Single column ion exchange separation of the transplutonium elements from uranium targets bombarded with heavy ions and catcher foils

A simple pressurized ion exchange apparatus has been devised for rapid ion exchange separation of transplutonium elements synthesized by heavy ion bombardment. Cation exchange with mixed media of mineral acids and organic solvents at elevated temperature was used to separate the transplutonium elements from uranium targets and/or catcher foils (aluminium and copper) dissolved in aqua regia. The transplutonium elements were strongly adsorbed on the cation exchange column and separated in a group from rare earths by elution with hydrochloric acid or mutually separated with 2-hydroxy-2-methylpropionate solution. It has been successfully applied to separate and identify²⁵⁰Fm and²⁴⁶Cf synthesized by the¹⁶O+²³⁸U reaction.     

Preparation of samples for the α—Spectrometry of transplutonium elements

The electrolytic deposition of the hydroxides of rare earth and transplutonium elements on nickel holders from α-hydroxyisobutyrate solutions of 10⁻⁵ M to 5·10⁻¹ M concentrations has been investigated in the presence of ammonium chloride. It is shown that at total concentrations of ≥10⁻¹² M of rare earth and transplutonium elements, their electrodeposition proceeds with a 90% yield.     

Rare earth tungsten bronzes: a new method of synthesis. Perspectives for their application as inert matrices for transmutation of long-life actinide elements

A new method of synthesis of oxide tungsten bronzes containing lanthanide (Ln) Nd and Eu, based on thermal degradation of polyoxotungstate compounds, is proposed. The simplicity of the method allows to consider this class of compounds with chemical formula, Ln_xWO₃, as potential inert target for incineration or transmutation of minor actinides, Am and Cm, in neutron reactors. Nd and Eu were used as analogues of transplutonium elements. Powder X-ray diffraction patterns of compounds synthesized reveal a cubic perovskite structure. The lanthanide content in bronzes was determined by optical spectroscopy analysis. The experimental density of the pressed bronze samples was estimated at 6.58 g cm⁻³, i.e., 89% of the crystallographic value. The thermal stability of the bronzes synthesized was checked up to 900°C in an inert atmosphere. Leaching tests were performed for europium bronzes in nitric acid solutions using luminescence technique.     

Stability constants of the aqueous mono-fluoride complexes of Pu(III) and Am(III) and their correlation with other metal ions

The stability constants of the aqueous mono-fluoride complexes of Pu(III) and Am(III) have been measured using the distribution method. A correlation of the available stability constants of fluoride complexes of trivalent actinides, up to Cf, with fundamental properties like charge and radii of the metal ion has been discussed. Good correlation within the group and as a part of other metal ions was obtained only for transplutonium elements. The reported stability constant values measured by potentiometry and the value obtained by distribution for Pu³⁺ appear to be much higher than expected from this correlation. However, a better correlation was obtained with transplutonium elements when effective charge instead of formal charge was considered for Pu³⁺ in the BSE function.     

Radiation effects on the separation of lanthanides and transplutonides by the TALSPEAK-type extraction

Effects of radiation on the extraction system composed of DEHPA extractant and DTPA aqueous solution containing nitrate were studied by measuring distribution ratios of Am(III) and Nd(III) with the extractant and DTPA solution either one of which was irradiated with⁶⁰Co γ-rays or the organic—aqueous mixed phase irradiated under continuous stirring. The irradiation causes an increase of Df and a decrease of the Nd/Am separation factor β, to an especially large extent in the mixed phase system. These effects are due firstly to the radiolytic decomposition of DTPA and secondarily to the formation of MEHPA. The replacement of nitrate with lactate stops the degradation of DTPA and DEHPA resulting in the retardation of increase of Df and a decrease of separation factor. The DEHPA-DTPA-lactic acid system is concluded to sustain absorption of radiation at an absorbed dose up to 200 Wh·I⁻¹ in the partitioning of transplutonium elements in HLW.     

Neutron activation analysis of pure uranium: Preconcentration of impurity elements

We have developed a radiochemical neutron activation analysis technique (RNAA) of pure uranium with using extraction chromatographic separation of ²³⁹Np from impurity elements in TBP-6M HNO₃ media. The estimation of influence of fission products of ²³⁵U on the results by radiochemical neutron activation analysis has been carried out. For it we have performed NAA with preconcentration of impurity elements. Experiments show that in this case the apparent concentration of Y, Zr, Mo, Cs, La, Ce, Pr, Nd exceeds the true concentration by 2500–3000 times. Therefore, determination of these elements is not possible by RNAA. This technique allowed to use the determination of 26 impurity elements with detection limit 10⁻⁵–10⁻⁹% by mass. This developed technique may be used for the determination of impurities in uranium and its compounds.     

