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The experimental reaction and decay studies producing nuclei in the A=230 mass chain have been reviewed. Data on elements from radon (Z=86) to americium (Z=95) are included, and level and decay schemes are presented for these nuclides. This work supersedes the previous evaluation for this mass chain (2012Br12). [ABSTRACT FROM AUTHOR]

Solvent extraction of Zr(IV) in an undiluted phosphonium based ionic liquid (IL) and its selective separation from Ln(III) and An(III) has been investigated in the present study. Eu(III)/Am(III) were chosen as the representative Ln(III)/An(III). Tri(hexyl)tetradecylphosphonium nitrate ([P66614][NO3]) was chosen as IL phase and the feed phase was nitric acid containing the target metal ions. The extraction process was accomplished at different experimental parameters such as the concentration of initial nitric acid, initial feed metal concentration and equilibration time to explore the extractability of the proposed IL towards Zr(IV). The efficient extraction of Zr(IV) without any external ligand in IL phase and negligible extraction of Eu(III)/Am(III) were distinctly discerned leading to noteworthy separation factors for Zr(IV). The loading experiment revealed a noticeable growth of equilibrium concentrations of Zr(IV) in IL phase while that of Eu(III) was very less irrespective of the initial feed concentration. The association of two IL moieties in the complex formation process has been inferred. Nitrate ion was found to be superior as IL anion in terms of metal loading in comparison to other anions. Thermodynamics of extraction and the stripping of the loaded Zr(IV) from IL phase using a suitable stripping solution have also been investigated. [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 present study, a zinc oxide (ZnO) thin films samples prepared using a Chemical bath deposition (CBD). On a glass base where the effect of irradiation with alpha particles on the optical properties of zinc oxide thin films prepared at a concentration of (0.3M) was studied. Irradiation was used from a alpha particle emitted from Americium (Am241) source,with average energy (5.486)MeV. The optical properties of ZnO films measured (200- 800nm) using a UV-Vis spectrophotometer.It was to study the relationship of absorbance as a function of photon energy for ZnO thin films.The energy gap for direct transition at standard was also calculated (2.49eV), while at irradiation of 20 min and 80 min, it was (2.37,2.29) eV, respectively. The energy band gap for indirect transfer was also calculated for the standard sample (3.26eV), while irradiation time at (20 and 80) min were (3.20,3.15) eV, respectively.The results for the research have confirmed that the direct and indirect energy gaps decrease with irradiation time when increases the time. The CBD method is used to obtain to ZnO nanotubes, which can be employed as photodetectors. [ABSTRACT FROM AUTHOR]

The Am N4,5 (4d3/2 and 4d5/2) and Am O4,5 (5d3/2 and 5d5/2) x-ray absorption spectroscopy (XAS) of americium sesquioxide (Am2O3) and americium dioxide (AmO2) has been evaluated with FEFF, a Green's function–based, multiple scattering code. Taking guidance from the intermediate coupling model (ICM), applicable to local and nonmagnetized samples, it is possible to completely reconstruct the experimental results for the N4,5 spectra, including the observed differences between the Am2O3 and the AmO2 cases. Although complicated by a more asymmetric line shape and difficult background variations, the FEFF analysis confirms the absence of core hole angular momentum coupling in Am O4,5 spectroscopy. [ABSTRACT FROM AUTHOR]

We studied the alpha decay half-life of Americium isotopes (Z = 9 5) with mass numbers ranging from 223 to 243. Our investigation employed the Coulomb and proximity potential model (CPPM), in addition to alternative analytical and semiempirical formulas. The calculations took into account both experimental and theoretical Q-values, as well as the total alpha kinetic energy. We analyzed the behavior of the hindrance factor concerning changes in the mass numbers of parent nuclei within the range of 223–243, and also examined the impact of magic numbers associated with closed shells. To evaluate the accuracy of our findings, we utilized the SemFIS, UNIV, and Royer formulas to make predictions, which were then compared to the existing experimental data. [ABSTRACT FROM AUTHOR]

