An Introduction to the Engineering of Fast Nuclear Reactors This book is a resource for both graduate-level engineering students and practicing nuclear engineers who want to expand their knowledge of fast nuclear reactors, the reactors of the future. The book is a concise yet comprehensive introduction to all aspects of fast reactor engineering. It covers topics including neutron physics, neutron flux spectra, Doppler and coolant temperature coefficients, the performance of ceramic and metal fuels under irradiation, the effects of irradiation and corrosion on structural materials, heat transfer in the reactor core and its effect on core design, coolants including sodium and lead-bismuth alloy, coolant circuits, pumps, heat exchangers and steam generators, and plant control. The final chapter covers all aspects of safety including operational safety and hypothetical accidents. The book includes discussions of gas coolants, the use of reactors to consume radioactive waste, and accelerator-driven subcritical systems. has more than 40 years experience in nuclear engineering, including managing the operation of a fast reactor power station and a period as Chief Technologist for Fast Reactors during which he was responsible for the entire UK national fast reactor R&D program. He spent periods at the Argonne National Laboratory (United States) and at the University of Cambridge Engineering Department. In addition to his research publications and presentations, he is the author of Fast Breeder Reactors: An Engineering Introduction.
AN INTRODUCTION TO THE ENGINEERING OF FAST NUCLEAR REACTORS
32 Avenue of the Americas, New York, NY 10013-2473, USA Cambridge University Press is part of the University of Cambridge. It furthers the University s mission by disseminating knowledge in the pursuit of education, learning, and research at the highest international levels of excellence. Information on this title: /9781107034648 C 2014 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 2014 Printed in the United States of America A catalog record for this publication is available from the British Library. Library of Congress Cataloging in Publication data Judd, A. M. An introduction to the engineering of fast nuclear reactors /. pages cm. A revision and extension of Fast breeder reactors : an engineering introduction, published in 1981 Preface. Includes bibliographical references and index. ISBN 978-1-107-03464-8 (hardback) 1. Fast reactors. 2. Breeder reactors. 3. Nuclear engineering. I. Judd, A. M. Fast breeder reactors. II. Title. TK9203.F3J84 2014 621.48 34 dc23 2013030947 ISBN 978-1-107-03464-8 Hardback Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party Internet Web sites referred to in this publication and does not guarantee that any content on such Web sites is, or will remain, accurate or appropriate.
CONTENTS Preface xi Introduction...1 What Fast Reactors Can Do 1 Chain Reactions 1 Breeding and Consumption 2 Energy Resources 6 How Fast Reactors Have Been Developed 8 The Early Years 8 The Era of Metal Fuel 10 The Importance of Burnup 11 Oxide Fuel and Sodium Coolant 13 The Period of Decline 14 The 21st Century 15 General References 16 1 Physics...18 1.1 Introduction 18 1.1.1 Physics and Design 18 1.1.2 Comparison with Thermal Reactors 19 1.1.3 Typical Reactors 20 1.2 Calculation Methods 21 1.2.1 The Transport Equation 21 1.2.2 Discretisation 23 1.2.3 The Diffusion Approximation 24 1.2.4 Multigroup Diffusion Theory 26 1.2.5 Fundamental Mode Calculations 28 1.2.6 Perturbation Theory 30 1.2.7 Matrix Notation 32 v
