In the advanced spent fuel wet reprocessing process, mutual separation of trivalent actinide ions (An3+) and lanthanide ions (Ln3+) is extremely challenging. The development of back-extraction separation ligands is considered to be a viable alternative to realized efficient An/Ln separation. Using density functional theory (DFT) calculations, we have studied the back-extraction behaviours and Am/Eu separation capabilities of three ethylenediamine N-heterocyclic carboxylate ligands including N, N, N’-tris (2-pyridylmethyl)-N’-(ethylacetate) ethylenediamine (HL3py), N, N, N’-tris (2-pyrazinylmethyl)-N’-(ethylacetate) ethylenediamine (HL3pz), and N, N, N’-tris (2-triazinylmethy)-N’-(ethylacetate) ethylenediamine (HL3tz). Although HL3pz is softer than HL3py, HL3py shows slightly better Am3+ selectivity over Eu3+ compared to HL3pz. This inverse relationship between ligands’ softness and their Am/Eu separation capabilities was explored through bonding nature analyses and back-extraction reactions. Though small in magnitude, Am-Nring and Eu-Nring bonds in the studied extraction complexes possess different extend of covalent component, and this difference may be the key mechanism of these back extractants for Am/Eu separation. Due to the hydrogen bonding and intermolecular interactions, the Am, Eu ions and extractants usually assemble in organic diluent forming supramolecular complexes. In this work, the thermodynamic properties of back-extraction from Am/Eu-DMDOHEMA and Am/Eu-HDEHP supramolecular species have been explored for the first time through quantum chemical calculations, which well reproduced the relative differences in selectivity Am3+ back extraction with HL3py and HL3pz, offering an explanation for the inverse relationship between ligand's softness and its Am3+ preference.

Organophosphorus ligands such as TBP, TiAP, and DMHMP have exhibited excellent performance in recovering actinides from spent fuel. In this work, the molecular geometries and properties of TBP, TiAP and DMHMP were investigated using density functional theory calculations. Furthermore, the extraction mechanism of ligands for actinides (Np(VI), Pu(IV)) was further elucidated by simulating the microstructures and extraction reactions of metal-ligand complexes. The results demonstrate that the complexation ability of the three ligands on actinide cations (NpO22+ and Pu4+) follows the order of DMHMP > TiAP > TBP. The electrostatic potential (ESP) analysis indicates that the nucleophilic ability of DMHMP is stronger than that of the other two ligands. The frontier molecular orbital analysis of the three ligands represents that DMHMP has the highest HOMO energy, suggesting that it has the strongest electron-donating capability and is more likely to bond with metal ions. The values of Wiberg bond indices (WBI) suggest that the MO bonds in DMHMP complexes have more covalency. According to the QTAIM analysis, the interactions between actinide cations and the ligands are predominantly ionic in nature. The molecular orbital analysis of the complexes shows that the M(NO3)(n)center dot 2DMHMP (MNpO22+ and Pu4+) complexes are more stable, which is supported by thermodynamic energy analysis. This work has clarified the complexing properties of actinide cations with three ligands, shedding light on the extraction mechanisms of organophosphorus ligands for actinide cations. It is anticipated to lay the theoretical foundation for the efficient recovery of critical actinide elements in spent fuel reprocessing, which will also provide innovative approaches for the design and development of related separation processes.

At present,the research on spent fuel reprocessing technology,especially the research on solvent extraction technology has been paid more and more attention.The radio-nuclides in aqueous solution were extracted with organic diluent containing extractant.This paper aims to review and discuss the extraction performance and radiation stability of phos-phorus-containing extractants,especially neutral phosphorus extractants,used in spent fuel reprocessing(solvent extraction)in the past decade.For neutral phosphine extractants,the extraction performance and radiation stability are affected by other factors such as its own structure,diluent type,etc.The decrease of the number of P—O bonds in the extractant would improve the extraction performance.The increase of alkyl chain length or the intro-duction of branched chain(such as methyl,ethyl and phenyl)can improve the radiation sta-bility.In addition,the organic phase with ionic liquid as diluent can reduce the irradiation of the organic phase.Therefore,the study of the relationship between the structure of phos-phorus-containing extractants and their extraction performance and radiation stability are conducive to select the extractant suitable for spent fuel reprocessing.It is also of great significance to select the structure with excellent extraction performance and radiation stabil-ity to guide the synthesis of new phosphorus-containing extractants.