The content of 237Np, 239,240Pu, and 241Am in seawater, suspended matter, and bottom sediment cores of the Ussuri and Amur Bays, sampled in July 2021 and August 2022, was analyzed. The activity concentrations of 237Np, 239,240Pu, and 241Am in the water of Peter the Great Bay were determined for the first time and were found to be equal to (19–105) × 10–3, 2.0–5.3, and 24.1–33.5 mBq/m3, respectively. The activity concentrations as well as the 239Pu/240Pu isotope ratio (⁓0.18) in the bottom sediments definitely indicate that global fallout is the main source of plutonium in the investigated territory. The sedimentation rates were determined for the Amur Bay (in the Razdolnaya River estuary), 0.9 mm/year, and for the Ussuri Bay, 4.1 mm/year. Actinide transfer coefficients were determined for Peter the Great Bay in the system dissolved forms (including colloids)–suspended matter–bottom sediment. [ABSTRACT FROM AUTHOR]

The hydrolysis mechanism of americium was calculated using density functional theory, and the detailed microscopic reaction mechanism was obtained. The results show that americium reacts with water along the octet state to produce oxides and H2, and that this reaction is exothermic. The interaction between Am and O atoms gradually changes from initially electrostatic interaction to covalent interaction, and continues to strengthen. During the reaction process, Am atoms always lose electrons, the 5f orbital is obviously involved, and there is df orbital hybridization. This study provides the necessary theoretical data support for the theoretical and experimental study of the actinide system. [ABSTRACT FROM AUTHOR]

Relevance. The fact that the literature does not contain any data not only on crystallization coefficients, but also on the nature of the co-precipitation of americium (III) with calcium oxalate. The co-precipitation reaction of americium with calcium oxalate is used to concentrate trace amounts of americium due to calcium oxalate low solubility and adsorption capacity. In this relation, the study of co-precipitation of trace amounts of americium with calcium oxalate, as well as the study of the isolation of trace amounts of americium using a calcium carrier and its subsequent separation from the carrier, is of unconditional interest. Aim. Investigation of americium co-precipitation with the solid sorbent – calcium oxalate, description of the equilibrium of the sorption isotherm using Langmuir and Freundlich models. Methods. When studying the establishment of co-precipitation of americium with a carrier – calcium oxalate, the qualification of the chemical reagents used met the requirements of the grade not lower than r.g. The isotope americium-241 was used in the work, the composition of the solid phase of the carrier – calcium oxalate – corresponded to the formula CaC2O4·H2O. The concentration of americium (III) cations in the initial solution and in the filtrate was determined by gamma-spectrometric method using the SCS-07P spectrometric complex, the amount of calcium – by complexometric titration with murexide as an indicator, and the concentration of oxalate ion – by permanganatometric method. Results. It was found that the co-precipitation of americium (III) nitrate solutions with calcium oxalate is largely due to adsorption of the micro-component – americium (III) – on the surface of the existing or newly formed precipitate of the macro-component calcium oxalate. It is determined that the Langmuir equation model adequately describes sorption, since the processing of experimental data by the least squares method showed that in coordinates C/A=f(C) the sorption isotherm is described by the equation of a straight line with a high correlation coefficient of more than 0.95.

We report an investigation of the effect of a low Am impurity content on bulk and point defect properties of mixed actinide oxide (U,Pu)O 2. Using the generalized gradient approximation, (GGA + U) we study U 0.75 − z P u 0.25 A mz O 2 with z = 3 and 6%. Several of its bulk properties have never been reported in the literature or are poorly known. The Hubbard term U is used to take into account the strong correlation effects related to the actinide 5f electrons. We find an electronic charge transfer between uranium and americium cations in the bulk crystal. Am(+IV) cations tend to easily reduce to Am(+III), and this reduction of Am(+IV) is compensated by the oxidation of U(+IV) to U(+V) in stoichiometric compounds. In turn, oxygen hypostoichiometry is accommodated by the reduction of U(+V) cations [which result from the presence of Am (+III) cations] before any reduction of the Pu cations. Furthermore, we show that Am induces a significant increase in the mixing enthalpy as well as a decrease in the lattice parameter of the (U,Pu)O 2 solid solution, which is in agreement with early experimental studies. Finally, we show that americium facilitates the formation of oxygen vacancies in (U,Am)O 2 compared to UO 2 , whereas it induces an increase in the formation energy of oxygen vacancies in (U,Pu,Am)O 2 compared to (U,Pu)O 2. [ABSTRACT FROM AUTHOR]

