Influence of variation in converging section and orifice plane on the performance of venturi scrubber by using CFD

Abstract

Filtered Containment Venting System (FCVS) is an important severe accident mitigation system within a nuclear powerplant. Its main objectives are prevention of over-pressurization of containment and spread of radioactivity into environment in a severe accident scenario. After initiation of an accident, when pressure exceeds the design limit, a portion of containment air is transferred to this system. Incoming contaminated air containing hazardous gases like iodine gets scrubbed out in FCVS and clean air is vented into environment. Removal of iodine is crucial because if released to the environment, it can cause thyroid cancer. Venturi scrubbers play a very important role in removal of iodine. Study of its geometric and operational parameters is required to achieve high iodine removal efficiency. So, this study was conducted to investigate the influence of geometric parameters of venturi scrubber on removal efficiency of iodine by using Computational Fluid Dynamics. Geometric parameters such as length and diameter of converging section, position of orifice plane and orifice diameter were studied. Effect of above-mentioned geometric parameters, on various operational parameters such as pressure, velocity, mass transfer rate, volume fraction of air and mass fraction of iodine, was studied. Results showed that variation in converging section's length from 110 to 70 mm caused 9% increase in mass transfer rate of iodine. Variation of position of orifice plane from 3 to 15 mm caused 25% increase in mass transfer rate of iodine. 60% increase in mass transfer rate was achieved by change of orifice diameter from 1 to 1.8 mm. The order of influence of geometric parameters on removal efficiency of iodine from higher to lower comes out to be orifice diameter, position of orifice plane, length of converging section and converging diameter.