Method Development for High Temperature In-Situ Neutron Diffraction Measurements of Glass Crystallization on Cooling from Melt
Method Development for High Temperature In-Situ Neutron Diffraction Measurements of Glass Crystallization on Cooling from Melt
复制标题
熔体冷却时玻璃结晶的高温原位中子衍射测量方法开发
作者：
J. McCloy;J. Marcial;B. Riley;J. Neuefeind;J. Crum;D. Patil
玻璃陶瓷硼硅酸盐废物形式正在考虑用于固定由超铀提取产生的碱、碱土、镧系元素和过渡金属的废物流，用于再加工用过的核燃料。废物形式是通过冷却时部分结晶产生的，主要是氧磷灰石和磷灰石相。进行原位中子衍射实验以获得有关从 1200°C 冷却时结晶的详细信息。硼硅酸盐玻璃与中子实验中使用的典型容器（例如钒和铌）的高温和反应性相结合，阻碍了它们在这里的使用。因此，开发了使用密封厚壁二氧化硅安瓿的方法进行原位研究。出乎意料的是，高中子吸收、低晶体分数和高二氧化硅容器背景使得这些高温测量的量化变得困难。随后，对不同的潜在高温容器材料进行了概念验证测量，重点是结晶材料，以便更容易分析废物样品中的残留玻璃。在低温下稳定的“理想”容器（即钒和薄壁二氧化硅毛细管）中对预结晶样品进行室温测量，并与在高温下稳定的容器（即铂、单晶蓝宝石和厚壁二氧化硅安瓿）中进行的相同测量进行比较。结果表明，如果适当密封以防止中子激活后样品受到污染，Pt 可能是最佳选择。
A glass-ceramic borosilicate waste form is being considered for immobilization of waste streams of alkali, alkaline-earth, lanthanide, and transition metals generated by transuranic extraction for reprocessing used nuclear fuel. Waste forms are created by partial crystallization on cooling, primarily of oxyapatite and powellite phases. In-situ neutron diffraction experiments were performed to obtain detailed information about crystallization upon cooling from 1200°C. The combination of high temperatures and reactivity of borosilicate glass with typical containers used in neutron experiments, such as vanadium and niobium, prevented their use here. Therefore, methods using sealed thick-walled silica ampoules were developed for the in-situ studies. Unexpectedly, high neutron absorption, low crystal fraction, and high silica container background made quantification difficult for these high temperature measurements. As a follow-up, proof-of-concept measurements were performed on different potential high-temperature container materials, emphasizing crystalline materials so that residual glass in the waste form sample could be more easily analyzed. Room temperature measurements were conducted with a pre-crystallized sample in ‘ideal’ containers stable at low temperatures (i.e., vanadium and thin-wall silica capillaries) and compared to the same measurements in containers stable at high temperatures (i.e, platinum, single crystal sapphire, and thick-walled silica ampoules). Results suggested that Pt is probably the best choice if suitably sealed to prevent contamination from the sample after neutron activation.