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Radiation and Environmental Biophysics Mar 2020At the tissue level, energy deposition in cells is determined by the microdistribution of alpha-emitting radionuclides in relation to sensitive target cells.... (Review)
Review
At the tissue level, energy deposition in cells is determined by the microdistribution of alpha-emitting radionuclides in relation to sensitive target cells. Furthermore, the highly localized energy deposition of alpha particle tracks and the limited range of alpha particles in tissue produce a highly inhomogeneous energy deposition in traversed cell nuclei. Thus, energy deposition in cell nuclei in a given tissue is characterized by the probability of alpha particle hits and, in the case of a hit, by the energy deposited there. In classical microdosimetry, the randomness of energy deposition in cellular sites is described by a stochastic quantity, the specific energy, which approximates the macroscopic dose for a sufficiently large number of energy deposition events. Typical examples of the alpha-emitting radionuclides in internal microdosimetry are radon progeny and plutonium in the lungs, plutonium and americium in bones, and radium in targeted radionuclide therapy. Several microdosimetric approaches have been proposed to relate specific energy distributions to radiobiological effects, such as hit-related concepts, LET and track length-based models, effect-specific interpretations of specific energy distributions, such as the dual radiation action theory or the hit-size effectiveness function, and finally track structure models. Since microdosimetry characterizes only the initial step of energy deposition, microdosimetric concepts are most successful in exposure situations where biological effects are dominated by energy deposition, but not by subsequently operating biological mechanisms. Indeed, the simulation of the combined action of physical and biological factors may eventually require the application of track structure models at the nanometer scale.
Topics: Alpha Particles; Animals; Bone and Bones; Humans; Lung; Radioisotopes; Radiometry
PubMed: 31863162
DOI: 10.1007/s00411-019-00826-w -
Inorganic Chemistry Jul 2019Both AmAlO and PuAlO perovskites have been synthesized and characterized using powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared...
Both AmAlO and PuAlO perovskites have been synthesized and characterized using powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). AmAlO perovskite showed a rhombohedral configuration (space group 3̅) in agreement with previous studies. The effect of americium α-decay on this material has been followed by XRD and Al MAS NMR analyses. In a first step, a progressive increase in the level of disorder in the crystalline phase was detected, associated with a significant crystallographic swelling of the material. In a second step, the crystalline AmAlO perovskite was progressively converted into amorphous AmAlO, with a total amorphization occurring after 8 months and 2 × 10 α-decays/g. For the first time, PuAlO perovskite was synthesized with an orthorhombic configuration (space group ), showing an interesting parallel to CeAlO and PrAlO lanthanide analogues. High-temperature XRD was performed and showed a → 3̅ phase transition occurring between 473 and 573 K. The thermal behavior of 3̅ PuAlO was followed from 573 to 1273 K, and extrapolation of the data suggests that cubic plutonium perovskite should become stable at around 1850 K (3̅ → 3̅ transition).
PubMed: 31246454
DOI: 10.1021/acs.inorgchem.9b00679 -
Scientific Reports Mar 2017Fundamental knowledge on intrinsic plutonium colloids is important for the prediction of plutonium behaviour in the geosphere and in engineered systems. The first...
Fundamental knowledge on intrinsic plutonium colloids is important for the prediction of plutonium behaviour in the geosphere and in engineered systems. The first synthetic route to obtain salt-free intrinsic plutonium colloids by ultrasonic treatment of PuO suspensions in pure water is reported. Kinetics showed that both chemical and mechanical effects of ultrasound contribute to the mechanism of Pu colloid formation. In the first stage, fragmentation of initial PuO particles provides larger surface contact between cavitation bubbles and solids. Furthermore, hydrogen formed during sonochemical water splitting enables reduction of Pu(IV) to more soluble Pu(III), which then re-oxidizes yielding Pu(IV) colloid. A comparative study of nanostructured PuO and Pu colloids produced by sonochemical and hydrolytic methods, has been conducted using HRTEM, Pu L-edge XAS, and O K-edge NEXAFS/STXM. Characterization of Pu colloids revealed a correlation between the number of Pu-O and Pu-Pu contacts and the atomic surface-to-volume ratio of the PuO nanoparticles. NEXAFS indicated that oxygen state in hydrolytic Pu colloid is influenced by hydrolysed Pu(IV) species to a greater extent than in sonochemical PuO nanoparticles. In general, hydrolytic and sonochemical Pu colloids can be described as core-shell nanoparticles composed of quasi-stoichiometric PuO cores and hydrolyzed Pu(IV) moieties at the surface shell.
PubMed: 28256635
DOI: 10.1038/srep43514 -
Scientific Reports Nov 2023Plutonium (Pu) cycling and mobility in the environment can be impacted by the iron cycle and microbial community dynamics. We investigated the spatial and temporal...
