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Leveraging microgram-level techniques, we here present the first transplutonium bis-pentatungstate complex: NaCs8Cm(W5O18)2·14H2O (CmW5). Single crystal XRD, Raman, and fluorescence characterization show significant differences relative to analogous lanthanide compounds. The study reveals the unsuspected impact of counterions on fluorescence and vibrational modes of the curium complex and its lanthanide counterparts. [ABSTRACT FROM AUTHOR]

Leveraging microgram-level techniques, we here present the first transplutonium bis-pentatungstate complex: NaCs8Cm(W5O18)2·14H2O (CmW5). Single crystal XRD, Raman, and fluorescence characterization show significant differences relative to analogous lanthanide compounds. The study reveals the unsuspected impact of counterions on fluorescence and vibrational modes of the curium complex and its lanthanide counterparts. [ABSTRACT FROM AUTHOR]

This study validates and improves the Cm radiochronometry method developed to determine the model discharge date of nuclear spent fuels based on a three isotopes system, specifically the 244Cm/246Cm and 244Cm/245Cm ratios change since discharge time. Six spent fuel samples with continuous irradiation histories were used. After Cm separation from the matrix, the Cm isotopes were measured by accelerator mass spectrometry using one of the samples as internal standard for normalization. The mean average deviation from the known fuel discharge date improved from 3.3 ± 2.8 to 2.7 ± 2.6 yr when using spent fuel with continuous irradiation. [ABSTRACT FROM AUTHOR]

The paper presents data on selecting curium and americium simulants for the lab-scale development of a displacement complexing chromatography-based separation technique. Being eluted with the eluents based on DTPA and a mixture of DTPA and citric acid, the rare earth element holmium behaves exactly as curium and terbium—as americium. Conversely, the tracer additives of transplutonium radionuclides are a perfect option for rare earth separation studies. [ABSTRACT FROM AUTHOR]

The behavior of 88Y, 152Eu, 228Ac, 241Am, and 244Cm was studied with 2-thenoyltrifluoroacetone resin with batch uptake, kinetics and column studies. Studies were performed in acetate buffer solutions (pH ~ 2 to ~ 6) and there was high uptake of all isotopes, except 228Ac, at pH > 4.5. The kinetics of uptake were reasonable, although slower for the actinides, and sufficient for column studies. The retention of 88Y, 152Eu, and 241Am on the resin in column studies was demonstrated as well as a reasonable separation of these isotopes from 228Ac. [ABSTRACT FROM AUTHOR]

The effect of HNO3 concentration on the extraction of Eu(III), Am(III), and Cm(III) with N,N,N',N'-tetrabutyldiglycolamide was studied in 5 different diluents: nitrobenzene, toluene, chloroform, 1,2-dichloroethane, and 1,1,2,2-tetrachloroethane. The distribution coefficients of these metals as a function of the nature of the diluent in the following series of compounds was established: nitrobenzene > m-trifluoromethylnitrobenzene > mixture of n-dodecane with decanol-1 (volume ratio 90 : 10) > carbon tetrachloride > 1,2-dichloroethane > benzene > 1,1,2,2-tetrachloroethane > toluene > chloroform. The conditions for the partioning Eu(III)/Am(III) and Am(III)/Cm(III) pairs were found. An explanation was proposed for the observed increase in the separation factors of the Am(III)/Cm(III) pair with increasing concentration of nitric acid in the equilibrium aqueous phase. [ABSTRACT FROM AUTHOR]

Structural and electronic characterization of (Cp′3Cm)2(μ−4,4′−bpy) (Cp′ = trimethylsilylcyclopentadienyl, 4,4′−bpy = 4,4′−bipyridine) is reported and provides a rare example of curium−carbon bonding. Cp′3Cm displays unexpectedly low energy emission that is quenched upon coordination by 4,4′−bipyridine. Electronic structure calculations on Cp′3Cm and (Cp′3Cm)2(μ−4,4′−bpy) rule out significant differences in the emissive state, rendering 4,4′−bipyridine as the primary quenching agent. Comparisons of (Cp′3Cm)2(μ−4,4′−bpy) with its samarium and gadolinium analogues reveal atypical bonding patterns and electronic features that offer insights into bonding between carbon with f-block metal ions. Here we show the structural characterization of a curium−carbon bond, in addition to the unique electronic properties never before observed in a curium compound. Despite the distinct electronic properties of the wide variety Cm3+ compounds that have been prepared to date, no singlecrystal structural characterization of a complex containing a Cm−C bond has been reported. Here the authors report the synthesis of a Cm complex bearing trimethylsilylcyclopentadienyl and 4,4'-bipyridine ligands with a low energy emission and identify the 4,4'-bipyridine ligand as the primary quenching agent. [ABSTRACT FROM AUTHOR]

