Thermohydrodynamic investigations of the grid spacers of nuclear reactor rod fuel assemblies

The studies on the velocity fields on the fuel assembly aerodynamic model were carried out with an account of the fact, that the grid spacers effect the redistribution of thermohydraulic parameters by the assembly cross section. It made it possible to determine the mechanisms of the grids impact on mixing, which may lead to leveling the nonuniformity of the thermohydraulic parameters distribution, which is typical for rod fuel assemblies, and thereby to the critical heat flux growth. The study results made it possible to determine the causes of the grid spacers effect on the heat transfer crisis and identify the most effective types of grids, which may be considered as the heat exchange intensifiers, leading to significant expansion of the area of the fuel assembly noncritical operation