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In the field of nuclear toxicology, the knowledge of the interaction of actinides (An) with biomolecules is of prime concern in order to elucidate their toxicity mechanism and to further develop selective decorporating agents. In this work, we demonstrated the great potential of hydrophilic interaction liquid chromatography (HILIC) to separate polar thorium (Th) biomimetic peptide complexes, as a key starting point to tackle these challenges. Th 4+ was used as plutonium (Pu 4+ ) analogue and pS16 and pS1368 as synthetic di- and tetra-phosphorylated peptides capable of mimicking the interaction sites of these An in osteopontin (OPN), a hyperphosphorylated protein. The objective was to determine the relative affinity of pS16 and pS1368 towards Th 4+ , and to evaluate the pS1368 selectivity when Th 4+ was in competition complexation reaction with UO 2 2+ at physiological pH. To meet these aims, HILIC was simultaneously coupled to electrospray ionization mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS), which allowed to identify online the molecular structure of the separated complexes and quantify them, in a single step. Dedicated HILIC conditions were firstly set up to separate the new dimeric Th 2 (peptide) 2 complexes with good separation resolution (peptide = pS16 or pS1368). By adding pS16 and pS1368 in different proportions relatively to Th 4+ , we found that lower or equal proportions of pS16 with respect to pS1368 were not sufficient to displace pS1368 from Th 2 pS1368 2 and pS16 proportion higher than pS1368 led to the formation of a predominant ternary complex Th 2 (pS16)(pS1368), demonstrating preferential Th 4+ binding to the tetra-phosphorylated peptide. Finally, online identification and quantification of the formed complexes when Th 4+ and UO 2 2+ were mixed in equimolar ratio relatively to pS1368 showed that in spite of pS1368 has been specifically designed to coordinate UO 2 2+ , pS1368 is also Th 4+ -selective and exhibits stronger affinity for this latter than for UO 2 2+ . Hence, the results gathered through this approach highlight the impact of Th 4+ coordination chemistry on its interaction with pS1368 and more widely to its affinity for biomolecules., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

We explored the speciation and kinetics of the Pu(VI)-citrate and Pu(III)-citrate systems (pH m = 2.5-11.0, I = 0.1 M NaCl, T = 23 °C, O 2 (g) < 2 ppm) using ultraviolet-visible-near-infrared (UV-vis-NIR) spectrophotometry, solvent extraction, and PHREEQC modeling. Formation constants were determined for PuO 2 (HcitH)(aq) (log  K ° 1,1 = 1.09 ± 0.05) and PuO 2 (HcitH)(citH) 3- (log  K ° 1,2 = -0.20 ± 0.07), and evidence for (PuO 2 ) m (citH - k ) n (OH) x 2 m (3+ k ) n - x was identified under alkaline conditions. Pu(VI) species were found to be less stable in the presence of citrate than in the absence of citrate ( t ≤ 168 days); the rate of reduction increased with increasing pH. The direct reduction of Pu(VI) to Pu(IV) was required to fit experimental data in the presence of citrate but did not improve the fit for Pu in the absence of citrate. We also observed increased Pu(III) stability in the presence of citrate ( t ≤ 293 days), with higher concentrations of Pu(III) favored at lower pH. Finally, we provide evidence of a radiolysis-driven mechanism for the citrate-mediated reduction of plutonium that involves electron transfer from the oxidative breakdown of citrate. Our work highlights the need to investigate the redox effect of organic ligands on plutonium oxidation states under repository-relevant conditions.

Sorption of Pu(VI) onto synthesized goethite under oxidizing and normal conditions was investigated, which revealed its pH dependence on different solid/liquid ratios. Pu speciation upon sorption on the solid phase was characterized via extended X-ray absorption fine structure (EXAFS) spectroscopy, while that in solution was assessed using ultraviolet-visible (UV-Vis) spectroscopy and liquid-liquid extraction. The obtained results demonstrate differences in plutonium behavior in the studied systems. Pu(VI) remains hexavalent on the goethite surface and in solution under oxidizing conditions. While Pu(IV) is stabilized on the mineral and Pu(V) is found in solution under normal conditions. This study provides the thermodynamic descriptions of these reactions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The 239 Pu, 238 U, and 241 Am concentrations and 239 Pu/ 240 Pu, 235 U/ 238 U, and 236 U/ 238 U atom ratios were measured in the hair and nail samples using a new method utilized TEVA, UTEVA, and DGA extraction chromatography and multi-collector ICP-MS. Samples were collected from individuals who donated their bodies to the United States Transuranium and Uranium Registries. The concentration of 239 Pu ranged from 0.22 to 15.8 ng/kg. The 240 Pu/ 239 Pu isotopic ratios ranged from 0.026 to 0.127 which is consistent with weapons-grade plutonium. Concentration of uranium fell between 1.84 μg/kg and 29.5 μg/kg and 235 U/ 238 U ratios ranged from 4.8 × 10 -3 to 7.6 × 10 -3 . Elevated 236 U/ 238 U atom ratios were measured in two cases and ranged from 5.0 × 10 -6 - 2.4 × 10 -5 indicating exposure to spent or reprocessed uranium material. The concentration of 241 Am was measured in four hair samples and ranged from 0.02 to 0.21 ng/kg., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:John D. Brockman reports was provided by University of Missouri. John D. Brockman reports a relationship with University of Missouri that includes: employment., (Copyright © 2023. Published by Elsevier B.V.)

From the available thermodynamic data in the literature, a review of the impact of the formation of complexes between triscarbonatoactinyl(VI) and alkaline earth(II) (Ae) is estimated under varying conditions. First, after analyzing the literature data and using the ascertained thermodynamic data available from the commissioned reviews from the Nuclear Energy Agency (Organization for the Economic Cooperation and Development) Thermochemical DataBank Project on actinides (An) U, Np, and Pu, and from recently determined Ae n UO 2 (CO 3 ) 3 (4-2n)- thermodynamic functions, the formation of Ae n AnO 2 (CO 3 ) 3 (4-2n)- complexes for Pu(VI) and Np(VI) are estimated using linear free energy relationships (LFERs). The data are in good agreement with the sole determination of AePuO 2 (CO 3 ) 3 2- from Jo et al. (Dalton Trans. 49, 11605), which gives a relative confidence in the LFERs, and allows the application to actual situations. From existing uranium data, first, the impact of the origin of the data on the calculated predominance is addressed under 0.1 M NaCl and atmospheric CO 2 (g); second, the influence of ionic strength and salinity on predominance is estimated; and finally, the influence of temperature up to 50 °C on the solubility of uraninite in a deep geological radioactive waste storage or disposal site is calculated. For neptunium and plutonium, the impact of the potential log 10 β°(Ae n AnO 2 (CO 3 ) 3 (4-2n)- ) on Pourbaix diagrams of Pu and Np in Mg-Ca-CO 3 media are estimated from Jo et al. (Dalton Trans. 49, 11605) and LFERs. Finally, the application to the speciation of Pu and Np in seawater is proposed., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Pascal Reiller reports financial support was provided by National Agency for Radioactive Waste and Enriched Fissile Materials., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Transferrin (Tf) is a glycoprotein that transports iron from the serum to the various organs. Several studies have highlighted that Tf can interact with metals other than Fe(III), including actinides that are chemical and radiological toxics. We propose here to report on the behavior of Th(IV) and Pu(IV) in comparison with Fe(III) upon Tf complexation. We considered UV-Vis and IR data of the M 2 Tf complex (M=Fe, Th, Pu) and combined experimental EXAFS data with MD models. EXAFS data of the first M-O coordination sphere are consistent with the MD model considering 1 synergistic carbonate. Further EXAFS data analysis strongly suggests that contamination by Th/Pu colloids seems to occur upon Tf complexation, but it seems limited. SAXS data have also been recorded for all complexes and also after the addition of Deferoxamine-B (DFOB) in the medium. The Rg values are very close for apoTf, ThTf and PuTf, but slightly larger than for holoTf. Data suggest that the structure of the protein is more ellipsoidal than spherical, with a flattened oblate form. From this data, the following order of conformation size might be considered:holoTf2 Tf (M=Th, Pu)2 Tf-DFOB (M=Fe, Th, Pu)., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Due to its presence in the nuclear industry and its strong radiotoxicity, plutonium is an actinide of major interest in the event of internal contamination. To improve the understanding of its mechanisms of transport and accumulation in the body, the complexation of Pu(IV) to the most common protein calcium-binding motif found in cells, the EF-hand motif of calmodulin, was investigated. Visible and X-ray absorption spectroscopies (XAS) in solution made it possible to investigate the speciation of plutonium at physiological pH (pH 7.4) and pH 6 in two variants of the calmodulin Ca-binding site I and using Pu(IV) in different media: carbonate, chloride, or nitrate solutions. Three different species of Pu were identified in the samples, with formation of 1:1 Pu(IV):calmodulin peptide complexes, Pu(IV) reduction, and formation of peptide-mediated Pu(IV) hexanuclear cluster.

