Caesium Mobility and Phase Separation Processes in Borosilicate Glasses

硼硅酸盐玻璃中铯的迁移率和相分离过程

• 批准号: EP/F011008/1
• 负责人: Ian Farnan
• 金额: $ 4.51万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FF011008%2F1
• 关键词: Caesium; Mobility; Phase; Separation; Processes

When nuclear fuel rods are removed from a reactor they contain, in addition to uranium dioxide (originally 235U enriched), a mixture of elements, including plutonium, that have been generated by the nuclear reactions that occur in the reactor. In the United Kingdom and in France these rods are 're-processed' to extract out plutonium, which may be used again as a nuclear fuel, and the uranium, now depleted in 235U, which can be mixed with the plutonium to make what is called mixed oxide or MOx fuel. This extraction is called the PUREX process and involves dissolving the rods in a highly acidic solution and extracting the plutonum and uranium with organic solvents. The atoms that have 'split' (called fission products) during the reactor process are left in the highly acidic and radioactive solution.This separation dramatically reduces the volume of nuclear waste material that needs disposal. The highly acidic and radioactive liquor remaining after the extraction of the plutonium and uranium is dried to an oxide powder and mixed with a base glass, made primarily from boron oxide and silicon dioxide, and heated to around 1100 degrees centigrade and turned into a glass. It is important for the quality (long term stability) of this material that all the fission products are adequately incorporated into the glass. Furthermore, the conditions required to produce the glass - high temperatures and intense radiation fields - make the process itself challenging with respect to the balance between temperature of operation, lifetime of melting equipment and the production of the highest quality waste glass i.e., avoidance of high solubility crystalline precipitates.This proposal intends to use high temperature nuclear magnetic resonance (NMR) spectroscopy to monitor the dissolution of two problematic elements, caesium (Cs) and molybdenum (Mo) into the borosilicate melt and the precipitation of Cs2MoO4 and related compounds during cooling. NMR is a very attractive technique for these materials because they are so complex in terms of composition. With NMR, specific elements can be observed independently of the rest of the material and so complex compositions are not an issue in determining which elements are involved in particular processes. This high temperature NMR method has been used successfully to look at molten silicates and borosilicates in the past by observation of boron and silicon behaviour. Here we are adapting these techiques to observe caesium and molybdenum. The outcome should be an understanding of the solubility of Cs and Mo into simplified melts and the real waste glasses (non-radioactive versions) provided by the French nuclear operators (Commissariat a l'Energie Atomique, CEA) and the UK nuclear operators (Nexia Solutions, BNFL group).

当核燃料棒从反应堆中取出时，除了二氧化铀（最初浓缩 235U）之外，它们还含有由反应堆中发生的核反应产生的元素混合物，包括钚。在英国和法国，这些棒被“重新加工”以提取钚，钚可以再次用作核燃料，而铀现在已贫化为 235U，可以与钚混合制成所谓的混合氧化物或 MOx 燃料。这种提取称为 PUREX 工艺，涉及将棒溶解在高酸性溶液中，然后用有机溶剂提取钚和铀。在反应堆过程中“分裂”的原子（称为裂变产物）留在高酸性和放射性溶液中。这种分离极大地减少了需要处理的核废料的体积。提取钚和铀后剩余的高酸性和放射性液体被干燥成氧化物粉末，并与主要由氧化硼和二氧化硅制成的基础玻璃混合，加热到1100摄氏度左右，变成玻璃。对于这种材料的质量（长期稳定性）来说，所有裂变产物充分融入玻璃中非常重要。此外，生产玻璃所需的条件 - 高温和强辐射场 - 使工艺本身在操作温度、熔化设备的使用寿命和最高质量废玻璃的生产之间的平衡方面具有挑战性，即避免高溶解度结晶沉淀物。该提案打算使用高温核磁共振 (NMR) 光谱来监测两种有问题的元素铯 (Cs) 的溶解情况 和钼 (Mo) 进入硼硅酸盐熔体，并在冷却过程中沉淀出 Cs2MoO4 和相关化合物。对于这些材料来说，核磁共振是一项非常有吸引力的技术，因为它们的成分非常复杂。通过 NMR，可以独立于材料的其余部分来观察特定元素，因此在确定特定过程中涉及哪些元素时，复杂的成分不是问题。这种高温核磁共振方法过去已成功用于通过观察硼和硅的行为来观察熔融硅酸盐和硼硅酸盐。在这里，我们正在采用这些技术来观察铯和钼。结果应该是了解法国核运营商（Commissariat a l'Energie Atomique，CEA）和英国核运营商（Nexia Solutions，BNFL 集团）提供的简化熔体和真实废玻璃（非放射性版本）中 Cs 和 Mo 的溶解度。

项目成果

95Mo NMR Study of Crystallization in Model Nuclear Waste Glasses

模型核废玻璃结晶的 95Mo NMR 研究

• 作者: S Kroeker (Author)