Factors affecting the spread of radioactive aerosols into indoors: deposition on the inner walls of small containers, a new model

Abstract

Deposition of aerosols on the inner walls of small-size containers is studied using a theoretical approach based on the equation of first Fick's law of diffusion. For calculating the deposition velocities, both turbulent and brownian diffusions are considered in describing the aerosol motions in the boundary layer. The aerosol eddy diffusivity near the surface is described by a fourth power dependence on the distance. The formula has a single describing parameter, where the model assumes the boundary layer to be formed of a single layer, rather than multi sublayers. The describing parameter is determined based on the friction velocity. Assuming spherical, aerosols with diameters between 1 nm–100 µm are studied, which covers all known types of aerosols. The results are compared to other theoretical calculations. The model is successful for describing the experimental data and gives a better understanding of the turbulence behavior inside small containers. Moreover, it redefines the structure and thickness of the boundary layer. Among other important applications, the new model suggests that the calculations of the indoor radioactive aerosol concentrations and inhalation doses should be refined by considering modified estimations of the radioactive aerosols deposition rates inside any small openings in the walls of the buildings.