Thermal-Hydraulic Principles and Safety Analysis Guidelines of PWRs and SMRs presents key phenomena, models, advantages, and drawbacks of current methods. The book guides the reader through the preparation and review of the thermal-hydraulic part of a safety analysis report and equips them with the knowledge to perform thermal-hydraulic studies with confidence. Starting with an introduction to thermal-hydraulics and two-phase flows, the book covers key models such as the Homogeneous Equilibrium Model and Drift Flux, Main Phenomena and associated models, including critical flow, heat transfer and void fraction, and then moves onto cover nuclear safety analyses and code. It contains fundamental tools to help readers understand complicated phenomena that can happen in various accidental conditions, along with key principles to help readers when using advanced simulation tools. This book is suitable for a broad audience, including non-specialized readers seeking independent advice and technicians or engineers working in nuclear facilities. It will provide students in engineering disciplines with a solid understanding of the thermal-hydraulics of nuclear reactors and safety, which will enable them to work safely and efficiently and drive research forward. Presents key phenomena and basic models without complex equations Focuses on DNB and LOCA thermal-hydraulic safety analyses Includes simple applications and tools for the evaluation of order of magnitude