In this paper, the feasibility of plutonium separation from the solution of irradiated neptunium target by solvent extraction with TBP was studied. The possibility of Pu(Ⅳ)-Np(Ⅳ) combination as extracted valence combination was investigated from material liquid preparation and process design. The two-step method of UDMH reduction-sodium nitrite oxidation to control the valence state of Pu(Ⅳ)-Np(Ⅳ) was studied. The results show that more than 99.9% Pu(Ⅳ) and 99.5% Np(Ⅳ) can be kept stable for more than 4 h. Based on this, an extraction process for plutonium separation from the solution of irradiated neptunium target is designed and verified by cascade experiments. According to the designed process, the yield of neptunium in 1A is 99.5%, the stripping rate of neptunium in 1B is 0.8%, and the stripping rate of plutonium is 99.9%. The stripping rate of neptunium in 1C is 99.5%. The data show that the separation of neptunium and plutonium can be realized by controlling the extracted valence combination of Pu(Ⅳ)-Np(Ⅳ) in feed, and yet the problems of long time stability of valence states and the weak extraction ability for neptunium with TBP will affect the practical application of the process.

研究了HNO 3 介质中甲基膦酸二甲庚酯（DMHMP）对Pu（Ⅳ）的萃取性能,考察了DMHMP浓度、NO - 3 浓度、HNO 3 浓度以及温度对Pu（Ⅳ）分配比的影响。确定了DMHMP萃取Pu（Ⅳ）的萃合物的组成为Pu（NO 3 ） 4 ·2DMHMP,其萃取反应方程式为:■其中Pu（Ⅳ）与NO - 3 形成中性分子,再与DMHMP结合成为中性配合物进入有机相。在实验范围内Pu（Ⅳ）分配比与DMHMP浓度的平方、NO - 3 浓度的四次方成正比,萃取过程为放热反应,反应的焓变为-34.46 kJ/mol。

以正十二烷为稀释剂,研究了甲基膦酸二甲庚酯(DMHMP)萃取剂对硝酸介质中Zr(Ⅳ)的萃取性能.从3.0 mol/L HNO3中萃取Zr(Ⅳ)的分配比与萃取剂浓度及硝酸根浓度的关系表明:萃取过程中DMHMP以中性萃取剂形式与Zr(Ⅳ)配位,萃取反应方程式主要为:Zr4+ +2DMHMP+4NO3--=Zr(NO3)4 · 2DMHM随着硝酸浓度的增大,还会生成Zr(NO3)4·2DMHMP· 2HNO3和Zr(NO3)4·2DMHMP·3HNO3.该反应为放热反应,降低温度有利于DMHMP对Zr(Ⅳ)的萃取.

采用静态平衡法测定了常压下在273.15～343.15 K时甲基膦酸二甲庚酯(DMHMP)在水和不同浓度硝酸溶液中的溶解度.实验数据表明:DMHMP在常压298.15 K条件下于水中的溶解度δ(DMHMP)=166.69 mg/L;随着温度升高,DMHMP在水中的溶解度δ逐渐增加,符合Apelblat溶解度模型;用正十二烷稀释DMHMP可以降低其在水相中的溶解度;随着硝酸浓度的增加,DMHMP在硝酸中的溶解度也随之增加.

1994年,招远市从荷兰引进M9T337苹果实生苗,半成品红富士/M9苹果苗(海关有档案记录).按照无病毒繁育标准建立苹果繁育圃1.3hm2,带动了周边县市及招远市无病毒苹果的发展.其中,招远市蚕庄镇蒋家村,栽植自根砧M9T337红富士60hm2.2010~2015年,笔者进行了红富士/M9T337精品高效栽培技术的应用研究,取得了理想效果.

