^(241)Am 在包气带粉质黏土中的迁移行为研究

Migration Behavior of^(241)Am in Silty Clay in Vadose Zone

为科学评估处置场的环境风险,需了解放射性核素在地质环境中的迁移行为和规律。以西北干旱地区包气带粉质黏土介质为研究对象,通过室内静态批式法及动态土柱迁移实验,结合数值模拟技术,利用Hydrus-1D建立溶质迁移数值模型模拟相关实验参数,开展^(241)Am在包气带粉质黏土中的迁移行为研究。研究结果表明:^(241)Am的迁移曲线呈单边下降形态,核素比活度主要分布在2.5 cm内,峰值比活度为342.38 Bq·g^(-1)。拟合得到弥散度DL为0.8 cm,分配系数为3000 mL·g^(-1),一级速率系数β为0.015 d^(-1)。静态批示法测量与动态土柱迁移实验模拟分别得到的^(241)Am分配系数值相差不大。给出的^(241)Am在包气带粉质黏土中的迁移行为研究可为现阶段放射性废物处置场安全全过程系统分析提供数据与理论支持,为新建近地表处置场的选址、建设等工作构建技术基础。

In order to scientifically evaluate the environmental risk of a disposal site,it is necessary to understand the migration behavior and fate of radionuclides in the geological environment.In this paper,silty clay medium in vadose zone in arid area of northwest China is taken as the research object,which was tested by indoor static batch method and dynamic soil column migration experiment,combined with numerical simulation technology.Software Hydrus-1D was used to establish a solute migration numerical model to simulate relevant test parameters,and the migration behavior of^(241)Am in the vadose zone was studied.The results show that the migration curve of^(241)Am shows a unilateral decline,and the specific activity of nuclides is mainly distributed within 2.5 cm,with a peak specific activity of 342.38 Bq·g^(-1).The fitted dispersion DL is 0.8 cm.The distribution coefficient is 3000 mL·g^(-1),andβis 0.015 d^(-1).The distribution coefficient of^(241)Am measured by static indication method is not much different from the dynamic distribution coefficient of^(241)Am obtained by dynamic soil column radionuclide migration experiment simulation.The migration behavior of^(241)Am in silty clay in vadose zone given by this study can provide data and theoretical support for the safety case at this stage,and build a technical foundation for the site selection and construction of new near-surface disposal site.