Numerical Modeling On Radioactive Diffusion Of Uranic Well Exhaust Gas In Atmosphere

Ventilation exhaust gases of uranium dusts, radon and its progeny emitted from the process of uranium mining to surrounding environment have the wide influencing scope, a long half-life period and accumulation effect under the dispersion of atmospheric downward direction. The radioactive pests have contribution to public collective effective dose and could pose potential hazards to the nearby ecological environment and resident health.Radionuclides migration in atmosphere is influenced by mine location, atmospheric wind fields, features of pollution source, underlying surface conditions and the climatic characteristics. Research of radioactive radionuclides about transport and diffusion mechanism is the basis for reasonable predicting and evaluating safety protection distance, and also is the emphasis subjects of atmospheric contamination-controlling and nuclear radiation protection.Supported by National Natural Science Foundation of China(Grant No. 11105068), and based on underlying surface roughness degrees, shaft height and the climatic characteristics of atmospheric stability and wind direction, numerical simulation investigation on the migration status of radionuclides are accomplished in this dissertation. In summary, this dissertation includes the following main contents:(1) The related research contents and methods both at present are investigated systematically in domestic and international field. Various factors affecting radionuclides migration about uranium well exhaust gas in atmosphere are summarized. Main research factors are decided for the studies of radionuclides dispersion, such as underlying surface roughness degrees, shaft height and the climatic characteristics of atmospheric stability and wind direction.(2) Three dimensional physical model of the atmospheric flow filed environment considered in paper is based upon an actual uranium-bearing terrain, and numerical simulation methods are used to solve complicated mathematical models of transportation and diffusion for radioactive radionuclides in atmosphere. The atmospheric wind features and dispersion mechanism of radionuclides migrations at uranium mine are obtained. It provides useful data to reasonably estimate public radiation dose for uranium mine ventilation shaft exhausts and accelerates sustainable development of nuclear industry in China.(3) Radon concentration distributions are studied on factors of roughness degree, release height and atmospheric stability, and the comparisons of diffusion effect of nuclide migration are conducted under these three factors. Investigations about control effect of releasing heights to diffusion distance from ventilation shaft are used to guide the design and location of uranium mine well.(4) Based on seasonal variation of surface roughness and atmospheric stability, the researches on nuclide radon diffusion impact of winter, summer and transition seasons are carried out and collective effective dose located at surrounding region of uranium mine is evaluated to reveal the seasonal characteristics of radon migration in atmosphere from uranium mine shaft exhausts.