CFD modeling of indoor radon distribution in a laboratory with granite countertops.

Radon gas, a significant source of indoor radiation exposure, poses serious health risks, particularly lung cancer. This study employs Computational Fluid Dynamics (CFD) using the ANSYS Fluent software to model the behaviour and distribution of radon gas in a laboratory space equipped with granite countertops. A three-dimensional model of the laboratory, including its geometry, ventilation rates, and radon exhalation sources, was developed to simulate radon concentrations, particularly at breathing height. Radon exhalation rate from the granite and other surfaces in the room was measured experimentally. Numerical results, validated by experimental measurements, revealed a 30% increase in average radon concentration following the installation of granite countertops with an exhalation rate of 6.5 Bq m^-2 h^-1. The spatial distribution of radon, particularly near the countertops, indicated regions where radon accumulated at concentrations exceeding the action threshold of the US Environmental Protection Agency of 148 Bq/m³. Additionally, while natural ventilation effectively reduced overall radon levels, its efficiency was diminished near the countertops due to complex airflow patterns, leading to radon accumulation in breathing zones. This study demonstrates the ability of numerical methods to identify centers of radon gas accumulation by predicting airflow patterns and behaviours at various ventilation rates, emphasizing the need for effective ventilation strategies, such as localized exhaust systems, to reduce radon exposure in critical areas.