| A large amount of tailings and waste-ore are produced in the process of uraniummining and metallurgy and stacked in the tailings, which can release more than dozesof radionuclides with the characteristics of large quantity, long half-life and extensivedistribution. The radon exhalation rate is much greater than the national standard limitafter decommissioning and treatment during the operation of uranium tailingsimpoundment. And radon and its daughter diffuse to surrounding area by the air,which may pose a long-term potential radiation hazard to the environment and publics.The study on the propagation regularity and transport mechanism of radon during theoperation of the uranium tailings impoundment to control and mitigate the influenceof radon on the surrounding ecological environment and residents’ health is animportant research topic in the field of nuclear radiation protection.The atmosphere diffusion of radon which is precipitated from beach surface ofuranium tailings impoundment are affected by local topography, shape and the windfield characteristics of the tailings, etc. And the situation of vegetation coverage in thetailings is one of the main factors. In the paper, based on the CFD and porous mediamodel, the effect of vegetation on radon atmospheric diffusion, transportation, andradon concentration distribution is researched during the operation process and afterdecommissioning and treatment, and the environmental effect caused by radon is alsoanalyzed, that provide the scientific basis for the settings of protective scope arounduranium tailings impoundment.The main research contents contain several aspects:(1) An overview on the basic theory of and research methods on the atmosphericmigration and diffusion of radionuclide radon is introduced. The main effect factors ofatmospheric diffusion and transportation and the effect characteristics of vegetation on atmospheric dynamics and micro climate are discussed.(2) Based on the CFD and porous media model, numerical calculation method onatmospheric diffusion of radon in uranium tailings impoundment and vegetationmodel are built up. And the influence of small vegetation on local microclimate isanalyzed by example.(3) In allusion to flat-type uranium tailings impoundment, based on the dynamicsinfluence of vegetation on wind field, the contrast analysis of the influence of beachface with and without vegetation on atmospheric diffusion of radon is given bynumerical simulation method during the operation of uranium tailings impoundment.The influence of different wind speeds, formation directions, and the vegetationcoverage areas on concentration distribution of radon in uranium tailingsimpoundment is also studied.(4) Considering the vegetation transpiration and the dynamics influence ofvegetation on wind field synthetically, the distribution regularity of radonconcentration, temperature and humidity in the downwind direction of uraniumtailings impoundment is studied. Compared with radon concentration distributionafter decommissioning and treatment, environmental effects near the uranium tailingsimpoundment under low wind speed and the protective distance of uranium tailingsimpoundment are analyzed and evaluated. |
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