Radium, which is naturally present in many rocks, decays to the radioactive gas radon, which is exhaled from the surface of underground tunnels and air-raid shelters and is a major source of human exposure to radioactivity. We developed a mathematical model for the migration of radon from a finite-thickness circular tubular emanation medium and a semi-infinite hollow cylindrical emanation medium based on the seepage–diffusion migration theory of radon in porous emanation media. We obtained an analytical solution for the distribution of radon c...
