Neutron-induced fission cross sections of Th 232 and U 233 up to 1 GeV using parallel plate avalanche counters at the CERN n_TOF facility

The neutron-induced fission cross sections of 232 Th and 233 U were measured relative to 235 U in a wide neutron energy range up to 1 GeV (and from fission threshold in the case of 232 Th , and from 0.7 eV in case of 233 U ), using the white-spectrum neutron source at the CERN Neutron Time-of-Flight (n_TOF) facility. Parallel plate avalanche counters (PPACs) were used, installed at the Experimental Area 1 (EAR1), which is located at 185 m from the neutron spallation target. The anisotropic emission of fission fragments were taken into account in the detection efficiency by using, in the case of 233 U , previous results available in EXFOR, whereas in the case of 232 Th these data were obtained from our measurement, using PPACs and targets tilted 45 ° with respect to the neutron beam direction. Finally, the obtained results are compared with past measurements and major evaluated nuclear data libraries. Calculations using the high-energy reaction models INCL + + and ABLA07 were performed and some of their parameters were modified to reproduce the experimental results. At high energies, where no other neutron data exist, our results are compared with experimental data on proton-induced fission. Moreover, the dependence of the fission cross section at 1 GeV with the fissility parameter of the target nucleus is studied by combining those ( p , f ) data with our ( n , f ) data on 232 Th and 233 U and on other isotopes studied earlier at n_TOF using the same experimental setup.Peer ReviewedArticle escrit per 81 autors/autores: D. Tarrío , L. Tassan-Got, I. Duran, L. S. Leong, C. Paradela, L. Audouin, E. Leal-Cidoncha, C. Le Naour, M. Caamaño, A. Ventura, S. Altstadt, J. Andrzejewski, M. Barbagallo, V. Bécares, F. Becvá ˇ ˇr,F. Belloni, E. Berthoumieux, J. Billowes, V. Boccone, D. Bosnar, M. Brugger, M. Calviani, F. Calviño, D. Cano-Ott, C. Carrapiço, F. Cerutti, E. Chiaveri,M. Chin, N. Colonna, G. Cortés, M. A. Cortés-Giraldo, M. Diakaki, C. Domingo-Pardo, N. Dzysiuk, C. Eleftheriadis, A. Ferrari, K. Fraval, S. Ganesan, A. R. García, G. Giubrone, M. B. Gómez-Hornillos, I. F. Gonçalves, E. González-Romero,E. Griesmayer, C. Guerrero, F. Gunsing, P. Gurusamy, D. G. Jenkins, E. Jericha, Y. Kadi, F. Käppeler,† D. Karadimos, P. Koehler, M. Kokkoris, M. Krticka, J. Kroll, C. Langer, C. Lederer, H. Leeb, R. Losito, A. Manousos, J. Marganiec, T. Martínez, C. Massimi, P. F. Mastinu,M. Mastromarco, M. Meaze, E. Mendoza, A. Mengoni, P. M. Milazzo, F. Mingrone, M. Mirea,,† W. Mondalaers, A. Pavlik, J. Perkowski, A. Plompen, J. Praena, J. M. Quesada, T. Rauscher, R. Reifarth, A. Riego, M. S. Robles, F. Roman, C. Rubbia, R. Sarmento, P. Schillebeeckx,S. Schmidt, G. Tagliente, J. L. Tain, A. Tsinganis, S. Valenta, G. Vannini, V. Variale, P. Vaz, R. Versaci, M. J. Vermeulen, V. Vlachoudis, R. Vlastou,A. Wallner, T. Ware, M. Weigand, C. Weiß, T. J. Wright, P. ŽugecPostprint (published version

The CD81 Partner EWI-2wint Inhibits Hepatitis C Virus Entry

Two to three percent of the world's population is chronically infected with hepatitis C virus (HCV) and thus at risk of developing liver cancer. Although precise mechanisms regulating HCV entry into hepatic cells are still unknown, several cell surface proteins have been identified as entry factors for this virus. Among these molecules, the tetraspanin CD81 is essential for HCV entry. Here, we have identified a partner of CD81, EWI-2wint, which is expressed in several cell lines but not in hepatocytes. Ectopic expression of EWI-2wint in a hepatoma cell line susceptible to HCV infection blocked viral entry by inhibiting the interaction between the HCV envelope glycoproteins and CD81. This finding suggests that, in addition to the presence of specific entry factors in the hepatocytes, the lack of a specific inhibitor can contribute to the hepatotropism of HCV. This is the first example of a pathogen gaining entry into host cells that lack a specific inhibitory factor

