A laboratory method for concurrently determining diffusion migration parameters and water saturation effects of...

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