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AbstractOptical spectroscopic measurements in the UV-Vis and IR ranges were performed in model solutions of aqueous and organic phases of the PUREX process for spent nuclear fuel (SNF) reprocessing. Chemometric processing of the spectral data with PLS (partial least squares) regression allowed simultaneous quantification of several key components (uranium, neptunium, plutonium, nitric acid) in these mixtures in an effective and elegant way. The content of all key components was quantitively determined with mean relative errors not exceeding 10%. It was shown that the employment of the whole spectra or their certain continuous regions for a PLS calibration enables to decrease the analytical errors compared to the use of a single wavelength in an ordinary least squares approach. The results of this research imply that the development of on-line techniques for SNF reprocessing monitoring is fully possible and can be based on optical spectroscopy methods combined with multivariate data processing techniques.

AbstractUV-Vis spectroscopic measurements were performed in model mixtures simulating solutions obtained in the course of PUREX spent nuclear fuel reprocessing. Mixtures contained constant concentrations of nitric acid and uranium with varied content of neptunium and plutonium. Spectral data were processed with classical chemometric technique — PLS regression. This approach has shown significant improvement in analytical precision of actinides determination compared to standard univariate data processing. The combination of spectroscopic measurements with chemometric data processing shows good promise for the development of on-line spectroscopic techniques for SNF reprocessing monitoring.

AbstractAmericium (Am) and europium (Eu) extraction from HNO3and HClO4media by a synergistic mixture of 2,6-bis(1-aryl-1H-tetrazol-5-yl)pyridines (ATP) with chlorinated cobalt dicarbollide (CCD) was studied by using m-nitrobenzotrifluoride, phenyltrifluoromethyl sulfone, and 1,2-dichloroethane as diluents. We examined the effects of diluents, of the aqueous phase composition and the nature of substituents in the ATP aryl ring on Am/Eu extraction efficiency and selectivity. The Am/Eu separation factor was found to be close to 100 at the optimal ratio of ATPs:CCD∼1:1. We also studied the extraction of 85Sr,137Cs and 133Ba; a PhATP-CCD mixture provided the separation of the Sr/Ba pair with a factor of 35. A high resistance of 2,6-bis-aryltetrazolyl pyridines to 6 M nitric and perchloric acids at 95 °C was demonstrated.

AbstractA number of cross-sensitive chemical sensors for determination of stable fission products (rare earth metals) were developed using different extracting agents that are known for their applicability in the reprocessing cycle of spent nuclear fuel. A novel “electronic tongue” multisensor system was suggested comprising an array of such sensors. The developed “electronic tongue” was tested in solutions simulating real reprocessing media and appeared being capable of simultaneous quantitative determination of several rare earth metals — typical constituents of spent nuclear fuel, e.g.cerium, neodymium and samarium. These results show a good promise for the development of a new analytical approach to multicomponent analysis in nuclear reprocessing industry.

AbstractThree structural isomers of diamides of dipicolinic acid (N,N′-diethyl-N,N′-ditolyl-dipicolinamide, EtTDPA) with varying position of the methyl group on the tolyl ring have been synthesized and investigated on extractability toward U(VI). The polar diluent FS-13 was used, and distribution ratios of U(VI) were studied as a function of nitric acid, ligand, and lithium nitrate concentrations. Extractability of uranium was shown to increase with increased concentration of nitrate and ligands. Infrared spectra of organic extraction phases indicate that nitric acid is coextracted as part of the neutral metal-ligand complex with U(VI) and EtTDPA through hydrogen bonding with the carbonyl group in the amide moiety.

A study of americium, uranium and europium extraction by various dialkyl-diarylamides of 2,6-pyridine-dicarboxylic (dipicolinic) acid has shown that maximum extractability is achieved by using polar fluorine-substituted diluents. Generally, the diamide extractability is found to increase with the alkyl radical length. We have demonstrated the possibility to separate Am and Eu in solutions with a nitric acid concentration of 0.5–2 mol/l. The extractability of these diamides with respect to the three metals rises with the acid concentration increase to 6 mol/l.

