This comprehensive volume offers readers a progressive and highly detailed introduction to the complex behavior of neutrons in general, and in the context of nuclear power generation. A compendium and handbook for nuclear engineers, a source of teaching material for academic lecturers as well as a graduate text for advanced students and other non-experts wishing to enter this field, it is based on the author's teaching and research experience and his recognized expertise in nuclear safety. After recapping a number of points in nuclear physics, placing the theoretical notions in their historical context, the book successively reveals the latest quantitative theories concerning: * The slowing-down of neutrons in matter * The charged particles and electromagnetic rays * The calculation scheme, especially the simplification hypothesis * The concept of criticality based on chain reactions * The theory of homogeneous and heterogeneous reactors * The problem of self-shielding * The theory of the nuclear reflector, a subject largely ignored subject in literature * The computational methods in transport and diffusion theories Complemented by more than 400 bibliographical references, some of which are commented and annotated, and augmented by an appendix on the history of reactor physics at EDF (Electricite De France), this book is the most comprehensive and up-to-date introduction to and reference resource in neutronics and reactor theory.