Na_2O/Al_2O_3摩尔比对模拟高放废液硼硅酸盐玻璃固化体结构和性能的影响

研究了Na2O/Al2O3摩尔比(n)对模拟高放废液硼硅酸盐玻璃固化体结构和性能的影响。利用红外光谱分析了不同Na2O/Al2O3摩尔比时硼硅酸盐玻璃固化体的结构变化,并用溶解速率法(DR)和全谱直读等离子发射光谱(ICP-OES)表征了所制备出固化体的化学稳定性。结果表明:在研究组分范围内,当n1.0时,硼硅酸盐玻璃固化体结构中Al以AlO4]四面体的形式存在,但BO3]三角体的量较大;随着Na2O/Al2O3摩尔比的增加(n=1.0),固化体结构中BO3]三角体向BO4]四面体转变,Al仍以AlO4]四面体的形式存在,固化体结构稳定性增加;Na2O/Al2O3摩尔比继续增加(n=1.5或2.0),固化体成分中由于Al含量已很少而使AlO4]含量过少,对固化体结构网络致密性的影响起主要作用,且此时成分中存在过多的碱金属离子在结构中起断网作用,玻璃固化体网络结构变疏松。在Na2O/Al2O3摩尔比为1.0时,玻璃固化体有相对较佳的结构稳定性和化学稳定性,浸泡56d后的失重速率为10-9 g/(cm2·min)数量级,且浸出液中各浸出离子的平均浓度最低。

Effects ofNa2O/Al2O3 Molar Ratio on the Structure and Performances of Borosilicate Glass Wasteforms for Simulated High-Level Radioactive Liquid Waste

The effect of Na₂O/Al₂O₃ molar ratios(n) on the structure and properties of borosilicate glass wasteforms was investigated. The structural changes of borosilicate glass wasteforms with different Na₂O/Al₂O₃ molar ratios were characterized by Fourier transform infrared spectroscopy(FTIR) analysis, and the chemical durability was measured by using dissolution rate(DR) method and direct reading plasma emission spectroscopy(ICP-OES). The results show that: within the studied composition scope, when n<1.0, Al exists as ［AlO₄］ tetrahedron in borosilicate glass wasteforms, but there are large number of triangular ［BO₃］ existed in its structure; with the increase of Na₂O/Al₂O₃ molar ratio (n=1.0), the structure stability of the wasteform increase for the transformations of triangular ［BO₃］ to ［BO₄］ tetrahedron; however, when the molar ratio of Na₂O/Al₂O₃ continually increase (n=1.5 or 2.0), the structure of glass wasteforms become poor, because Al content is very few result in too much decreased ［AlO₄］ content, which plays an important role in influence of the network density at this condition, and excessive alkali metal ions have the effect of broking network in the structure. When Na₂O/Al₂O₃ mole ratio is 1.0, the good structural and chemical stability are obtained. The value of DR for the glass wasteform is 10^-9 g/(cm²?min) order of magnitude after 56 d at 90℃, and the concentration of ions in leached water is the lowest.