To examine the scope of the abnormal aryl strengthening effect (an increase in the extraction of metal ions when an aromatic substituent is introduced into the amide group) on f-metal extraction, a series of tetradentate diamide-type extragents bearing electron-withdrawing pyridine rings in amide moieties of the molecules were tested. The solvent extraction of Am(III)/Eu(III) pairs was investigated under various conditions, the solution chemistry of the lanthanide-extragents systems was studied, and the bonding constants were calculated for complexes of Eu(III) and Tb(III) ions with diamides. The photophysical properties of chemically synthesized ligand/metal (LM) complexes with various LM compositions were additionally studied in depth. The replacement of a phenyl ring by a pyridine one led to a critical reduction in metal affinity, showing the major contribution of electronic nature to the abnormal aryl strengthening effect. However, the pyridine group in the amide side chain provided additional coordination positions for metal ion binding; corresponding complexes with LM2 composition were detected in the system and their stability was calculated. Due to the low stability of the corresponding LM2 complexes, chemical synthesis of the complexes led to the formation of only one metal-containing species with LM composition. The luminescence spectra of europium and terbium complexes of the LM composition were studied. Differences were discovered in the luminescence excitation spectra of europium and terbium complexes with the same ligand. The luminescence quantum yields and luminescence lifetimes of solutions of europium and terbium complexes were determined. [ABSTRACT FROM AUTHOR]

The electronic properties in particular the occupation number of 5f electrons and the valence state of Am ions in americium trichloride (AmCl3) are studied by using density functional theory (DFT) merged with dynamical mean‐field theory (DMFT). We find that j = 5/2, j = 7/2 manifolds both are in the insulating regimes, resulting in the semiconducting band gap of about 0.837 eV, together with the weak Am 5f‐conduction electrons hybridization and the localized 5f‐derived spectra feature in the vicinity of the Fermi level. The weighted summation for the occupation probabilities of 5fn (n = 3–7) atomic configurations suggests that 5f electrons have the inter‐configuration fluctuation with an average occupation number of 5f electrons n5f ~ 5.182, corresponding to the valence state of Am3.818+ in AmCl3. The 5fn‐mixing‐driven inter‐configuration fluctuation might originate from the complicated quantum mechanics processes such as the dual nature of 5f electrons and the flexible electronic configuration of Am ions. Finally, the so‐called quasiparticle band structure is also predicted. [ABSTRACT FROM AUTHOR]

A major challenge in modelling the decorporation of actinides (An), such as americium (Am), with DTPA (diethylenetriaminepentaacetic acid) is the fact that standard biokinetic models become inadequate for assessing radionuclide intake and estimating the resulting dose, as DTPA perturbs the regular biokinetics of the radionuclide. At present, most attempts existing in the literature are empirical and developed mainly for the interpretation of one or a limited number of specific incorporation cases. Recently, several approaches have been presented with the aim of developing a generic model, one of which reported the unperturbed biokinetics of plutonium (Pu), the chelation process and the behaviour of the chelated compound An–DTPA with a single model structure. The aim of the approach described in this present work is the development of a generic model that is able to describe the biokinetics of Am, DTPA and the chelate Am–DTPA simultaneously. Since accidental intakes in humans present many unknowns and large uncertainties, data from controlled studies in animals were used. In these studies, different amounts of DTPA were administered at different times after contamination with known quantities of Am. To account for the enhancement of faecal excretion and reduction in liver retention, DTPA is assumed to chelate Am not only in extracellular fluids, but also in hepatocytes. A good agreement was found between the predictions of the proposed model and the experimental results for urinary and faecal excretion and accumulation and retention in the liver. However, the decorporation from the skeletal compartment could not be reproduced satisfactorily under these simple assumptions. [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]

The main approaches to americium transmutation in BN-1200M are considered: homogeneous transmutation in the core and heterogeneous transmutation with a moderator in the radial blanket. It is stated that the main limiting factor of transmutation is the residual heat release of the unloaded FAs. Within the design constraints, the annual transmutation rates are approximately the same in both cases. It is proposed to combine the advantages of both transmutational methods so as to ensure the homogeneous transmutation of americium in the core at the level of an equilibrium content and the heterogeneous transmutation of external americium in the radial blanket. On the basis of a simplified economic model, a comparison of various approaches was made and the corresponding technical and economic estimates were given. [ABSTRACT FROM AUTHOR]

The separation of americium during the fractionation of a highly active raffinate obtained in the extraction processing of spent nuclear fuel represents an urgent task of the contemporary nuclear fuel cycle. The article discusses new approaches to this task. It is shown that a sodium bismuthate powder (NaBiO3), upon contact with a solution of Am (III) and Cm (III), oxidizes Am (III) to Am (VI) and sorbs actinides. The addition of a (NH4)2CO3 solution results in a content of up to 91% of americium and about 2% of curium in the solution after desorption. The behavior of americium and curium in acidic and alkaline solutions of potassium hexacyanoferrate (III) was studied. In acidic solutions of HNO3, americium and curium are precipitated, while praseodymium, comprising a lanthanide simulator, remains quantified in the supernatant. In alkaline solutions of potassium hexacyanoferrate (III), ~50% of Am (III) is shown to oxidize to Am (V). The obtained results can be used as a basis for a new technology of separating americium from curium and lanthanides for the purposes of americium transmutation. [ABSTRACT FROM AUTHOR]