Abstract: This work investigates the uptake and root-shoot transport of plutonium (Pu) and iron (Fe) in corn ( Zea mays ) to gain insight into the Pu uptake pathway. Plutonium has no known biological function in plants yet may feasibly enter plants through the uptake pathway used by Fe (an essential nutrient), as these two elements have similar chemical properties. A series of experiments was conducted in which two hydroponically grown corn strains (one normal and one deficient in the transporter protein for Fe) were exposed to varying concentrations of complexed Pu and Fe. Results suggest that while Fe did inhibit Pu uptake to a certain extent, Pu was able to use alternative uptake pathways. In a 10 ppb Pu:1 ppb Fe hydroponic solution, all shoots had detectable shoot Pu concentrations compared to only 22% of plants when the Fe concentration was raised to 10 ppb. While root Pu accumulation was reduced for the corn strain deficient in the Fe transporter protein at lower Pu media concentrations, there were no differences at higher Pu concentrations, signifying the existence of substitute transport routes. A comparison of citrate and deferoxamine B (DFOB) ligand influence found that Pu complexed with DFOB remained in the roots of the plant, while movement of Pu into the shoots of the plant was more prevalent with the Pu-citrate complex. This study advances understanding of the behavior and mobility of Pu in the terrestrial environment and specifically the interactions between Pu and an essential nutrient in a common crop species., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Health Physics Society.)

A compact field-deployable microfluidic system has been developed to improve timelines for the rapid analysis of debris in post-detonation nuclear forensics. We used a high-resolution 3D printer to miniaturize typical laboratory-based procedures into a fieldable platform. Microfluidic half-modules were produced for the purification of Pu from excess U, along with a portable alpha chamber for the following isotopic analysis of the Pu stream. A porous PTFE membrane is soaked with a hydrophobic tributyl phosphate (TBP) solution and is placed between two half-modules; separation is performed as a liquid-liquid extraction in an extraction channel across this membrane, where the forward and back-extractions occur within one complete module. Following separation, a 100 μL sampling of the Pu-bearing stream is injected into a small-footprint 3D printed alpha chamber for isotopic assay via alpha spectrometry as part of an online process. In this first demonstration of microfluidic separation coupled with online alpha spectrometry, high extraction yields have been obtained for Pu (98.9 ± 4.0)% and U (97.5 ± 2.5)%. The process uses less than 800 μL of solution with separation chemistry complete within 45 minutes and subsequent alpha spectrometry initiating 25 minutes after separation.

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.

In case of an incident in the nuclear industry or an act of war or terrorism, the dissemination of plutonium could contaminate the environment and, hence, humans. Human contamination mainly occurs via inhalation and/or wounding (and, less likely, ingestion). In such cases, plutonium, if soluble, reaches circulation, whereas the poorly soluble fraction (such as small colloids) is trapped in alveolar macrophages or remains at the site of wounding. Once in the blood, the plutonium is delivered to the liver and/or to the bone, particularly into its mineral part, mostly composed of hydroxyapatite. Countermeasures against plutonium exist and consist of intravenous injections or inhalation of diethylenetetraminepentaacetate salts. Their effectiveness is, however, mainly confined to the circulating soluble forms of plutonium. Furthermore, the short bioavailability of diethylenetetraminepentaacetate results in its rapid elimination. To overcome these limitations and to provide a complementary approach to this common therapy, we developed polymeric analogs to indirectly target the problematic retention sites. We present herein a first study regarding the decontamination abilities of polyethyleneimine methylcarboxylate (structural diethylenetetraminepentaacetate polymer analog) and polyethyleneimine methylphosphonate (phosphonate polymeric analog) directed against Th(IV), used here as a Pu(IV) surrogate, which was incorporated into hydroxyapatite used as a bone model. Our results suggest that polyethylenimine methylphosphonate could be a good candidate for powerful bone decontamination action.

Understanding the mechanisms involved in retention and clearance of actinides from the lungs after accidental intake is essential for the evaluation of the associated radiological risks. Although the absorption of radioelements has been shown in vivo to depend on their nature and physico-chemical properties, their mechanisms of translocation remain unknown. In this study, we have evaluated in vitro the binding and uptake by bronchial epithelial cells Calu-3 of 2 transuranic actinides, plutonium (Pu) and americium (Am), as the first steps of translocation across the pulmonary barrier. For this purpose, Calu-3 cells grown to confluence in 24-well plates were exposed to the radioelements for 24 h under various culture conditions. Two compartments were identified for the association of actinides to cells, corresponding to the membrane bound and internalized fractions. Binding of Pu was slightly higher than of Am, and depended on its initial chemical form (nitrate, citrate, colloids). Uptake of Pu and Am nitrate was higher in serum-free conditions than in supplemented medium, with an active mechanism involved in Pu internalization. Overall, our results suggest that complexation of actinides to bioligands may have an influence on their uptake by pulmonary epithelial cells, and therefore possibly on their subsequent absorption into blood., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The solution-state interactions of plutonium and berkelium with the octadentate chelator 3,4,3-LI(1,2-HOPO) (343-HOPO) were investigated and characterized by X-ray absorption spectroscopy, which revealed in situ reductive decomposition of the tetravalent species of both actinide metals to yield Pu(III) and Bk(III) coordination complexes. X-ray absorption near-edge structure (XANES) measurements were the first indication of in situ synchrotron redox chemistry as the Pu threshold and white-line position energies for Pu-343-HOPO were in good agreement with known diagnostic Pu(III) species, whereas Bk-343-HOPO results were found to mirror the XANES behavior of Bk(III)-DTPA. Extended X-ray absorption fine structure results revealed An-O HOPO bond distances of 2.498 (5) and 2.415 (2) Å for Pu and Bk, respectively, which match well with bond distances obtained for trivalent actinides and 343-HOPO via density functional theory calculations. Pu(III)- and Bk(III)-343-HOPO data also provide initial insight into actinide periodicity as they can be compared with previous results with Am(III)-, Cm(III)-, Cf(III)-, and Es(III)-343-HOPO, which indicate there is likely an increase in 5f covalency and heterogeneity across the actinide series., (open access.)

