Chapter 1 Fundamental aspects of nuclear reactor fuel elements

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Printed in the United States of America ERDA Technical Information Center, Oak Ridge, Tennessee April 1976
Preface
Most industrialized nations of the world have accorded high priority to development of nuclear reactors in an effort to stave off an energy crisis. One of the critical areas on which the economic viability of this type of electricity production hinges is the performance of the ceramic fuel and the metallic structural components of the core, which are subject to conditions of high temperature and radiation fields. Research on the behavior of materials under such conditions is relatively recent, and this book represents application of this research to the practical problem of predicting the performance and longevity of reactor fuel elements. The book is designed to function both as a text for first-year graduate courses in nuclear materials and as a reference for workers involved in the materials design and performance aspects of nuclear reactors for electric power production. It is based on lectures in graduate courses in the Department of Nuclear Engineering, University of California, Berkeley, University students in nuclear engineering come from a variety of undergraduate disciplines, but, by and large, their background in the fundamental physics and chemistry on which much of the applied work treated in the book is based is sketchy. For this reason the first 8 chapters are devoted to reviews of selected aspects of s t a tistical thermodynamics, crystallography y, chemical thermodynamics, and physical metallurgy. The remaining 13 chapters constitute the application of these principles to the problems encountered in nuclear fuel elements. Chapters 9 to 16 deal with the properties and irradiation behavior of oxide fuels. Chapters 17 to 20 treat similar problems in the cladding. Chapter 21 incorporates the analyses of materials behavior presented in the earlier chapters into calculations of the performance of the entire fuel element. The book is primarily concerned with the materials problems uncovered during the development of the liquidmetal fast breeder reactor (LMFBR). Because of the less stringent radiation and thermal conditions in which lightwater-reactor (LWR) fuel operates compared to the environment of an LMFBR fuel pin, the fast breeder reactor may be more severely materials- limited than is the water reactor. Except for aqueous corrosion, hydriding, and nonisotropic growth of zircaloy cladding, which are not treated in the book, the basic irradiation effects are common on both LWR and LMFBR fuel elements. Similarly, gas-cooled fast breeder reactors will inherit all the
Citation
TID-26711-P1
Fundamental Aspects of Nuclear Reactor Fuel Elements
Donald R. Olander
Department of Nuclear Engineering University of California, Berkeley
fuel elements.
Available as TID-26711-P1
for $16.25 (foreign, $18.75)
National l Information Service U. S. Department of Commerce Springfield, Virginia 22161
Prepared
for the Division Energy
of Reactor Research
Development and Development
and
Demonstration Administration
1976
Technical Energy
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Olander, Donald R. Fundamental aspects of nuclear reactor “TID-26711-P1” Includes bibliographies and index. 1. Nuclear fuel elements. 1. Title. TK9207.04 76-6485 621.48’ 335 ISBN 0-87079-031-5 (v.1)
iii
materials problem of the LMFBR save those arising from the use of liquid-sodium coolant. Advanced fuels, such as carbides and nitrides, for fast breeder reactors are not specifically discussed in the book. The phenomena responsible for the behavior of oxide fuels in a reactor environment are for the most part found in carbides and nitrides as well. The differences between oxide and advanced ceramic fuels are quantitative rather than qualitative, and some fuel performance analyses in the book are illustrated using (U,Pu)C instead of ( U,Pu)O2. The approach is analytic rather than descriptive. The aim is to make very clear the relation between a model of the performance of some feature of a fuel element and simple, basic physical principles with which the reader is familiar. This philosophy means that a number of standard, classical formulas that constitute the starting point for many fuel-element performance analyses are derived rather than simply presented. The book is intended to be as self-consistent and inclusive in this aspect as possible, and its length is in large part dictated by this approach. The ultimate purpose is to convey an understanding of the physical processes occurring in metals and ceramics which, when taken together, produce the complex irradiation behavior of a nuclear reactor fuel pin. No attempt has been made to provide a method for rational design of a fuel element. Such a recipe does not exist, and, even if it did, its technological lifetime would be very much shorter than that of the fundamental phenomena on which it is based. As an aid to students, problems are provided at the end of each chapter; solutions to these problems have been to Problems, published in a separate book, Solutions available as TID-26711-P2 from the National Technical Information Service, U. S. Department of Commerce, Springfield, Virginia 22161. An attempt was made to maintain a consistent set of symbols throughout the book. This in itself provides a thread of continuity between the many theories of fuel and cladding behavior which have appeared in the technical literature over the past decade. Metric units are used throughout. It is impossible to be an expert in a field as eclectic as nuclear materials. The disciplines of chemistry, nuclear and solid-state physics, metallurgy, ceramics, applied mechanics, and mathematical analysis are all involved in an accurate description of the fate of an irradiated fuel pin. I am consequently particularly grateful to colleagues who have reviewed sections of the book.