Investigations of Characteristic Properties of the Coolant Flow at the Inlet to a Cassette Fuel Assembly of a RITM-200 Reactor of a Low-Power Nuclear Plant

Results of investigations into the coolant flow at the cassette fuel assembly (FA) inlet of the RITM-200 reactor at a small nuclear power plant are presented. The goal of the investigation is an experimental determination of the effects of the elements of the FA inlet portion design on the coolant hydrodynamics in the active segment of the fuel element cluster and the development of recommendations on optimizing the design of certain elements of the FA inlet portion. To achieve this, experiments were carried out on a scaled model simulating the geometry of the FA inlet flow path from the choke flange to the second spacer grid in the fuel element cluster. The experiments were conducted using the pneumometric method. The flow velocity was measured through the entire cross section of the experimental model. The characteristic properties of the coolant flow were visualized with axial velocity cartograms (collation maps) in cross sections of the experimental model. The experimental data have been used in hydraulic profiling of the FA inlet portion and also in substantiating the thermotechnical reliability of new cassette cores. An experimental database has been used in validation of the LOGOS CFD-program and also for clarification of thermohydraulic core design procedures.