The impact of the contamination of living organisms by actinide elements has been a constant subject of attention since the 1950s. But to date still little is understood. Ferritin is the major storage and regulation protein of iron in many organisms, it consists of a protein ring and a ferrihydric core at the center. This work sheds light on the interactions of early actinides (Th, Pu) at oxidation state +IV with ferritin and its ability to store those elements at physiological pH compared to Fe. The ferritin-thorium load curve suggests that Th IV saturates the protein (2840 Th atoms per ferritin) in a similar way that Fe does on the protein ring. Complementary spectroscopic techniques (spectrophotometry, infrared spectroscopy, and X-ray absorption spectroscopy) were combined with molecular dynamics to provide a structural model of the interaction of Th IV and Pu IV with ferritin. Comparison of spectroscopic data together with MD calculations suggests that Th IV and Pu IV are complexed mainly on the protein ring and not on the ferrihydric core. Indeed from XAS data, there is no evidence of Fe neighbors in the Th and Pu environments. On the other hand, carboxylates from amino acids of the protein ring and a possible additional carbonate anion are shaping the cation coordination spheres. This thorough description from a molecular view point of Th IV and Pu IV interaction with ferritin, an essential iron storage protein, is a cornerstone in comprehensive nuclear toxicology., (© 2020 Wiley-VCH GmbH.)

Administration of diethylenetriaminepentaacetic acid (DTPA) is the treatment approach used to promote the decorporation of internalized plutonium. Here we evaluated the efficacy of PEGylated liposomes coated with DTPA, primarily designed to prevent enhanced plutonium accumulation in bones, compared to marketed nonliposomal DTPA and liposomes encapsulating DTPA. The comparative effects were examined in terms of reduction of activity in tissues of plutonium-injected rats. The prompt treatment with DTPA-coated liposomes elicited an even greater efficacy than that with liposome-encapsulated DTPA in limiting skeletal plutonium. This advantage, undoubtedly due to the anchorage of DTPA to the outer layer of liposomes, is discussed, as well as the reason for the loss of this superiority at delayed times after contamination. Plutonium complexed with DTPA-coated liposomes in extracellular compartments was partly diverted into the liver and the spleen. These complexes and those directly formed inside hepatic and splenic cells appeared to be degraded, then released from cells at extremely slow rates. This transitory accumulation of activity, which could not be counteracted by combining both liposomal forms, entailed an underestimation of the efficacy of DTPA-coated liposomes on soft tissue plutonium until total elimination probably more than one month after treatment. DTPA-coated liposomes may provide the best delivery vehicle of DTPA for preventing plutonium deposition in tissues, especially in bone where nuclides become nearly impossible to remove once fixed. Additional development efforts are needed to limit the diversion or to accelerate cell release of plutonium bound to DTPA-coated liposomes, using a labile bond for DTPA attachment., (©2021 by Radiation Research Society. All rights of reproduction in any form reserved.)

Plutonium mononitride is one of the main fuels for Generation IV reactors and can be prepared from nitrogenation of plutonium hydride. We investigated the adsorption and dissociation of nitrogen on PuH 2 (111) surface to elaborate the initial stage of nitrogenation. The adsorption energies varied greatly with respect to the adsorption sites and orientations of the adsorbed molecule. The nitrogen exhibited preferential adsorption above the ccp site, where the molecular nitrogen was nearly parallel to the PuH 2 surface and pointed to the nearest Pu atom. The orbital hybridization and the electrostatic attraction between the Pu and N weakened the N-N bond in the adsorbed molecule. The mechanism of the dissociation process was investigated within transition state theory, and the analysis of the activation barrier indicated that dissociation of nitrogen is not the rate-determining step of nitrogenation. These findings can contribute to a better understanding of the nuclear fuel cycle.

Plutonium has potential applications in energy production in well-controlled nuclear reactors. Since nuclear power plants have great merit as environmentally friendly energy sources with a recyclable system, a recycling system for extracting Pu from spent fuels using suitable extractants has been proposed. Pu leakage is a potential environmental hazard, hence the need for chemical sensor development. Both extractants and chemical sensors involve metal-ligand interactions and to develop efficient extractants and chemical sensors, structural information about Pu ligands must be obtained by quantum calculations. Herein, six representative nitrogen tridentate ligands were introduced, and their binding stabilities were evaluated. The tridentate L6, which contains tri-pyridine chelate with benzene connectors, showed the highest binding energies for Pu(IV) and PuO 2 (VI) in water. Analysis based on the quantum theory of atoms in molecular analysis, including natural population analysis and electron density studies, provided insight into the bonding characteristics for each structure. We propose that differences in ionic bonding characteristics account for the Pu-ligand stability differences. These results form a basis for designing novel extractants and organic Pu sensors.

The possibility of plutonium (Pu) intake by radiation workers can not be ruled out. Transportation of Pu(IV) to various organs/cells is mainly carried through iron-carrying protein, serum transferrin (sTf), by receptor-mediated endocytosis. Understanding the Pu-sTf interaction is a primary step toward future design of its decorporating agents. We report MD simulations of Pu(IV) binding with sTf and look out for its decorporation at extracellular pH using suitable ligands. MD simulations were carried out in polarizable water environment at different protonation states of the protein. Results unravel the binding motif of Pu(IV): (1) sTf binds the ion in closed conformation at extracellular serum pH with carbonate as synergistic anions, (2) change in protonation state of dilysine (K206 and K296)-trigger and that of the carbonate ion at acidic endosomal pH is found to cause conformational changes of protein, conducive for the heavy ion to be released, although; (3) strong electrostatic interaction between D63 in the binding-cleft and Pu(IV) is found not to ever set free the ion. In an endeavour to decorporate Pu(IV), fragmented molecular form of hydroxypyridinone (HOPO) and catechol (CAM)-based ligands are docked at the binding site (BS) of the protein and metadynamics simulations are conducted. Pu(IV) binding at BS is found to be so strong that it was not detached from BS with the docked HOPO. However, for the identical set of simulation parameters, CAM is found to facilitate dislodging the heavy ion from the protein's binding influence. Differential behaviour of the two chelators is further explored. Fragmented molecular form of hydroxy-pyridinone (HOPO) and catecholamide (CAM) ligands were docked at the binding-site (BS) of human serum transferrin (sTf) to explore their feasibility as plausible Pu(IV) decorporating agents by employing metadynamics method. CAM was found to dislodge Pu from the sTf BS, while HOPO could not.

