Abstract: Radon is the main gaseous radioactive effluents released in the process of uranium mining and metallurgy, and radon release in in-situ leaching uranium mine borehole area mainly comes from the liquid extraction hole. The applicability of the traditional Gaussian model to such source terms is limited. Concentration distribution characteristics of radionuclide radon near ground surface in borehole area and its surroundings of a typical in-situ uranium leaching mine was studied by establishing CFD atmospheric diffusion mathematical model to couple solution under the actual terrain, radon source term and 2019 meteorological data, and the annual effective dose of the public was calculated by the annual average distribution mathematical model of individual dose. The results showed that terrain and wind speed had an important impact on radon diffusion in the drilling site, and wind speed played a dominant role. The higher the wind speed, the lower the radon concentration. Low and concave areas were easy to cause radon accumulation near emission sources, and local pollution was heavier. The distribution range of radon near the ground was mainly affected by the synergistic effect of wind speed and wind direction frequency, which grew as the latter increases. There was a positive correlation between radon concentration decay rate and diffusion distance. However, the radon emission concentration was at low level from liquid extraction hole, which had small contribution to the environmental radon concentration, impact on the surrounding environment and the public radiation, and the individual dose was not more than 0.001 1 mSv·a^-1. This study provides the theoretical supports for the layout of borehole area and the determination of the radiation safety distance.

Key words: in-situ uranium leaching, borehole area, radon diffusion, CFD, radiation safety distance