高放废物晶格固化用LaMgAl(11)O(19)材料的制备及其稳定性

Synthesis and Chemical Stability of LaMgAl_(11)O_(19) Ceramic Materials for the Lattice Solidification of High Level Radioactive Waste

高放废物的固化是防止核废料放射性扩散的第一道安全屏障。磁铁铅矿结构的LaMgAl_(11)O_(19)材料,因其高包容性、高致密、低核素浸出率、抗辐照稳定性等优点,被认为是核燃料循环后端克服玻璃固化技术固有缺陷、最具应用前景的新一代高放废物晶格固化候选陶瓷材料之一。本文采用柠檬酸溶胶-凝胶湿化学工艺制备了LaMgAl_(11)O_(19)陶瓷材料,借助X射线衍射、扫描电子显微镜及高分辨投射电子/选取衍射技术对材料的化学组分、微观形貌及电子衍射花样进行了表征;对LaMgAl_(11)O_(19)陶瓷材料经去离子水浸泡前后的组分、微观形貌、抗潮解性能进行了分析。结果表明,LaMgAl_(11)O_(19)陶瓷材料具有单一的六方磁铁铅矿型结构;经谢乐公式计算并结合扫描电子显微镜表征结果,1 500℃下保温4h样品的平均晶粒粒径为89.4nm;经去离子水浸泡48h后的LaMgAl_(11)O_(19)材料发生了潮解,因Mg^(2+)离子的溶出造成磁铁铅矿结构的失稳。本研究为后续商用高放废物晶格固化候选材料的实践应用提供了理论依据。

The solidification of high level radioactive waste is the first safety barrier to prevent radioactive radioactive waste proliferating. Due to high inclusion, high density, low leaching rate and anti-irradiation stability, magnetoplumbite-type LaMgAlll 019 are selected as the most promising new generation lattice solidification ceramic materials,which could overcome the inherent technology defects of glass solidification in the back- end of the nuclear fuel cycle. The LaMgAlll O19 ceramic materials were prepared by citric acid sol-gel chemical processing, the chemical composition, micromorphology and electron diffraction pattern were characterized by X- ray diffraction, scanning electron microscope and high resolution transmission electron microscope/selected area electron diffraction, respectively. The component, micromorphology and ant-deliquescence properties were analyzed before and after soaking in deionized water. The results indicate that LaMgAI~ O^9 ceramic materials have pure hexagonal magnetoplumbite crystal structure,the average crystalline grain size of the samples sintered at 1 500 ~C for 4 h was 89.4 nm which calculated by Scherrer formula and micromorphology. The bivalent Mgz＋ cation dissolving-out ofEMgO,~lattice result in the deliquescence and structural instability. This paper provides a theoretical basis for the commercial application of candidate lattice solidification materials which used to high level radioactive waste.