At the VNIINM (Rosatom) installation, the sorption chromatographic technique for separation of 244Сm and 241,243Аm was tested as part of the research work of the Proryv project in the field of fractionation using sulfonic cation exchange resin SPS SAC (8%)-50 (manufactured by Technosorbent LLC). The separation was carried out using a concentrate of REE–TPE oxides from the VVER-1000 spent nuclear fuel reprocessing at the Mayak Production Association. In summary, 1.39 g of Am with a purity of more than 99.9% was yielded in one cycle. The combined Cm fraction contained 36.4 mg of Am (about 2.6% of the original). The amount of Am in fractions containing also Eu or Cm did not exceed 4% of its initial amount. [ABSTRACT FROM AUTHOR]

The extraction ability and selectivity of nonmacrocyclic (8-quinolinol and 2,3-dihydroxynaphthelene) and macrocyclic (sulfur-containing calixarene derivatives) ligands toward rare earth and transplutonium elements in carbonate media was studied. Both macrocyclic and nonmacrocyclic derivatives showed moderate selectivity to americium in the Am/Eu pair (separation factor SF from 1.6 to 14 at pH > 12), and sulfur-containing calixarenes showed also high selectivity to Am in the Am/Cm pair (SF 3–8 at pH > 13). The compounds studied show promise as extractants for group recovery and separation of actinides, and also for separation of rare earth and transplutonium elements in carbonate media. [ABSTRACT FROM AUTHOR]

The conditions for the oxidation of Am(III) to Am(VI) and its reduction to Am(V) are shown, and the stability of these forms in a 0.1 M nitric acid model solution of the actinide-lanthanide fraction of high-level waste (HLW) containing isotopes of americium and curium and also praseodymium as a simulant of the behavior of fragmented lanthanides is defined. It was found that about 30% of americium in the Am(V) oxidation state of its initial content in a model solution containing a salting-out agent (ammonium nitrate) in an amount of 8 M, passes into the organic phase in one stage of extraction with a 30% solution of tributyl phosphate in Isopar-M. In this case, Cm and Pr are extracted by 80–85%. The distribution coefficient of Am was about 0.1, of Cm and Pr, about 1, and the separation factor of Am from Cm and Pr was about 10. Thus, the possibility of selective separation of americium from HLW for its subsequent transmutation in fast reactors was demonstrated. [ABSTRACT FROM AUTHOR]

We present the first report of ligand-sensitized, actinide luminescence in a lanthanide nanoparticle host. Amplified luminescence of 248Cm3+ doped in a NaGdF4 lattice is achieved through optical pumping of a surface-localized metal chelator, 3,4,3-LI(1,2-HOPO), capable of sensitizing Cm3+ excited states. The data suggest the possibility of using such materials in theranostic applications, with a ligand-sensitized actinide or radio-lanthanide serving the dual roles of a nuclear decay source for radiotherapeutics, and as a luminescent center or energy transfer conduit to another emissive metal ion, for biological imaging.

The extraction of nitric acid, trace amounts of 152Eu(III), 241Am(III), and 244Cm(III) with N,N,N',Nꞌ-tetrabutyldiglycolamide is studied in four diluents: mixture of n-dodecane with decanol-1 (volume ratio 90 : 10), benzene, carbon tetrachloride, and m-trifluoromethylnitrobenzene. For all diluents studied, the distribution coefficients of metals increase with an increase in the HNO3 concentration in the equilibrium aqueous phase. The degree of metal extraction into the extract increases in the order: Cm(III) < Am(III) < Eu(III) and decreases in the order of diluents: F-3 > DD+Dec-1 > CCl4 > PhH. The conditions for the separation of Eu(III)/Am(III) and Am(III)/Cm(III) pairs are determined. The thermal effects of extraction reactions increase on going from An(III) to Eu(III) for all the diluents considered. [ABSTRACT FROM AUTHOR]

