Kondo entropy of δ-phase plutonium and its impact on Pu alloy phase diagrams

We present a new analysis of the heat capacity of δ-phase Pu-5 at.% Al with a fit using a single-ion Kondo term and a low-temperature Schottky anomaly in addition to the Debye and linear terms. The Kondo and Schottky terms together contribute 1.2 R to the entropy at 300?K. We show how the extra entropy could affect the alloy phase diagrams of δ-phase Pu.     

锕系元素钍到锿的5f电子效应

基于全对称群的Dirac方程, 通过计算研究锕系元素钍(Th)到锿(Es)的5f电子效应. 离域效应的定义与量子力学相合.离域能与原子体积两者的变化趋势是相反方向.对比能隙 和原子体积与原子序数的关系,两者互为源和像,是一种1—1映射.这也是与5f电子离域效应有关. 关键词： Dirac方程 锕系元素 离域效应 能隙     

Challenges to develop single-column MA(III) separation from HLLW using R-BTP type adsorbents

In order to directly separate trivalent minor actinides(MA:Am,Cm) from fission products(FP) containing rare earths(RE) in high level radioactive liquid waste(HLLW),the authors have challenged to develop a simplified MA separation process by extraction chromatography using a single column.Attention has been paid to a new type of nitrogen-donor ligands,R-BTP(2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl) pyridine,R:alkyl group) as an extractant because it shows high extraction selectivity for Am(Ⅲ) over RE(Ⅲ).It is known that the R-BTP ligands show different properties such as adsorbability and stability by having different alkyl groups.Therefore,some novel adsorbents were prepared by impregnating different types of R-BTP ligands(isohexyl-,isoheptyl-and cyheptyl-BTP) and a similar ligand to the R-BTP,ATP(2,6-bis(1-aryl-1H-tetrazol-5-yl)pyridines),into the porous silica/polymer support(SiO2-P particles).This work deals with comparison in adsorption and desorption properties of Am and some FP in HNO 3 solution onto such R-BTP type adsorbents,as well as chemical and radiolytic stability of the adsorbents.Then the possibility of a single-column separation of MA from main FP was pursued by evaluating the results of column experiments using the most promising adsorbent(isohexyl-BTP/SiO2-P) under temperature control.In addition,elution behaviors of U and Pd were also estimated.     

含氮杂环化合物萃取分离三价锕系与镧系元素

乏燃料后处理中的三价锕系和镧系元素分离是“分离-嬗变”过程的主要环节,对于建立先进核燃料循环具有重要意义。然而,三价锕系和镧系元素结构与性质非常相似,实现二者的分离一直都是分离科学研究领域的难题。溶剂萃取法是三价锕系和镧系元素分离的基本方法之一,而运用含硫、氮等软配位原子的萃取剂则是实现分离的关键。在众多的萃取剂中,含氮杂环化合物因其优良的萃取分离能力,同时符合CHON原则而利于实现废物最小化,近年来引起了广泛的研究兴趣。本文综述了国内外研究报道的典型含氮杂环类三价锕系和镧系元素分离萃取剂,包括三联吡啶、TPTZ、BTP、BTBP以及以TPEN为代表的氮杂环取代胺类萃取剂,对其分离能力、稳定性等性能进行了比较,对萃取机理以及影响其萃取能力的因素等亦进行了说明,并对萃取剂的后续设计、改进提出了参考性建议。     

Quest for Environmentally Benign Ligands for Actinide Separations: Thermodynamic,Spectroscopic, and Structural Characterization of UVI Complexes with Oxa‐Diamide and Related Ligands

Complexation of U ^VI with N,N,N′,N′‐tetramethyl‐3‐oxa‐glutaramide (TMOGA) and N,N‐dimethyl‐3‐oxa‐glutaramic acid (DMOGA; see picture) was studied in comparison with their dicarboxylate analogue, oxydiacetic acid (ODA). The stability constants, enthalpy, and entropy of complexation all decrease in the order ODA> DMOGA>TMOGA, showing that the complexation is entropy driven and the substitution of a carboxylate group with an amide group reduces the strength of complexation with U^VI due to the decrease in the entropy of complexation (see figure).

     

从高放废液中去除锕系元素的TRPO 流程发展三十年

放射性废物,尤其是高放废物的妥善处理处置是各国政府和民众非常重视的一个问题,也是影响核能可持续发展的关键因素之一。高放废液是后处理Purex流程排放出来的废液,它集中了乏燃料中95%以上的放射性,其中α放射性核素的存在决定了需要将其处置在地质处置库中与生物圈隔离10万年以上。“分离-嬗变”方法处理高放废液可以有效缩减地质处置库与生物圈隔离的时限。TRPO具有良好的物性、辐照稳定性和对三价、四价和六价锕系元素良好的萃取选择性。基于此,我国提出了从高放废液中分离锕系元素的TRPO流程。多次热验证实验和中间规模冷台架实验结果证明TRPO流程处理我国生产堆高放废液,可完全实现高放废液的非α化。TRPO流程具有我国自主知识产权,在我国生产堆高放废液和动力堆高放废液处理中都具有良好的应有前景。     

Assessment of Various Density Functional Theory Methods for Finding Accurate Structures of Actinide Complexes

Density functional theory (DFT) is a widely used computational method for predicting the physical and chemical properties of metals and organometals. As the number of electrons and orbitals in an atom increases, DFT calculations for actinide complexes become more demanding due to increased complexity. Moreover, reasonable levels of theory for calculating the structures of actinide complexes are not extensively studied. In this study, 38 calculations, based on various combinations, were performed on molecules containing two representative actinides to determine the optimal combination for predicting the geometries of actinide complexes. Among the 38 calculations, four optimal combinations were identified and compared with experimental data. The optimal combinations were applied to a more complicated and practical actinide compound, the uranyl complex (UO₂(2,2′-(1E,1′E)-(2,2-dimethylpropane-1,3-dyl)bis(azanylylidene)(CH₃OH)), for further confirmation. The corresponding optimal calculation combination provides a reasonable level of theory for accurately optimizing the structure of actinide complexes using DFT.     

The extraction of actinides by diphenyl(dibutylcarbamoylmethyl)phosphine oxide in the absence of a solvent

The possibility of changing the aggregate state of several solid mono- and bidentate neutral organophosphorus compounds in contact with various mineral acids was demonstrated. The formation of the liquid phase immiscible with water was observed. The, phase exhibits a high extraction capability with respect to actinides in various oxidation states. The diphenyl(dibutylcarbamoylmethyl)phosphine oxide-NHO₃ extraction system was studied in detail. The composition of the liquid phase was shown to the Ph₂P(O)CH₂C(O)NBu₂·HNO₃·nH₂O (n=2 or 3). The kinetics of formation of this phase and extraction of Amⁱⁱⁱ from solutions of nitric acid and its salts was studied. The organic phase exhibits redox properties, due to which some actinides change the oxidation state during extraction. The “aryl strengthening effect” was suggested to exist for extraction of Am^III in the absence of a solvent. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1739–1745, September, 1998.