Determination of rare earths in silicate rocks by epithermal neutron activation and a simple group separation

The determination of nine rare earth elements in rock samples by epithermal neutron activation, followed by a simple group-separation procedure and Ge(Li) γ-ray spectrometry, is described. This method is found to be advantageous for the determination of Nd, Gd, Ho, Er and Lu by means of the short-lived nuclides¹⁴⁹Nd,¹⁵⁹Gd,¹⁶⁶Ho,¹⁷¹Er and^176m Lu. Precision for La, Sm and Eu is similar to that of thermal neutron activation, that for Dy is worse. Samples of the standard rocks, basalt BCR-1 and granite G-2, were analyzed by this procedure and the results obtained are compared with previously reported data.     

Separation of transplutonium and rare-earth elements by extraction with HDEHP from DTPA solutions

The extraction behaviour of Am, Cm, Bk, Cf, Es, La, Ce, Pr, Pm, Sm, Eu, Gd, Ho, Yb and Lu in the system HDEHP—DTPA in lactic acid has been studied from the point of view of group separation of the transplutonium and rare-earth elements. Optimum separation conditions have been found on the basis of the results obtained. Some test separations of transplutonium elements from rare-earth fission products have been carried out in real solutions by extraction chromatography. It has been shown that this method can be used successfully for the analytical determination of transplutonium elements as well as for recovery of the latter from irradiated samples.     

Curium isotopes in Chernobyl fallout

In nuclear reactors plutonium and transplutonium isotopes are produced by multiple neutron capture of uranium and plutonium and are important for the energy production and their composition reflects the core burnout. Under normal operation these elements are not released to the environment in significant amounts. There are accordingly very few areas or source terms where exotic transplutonium elements, such as curium isotopes, can be studied in the environment. The Chernobyl accident provided a complex spectrum of fission and activation products in fallout while the relative amounts, compared to the core inventory, of refractory elements such as transuranium and transplutonium elements were small. The major alpha-activity consisted of ²⁴²Cm (T _1/2 = 163 d) that would have decayed after a few years. In this study we have demonstrated the presence of so called supported ²⁴²Cm from the long-lived ²⁴²Am^m (T _1/2 = 141 a) in environmental samples, following fallout from the Chernobyl accident. It has also been possible to assess the core burn up by using the data obtained for the Cm isotopes. The curium isotopes ²⁴³Cm (T _1/2 = 29.1 a) and ²⁴⁴Cm (T _1/2 = 18.1 a) cannot be resolved by conventional alpha-spectrometry. The assessment of these isotopes in environmental samples contaminated from the Chernobyl accident has been made by studying the effective half-life of the mixture of the isotopes. The data are compared with those previously obtained by high-resolution alpha-spectrometry and spectral deconvolution.     

Polymer monolithic capillary microextraction combined on‐line with inductively coupled plasma MS for the determination of trace rare earth elements in biological samples

A rapid and sensitive method based on polymer monolithic capillary microextraction combined on‐line with microconcentric nebulization inductively coupled plasma MS has been developed for the determination of trace/ultratrace rare earth elements in biological samples. For this purpose, the iminodiacetic acid modified poly(glycidyl methacrylate‐trimethylolpropane trimethacrylate) monolithic capillary was prepared and characterized by SEM and FTIR spectroscopy. Factors affecting the extraction efficiency, such as sample pH, sample flow rate, sample/eluent volume, and coexisting ions were investigated in detail. Under the optimal conditions, the LODs for rare earth elements were in the range of 0.08 (Er) to 0.97 ng/L (Nd) with a sampling frequency of 8.5 h^?1, and the RSDs were between 1.5% (Sm) and 7.4% (Nd) (c = 20 ng/L, n = 7). The proposed method was successfully applied to the analysis of trace/ultratrace rare earth elements in human urine and serum samples, and the recoveries for the spiked samples were in the range of 82–105%. The developed method was simple, rapid, sensitive, and favorable for the analysis of trace/ultratrace rare earth elements in biological samples with limited sample volume.     

