放射性核素在处置库天然屏障材料中的迁移行为是评价处置库有效隔绝其进入生物圈的最重要因素之一。由于放射性核素的迁移和转化行为主要受其在固/液界面吸附过程的控制，开展放射性核素在天然屏障花岗岩中的微观地球化学过程尤为重要。本项目旨在分子尺度下探索Eu（作为Cm和Am等关键锕系元素的模拟物）和长寿命裂变产物 Se-79（半衰期 650,000 年）在花岗岩表面协同、耦合吸附机制。采用基于同步辐射扩展边 X 射线吸收精细结构谱（EXAFS）、微区X射线荧光光谱（µ-XRF）等实验技术探索复杂环境下Eu3+和SeO32-及SeO42-在花岗岩表面的吸附/解吸过程、表面分布特征以及其在花岗岩表面的微观吸附形态；研究不同类型核素之间的协同和耦合等微观作用机制；揭示复杂体系中放射性核素在花岗岩中迁移/滞留的规律。研究成果可为我国核裂变能大规模开发利用及环境保护等提供重要的基础理论和科学依据。

Radionuclides’ behavior in natural carrier of the high lever radioactive waste (HLW) repository is an important factor to evaluate whether the HLW is sufficient to retard radionuclides releasing into biosphere at a long term. As well known, the migration of radionuclides is mainly controlled by their sorption and desorption reaction in natural system. In this proposal, the synergistic and coupling sorption processes of Eu3+ (an analogy of Am3+ and Cm3+) and SeO32-/SeO42- (Se-79 is a typical fission product with a relative long half-life of 650,000 years) will be explored on granite at a molecular- and macro-scales. The surface speciation and distribution of Eu3+ and SeO32-/SeO42- on granite will be studied using synchrotron radiation extended X-ray absorption fine structure (SR-EXAFS) and SR-µ-X-ray fluorescence (SR-µ-XRF) under different environmental conditions. Moreover, the synergistic and coupling effect between Eu3+ and SeO32-/SeO42- will also be quantitatively investigated in a complicated condition. These findings can be adapted to the clarification of radionuclides migration, retard, and transformation in the natural carriers, and can provide important and basic supporting to the safety and performance assessment of HLW repository at theory and engineering level, which is related to the big development of atomic power plan in China.