Computational and Experimental Investigation of Patterns of Coolant Flow in the Mixed Core of a VVER Reactor

The paper presents the results of investigations into the hydrodynamics of a three-dimensional coolant flow motion in the mixed core of a VVER (a.k.a. WWER or PWR) reactor. The experiments were conducted on an aerodynamic research facility test bench with scaled models of core fragments. An investigation has been made into the patterns of the coolant flow motion by experimental finding of the velocity vector. Measurement of the flow pressure field was conducted with a five-channel pneumometric (pressure-tube) probe and was then recalculated and converted into the direction and value of the velocity. To obtain a detailed pattern of a three-dimensional coolant flow motion, the most representative region of the models′ cross section including the space between the fuel (fuel rod bundles) and four rows of fuel elements of each of the adjacent fuel assemblies was identified and investigated. The general pattern of the coolant flow is represented by plots of transverse velocity distribution as a function of a relative coordinate and by cartograms of axial velocity distribution. An analysis of the spatial distribution of the flow velocity projections in characteristic regions of the model made it possible to identify the patterns of the coolant flow around hydraulically nonidentical intensifier grids.