High-Precision Measurements of the 143Nd/144Nd Isotope Ratio in Certified Reference Materials without Nd and Sm Separation by Multiple Collector Inductively Coupled Plasma Mass Spectrometry

We present a precise and accurate method for the determination of ¹⁴³Nd/¹⁴⁴Nd isotope ratio without Nd and Sm separation by multiple collector inductively coupled plasma mass spectrometry. We corrected instrumental mass discrimination by applying the natural constant ¹⁴⁶Nd/¹⁴⁴Nd ratio as an internal standard after isobaric interference correction of ¹⁴⁴Sm on ¹⁴⁴Nd using interference-free ¹⁴⁷Sm/¹⁴⁹Sm ratio for Sm mass fractionation. The present method was validated by duplicate analyses of several certified reference materials after dissolution and cation-exchange resin purification. The precision (2σ) of the ¹⁴³Nd/¹⁴⁴Nd ratio is less than 10 ppm (internal) and 20 ppm (external), respectively.     

Multielement analysis of uraniferous rocks by INAA: Special reference to interferences due to uranium and fission of uranium

The presence of uranium in a sample enhances the true values of La, Ce, Nd, Sm determined by INAA if appropriate corrections are not made for the interference. The enhancement of the true values comes about because the (n, γ) activation products of these elements, viz.¹⁴⁰La,¹⁴¹Ce,¹⁴⁷Nd,¹⁵³Sm, are also produced from the fission of²³⁵U (～0.72% natural isotopic abundance) even when La, Ce, Nd, Sm are totally absent in the given sample. In a 5 hour irradiation 1 μg of U is found to be equal to 0.28 μg of Ce and 0.23 μg of Nd while the equivalent La is found to be dependent upon the delay from end of irradiation to sample counting time. A numerical procedure is given to correct for these interferences. Spectral interferences from fission and (n, γ) β products of uranium in the determination of other trace elements by INAA is also investigated. Uranium is found to be determined best using the 278 keV gamma-ray of²³⁹Np.     

Neutron activation determination of uranium by coprecipitation of neptunium-239 on zirconium phosphate

A method is proposed for neutron activation determination of U via²³⁹Np. This is separated by coprecipitation of ZrO(H₂PO₄)₂ and its 106 keV γ-peak measured. The sensitivity of the determination is 10⁻⁹ g. The method is based on the well-known ability of Np(IV) to coprecipitate with zirconium phosphate, while Np(VI) does not form insoluble phosphates or fluorides. This permits elimination of elements interfering, with the determination of²³⁹Np via the 106 keV γ-peak: Sm, Nd, Yb, Lu, Pa (from Th) and Ta. The rare earths are eliminated by coprecipitation on LaF₃, and Pa and Ta as insoluble phosphates in an oxidizing medium. The method is suitable for phosphorus-containing samples: phosphorites, apatites and their industrial treatment products. The results obtained for the uranium content with the proposed method are in good agreement with the results of other methods and authors.     

Evidence of Alpha Radiolysis in the Formation of a Californium Nitrate Complex

Well-characterized complexes of transplutonium elements are scarce because of the experimental challenges of working with these elements and the rarity of the isotopes. This leads to a lack of structural and spectroscopic data needed to understand the nature of chemical bonds in these compounds. In this work, the synthesis of Cf(DOPO^q)₂(NO₃)(py) (DOPO^q=2,4,6,8-tetra-tert-butyl-1-oxo-1H-phenoxazin-9-olate; py=pyridine) is reported, in which the nitrate anion is hypothesized to form through the α-radiolysis-induced reaction of pyridine and/or the ligand. Computational analysis of the electronic structure of the complex reveals that the Cf^III–ligand interactions are largely ionic.     

Efficient discrimination of transplutonium actinides by in vivo models

Transplutonium actinides are among the heaviest elements whose macroscale chemical properties can be experimentally tested. Being scarce and hazardous, their chemistry is rather unexplored, and they have traditionally been considered a rather homogeneous group, with most of their characteristics extrapolated from lanthanide surrogates. Newly emerged applications for these elements, combined with their persistent presence in nuclear waste, however, call for a better understanding of their behavior in complex living systems. In this work, we explored the biodistribution and excretion profiles of four transplutonium actinides (²⁴⁸Cm, ²⁴⁹Bk, ²⁴⁹Cf and ²⁵³Es) in a small animal model, and evaluated their in vivo sequestration and decorporation by two therapeutic chelators, diethylenetriamine pentaacetic acid and 3,4,3-LI(1,2-HOPO). Notably, the organ deposition patterns of those transplutonium actinides were element-dependent, particularly in the liver and skeleton, where lower atomic number radionuclides showed up to 7-fold larger liver/skeleton accumulation ratios. Nevertheless, the metal content in multiple organs was significantly decreased for all tested actinides, particularly in the liver, after administering the therapeutic agent 3,4,3-LI(1,2-HOPO) post-contamination. Lastly, the systematic comparison of the radionuclide biodistributions showed discernibly element-dependent organ depositions, which may provide insights into design rules for new bio-inspired chelating systems with high sequestration and separation performance.

