Types and main features of NPPs. Realization of the heat transport technology in different reactor types. The heat production process and its spatial distribution in light-water nuclear reactors. The relationship between the thermal neutron flux distribution and the heat production. Power distribution within the reactor core. Residual heat generation. The general heat conduction differential equation and its solution for the fuel - cladding system. Single-phase hydraulics: the momentum conservation equation for one-dimensional flow; calculations of the friction loss, hydraulic resistance of sudden changes; modelling the velocity distribution and the transport processes in the reactor, mixing, critical flow. Two-phase hydraulics: flow patterns, volume steam content, two-phase flow modelling, pressure drop in two-phase flow, mixing, critical flow. Single-phase heat transfer calculations, natural and forced convection. Two-phase heat transfer calculations. Boiling curve, boiling crisis, critical heat flux, DNBR. Thermal-hydraulics calculation of the pressurized water reactor: conservation equations; temperature distribution in the fuel rod; calculation of the characteristics of the coolant; design limits, hot channel factors. The thermal-hydraulics of design basis accidents. Thermo-physical problems of the re-flooding of the reactor core. Overview of computer programs used in thermal-hydraulics calculations. Subchannel codes and their applications. System codes and their validation. Nuclear safety principles. Design basis. Understanding and applying the thermal-hydraulics system codes for the analysis of incidents. Overview of the most important processes leading to core meltdown in beyond design basis severe accidents and their calculations.