Neill Thomas S, Morris Katherine, Pearce Carolyn I, Sherriff Nicholas K, Bryan Nick, Rigby Bruce, Shaw Samuel
Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth & Environmental Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
Langmuir. 2022 Mar 15;38(10):3090-3097. doi: 10.1021/acs.langmuir.1c02927. Epub 2022 Feb 28.
Spent nuclear fuel contains both uranium (U) and high yield fission products, including strontium-90 (Sr), a key radioactive contaminant at nuclear facilities. Both U and Sr will be present where spent nuclear fuel has been processed, including in storage ponds and tanks. However, the interactions between Sr and U phases under ambient conditions are not well understood. Over a pH range of 4-14, we investigate Sr sorption behavior in contact with two nuclear fuel cycle relevant U(IV) phases: nano-uraninite (UO) and U(IV)-silicate nanoparticles. Nano-UO is a product of the anaerobic corrosion of metallic uranium fuel, and UO is also the predominant form of U in ceramic fuels. U(IV)-silicates form stable colloids under the neutral to alkaline pH conditions highly relevant to nuclear fuel storage ponds and geodisposal scenarios. In sorption experiments, Sr had the highest affinity for UO, although significant Sr sorption also occurred to U(IV)-silicate phases at pH ≥ 6. Extended X-ray absorption fine structure (EXAFS) spectroscopy, transmission electron microscopy, and desorption data for the UO system suggested that Sr interacted with UO via a near surface, highly coordinated complex at pH ≥ 10. EXAFS measurements for the U(IV)-silicate samples showed outer-sphere Sr sorption dominated at acidic and near-neutral pH with intrinsic Sr-silicates forming at pH ≥ 12. These complex interactions of Sr with important U(IV) phases highlight a largely unrecognized control on Sr mobility in environments of relevance to spent nuclear fuel management and storage.
乏核燃料含有铀（U）和高产率裂变产物，包括锶-90（Sr），这是核设施中的一种关键放射性污染物。在处理乏核燃料的地方，包括储存池和储罐中，都会存在U和Sr。然而，在环境条件下Sr与U相之间的相互作用尚未得到充分了解。在pH值为4至14的范围内，我们研究了与两种与核燃料循环相关的U(IV)相接触时Sr的吸附行为：纳米晶质铀矿（UO）和U(IV) - 硅酸盐纳米颗粒。纳米UO是金属铀燃料厌氧腐蚀的产物，并且UO也是陶瓷燃料中U的主要形式。U(IV) - 硅酸盐在与核燃料储存池和地质处置场景高度相关的中性至碱性pH条件下形成稳定的胶体。在吸附实验中，Sr对UO具有最高的亲和力，尽管在pH≥6时Sr也会大量吸附到U(IV) - 硅酸盐相上。对于UO体系的扩展X射线吸收精细结构（EXAFS）光谱、透射电子显微镜和脱附数据表明，在pH≥10时，Sr通过近表面的高配位络合物与UO相互作用。对U(IV) - 硅酸盐样品的EXAFS测量表明，在酸性和近中性pH条件下，外层Sr吸附占主导，在pH≥12时形成本征Sr - 硅酸盐。Sr与重要的U(IV)相之间的这些复杂相互作用突显了在与乏核燃料管理和储存相关的环境中，对Sr迁移率的一种很大程度上未被认识到的控制作用。