Transplutonium actinides are among the heaviest elements whose macroscale chemical properties can be experimentally tested.     

Possibilities of ED-XRF with radionuclide sources for analysis of plants

A comparative evaluation of the applicability of different radionuclide sources for the determination of toxic elements in plants by ED-XRF is presented.²³⁸Pu or¹⁰⁹Cd are suggested as most suitable single excitation sources in ED-XRF for monitoring investigations. More elements are determined with a combination of⁵⁵F/¹⁰⁹Cd(²³⁸Pu)/²⁴¹Am. The results obtained by radionuclide ED-XRF analysis of different plants show that the method permits the reliable determination of Br, Ca, Fe, K, Mn, Rb, Sr and Zn in plant bioindicators. For toxic elements like As, Cd, Cu Cr, Hg, Ni, Se and Pb the detection limits of the method are not low enough.     

Direct inductively coupled plasma optical emission spectrometry for analysis of waste samarium-cobalt magnets

An analytical procedure for direct determination of Al, Mg, Ti, Cr, Mn, Nb, La, Nd, Eu, Gd, Tb, Dy, Tm, Yb, Lu, Hf, Ni, Cu, Fe, Zr Sm and Co by ICP-OES in waste samarium-cobalt magnets has been developed. The significant influence of the matrix on all determinable components has been shown. The influence of operation parameters (ICP power and nebuliser flow rate) on the matrix effect has been studied using two plasma observation modes (axial and radial). For the first time, the optimal conditions for ICP-OES analysis of waste samarium-cobalt magnets has been substantiated (ICP power 1400 W, nebuliser flow rate 0.5–0.6 L/min). The analytical capabilities of the method have been evaluated using spike recovery test, certified reference materials and comparison with ICP-MS. ICP-OES measurements were performed in the axial mode for trace elements (with concentrations of n·10^?4-n·10^?2 % wt.) and in the radial mode for matrix elements and analytes (with concentrations higher than n·10^?2 % wt.). The limits of quantification (LOQs) were in the range of n·10^?5 wt% for Mn, Zr and Yb and n·10^?4 wt% for Al, Mg, Ti, Cr, Hf, La, Ni, Cu, Tb, Lu, Nb, Fe, Nd, Eu, Gd, Dy and Tm. RSD ranged from 0.2 to 10.6%.     

Recent advances in the analytical chemistry of the transplutonium elements

A survey is given of current developments in the determination of the transplutonium elements, and of the properties useful in their analytical chemistry.     

Use of chelating resins and inductively coupled plasma mass spectrometry for simultaneous determination of trace and major elements in small volumes of saline water samples

For some saline environments (e.g. deeply percolating groundwater, interstitial water in marine sediments, water sample collected after several steps of fractionation) the volume of water sample available is limited. A technique is presented which enables simultaneous determination of major and trace elements after preconcentration of only 60 mL sample on chelating resins. Chelex-100 and Chelamine were used for the preconcentration of trace elements (Cd, Cu, Pb, Zn, Sc) and rare earth elements (La, Ce, Nd, Yb) from saline water before their measurement by inductively coupled plasma mass spectrometry. Retention of the major elements (Na, Ca, Mg) by the Chelamine resin was lower than by Chelex; this enabled their direct measurement in the solution after passage through the resin column. For trace metal recoveries both resins yield the same mass balance. Only Chelex resin enabled the quantitative recovery of rare earth elements. The major elements, trace metals and rare earth elements cannot be measured after passage through one resin only. The protocol proposes the initial use of Chelamine for measurement of trace and major elements and then passage the same sample through the Chelex resin for determination of the rare earth elements. The detection limit ranged from 1 to 12 pg mL^–1. At concentrations of 1 ng mL^–1 of trace metals and REE spiked in coastal water the precision for 10 replicates was in the range of 0.3–3.4% (RSD). The accuracy of the method was demonstrated by analyzing two standard reference waters, SLRS-3 and CASS-3.