Abstract

The Volume Control Tank (VCT) is an indispensable device ofChemical and Volume Control System in the primary loop. The incoming water cannot be quickly mixed with the original boric acid solution in the VCT during the dilution process. The poor mixing would delay the reactive control of the core, which increases the time consumption of nuclear power plant operations and brings adverse impacts on core stability. A numerical investigation of the mixing in the VCT during the dilution process is carried out. The numerical methods were validated by experimental data. It is found that there are two different mixing modes in the tank, and the mixing and flow characteristics under different mixing modes are analyzed. It is found that the concentration stratification increases the flow resistance, which has a negative impact on the mixing. Increasing the inlet velocity can effectively avoid stratification and improve mixing efficiency. Increasing the jet density difference will aggravate the stratification in the tank, and even cause the phenomenon of double stratification. The work in this paper has certain guidance for understanding the internal fields in the VCT during the dilution process and improving the mixing efficiency in the VCT.

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