The extraction properties of a series of diamides of 2,2-bipyridine-6,6-dicarboxylic acids with respect to americium, curium, neptunium, thorium, light lanthanides and a series of d-elements present in solutions of highly radioactive wastes have been studied in this work. It has been shown that the extraction properties of diamides are determined not only by the structure of the heterocyclic framework, but also by the nature of substituents in positions remote from oxygen centers. The influence of substituents in a series of extractants is determined by differences in their electronic nature, and also depends on their volume and position. In the work, effective and selective extractants were found for the separation of the Am/Eu pair (SF up to 27), and fundamental patterns were revealed between the structure of the extractant and the efficiency of extracting metal ions. [ABSTRACT FROM AUTHOR]

We present a combined TEVA-DGA chromatography chemistry to purify single-element fractions of Pu, Am, and Np from bulk (mg-level) U materials. Plutonium and Np are first sorbed onto TEVA resin using a 4 + redox adjustment with a hydroxylamine hydrochloride and sodium nitrite treatment, with U + Am eluting directly onto DGA resin. Americium is then purified from U on DGA using 0.1 M HNO3 as a U eluent. A subsequent TEVA column is used to separate Pu from Np using hydrogen peroxide to oxidize Np into the 5 + oxidation state for elution through TEVA. Our presented TEVA-DGA method is able to produce high-purity, single-element fractions of Pu (90% recovery), Am (98% recovery), and Np (62% recovery) from mg-levels of U, and does so in three days of column chemistry. [ABSTRACT FROM AUTHOR]

The uptake behavior of 88Y, 140Ba, 140La, 141Ce, 152Eu, 228Ac, and 241Am was studied with batch uptake, kinetics and column studies in a synergistic extraction system with Pb resin and 2-thenoyltrifluoroacetone in acetate-ethanol solutions. The k′ values are very high (> 10,000) at near neutral pH (~ 5 to 6) for all of the radioisotopes studied. The kinetics are reasonably fast for column separations, though the uptake rate is dependent on the concentration of 2-thenoyltrifluoroacetone. Column studies were performed to demonstrate the separation of the trivalent actinides and lanthanides from barium and common fission products (99Mo, 103Ru). [ABSTRACT FROM AUTHOR]

We report the structural, vibrational, and optical properties of americium formate (Am(CHO2)3) crystals synthesized via the in situ hydrolysis of dimethylformamide (DMF). The coordination polymer features Am3+ ions linked by formate ligands into a three‐dimensional network that is isomorphous to several lanthanide analogs, (e. g., Eu3+, Nd3+, Tb3+). Structure determination revealed a nine‐coordinate Am3+ metal center that features a unique local C3v symmetry. The metal–ligand bonding interactions were investigated by vibrational spectroscopy, natural localized molecular orbital calculations, and the quantum theory of atoms in molecules. The results paint a predominantly ionic bond picture and suggest the metal‐oxygen bonds increase in strength from Nd−O

The electronic structure and the chemical state in Am binary oxides and Am-doped UO 2 were studied by means of X-ray absorption spectroscopy at shallow Am core (4d and 5d) edges. In particular, the Am 5f states were probed and the nature of their bonding to the oxygen states was analyzed. The interpretation of the experimental data was supported by the Anderson impurity model (AIM) calculations which took into account the full multiplet structure due to the interaction between 5f electrons as well as the interaction with the core hole. The sensitivity of the branching ratio of the Am 4 d 3 / 2 and 4 d 5 / 2 X-ray absorption lines to the chemical state of Am was shown using Am binary oxides as reference systems. The observed ratio for Am-doped UO 2 suggests that at least at low Am concentrations, americium is in the Am(III) state in the UO 2 lattice. To confirm the validity of the applied AIM approach, the analysis of the Am 4f X-ray photoelectron spectra of AmO 2 and Am 2 O 3 was also performed which revealed a good agreement between experiment and calculations. As a whole, AmO 2 can be classified as the charge-transfer compound with the 5f occupancy ( n f ) equal to 5.73 electrons, while Am 2 O 3 is rather a Mott–Hubbard system with n f = 6.05. [ABSTRACT FROM AUTHOR]

