FEATURES OF THE FORMATION OF HYDRODYNAMIC LOADS ON THE FUEL RODS DEPENDING ON THE STRUCTURE OF THE COOLANT FLOW AT THE ENTRANCE TO THE FUEL ASSEMBLY WWER

Experimental studies of hydrodynamic induced of fuel rods vibrations WWER-440 tweers using a full-scale mock-up with lead imitators of fuel tablets have been carried out. It is shown that the speed of the turbulent flow in the fuel rods beam cannot be the only hydrodynamic characteristic that determines the vibrational characteristics of the fuel rods beams. The presence of indignant flow of various elements of the tract of the coolant to the fuel rods beams inlet significantly affects the intensity of their vibrations. An energy model of the balance of pulsating energy of turbulent flow and expendable mechanical energy to the fuel rods beams has been developed. On the basis of the proposed model, a functional connection of the intensity of the vibrations of the fuel rods beams with the levels of pressure pulsations in the turbulent flow of the coolant at the entrance to the fuel rods beams is established. The modelling of Fuel Assembly (FA) as a mechanical vibrational system has received considerable attention. At the same time, the end-element methods, as the most universal for the sampling of spatial continual systems, have become widespread. However, the analysis of hydrodynamically excited vibrations is impossible without describing the processes of interaction of the flow with the streamlined surfaces of the mechanical vibration system. In most cases, such information can be obtained only through experimental research.