降雨对铀尾矿库地下水中核素迁移影响的模拟研究

Simulation research on the effects of precipitation on the nuclide migration in the groundwater of the uranium tailings impoundment

为了揭示铀尾矿库周边放射性核素在地下水中的迁移扩散规律,以迁移能力强、半衰期长的放射性核素铀为研究对象,以我国南方某大型铀尾矿库为例,应用GMS(Groundwater Modeling System)中的MODFLOW和MT3D模块分别进行流场和溶质迁移模拟。考虑研究区降雨随季节变化明显的特点,分别模拟了枯水期、丰水期铀的迁移扩散情况。结果表明,降雨对尾矿库核素铀在地下水中的迁移扩散影响较大,丰水期铀的迁移速度约为枯水期时的11.4倍。

The paper is to discover the regularity of the transmission and diffusion of the radionuclide in the groundwater near uranium mining tailings impoundment Due to its strong migration ability and long half-decay period, the radioactivity of the uranium nuclide has become a hot subject in the nuclear science research. The present paper has taken a large uranium tailings impoundment in South Chinaas the case study by adopting MODFLOW module and MT3D module in the Groundwater Modeling System （GMS） to the flowing simulation and fluid transmission simulation, respectively. Seeing the noticeable seasonal precipitation changes in the research spots （mainly in the 3 - 6 months every year）, we have been conducting our simulation ac- tivities in uranium transmission and diffusion in dry seasons and rainy seasons respectively in hoping to work out a survey map of the water level and uranium concentration isaline in the groundwater around the uranium tailing impoundment under different precipitation conditions. In the simulation activities, the migration period of ours lasts 120 days with all the models. According to the different precipitation con- ditions in the research spot, we have set up four different kinds of in- filtration rate and infiltration concentrations. And we have found that, when the infiltration rate is 0.000 8 and the infiltration concentration is 5 mg/L, the migration velocity of uranium in the groundwater would be equal to 11.4 times as compeercd with the infiltration rate of 0.000 4 and the infiltration concentration of 0.705 mg/L. This shows that the precipitation tends to exert a great influence on the trans- portation and diffusion of the uranium in the groundwater of the urani- um mining tailings impoundment. And, both the infiltration rate and the infiltration concentration influence the migration of the uranium obviously, and, moreover, the influence of the latter seems much greater than the former. In addition, we have found that the migration velocity of uranium in dry seasons proves 11.4 times stronger than that of the rain seasons. Therefore, it can be concluded that the flood control and drainage is of great importance for controlling the trans- portation and diffusion of theuranium radioactivity in the groundwater near the uranium tailings impoundment.