Studying coolant hydrodynamics in the area of a guide channel of fuel assembly with intensifier grids

The article presents the results of studies of the coolant flow in fuel assemblies behind the intensifier grids of FA-Square reactors of the PWR type. The aim of this work is to evaluate the effectiveness of using various designs of the intensifier grid for the flow mixing. To achieve this goal, a number of experimental studies are carried out on an aerodynamic stand with scale models of fragments of fuel assemblies with intensifier grids of various designs. Adjacent cells of the guide channel, the design feature of which is the different spatial orientation of turbulators installed on the intensifier grids, are selected as a representative area of research. The general flow pattern is represented by vector fields of tangential velocities, as well as by graphical dependences of the distribution of transverse velocities in the gaps between the rods of the research area. To evaluate the efficiency of using various intensifier grids' designs for the coolant flow mixing, the parameters of intracellular vortex formation and intercellular mixing are analyzed. Analysis of the spatial distribution of tangential flow velocities allows studying and detailing the coolant flow pattern behind the mixing grids with various designs of deflectors. The accumulated database on the coolant flow in the FAKVADRAT is the basis for engineering justification of the PWR reactor core designs. The results of experimental studies are used to verify CFD codes of both foreign and domestic development, as well as the programs for detailed cell-based calculation of active zones in order to reduce conservatism in justifying thermal reliability.