Chelating agents are administered to treat significant intakes of radioactive elements such as plutonium, americium, and curium. These drugs may be used as a medical countermeasure after radiological accidents and terrorist acts. The administration of a chelating agent, such as Ca-DTPA or Zn-DTPA, affects the actinide's normal biokinetics. It enhances the actinide's rate of excretion, posing a dose assessment challenge. Thus, the standard biokinetic models cannot be directly applied to the chelation-affected bioassay data in order to assess the radiation dose. The present study reviews the scientific literature, from the early 1970s until the present, on the different studies that focused on developing new chelation models and/or modeling of bioassay data affected by chelation treatment. Although scientific progress has been achieved, there is currently no consensus chelation model available, even after almost 50 y of research. This review acknowledges the efforts made by different research groups, highlighting the different methodology used in some of these studies. Finally, this study puts into perspective where we were, where we are, and where we are heading in regards to chelation modeling.

Occupational contamination is a potential health risk associated with plutonium inhalation. DTPA remains the chelating drug of choice to decorporate plutonium. In this study, plutonium was found to be more effectively removed from lungs by a single inhalation of nebulized DTPA solution at only 1.1 µmol.kg -1 than by a single intravenous (i.v.) dose of DTPA at 15 µmol.kg -1 . When DTPA was inhaled promptly after contamination, it removed the transportable fraction of plutonium prior blood absorption, thereby preventing both liver and bone depositions. Conversely, DTPA injection was better than inhalation at reducing the extrapulmonary burden, probably due to the much greater circulating dose, favoring the mobilization of plutonium already translocated. Thus, prompt inhalation, concomitantly supplemented with i.v. injection, of DTPA induced an important decrease in extrapulmonary deposits. Repeated DTPA inhalations over several weeks were more efficient than a single inhalation in limiting both pulmonary and extrapulmonary plutonium retention, due at least in part to the chelation of the transportable fraction of lung plutonium. Furthermore, repeated DTPA injections remained better at reducing liver and bone plutonium retentions. Taken together, our results suggest that multiple DTPA inhalations may be considered an effective treatment after inhalation of plutonium, particularly given the ease of this needle-free delivery, for the two following conditions: 1. A treatment combining i.v. injection and inhalation should be given in an emergency scenario to efficiently chelate the activity already absorbed; 2. Inhalations should be administered daily to effectively trap the early transferable fraction.

The manuscript presents the results of the development of new material for high-level waste (HLW) management: the magnesium potassium phosphate (MKP) compound. The possibility of using zeolite (Sokyrnytsya deposit) to increase the mechanical, thermal, and hydrolytic resistance of this compound with immobilized HLW was studied. The main component of the used natural zeolite is a mineral of the clinoptilolite-heulandite series, and quartz, microcline, and clay minerals (illite, sepiolite, and smectite) are present as impurities. The compressive strength of the compound, containing at least 4.2 wt % zeolite, is about 25 MPa. Compound containing 28.6 wt % zeolite retains high compressive strength (at least 9.0 MPa), even after heat treatment at 450 °C. The adding of zeolite to the composition of the compound increases its hydrolytic stability, while the leaching rate of the mobile nuclides 137 Cs and 90 Sr decreases up to one order of values. Differential leaching rate of radionuclides from the compound containing 28.6 wt % zeolite is 2.6 × 10 -7 for 137 Cs, 2.9 × 10 -6 for 90 Sr, 1.7 × 10 -9 for 239 Pu, and 2.9 × 10 -9 g/(cm 2 ∙day) for 241 Am. Thus, the properties of the resulting compound correspond to the requirements for solidified HLW in Russia.

In ultralow Pu analyses, the gold standard is thermal ionization mass spectrometry (TIMS), which requires pure sources to achieve its performance. This purity is achieved through step-wise purifications. In this work single, anion-exchange beads were trapped in the tubing to allow for dynamic solution cycling over the surface of the beads to improve the rates of metal complex uptake. Rates of Pu sorption on single ∼900 μm SIR-1200 and ∼620 μm Reillex-HPQ beads were determined for single beads trapped in a tube with syringe pump driven dynamic solution cycling over the bead, improving sorption and desorption rates. A static control was used as a comparison. Using 238 Pu to enable facile activity-based measurements, rates were determined by measuring the residual Pu after contact with beads using liquid scintillation analysis (LSA) for fixed periods of time. Syringe pump driven dynamic solution cycling results in ∼5 and ∼15-fold improvements in the sorption rates for SIR-1200 and Reillex-HPQ. Impacts on desorption were also examined., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Individuals with significant intakes of plutonium (Pu) are typically treated with chelating agents, such as the trisodium salt form of calcium diethylenetriaminepentaacetate (CaNa 3 -DTPA, referred to hereafter as Ca-DTPA). Currently, there is no recommended approach for simultaneously modeling plutonium biokinetics during and after chelation therapy. In this study, an improved modeling system for plutonium decorporation was developed. The system comprises three individual model structures describing, separately, the distinct biokinetic behaviors of systemic plutonium, intravenously injected Ca-DTPA and in vivo-formed Pu-DTPA chelate. The system was linked to ICRP Publication 100, "Human Alimentary Tract Model for Radiological Protection" and NCRP Report 156, Development of a Biokinetic Model for Radionuclide-Contaminated Wounds and Procedures for Their Assessment, Dosimetry and Treatment." Urine bioassay and chelation treatment data from an occupationally-exposed individual were used for model development. Chelation was assumed to occur in the blood, soft tissues, liver and skeleton. The coordinated network for radiation dosimetry approach to decorporation modeling was applied using a chelation constant describing the secondorder, time-dependent kinetics of the in vivo chelation reaction. When using the proposed system of models for plutonium decorporation, a significant improvement of the goodness-of-fit to the urinary excretion data was observed and more accurate predictions of postmortem plutonium retention in the skeleton, liver and wound site were achieved., (© 2019 by Radiation Research Society.)

In recent decades, interest in plutonium mobility has increased significantly due to the need of the United States, as well as other nations, to deal with commercial spent nuclear fuel, nuclear weapons disarmament, and the remediation of locations contaminated by nuclear weapons testing and production. Although there is a global consensus that geologic disposal is the safest existing approach to dealing with spent nuclear fuel and high-level nuclear waste, only a few nations are moving towards implementing a geologic repository due to technical and political barriers. Understanding the factors that affect the mobility of plutonium in the subsurface environment is critical to support the development of such repositories. The importance of redox chemistry in determining plutonium mobility cannot be understated. While Pu(iv) is generally assumed to be immobile in the subsurface environment due to sorption or precipitation, Pu(v) tends to be mobile due to its relatively low effective charge and weak complex formation. This review highlights one particularly important aspect of plutonium behaviour at the mineral-water interface-the concept of surface-mediated reduction, which describes the reduction of plutonium on a mineral surface. It provides a conceptual model for and evidence supporting or refuting each proposed mechanism for surface-mediated reduction including (i) radiolysis at the mineral surface, (ii) electron transfer via ferrous iron or manganese in the mineral structure, (iii) electron shuttling due to the semiconducting properties of the mineral, (iv) disproportionation of Pu(v), (v) facilitation by proton exchange sites, (vi) stabilisation of Pu(iv) due to the increased concentration gradient within the electrical double layer, and (vii) a Nernstian favourability of Pu(iv) surface complexes and colloids. It also provides new perspectives on future research directions.

