Electrochemistry of thorium in LiCl-KCl eutectic melts

This work presents a study of the electrochemical properties of Th chloride ions dissolved in a molten LiCl-KCl eutectic, in a temperature range of 693-823 K. Transient electrochemical techniques such as cyclic voltammetry and chronopotentiommetry have been used in order to investigate the reduction mechanism on a tungsten electrode and the diffusion coefficient of dissolved Th ions. All techniques showed that only one valence state was stable in the melt. The reduction into Th metal was found to occur according to a one-step mechanism, through an irreversible reaction controlled by a nucleation process which requires an overpotential of several 100 mV. At 723 K, the diffusion coefficient is DTh(723K) = 3.7 ± 0.2·10-5 cm2.s-1. EMF measurements indicated that, at 723 K, the standard apparent potential is *0ThCl4 /Th) E (723 K) = - 2.582 V vs. Cl2/Cl-, and the activity coefficient γThCl4(723 K) = 8·10-3 on the mole fraction scale (based on a pure liquid reference state)

Investigation of electrorefining of metallic alloy fuel onto solid Al cathodes

This work concerned the electrorefining of UZr and UPuZr alloys on a solid aluminium cathode, in the LiCl-KCl eutectic melt containing U3+, Pu3+, Np3+, Zr2+ or Zr 4+, Am3+, Nd3+, Y3+, Ce3+ and Gd3+ chlorides. During constant current electrolyses, the use of a cathodic cut-off potential (-1.25 V vs. Ag/AgCl) allowed to selectively deposit actinides (mainly U), while lanthanides remainedin the salt. The aim was to determine the maximal load achievable on a single aluminium electrode. The total exchange charge was 4300 C, which represents the deposition of 3.72 g of actinides in 4.17 g Al, yielding a composition of 44.6 wt% An in Al. It was shown that the melting of the cathode contributed to increase the total amount of actinides deposited on the aluminium

Role of self-irradiation defects on the ageing of 239PuCoGa5

6 pages, 18 referencesInternational audienceLow-temperature accumulation and annealing experiments, in conjunction with electrical resistivity and critical current density measurements, were used to study the ageing of the actinide superconductor PuCoGa5. These measurements reveal that 2-nm sized non-superconducting point-like regions are the main damage formed during room temperature ageing; smaller point-like defect were irrelevant to transport properties. Defect sizes and densities deduced from experiment agree with Transmission Electron Micoscopy observations

Tris‐{hydridotris(1‐pyrazolyl)borato}actinide Complexes: Synthesis, Spectroscopy, Crystal Structure, Bonding Properties and Magnetic Behaviour

The isostructural compounds of the trivalent actinides uranium, neptunium, plutonium, americium, and curium with the hydridotris(1-pyrazolyl)borato (Tp) ligand An[η$_{3}$-HB(N$_{2}$C$_{3}$H$_{3}$)$_{3}$]$_{3}$ (AnTp$_{3}$) have been obtained through several synthetic routes. Structural, spectroscopic (absorption, infrared, laser fluorescence) and magnetic characterisation of the compounds were performed in combination with crystal field, density functional theory (DFT) and relativistic multiconfigurational calculations. The covalent bonding interactions were analysed in terms of the natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) models

Tris‐{hydridotris(1‐pyrazolyl)borato}actinide Complexes: Synthesis, Spectroscopy, Crystal Structure, Bonding Properties and Magnetic Behaviour

The isostructural compounds of the trivalent actinides uranium, neptunium, plutonium, americium, and curium with the hydridotris(1-pyrazolyl)borato (Tp) ligand An[η$_{3}$-HB(N$_{2}$C$_{3}$H$_{3}$)$_{3}$]$_{3}$ (AnTp$_{3}$) have been obtained through several synthetic routes. Structural, spectroscopic (absorption, infrared, laser fluorescence) and magnetic characterisation of the compounds were performed in combination with crystal field, density functional theory (DFT) and relativistic multiconfigurational calculations. The covalent bonding interactions were analysed in terms of the natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) models

Pressure Effects on Neptunium Monochalcogenides NpS and NpSe

We present high pressure resistivity at low temperature of NpS and NpSe systems up to 10 and 25 GPa respectively. These systems are reported as type II antiferro- magnets at 25 and 38 K respectively presenting bad metal aspects. In the magnetic domain, they present semiconducting features with high resistivity. When applying pressure, we observe an increase of TN from 25 to 50 K for NpS while magnetic order temperature decreases for NpSe from 38 K to 20 K.JRC.E.6-Actinides researc

High Pressure Effect on Superconducting State of Thorium Metal

Here we report pressure studies on thorium metal by electrical resistivity in the normal and in the superconducting state. We determined Tc(p) diagram and critical field Hc(T) up to 13 GPa and down to 0.4 K. We observe a decrease in Tc and Hc with the pressure applied. We confirm the change of regime around 10 GPa. But we observe a different behavior of superconducting state versus pressure than previously reported.JRC.E.6-Actinides researc

High Pressure X-Ray Diffraction Experiments on NpS and PuS up to GPa.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

High Pressure Behaviour of NpTe.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

Photoemission Study of Delta-Pu with Am Doping

Photoelectron spectroscopy studies indicate that the degree of 5f-localization in d-Pu remains preserved despite a large volume expansion, induced by Am doping.JRC.E.6-Actinides researc