The extraction of f-elements from nitric acid solutions with symmetric diglycolamides in polar aliphatic fluorinated diluents was studied. The influence of diamide structure, namely of the length of alkyl substituents (C4, C6, C8) on amidic nitrogen atom, on the extraction properties was investigated. New extraction solvent on the base of N,N,N′,N′-tetrahexyl diglycolamide in formal of tetrafluorpropyl alcohol (FN-1) was proposed for selective Am (III) separation from PUREX-process raffinates.

N,O-hybrid donor ligands are promising compounds for the isolation and separation of actinides and lanthanides from process solutions of spent nuclear fuel reprocessing. Newly synthesized N,O-hybrid donor ligands – derivatives of 2,6-pyridinedicarboxylic acid were studied as extractants and membrane components for potentiometric sensors. The extraction ability of solutions of these compounds in meta-nitrobenzotrifluoride towards d- and f-elements from nitric and perchloric acid solutions was investigated. It was shown that the replacement of amide groups with ester groups reduces the extraction ability of the ligands. Switching from nitric acid to perchloric acid gives a dramatic increase in extraction capacity due to the perchlorate effect. Also, a significant increase in extraction capacity is observed when chlorinated cobalt dicarbolide is added to the organic phase: the highest distribution coefficient is observed at a 1 : 1 ratio of extractant and additive concentrations. Potentiometric membrane sensors based on the new ligands showed significant sensitivity to Cd2+. Correlations between extraction and sensing behavior of new ligands were studied.

The chemical analysis of spent nuclear fuel (SNF) reprocessing is a very challenging research field due to the high radioactivity of process streams and their complex composition. The process managing requires thorough chemical analysis to ensure safe and efficient performance. Traditional ways of chemical control of SNF reprocessing are based on sampling methods and involve long and tedious procedures, failing to provide immediate information on the process status. Recent literature suggests that potentiometric multisensor systems can be employed for on-line control. However, up to now these systems were only studied in very simple model media. This work reports on the potentiometric multisensor array applied for the first time for the simultaneous quantification of the content of actinides (uranium, plutonium, neptunium) and several other analytes (zirconium, molybdenum and nitric acid) in the complex samples obtained from the pilot extraction unit for SNF reprocessing. The same samples were also analyzed by UV-Vis spectrometry (another prospective method for on-line control) and the analytical performance of these two methods was compared using established analytical figures of merit (sensitivity and analytical sensitivity metrics) for multivariate calibration. In spite of the extremely challenging analytical task, both simple methods provide the characteristics suitable for real industrial applications.

The history of the development of fluorinated compounds as potential diluents in solvent extraction processes is described. Fluorinated diluents were first investigated in the former Soviet Union and later in the United States and Europe. Fluorinated diluents represent a class of compounds that can be used as primary diluents or as phase modifiers. They are of particular utility when extractant solubility is limited in traditional hydrocarbon diluents and a polar diluent is needed. The chemical and physical characterisitics of fluorinated diluents are provided for a broad range of compounds. Other properties such as toxidcity and resistance to radiolysis are described. Fluorinated compounds have been studied for over 40 years and have been used at industrial scale as a primary diluent for cesium and strontium extraction in Russia and as a phase modifer for an insustrial-scale cesium extraction process in the United States. The advantages and disadvantages of traditional hydrocarbon diluents are compared with chlorinated diluents, chlorinated and fluorinated diluents, and a number of different types of fluorinated diluents. Developing trends for teh use of fluorinated diluents in solvent extraction processes are discussed. This article should provide assistance to researchers investigating new or improved solvent extraction processes where traditional hydrocarbon diluents may not be appropriate.

