The presented issue is based on the materials of lectures on course “Physics and Dynamics of Nuclear Reactors” that the author has been delivering for many years at the Institute for Nuclear Power Engineering (Obninsk) to Russian NPP engineers arriving for advanced training and professional development. With account that not all readers possess the special knowledge in areas of nuclear physics and physical theory of nuclear reactors, the following issues are described in the book, namely fundamentals in nuclear power, current problems in nuclear power and solving methods, fundamentals in nuclear reactor physics and technology; the processes developing in the operating reactor and important for safety are characterized; the reasons of certain accidents and possible ways for their elimination are examined. The presented issue is oriented on senior pupils, students specializing in different areas of nuclear power, teachers of physics, operating NPP engineers, researchers in design and construction of nuclear reactors and all people interested in the problems of nuclear power.