Radon-222 Accumulation in Air Confined by Phosphogypsum-Bearing Boundaries: Simulation for Distinct Exhaling Scenarios

Abstract:- Understanding radon-222 exhalation from phosphogypsum-bearing materials and its accumulation in confined air is fundamental for radiation exposure assessment and radiological protection design based on human health risks. Despite evoking time dependence, zero-order models with respect to space assume uniform distribution of radon-222 activity. If detailed description is desired, one must consider spatial dependence as well. Accordingly, this work proposes a time-varying two-dimensional diffusion-dominant model where radon-222 self-decay is accounted as a sink term in the governing differential equation while its exhalation from boundaries is modelled as Neumann-type boundary condition. By adapting an existing academic simulator for transport phenomena, distinct exhaling scenarios are numerically simulated and discussed bearing in mind the failure of the aforesaid homogeneous distribution hypothesis as well as future extensions of the simulator