The variety of newly synthesized diamides of dipicolinic acid(DPA)bearing methyl-and oxymethyl substituents in various positions of phenyl ring was investigated as potential ligands for liquid-liquid extraction of rare earth metal ions and as membrane active compounds in plasticized polymeric membranes of potentiometric sensors.It is found that scandium is extracted with 2,6-pyridinedicarboxylic acid diamides similarly to heavy lanthanides,while yttrium is extracted together with light group lanthanides.DPA shows high selectivity for the separation of cadmium/zinc,lead/nickel or copper/nickel pairs.The four out of six studied ligands demonstrate significant potentiometric sensitivity towards scandium,yttrium and lanthanides in 10-7-10-3 mol/L concentration range in nitric acid solutions.The trends in sensitivity values vary depending on a ligand structure and the highest values are observed for Sc3+and heavy lanthanides.According to the evaluated selectivity Sm3+is the most preferred ion,while La3+is the most discriminated.The differences in sensor behavior in rare earth metal solutions assume that such devices can be applied in sensor arrays for potentiometric analysis of lanthanide mixtures.

“Mayak” production association has convincingly demonstrated the possibility of creating a HLW partitioning scheme based on different radical phosphine oxide in heavy fluorinated or chlorinated diluents, including in the presence of tributyl phosphate. The separation system makes it possible to efficiently recover uranium, plutonium, neptunium, REE–TPE, as well as technetium from solutions (up to 2 M) in HNO3 and separate them into at least two fractions: a fraction of trivalent REE/TPE with the bulk of technetium and a fraction of polyvalent actinides.

A flowsheet for a novel CRAMEX (crown ether and amide for the extraction) process has been developed. The solvent system proposed is a combination of 0.3 M N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and 0.2 M dibenzo-21-crown-7 (DB21C7) in polar fluorinated diluents that co-extracted cesium, strontium, actinides and lanthanides. The stripping of cesium and strontium from the loaded organic phase can be carried out with diluted nitric acid solutions (< 0.1  M HNO3). A mixture of 0.5 M methylamine carbonate and 10 g/l DTPA provides stripping of actinides and lanthanides.

Developing a potentiometric sensor with required target properties is a challenging task. This work explores the potential of quantitative structure-property relationship (QSPR) modeling in the prediction of potentiometric selectivity for plasticized polymeric membrane sensors based on newly synthesized ligands. As a case study, we have addressed sensors with selectivity towards carbonate—an important topic for environmental and biomedical studies. Using the logKsel(HCO3−/Cl−) selectivity data on 40 ionophores available in literature and their substructural molecular fragments as descriptors, we have constructed a QSPR model, which has demonstrated reasonable precision in predicting selectivities for newly synthesized ligands sharing similar molecular fragments with those employed for modeling.

Developing chemical sensors with pronounced sensitivity towards lanthanides is a very important task related to the analytical control of industrial processes in nuclear industry. Various diamides of organic acids were shown to be very effective for such sensing applications when employed as ligands in plasticized polymeric membranes of potentiometric sensors. The chemical structures of some of these ligands (diamides of diglycolic acid) are very similar to those suggested in 80’s as Ca(II) ionophores that were later commercialized. We have hypothesized that commercial ionophores ETH 129 (N,N,N′,N′-tetra[cyclohexyl] diglycolic acid diamide) and ETH 5234 (N,N-dicyclohexyl-N′,N′-dioctadecyl-diglycolic diamide) originally intended for calcium detection can provide noticeable potentiometric sensitivity towards lanthanides. To confirm this hypothesis a series of PVC-plasticized sensor membranes containing ETH 129 and ETH 5234 were prepared. The sensing properties of these membranes in aqueous solutions of rare earth metals were studied and compared to earlier developed lanthanide sensors based on diamide ligands. It was found that commercial calcium ionophores indeed provide pronounced sensitivities towards lanthanides, scandium, and yttrium, while the selectivities in presence of calcium ions are in the favor of Ca(II).

Despite the fact that in the mass consciousness nuclear power is associated with increased environmental risks, this type of energy today remains one of the cleanest, most efficient and carbon neutral. Further development of nuclear energy is hampered by the problem of appropriate handling of spent nuclear fuel (SNF). A very attractive concept of the closed nuclear cycle has been developed to solve it. A real-life implementation of this concept requires the development of technological processes for the efficient separation of minor actinides from the rest of the SNF components. Recent progress in this area has been closely associated with N,O-hybrid donor ligands for liquid–liquid extraction. This work systematically reviews the available literature on the topic and provides detailed explanations on the behavior of the most perspective ligands. Notably, another important aspect of the application of N,O-hybrid donor ligands in nuclear cycle analytics through their incorporation in chemical sensors is also discussed.

