-
Disaster Medicine and Public Health... Oct 2022Americium is a man-made metal produced in very small quantities in nuclear reactors. Americium-241 is one of the radioactive isotopes of americium and has commercial...
Americium is a man-made metal produced in very small quantities in nuclear reactors. Americium-241 is one of the radioactive isotopes of americium and has commercial applications, including use in smoke detectors. This is a case report of an occupational inhalation of americium-241, treated with both effective external decontamination and the use of diethylenetriamine pentaacetate to promote decorporation. This experience is significant because of the potential for americium or similar radionuclides to be used in "dirty" bombs or other radiological dispersion devices to cause large-scale radioactive contamination.
Topics: Humans; Americium; Chelation Therapy; Pentetic Acid; Decontamination
PubMed: 34399875
DOI: 10.1017/dmp.2021.211 -
Radiation Research Jul 2019In this work, a baseline compartmental model of the distribution and retention of americium in the rat for a systemic intake was derived. The model was derived from data...
In this work, a baseline compartmental model of the distribution and retention of americium in the rat for a systemic intake was derived. The model was derived from data obtained from a study designed to evaluate the behavior of americium in the first 28 days after incorporation. A pharmacokinetic (PK)-front-end modeling approach was used to specify transfer to and from the extracellular fluids (ECF) in the various tissues in terms of vascular flow and volumes of ECF. Back-end rates representing transport into and out of the cells were determined empirically. Uncertainties in transfer rates were investigated using Markov chain Monte Carlo (MCMC). The combination of PK-front-end model and the back-end model structure used allowed for extrapolation to the earliest times with small uncertainty. This approach clearly demonstrated the rapid transfer of material from ECF to liver and bone. This model provides a baseline for modeling the action of decorporation agents, such as DTPA.
Topics: Americium; Animals; Biological Transport; Extracellular Space; Female; Kinetics; Male; Models, Biological; Rats; Tissue Distribution
PubMed: 31107639
DOI: 10.1667/RR15256.1 -
Applied Radiation and Isotopes :... May 2008The human and animal data on the biokinetics of (242)Cm and (244)Cm are reviewed and shown to be very similar to those for (241)Am. Liver and skeleton are the main... (Comparative Study)
Comparative Study Review
The human and animal data on the biokinetics of (242)Cm and (244)Cm are reviewed and shown to be very similar to those for (241)Am. Liver and skeleton are the main organs of deposition and the retention of curium in the skeleton is very prolonged in all the species examined. Retention of both curium and americium in the liver appears to be species-dependent, being relatively rapidly removed from the liver of rats, and probably humans, but being tenaciously retained in dogs and some other species. The radiotoxicity of curium is also reviewed and it is shown that, as with (241)Am, lung and bone tumour induction are the major hazards from inhaled and systemically deposited (244)Cm. The use of chelating agents for the treatment of accidental contamination of the human body with (242,244)Cm is also discussed.
Topics: Americium; Animals; Curium; Female; Humans; Maternal-Fetal Exchange; Pregnancy; Tissue Distribution
PubMed: 18222696
DOI: 10.1016/j.apradiso.2007.12.002 -
Journal of Radiological Protection :... Jun 2019The biokinetic model for systemic americium (Am) currently recommended by the International Commission on Radiological Protection (ICRP) for application to occupational...
The biokinetic model for systemic americium (Am) currently recommended by the International Commission on Radiological Protection (ICRP) for application to occupational intake of Am is based on information available through the early 1990s. Much additional information on Am biokinetics has been developed in the past 25 y, including measurements of retention and excretion of Am in many workers with Am burdens and post mortem measurements of Am in tissues of some of those workers. The ICRP's current Am model is reasonably consistent with the updated information, with the main exception that the current model apparently overestimates 24-hour urinary Am as a fraction of skeletal or systemic Am at late times after intake. This paper provides an overview of current information on the systemic kinetics of Am in adult human subjects and laboratory animals and presents an updated biokinetic model for systemic Am that addresses the discrepancies between the current database and current ICRP systemic model for Am. This model is applied in Part 4 (to appear) of an ICRP series of reports on intake of radionuclides by workers called the OIR (Occupational Intake of Radionuclides) series.
Topics: Adult; Americium; Animals; Female; Humans; Male; Models, Biological; Occupational Exposure; Tissue Distribution
PubMed: 30840936
DOI: 10.1088/1361-6498/ab0d3b -
Journal of the American Chemical Society Jun 2017Developing a better understanding of covalency (or orbital mixing) is of fundamental importance. Covalency occupies a central role in directing chemical and physical...
