铁元素对铝热剂SHS核废物固化体性能的影响

研究了铁元素对用自蔓延高温合成（SHS）技术固化处理的核废物固化体的组成结构及化学稳定性的影响。借助XRD、SEM和TG-DSC等测试手段对固化体的矿相组合、微观结构和热稳定性进行了测试分析，采用PCT浸泡法对固化体的抗浸出性能进行了研究。结果表明：不同配比的固化体矿相结构基本相同，矿相的主要组成为Al₂O₃，Fe元素对固化体的矿相结构无明显影响。固化体的微观结构非常致密，结晶良好，但固化产物的气孔数量及孔径随Fe元素含量的增大而增大。在小于1400 ℃时，固化体无明显失重，具有良好的热稳定性。固化体中示踪核素Ce的28 d浸出速率为10^-5～10^-6 g/(m²?d)，固化体中Fe的含量在1%~10%范围内波动时，其对Ce、Ca、Si、Al、Fe的浸出速率无明显影响。

Effect of Iron on Performance of Simulated Nuclear Waste Form by Thermit SHS

The effects of Fe element on the structures and chemical stability of simulated nuclear waste immobilized by the thermit self-propagating high temperature synthesis (SHS) were investigated. The composition, microstructure, thermal stability, and the normalized release rate of the products were characterized by X-ray diffraction, scanning electron microscope, thermogravimetric and differential scanning calorimeter analysis, and product consistency test (PCT). The results show that the dominant crystalline phase of the immobilized SHS products is Al₂O₃, and Fe has no significant effect on the composition and structure of the products. The products have dense and well-developed crystal structure. But the apparent porosities and apertures increase with Fe content. The products also have good thermal stability without obvious weight loss at the temperature lower than 1 400 ℃. The leaching rate of Ce during 28 days is 10^-5-10^-6 g/(m²?d), and there are no significant changes in the normalized release rates of Ce, Ca, Si, Al and Fe when the Fe content of the products increases from 1% to 10%.