闪烧制备钆锆烧绿石模拟锕系核素固化体的机理性研究

The disposal of high level waste (HLW) is critical to national security and citizens' health, so it has been the focus of research on radiative wasteform for long time. Gd2Zr2O7 pyrochlore, which is an ideal candidate for HLW wasteform, possesses long time chemical and physical stability, and is highly resistant to radiation. However, the problem of HLW ceramic wasteform lies on the inmature sintering and synthesizing techniques. In view of the urgency of our country's HLW wasteform needs, this project will apply flash sintering in the field of HLW wasteform for the first time and carry out a systematic study on the synthesis of simulative HLW doped Gd2Zr2O7 pyrochlore. It is expected to lower the sintering temperatures of HLW wasteform, reduce the risk of evaporation of HLW element and also lower the processing cost. The immobilizing mechanisms of the simulated elements in Gd2Zr2O7 pyrochlore based wasteform will also be studied. This project will use Cs-corrected TEM to observe the structures of Gd2Zr2O7 pyrochlore prepared by flash sintering on atomic scale, and reveal the mechanisms of flash sintering of Gd2Zr2O7 pyrochlore. This project will not only enrich the physical meanings of materials science, promote the development of theoretical and application study of flash sintering, but also enhance the our country's HLW wasteform research.

高放废物处理关系着国家和人民生命财产安全，是国内外放射性废物处理的研究重点。钆锆烧绿石具有长期的物理化学稳定性和较好的抗辐照能力，是高放废料固化的理想基材。然而，目前陶瓷固化技术的核心问题还在于基材的合成技术不够成熟。鉴于我国高放核废料固化的急切需求，本项目首次将闪烧法应用于高放废料陶瓷固化领域，开展钆锆烧绿石模拟锕系元素固化体制备工艺的系统研究，有望借助闪烧的低温和快速效应显著降低核废料的固化温度、有效降低核素挥发风险并且降低固化成本；进而研究模拟核素的固化机制；巧妙引入高分辨双球差校正透射电镜对闪烧样品进行原子像观察，揭示闪烧制备钆锆烧绿石的反应烧结机理。本项目不仅可以丰富材料科学的物理内涵，推动闪烧技术的理论和应用研究，而且促进我国在高放废料固化领域的研究进展。

针对高放废料处置中现有玻璃固化技术储存寿命有限、热力学不稳定的问题，项目利用陶瓷材料较好的热力学和机械性能，开展了模拟高放废料陶瓷固化的研究。项目开发了闪烧设备，创建了闪烧制备高放废物陶瓷固化的新方法体系，闪烧制备的模拟放射性元素固化体的关键性能达到了与传统烧结材料同样的水平，而烧结温度比传统烧结降低了500 ℃（降低了1/3），烧结时间从72小时缩短到1分钟，大幅提升了制备效率、降低了制备成本。目前为止，与国际文献报道中的烧结技术相比，我们采用闪烧技术制备的Gd2Zr2O7 材料的烧结温度是最低的，充分发挥了闪烧的优势。同时，项目深入研究制备工艺和A2B2O7类材料物相组成、微结构之间的关联性，揭示了A2B2O7类材料的闪烧机理。