Tutorial on courses "Nuclear Physics," "Radiochemistry" and "Nuclear Industry." The book contains systematic information on radioactivity, radionuclides and accompanying radiation, the kinetics of decay and accumulation of radioactive isotopes, the structure of the nucleus and nuclear processes, sources of radioactive radiation, methods for detecting radioactive radiation, the interaction of radiation with matter, methods for separating isotopes, as well as methods for statistical processing of the results of radiometric measurements.