The extraction properties of calix[4]arenes, substituted by CH2P(O)Alk2-group on the upper rim were studied. Extraction of Am and Eu by solutions of these substituted calix[4]arenes in m-nitrobenzotrifluoride, dichloroethane, methylen chloride and p-xylene from nitric acid was performed. It was shown that extraction efficiency of calix[4]arenes from the diluted (C≤ 0.3 M) nitric acid decreases according to substituent type at phosphorus atom in the following order: butyl ≈ propyl > ethyl > methyl. Such behavior is not typical for corresponding monodentate compounds, so it was preliminary called Anomalous Alkyl Effect (AAE). In order to find out the reasons of this effect the influence of calixarene structure, changing of diluent and the distribution of extractant between water/nitric acid and organic phases were studied. We have stated that CIP-45 (with ethyl substituents at phosphorus atom) transfers into water and nitric acid (C≤ 0.3 M) from m-nitrobenzotrifluoride solution for more than 80%. CIP-45 also transfers from dichloroethane solution: about 100% transfers into water and less than 10% transfers into 0.01 M HNO3. This compound fully transfers from p-xylene even into 0.3 M HNO3solution. Less than 5% of CIP-67 (with propyl substituents at phosphorus atom) transfer from organic phase (in any of used diluent) into water/nitric acid. IR-spectroscopy investigations of CIP-45 aqueous solutions displayed that the main reason of the extraction efficiency decreasing of these substituted calix[4]arenes from the diluted nitric acid may be the formation of calixarene hydrate. This hydrate is soluble in water, but already in diluted HNO3it transforms into water insoluble solvate.

Abstract??Extraction of americium and europium from perchloric acid solutions with pyridine-2,6-dicarboxamides was studied. The solvate numbers and Am/Eu separation factors were determined.

Sorption of 241Am and 137Cs on ion-exchange resins with different functional groups from complexone solutions in liquid CO2was investigated. It was shown that more than 99% of radionuclides could be recovered from liquid CO2by using strongly acidic resins or H2C2O4·2H2O. Ion-exchange capacity of KU2-8 (analog of DOWEX-50-8) in liquid CO2was estimated.

Eight p-adamantylcalix[4]arene derivatives, bearing four CMPO-like functions [(CH2)nNHC(O)CH2- P(O)Ph2] at the wide (4a,b, n= 0, 1) or narrow (5a–cand 6a–c, n= 2–4) rims were synthesized for the first time. Studies of the extraction of americium(III) and europium(III) from 3 M HNO3solutions to organic phases (dichloromethane, m-nitro-trifluoromethylbenzene) showed: (i) The extraction ability for all the adamantylcalixarene ligands is much better than for their monomeric analogues –N-(1-adamantyl)-, N-(1-adamantylmethyl)- and N,N-(dibutyl)carbamoylmethyldiphenylphosphine oxides 7a, 7b, 8;(ii) The extraction percentage increases strongly with increasing length of the spacer for all types of ligands 4–6, and best extraction results were found for 4b(n= 1) and 5c (n= 4); (iii) The separation coefficient DAm/DEufor the investigated compounds did not exceed 2, which is close to the narrow rim CMPO calixarenes, studied earlier; (iv) Variation of the spacer length between CMPO groups attached to the 1,3- and 2,4-positions of the calixarene platform in 6did not lead to appreciably improved extractants, neither with respect to the extraction abilities (D) nor to the selectivities (DAm/DEu).

Abstract New polymeric sensors based on bidentate neutral organophosphorus compounds of varied structure with addition of chlorinated cobalt dicarbollide, which are highly sensitive to Fe3+, Y3+, La3+, Pr3+, Nd3+, and Eu3+ cations in a wide range of concentrations at pH 2, were suggested. The selectivity, detection limits, and pH-dependence of the potential of the sensors developed were studied. The influence of chlorinated cobalt dicarbollide on the electrochemical characteristics of the sensors was demonstrated.

Extraction of Am and Eu from HNO3media by phosphorylated calix-arenes in m-nitrobenzotrifluoride was studied and the following was established:• organophosphorus substituents affect the extraction properties of calix-arenes in the same manner as in the case of routine organophosphorus compounds;• calix[4]phosphine oxides and calix[4]phosphinic acid demonstrate considerable cooperative effect and extract Am and Eu about 100-times more efficient than corresponding monophosphoryl compounds;• calix[4]tetraphosphine oxides form disolvates with Am and Eu;• transfer from phosphorylated calix[4] to calix[6]arenes, i.e. increase in number of donor P=O groups, has practically no influence on extraction of Am and Eu;• only calix[4]carbamoyl extracts Am better than Eu;• as to extraction ability, calix[4]dioxide and calix[4]carbamoyl are close to conventional diphosphine dioxides and carbamoylphosphine oxides.

