CFD analysis of iodine mass transfer coupled with a chemical reaction in a filtered containment venting system

The removal of iodine from flue gases through FCVS during a core meltdown in nuclear reactors is important for environmental safety. In this study, CFD analysis for iodine removal in a venturi scrubber was done on Ansys Fluent using a mathematical model that coupled the mass transfer of iodine with the reaction between iodine and thiosulfate. A user defined function (UDF) was written to couple the mass transfer with the reaction. The UDF was hooked into Ansys Fluent, and the simulation was run for three different gas flow rates. Contours for the mass fraction of iodine, tetrathionate, and iodide, along with the hydrodynamics of the venturi scrubber, were analyzed at different gas flow rates. The mass transfer rate of iodine and its overall removal efficiency were observed to increase at higher gas velocities. The results satisfied the experimental data at a high gas flow rate of 340 m³/h but overpredicted the efficiency at lower flow rates of 240 m³/h and 290 m³/h.