Nuclear reactor physics is concerned with the study of chain reactions in nuclear reactors and their application for producing energy in a controlled fission reaction. The initiation and control of a self-sustained nuclear chain reaction occurs in a nuclear reactor. The key components in a nuclear power plant can be grouped under the classes of reactor assembly, steam generation, power generation, fuel handling, safety systems and controls. The reactor assembly consists of nuclear fuel, moderator, neutron source, reactor core, coolant and control rods, besides others. Boiler feedwater pump and steam generators are the components in steam generation. Nuclear reactors are classified according to the type of nuclear reactions they undergo, the moderator and coolants used, etc. Nuclear reactors are used for electricity generation and for the propulsion of ships. Heat generated due to nuclear fission is transferred to water or gas, which then drives steam turbines for varied applications. This book outlines the processes and applications of nuclear reactors in detail. While understanding the long-term perspectives of the topics, the book makes an effort in highlighting their impact as a modern tool for the growth of nuclear reactor physics. This book is meant for students who are looking for an elaborate reference text on nuclear reactor physics.