Theoretical study of the radon emanation coefficient for granular material: influence of packing and water

Experimentally, it has been observed that the radon emanation coefficient, determined for geologicaland construction materials, depends principally on the porosity and water content. This paperconcerns a theoretical study of radon emanation by using these parameters and additionally byincluding the grain size of the material and the packing of the grains as well as the radium distribution.The radon emanation coefficient was calculated from a 3D Monte Carlo-type simulation of thetrapping rate of the radon atom in the grain and the embedding rate in a neighbouring grain by thedirect recoil effect (mono-sized spherical grain packing). This study highlights the large influence ofwater and the influence of the radium localization in the grain.