This book highlights a comprehensive and detailed introduction to the fundamental principles related to nuclear engineering. As one of the most popular choices of future energy, nuclear energy is of increasing demand globally. Due to the complexity of nuclear engineering, its research and development as well as safe operation of its facility requires a wide scope of knowledge, ranging from basic disciplines such as mathematics, physics, chemistry, and thermodynamics to applied subjects such as reactor theory and radiation protection. The book covers all necessary knowledge in an illustrative and readable style, with a sufficient amount of examples and exercises. It is an easy-to-read textbook for graduate students in nuclear engineering and a valuable handbook for nuclear facility operators, maintenance personnel and technical staff.