Abstract A study of the electrochemical behaviors of N,N-dimethylhydroxylamine (DMHAN) and monomethyl hydrazine (MMH) in nitric acid solution on Pt electrodes were carried out by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) methods. The diffusion coefficients of DMHAN and MMH were obtained by CV. The values are found to be 0.53 × 106 cm2/s D(DMHAN) and 0.88 × 105 cm2/s D(MMH). The equilibrium potentials (+0.47 V vs. SCE for DMHAN and +0.31 V vs. SCE for MMH) were also measured using Tafel curves. Various valence states of Pu and Np in HNO3 solution containing DMHAN and MMH in the electrolytic process were investigated by an electrolytic cell using a platinum as the anode and a titanium plate as the cathode. In this procedure, MMH was first electro-oxidized on the Pt anode and Np(V) was reduced to Np(IV) on the Ti cathode. After MMH was entirely consumed, the accumulation of HNO2 (due to the electrochemical reduction of nitric acid on the Ti cathode) caused a significantly fast catalytic reaction of DMHAN with HNO3 to form HNO2. HNO2 can oxidize Pu(III) to Pu(IV) quickly. As a result, both oxidation states of Pu and Np were found to be tetravalent in the post-electrolysis solution. A convenient method to keep the post-electrolysis solution at 70 ºC was used to adjust the oxidation state of Np in it's pentavalent state while retaining the tetravalent state of Pu. This study developed an electrolytic process for the preparation of 2AF feed (the feed of Pu purification cycle) in APOR (Advanced Purex Process Based on Organic Reductants) process by electrochemically oxidizing Pu(III) and selectively adjusting the valence state of neptunium to either Np(IV) or Np(V).

Tri-isoamyl phosphate(TiAP or TAP) with tri-butyl phosphate(TBP) in physical characters,extraction ability and radiation-resist stability were compared.The results show that TiAP is a better extractant than TBP in physical properties,ability of extraction of Np(Ⅳ) and Pu(Ⅳ),and radiation-resist stability.It shows that radiation stability of TiAP is adequate for most of the process application,ability of extraction of Np(Ⅳ),Pu(Ⅳ),U(Ⅵ) and Np(Ⅵ) is good,and the extraction of fission product contaminants such as Zr,Nb,Ru,Cs is almost negligible even at very high nitric acid concentrations in the aqueous phase.TiAP may be an alternative extractant to TBP for extraction and separation of actinide elements,which is especially suitable for systems containing high-level radioactivity and/or high concentration plutonium.It is worthy of further exploration.

A novel extraction reagent,N,N,N′,N′-tetraoctyl diglycolamide(TODGA) was synthesized.The influence of various factors on the extraction of alkali earth metal from aqueous nitric acid solutions with this amide(L) and N,N-dihexyl-octamide(DHOA) is studied,including extractant concentration in n-dodecane,extracted ions concentration,acidity of aqueous phase,ionic strength of salting out agent and temperature.The composition of the extracted species and the mechanism of extraction were studied.The results suggest the extracted species to be M(NO3)2·2TODGA(org).The enthalpy change for the extraction of Ca(Ⅱ),Sr(Ⅱ) and Ba(Ⅱ) are(-38.85±1.37) kJ/mol,(-24.30±1.45) kJ/mol and(-9.14±2.01) kJ/mol,respectively.The ehtropy change are(-78.26±2.67) J/(mol·K),(-75.80±4.74) J/(mol·K) and(-51.85±6.11) J/(mol·K),and the Gibbs energy change are(-9.88±0.06) kJ/mol,(-2.08±0.06) kJ/mol and(6.06±0.22) kJ/mol at 293 K,respectively.No emulsification or third phase formation is observed during the extraction process.On the basis of the experiment results,the method of seperation and recovery of Sr from high-level liquid waste puts forward.