Plutonium (Pu) isotopes were first determined in surface and core sediment samples collected from the northern North Yellow Sea (NYS) to elucidate their source terms and deposition process as well as the response to catchment environmental changes of inflow rivers. 240 Pu/ 239 Pu atom ratios in all sediments showed the typical global fallout value of ∼0.18 without any influences from the nuclear weapons tests conducted recently in the North Korea or early in the Pacific Proving Ground. The large variation of 239+240 Pu activities (0.022-0.515 mBq/g) observed in surface sediments should be mainly attributed to the re-suspension and transportation of fine sediments influenced by the Liaonan Costal Current. Based on the two 239+249 Pu depth profiles with easily observed onset fallout levels (1952) and global fallout peaks (1963), 239+240 Pu served as a valid time mark in the coastal sedimentary system. Riverine input Pu contributed only 15-27% to the total global fallout inventory (92.5-108.8 Bq/m 2 ) in the northern NYS, much lower than that in the Yangtze River estuary (77-80%), indicating a better soil conservation in the northeast China due to higher forest coverage compared to the Yangtze River's drainage basin. The increase of riverine input Pu after 1980s reflected the more intense soil erosion degree caused by the land use and cover change due to the increment of human activities in the northeast China at the same period. Our results demonstrated that plutonium is a good indicator for studying sedimentary process and its response to the environment in the coastal area., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In order to assess the impact of the Fukushima derived Pu isotopes on seawater, a new analytical method to rapidly determine Pu isotopes in seawater by SF-ICP-MS including Fe(OH) 2 primary co-precipitation, CaF 2 /LaF 3 secondary co-precipitation and TEVA+UTEVA+DGA extraction chromatographic separation was established. High concentration efficiency (~100%) and high U decontamination factor (~10 7 ) were achieved. The plutonium chemical recoveries were 74-88% with the mean of 83 ± 5%. The precisions for both 240 Pu/ 239 Pu atom ratios and 239+240 Pu activity concentrations were less than 5% when 15 L of seawater samples with the typical 239+240 Pu activity of the Northwest Pacific were measured. It just needs 12 hours to determine plutonium using this new method. The limit of detection (LOD) for 239 Pu and 240 Pu were both 0.08 fg/mL, corresponding to 0.01 mBq/m 3 for 239 Pu and 0.05 mBq/m 3 for 240 Pu when a 15 L volume of seawater was measured. This method was applied to determine the seawater samples collected 446-1316 km off the FDNPP accident site in the Northwest Pacific in July of 2013. The obtained 239+240 Pu activity concentrations of 1.21-2.19 mBq/m 3 and the 240 Pu/ 239 Pu atom ratios of 0.198-0.322 suggested that there was no significant Pu contamination from the accident to the Northwest Pacific.

In 2008, Serandour et al. reported on their in vitro experiment involving rat plasma samples obtained after an intravenous intake of plutonium citrate. Different amounts of DTPA were added to the plasma samples and the percentage of low-molecular-weight plutonium measured. Only when the DTPA dosage was three orders of magnitude greater than the recommended 30 μmol/kg was 100% of the plutonium apparently in the form of chelate. These data were modeled assuming three competing chemical reactions with other molecules that bind with plutonium. Here, time-dependent second-order kinetics of these reactions are calculated, intended eventually to become part of a complete biokinetic model of DTPA action on actinides in laboratory animals or humans. The probability distribution of the ratio of stability constants for the reactants was calculated using Markov Chain Monte Carlo. These calculations substantiate that the inclusion of more reactions is needed in order to be in agreement with known stability constants.

The use of uranium and to a minor extent plutonium as fuel for nuclear energy production or as components in military applications is under increasing public pressure. Uranium is weakly radioactive in its natural isotopy but its chemical toxicity, combined with its large scale industrial utilization, makes it a source of concern in terms of health impact for workers and possibly the general population. Plutonium is an artificial element that exhibits both chemical and radiological toxicities. So far, uranium (under its form uranyl, U(vi)) or plutonium (as Pu(iv)) decorporation or protecting strategies based on molecular design have been of limited efficiency to remove the actinide once incorporated after human exposure. In all cases, after human exposure, plutonium and uranium are retained in main target organs (liver, kidneys) as well as skeleton although they exhibit differences in their biodistribution. Polymers could represent an alternative strategy as their tropism for specific target organs has been reported. We recently reported on the complexation properties of methylcarboxylated polyethyleneimine (PEI-MC) with uranyl. In this report we extend our work to methylphosphonated polyethyleneimine (PEI-MP) and to the comparison between actinide oxidation states +IV (thorium) and +VI (uranyl). As a first step, thorium (Th(iv)) was used as a chemical surrogate of plutonium because of the difficulty in handling the latter in the laboratory. For both cations, U(vi) and Th(iv), the uptake curve of PEI-MP was recorded. The functionalized PEI-MP exhibits a maximum loading capacity comprised of between 0.56 and 0.80 mg of uranium (elemental) and 0.15-0.20 mg of thorium (elemental) per milligram of PEI-MP. Complexation sites of U(vi) and Th(iv) under model conditions close to physiological pH were then characterized with a combination of Fourier transform Infra Red (FT-IR) and Extended X-Ray Absorption Fine Structure (EXAFS). Although both cations exhibit different coordination modes, similar structural parameters with phosphonate functions were obtained. For example, the coordination sites are composed of fully monodentate phosphonate functions of the polymer chains. These physical chemical data represent a necessary basic chemistry approach before envisioning further biological evaluations of PEI-MP polymers towards U(vi) and Pu/Th(iv) contamination.

The role of humic acid concentration in the microbially-mediated reductive solubilization of Pu(IV) polymers remains unclear until now. The effects of humic concentration (0-150.5mg/L) on the rate and extent of reduction of polymeric Pu(IV) were studied under anaerobic and pH 7.2 conditions. The results show that Shewanella putrefaciens, secreting flavins as endogenous electron shuttles, cannot notably stimulate the reduction of polymeric Pu(IV). In the presence of humic acids, the reduction rate of polymeric Pu(IV) increased with increasing humic concentrations (0-15.0mg/L): e.g., a 102-fold increase from 4.1×10 -15 (HA=0) to 4.2×10 -13 mol Pu(III) aq /h (HA=15.0mg/L). The bioreduced humic acids by S. putrefaciens facilitated the extracellular electron transfer to Pu(IV) polymers and thus the reduction of polymeric Pu(IV) to Pu(III) aq became thermodynamically favorable. However, the reduction rate did not increase but decrease with increasing humic concentrations from 15.0 to 150.5mg/L. Humic coatings formed on the polymer surfaces at relatively high humic concentrations limited the electron transfer to the polymers and thus decreased the reduction rate. The finding of the dynamic role of humic acids in the bioreductive solubilization may be helpful in evaluating Pu mobility in the geosphere., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This work tested the feasibility of a silicon-on-insulator microdosimeter, which mimics the size and shape of specific cells within the human body, to determine dose equivalent from neutron irradiation. The microdosimeters were analyzed in terms of their basic diode characteristics, i.e., leakage current as a function of bias voltage. Lineal energy spectra were acquired using two different converter layers placed atop the microdosimeter: a tissue-substitute converter made from high-density polyethylene, and a boron converter consisting of epoxy coated with boron powder. The spectra were then converted into absorbed dose and dose equivalent. Experimental results were compared to Monte Carlo simulations of the neutron irradiations, revealing good agreement. Uncertainty in the dose equivalent determinations was 7.5% when using the cell-shaped microdosimeter with the tissue-substitute converter and 13.1% when using the boron converter. This work confirmed that the SOI approach to cell-mimicking microdosimetry is feasible.