Published data are examined, and the choice of possible imitators for studying the electrochemical partitioning of americium and curium in molten salts is substantiated. Since the direct study of americium and curium is difficult because of their high radioactivity, the corresponding lanthanides (europium and gadolinium) are proposed for the use as imitators. The structures of their external electron shells are very similar, and the oxidation levels are also similar. The electrochemical partitioning in molten salts is concluded to be most promising, since similar media make it possible to conduct the process at elevated temperatures and they are more resistant to radiation than aqueous and organic solvents. The calculation results show that AmCl3 is easily reduced to AmCl2 at elevated temperatures in chloride melts. The conventional standard potentials of Am2+/Am and Cm3+/Cm in the molten LiCl–KCl eutectic according to the data of independent authors are presented. In the melts based on the LiCl–KCl eutectic, the electrode potentials of americium and curium are found to nearly coincide; hence, the direct electrochemical partitioning of these elements is theoretically impossible. The electroreduction potentials of the Eu/Gd couple are additionally estimated more precisely. The data obtained show that the conventional standard potentials of Eu2+/Eu significantly differ from those of Gd3+/Gd, unlike the pair of Am2+/Am and Cm3+/Cm, because of which europium and gadolinium cannot serve as imitators for studying the partitioning of americium and curium. In addition, the Eu2+/Eu couple cannot be used in the LiCl–KCl melt, because the reduction potential of europium is more negative than the reduction potential of lithium. The conventional electroreduction potentials of Mg, Sc, Sr, Ba, Pr, and Nd in the LiCl–KCl melt at different temperatures are examined. The data obtained show that, among the chosen elements, the potentials of magnesium are closest to the potentials of americium and the scandium potentials are close to those of curium, which makes them more preferable for studying americium and curium partitioning in the LiCl–KCl melt. [ABSTRACT FROM AUTHOR]

The uptake of 241Am, 244Cm and 249Cf with LN resin was studied in HCl and HNO3 solutions with concentrations ranging from 0.02 to 2.5 M. There is high uptake at concentrations < 0.1 M in both acids for all three isotopes with decreasing uptake at higher concentrations and negligible extraction at ≥ 0.6 M. Californium has a higher extraction than americium and curium, which are extremely similar. Kinetics studies showed rapid uptake of all three isotopes. Column studies were performed to demonstrate the separation of 241Am and 249Cf, and a bulk separation including nine stable lanthanides along with 241Am, 249Cf, and 88Y. [ABSTRACT FROM AUTHOR]

We investigated the binary Cm-citrate system using time-resolved laser fluorescence spectroscopy (TRLFS), parallel factor analysis (PARAFAC), and quantum chemical calculations. Evidence collectively suggests the stepwise coordination and deprotonation of citrate alcohol groups in Cm-cit complexes with two bound citrate moieties upon increasing pH, which is supported by a bathochromic shift in emission spectra, an observed increase in lifetime measurements, and lower energy minima for citrate alcohol involvement versus hydrolysis of the Cm-citrate species. Our PARAFAC results agree with a 3-component model for the Cm-citrate system and offer pure component decompositions, yielding fraction species across the studied pH range that have a correlated slope = 1 as a function of pH. For the first time, evidence of ternary Ca-Cm-citrate complexes was revealed by TRLFS with increasing calcium concentration at fixed pH m. The formation of these ternary complexes was substantiated with density functional theory (DFT) calculations on simple model systems of the complexes. Shared citrate carboxylate groups between calcium and curium were proposed for all three ternary Ca-Cm-cit complexes based on DFT-determined Ca–O and Cm–O distances. Moreover, we found that the ternary complex with both alcohol groups deprotonated is most stable when it shares both two carboxylate and two alcohol groups between Ca and Cm. The presence of shared functional groups highlights the enhanced stability of these ternary complexes. Additional work is warranted to further constrain the stoichiometry, stability constants and dependence on ionic strength of these complexes for purposes of thermodynamic modeling of repository settings. [Display omitted] • Deconvolution of Cm-citrate TRLFS spectra from pH 5.0–12.5 resulted in 3 components. • DFT supports stepwise deprotonation and coordination of the citrate alcohol group. • Slope analysis revealed a linear slope = 1 for fraction species versus pH. • Ternary Ca-Cm-citrate complexes are reported for the first time. [ABSTRACT FROM AUTHOR]

