Geochemical analysis for long term effect and stability of engineering barrier

高放射性废物处置的废物管理是防止放射性废物处置孤立于人类的有希望的方法。然而，这一情景是在假定工程屏障的性质在很长一段时间内是唯一的前提下得出的。事实上，我们知道，蒙脱石是通过与地下水中的阳离子离子交换而变成伊利石的。研究结果可以评价蒙脱石转化为伊利石对膨润土迁移的影响。结果总结如下。(1)膨润土孔隙水的ph、氧化还原电位和碳酸浓度等化学条件在恶化前进行了实验测量，可以编辑的是，这些数值与模拟结果一致。结果表明，镅通过附着于膨润土上的微孢子而转变为伪胶体。通过假设伪胶体，可以从理论上解释实验测量的对镅吸附的影响。(2)通过实验测量蒙脱石、伊利石和混合物的吸附分布系数，并利用这些测量数据和Altarner模型，建立了可以定量解释其性质变化的模型。通过对蒙脱石、伊利石及不同配比的混合物的吸附分布系数的测定，确定了这些元素的吸附特性。(3)根据(1)和(2)的结果，建立了考虑膨润土随时间变化的放射性核素迁移模型。模拟结果表明，膨润土性质随时间的变化定量地影响了膨润土中的迁移。

Waste management of high revel waste disposal is the hopeful method to prevent isolate radioactive waste disposal from human beings. The scenario, however, is concluded on the assumptions that the properties of engineering barrier is unique for a long time. In fact, it is known that smectites change into illites by ion-exchange with cation in the ground water.As a result of this research, The effect that smectites change into illites, on migration in the bentonite can be evaluated. Results are summarized as follows.(1) Chemical conditions, i.e.pH,oxidation-reduction potential and concentration of carbonate acid of the water in the bentonite porosity, were experimentally measured before worsening and it can be edited that those values agree with the simulation results. It is made clear that americium change into pseudo-colloids by attaching to microsperes from bentonite. By supposing pseudo-colloids, that experimentally measured effect on adsorb of americium can be explained theoretically.(2) By exprimentally measuring sorption distribution coefficient of smectites, illites, and mixture and using these measured data and Altarner model, a model, by which the change of properties can be quantitatively explained, was made. Furthermore, By measuring sorption distribution coefficient for smectites, illites, and mixture with another mixing ratio, the properties of these elements were found out.(3) According to results of (1) and (2), a model of radionuclide migration was made, considering change of bentonite as time passed. The results of simulation show that the change of bentonite property dependant on time quantitatively makes effects on the migration in bentonite.