The kinetics of redox reaction between methylhydrazine (MMH) and Np (Ⅴ) in nitric acid media was studied by spectrophotometry. Based on results about the influence of MMH concentration and acidity on the reaction, the rate equation of that redox reaction is presented as-dc (Np (Ⅴ))/dt=kc (Np (Ⅴ)) c^0.36 (MMH) c (H(superscript +)). The rate constant is 0.004 79 (mol/L)^(-1.36)/min at 35℃. Effects of ionic strength, c (U (Ⅵ) ), and temperature were also investigated. The results show that ionic strength and c (U (Ⅵ) ) have no obvious effect on the reaction but temperature has positive effect with activation energy value of 60.43 kJ/mol. The mechanism of the redox reaction was discussed.

The reaction kinetics between dimethylhydroxylamine(DMHAN) and Np(Ⅵ) in nitric acid media was studied by spectrophotometry.By investigating the influence of DMHAN concentration and acidity on the reaction,the reaction rate equation is obtained:-dc(Np(Ⅵ))/dt=kc(Np(Ⅵ))c(DMHAN)/c0.6(H+),and the rate constant is 289.8(mol/L)-0.4/min at 25 ℃ and I=4.0 mol/kg.The effects of ionic strength,c(U(Ⅵ)),and temperature were also investigated.The results show that the ionic strength and c(U(Ⅵ)) have no obvious effects on the reaction.The reaction activation energy was found to be 53.3 kJ/mol(25 ℃) by plotting the reaction rate constant against the reciprocal of reaction temperature.The negative activation energy implies that rising temperature will accelerate the reaction.Based on the above results,the reaction mechanism was explored.

<正>在Purex流程中的共去污阶段,镎可进入高放废液,也可与铀、钚一起萃取进入有机相。因此,共去污阶段是决定镎走向的关键环节。如果1AF中的大部分镎被萃取到有机相,则可避免从高放废液中分离镎。镎被萃取到1AP后,可在铀线循环或钚线循环中得到分离或净化。为探寻使大部分镎与铀、钚共萃取的工艺条件,综合考虑进料酸度、亚硝酸浓度、铀饱和度、流比等因素的影响,采用计算机程序计算优化工艺条件,在混合澄清槽中进行了台架实验(图1)。

Considering the good solubility of 2,6-bis(5,6-di-n-propyl-1,2,4-triazin-3-yl)-pyridine(DPTP) and avoiding the third phase formation,octanol-dodecane(ODOD) with a volume fraction of 30% was selected as the diluent.The distribution ratios of Am(Ⅲ) and Eu(Ⅲ) were studied as a function of a number of parameters such as contact time,nitrate ion and the nitric acid concentration in aqueous phase,the concentration of DPTP in the organic phase.A counter-current cascade(10 mL glass tube with plug) extraction experiment was carried out with 0.04 mol/L DPTP/ODOD.In the experiments,the flow rate ratios are as following: F∶X∶S=1∶0.63∶0.25,BF∶BX =1∶1;the feed solution,Eu(Ⅲ)+Am(Ⅲ) in 1.0 mol/L HNO3 solution;scrubbing solution,1.0 mol/L HNO3 solution;stripping reagent,0.01 mol/L HNO3.The results show that the recovery of Am is 98.42%,only containing 0.1% Eu in the organic solvent,and the stripping efficiency of Am and Eu both are 99.9%,the separation factor of SFAm/Eu is 45,SFEu/Am is more than 103.

<正>在钚线工艺研究台架试验装置上完成了4次钚线工艺初步台架试验,总的钚操作量为56g,包括二次羟胺还原钚线工艺和二次DMHAN还原的先进钚线工艺试验。

Electrochemical behavior of methyl hydrazine has been studied on platinum electrode in nitric acid solution by potential cyclic sweep voltammetry.The CV results imply that the electrochemical oxidation reactions of methyl hydrazine are chemically irreversible.The kinetics parameters of electron transfer coefficient α is 0.53,diffusion coefficient D is 8.75×10-6 cm2 / s and equilibrium potential of methyl hydrazine is 0.31 V(vs SCE).

<正>乏燃料后处理Purex流程中的铀钚共去污工艺(1A)是整个化学分离过程的关键环节之一,该工艺计算机模拟计算对1A进行流程优化和安全分析具有重要意义。