铝热剂SHS固化模拟核废物产物的结构和性能分析

Analysis on the Structure and Properties of Simulated Radioactive Waste Obtained by Self-tpropagating High-temperature Synthesis with Thermit Reaction

本文以CeO_2作为示踪核素,SiO_2、Al2O_3和CaO混合物作为模拟砂土,在流动Ar气保护下,通过电加热引发铝热剂(Al和Fe2O_3物质的量比为2∶1),利用自蔓延高温合成(SHS)技术制备模拟核废物砂土固化产物。通过同步热分析、显气孔率测试、密度分析、X射线衍射分析、扫描电镜等手段分析了固化产物的表面形貌、组成结构和热稳定性。结果表明:采用SHS技术固化砂土,固化产物为无定形玻璃相和陶瓷相的混合物,改变固化比和示踪剂含量对固化体相结构组成的影响较小,固化产物密度在2.3～2.9g/cm3之间,高温状态下示踪核素Ce参与固化反应,主要以CeAl11O18形式和Ce2SiO5形式存在,固化体在常温到600℃具有较好的热稳定性。

Simulated solid nuclear wastes were obtained via self-propagating high-temperature synthesis(SHS)technology under protective Ar flow,initiated by the electric heating of thermit(n(Al)∶n(Fe 2O 3)=2∶1).In this study,CeO 2 was applied as the tracer element,while the mixture of SiO 2,Al 2O 3 and CaO was used as simulated sand.The surface morphology,compositions and thermal stability of the solid products were analyzed by simultaneous thermal analysis,open porosity test,density analysis,X-ray diffraction and scanning electron microscopy.The results indicated that the solidified products via SHS consisted of glassy amorphous and ceramic phases,while different ratio of raw materials and various contents of tracer element barely made a difference in the phase composition of solidified products.The densities of products by SHS were found to range from 2.3 g/cm 3 to 2.9 g/cm 3.Additionally,the tracer element Ce reacted with mixture and formed CeAl 11 O 18 and Ce 2SiO 5 at high temperature,whereas the solidified wastes maintained good thermal stability up to 600℃.