A Laboratory Method for Concurrently Determining Diffusion Migration Parameters and Water Saturation Effects of Thoron in Uranium Tailings

Environmental humidity has a significanteffect on changes in free (220)Rn (thoron) production rate and effective diffusion coefficient of (220)Rn in uranium tailings. To understand such changes, a closed cavity containing porous (220)Rn media with finite thickness was studied. Based on the (220)Rn diffusion migration theory in porous media with finite thickness, a model for calculating the uniform (220)Rn activity concentration in a closed container with porous media of finite thickness was established. A laboratory method for concurrently determining free (220)Rn production rate and effective diffusion coefficient of (220)Rn was proposed and a corresponding experimental setup was made. With samples taken from a uranium tailing impoundment in southern China, water content, free (220)Rn production rate, and effective diffusion coefficient of (220)Rn in uranium tailings were determined under certain environmental temperature and humidity conditions. Results show that: (1) The method and experimental setup presented in this study can simultaneously determine free (220)Rn production rate and effective diffusion coefficient of (220)Rn in porous media such as uranium tailing; (2) The free (220)Rn production rate in uranium tailings increases linearly with water saturation. Effective diffusion coefficient of (220)Rn, on the other hand, decreases exponentially with the increase in water saturation.