CFD simulations to study the effect of ventilation rate on 220Rn concentration distribution in a test house

Abstract

Measurement and interpretation of the distribution patterns of indoor 220Rn concentration is important for inhalation dosimetry in occupational and residential areas. The shorter half-life of radioactive 220Rn gas greatly affects its patterns resulting in non-homogeneity in the spatial concentration profile. In addition, the distribution profile also changes with variations in the ambient atmospheric parameters (ventilation rate, humidity etc.). The Computational fluid dynamics (CFD) technique has gained a lot of attention in recent times for the prediction and visualization of the distribution pattern of indoor 222Rn/220Rn concentration. This study aims to apply the CFD technique for studying the effect of variations in the ventilation rate on the distribution pattern of the 220Rn concentration in a thoron test house. Experimentally measured 220Rn flux from the surfaces of the experimental test house is used as input for the CFD simulations. Ventilation rate is varied from 0.1 h−1 to 9.0 h−1 and the simulated results of velocity and 220Rn concentration profile for the entire test domain are interpreted. It is observed that the increase of ventilation rate leads to the flow induced turbulence enhancing the mixing of 220Rn in indoor air. Results of this study demonstrate the inter-play of radionuclide half-life and turbulent mixing induced transportation. Inferences are discussed in order to improve the dosimetric deductions for indoor conditions.