A study of the coolant flow at the inlet to the fuel assembly of the RITM nuclear icebreaker reactor

The article presents the results of an experimental study connected with the features of a coolant flow at the inlet to the fuel assembly (FA) in the cartridge core of a RITM nuclear icebreaker reactor. The study is focused at the non-uniformity of the axial flow velocity at the FA inlet. To this end, a series of experiments was carried out using a scale model including structural elements of the inlet section between the orifice plate and the unit attaching fuel rods to the diffuser, as well as the section of the fuel rod bundle up to the second spacer grid. In addition, the propagation of a non-uniform axial flow along the length of the fuel rod bundle was assessed during the experiments. The studies were carried out using the pneumometric method in characteristic cross-sections along the length of the model. Features of the coolant flow are visualized by cartograms of the axial velocity for the working medium flow. The results of experiments were used for hydraulic profiling of the FA inlet section. The obtained experimental database can be used to validate the LOGOS CFD software and clarify the methods for thermal-hydraulic calculations of cores in a cell approximation.