Potentiometric multisensor systems were shown to be very promising tools for the quantification of numerous analytes in complex radioactive samples deriving from spent nuclear fuel reprocessing. Traditional multivariate calibration for these multisensor systems is performed with partial least squares regression—an intrinsically linear regression method that can provide suboptimal results when handling potentiometric signals from very complex multi-component samples. In this work, a thorough investigation was performed on the performance of a multisensor system in combination with non-linear multivariate regression models for the quantification of analytes in the PUREX (Plutonium–URanium EXtraction) process. The multisensor system was composed of 17 cross-sensitive potentiometric sensors with plasticized polymeric membranes containing different lipophilic ligands capable of heavy metals, lanthanides, and actinides binding. Regression algorithms such as support vector machines (SVM), random forest (RF), and kernel-regularized least squares (KRLS) were tested and compared to the traditional partial least squares (PLS) method in the simultaneous quantification of the following elements in aqueous phase samples of the PUREX process: U, La, Ce, Sm, Zr, Mo, Zn, Ru, Fe, Ca, Am, and Cm. It was shown that non-linear methods outperformed PLS for most of the analytes.

While potentiometric, plasticized membrane sensors are known as convenient, portable and inexpensive analytical instruments, their development is time- and resource-consuming, with a poorly predictable outcome. In this study, we investigated the applicability of the QSPR (quantitative structure–property relationship) method for predicting the potentiometric sensitivity of plasticized polymeric membrane sensors, using the ionophore chemical structure as model input. The QSPR model was based on the literature data on sensitivity, from previously studied, structurally similar ionophores, and it has shown reasonably good metrics in relating ionophore structures to their sensitivities towards Cu2+, Cd2+ and Pb2+. The model predictions for four newly synthesized diphenylphosphoryl acetamide ionophores were compared with real potentiometric experimental data for these ionophores, and satisfactory agreement was observed, implying the validity of the proposed approach.

There is not much known on the stability of plasticized polymeric sensor membranes against ionizing radiation. While recent studies have indicated the applicability of potentiometric sensors with such membranes for quantification of actinides and lanthanides in spent nuclear fuel reprocessing solutions, the real industrial application of such sensors will require their stability in ionizing radiation fields. The present study explores this problem and evaluates the stability of potentiometric sensitivity towards lanthanides and actinides for a variety of plasticized polymeric membranes based on different neutral ligands. We demonstrate that most of the studied sensor compositions retain their sensitivity up to 50–100 kGy of the absorbed gamma radiation dose. The higher doses lead to the gradual loss of sensitivity due to the radiolysis of ligands and a polymer membrane matrix as confirmed by electrochemical impedance and nuclear magnetic resonance studies.

This work aims to discuss quantification of rare earth metals in a complex mixture using the novel multi-ionophore approach based on potentiometric sensor arrays. Three compounds previously tested as extracting agents in reprocessing of spent nuclear fuel were applied as ionophores in polyvinyl chloride (PVC)-plasticized membranes of potentiometric sensors. Seven types of sensors containing these ionophores were prepared and assembled into a sensor array. The multi-ionophore array performance was evaluated in the analysis of Ln3+ mixtures and compared to that of conventional monoionophore sensors. It was demonstrated that a multi-ionophore array can yield RMSEP (root mean-squared error of prediction) values not exceeding 0.15 logC for quantification of individual lanthanides in binary mixtures in a concentration range 5 to 3 pLn3+.

The radiolytic stability of hydrophobic extracting compounds CyMe4-BTBP and CyMe4-BTPhen and a hydrophilic masking agent (PhSO3H)2-BTPhen, widely employed for trivalent minor actinoid and lanthanoid separation, against γ radiation was tested. Even though the solvent with a promising fluorinated diluent BK-1 provides better extraction properties compared to octan-1-ol, its radiation stability is much lower, and no extraction was observed already after an absorbed dose of 150 kGy (CyMe4-BTBP) or 200 kGy (CyMe4-BTPhen). For the (PhSO3H)2-BTPhen hydrophilic masking agent, the results showed that the rate of radiolytic degradation was significantly higher in 0.25 M HNO3 than in 0.5 M HNO3. For both the hydrophobic and hydrophilic agents, degradation was slower in the presence of both organic and aqueous phases during irradiation.