Quantum molecular dynamics investigations of protactinium (V) fluoro and oxofluoro complexes in solution

International audienceQuantum Molecular Dynamics simulations of protactinium (V) fluoro and oxofluoro complexes in solution were undertaken using density functional theory with generalised gradient approximation (and the ABINIT software package). The complexes were studied in the gas phase (at 0 K) and in solution (at 298 K) with water molecules as the solvent. We characterised all of the systems, taking into account their structures, dissociation energies, bond lengths and formation enthalpies in solution, and explained their relative stabilities. At ambient temperature, the hydrated species PaF 5 , P a F 4 + $Pa{F}_{4}^{+}$ , P a O F 5 2 − $PaO{F}_{5}^{2-}$ , P a O F 4 − $PaO{F}_{4}^{-}$ and PaOF 3 were found to be the most stable (and to exhibit similar stabilities). The calculated formation enthalpies of the complexes are in close agreement with measurements made elsewhere

The speciation of protactinium since its discovery: a nightmare or a path of resilience

International audienceAbstract This review concerns the speciation of protactinium in aqueous solution under its both oxidation states +IV and +V. Emphasis is placed on experimental data obtained at trace level but also in macroscopic amount leading to the determination of thermodynamic and structural data. Thus, the complexation of Pa(V) with mineral acids and organic acids, mainly polyaminocarboxylic acids (iminodiacetic acid [IDA], nitrilotriacetic acid [NTA], ethylenediaminetetraacetic acid [EDTA] and diethylenetriaminepentaacetic acid [DTPA]) are highlighted and compared. The review also includes the actual knowledge about the Pa(IV) aqueous chemistry pinpointing its spectroscopic features.</jats:p

Protactinium(V) in aqueous solution: a light actinide without actinyl moiety

International audienc

Thorium oxide dissolution in HNO3_3-HF mixture: kinetics and mechanism

International audienceThis paper is an attempt to find out thorium oxide dissolution mechanism in HNO3-HF mixture. In a previous paper, several parameters effects on thorium oxide dissolution have been described, with specific focus on hydrofluoric acid effect, which can lead to an increase of the dissolution rate if present in small amount, but precipitates as ThF4 at higher content. Based on this previous study, experimental data were fitted using several dissolution models in order to find out the best one. Finally, a revisited model based on literature and considering the ThF4 formation was proposed. It describes the main steps of dissolution and is able to fit the experimental data for a wide range of solution compositions. This point is crucial since it allows considering an extrapolation of the established model to not-yet-studied conditions

La spéciation des actinides - Pierre angulaire de la chimie dans le cycle du combustible nucléaire

International audienceLa France a opté pour une fermeture du cycle du combustible afin de recycler les matières valorisables et limiter la quantité et la nocivité des déchets radioactifs. Sa mise en oeuvre industrielle est réalisée selon le procédé PUREX (Plutonium, Uranium, Reduction, EXtraction). Cet article présente quelques travaux de recherche récents, dans le but d'améliorer l'état des connaissances de la chimie des actinides en solution d'un point de vue fondamental et en soutien au développement de procédés industriels. Après un rappel des connaissances de base concernant la spéciation des actinides en solution aqueuse, les principales étapes du procédé industriel de traitement/ recyclage du plutonium sont présentées, suivies de quelques exemples récents illustrant l'intérêt de la spéciation pour la compréhension des phénomènes chimiques dans quelques opérations du cycle du combustible nucléaire

Specific Interaction between Uranium Anionic Complexes and the Cations of Bis(trifluoromethylsulfonyl)imide Based Ionic Liquids

