REGULARITIES OF FORMATION OF FLOW OF COOLANT BEHIND THE TVS-KVADRAT MIXING SPACING GRID OF THE PWR-TYPE REACTOR

Tgratinghis paper presents the results of experimental investigations of the influence of mixing spacer gratings with different types of deflectors on the coolant flow in the TVSKvadrat fuel assembly of the PWR-type reactor. Experimental model of the TVS-Kvadrat of the PWR reactor was made in complete geometric similarity with the full-scale cassettes. Studies were carried out by modeling the flow of coolant in the core with the use of an experimental stand; the latter was an aerodynamic open loop through which air is pumped. To measure the local hydrodynamic characteristics of the coolant flow, special pneumatic sensors were used that were able to measure the full velocity vector at the point by its three components. During the studies of the local fluid dynamics of the coolant, the transverse flow rates were measured; also, the coolant flow rates were measured by cells of the TVS-Kvadrat experimental model. The analysis of the spatial distribution of the projections of the absolute flow velocity made it possible to detail the pattern of the coolant flow behind the mixing spacing gratings with different variants of the deflector design, as well as to choose the deflector of the optimal design. Accumulated data base on the flow of the coolant in the TVS-Kvadrat fuel assembly formed the basis of the engineering justification of the structures of the active zones of PWR reactors. Guidelines for choosing optimal designs mixing spacing grids have been considered by designers of the “Afrikantov OKBM” JSC when they created implementations of the latest TVS-Kvadrat assemblies. The results of experimental studies are used to verify CFD-codes of both foreign and domestic origin, as well as the programs for detailed cell-by-cell calculation of active zones in order to reduce conservatism in the justification of thermal reliability.

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