Estimation of radon release rate for an underground uranium mine ventilation shaft in China and radon distribution characteristics.

Radon, known to be a human carcinogen, is one of the most concerned radionuclides in uranium mining which need to be monitored and controlled. A large amount of radon is discharged to the atmosphere mainly through underground ventilation shafts for underground uranium mining. There are many studies on radon release of uranium mine, but the differences of the measured radon results are very big. In this paper, a typical underground uranium mine in China is chosen as a case study. This study finds that distribution of radon concentration and airflow speed inside the ventilation shaft are extremely uneven, but the distributions are respectively stable and regular for a fixed cross-section at the wellhead depth of 0-1 m. There is also a stable numerical relationship between the radon release rate and the product of radon concentration and airflow speed at the center for any cross-section in the shaft. Based on this regulation, a multipoint interpolation-integration method and a one-point method for calculating radon release from underground ventilation shaft are proposed in this paper. The results show that the difference between these two methods is 2-10%, the one-point method is more suitable and convenient to be applied for the long-term monitoring radon release rate from uranium mine ventilation. The research results in this paper can be applied in the estimation of radon release rate for other underground uranium ventilation shafts.