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Materials (Basel, Switzerland) Jan 2024The hydrolysis mechanism of americium was calculated using density functional theory, and the detailed microscopic reaction mechanism was obtained. The results show that...
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 H, 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.
PubMed: 38591375
DOI: 10.3390/ma17030572 -
Journal of the American Chemical Society Apr 2024Comparison of bonding and electronic structural features between trivalent lanthanide (Ln) and actinide (An) complexes across homologous series' of molecules can provide...
Comparison of bonding and electronic structural features between trivalent lanthanide (Ln) and actinide (An) complexes across homologous series' of molecules can provide insights into subtle and overt periodic trends. Of keen interest and debate is the extent to which the valence f- and d-orbitals of trivalent Ln/An ions engage in covalent interactions with different ligand donor functionalities and, crucially, how bonding differences change as both the Ln and An series are traversed. Synthesis and characterization (SC-XRD, NMR, UV-vis-NIR, and computational modeling) of the homologous lanthanide and actinide N-heterocyclic carbene (NHC) complexes [M(CMe)(X)(I)] {X = I, M = La, Ce, Pr, Nd, U, Np, Pu; X = Cl, M = Nd; X = I/Cl, M = Nd, Am; and I = [C(NMeCMe)]} reveals consistently shorter An-C vs Ln-C distances that do not substantially converge upon reaching Am/Nd comparison. Specifically, the difference of 0.064(6) Å observed in the La/U pair is comparable to the 0.062(4) Å difference observed in the Nd/Am pair. Computational analyses suggest that the cause of this unusual observation is rooted in the presence of π-bonding with the valence d-orbital manifold in actinide complexes that is not present in the lanthanide congeners. This is in contrast to other documented cases of shorter An-ligand vs Ln-ligand distances, which are often attributed to increased 5f vs 4f radial diffusivity leading to differences in 4f and 5f orbital bonding involvement. Moreover, in these traditional observations, as the 5f series is traversed, the 5f manifold contracts such that by americium structural studies often find no statistically significant Amvs Nd metal-ligand bond length differences.
PubMed: 38569081
DOI: 10.1021/jacs.3c12721 -
Chemical Science Feb 2024Americium (Am) is a key radioactive element in consideration in nuclear waste treatment. Separation of Am from the fission products, lanthanides, is a prerequisite to...
Americium (Am) is a key radioactive element in consideration in nuclear waste treatment. Separation of Am from the fission products, lanthanides, is a prerequisite to minimize the hazardous impact of Am and make utilization of rare Am isotopes, but it represents a great challenge due to the chemical similarity between the two groups of elements. Herein, we realize the separation by first oxidizing Am(iii) to high valent Am(vi) and then converting it to Am(v) in a biphasic extraction system with Bi(v) oxidant incorporated in an organic phase. Am(v) is highly stabilized during the separation process and this leads to record high Ln/Am separation factors (>10) in a single contact over a wide range of acidities.
PubMed: 38332823
DOI: 10.1039/d3sc06240f -
Applied Radiation and Isotopes :... Apr 2024The n-lab is a fast neutron facility based in the Department of Physics, University of Cape Town, offering collimated neutron beams produced by an MP 320...
The n-lab is a fast neutron facility based in the Department of Physics, University of Cape Town, offering collimated neutron beams produced by an MP 320 deuterium-tritium sealed tube neutron generator, and a 220 GBq americium-beryllium radioisotopic source. Characterisations of the spatial and energy distributions of the fast neutron beams were performed using an EJ-301 organic liquid scintillator detector and digital data acquisition system. Neutron energy spectra were obtained through unfolding analyses with MAXED, and a Monte Carlo approach to the propagation of uncertainties was implemented. Measurements of fluence and neutron emission rates were determined through the neutron activation of copper foils and subsequently used to validate the scaling of the unfolded neutron energy spectra.
PubMed: 38309120
DOI: 10.1016/j.apradiso.2024.111196 -
RSC Advances Dec 2023A new variant of the AmSel (Americium Selective Separation) system for the separation of Am(iii) from a PUREX raffinate was tested in which the aliphatic diluent was...
A new variant of the AmSel (Americium Selective Separation) system for the separation of Am(iii) from a PUREX raffinate was tested in which the aliphatic diluent was replaced by the ionic liquid Aliquat-336 nitrate. For this ionic liquid variant, the kinetics, and the influence of both the HNO concentration and the ligand concentration on the stripping were evaluated. In addition, both the original AmSel system, and the ionic liquid variant were demonstrated on a simulated highly active raffinate. The introduction of Aliquat-336 nitrate results in an improved separation between Am(iii) and the fission products, in particularly for the light lanthanides and strontium. The Am/Cm separation factors of the ionic liquid variant were found to remain similar to the original AmSel process. Despite the improved separation, slower stripping kinetics were observed and extraction of the SO-Ph-BTBP complexant to the Aliquat 336 nitrate phase occurred at low HNO concentrations during the stripping step. However, adequate mitigation actions to counteract these issues were found and applied.
