Modeling and Speciation Study of Uranium(VI) and Technetium(VII) with TBP
Modeling and Speciation Study of Uranium(VI) and Technetium(VII) with TBP
复制标题
DOI：
10.1080/07366299.2020.1834979
复制
发表时间：
2020-11
影响因子：
2
通讯作者：
P. Moeyaert;T. Dumas;D. Guillaumont;P. Solari;C. Lefebvre;A. Thevenet;C. Sorel;P. Moisy
中科院分区：
文献类型：
--
作者：
P. Moeyaert;T. Dumas;D. Guillaumont;P. Solari;C. Lefebvre;A. Thevenet;C. Sorel;P. Moisy
摘要在乏核燃料中存在的裂变产物中，锝在溶剂萃取后处理操作中表现出独特的行为。事实上，这种强酸很容易分解形成含氧阴离子TcO 4 −，这可能会在PUREX工艺的提取循环中干扰铀（VI）、钚（IV）和锆（IV）。本文着重研究了TBP与铀锝配合物及其非放射性替代物。尽管有大量的分布数据可用于TBP萃取锝和锝，但共萃取络合物的结构在很大程度上仍然未知。然而，重要的是要清楚地了解萃取机理与TBP在PUREX过程中，以优化分离过程，并模拟其行为在萃取步骤。基于文献中的分布数据，建立了有机相中铀（VI）过量时TBP萃取锝的热力学模型。因此，当考虑形成（HTcO 4）（TBP）n络合物，以及混合UO 2（NO 3）（TcO 4）（HNO 3）x（TBP）n，配合物时，铀和锝的分布数据得到了很好的代表性。在配合物UO_2（NO_3）_2（HNO_3）_x（TBP）_n中，一个高锝酸根阴离子取代铀配位层中的一个硝酸根。将理论计算（密度泛函理论）支持的互补光谱技术（FT-IR和X射线吸收）与含有大量过量锝（VII）或锝（VII）的有机相相结合，可以全面表征有限的铀-锝混合物质以及铀-锝混合物质。详细的铀-锝配合物的协调提供了DFT计算和XAS测量的帮助下。
ABSTRACT Among the fission products present in the spent nuclear fuel, technetium exhibits a singular behavior in reprocessing operations performed by solvent extraction. Indeed, this strong acid readily dissociates to form the oxo-anion TcO4 − that may interfere with uranium(VI), plutonium(IV), and zirconium(IV) in the extraction cycles of the PUREX process. This paper focuses on the uranium-technetium complex with TBP and on its non-radioactive rhenium surrogate. Despite the large set of distribution data available for rhenium and technetium extraction with TBP, the structures of the co-extracted complexes remain largely unknown. However, it is important to understand clearly the extraction mechanism of technetium with TBP in the PUREX process to optimize the separation process and to model its behavior during the extraction steps. Based on distribution data available in the literature, a thermodynamic model was developed for the extraction of technetium with TBP for a large excess of uranium(VI) in organic phase. A good representation of uranium and technetium distribution data was thus obtained when considering the formation of (HTcO4)(TBP)n complexes, as well as mixed UO2(NO3)(TcO4)(HNO3)x(TBP)n, complexes. In the complex UO2(NO3)2(HNO3)x(TBP)n., one pertechnetate anion replaces one nitrate in the uranium coordination sphere. Combination of complementary spectroscopic techniques (FT-IR and X-ray absorption) supported by theoretical calculations (density functional theory) with organic phases containing a large excess of technetium(VII) or rhenium(VII) enabled full characterization of the limit mixed uranium−technetium species and also of mixed uranium-rhenium species. Details on the coordination of the uranium-technetium complex are provided with the help of DFT calculations and XAS measurements.