Studies of Thermohydraulic Processes to Substantiate the Safety Characteristics of Fast Reactors (Review)

The article presents the results of current problem-oriented studies of thermal-hydraulic processes to substantiate the characteristics and safety of sodium-cooled fast neutron reactors across a wide range of thermophysical problems, including hydrodynamics and heat exchange in channels and fuel assemblies (FA) of the core, including under conditions of fuel element assemblies’ deformation during the campaign, intravessel circulation and coolant stratification in the tank of a fast neutron reactor with an integral equipment layout in the nominal mode with forced convection and natural convection of the coolant in the emergency cooldown mode, in the intermediate heat exchanger, and in the large-modular steam generator. The data of experimental hydrodynamic studies of flow parts of reactor installations, heat exchangers, and reactors of nuclear power plants are presented. The article analyzes the patterns of hydrodynamic processes occurring in the flow sections of cylindrical collector systems in reactors and heat exchangers identified during experimental studies on an aerodynamic stand and a hydraulic flume. These patterns are registered as scientific discoveries as previously unknown patterns and phenomena related to the atomic, space, metallurgical, and chemical fields of science and technology. The results of the computational studies performed using the version of the channel-by-channel code implementing a two-fluid model of a two-phase flow of liquid metal in the approximation of equal pressures in the vapor and liquid phases reproduce the development of the flow regimes of a two-phase flow, the pulsations of the liquid metal flow obtained in experimental studies, and also demonstrate antiphase pulsations of the flow of a two-phase coolant in a system of parallel fuel assemblies and interchannel instability characterized by a significant increase in the amplitude of the pulsations of the coolant flow in parallel FA.