A series of calix[6]arenes substituted with phosphoryl functional groups were prepared by the Arbuzov reaction of hexakis(chloromethyl)calix[6]arene hexamethyl ether with isopropyl esters of trivalent phosphorus acids, followed by appropriate chemical transformations. Molecular modeling and NMR data show that phosphorylated calix[6]arenes exist in the stereochemically labile 1,2-alternateconformation. The extractive power of these compounds with respect to americium and europium was studied. Due to the cooperative binding of the metal cation with phosphoryl groups, the phosphorylated calixarenes are more effective extractants than their acylcic analogs and commercial organophosphorus extractants.

The solubility of uranium, plutonium, neptunium, and americium β-diketonates in supercritical carbon dioxide (SC-CO2) was studied. The concentration of actidine β-diketonates in SC-CO2can be as high as 10-100 g l-1. The complexes with dipivaloylmethane, trifluoroacetylacetone, and hexafluoroacetylacetone and especially their adducts with tributyl phosphate and water are the most soluble. The residues after treatment of the complexes with SC-CO2were studied by IR spectroscopy.

Solutions of hexafluoroacetylacetone and a modifier such as, e.g., pyridine in supercritical CO2allow 97-99% removal of actinides from the stainless steel surface. The deactivation efficiencies were compared for liquid and supercritical CO2. Single treatment run with solutions of HDEHP and DCH18C6 in liquid CO2removes 70-80% of transuranium elements and over 50% of strontium and cesium from the stainless steel surface. Deactivation of real contaminated radioactive samples was studied. Methods such as supercritical fluid extraction and extraction with liquid CO2are suitable for deactivation of surfaces and porous materials.

Data are reported on the use of extraction generator for preparing high-purity 99mTc from 99Mo, and the quality of the solution of 99mTc is studied. The radiolysis products of the extractant, methyl ethyl ketone (MEK), are examined; the major products are MEK dimers, and their content under operating conditions does not exceed 0.005%. A high degree of removal of both inorganic and organic impurities from the 99mTc eluate obtained from the extraction generator (Radium Institute) is achieved. This ensures a high quality of radiopharmaceuticals prepared from this 99mTc solution. The 99mTc solution prepared with the extraction generator surpasses in quality the similar solution prepared with the sorption generator. When a centrifugal extractor is used for separating 99Mo and 99mTc, the concentration of MEK in the solution of 99mTc does not exceed 0.04 mg ml-1.

A number of procedures for determining the solubility of metal complexes in supercritical carbon dioxide (SC-CO2) were compared. The solubility of adduct of uranyl trifuoroacetylacetonate with pyridine at a pressure of 300 atm and a temperture of 60°C exceeds 100 g l-1(26 mg of U per 1 ml of SC-CO2). Partial degradation of the adduct under these conditions was observed.

This work presents results of studying the extraction of dry actinide salts and oxides by complexone solutions in carbon dioxide. The conditions for efficient removal of actinide salts and oxides from solid surfaces were determined and the solubilities of different actinide complexes were compared. It was shown that the “solubility” of actinide complexes, as a rule, increases in the following order: acetylacetone ≈ divivaloylmethane ≈ thenoyltrifluoroacetone < trifluoroacetylacetone ≈ hexafluoroacetylacetone; as to additional ligands, this order is as follows: water < pyridine < tributylphosphate. The exception is provided by hydrated actinide complexes with hexafluoroacetylacetone (HFA) and trifluoroacetylacetone (TFA). The “solubilities” of similar complexes of uranium(VI), plutonium(IV), europium(III) and americium(III) differ insignificantly from each other. The “solubility” of corresponding neptunium(VI) complexes is much lower..

Structural analyses of uranyl complexes with isomers of N,N'-diethyl-N,N'-ditolyl-dipicolinamide were carried out using IR spectroscopy and single crystal x-ray diffraction. From these analyses it was determined that complexation takes place through coordination with the carbonyl and pyridine nitrogen moieties. The uranium-oxygen and uranium-nitrogen bond distances for Et(p)TDPA are U(1)-O(1): 2.394(3), U(1)-O(2): 2.460(3), U(1)-N(1): 2.661(3) and for Et(o)TDPA U(1)-O(1): 2.415(5), U(1)-O(2): 2.432(4), and U(1)-N(1): 2.647(5).