Plutonium (Pu) cycling and mobility in the environment can be impacted by the iron cycle and microbial community dynamics. We investigated the spatial and temporal changes of the microbiome in an iron (Fe)-rich, plutonium-contaminated, monomictic reservoir (Pond B, Savannah River Site, South Carolina, USA). The microbial community composition varied with depth during seasonal thermal stratification and was strongly correlated with redox. During stratification, Fe(II) oxidizers (e.g., Ferrovum, Rhodoferax, Chlorobium) were most abundant in the hypoxic/anoxic zones, while Fe(III) reducers (e.g., Geothrix, Geobacter) dominated the deep, anoxic zone. Sulfate reducers and methanogens were present in the anoxic layer, likely contributing to iron and plutonium cycling. Multinomial regression of predicted functions/pathways identified metabolisms highly associated with stratification (within the top 5%), including iron reduction, methanogenesis, C1 compound utilization, fermentation, and aromatic compound degradation. Two sediment cores collected at the Inlet and Outlet of the pond were dominated by putative fermenters and organic matter (OM) degraders. Overall, microbiome analyses revealed the potential for three microbial impacts on the plutonium and iron biogeochemical cycles: (1) plutonium bioaccumulation throughout the water column, (2) Pu-Fe-OM-aggregate formation by Fe(II) oxidizers under microaerophilic/aerobic conditions, and (3) Pu-Fe-OM-aggregate or sediment reductive dissolution and organic matter degradation in the deep, anoxic waters.
Topics: Iron; Plutonium; Ponds; Bacteria; Oxidation-Reduction; Microbiota; Ferrous Compounds
PubMed: 37952079
DOI: 10.1038/s41598-023-45182-4 -
Scientific Reports Jul 2023Unlike short-term laboratory experiments, studies at sites historically contaminated with radionuclides can provide insight into contaminant migration behavior at...
Unlike short-term laboratory experiments, studies at sites historically contaminated with radionuclides can provide insight into contaminant migration behavior at environmentally-relevant decadal timescales. One such site is Pond B, a seasonally stratified reservoir within Savannah River Site (SC, USA) has low levels (μBq L) of plutonium in the water column. Here, we evaluate the origin of plutonium using high-precision isotope measurements, investigate the impact of water column geochemistry on plutonium cycling during different stratification periods, and re-evaluate long-term mass balance of plutonium in the pond. New isotopic data confirm that reactor-derived plutonium overwhelms input from Northern Hemisphere fallout at this site. Two suggested mechanisms for observed plutonium cycling in the water column include: (1) reductive dissolution of sediment-derived Fe(III)-(oxyhydr)oxides during seasonal stratification and (2) plutonium stabilization complexed strongly to Fe(III)-particulate organic matter (POM) complexes. While plutonium may be mobilized to a limited extent by stratification and reductive dissolution, peak plutonium concentrations are in shallow waters and associated with Fe(III)-POM at the inception of stratification. This suggests that plutonium release from sediments during stratification is not the dominant mechanism driving plutonium cycling in the pond. Importantly, our analysis suggests that the majority is retained in shallow sediments and may become increasingly recalcitrant.
Topics: Plutonium; Geologic Sediments; Ponds; Seasons; Ferric Compounds; Radioisotopes; Water Pollutants, Radioactive; Water
PubMed: 37422457
DOI: 10.1038/s41598-023-37276-w -
Analytical Sciences : the International... 2016A simple potentiometric method for determining the free acidity without complexation in the presence of hydrolysable metal ions and sequentially determining the...
A simple potentiometric method for determining the free acidity without complexation in the presence of hydrolysable metal ions and sequentially determining the plutonium concentration by a direct spectrophotometric method using a single aliquot was developed. Interference from the major fission products, which are susceptible to hydrolysis at lower acidities, had been investigated in the free acidity measurement. This method is applicable for determining the free acidity over a wide range of nitric acid concentrations as well as the plutonium concentration in the irradiated fuel solution prior to solvent extraction. Since no complexing agent is introduced during the measurement of the free acidity, the purification step is eliminated during the plutonium estimation, and the resultant analytical waste is free from corrosive chemicals and any complexing agent. Hence, uranium and plutonium can be easily recovered from analytical waste by the conventional solvent extraction method. The error involved in determining the free acidity and plutonium is within ±1% and thus this method is superior to the complexation method for routine analysis of plant samples and is also amenable for remote analysis.
PubMed: 27063711
DOI: 10.2116/analsci.32.401 -
Environmental Pollution (Barking, Essex... Nov 2021Concentrations of Pu and Pu in 163 surface soil samples and five soil cores collected from the northeast and north China were analyzed using the radiochemical separation...
Concentrations of Pu and Pu in 163 surface soil samples and five soil cores collected from the northeast and north China were analyzed using the radiochemical separation combined with inductively coupled plasma mass spectrometry measurement. The average Pu/Pu atomic ratios (0.185 ± 0.018) for all surface soil samples indicated that the global fallout is the major source of plutonium in the studied region. The Pu concentrations of the surface soil ranged from 0.002 mBq/g to 4.82 mBq/g, lying in the range of the reported results in the areas with similar latitude, except for a few samples. The distribution of Pu in this region is controlled by the deposition of plutonium in the atmosphere and its preservation in the soil, which were affects by multi-factors such as topography, climate, utilization of the land and vegetation coverage. The analytical results could be used as the baseline data for the assessment of the impact of nuclear activities in the past and the future.