vi Contents 1.2.8 Resonances the Effect of Temperature 34 1.2.9 Resonances Effective Cross Sections 36 1.2.10 Computation Transport and Diffusion Theory 39 1.2.11 Computation the Monte Carlo Method 41 1.2.12 Accuracy and Experimental Checks 45 1.3 Neutron Flux 47 1.3.1 Energy Spectra 47 1.3.2 Power Distribution and Enrichment Zones 56 1.4 Higher Actinides 58 1.4.1 Formation of Higher Actinides 58 1.4.2 Breeding 60 1.4.3 Internal Breeding 63 1.4.4 Fuel Composition 64 1.5 Control Rods 69 1.5.1 Materials 69 1.5.2 Reactivity Worth 69 1.5.3 Reactivity Requirements 72 1.6 Reactivity Coefficients 73 1.6.1 Effects of Temperature 73 1.6.2 Structure Temperatures 74 1.6.3 Bowing 76 1.6.4 Coolant Density 76 1.6.5 Doppler Coefficient 79 1.6.6 Power and Temperature Coefficients 81 1.6.7 Dependence of Doppler and Sodium Coefficients on Design Breeders 81 1.6.8 Dependence of Doppler and Sodium Coefficients on Design Consumers 84 1.7 Subcritical Reactors 85 1.7.1 Neutron Economy 85 1.7.2 Gain 87 1.7.3 Changes in Reactivity 88 1.7.4 Power Density 89 References for Chapter 1 90 2 Fuel...92 2.1 Introduction 92 2.2 Oxide Fuel Temperatures 93 2.2.1 Temperature Distribution 93 2.2.2 Thermal Conductivity 94 2.2.3 Conductance between Fuel and Cladding 97
Contents vii 2.3 Design and Manufacture of Oxide Fuel 99 2.3.1 Porosity, Swelling and Smear Density 99 2.3.2 Manufacturing Processes 101 2.3.3 Reprocessing 102 2.3.4 Stoichiometry and Oxygen Potential 104 2.3.5 Fission-Product Gas Release 107 2.3.6 Sealed or Vented Fuel 110 2.3.7 Fuel Element Design 111 2.4 Irradiation Behaviour of Oxide Fuel 112 2.4.1 Recrystallisation 112 2.4.2 Cracking 115 2.4.3 Thermal and Irradiation Creep 116 2.4.4 Interaction between Fuel and Cladding 119 2.4.5 Migration of Plutonium and Oxygen 120 2.4.6 Fission-Product Behaviour 122 2.4.7 Corrosion of the Cladding 125 2.5 Metal Fuel 126 2.5.1 Temperatures 126 2.5.2 Swelling 128 2.5.3 Mechanical Behaviour during Irradiation 131 2.5.4 Redistribution of Alloy Components 133 2.5.5 Corrosion of the Cladding 134 2.5.6 Reprocessing and Fabrication 135 2.6 Other Fuel Materials 137 2.6.1 Carbide 137 2.6.2 Nitride 140 2.7 Fuel for Consumer Reactors 141 2.7.1 Consumption of Plutonium 141 2.7.2 Consumption of Higher Actinides Ceramic Fuel 143 2.7.3 Preferred Ceramic Fuel Materials for a Consumer of Higher Actinides 145 2.7.4 Consumption of Higher Actinides Metal Fuel 147 References for Chapter 2 148 3 ReactorCore...150 3.1 Introduction 150 3.2 Heat Transfer and Transport 151 3.2.1 Fuel Element Rating 151 3.2.2 Distribution of Power Density 152 3.2.3 Heat Transport from the Core 153
viii Contents 3.2.4 Heat Transfer to the Coolant 157 3.2.5 Coolant and Cladding Temperatures 160 3.3 Structural Materials 164 3.3.1 Displacement of Atoms 164 3.3.2 Irradiation Swelling 167 3.3.3 Irradiation Creep, Embrittlement and Hardening 171 3.3.4 Corrosion in Sodium 173 3.3.5 Corrosion in Lead and Lead-Bismuth Eutectic 176 3.3.6 Choice of Structural Materials 178 3.4 Core Structure 180 3.4.1 Fuel Subassemblies 180 3.4.2 Subassembly Bowing and Restraint 182 3.4.3 Diagrid 186 3.4.4 Configuration of the Reactor Core 188 References for Chapter 3 190 4 CoolantCircuitsandSteamPlant...192 4.1 Introduction 192 4.1.1 Choice of Coolant 192 4.1.2 Sodium Coolant 195 4.2 Primary Sodium Circuit 197 4.2.1 Pool or Loop Layout 197 4.2.2 Pumps 202 4.2.3 Intermediate Heat Exchangers 205 4.2.4 Thermal Shock 206 4.2.5 High-Cycle Fatigue ( Thermal Striping ) 208 4.2.6 Crack Initiation and Growth 210 4.2.7 Control of Impurities 212 4.2.8 Monitoring of Impurities 214 4.2.9 Refuelling 215 4.3 Steam Plant 218 4.3.1 Steam Generator Design 218 4.3.2 Steam Generator Tube Welds 221 4.3.3 Steam Generator Heat Transfer 224 4.3.4 Plant Efficiency 227 4.3.5 Available Energy 229 4.4 Control Systems 232 4.4.1 Normal Operation 232 4.4.2 Abnormal Conditions 235 References for Chapter 4 237
