THE WHOLE- CORE LEU U3SI2-AL FUEL DEMONSTRATION IN THE 30-MW OAK RIDGE RESEARCH REACTOR

Examples of LEU Conversion Analyses in the RERTR Program

THE WHOLE- CORE LEU U₃SI₂-AL FUEL DEMONSTRATION IN THE
30-MW OAK RIDGE RESEARCH REACTOR

M. M. Bretscher and J. L. Snelgrove

ABSTRACT

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.

PDF version available
This document is split in downloadable PDF sections.

TABLE OF CONTENTS AND ABSTRACT (48 KB)	Page
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
	58
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
	66
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
8. SUMMARY AND CONCLUSIONS (19 KB)	155
ACKNOWLEDGMENTS	156
REFERENCES	157
APPENDICES	161
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

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

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