Developing a better understanding of covalency (or orbital mixing) is of fundamental importance. Covalency occupies a central role in directing chemical and physical properties for almost any given compound or material. Hence, the concept of covalency has potential to generate broad and substantial scientific advances, ranging from biological applications to condensed matter physics. Given the importance of orbital mixing combined with the difficultly in measuring covalency, estimating or inferring covalency often leads to fiery debate. Consider the 60-year controversy sparked by Seaborg and co-workers ( Diamond, R. M.; Street, K., Jr.; Seaborg, G. T. J. Am. Chem. Soc. 1954 , 76 , 1461 ) when it was proposed that covalency from 5f-orbitals contributed to the unique behavior of americium in chloride matrixes. Herein, we describe the use of ligand K-edge X-ray absorption spectroscopy (XAS) and electronic structure calculations to quantify the extent of covalent bonding in-arguably-one of the most difficult systems to study, the Am-Cl interaction within AmCl. We observed both 5f- and 6d-orbital mixing with the Cl-3p orbitals; however, contributions from the 6d-orbitals were more substantial. Comparisons with the isoelectronic EuCl indicated that the amount of Cl 3p-mixing with Eu 5d-orbitals was similar to that observed with the Am 6d-orbitals. Meanwhile, the results confirmed Seaborg's 1954 hypothesis that Am 5f-orbital covalency was more substantial than 4f-orbital mixing for Eu.
Topics: Americium; Chlorides
PubMed: 28613849
DOI: 10.1021/jacs.7b03755 -
Journal of Environmental Radioactivity Apr 2021The new data on Pu, Pu, Pu, Am vertical distribution in the deep western Black Sea sediments was analyzed. The sediment dating, obtained by means of Pu/Pu activity ratio...
The new data on Pu, Pu, Pu, Am vertical distribution in the deep western Black Sea sediments was analyzed. The sediment dating, obtained by means of Pu/Pu activity ratio vertical distribution, suggested the upper 3 cm layer of sediments to be formed during 27 years after the Chernobyl accident and the deeper layers to be formed earlier in pre-Chernobyl time (before 1986). The whole data set on profiles of radionuclides studied was shown to reflect the history of their input into the basin and elimination of these radionuclides from the water column. Analysis of inventories of plutonium alpha-emitting nuclides ensured a more significant contribution of Chernobyl fallout into the present total Pu inventory than into Pu one. The Am inventory after-deposition enhancement due to Pu decay was estimated at 74% in pre-Chernobyl sediment layer and the general contribution of Pu support in the total Am inventory in situ enhancement was estimated at 49%.
Topics: Americium; Black Sea; Geologic Sediments; Plutonium; Radiation Monitoring; Water Pollutants, Radioactive
PubMed: 33503559
DOI: 10.1016/j.jenvrad.2021.106540 -
Journal of Chromatography. A Apr 2022Several novel extraction chromatography resins (EXC) have been synthesised by solvent impregnation of the triazine ligands...
Several novel extraction chromatography resins (EXC) have been synthesised by solvent impregnation of the triazine ligands 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenzo[1,2,4]triazin-3-yl)-2,2'-bipyridine (CyMeBTBP) and 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-1,10-phenanthroline (CyMeBTPhen) into Amberlite XAD7 and Amberchrom CG300 polymer supports. The resins have been physically characterised by a suite of spectroscopic, analytical and imaging techniques. The resins have also been evaluated in terms of their ability to selectively extract americium from complex matrices intended to simulate those typical of spent nuclear fuel raffinate, environmental samples and nuclear forensics samples. The resins have been compared with previously reported attempts to generate EXC resins based on CyMeBTBP and CyMeBTPhen. Previously reported resins all rely on complex synthesis for the formation of a covalent bond between extractant and support by contrast with the simpler solvent impregnation method reported here. The Amberchrom supported CyMeBTBP resin achieved a weight distribution ration (D) of 170 within 60 min and a decontamination factor (DF) of >1000 for americium over lanthanides by column chromatography. The Amberchrom CyMeBTPhen resin achieved a D of 540 within 30 min and a DF for americium from lanthanides of 60-160.
Topics: Americium; Chromatography; Resins, Plant; Solvents; Triazines
PubMed: 35294895
DOI: 10.1016/j.chroma.2022.462950 -
Journal of the American Chemical Society Sep 2021Anthropogenic radionuclides, including long-lived heavy actinides such as americium and curium, represent the primary long-term challenge for management of nuclear...
