| The behavior of the radionuclides migration in groundwater is a hot-button and difficult point in geological disposal of high level radioactive waste(HLW). From the water dynamics, hydrogeochemical perspective,this paper mainly researches the characteristic of the radionuclides U and Sr in the granite fracture water in China's HLW disposal preliminary site in Beishan area, and predicts the nuclides migration behavior when repository is destructed sometime in future.The main works and innovation achievements in this paper are as follows:(1) Through the research of water dynamic and hydrological characteristics in the research area, the conceptual and mathematical models of solute transport in rock fracture are built deduced by Laplace transform. Their transport distance and relative concentrations of U and Sr in fracture domain and diffusion depth in matrix domain are researched by MATLAB in detail. The transport distance in fracture domain of U in the groundwater is about 500 to 700 meters, and Sr is between 1400 and 1600 meters. Sr in groundwater migration distance is longer than U; Radionuclide U and Sr in matrix domain and migration distance fixed the nuclide after the relative concentrations of distance with the diffusion and decreases.(2) It uses hydrogeochemical simulation software- PHREEQC -Ⅱto calculate and analyze the species of U and Sr in drilling groundwater and WULONG spring. Furthermore, It comprises the distribution of pollutants(uranium and strontium) between they enter into the aquifer and in natural state, The results show that the main species of uranium in the groundwater are still predominantly made up of UO2(CO3)34-,UO2(CO3)22-,UO2CO30 and(UO2)3(OH)5+and the main species of strontium exists dominantly with Sr2+ and SrSO40. The species distribution of the groundwater and the spring is roughly same and contents are some changed after pollutants enter.(3) It uses PHREEQC -Ⅱsoftware to simulate uranium and strontium concentration changed with time and distance as instantaneous and continuous source respectively entering groundwater in the study area. The influence factors such as pH,dispersion,diffusion coefficient and temperature are also simulated. The research results show that pollutants uranium as instantaneous source migrates with a limit distance after 728 years. In continuous source circumstance, U, Sr concentration increases with time in the same distance place until it reaches the initial concentration; When uranium concentration in 1995m place reaches 2.07×10-6mol/L in 6952 years, strontium concentration is 5.63×10-6mol/L, all are close to national drinking water hygiene standards.(4) It analyzes the influence of the different factors including pH, concentration, temperature, etc. to distribution coefficient Kd value in crushed granite rocks in Beishan area by batch method. The results show that the system achieves adsorption equilibrium around 2-3d. The temperature increasing results in Kd changes with little effects on adsorption efficiency. The pH and nuclide concentration plays a more significant role and the adsorption of Uranium in Beishan granite accords with Fruendlich isothermal adsorption equation.
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