PubMed: 38090078
DOI: 10.1039/d3ra06064k -
PloS One 2023The article assesses the content of radionuclides in hoofed animals inhabiting the Semipalatinsk Test Site by calculation. Hoofed animals' faeces were sampled to...
The article assesses the content of radionuclides in hoofed animals inhabiting the Semipalatinsk Test Site by calculation. Hoofed animals' faeces were sampled to determine the content of radionuclides in their diets. Based on values determined for the content of radionuclides in animals; diets, the content of radionuclides in the meat and milk of farm animals-cows (Bos taurus taurus), sheep (Ovis), goats (Capra hircus) and horses (Equus caballus Lin., 1758) as well as in the meat of wild animals-european moose (Alces alces Lin., 1758), argali (Ovis ammon Lin., 1758), roe deer (Capreolus pygargus Pal., 1771) and saiga (Saiga tatarica Lin., 1766) was calculated. No excess of permissible values of the content of 137Cs and 90Sr in the meat of farm animals was found to be expected, even for a conventional 'conservative' scenario, in which maxima of the radionuclide activity concentration in a vegetable feed (faeces) are taken as a basis. 241Am and 239+240Pu in the meat of farm hoofed animals are not standardized. Their predicted maxima of activity concentration are very low, and even in the 'conservative' scenario, they do not exceed 1.8×10-2 Bq kg-1, 1.4×10-1 Bq kg-1 and 1.6×10-1 Bq kg-1, respectively. In the milk of farm animals, the content of 137Cs and 90Sr does not exceed permissible values. 241Am and 239+240Pu in the milk of farm animals are not standardized. Their predicted activity concentration values in the milk of sheep and goats do not exceed 6.5×10-2 Bq l-1, for cows- 2.6×10-2 Bq l-1, for horses- 3.1×10-2 Bq l-1. Permissible values of 137Cs and 90Sr in the meat of wild hoofed animals are not exceeded either. In the meat of argali, roe deer and saigas, relatively high levels of 137Cs are predictable. 241Am and 239+240Pu in meat of wild animals are not standardized. Their predicted activity concentration values in the meat of moose and argali do not exceed 3.2×10-1 Bq kg-1 and 1.6×10-1 Bq kg-1, respectively, for roe deer and saiga-5.4×10-2 Bq kg-1. Thus, in case of free grazing in the STS territory, no excess of permissible values of standardized radionuclides (137Cs and 90Sr) in the meat and milk of hoofed animals is predictable.
Topics: Female; Cattle; Animals; Horses; Sheep; Cesium Radioisotopes; Strontium Radioisotopes; Plutonium; Americium; Bioaccumulation; Deer; Animals, Domestic; Goats
PubMed: 38011204
DOI: 10.1371/journal.pone.0294632 -
Clinical Epigenetics Oct 2023Alpha (α)-radiation is a ubiquitous environmental agent with epigenotoxic effects. Human exposure to α-radiation at potentially harmful levels can occur repetitively...
BACKGROUND
Alpha (α)-radiation is a ubiquitous environmental agent with epigenotoxic effects. Human exposure to α-radiation at potentially harmful levels can occur repetitively over the long term via inhalation of naturally occurring radon gas that accumulates in enclosed spaces, or as a result of a single exposure from a nuclear accident. Alterations in epigenetic DNA methylation (DNAm) have been implicated in normal aging and cancer pathogenesis. Nevertheless, the effects of aberrations in the methylome of human lung cells following exposure to single or multiple α-irradiation events on these processes remain unexplored.
RESULTS
We performed genome-wide DNAm profiling of human embryonic lung fibroblasts from control and irradiated cells using americium-241 α-sources. Cells were α-irradiated in quadruplicates to seven doses using two exposure regimens, a single-fraction (SF) where the total dose was given at once, and a multi-fraction (MF) method, where the total dose was equally distributed over 14 consecutive days. Our results revealed that SF irradiations were prone to a decrease in DNAm levels, while MF irradiations mostly increased DNAm. The analysis also showed that the gene body (i.e., exons and introns) was the region most altered by both the SF hypomethylation and the MF hypermethylation. Additionally, the MF irradiations induced the highest number of differentially methylated regions in genes associated with DNAm biomarkers of aging, carcinogenesis, and cardiovascular disease. The DNAm profile of the oncogenes and tumor suppressor genes suggests that the fibroblasts manifested a defensive response to the MF α-irradiation. Key DNAm events of ionizing radiation exposure, including changes in methylation levels in mitochondria dysfunction-related genes, were mainly identified in the MF groups. However, these alterations were under-represented, indicating that the mitochondria undergo adaptive mechanisms, aside from DNAm, in response to radiation-induced oxidative stress.