In the present work, an ion exchange-based radionuclides removal method for the treatment of radioactive laboratory organic liquid waste was developed. The removal of radionuclides was accomplished with the combined action of an in-house developed chelating type polystyrene based weakly acidic cation exchange resin and oxalic acid complexant. The efficacy of the method was investigated based on the results of gamma spectrometry, liquid scintillation counting and alpha spectrometry. The radioactive organic liquid waste treatment was demonstrated finally through column mode of separation method for nearly 1 Litre of the waste. [ABSTRACT FROM AUTHOR]

We present an automated separation method to simultaneously isolate short-lived activation products 242g, 240Am, 237U, 72Ga from fresh fission products prior to gamma spectrometric analysis. On the basis of multi-column chromatographic units (HDEHP resin, TBP resin, DGA resin, TEVA resin, Al2O3, activated carbon) assembly, smart media compatibility between adjacent columns, chromatographic conditions optimization and process automation design, a modularized and streamline separation procedure was developed. The established method allows better recoveries of 93%, 91% and 97% for americium, uranium and gallium separately and excellent decontamination factors of more than 105 for fission products even for large volume of samples. Because of highly efficient removal of interferents, this method coupled with well-type high-purity germanium (HPGe) gamma spectrometers achieved highly sensitive and selective analysis of activation products in spiked complicated matrix samples. [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]

We demonstrate rapid isotopic analysis of trace U, Pu, and Am in solid basalt matrices using resonance ionization mass spectrometry (RIMS). The samples were intended to mimic post-detonation debris from a nuclear explosion, in which material from the device is intimately mixed with entrained material from the environment. Complete isotopic analysis of materials containing ppm to ppb levels of the actinides was done without separating them from the host matrix, and consumed <100 ng of sample. Measured isotopic compositions of U, Pu, and Am were accurate to ≤10% for most isotope ratios except 238Pu, which was compromised by low concentration and excesses of 238U up to 34 000 : 1. A new method called "blinking" that takes advantage of the singular ability of RIMS to quantify backgrounds from all sources rapidly and accurately was developed for the analysis of 238Pu. Using the blinking method we accurately measured the 238Pu/239Pu ratio on a sample containing 1.4 × 106 atoms of 238Pu at a concentration of 0.1 ppb in the host material. [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]

Luffa cylindrica biomass was converted to biochar and the removal of 241Am by pristine and oxidized biochar fibers was investigated in laboratory and environmental water samples. This species has the added advantage of a unique microsponge structure that is beneficial for the production of porous adsorbents. The main purpose of this study was to valorize this biomass to produce an efficient adsorbent and investigate its performance in radionuclide-contaminated waters. Following the preparation of Am3+ solutions at a concentration of 10−12 mol/L, the adsorption efficiency (Kd) was determined as a function of pH, adsorbent mass, ionic strength, temperature, and type of aqueous solution by batch experiments. At the optimum adsorbent dose of 0.1 g and pH value of 4, a log10Kd value of 4.2 was achieved by the oxidized biochar sample. The effect of temperature and ionic strength indicated that adsorption is an endothermic and entropy-driven process (ΔH° = −512 kJ mol−1 and ΔS° = −1.2 J K−1 mol−1) leading to the formation of inner-sphere complexes. The adsorption kinetics were relatively slow (24 h equilibrium time) due to the slow diffusion of the radionuclide to the biochar surface and fitted well to the pseudo-first-order kinetic model. Oxidized biochar performed better compared to the unmodified sample and overall appears to be an efficient adsorbent for the treatment of 241Am-contaminated waters, even at ultra-trace concentrations. [ABSTRACT FROM AUTHOR]

The extraction of Am3+ and Eu3+ with 6,6'-bis(5-alkyl-1H-pyrazol-3-yl)-2,2'-bipyridine (BPzBPy, alkyl = i-Bu, n-Bu, n-Oct) from HNO3 medium and the complexation of BPzBPy with Eu3+ were investigated. By using meta-nitrobenzotrifluoride (F-3) as a diluent, iBu-BPzBPy ligand in combination with 2-bromohexanoic acid was able to extract Am3+ over Eu3+ with the nature of significantly high efficiency, relatively fast extraction kinetics, and easy stripping. Slope analysis showed the formation of a 1:2 metal/ligand extraction species. The analyses of electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared (FT-IR) and time-resolved laser fluorescence spectrum (TRLFS) revealed that the composition of the extracted complex was [Eu(H2O)L2]A3 (L = ligand; HA = 2-bromohexanoic acid). The complexation of iBu-BPzBPy ligand with Eu3+ was an enthalpy-driven spontaneous, exothermic, and entropy-decreasing process. Besides, the complex stability constants were also obtained via UV–vis spectrophotometric titration. Combining the results of solvent extraction and complexation studies, a cation exchange extraction model was also proposed. [ABSTRACT FROM AUTHOR]