In this research, curium oxide (CmO2) is studied as fuel for VVER-1200 reactor to get an attention to its energy value and possibilities. For this purpose, CmO2 is used in fuel rods or integrated burnable absorber (IBA) rods with and without UO2 and then compared with the conventional fuel assembly of VVER-1200 reactor. It is burned to 60 GWd/t by using SRAC-2006 code and JENDL-4.0 data library. From these studies, it is found that CmO2 is competent like UO2 as a fuel due to higher fission cross-section of 243Cm and 245Cm isotopes and neutron capture cross-section of 244Cm and 246Cm isotopes. As a result, when some or all of the UO2 of fuel rods or IBA rods are replaced by CmO2, we get a similar k-inf like the reference even with lower enrichment UO2 fuels. These studies show that the use of CmO2 as IBA rods is more effective than the fuel rods considering the initially loaded amount, power peaking factor (PPF), fuel temperature and void coefficient, and the quality of spent fuel. From a detailed study, 3% CmO2 with inert material ZrO2 in IBA rods are recommended for the VVER-1200 reactor assembly from the once through concept.

We report on the investigation of the atomic structure of curium ( Z = 96 ) by resonance ionization spectroscopy. Three different excited energy levels were populated from the 5 f 7 6 d 7 s 2 9 D 2 o ground state as first excitation steps. Wide-range scans were performed for the search of second excitation steps around the literature value of the ionization potential. These spectra were analyzed to identify Rydberg levels and auto-ionizing resonances. The ionization potential was consistently determined as 48330.68(16) cm - 1 through the evaluation of Rydberg convergences and the complementary approach of DC electric field ionization by evaluating the ionization threshold according to the saddle point model. The new result deviates by 6.7 cm - 1 from the literature value of 48324(2) cm - 1 by Köhler et al. [15] and is about one order of magnitude more precise. [ABSTRACT FROM AUTHOR]

An innovative-SANEX process for the selective separation of the trivalent actinides americium and curium from a simulated PUREX raffinate solution was successfully demonstrated on the laboratory scale using a 16-stage 1 cm annular centrifugal contactor setup. The solvent was composed of 0.2 mol L−1N,N,N′,N′-tetra-n-octyl-diglycolamide (TODGA) and 5% v/v 1-octanol in a kerosene diluent. Zr(IV) and Pd(II) co-extraction was prevented using trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CDTA) as a masking agent in the feed. The actinide(III) selective back-extraction was achieved using 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl]pyridine (PyTri-Diol) in 0.45 mol L−1 HNO3 as a CHON alternative to the sulfur-containing stripping agent used in a previous version of the innovative-SANEX process. The new process described in this paper showed excellent performance for the recovery of An(III). An An(III) product with a quasi-quantitative recovery of americium and curium (≥99.9%) and very good separation from fission and activation products was obtained (decontamination factors ≥4000). Only a slight contamination with Zr and Ru was observed. This test demonstrates the successful use of molecules containing only carbon, hydrogen, oxygen, and nitrogen atoms (so-called CHON molecules) for the selective separation of An(III) from a simulated PUREX raffinate solution. By avoiding sulfur- or phosphorous-containing molecules, the generation of secondary radioactive waste during process operation can be reduced drastically. [ABSTRACT FROM AUTHOR]

The properties of the potential matrix of the REE–actinide fraction of high-level radioactive waste have been studied. A sample containing 2 wt % of curium was obtained by sintering at 1400°С from a charge with the (Nd,Cm)4Ti9O24 composition. The sample was studied by the conventional XRD method. Its stability in water was determined according to the standard procedure (90°C, periodic change of solution). Contrary to the preliminary experiments with Sm (a Cm imitation) the sample consisted of perovskite-like Nd0.667TiO3 titanate and a small amount of Ti3O5 instead of the (Nd,Cm)4Ti9O24 titanate phase. The reason for the discrepancy is probably associated with the reducing conditions during the synthesis of the curium-containing sample, which led to the formation of (Nd,Cm)0.667TiO3 and Ti3O5 instead of the expected phase (Nd,Cm)4Ti9O24. From the change in the X-ray diffraction patterns over time and from the data of leaching experiments, the radiation resistance of the sample and its corrosion resistance (leaching rates of elements) in water were determined. [ABSTRACT FROM AUTHOR]

