[en] This paper discusses the results of a study of actinide surrogates in a nuclear borosilicate glass to understand the effect of processing conditions (temperature and oxidizing versus reducing conditions) on the solubility limits of these elements. The incorporation of cerium oxide, hafnium oxide, and neodymium oxide in this borosilicate glass was investigated. Cerium is a possible surrogate for tetravalent and trivalent actinides, hafnium for tetravalent actinides, and neodymium for trivalent actinides. The material homogeneity was studied by optical, scanning electron microscopy. Cerium L_III XANES spectroscopy showed that the Ce³⁺/Ce_total ratio increased from about 0.5 to 0.9 as the processing temperature increased from 1100 to 1400 deg. C. Cerium L_III XANES spectroscopy also confirmed that the increased Ce solubility in glasses melted under reducing conditions was due to complete reduction of all the cerium in the glass. The most significant results pointed out in the current study are that the solubility limits of the actinide surrogates increases with the processing temperature and that Ce³⁺ is shown to be more soluble than Ce⁴⁺ in this borosilicate glass

[en] The aim of this work is to characterise the retention properties of apatites, studied as potential inert matrices, towards the long-lived fission product ⁹⁹Tc (T=210 000 years) in radioactive waste disposal. The study was made using two stable homologous elements of Tc: molybdenum which has the same mass as technetium, and rhenium which is the chemical analogue of Tc. These elements were introduced in apatite samples by ion implantation and their profiles were determined by Rutherford backscattering spectroscopy (RBS). The coupling of X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES) analysis showed the oxidation of molybdenum and rhenium during annealing. Using these results on Mo and Re behaviour, assumptions were made on the migration of technetium

[en] The main scope of the LN1 laboratory in ATALANTE facility is the chemical and physico-chemical study of transuranic samples to understand the behavior of compounds of actinide with selective ligands at a molecular scale. The main techniques implemented in this laboratory are the following ones: Nuclear Magnetic Resonance spectrometer (400 MHz shielded magnetic field), a four circle X-ray diffractometer for single crystals, a microcalorimeter to the measurement of low heats of reactions, a Time Resolved Laser-induced spectro-fluorimeter, vibrational spectrometers: FTIR and Raman, an Electro-spray Ionisation Mass spectrometer. Specific glove boxes have been built for each technique to work on radio elements with safety conditions and allow the analysis of samples in different states (aqueous and organic liquids, gels, solids). (authors)

[en] The crystal structure of new complexes of praseodymium(III) and ytterbium(III) (elements from the initial and final parts of the lanthanide series), namely, [Pr(NO₃)₃ (Terpy)((CH₃)₂CO)] (I) and [Yb(NO₃)₂(Terpy)(H₂O)₂]NO₃ . 2H₂O (II), is investigated. The structure of compound I consists of [Pr(NO₃)₃(Terpy)((CH₃)₂CO)] neutral complexes. The coordination number of the praseodymium atom is 10. The coordination polyhedron of the praseodymium atom can be described as a distorted bicapped tetragonal antiprism. The structure of compound II is composed of [Yb(NO₃)₂(Terpy)(H₂O)₂]⁺ cationic complexes, nitrate anions, and molecules of crystallization water. The structural components are joined together via a three-dimensional system of hydrogen bonds. The coordination polyhedron of the ytterbium atom can be represented as a distorted tricapped trigonal prism. The coordination number of the ytterbium atom is 9

[en] Amido complexes of d and f transition metals have been the subject of tremendous interest lately. In particular, uranium amido complexes allow scanning a wide range of U oxidation states. As a consequence, both structural and electronic evolutions within complex series are to be probed by XAS, especially when single crystal are lacking. We present here a series of homoleptic U(IV) amide species. It involves oligomeric bridging amido complexes (from monomeric to trimeric) in which U-U intra-cluster interaction was probed by uranium L₃ edge measurements. (au)

[en] A new basic Nd³⁺ nitrate, [Nd₆O(OH)₈(H₂O)₁₄(NO₃)₆](NO₃)₂ . 2H₂O (I), is isolated in the crystal form and studied. Compound I differs from the basic Ln nitrates containing [Ln₆O(OH)₈] clusters in that it involves a larger number of water molecules. The incorporation of additional water molecules is accompanied by changes in the coordination environment of one of the three crystallographically independent Nd³⁺ cations. Two cations have coordination polyhedra in the form of a monocapped tetragonal antiprism with a coordination number of 9, and the third cation has a polyhedron in the form of a bicapped tetragonal antiprism with a coordination number of 10

[en] Single crystals of [Th(TMP)₄(DMP)₂]₂[ClO₄]₄ and [UO₂(TMP)(DMP)(NO₃)]₂ have been synthesized and their structures have been determined by X-ray diffraction analysis. The complexes of Th(IV) and U(VI) contain simultaneously both the molecular ligand trimethyl phosphate (TMP) and the anion dimethyl phosphate. The main structural motif in Th(IV) complex is centrosymmetric dimeric cation [Th(TMP)₄(DMP)₂]₂⁴⁺, and in U(VI) it is the neutral centrosymmetric dimeric complex [UO₂(TMP)(DMP)(NO₃)]₂. Coordination polyhedron of Th(IV) is tetragonal antiprism, for U(VI) it is pentagonal bipyramid. The structures are compared with those of other Th(IV) and U(VI) complexes containing other trialkyl phosphates. (orig.)

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[en] Waste management of nuclear fuel represents one of the major environmental concerns of the decade. To recycle fissile valuable materials, intimate knowledge of complexation mechanisms involved in the solvent extraction processes is indispensable. Evolution of the actinide coordination sphere of AnO₂(NO₃)₂TBP-type complexes (an = U, Np, Pu; TBP = tributylphosphate) with the actinide valence state have been probed by XAS at the metal L_III edge. Dramatic changes in the actinide coordination sphere appeared when the An(VI) metal is reduced to An(IV). However, no significant evolution in the actinide environment has been noticed across the series UO₂²⁺, NpO₂²⁺ and PuO₂²⁺. (au)