烧绿石是目前最受关注的一类锕系固化体材料，其化学形式为A2B2O7，具有两个不同的阳离子位点。由于锕系元素具有多重价态和复杂的5f成键行为，目前对于锕系元素在烧绿石中的赋存形式仍然存在争议。特别是在长期自辐照作用下锕系元素成键强度会发生变化，可能引发结构非晶化，导致放射性核素的大量泄露。因此本项目拟从原子分子水平出发，依托基于同步辐射的高分辨吸收谱学技术（HERFD-XAS/RXES）系统研究两种关键放射性核素（Th、U）的配位结构和电子结构对烧绿石辐照结构稳定性的影响机制，探索不同合成条件下Th、U占位的可能性，研究不同占据位点、价态与结构包容性之间的关系；重点研究辐照前后不同锕系元素占据位点相应的配位数、5f电子占据数、成键强度等配位和电子结构与宏观结构稳定性之间的关联机制，指导设计在极端条件下具有高稳定性的烧绿石固化存储材料。

Pyrochlore is one of the most popular type of actinide solidification material. Its ideal chemical formula is A2B2O7, with two different cationic sites. Due to the multiple valence states and complex 5f electronic properties of actinide, there is still a controversy about the actinide behaviors in pyrochlore. In particular, the bonding strength of actinide elements in long-term self-irradiation can change, which may lead to structural amorphization, then leading to a large amount of radionuclide leakage. In this project, we will study the influence mechanism of the coordination structure and electronic structure of two key radionuclides (Th, U) on the structural stability of pyrochlore under irradiation using advanced high resolution absorption spectroscopy technology (High energy resolution fluorescence detected XAS, HERFD -XAS/ Resonant x-ray emission spectroscopy, RXES). We will explore the occupying site of Th and U under different synthesis conditions, and establish the relationship between the occupy site, valency state and structural tolerance. We will systematically study the correlation mechanism between the coordination and electronic structure in different cation site including the coordination number, 5f occupation number and bond strength and structural stability of pyrochlore before and after irradiation, to guide the design of nuclear waste solidification molecular materials.