In comparison, the log I i ' SB 3 sb values for the complexation with I cis i -mTDDGA are 1.1 (for Cm(III)) and 1.8 (for Eu(III)) orders of magnitude higher than for the complexation with I trans i -mTDDGA, confirming I cis i -mTDDGA to be the stronger ligand. In contrast to the complexation of Cm(III) with I cis i - and I trans i -mTDDGA no spectroscopic evidence for a 1:2 complex with I cis i - or I trans i -mTDDGA with Eu(III) could be found. 2.2 Preparation of monophasic samples For monophasic experiments in dependence of the ligand concentration 4.5 mg I cis i -mTDDGA or 118.2 mg I trans i -mTDDGA were dissolved in 2 mL ( I cis i -mTDDGA) or 1 mL ( I trans i -mTDDGA) of 2-propanol with 5 vol% H SB 2 sb O and 1 × 10 SP -2 sp mol L SP -1 sp HClO SB 4 sb . 3 Results and discussion 3.1 Complexation of Cm(III) with cis - and trans -mTDDGA 3.1.1 cis -mTDDGA The complexation of Cm(III) with I cis i -mTDDGA was studied in 2-propanol with 5 vol% H SB 2 sb O and 1 × 10 SP -2 sp mol L SP -1 sp HClO SB 4 sb . [Extracted from the article]

A method for rapid separation of americium from complex matrices by use of two commercially available extraction chromatography resins is reported. TRU resin is capable of purifying americium/lanthanides together from Group 1, Group 2 and transition metals. TRU resin tolerated high loadings of iron, aluminium, calcium sodium and potassium. TEVA resin purified americium/lanthanides by elution with ammonium thiocyanate. Decontamination factors > 20,000 were achieved within one working day. The affinity of TEVA resin for americium, curium and lanthanides as a function of ammonium thiocyanate concentration is reported. The possibility of americium/lanthanide separations on LN resin has been explored. [ABSTRACT FROM AUTHOR]

In the ocean, complex interactions between natural and anthropogenic radionuclides, seawater, and diverse marine biota provide a unique window through which to examine ecosystem and trophic transfer mechanisms in cases of accidental dissemination. The nature of interaction between radionuclides, the marine environment, and marine species is therefore essential for better understanding transfer mechanisms from the hydrosphere to the biosphere. Although data pertaining to the rate of global transfer are often available, little is known regarding the mechanism of environmental transport and uptake of heavy radionuclides by marine species. Among marine species, sponges are immobile active filter feeders and have been identified as hyperaccumulators of several heavy metals. We have selected the Mediterranean sponge Aplysina cavernicola as a model species for this study. Actinide elements are not the only source of radioactive release in cases of civilian nuclear events; however, their physicochemical transfer mechanisms to marine species remain largely unknown. We have targeted europium(III) as a representative of the trivalent actinides such as americium or curium. To unravel biological uptake mechanisms of europium in A. cavernicola, we have combined radiometric (γ) measurements with spectroscopic (time-resolved laser-induced fluorescence spectroscopy, TRLIFS, and X-ray absorption near-edge structure, XANES) and imaging (transmission electron microscopy, TEM, and scanning transmission X-ray microscopy, STXM) techniques. We have observed that the colloids of NaEu(CO3)2·nH2O formed in seawater are taken up by A. cavernicola with no evidence that lethal dose has been reached in our working conditions. Spectroscopic results suggest that there is no change of speciation during uptake. Finally, TEM and STXM images recorded at different locations across a sponge cross section, together with differential cell separation, indicate the presence of europium particles (around 200 nm) mainly located in the skeleton and toward the outer surface of the sponge.

Trivalent actinides such as Cm(III) are able to strongly interact with microbes and especially with bacterial cell walls. However, detailed knowledge of the influence of different cell wall components is somewhat lacking. For this investigation, we studied the formation of aqueous Cm(III) complexes with cell wall components (e.g., lipopolysaccharide, peptidoglycan, and plasma membranes) using time-resolved laser-induced fluorescence spectroscopy (TRLFS). For all systems, two specific Cm(III) complexes with the biomacromolecules were observed as a function of pH. Specifically, Cm(III) was found to bind to phosphate and carboxyl groups present in the structure of the biomacromolecules. Stability constants and luminescence parameters of the specific Cm(III) complexes were determined and are presented. The pH of the surrounding aqueous solution, the plasma membrane concentration, and proteins included in the crude plasma membrane fraction were found to significantly impact the complexation of Cm(III). The Cm(III) luminescence spectra with plasma membranes, cell wall polymers, as well as Gram-negative (Sporomusa sp. MT-2.99 and Pseudomonas fluorescens) and Gram-positive (Paenibacillus sp. MT-2.2) bacteria will be explained by linear combination fitting using the investigated components.

