Radon diffusion studies through some building materials: Effect of grain size

Radon appears mainly by diffusion processes from the point of origin following αα-decay of 226Ra in underground soil and building materials used, in the construction of floors, walls, and ceilings. The diffusion of radon in dwellings is a process determined by the radon concentration gradient across the building material structure between the radon source and the surrounding air, and can be a significant contributor to indoor radon inflow. In the present study radon diffusion through some building materials, viz., soil, sand, fly ash, cement, etc. has been carried out using LR-115 type II solid-state nuclear track detectors (SSNTDs). The radon diffusion coefficients and diffusion lengths through these building construction materials have been calculated. As the rate of radon inflow is dependent upon the porosity and grain size of the materials also, therefore, the effects of grain size on radon diffusion through some of these materials have also been studied. For these studies the materials with different grain sizes, viz. 50, 100, 200μm were used. The results indicate that the radon diffusion through these materials decreases with decrease in grain size.