Anthropogenic radionuclides, including long-lived heavy actinides such as americium and curium, represent the primary long-term challenge for management of nuclear waste. The potential release of these wastes into the environment necessitates understanding their interactions with biogeochemical compounds present in nature. Here, we characterize the interactions between the heavy actinides, Am and Cm, and the natural lanthanide-binding protein, lanmodulin (LanM). LanM is produced abundantly by methylotrophic bacteria, including , that are widespread in the environment. We determine the first stability constant for an Am-protein complex (AmLanM) and confirm the results with CmLanM, indicating a ∼5-fold higher affinity than that for lanthanides with most similar ionic radius, Nd and Sm, and making LanM the strongest known heavy actinide-binding protein. The protein's high selectivity over Am's daughter nuclide Np enables lab-scale actinide-actinide separations as well as provides insight into potential protein-driven mobilization for these actinides in the environment. The luminescence properties of the Cm-LanM complex, and NMR studies of Gd-LanM, reveal that lanmodulin-bound f-elements possess two coordinated solvent molecules across a range of metal ionic radii. Finally, we show under a wide range of environmentally relevant conditions that lanmodulin effectively outcompetes desferrioxamine B, a hydroxamate siderophore previously proposed to be important in trivalent actinide mobility. These results suggest that natural lanthanide-binding proteins such as lanmodulin may play important roles in speciation and mobility of actinides in the environment; it also suggests that protein-based biotechnologies may provide a new frontier in actinide remediation, detection, and separations.
Topics: Americium; Bacterial Proteins; Coordination Complexes; Curium; Ions; Lanthanoid Series Elements; Luminescent Measurements; Macromolecular Substances; Methylobacterium extorquens; Molecular Conformation; Protein Binding; Structure-Activity Relationship
PubMed: 34542285
DOI: 10.1021/jacs.1c07103 -
Applied Radiation and Isotopes :... Aug 2022A rapid radiochemical method has been developed for estimation of plutonium and americium in nasal swab using extractive liquid scintillation spectrometry. The method...
A rapid radiochemical method has been developed for estimation of plutonium and americium in nasal swab using extractive liquid scintillation spectrometry. The method involves solvent extraction of plutonium and americium from pre-treated nasal swab using 0.2 M Di-(2-ethylhexyl)phosphoricacid prepared in toluene scintillator & back extraction of americium in aqueous phase using 0.35 M HNO Activity assessment was carried out using liquid scintillation spectrometry. Overall recovery obtained was 96% for plutonium and 76% for americium with a sample turnaround time of 3 h.
Topics: Americium; Plutonium; Radiometry; Solvents; Spectrum Analysis
PubMed: 35623136
DOI: 10.1016/j.apradiso.2022.110297 -
Health Physics Aug 2019Decorporation therapy with salts of diethylenetriamine-pentaacetic acid binds actinides, thereby limiting uptake to organs and enhancing the rate at which actinides are...
Decorporation therapy with salts of diethylenetriamine-pentaacetic acid binds actinides, thereby limiting uptake to organs and enhancing the rate at which actinides are excreted in urine. International Commission on Radiological Protection reference biokinetic models cannot be used to fit this enhanced exertion simultaneously with the baseline actinide excretion rate that is observed prior to the start of therapy and/or after the effects of therapy have ceased. In this study, the Coordinated Network on Radiation Dosimetry approach, which was initially developed for modeling decorporation of plutonium, was applied to model decorporation of americium using data from a former radiation worker who agreed to donate his body to the US Transuranium and Uranium Registries for research. This individual was exposed to airborne Am, resulting in a total-body activity of 66.6 kBq. He was treated with calcium-diethylenetriamine-pentaacetic acid for 7 y. The time and duration of intakes are unknown as no incident reports are available. Modeling of different assumptions showed that an acute intake of 5-μm activity median aerodynamic diameter type M aerosols provides the most reasonable description of the available pretherapeutic data; however, the observed Am activity in the lungs at the time of death was higher than the one predicted for type M material. The Coordinated Network on Radiation Dosimetry approach for decorporation modeling was used to model the in vivo chelation process directly. It was found that the Coordinated Network on Radiation Dosimetry approach, which only considered chelation in blood and extracellular fluids, underestimated the urinary excretion of Am during diethylenetriamine-pentaacetic acid treatment; therefore, the approach was extended to include chelation in the liver. Both urinary excretion and whole-body retention could be described when it was assumed that 25% of chelation occurred in the liver, 75% occurred in the blood and ST0 compartment, and the chelation rate constant was 1 × 10 pmol d. It was observed that enhancement of urinary excretion of Am after injection of diethylenetriamine-pentaacetic acid exponentially decreased to the baseline level with an average half-time of 2.2 ± 0.7 d.
Topics: Americium; Chelating Agents; Chelation Therapy; Decontamination; Humans; Kinetics; Male; Models, Biological; Occupational Exposure; Radiation Dosage; Radiation Injuries; Radiation Protection; Radiometry; Tissue Donors
PubMed: 30489383
DOI: 10.1097/HP.0000000000000931