Topics: China; Plutonium; Radiation Monitoring; Radioactive Fallout; Soil Pollutants, Radioactive
PubMed: 34426197
DOI: 10.1016/j.envpol.2021.117967 -
Materials (Basel, Switzerland) Nov 2022The chemical corrosion aging of plutonium is a very important topic. It is easy to be corroded and produces oxidation products of various valence states because of its...
The chemical corrosion aging of plutonium is a very important topic. It is easy to be corroded and produces oxidation products of various valence states because of its 5f electron orbit between local and non-local. On the one hand, the phase diagram of plutonium and oxygen is complex, so there is still not enough research on typical structural phases. On the other hand, most of the studies on plutonium oxide focus on PuO and PuO with stoichiometric ratio, while the understanding of non-stoichiometric ratio, especially for PuO, is not deep enough. Based on this, using the DFT + U theoretical scheme of density functional theory, we have systematically studied the structural stability, lattice parameters, electronic structure, mechanical and optical properties of six typical high temperature phases of β-PuO, α-PuOγ-PuO PuO, α-PuOγ-PuO. Further, the mechanical properties and optical behavior of PuO under different oxygen vacancy concentrations are analyzed and discussed in detail. The result shows that the elasticity modulus of single crystal in mechanical properties is directly related to the oxygen/plutonium ratio and crystal system. As the number of oxygen vacancies increases, the mechanical constants continue to increase. In terms of optical properties, PuO has the best optical properties, and the light absorption rate decreases with the increase of oxygen vacancy concentration.
PubMed: 36363381
DOI: 10.3390/ma15217785 -
Environmental Science and Pollution... Dec 2022The Aare river system in Switzerland, with two nuclear power plants on the banks of the river, and its intermediate lakes and reservoirs, provides a unique opportunity...
The Aare river system in Switzerland, with two nuclear power plants on the banks of the river, and its intermediate lakes and reservoirs, provides a unique opportunity to analyze the contribution of different sources to the radioactive contamination. Sediment cores were collected from two lakes and a reservoir, all connected by the river Aare. In order to study the influence of the Chernobyl accident, one sediment core was collected from a lake in the southern part of Switzerland. The sediment cores were sliced and analyzed with gamma ray spectrometry. Plutonium, americium, and uranium were extracted radiochemically, and their concentrations were measured with a sector field ICP-MS. The uranium isotope ratios were further measured with a multi collector ICP-MS. The maximum Cs activity from the Chernobyl accident and the Pu and Cs activities associated to the 1963 global fallout maximum were well identified in sediments from all three lakes. High-resolution records of plutonium isotopes in the zone of the sediments corresponding to the period of maximum fallout from the atmospheric nuclear weapon testing showed distinct fingerprints, depending on the different test activities. Pu isotope ratios could be used to detect non-global fallout plutonium. The ratio Am/Pu was used to determine the age of the plutonium. Despite of very low Pu and Am concentrations, the calculated plutonium production dates seemed to be reasonable for the sediment layers corresponding to the NWT tests. The calculated production date of the plutonium in the upper most 15 cm of the sediment core seemed to be younger. The reason for this could be additional non-global fallout plutonium. For the lake sediments, natural ratios for U/U and enriched or depleted ratios for U/U were measured, depending on the lake. A small increase of the U/U ratio could be recognized for the NWT zone in all three lakes and, for Lake Lugano, a further distinct increase in the Chernobyl layer.
Topics: Plutonium; Americium; Lakes; Uranium; Water Pollutants, Radioactive; Switzerland; Geologic Sediments; Cesium Radioisotopes; Isotopes; Radioactive Fallout
PubMed: 35595889
DOI: 10.1007/s11356-022-20785-y -
Scientific Reports Apr 2017Lattice dynamics and elasticity for the high-temperature ε phase (body-centered cubic; bcc) of plutonium is predicted utilizing first-principles electronic structure...
Lattice dynamics and elasticity for the high-temperature ε phase (body-centered cubic; bcc) of plutonium is predicted utilizing first-principles electronic structure coupled with a self-consistent phonon method that takes phonon-phonon interaction and strong anharmonicity into account. These predictions establish the first sensible lattice-dynamics and elasticity data on ε-Pu. The atomic forces required for the phonon scheme are highly accurate and derived from the total energies obtained from relativistic and parameter-free density-functional theory. The results appear reasonable but no data exist to compare with except those from dynamical mean-field theory that suggest ε-plutonium is mechanically unstable. Fundamental knowledge and understanding of the high-temperature bcc phase, that is generally present in all actinide metals before melting, is critically important for a proper interpretation of the phase diagram as well as practical modeling of high-temperature properties.
PubMed: 28442720
DOI: 10.1038/s41598-017-01034-6