Plutonium plays an important role within nuclear waste materials because of its long half-life and high radiotoxicity. The aim of this study was to investigate with high spatial resolution the reactivity of the more oxidized forms of Pu(V,VI) within Opalinus Clay (OPA) rock, a heterogeneous, natural argillaceous rock considered as a potential repository host. A combination of synchrotron based X-ray microprobe and bulk techniques was used to study the spatial distribution and molecular speciation of Pu within OPA after diffusion and sorption processes. Microscopic chemical images revealed a pronounced impact of geochemical heterogeneities concerning the reactivity of the natural barrier material. Spatially resolved X-ray absorption spectroscopy documented a reduction of the highly soluble Pu(V,VI) to the less mobile Pu(IV) within the argillaceous rock material, while bulk investigations showed second-shell scattering contributions, indicating an inner-sphere sorption of Pu on OPA components. Microdiffraction imaging identified the clay mineral kaolinite to play a key role in the immobilization of the reduced Pu. The findings provide strong evidence that reduction and immobilization do not occur as linked processes on a single reactive phase but as decoupled, subsequent, and spatially separated reactions involving different phases of the OPA.

The potential consequences of a major radiological event are not only large-scale external radiation exposure of the population, but also uncontrolled dissemination of, and internal contamination with, radionuclides. When planning an emergency response to radiological and nuclear incidents, one must consider the need for not only post-exposure treatment for contaminated individuals, but also prophylactic measures to protect the workforce facing contaminated areas and patients in the aftermath of such events. In addition to meeting the desired criteria for post-exposure treatments such as safety, ease of administration, and broad-spectrum efficacy against multiple radionuclides and levels of challenge, ideal prophylactic countermeasures must include rapid onset; induce minimal to no performance-decrementing side effects; be compatible with current military Chemical, Biological, Radiological, Nuclear, and Explosive countermeasures; and require minimal logistical burdens. Hydroxypyridinone-based actinide decorporation agents have shown the most promise as decorporation strategies for various radionuclides of concern, including the actinides plutonium and americium. The studies presented here probe the extent of plutonium decorporation efficacy for two chelating agents, 3,4,3-LI(1,2-HOPO) and 5-LIO(Me-3,2-HOPO), from early pre-exposure time points to a delay of up to 7 days in parenteral or oral treatment administration, i.e., well beyond the initial hours of emergency response. Despite delayed treatment after a contamination event, both ligands clearly enhanced plutonium elimination through the investigated 7-day post-treatment period. In addition, a remarkable prophylactic efficacy was revealed for 3,4,3-LI(1,2-HOPO) with treatment as early as 48 h before the plutonium challenge. This work provides new perspectives in the indication and use of experimental actinide decorporation treatments., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

The effect of citric acid (CA), desferrioxamine B (DFOB), fulvic acid (FA), and humic acid (HA) on plutonium (Pu) sorption to goethite was studied as a function of organic carbon concentration and pH using batch sorption experiments at 5 mg C ·L -1 and 50 mg C ·L -1 natural organic matter (NOM), 10 -9 -10 -10 M 238 Pu, and 0.1 g·L -1 goethite concentrations, at pH 3, 5, 7, and 9. Low sorption of ligands coupled with strong Pu complexation decreased Pu sorption at pH 5 and 7, relative to a ligand-free system. Conversely, CA, FA, and HA increased Pu sorption to goethite at pH 3, suggesting ternary complex formation or, in the case of humic acid, incorporation into HA aggregates. Mechanisms for ternary complex formation were characterized by Fourier transform infrared spectroscopy in the absence of Pu. CA and FA demonstrated clear surface interactions at pH 3, HA appeared unchanged suggesting HA aggregates had formed, and no DFOB interactions were observed. Plutonium sorption decreased in the presence of DFOB (relative to a ligand free system) at all pH values examined. Thus, DFOB does not appear to facilitate formation of ternary Pu-DFOB-goethite complexes. At pH 9, Pu sorption in the presence of all NOM increased relative to pH 5 and 7; speciation models attributed this to Pu(IV) hydrolysis competing with ligand complexation, increasing sorption. The results indicate that in simple Pu-NOM-goethite ternary batch systems, NOM will decrease Pu sorption to goethite at all but particularly low pH conditions.

Plutonium (Pu) intake by inhalation is one of the major potential consequences following an accident in the nuclear industry or after improvised nuclear device explosion. Macrophages are essential players in retention and clearance of inhaled compounds. However, the extent to which these phagocytic cells are involved in these processes highly depends on the solubility properties of the Pu deposited in the lungs. Our objectives were to develop an in vitro model representative of the human pulmonary macrophage capacity to internalize and release Pu compounds in presence or not of the chelating drug diethylenetriaminepentaacetate (DTPA). The monocyte cell line THP-1 was used after differentiation into macrophage-like cells. We assessed the cellular uptake of various forms of Pu which differ in their solubility, as well as the release of the internalized Pu. Results obtained with differentiated THP-1 cells are in good agreement with data from rat alveolar macrophages and fit well with in vivo data. In both cell types, Pu uptake and release depend upon Pu solubility and in all cases DTPA increases Pu release. The proposed model may provide a good complement to in vivo animal experiments and could be used in a first assessment to predict the fraction of Pu that could be potentially trapped, as well as the fraction available to chelating drugs., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: In the case of a nuclear or radiological incident, there is a risk of external and internal contamination with radionuclides in addition to external irradiation. There is no consensus whether decorporation treatment should be initiated right away on spec or pending the results of internal dosimetry to determine the indication. Method: Based on biokinetic models for plutonium-239, americium-241 and cesium-137, the efficacy of a decorporation treatment using DTPA or Prussian blue was simulated depending on the initiation time and the duration of treatment for different invasion pathways and physicochemical properties of the inhaled compounds. Results: For the same level of radioactivity incorporated, the committed effective dose increases with the speed of the invasion process. The impact of the initiation time of a decorporation treatment is particularly important when the absorption of the radionuclide is fast. Even if started early after incorporation, the therapeutic efficacy is less for americium-241 or cesium-137 compared to plutonium-239. Therapeutic efficacy increases with treatment duration up to about 90 days for plutonium-239 and cesium-137, whereas a prolongation of the treatment over this limit may further enhance efficacy in the case of americium-241. Conclusion: In the case of a nuclear incident, several fractions with different but a priori unknown physicochemical properties may be inhaled. Thus, decorporation therapy should be started as soon as possible after the incorporation of the radionuclide(s), as a loss of efficacy caused by a delay of treatment initiation possibly cannot be compensated later on. Treatment should be pursued for several months., (© Georg Thieme Verlag KG Stuttgart · New York.)