Contents ix 5 Safety...239 5.1 Introduction 239 5.1.1 Safety and Design 239 5.1.2 Comparison with Thermal Reactors 240 5.1.3 Low-Pressure Coolants 242 5.2 Reactor Protective Systems 244 5.2.1 Automatic Shutdown 244 5.2.2 Whole-Core Instrumentation 245 5.2.3 Subassembly Instrumentation 248 5.2.4 Decay-Heat Removal 251 5.2.5 Containment 253 5.3 Operational Safety 256 5.3.1 Operator Dose 256 5.3.2 Sodium Fires 256 5.3.3 Sodium-Water Reactions 257 5.4 Hypothetical Accidents 263 5.4.1 Accident Sequences 263 5.4.2 Subassembly Accidents 265 5.4.3 Whole-Core Accidents 268 5.4.4 Core-Disruptive Accidents the Initiation Phase 271 5.4.5 Core-Disruptive Accidents the Transition Phase 275 5.4.6 Core-Disruptive Accidents Passive Protection 278 5.4.7 Post-Accident Cooling 280 References for Chapter 5 281 Index 285
PREFACE This book is a revision and extension of Fast Breeder Reactors: An Engineering Introduction, published in 1981. I have rewritten much of it in the light of developments in fast reactor technology that have taken place in the subsequent three decades, and to take account of the new applications for fast reactors that have been suggested. It is intended for the newcomer to the study of fast reactors, either as a student or at a later stage of his or her career. It will probably be most useful to someone who already has some knowledge of nuclear reactors. There are many excellent introductory texts for the beginner in nuclear engineering but they all concentrate on thermal reactors. The purpose of this book is to provide an up-to-date account of fast reactors for those who want to take the next step. Fast reactor technology has become a wide field, so wide that it is not possible to cover all of it in depth in a single book of reasonable length. What I have attempted is to cover the whole in sufficient detail to allow the reader to understand the important features, and to provide suitable references for further study. I have gone into detail on the neutron physics because any fast reactor engineer, whether he or she is a designer, an operator or a researcher, needs to understand how the machinery works at a basic level. I have also attempted to include the results of experience, often hard-won, of operating a fast reactor power station. xi
xii Preface I have divided the subject matter up in chapters according to discipline. Chapter 1 about the physics of fast reactors is the most detailed and mathematical. This is to give those who have to use the numbers produced by the complex computer codes that predict reactor performance some idea of where they come from. Chapter 2 is mainly about the chemistry of fast reactor fuel. Chapters 3 and 4 are about the application of mainly conventional engineering disciplines to fast reactors so they contain less theoretical detail. In Chapter 5 I have tried to show how safety can be attained by careful attention to detail in design. The Introduction includes an explanation of the difference between fast reactors and thermal reactors and a brief summary of the history of fast reactor development. I wish to thank Argonne National Laboratory for permission to reproduce Figures 2.19, 2.22 and 2.25. Many of my colleagues in the atomic energy industry have been very generous in helping me to write this book and its predecessor. They are for too numerous to mention by name. By way of thanks I wish to dedicate this account of the technology to the hundreds of engineers, scientists and technicians whose achievements made possible the success of the British Fast Reactor project, started in 1946 and abandoned prematurely in 1993.