Mathematical analysis and modelling of reducing radon radiation activity in the building

Analytical dependencies for determining the concentration of Radon 222 (222Rn) in the air of premises for various purposes where gas leaks through leaks or cracks in the building envelope (bomb shelters, basements, semi-basement non-residential and residential premises of the first to third floors of buildings and structures) were obtained. Based on the obtained formulas, it became possible to calculate the change in gas concentration in the investigated space. The developed mathematical model, which uses ANSYS CFD (Computational Fluid Dynamics) simulation, confirmed the results of the calculation according to the analytical dependencies. Based on the continuity equations and the Reynolds-Averaged Navier-Stokes equations (RANS), the results of changes in the state of the air environment in a ventilated space were obtained: - graph of changes in 222Rn concentration in the initially contaminated room (500 Bq/m3) to the standard value over time when inert gas is supplied to the room and the general exchange ventilation system is in operation; - concentration by Mass Fraction for 222Rn in time upon reaching the value permitted by the regulatory documents of Ukraine; - 222Rn current lines (Velocity Stream Line). The engineering formulas for calculating the reduction of 222Rn concentration during the operation of the general exchange ventilation system were obtained. The recommended scheme of air exchange in rooms with 222Rn inflow through leaks or cracks in the floor is "supply air from above - exhaust air from below".