北山花岗岩/地下水厂址条件下Fe(II)对Se-79(IV)的还原阻滞作用研究

Se-79是高放废物地质处置中重点关注的放射性核素之一，主要以溶解度大、迁移性强的Se-79(IV)形式存在。在长时间尺度下，地下水中富含的Fe(II)对Se-79(IV)的还原沉淀作用将是地质处置库阻滞Se-79(IV)迁移最主要的方式，然而具体还原阻滞过程及作用机制尚不清楚。针对这一现状，本项目拟对北山花岗岩/地下水厂址条件下Fe(II)与Se-79(IV)的氧化还原行为进行深入探究，获取反应动力学曲线，建立反应速率与各影响因素之间的关系，并利用EXAFS/XANES、XPS等表征手段，探索反应机理，理清膨润土胶体等重点因素的作用机制。研究结果对于全面了解Se-79(IV)的地球化学行为及明晰深地质处置库对Se-79(IV)迁移的还原阻滞过程及作用机制具有重要的现实意义，也将为我国高放废物地质处置库的安全评价和工程设计提供基础数据支持。

Se-79 is one of the most important radionuclides in the geological disposal of high-level radioactive waste. It mainly exists as Se-79(IV) in the groundwater of disposal repository with high solubility and strong mobility. In the long time scale of geological disposal repository, reduction-precipitation is expected to be the main way to retard the migration of Se-79(IV). The redox behavior of Se-79(IV) and Fe(II)-mineral in disposal repository has always attracted more attention. However, the redox behavior of Fe(II) and Se-79(IV) in groundwater of disposal repository has not been reported, which is critical. On the basis of previous work, this project aims to investigate the redox behavior between Fe(II) and Se-79(IV) in Beishan granite/groundwater system and establish the relationship between the reaction rate and the influence factors. Combining EXAFS/XANES and XPS characterization, it is important to explore the reaction mechanism and make clear the mechanism of key factors such as bentonite colloid. The results have important significance for comprehensively understanding the geochemical behavior of Se-79(IV) and clarifying the reduction retardation process and mechanism of Se-79(IV) by deep geological repository. At the same time, it has important guiding significance to study the behavior of other polyvalent nuclides (such as Tc-99) and also can provide basic data support for safety evaluation and engineering design of geological disposal repository of high-level radioactive waste in China.