Americium and curium, present in spent nuclear fuel, are carried forward to the high-level wastes (HLW) upon its reprocessing within the closed nuclear fuel cycle strategy. These minor actinides are required to be extracted efficiently to mitigate the long-term radiotoxicity of the HLW, which in some countries is the proposed strategy for the safe management of radioactive wastes emanating from the reprocessing of spent nuclear fuel. While both Am and Cm are co-extracted by most of extractants used for actinide partitioning and lanthanide-actinide separations, their mutual separation makes Am transmutation less complicated. In their most stable (trivalent) oxidation state, these elements are very difficult to separate. In this review, solvent extraction systems for the mutual separation of Am(III) and Cm(III) from nitric acid solutions are discussed. The extraction systems for the separation of americium directly from high-level liquid waste and from isolated mixtures of americium and curium are considered. Abbreviations: D:distribution ratio, D = C o r g C a q , where Corg – total concentration of a metal in the organic phase, Caq – total concentration of a metal in the aqueous phase; DF: decontamination factor, D F = C x , f e e d ⋅ Q f e e d C x , p r o d u c t ⋅ Q p r o d u c t , where Cx,feed, Cx,product – concentrations of an impurity in the initial feed solution and the product solution (raffinate or back-extract), Qfeed, Qproduct – flow rates of the initial feed solution and the product solution; GW×day/tHM: burn-up of nuclear fuel, where tHM – tons of heavy metal; HAC: high active concentrate; HLW: high level waste; HSAB: Hard and Soft Lewis Acids and Bases; Kex: constant of extraction, for the reaction M3+(aq) + 3NO3−(aq) +nL(org) = M(NO3)3Ln (org), Kex: [M3+][NO3−]3[L]n/[M(NO3)3Ln]; PUREX: Plutonium Uranium Reduction EXtraction; GANEX: Grouped ActiNide EXtraction; REE: rare earth element; SF: separation factor, SF = D1/D2, D1>D2; SNF: spent nuclear fuel; TRLIFS: time-resolved laser induced fluorescence spectrometry; β: constant of complex formation; List of ligands: ADAAM(EH): tetra-(2-ethylhexyldiamide-(2-ethylhexyl)-amine; BTPhen: bis-triazinylphenanthroline; (Cl-Ph)2PS2H: bis-(chlorophenyl)-dithiophosphinic acid; CMPO: Carbamoylmethylphosphine oxide DMDOHEMA: N,N'-dimethyl-N,N'-dioctyl-2-(hexyloxy)ethylmalonamide; DOODa: N,N,N',N'-tetraalkyl-3,6-dioxaoctanediamide; H2BP18C6: N,N'-bis[(6-carboxy-2-pyridyl)methyl]-1,10-diaza-18-crown-6; H4TPAEN: N,N,N',N'-tetrakis-[(6-carboxypyridin-2-yl)-ethylenediamine; HDEHP: di-(2-ethylhexyl)phosphoric acid; HEDTA: hydroxyethylethylenediaminetriacetic acid; HEH[EHP]: 2-ethylhexylphosphonic acid; NTAamide: N,N,N,N',N',N'-hexaalkylnitrilotriacetamide; PhPyPO: phenyl-pyridine phosphine oxide; TBP: tri-(n-butyl)phosphate; TEDGA: tetraethyldiglycolamide; TEHP: tri-(2-ethylhexyl) phosphate; TODGA: tetraoctyldiglicolamide; TPH: hydrogenated tetrapropylene List of terms: CHON-principle: An idea that the extractant molecule should consist only of carbon, hydrogen, oxygen and nitrogen atoms, so that the spent ligand can be easily incinerated without the formation of any solid waste. Salting out-agent: An inorganic salt with the same counter-ion as an extracted complex has.Counter-current process: A process in which the solvent and the aqueous feed streams, in contact with each other, flow in opposite directions. [ABSTRACT FROM AUTHOR]