Evaluation of continuous air monitors in the presence of a plutonium aerosol is time intensive, expensive, and requires a specialized facility. The Radiation Protection Services Group at Los Alamos National Laboratory has designed a Dynamic Radioactive Source, intended to replace plutonium aerosol challenge testing. The Dynamic Radioactive Source is small enough to be inserted into the sampler filter chamber of a typical continuous air monitor. Time-dependent radioactivity is introduced from electroplated sources for real-time testing of a continuous air monitor where a mechanical wristwatch motor rotates a mask above an alpha-emitting electroplated disk source. The mask is attached to the watch's minute hand, and as it rotates, more of the underlying source is revealed. The measured alpha activity increases with time, simulating the arrival of airborne radioactive particulates at the air sampler inlet. The Dynamic Radioactive Source allows the temporal behavior of puff and chronic release conditions to be mimicked without the need for radioactive aerosols. The new system is configurable to different continuous air monitor designs and provides an in-house testing capability (benchtop compatible). It is a repeatable and reusable system and does not contaminate the tested air monitor. Test benefits include direct user control, realistic (plutonium) aerosol spectra, and iterative development of continuous air monitor alarm algorithms. Data obtained using the Dynamic Radioactive Source has been used to elucidate alarm algorithms and to compare the response time of two commercial continuous air monitors.

Plants have demonstrated a great potential to remove toxic elements from soils and solutions and been successfully used for phytoremediation of important radionuclides. Uptake potential of vetiver plants (V. zizanoides) for the remediation of (239)Pu in hydroponic and soil conditions was studied in the present work. High efficiency of V. zizanoides for the removal of (239)Pu was recorded with 66.2% being removed from the hydroponic solution after 30 days. However, remediation of (239)Pu from soil was limited. Remediation of (239)Pu from soil was increased with the addition of chelating agents citric acid (CA) and diethylenetriaminepentaacetic acid (DTPA). Accumulation of (239)Pu was recorded higher in roots than shoots, however its translocation from roots to shoots increased in the presence of chelators in hydroponic as well as soil conditions. DTPA was found more effective than CA showing higher translocation index (TI). Increase in TI was observed 8 and 6 times in the solution and soil respectively when plants were exposed to (239)Pu-DTPA in comparison to only (239)Pu. The present study demonstrates that V. zizanoides plant is a potential plant for phytoremediation of (239)Pu., (Copyright © 2016 Elsevier Inc. All rights reserved.)

An understanding of the "bioavailability" of disseminated radiocontaminants is a necessary adjunct in order to tailor treatment and to calculate dose. A simple test has been designed to predict the bioavailability of different actinide forms likely to be found after dissemination of radioactive elements by dispersal devices or nuclear reactor incidents. Plutonium (Pu) or Americium (Am) nitrate or MOX (U,PuO2) are immobilized in culture wells using a static gel phase simulating biological compartments (lung, wound, etc.). Gels are incubated in a fluid phase representing physiological media (plasma, sweat, etc.). Transfer of radionuclide from static to fluid phase reflects contaminant bioavailability. After 48 h of incubation in physiological saline, Am transfer from static to fluid phase was greater than for Pu (70% vs. 15% of initial activity). Transfer of Pu or Am was markedly less from the oxide form of the two elements (1% Am and 0.05% Pu transferred). Medium representing intracellular lysosomal fluid (pH 4) increased transfer of Pu and Am, whereas culture medium including serum reduced actinide transfer. Actinide transfer was also reduced by elements of the extracellular matrix present in the static gel phase. Increasing DTPA concentrations (5 to 500 μM) to the fluid phase significantly enhanced transfer of Pu and Am. Although this agarose gel cannot fully represent in vivo complexity, this simple test can be used to investigate and predict the behavior in vivo of radiocontaminants to support medical treatments and medical forensic investigations.

Pu(IV) and Pu(V) sorption to goethite was investigated over a concentration range of 10(-15)-10(-5) M at pH 8. Experiments with initial Pu concentrations of 10(-15) - 10(-8) M produced linear Pu sorption isotherms, demonstrating that Pu sorption to goethite is not concentration-dependent across this concentration range. Equivalent Pu(IV) and Pu(V) sorption Kd values obtained at 1 and 2-week sampling time points indicated that Pu(V) is rapidly reduced to Pu(IV) on the goethite surface. Further, it suggested that Pu surface redox transformations are sufficiently rapid to achieve an equilibrium state within 1 week, regardless of the initial Pu oxidation state. At initial concentrations >10(-8) M, both Pu oxidation states exhibited deviations from linear sorption behavior and less Pu was adsorbed than at lower concentrations. NanoSIMS and HRTEM analysis of samples with initial Pu concentrations of 10(-8) - 10(-6) M indicated that Pu surface and/or bulk precipitation was likely responsible for this deviation. In 10(-6) M Pu(IV) and Pu(V) samples, HRTEM analysis showed the formation of a body centered cubic (bcc) Pu4O7 structure on the goethite surface, confirming that reduction of Pu(V) had occurred on the mineral surface and that epitaxial distortion previously observed for Pu(IV) sorption occurs with Pu(V) as well.

Based on the data from the literature the authors analyzed the methods used for the estimation of the risks of plutonium-contaminated areas. The analysis was based on the published data on the measured plutonium concentrations in the air and soil. To calculate plutonium concentrations in the near-surface air layer above the contaminated area a modification of the method of the load estimation from the mass was proposed: instead of the average plutonium specific activity in soil the authors suggested the use of the soil coefficient which consists of the sum of specific activities of every respirable fraction (size 0.05 to 10 μm) multiplied by the percentage of its activity in the total activity of the soil sample. Verification of the proposed method on independent data showed that the calculated values approached the measured ones.

The interaction natures between Pu and different ligands in several plutonyl (VI) complexes are investigated by performing topological analyses of electron density. The geometrical structures in both gaseous and aqueous phases are obtained with B3LYP functional, and are generally in agreement with available theoretical and experimental results when combined with all-electron segmented all-electron relativistic contracted (SARC) basis set. The Pu- O y l bond orders show significant linear dependence on bond length and the charge of oxygen atoms in plutonyl moiety. The closed-shell interactions were identified for Pu-Ligand bonds in most complexes with quantum theory of atoms in molecules (QTAIM) analyses. Meanwhile, we found that some Pu-Ligand bonds, like Pu-OH(-), show weak covalent. The interactive nature of Pu-ligand bonds were revealed based on the interaction quantum atom (IQA) energy decomposition approach, and our results indicate that all Pu-Ligand interactions is dominated by the electrostatic attraction interaction as expected. Meanwhile it is also important to note that the quantum mechanical exchange-correlation contributions can not be ignored. By means of the non-covalent interaction (NCI) approach it has been found that some weak and repulsion interactions existed in plutonyl(VI) complexes, which can not be distinguished by QTAIM, can be successfully identified.

