Features of forming a coolant flow in the inlet section of the fuel cartridge for a RITM small nuclear power plant

The paper presents the results of an experimental study on coolant flow patterns at the inlet section of a fuel assembly (FA) in the cartridge core of a reactor for a RITM small nuclear power plant. The objective was a study on influence of different inlet elements on the coolant axial velocity distribution. This task was performed by a series of experiments on a scale-up experimental model covering the inlet section components from the calibration washer up to the attachment unit between fuel rods and the diffuser. The model also covers the section of the fuel-element bundle between the absorbing grid and the spacer grid. This study is based on the pneumometric method for several critical cross sections over the model length. The allocation of measuring points covers the entire cross section of the model. The coolant flow features are visualized using digital maps for the working medium flow axial velocity in the fuel rod bundle cross section. The experimental modeling can be useful for optimizing the hydraulic profiling of the components at the inlet of the fuel rod assembly. The set of test data can be applied for validation of the LOGOS CFD software and for adjusting the technique of heat and fluid computations for the core zones under a cell approximation.