The "Chernobyl nuclear disaster" released huge amounts of radionuclides, which are still detectable in plants and sediments today. Bryophytes (mosses) are primitive land plants lacking roots and protective cuticles and therefore readily accumulate multiple contaminants, including metals and radionuclides. This study quantifies 137Cs and 241Am in moss samples from the cooling pond of the power plant, the surrounding woodland and the city of Prypiat. Activity concentrations of up to 297 Bq/g (137Cs) and 0.43 Bq/g (241Am) were found. 137Cs contents were significantly higher at the cooling pond, where 241Am was not detectable. Distance to the damaged reactor, amount of original fallout, presence of vascular tissue in the stem or taxonomy were of little importance. Mosses seem to absorb radionuclides rather indiscriminately, if available. More than 30 years after the disaster, 137Cs was washed out from the very top layer of the soil, where it is no more accessible for rootless mosses but possibly for higher plants. On the other hand, 137Cs still remains solved and accessible in the cooling pond. However, 241Am remained adsorbed to the topsoil, thus accessible to terrestrial mosses, but precipitated in the sapropel of the cooling pond. [ABSTRACT FROM AUTHOR]

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]

The behavior of uranium, americium, and plutonium compounds contained in radioactive graphite during its heating in a mixture of water vapor and oxygen was studied by thermodynamic simulation, which was carried out using the TERRA program at temperatures from 373 to 3073 K to determine possible compounds of radionuclides (U, Am, Pu) during the disposal of radioactive graphite by heating it in a mixture of water vapor and oxygen. Thermodynamic simulation has shown that uranium, plutonium, and americium, which are present in radioactive graphite in the form of impurities during heating in a water vapor–oxygen mixture, when certain temperatures are reached, pass into the gas phase. The main list of reactions is selected and equilibrium constants are derived for the combustion of radioactive graphite in a mixture of water vapor and oxygen. [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]

To examine the scope of the abnormal aryl strengthening effect (an increase in the extraction of metal ions when an aromatic substituent is introduced into the amide group) on f-metal extraction, a series of tetradentate diamide-type extragents bearing electron-withdrawing pyridine rings in amide moieties of the molecules were tested. The solvent extraction of Am(III)/Eu(III) pairs was investigated under various conditions, the solution chemistry of the lanthanide-extragents systems was studied, and the bonding constants were calculated for complexes of Eu(III) and Tb(III) ions with diamides. The photophysical properties of chemically synthesized ligand/metal (LM) complexes with various LM compositions were additionally studied in depth. The replacement of a phenyl ring by a pyridine one led to a critical reduction in metal affinity, showing the major contribution of electronic nature to the abnormal aryl strengthening effect. However, the pyridine group in the amide side chain provided additional coordination positions for metal ion binding; corresponding complexes with LM2 composition were detected in the system and their stability was calculated. Due to the low stability of the corresponding LM2 complexes, chemical synthesis of the complexes led to the formation of only one metal-containing species with LM composition. The luminescence spectra of europium and terbium complexes of the LM composition were studied. Differences were discovered in the luminescence excitation spectra of europium and terbium complexes with the same ligand. The luminescence quantum yields and luminescence lifetimes of solutions of europium and terbium complexes were determined.

Hybrid donor extractants are a promising class of compounds for the separation of trivalent actinides and lanthanides. In this paper, we present a new ligand from the bipyridyl-dicarboxylic acid diamide family—N,N'-diethyl-N,N'-bis(2,4,5-trimethylphenyl)-[2,2'-bipyridine]-6,6'-dicarboxamide. The synthesis of N-ethyl-2,4,5-trimethylaniline from pseudocumene by selective acetylation is presented. The target ligand was obtained using this aminylene. Chemical synthesis of its complexes with Ln(NO3)3 and their spectroscopic analysis showed that the structure of the complexes is near to the corresponding structures of well-known di-methylated dianilides. A series of studies on the photophysical, complexing, and extraction properties of this ligand and its complexes were carried out. It was shown that the extraction system based on this ligand can selectively isolate americium from the solution of high-level waste imitator. [ABSTRACT FROM AUTHOR]