The redox properties of uranium­(IV) hexachloro complex have been investigated with a glassy carbon electrode in four bis­(trifluoromethylsulfonyl)­imide (Tf₂N^–) based ionic liquids (ILs): the 1-butyl-3-methylimidazolium ([BuMeIm]⁺), the 1-butyl-2,3-dimethylimidazolium ([BuMe₂Im]⁺), the <i>N</i>-butylmethylpyrrolidinium ([BuMePyr]⁺), and the tributyl-methylammonium ([MeBu₃N]⁺). The cyclic voltammetric analysis has revealed two main redox systems: U^VCl₆^–/U^IVCl₆^2– around 0.2 V and U^IVCl₆^2–/U^IIICl₆^3– around −2 V. The formation of U^VCl₆^–, a non-dioxo uranium­(V) species, can then be observed at the electrode in [Tf₂N]⁻ based ILs. This work also provides evidence of a specific interaction between the uranium anionic species and the IL cations because the standard potentials of both redox couples depend on the IL. The interaction extent has been evaluated by comparison of the IL cation number associated with the uranium anionic complex. For that purpose, the standard potentials of both systems have been measured in the less interacting medium [MeBu₃N]­[Tf₂N] as a function of the [BuMeIm]⁺, [BuMe₂Im]⁺, and [BuMePyr]⁺ concentration. Predominance diagrams for uranium hexachloro complexes, analogous to the Pourbaix diagram, have then been built in [MeBu₃N]­[Tf₂N] depending on the IL cations concentration. The exploitation of these diagrams leads to the conclusion that the interaction is function of the charge of the uranium hexachloro complex (U^VCl₆^– < U^IVCl₆^2– < U^IIICl₆^3–) and the IL cation ([BuMe₂Im]⁺ < [BuMePyr]⁺ < [BuMeIm]⁺). The influence of the IL cation could be correlated to the size and the electropositivity of the IL cation. The association would occur by H-bonding and electrostatic interaction. Ab initio calculations were also carried out to evaluate the strength of the interaction between the anionic uranium­(IV) chloro complex and the IL cations. The results show that [BuMeIm]⁺ interacts the most and [MeBu₃N]⁺ the least with U^IVCl₆^2–, and the magnitude of the interaction is comparable for [BuMe₂Im]⁺ and [BuMePyr]⁺

Comparison of the electrochemical behavior of some Rare Earth Elements in butyl methylpyrrolidinium dicyanamide ionic liquid

International audienceTo evaluate the feasibility of developingan efficient electrochemical separation process for rare earth elements (REE) at room temperature, the electrochemical behavior of some representative REE was evaluated in butyl methylpyrrolidinium dicyanamide (BMPyr-DCA), a room temperature ionic liquid. Because of their chemical properties,their commercial availability and their technological applications, yttrium, lanthanum, neodymium and samarium were selected for this study. The differences intheelectrochemical properties of these elements as trivalent salts in BMDCA solutions were evaluated by cyclic voltammetry using a Pt electrode underanAr atmosphere. For the elements withchemical properties that predict only the reduction in one stage (Y, La and Nd), theresults exhibitedthe simultaneous reduction of BMPyr-DCA and the REE cation andthe corresponding oxidation of the reduced REE at anodic potentials that were dependent on the REE cation. ForSm, a two-stepreduction process from Sm(III) to Sm(II) and from Sm(II) to Sm(0) wasobserved,and a clear cathodic peak wasobserved far from the cathodic electrochemical window limit (-1.38 and-2.25 Vvs Fc/Fc+); only oneanodic peakwasobserved at -0.93 V,amore negative potentialthanfor the other studied REE. The results show the same behavior as observed in other media (aqueous and molecular mediaand molten salts) and allow for the evaluation ofthe possibilityofselectively identifyingthe studied REE in the contextof their differingelectrochemical responses

Double Layer at [BuMeIm][Tf2_2N] Ionic Liquid−Pt or −C Material Interfaces

International audienceThe interface [BuMeIm][Tf2N]/electrode, where [BuMeIm][Tf2N] stands for the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, was characterized by electrochemical impedance spectroscopy at different temperatures and for different electrode materials: platinum (Pt, metallic), glassy carbon (GC, high conductivity), carbon nitride (a-CNx, mean conductivity), and boron-doped diamond (BDD, semiconducting with a quasimetallic character). For Pt, GC, and a-CNx, the behavior of the interface could be described by the same equivalent electrical circuit. In the case of BDD, a parallel combination of Rsc and Csc was introduced into the circuit to take into account the potential drop due to the development of a space charge region within the material. The Mott−Schottky plots have confirmed the polycrystalline semiconductor character of the BDD material, and the boron concentration estimated is fully consistent with the B amount introduced for the synthesis. The variations of the double-layer capacitance as a function of potential were found to be camel shaped for all electrode materials at the highest studied temperature. This is consistent with the prediction of Kornyshev's theory as low values of the packing parameter Gamma were estimated by simulation (lower than 0.33). An increase of the double-layer capacitance is found with the temperature similarly to most of the results obtained for molten salt