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Thermophysics and Aeromechanics

2021 year, number 6

Studying the hydrodynamics of a coolant behind the mixing intensifier grid of the PWR fuel assembly

S.M. Dmitriev, A.A. Dobrov, D.V. Doronkov, D.S. Doronkova, K.E. Ivanova, K.A. Obidina, A.N. Pronin, A.V. Ryazanov, D.N. Solntsev, A.E. Khrobostov, O.D. Yalymova
Nizhny Novgorod State Technical University named after R.E. Alekseev, Nizhny Novgorod, Russia
Keywords: nuclear reactor, core, fuel assembly, mixing intensifier grid, fuel element, guide channel, research area, characteristic cell, coolant hydrodynamics, coolant mixing, vortex flow


The article presents the results of studies of a coolant flow behind the mixing intensifier grids of TVS Kvadrat fuel assemblies of the PWR. The purpose of the work is to evaluate the efficiency of mixing the coolant behind the intensifier grids of various designs and to choose their optimal design. To achieve this goal, a number of experiments are carried out on the aerodynamic research stand with scale models of fuel rod bundle fragments of fuel assemblies with mixing intensifier grids, equipped with turbulizing deflectors of various profile shapes. The cells located near the guide channel and regular cells are selected as the research area. The choice of the research area is due not only to the need to obtain a hydrodynamic picture of the coolant flow in characteristic cells and the choice of the optimal shape of the deflector, but also due to the necessary assessment of the influence of transverse coolant flows from the area of the guide channel on the flow motion in adjacent cells. The coolant flow pattern is represented by vector fields of transverse velocities, cartograms of the distribution of transverse and axial velocities, as well as graphical dependences of the distribution of the flow velocity components. Analysis of the spatial distribution of transverse and axial flow velocities allows studying and detailing the flow pattern of the coolant. Evaluation of the efficiency of the coolant mixing behind the grids and determination of the optimal shape of the deflector profile are carried out on the basis of a comprehensive analysis of the hydrodynamic pattern of the coolant flow and the parameters of intracellular vortex formation and intercellular mixing. The experimental results can be used in the engineering justification of structural solutions for the design of active zones of PWR reactors with TVS-Kvadrat. The accumulated database of experimental data is used for verification of CFD programs (both foreign and domestic development), as well as programs for thermal-hydraulic cell-by-cell calculation of active zones.