【作者】 韦红钢；

【导师】 钟佐燊； 孙占学；

【作者基本信息】 中国地质大学（北京） ， 环境科学与工程， 2012， 博士

【摘要】 放射性核素的迁移行为研究是高放废物地质处置中的一项热门难点研究内容。本论文从水动力学、水文地球化学角度对放射性核素U和Sr在中国高放废物北山处置库预选场花岗岩裂隙水中的运动特征展开研究。预测了处置库破坏后核素的迁移行为。本项研究主要的工作和创新成果如下:（1）通过研究高放废物处置预选场研究区裂隙水水文地质特征与水动力特性,建立核废物处置场地下水运动的概念模型和迁移模型,并推导出岩石裂隙地下水中的数值解。在此基础上,利用MATLAB计算核素U、Sr在花岗岩裂隙域与基质域中的相对浓度分布和迁移距离。在花岗岩裂隙域中,U在地下水中迁移距离为500～700米,而Sr迁移距离为1400～1600米,Sr在地下水中迁移的距离比U要长;核素U、Sr在基质域中,迁移距离相同点处的核素相对浓度都随扩散距离增大而减小。（2）通过水文地球化学模拟软件PHREEQC -Ⅱ对研究区钻孔地下水和乌龙泉水中U、Sr元素形态计算分析表明地下水中铀的主要形态仍以UO₂（CO₃）₃^4-、UO₂（CO₃）₂^2-、UO₂CO₃⁰和（UO₂）₃（OH）₅⁺为主,锶主要形态为Sr²⁺和SrSO₄⁰占据主导地位。对比污染物（铀和锶）全部进入含水层后和天然状态下的U、Sr的形态分布结果表明元素形态分布大致相同,但含量有一定变化。（3）利用PHREEQC -Ⅱ分别模拟污染物铀、锶连续源和瞬时源进入研究区地下水后浓度随时空的分布。同时还对迁移的pH、弥散度、扩散系数和温度等影响因素进行模拟分析。模拟结果表明:瞬时源进入地下水后,728年后,铀含量已迁移到极限距离。连续源情况下,同一距离处U、Sr元素的浓度随着时间的迁移不断升高,直至达到初始浓度;在6952年的时候1995m处铀浓度达到其值为2.07×10^-6mol/L、锶浓度其值为5.63×10^-6mol/L,均接近国家饮用水卫生标准。（4）采用批式法测定不同因素如pH值、浓度、温度等对铀在北山处置场粉碎花岗岩岩石中分配系数K_d值的影响。结果表明,体系在2-3d左右达到吸附平衡。温度增高会导致铀的分配系数K_d值的变化,但吸附效率影响不大。pH值和核素浓度对铀在地下水中吸附扩散影响比较显著。铀在北山花岗岩上的吸附符合Fruendlich等温吸附方程。更多还原

【Abstract】 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）₃^4-、UO₂（CO₃）₂^2-、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 K_d 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 K_d 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.更多还原