The sorption properties of mineral phases that constitute the rocks of the Yeniseysky area of the Nizhnekansky granitoid massif toward Np, Pu, Am, Sr, and Cs were studied under conditions of underground radioactive waste disposal. As a result of sorption experiments, sorption kinetic curves were obtained, and the distribution coefficients (Kd) of radionuclides on mineral phases were determined. The resulting data made it possible to evaluate the differences in the sorption properties of minerals towards the studied radionuclides. For each radionuclide, with the exception of americium, it was possible to establish the most effective mineral phases in terms of sorption: for Np(V)—hydroxyapatite and calcite, for Pu(V)—hydroxyapatite and magnetite, for Sr(II)—biotite and hydroxyapatite, for Cs(I)—biotite and muscovite. Americium was sorbed quantitatively on all mineral phases, except for biotite and quartz. [ABSTRACT FROM AUTHOR]

Camphor-bistriazinyl pyridine (bis-2,6-(5,6,7,8-tetrahydro-5,9,9-trimethyl-5,8-methano-1,2,4-benzotriazin-3-yl) pyridine (CA-BTP)) was synthesized and used to prepare two different resins for extraction chromatography studies. CA-BTP/XAD-7 resin was prepared by the direct sorption of the extractant CA-BTP onto the inert XAD-7 support. In contrast, CA-BTP-Oct/XAD-7 resin was prepared such that a polar diluent 1-octanol was incorporated along with the extractant CA-BTP into the resin beads. The extraction performance of both these resins was investigated in batch studies to separate Am(III) from Eu(III) in acidic nitrate solutions. Comparing the results obtained for both the resins indicated that CA-BTP-Oct/XAD-7 resin has better selectivity for Am(III) over Eu(III). In extraction chromatography, the separation of Am(III) from Eu(III) was demonstrated using CA-BTP-Oct/XAD-7 resin. Am(III) was quantitatively recovered from the column with a Eu(III) contamination of only 9%. [ABSTRACT FROM AUTHOR]

To better inform electrorefining operations of used nuclear fuel, a fundamental understanding of the electrochemical properties of each actinide in the molten salt electrolyte is needed. Access to actinide chlorides is thus required to support measurement of these properties. In this work, we synthesized americium trichloride through a novel pathway comprising chlorination of Am2O3 with ZrCl4 in a LiCl–KCl molten salt at 500 °C. The formation of AmCl3 was confirmed by cyclic voltammetry and gamma spectroscopy. This chlorination method does not produce mixed hazardous-radioactive waste and the byproduct, ZrO2, is not electrochemically active and does not affect the actinide electrodeposition reaction. [ABSTRACT FROM AUTHOR]

For the major isotope abundance measurements of plutonium, uranium, and americium, the total evaporation technique yields data with best precision and accuracy characteristics. However, minor isotope abundance measurements using this technique are biased higher due to peak tailing effects. We investigate whether the tailing corrections at the minor isotopes are large enough to shift the major isotope abundance values outside the ITV-2010 values, which are routinely used as pass/fail criteria in proficiency test programs. Measured data in a plutonium sample, a uranium sample, and a uranium separate (from decay of Pu isotopes) is investigated. LA-UR-22–22,282. [ABSTRACT FROM AUTHOR]

Speciation of actinides, and more particularly bioligand-binding ability, influences in vivo behavior. Understanding these interactions is essential for estimation of radiological dose and improvement of decorporation strategies for accidentally contaminated victims. Because the handling of actinides imposes overwhelming difficulties, in vitro assays carried out in physiological conditions are lacking and data regarding such interactions are scarce. In this study, we used a bi-compartmental and dynamic assay, providing physiological conditions (presence of inorganic ions, pH, temperature) to explore interactions between the actinides plutonium (Pu) and americium (Am) and endogenous (proteins transferrin and ferritin) or exogenous ligands (the chelating agent diethylenetriaminpentaacetic acid, DTPA). In this assay, an agarose gel represents the retention compartment of actinides and a dynamic fluid phase, the transfer compartment. The proportion of actinides transferred from static to dynamic phase reflects interactions between Pu/Am and various ligands. The results show differences in the formation of actinide-protein or actinide-DTPA complexes in physiologically relevant media depending on which ligand is present and where. We observed differential behavior for Pu and Am similar to in vivo studies. Thus, our assay may be used to determine the ability of various actinides to interact with specific proteins or with drug candidates for decorporation in complex physiologically relevant environments. [ABSTRACT FROM AUTHOR]

