct. 11-14, 2015.
For more information visit RERTR-2015.

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Last modified on July 29, 2008 11:32 +0200