ABSTRACT New non-inflammable compounds – carbonates of fluorinated alcohols were proposed as potential diluents for tributyl phosphate (TBP). These compounds are commercially available, have high boiling point, high density, and low solubility in water solutions. Extraction of actinides from nitric acid by TBP solutions in fluorinated carbonates was studied. TBP solutions in fluorinated carbonates show lower extraction ability comparing with TBP solutions in hydrocarbon diluents. In spite of this, it is possible to extract more than 99.9% of tetra- and hexavalent actinides presented in spent nuclear fuel solutions. The advantage of proposed solvent is possibility to obtain uranium strip product with uranium concentration higher than 100 g/l.

Scandium is a rare earth element that is not very abundant on Earth, however in recent years due to the employment of scandium in various high-tech fields the interest in the analytical chemistry of this metal is growing. Currently, the methods for scandium quantification are mainly based on inductively coupled plasma atomic emission and mass-spectrometry and to the best of our knowledge no potentiometric sensors for scandium detection were reported so far. This study is devoted to the development of simple and cost-effective ion-selective sensors for quantification of Sc3+ in aqueous media. Employing the variety of lipophilic ligands suggested in liquid extraction for separation of lanthanides and actinides we synthesized a series of plasticized polymeric sensor membranes that have shown pronounced sensitivity to Sc3+ in acidic aqueous solutions, reaching in some cases super-Nernstian values around 30 mV/dec. The selectivity of the sensors was studied with respect to transition metals, lanthanides and yttrium and it was found that most of the developed sensors are selective towards scandium. The real-life applicability of the sensors was demonstrated in quantification of scandium in industrial solutions - hydrolytic sulfuric acid obtained from pigment titanium dioxide production. We believe these sensors can be considered as a promising alternative to conventional analytical methods in technological process monitoring task.

In this work, we explore the possibility of using anti-crown ether (C6HgF4)3 as a membrane-active component for potentiometric cross-sensitive sensors. Anti-crown ligands have already been employed as ionophores in plasticized polymeric membranes; however, the results of these studies are contradictory. In order to clarify the electrochemical sensitivity patterns of anti-crown-based sensors, we have studied plasticized polymeric membranes containing cation and anion-exchanging additives and various solvent-plasticizers. We explored the electrochemical sensitivity of these membranes in a wide variety of aqueous solutions of inorganic salts. Alkaline, alkaline-earth, and d-element salts with different anions were studied. It was found that the sensors based on anti-crown (C6HgF4)3 exhibit cationic sensitivity, and no considerable anionic responses were observed.

Results are presented of tests, mastering, industrial exploitation, and optimization of an integrated scheme for fractionation of liquid high-activity wastes (HAWs) produced in processing of spent nuclear fuel (SNF), which includes the extractive recovery of the Cs–Sr with the system based on chlorinated cobalt dicarbollide in a heavy fluorinated diluent and extraction from the resulting raffinates of a group of rtansplutonium and rare-earth elements by the oxalate precipitation method. This was done at Mayak Production Association in 1996–2003. A total of more than 1600 m3 of HAWs that were stored during a long time in storage facilities and contain more than 54 MCi of β- emitters. About 52 MCi of β- and also about 0.5 MCi of α-nuclides were isolated into concentrates and transferred to vitrification. The scale of activities on integrated fractionation of acid HAWs has no analogs in the world.

The quantification of plutonium in technological streams during spent nuclear fuel (SNF) reprocessing is an important practical task that has to be solved to ensure the safety of the process. Currently applied methods are tedious, time-consuming and can hardly be implemented in on-line mode. A fast and simple quantitative plutonium (IV) analysis using a potentiometric sensor array based on extracting agents is suggested in this study. The response of the set of specially designed PVC-plasticized membrane sensors can be related to plutonium content in solutions simulating real SNF-reprocessing media through multivariate regression modeling, providing 30% higher precision of plutonium quantification than optical spectroscopy.