CONCLUSIONS
We identified a contrasting methylomic profile in the lung fibroblasts α-irradiated to SF compared with MF exposures. These findings demonstrate that the methylome response of the lung cells to α-radiation is highly dependent on both the total dose and the exposure regimen. They also provide novel insights into potential biomarkers of α-radiation, which may contribute to the development of innovative approaches to detect, prevent, and treat α-particle-related diseases.
Topics: Humans; DNA Methylation; DNA; Fibroblasts; Lung; Biomarkers
PubMed: 37891670
DOI: 10.1186/s13148-023-01564-z -
Radiation and Environmental Biophysics Nov 2023A major challenge in modelling the decorporation of actinides (An), such as americium (Am), with DTPA (diethylenetriaminepentaacetic acid) is the fact that standard...
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.
Topics: Humans; Rats; Animals; Pentetic Acid; Americium; Models, Biological; Chelating Agents; Plutonium
PubMed: 37831188
DOI: 10.1007/s00411-023-01046-z -
Gels (Basel, Switzerland) Aug 2023The binding of actinide ions (Am(III) and U(VI)) in aqueous solutions by hybrid silica-hyperbranched poly(ethylene imine) nanoparticles (NPs) and xerogels (XGs) has been...
The binding of actinide ions (Am(III) and U(VI)) in aqueous solutions by hybrid silica-hyperbranched poly(ethylene imine) nanoparticles (NPs) and xerogels (XGs) has been studied by means of batch experiments at different pH values (4, 7, and 9) under ambient atmospheric conditions. Both materials present relatively high removal efficiency at pH 4 and pH 7 (>70%) for Am(III) and U(VI). The lower removal efficiency for the nanoparticles is basically associated with the compact structure of the nanoparticles and the lower permeability and access to active amine groups compared to xerogels, and the negative charge of the radionuclide species is formed under alkaline conditions (e.g., UO(CO) and Am(CO)). Generally, the adsorption process is relatively slow due to the very low radionuclide concentrations used in the study and is basically governed by the actinide diffusion from the aqueous phase to the solid surface. On the other hand, adsorption is favored with increasing temperature, assuming that the reaction is endothermic and entropy-driven, which is associated with increasing randomness at the solid-liquid interphase upon actinide adsorption. To the best of our knowledge, this is the first study on hybrid silica-hyperbranched poly(ethylene imine) nanoparticle and xerogel materials used as adsorbents for americium and uranium at ultra-trace levels. Compared to other adsorbent materials used for binding americium and uranium ions, both materials show far higher binding efficiency. Xerogels could remove both actinides even from seawater by almost 90%, whereas nanoparticles could remove uranium by 80% and americium by 70%. The above, along with their simple derivatization to increase the selectivity towards a specific radionuclide and their easy processing to be included in separation technologies, could make these materials attractive candidates for the treatment of radionuclide/actinide-contaminated water.
PubMed: 37754371
DOI: 10.3390/gels9090690 -
Scientific Reports Aug 2023Nuclear radiation detectors are indispensable for research in the field of nuclear radiation, X-ray spectroscopy and other areas. Interest in silicon p-i-n detectors of...
Nuclear radiation detectors are indispensable for research in the field of nuclear radiation, X-ray spectroscopy and other areas. Interest in silicon p-i-n detectors of nuclear radiation is increasing today due to the possibility of their operation under normal conditions. In this paper, an equivalent circuit of a silicon-lithium p-i-n nuclear radiation detector is proposed. The proposed circuit is obtained using the classical Shockley equation for silicon semiconductors and the telegraph equations. The parameters of the equivalent circuit were determined using the multiple regression method. As a result of simulation of the model in the MATLAB Simulink graphical development environment, the amplitude-frequency and phase-frequency characteristics of the proposed model were obtained. Using the Monte Carlo method, the alpha-decay of the uranium isotope [Formula: see text], thorium isotope [Formula: see text] and americium isotope [Formula: see text] the alpha-decay spectrum was obtained. Obtained alpha-decay spectra coincides with the experimental data, presented in previous works of other authors.
PubMed: 37532741
DOI: 10.1038/s41598-023-39710-5