Specification of Np(V) and Np(IV) in Brine

在国际上，负责管理用过核燃料的机构正在考虑将结晶岩层或沉积岩中的深层地下储存库作为日益增加的用过核燃料库存的安全和长期解决办法。这些机构必须准备一份安全评估，以证明使用过的核燃料将在数十万年内得到安全管理。裂变产物和锕系元素的溶解和吸附行为与它们的形态密切相关。为了减少安全评估计算中的相关不确定性，需要提高对这些行为的科学理解。安大略省南部深层地下水的一个典型特征是，那里的水是高盐盐水，有几个城市表示有兴趣学习如何建立一个乏燃料储存库。然而，卤水中镎（Np）的形态尚不清楚。在本研究中，我们将(1)确定Np(V)和Np（IV）在盐水中的形态，(2)估计盐水中Np配合物的平衡常数，(3)发展研究盐水中形态的方法。首先，利用热力学数据库预测卤水中Np的形态。其次，结合光谱学、因子分析、溶剂萃取法和量子化学模拟，结合溶解度法和量子化学模拟，分别阐明Np(V)和Np（IV）的形态。最后，估算了Np(V)和Np（IV）在盐水中络合反应的平衡常数。我们提议的研究将在麦克马斯特大学建立一个前沿的锕系元素研究核心。这项研究将有助于提高对Np吸附的理解和预测，并减少盐水中安全评估计算的不确定性。重要的是，它还将有助于培养锕系化学和乏燃料管理工程领域的高素质人才。此外，该研究将有助于在卤水环境中建立锕系元素化学和工程的新前沿。

Internationally, agencies which have responsibility for used nuclear fuel management are considering deep underground repositories in either crystalline or sedimentary rock formations as a safe and long term solution to the growing used nuclear inventory. These agencies will have to prepare a safety assessment to demonstrate that used nuclear fuel will be safely managed over hundreds of thousands of years. The dissolution and the sorption behaviors of fission products and actinides significantly depend on their speciation. An improved scientific understanding of these behaviors is needed to reduce associated uncertainties in safety assessment calculations. One of the typical characteristics of deep groundwater in southern Ontario, where several municipalities have expressed interest in learning about hosting a used nuclear fuel repository, is that the waters are highly saline brines. However, the speciation of neptunium (Np) in brine is not yet understood. In this proposed research, we will (1) identify the speciation of Np(V) and Np(IV) in brine, (2) estimate the equilibrium constants of the Np complexes in brine, and (3) develop the methodology to study the speciation in brine. Firstly, Np speciation in brine will be predicted using thermodynamic databases. Secondly, Np(V) and Np(IV) speciation will be elucidated by combining spectroscopy, factor analysis, solvent extraction method and quantum chemistry simulation and by combining solubility method and quantum chemistry simulation, respectively. Finally, the equilibrium constants of complexation reactions of Np(V) and Np(IV) in brine will be estimated. Our proposed research will establish a cutting-edge research core of actinides at McMaster University. This proposed research will contribute significantly to improved understanding and predictions of Np sorption and to reducing uncertainty in safety assessment calculations in brines. Importantly, it will also contribute to the development of highly qualified personnel in the fields of actinide chemistry and engineering of used nuclear fuel management. Furthermore, this research will contribute to establishing a new frontier of actinide chemistry and engineering in the brine environment.