In this work, a simple and efficient procedure for the mutual separation of trivalent americium and curium (Am(III) and Cm(III)) has been provided by extraction chromatography with the novel developed XAD-7-based BCPDTPA composite sorbent in nitric acid solution. The batch experiments and column separation studies were systematically performed. The influences of nitric acid concentration and temperature on the weight distribution coefficients and separation factors for Am(III) and Cm(III) were determined in the batch experiments. Based on the data in the batch studies, the column experiments were designed and conducted. A satisfactory separation of Am(III) and Cm(III) was accomplished in a 1.4 mL column (φ5 × 70 mm) with 0.10 mol L−1 nitric acid solution. It is noted that the partitioning process can work with single nitric acid solution without any additives. [ABSTRACT FROM AUTHOR]

Insight into the effects of radiolytic processes on the actinides is critical for advancing our understanding of their solution chemistry because the behaviour of these elements cannot be easily separated from the influence of their inherent radiation field. However, minimal information exists on the radiation-induced redox behaviour of curium (Cm), a key trivalent transuranic element present in used nuclear fuel and frequently used as an alpha radiation source. Here we present a kinetic study on the aqueous redox reactions of Cm(III) with radicals generated through the radiolysis of aqueous media. In particular, we probe reaction kinetics in nitric acid solutions that are used as the aqueous phase component of used nuclear fuel reprocessing solvent systems. Second-order rate coefficients (k) were measured for the reaction of Cm(III) with the hydrated electron (eaq−, k = (1.25 ± 0.03) × 1010 M−1 s−1), hydrogen atom (H˙, k = (5.16 ± 0.37) × 108 M−1 s−1), hydroxyl radical (˙OH, k = (1.69 ± 0.24) × 109 M−1 s−1), and nitrate radical (NO3˙, k = (4.83 ± 0.09) × 107 M−1 s−1). Furthermore, the first-ever Cm(II) absorption spectrum (300–700 nm) is also reported. These kinetic data dispel the status quo notion of Cm(III) possessing little to no redox chemistry in aqueous solution, and suggest that the resulting Cm(II) and Cm(IV) transients could exist in irradiated aqueous solutions and be available to undergo subsequent redox chemistry with other solutes. [ABSTRACT FROM AUTHOR]

In the approximation of the relativistic discrete variation method, the valence X-ray photoelectron spectrum of CmO2 was calculated, and satisfactory agreement with the structure of the experimental spectrum was found. It was shown that the structure of the spectrum is due to the electrons of the outer (from 0 to ~15 eV) and inner (from ~15 to ~35 eV) valence molecular orbitals, which leads to an increase in the covalency of the chemical bond in CmO2. The effective charge of curium in CmO2 was determined, and the contribution of various electrons to the chemical bond was evaluated. A semiempirical scheme of molecular orbitals for CmO2 was constructed. [ABSTRACT FROM AUTHOR]

In this study, drawbacks of the use of 243Am as a tracer in order to quantify curium isotopes during a complex chemical procedure were highlighted. These drawbacks were investigated through a speciation computation simulation based on the compilation of over 50 stability constants. A new curium standard was then characterized and used to quantify a wide 244Cm activities range in environmental samples. Obtained results were in excellent agreement with spiked activities and more consistent than those obtained when using 243Am as tracer. [ABSTRACT FROM AUTHOR]

In the approximation of the relativistic discrete variation method, the valence X-ray photoelectron spectrum of CmO2 was calculated, and satisfactory agreement with the structure of the experimental spectrum was found. It was shown that the structure of the spectrum is due to the electrons of the outer (from 0 to ~15 eV) and inner (from ~15 to ~35 eV) valence molecular orbitals, which leads to an increase in the covalency of the chemical bond in CmO2. The effective charge of curium in CmO2 was determined, and the contribution of various electrons to the chemical bond was evaluated. A semiempirical scheme of molecular orbitals for CmO2 was constructed. [ABSTRACT FROM AUTHOR]

The chromatographic resins DGA and LN have been used sequentially to separate curium, californium, plutonium, and various fission products (FPs) to obtain products with a pure radioisotope or a radioelement with high isotopic purity. This 2-step combination of resins has found applications in the 252Cf and 238Pu campaigns performed at Oak Ridge National Laboratory. Experiments have been carried out in glove boxes, shielded caves, and hot cells, demonstrating that these resins are adequate and maintain their performance in highly radiolytic environments. Using these resins has led to the recovery of curium highly enriched (>95%) in 248Cm, the clean separation of 251Cf for the superheavy element research, and the recovery of 147Pm from the FP stream obtained during the 238Pu production campaign while demonstrating that the raffinate post DGA is essentially free of transuranic elements. [ABSTRACT FROM AUTHOR]