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

在国际上，负责乏核燃料管理的机构正在考虑将晶体或沉积岩层中的深层地下处置库作为日益增长的乏核库存的安全和长期解决方案。这些机构将不得不准备一份安全评估，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在土壤中的溶解和吸附行为与它们的形态有关。需要对这些行为有更好的科学理解，以减少安全评估计算中的相关不确定性。安大略南部深层地下水的一个典型特征是沃茨，那里的几个市政当局表示有兴趣了解如何托管一个用过的核燃料储存库。然而，卤水中镎（Np）的形态尚不清楚。在这项拟议的研究中，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络合物的平衡常数，（3）开发研究盐水中形态的方法。首先，Np在卤水中的形态将使用热力学数据库进行预测。其次，分别采用光谱法、因子分析法、溶剂萃取法和量子化学模拟相结合的方法，以及溶解度法和量子化学模拟相结合的方法，对Np（V）和Np（IV）的形态进行了研究。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锕系元素的尖端研究核心。这项拟议的研究将大大有助于提高对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元素化学和用过核燃料管理工程领域的高素质人才。此外，这项研究将有助于建立一个新的前沿锕系元素化学和工程在盐水环境。

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.