Joint Reactor Laboratory Course for Students in KUCA

April 2004
Tsuyoshi Misawa, Hironobu Unesaki, Chihiro Ichihara, Cheol Ho Pyeon and Seiji Shiroya

Contents

Introduction to Kyoto University Critical Assembly (KUCA)

1. General Description of the KUCA Facility  /p.1

1-1 The KUCA Facility   /p.1

1-2 Solid-Moderated Cores (A & B Cores)  /p.2

1-3 Light-Water Moderated Core (C core)  /p.3

1-4 Pulsed Neutron Source  /p.4

1-5 Control Room  /p.5

2. Detail of the Light-Water Moderated Core (C core)   /p.6

2-1 Overall Structures  /p.6

2-2 Core Tank and Grid Plate  /p.7

2-3 Fuel Plates and Fuel Frames  /p.7

2-4 Core Configurations  /p.10

Chapter 1 Approach to Criticality

1-1 Chain Reaction of Nuclear Fission, Neutron Multiplication and Approach to Criticality  /p.12

1-1-1 Fission Chain Reaction: Neutron Multiplication in a Subcritical Media  /p.12

1-1-2 Neutron Multiplication in a Subcritical Media  /p. 14

1-1-3 Inverse Count Rate and Criticality Approach  /p.15

1-2 Experiments  /p.18

1-2-1 Neutron Detectors  /p. 18

1-2-2 Actual Procedures of the Experiment  /p.18

1-2-3 Additional Experiment: Determination of Infinite Reflector Thickness  /p.22

1-3 Report   /p. 24

1-4Preparatory Report  /p.25

1-4-1 Numerical Simulation of the Critical Approach Experiment  /p.25

1-4-2 2-Group Diffusion Calculation of a Reflected Reactor   /p. 29

Appendix 1   /p.34

1A. Analytical Solution of the 2-Group Diffusion Equation  /p.34

1B. Solution for Core Region  /p.36

1C. Reflector Region  /p.39

1D. De termination of Critical Core Size  /p.41

1E. Neutron Flux Distribution  /p.44

Chapter 2 Control Rod Calibration

2-1 Purpose of Control Rod Calibration  /p.45

2-2 Principles  /p.47

2-2-1 Reactor Kinetic Equation  /p.47

2-2-2 Positive Period Method  /p.48

2-2-3 Control Rod Drop Metho  /p.50

2-2-4 Compensation Method  /p.53

2-3 Experiments  /p.54

2-3-1 Core Configurations   /p.54

2-3-2 Period Method Experiment  /p.56

2-3-3 Rod Drop Method Experiment  /p.56

2-4Discussions  /p.57

2-5 Preparatory Report  /p.58

Appendix 2 • • • ・5 9

2A. Neutron Lifetime  /p.59

2B. Delayed Neutron Data and Basic Parameters of KUCA  /p.60

2C. First Order Perturbation Theory  /p.61

2D. Control Rod Calibr~tion Curve  /p.64

Chapter 3 Measurement of Reaction Rate Dis出bution

3-1 Purpose  /p.65

3-2 Principle of Measurement by Activation Detector  /p.67

3-2-1 Features of a Neutron Activation Detector   /p.67

3-2-2 Principle of Measurement of Neutron Flux by Using an Activation Detector  /p.68

3-2-3 Principle of Measuring Radioactivity by Using Gold (Au) Activation Foil  /p.71

3-2-4 Determination of Detection Coefficient  /p.73

3-3 Determination of the Activation Reaction Rate by Thermal Neutron Flux  /p.75

3-3-1 Neutron Spectrums in the Reactor Core  /p.75

3-3-2 Activation Reaction Rate by Thermal Neutrons  /p.77

3-4 Experiments  /p.87

3-4-1 Core Configuration  /p.87

3-4-2 Equipment and Irradiation of Gold Wires and Foils with the Core  /p.87

3-4-3 Measurement of the Radiation of the Gold Wires and Foils  /p.89

3-5 Preparation of Experimental Data and Report  /p.94

3-6 Preparatory Report  /p.97

References  /p.100

Appendix 3  /p.101

3A. Absolute Measurement of the Activation Reaction Rate by the 4πβ-γ Coincidence Method  /p.1 01

3A-1 Principles of the 41rP-rCoincidence Method  /p.101

3A-2 Absolute Measurement by the  4πβ-γ Coincidence Method  /p.103

3B. Outline and Instruction of Measurement Equipment by an HPGe Detector  ・ 1 05

Chapter 4 Neutron Correlation Experiment Feynman-α Method

4-1 Purpose  /p.107

4-2 Variance-to-Mean Ratio in a Multiplication System   /p.108

4-2-1 Decay Constant α  /p.109

4-2-2 γValue Expressed by Reactivity  /p.110

4-2-3 Amount of γ value  /p.111

4-2-4 Asymptotic Behavior of γ  /p.111                      

4-2-5 γValue in a Critical System by Delayed Neutrons  /p.112

4-2-6 Relationship between Power and the Value  /p.113

4-3 Experiments  /p.114

4-3-1 Equipment Needed  /p.114

4-3-2 Experimental Methods  /p.116

4-3-3 Data Processing  /p.118

4-4 Reports and Discussions  /p.119

4-4-1 Reports  /p.119

4-4-2 Discussions  /p.120

References  /p.121

Appendix 4  /p.122

Derivation of Feynman-a Method Equations  /p.122

4A-1 Steady State  /p.126

4A-2 Consideration of Delayed Neutrons  /p.127

4A-3 Initial Correlation Correction, Spatial Dependence and Fission Counter  /p.128

Chapter 5 Measurement of Reactivity by the Pulsed Neutron Method

5-1 Purpose   /p.129

5-2 Principle of the Experiment  /p.130

5-3 Experimental Equipment   /p.137

5-4 Experimental Methods   /p.138

5-5 Data Processing   /p.139

5-6 Reports and Discussion  /p.140

References  /p.141