With regard to environmental monitoring of certain nuclear facilities, pentavalent actinides, in particular neptunium and plutonium, play a key role, as the chief soluble, mobile forms of actinides. In the past five years, investigations carried out by hyphenating capillary electrophoresis to ICP-MS (CE-ICP-MS) have allowed a number of hitherto unknown thermodynamic data to be determined for Np(V) and Pu(V) interactions with the chief environmentally abundant anions. For the first time, data were provided for Pu(V) interactions with carbonate, sulfate, oxalate, chloride, and nitrate ions, allowing the Np(V)/Pu(V) analogy to be verified experimentally. Knowledge of Np(V) chemistry, especially in carbonate, and sulfate media, was also refined. These CE-ICP-MS studies, combined with some earlier findings, have brought about a renewal in the knowledge of An(V) chemistry in solution., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The geochemical behavior of Pu strongly depends on its redox speciation. In this study, we investigated Pu sorption onto Na-illite, a relevant component of potential host rocks for high-level nuclear waste repositories, under anaerobic conditions. When contacting Pu (85% Pu(IV), 11% Pu(V), and 4% Pu(III); 8 × 10(-11) < [Pu]tot/M < 10(-8)) with illite in 0.1 M NaCl at pH between 3 and 10, Pu uptake was characterized by log Rd > 4 (Rd: distribution coefficient in L kg(-1)). Small amounts of aqueous Pu(V) were detected in solution on contact with illite after 1 week, which is not expected to be stable at the measured redox potentials (Eh) in our experiments. This observation suggests time-dependent reduction of Pu(V) to Pu(IV). After one year, log Rd values had increased compared to those after 1 week due to the reduction of weakly adsorbing Pu(V). For pH < 5, Pu(IV) and Pu(III) coexisted in solution under our experimental conditions, showing that Pu(IV) reduction to Pu(III) occurred in the illite suspension. Taking (i) surface complexation constants determined for Eu(III)-illite interaction (with redox-insensitive Eu(III) as a chemical analogue to Pu(III)), (ii) the known constant for Pu(III)-Pu(IV) redox transition, and (iii) measured Eh and pH, overall Pu uptake was well-predicted.

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can potentially contribute to the exposure of biota and humans. The diffusive gradients in thin films technique is introduced here for in-situ measurements of Pu bioavailability and speciation. A diffusion cell constructed for laboratory experiments with Pu and the newly developed protocol make it possible to simulate the environmental behavior of Pu in model solutions of various chemical compositions. Adjustment of the oxidation states to Pu(IV) and Pu(V) described in this protocol is essential in order to investigate the complex redox chemistry of plutonium in the environment. The calibration of this technique and the results obtained in the laboratory experiments enable to develop a specific DGT device for in-situ Pu measurements in freshwaters. Accelerator-based mass-spectrometry measurements of Pu accumulated by DGTs in a karst spring allowed determining the bioavailability of Pu in a mineral freshwater environment. Application of this protocol for Pu measurements using DGT devices has a large potential to improve our understanding of the speciation and the biological transfer of Pu in aquatic ecosystems.

Pu concentrations in wetland surface sediments collected downstream of a former nuclear processing facility in F-Area of the Savannah River Site (SRS), USA, were ∼2.5 times greater than those measured in the associated upland aquifer sediments; similarly, the Pu concentration solid/water ratios were orders of magnitude greater in the wetland than in the low-organic matter content aquifer soils. Sediment Pu concentrations were correlated to total organic carbon and total nitrogen contents and even more strongly to hydroxamate siderophore (HS) concentrations. The HS were detected in the particulate or colloidal phases of the sediments but not in the low molecular weight fractions (<1000 Da). Macromolecules which scavenged the majority of the potentially mobile Pu were further separated from the bulk mobile organic matter fraction ("water extract") via an isoelectric focusing experiment (IEF). An electrospray ionization Fourier-transform ion cyclotron resonance ultrahigh resolution mass spectrometry (ESI FTICR-MS) spectral comparison of the IEF extract and a siderophore standard (desferrioxamine; DFO) suggested the presence of HS functionalities in the IEF extract. This study suggests that while HS are a very minor component in the sediment particulate/colloidal fractions, their concentrations greatly exceed those of ambient Pu, and HS may play an especially important role in Pu immobilization/remobilization in wetland sediments.

Understanding how plutonium (Pu) doping affects the crystalline zircon structure is very important for risk management. However, so far, there have been only a very limited number of reports of the quantitative simulation of the effects of the Pu charge and concentration on the phase transition. In this study, we used density functional theory (DFT), virtual crystal approximation (VCA), and two-dimensional correlation analysis (2D-CA) techniques to calculate the origins of the structural and electronic transitions of Zr1-cPucSiO4 over a wide range of Pu doping concentrations (c=0-10mol%). The calculations indicated that the low-angular-momentum Pu-fxy-shell electron excites an inner-shell O-2s(2) orbital to create an oxygen defect (VO-s) below c=2.8mol%. This oxygen defect then captures a low-angular-momentum Zr-5p(6)5s(2) electron to form an sp hybrid orbital, which exhibits a stable phase structure. When c>2.8mol%, each accumulated VO-p defect captures a high-angular-momentum Zr-4dz electron and two Si-pz electrons to create delocalized Si(4+)→Si(2+) charge disproportionation. Therefore, we suggest that the optimal amount of Pu cannot exceed 7.5mol% because of the formation of a mixture of ZrO8 polyhedral and SiO4 tetrahedral phases with the orientation (10-1). This study offers new perspective on the development of highly stable zircon-based solid solution materials., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Actinyl(VI, V) (An = U, Np and Pu) complexes of the recently reported hybrid macrocycle, cyclo[1]furan[1]pyridine[4]pyrrole (denoted as H4L), have been studied using density functional theory in combination with the small-core scalar-relativistic effective core potentials and corresponding (14s13p10d8f6g)/[ 10s9p5d4f3g] basis sets in the segmented contraction scheme. On the basis of our calculations, the pyrrole nitrogen atoms that possess the shortest An-L bonds and strongest basicity are the main donor atoms that contribute to the formation of actinyl(VI, V) complexes. The natural population analysis (NPA) suggests higher ligand-to-actinyl charge transfer in the actinyl(VI) complexes than in their actinyl(V) analogues, which account for the higher decomposition energies of the former. A significant actinide-to-ligand spin density delocalization in the uranyl(V) and neptunyl(V) complexes was observed owing to the redistribution of spin density caused by complexation. A thermodynamic analysis indicates that the formation of the actinyl(VI, V) complexes are exothermic reactions in CH2Cl2 solvent, where the uranyl cations show the highest selectivity. In aqueous solution containing chloride ions, for complexing with macrocycle H4L, the plutonyl(VI) and uranyl(V) cations possess the highest selectivity among actinyl(VI) and (V) cations, respectively. This work can shed light on the design of macrocycle complexes for actinide recognition and extraction in the future.

The speciation of U and Pu in soil and concrete from Rocky Flats and in particles from soils from Chernobyl, Hanford, Los Alamos, and McGuire Air Force Base and bottom sediments from Mayak was determined by a combination of X-ray absorption fine structure (XAFS) spectroscopy and X-ray fluorescence (XRF) element maps. These experiments identify four types of speciation that sometimes may and other times do not exhibit an association with the source terms and histories of these samples: relatively well ordered PuO2+x and UO2+x that had equilibrated with O2 and H2O under both ambient conditions and in fires or explosions; instances of small, isolated particles of U as UO2+x, U3O8, and U(VI) species coexisting in close proximity after decades in the environment; alteration phases of uranyl with other elements including ones that would not have come from soils; and mononuclear Pu-O species and novel PuO2+x-type compounds incorporating additional elements that may have occurred because the Pu was exposed to extreme chemical conditions such as acidic solutions released directly into soil or concrete. Our results therefore directly demonstrate instances of novel complexity in the Å and μm-scale chemical speciation and reactivity of U and Pu in their initial formation and after environmental exposure as well as occasions of unexpected behavior in the reaction pathways over short geological but significant sociological times. They also show that incorporating the actual disposal and site conditions and resultant novel materials such as those reported here may be necessary to develop the most accurate predictive models for Pu and U in the environment.