Ruthenium: Nuclear's Volatile Problem

钌：核能的不稳定问题

• 批准号: 2504922
• 金额: --
• 依托单位: Lancaster University
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2504922
• 关键词: Ruthenium; Nuclear; Volatile; Problem

Ruthenium is a fission product possessed of two relatively long lived stable isotopes: Ru-103 (half life = 39.8 days) and Ru-106 (half life = 1 year). Both isotopes are present in UK spent fuel and so have had to be accounted for during the reprocessing or disposal of that fuel. At a number of stages during the processing of spent fuel, ruthenium can be exposed to high nitric acid, high temperature conditions that may lead to its transfer into the gas phase as ruthenium tetroxide. Two such stages are the dissolution of spent fuel into concentrated nitric acid at the start of reprocessing, and the vitrification of ruthenium into a glass waste form after reprocessing has occurred.Volatilisation is to be avoided as the resultant gas phase ruthenium may then redeposit within metal pipework elsewhere in the plant which will then have to be decontaminated. However, ruthenium volatilisation occurs at unexpectedly low temperatures. Whilst RuO2 is not seen to volatilise below 900oC, gaseous ruthenium oxides have been seen to evolve from solutions of Ru in nitric acid at temperatures as low as 150oC - making the management of ruthenium difficult during reprocessing and vitrification.Thus, given its volatile nature and high specific radioactivity ruthenium presents a strong challenge to the nuclear industry in effectively managing its abatement. Key challenges are to fully understand the highly complex solution/solid state chemistries that obtain not only under conditions relevant to dissolvers, evaporators and vitrification plants, but also in the decontamination methods used in its clean up. Using a combination of chemical, analytical and engineering approaches, we shall seek to address these challenges in this PhD. The specific objectives of the PhD will be to:1) Develop gravimetric, mass spectroscopic, electrochemical and spectroscopic analytical methods that will improve the understanding of ruthenium speciation in high nitric acid environments and oxidation state interconversion during oxidative / thermal treatment of same.2) Using these methods, to establish the kinetics of interconversion between ruthenium species, most especially Ru(III) to Ru(IV) and Ru(VIII) and Ru(IV) to Ru(VIII), and the resultant product distributions of these processes.3) To establish the influence that Ru(III) complexation may have on these interconversions and the role that RuO2 may have in supporting or inhibiting volatilisation.4) Establish the mechanism by which other fission product metal ions such as Ce(IV) may oxidise and thus potentially volatilise ruthenium.5) Investigate the role that key NOx species such as NO and HNO2 may have on oxidising Ru(III) directly or inhibiting the putative Ce(IV)-driven oxidation of Ru(III).

钌是一种裂变产物，具有两种相对长寿命的稳定同位素：Ru-103（半衰期= 39.8天）和Ru-106（半衰期= 1年）。这两种同位素都存在于联合王国的乏燃料中，因此在对该燃料进行后处理或处置时必须加以说明。在乏燃料处理过程中的若干阶段，钌可能暴露于高硝酸、高温条件下，这可能导致其作为四氧化钌转移到气相中。其中两个阶段是在后处理开始时将乏燃料溶解在浓硝酸中，以及在后处理发生后将钌玻璃化为玻璃废物形式，必须避免挥发，因为生成的气相钌可能会重新沉积在工厂其他地方的金属管道中，然后必须对这些管道进行去污。然而，钌挥发发生在意想不到的低温下。虽然RuO 2在900 oC以下不会挥发，但钌的硝酸溶液在150 oC的低温下会产生气态氧化钌，这使得后处理和玻璃化过程中钌的管理变得困难。因此，鉴于其挥发性和高比放射性，钌对核工业有效管理其减排提出了巨大挑战。关键的挑战是要充分理解高度复杂的溶液/固态化学，不仅在与溶解器，蒸发器和玻璃化工厂相关的条件下获得，而且在其清理中使用的去污方法中获得。使用化学，分析和工程方法的组合，我们将寻求解决这个博士学位的这些挑战。博士的具体目标将是：1）开发重量分析、质谱、电化学和光谱分析方法，其将改进对高硝酸环境中的钌物种形成和在其氧化/热处理期间的氧化态互变的理解。2）使用这些方法，建立钌物种之间的互变动力学，最特别是Ru（III）至Ru（IV）和Ru（VIII）以及Ru（IV）至Ru（VIII），以及这些过程的产物分布。3）确定Ru（III）络合对这些相互转化的影响以及RuO 2在支持或抑制挥发中的作用。4）建立其他裂变产物金属离子（如Ce（IV））可能氧化并因此潜在挥发Ru（III）的机制。5）研究关键NOx物质（如NO和HNO 2）可能直接氧化Ru（III）或抑制推定的Ce（IV）驱动的Ru（III）氧化的作用。