Adsorption reactions on mineral surfaces are influenced by the overall concentration of the adsorbing metal cation. Different site types (strong vs. weak ones) are often included to describe the complexation reactions in the various concentration regimes. More specifically, strong sites are presumed to retain metal ions at low sorbate concentrations, while weak sites contribute to metal ion retention when the sorbate concentration increases. The involvement of different sites in the sorption reaction may, thereby, also be influenced by competing cations, which increase the overall metal ion concentration in the system. To date, very little is known about the complex structures and metal ion speciation in these hypothetical strong- and weak-site regimes, especially in competing scenarios. In the present study, we have investigated the uptake of the actinide americium on corundum (α–Al2O3) in the absence and presence of yttrium as competing metal by combining extended X-ray absorption fine structure spectroscopy (EXAFS) with density functional theory (DFT) calculations. Isotherm studies using the radioactive 152Eu tracer were used to identify the sorption regimes where strong sites and weak sites contribute to the sorption reaction. The overall americium concentration, as well as the presence of yttrium could be seen to influence both the amount of americium uptake by corundum, but also the speciation at the surface. More specifically, increasing the Am3+ or Y3+ concentrations from the strong site to the weak site concentration regimes in the mineral suspensions resulted in a decrease in the overall Am–O coordination number from nine to eight, with a subsequent shortening of the average Am–O bond length. DFT calculations suggest a reduction of the surface coordination with increasing metal–ion loading, postulating the formation of tetradentate and tridentate Am3+ complexes at low and high surface coverages, respectively. [ABSTRACT FROM AUTHOR]

The extraction performance and mechanism of 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-1,10-phenanthroline (CyMe4BTPhen) in the room temperature ionic liquid 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][NTf2]) have been studied and are herein reported. Americium is extracted from nitric acid solutions by cation exchange and is most efficient at low (< 1 M) nitric acid concentrations as opposed to the high (4 M) concentration preferred when using most traditional molecular diluents. The kinetics are slow, taking 24 hours to achieve quantitative extraction of americium but are greatly improved, achieving the same within 8 hours, by dilution with 1-octanol. High SFAm/Eu > 3000 were achieved although decontamination factors for americium from more complex matrices were non-competitive with extraction using traditional molecular diluents. Modest improvements in decontamination factor were attained by the addition of the hydrophilic reagent N,N,N',N'-tetraethyl diglycolamide (TEDGA). [ABSTRACT FROM AUTHOR]

The aqueous reaction of sodium pyrithione, (Na)mpo, with 243AmCl3·nH2O yields a dimerized complex, [243Am(mpo)2(μ-O-mpo)(H2O)]2·3H2O. This compound is compared with isostructural lanthanide pyrithionates, where dimerization across the 4f-block is observed to be dependent upon the size of the cation. Unlike in most reported Am(III) UV-visible absorption spectra, [243Am(mpo)2(μ-O-mpo)(H2O)]2·3H2O shows significant splitting in the fingerprint excitations. This is attributed to a unique ligand-field environment, where the Am–mpo bonds possess different bonding compared to the Nd(III) analog because of increasing covalent interactions. [ABSTRACT FROM AUTHOR]

Variations in bonding between trivalent lanthanides and actinides is critical for reprocessing spent nuclear fuel. The ability to tune bonding and the coordination environment in these trivalent systems is a key factor in identifying a solution for separating lanthanides and actinides. Coordination of 4,4′−bipyridine (4,4′−bpy) and trimethylsilylcyclopentadienide (Cp′) to americium introduces unexpectedly ionic Am−N bonding character and unique spectroscopic properties. Here we report the structural characterization of (Cp′3Am)2(μ − 4,4′−bpy) and its lanthanide analogue, (Cp′3Nd)2(μ − 4,4′−bpy), by single-crystal X-ray diffraction. Spectroscopic techniques in both solid and solution phase are performed in conjunction with theoretical calculations to probe the effects the unique coordination environment has on the electronic structure. The coordination environment has a great impact on the electronic structure, bonding and properties of metal complexes. Here the authors report a dinuclear organometallic americium complex that displays unexpectedly ionic Am−N bonding, but enhanced covalency in the Am−C bonds compared to its neodymium analogue. [ABSTRACT FROM AUTHOR]