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In the context of research on U/minor actinides for nuclear fuel reprocessing in the transmutation process, developments are first studied with surrogates containing uranium and lanthanides to facilitate testing. The tests consist of precipitating and calcining a hydrazinium uranium/cerium oxalate. The structure of this oxalate had not been previously determined, but was necessary to validate the physicochemical mechanisms involved. The present study, firstly demonstrates the structural similarity of the U/Ce oxalate phase (N 2 H 5 ,H) 2.9 U 1.1 Ce 0.9 (C 2 O 4 ) 5 ·10H 2 O, synthesized using a vortex precipitator for continuous synthesis of actinide oxalates, with previously known oxalates, crystallizing in P 6 3 / mmc symmetry, obtained by more classical methods. This fast precipitation process induces massive nucleation of fine powders. Their structural and microstructural determination confirms that the raw and dried phases belong to the same structural family as (NH 4 ) 2 U 2 (C 2 O 4 ) 5 ·0.7H 2 O whose structure was described by Chapelet-Arab in P 6 3 / mmc symmetry, using single crystal data. However, they present an extended disorder inside the tunnels of the structure, even after drying at 100 °C, between water and hydrazinium ions. This disorder is directly related to the fast vortex method. This structure determination can be used as a basis for further semi-quantitative analysis on the U/minor actinides products formed under various experimental conditions. [ABSTRACT FROM AUTHOR]

Abstract: After InTeO3F and InTe2O5F recently described, a new compound In3TeO3F7 is characterized in the In–TeIV–O–F system. The crystal structure was determined by single X-ray diffraction and refined to R 1 =0.028. In3TeO3F7 crystallizes in orthorhombic space group Cmmm, a =7.850(2)Å, b =27.637(6)Å, c =4.098(1)Å, V =889.1(4)Å3 and Z =4. Its structure consists of the stacking, via vertices, of identical layers composed of InF6 and InO2F4 octahedra sharing corners and of InO4F3 pentagonal bipyramids sharing edges and vertices. The Te cations statistically occupy one or the other of two close sites located inside tunnels delimited by the In polyhedra and are bonded to F anions located in the same tunnels. The structure can be considered as an intergrowth of parallel strips of MIn 3 F 10 and hexagonal tungsten bronze (c)-types. It is compared to other structures such as the bronze Sb0.157WO3, TeMo5O16 and Sb2Mo10O31, phases also comprising Te4+ or Sb3+ inside hexagonal tunnels. The electronic lone pair of Te4+ is stereochemically active and a perfect O/F ordering occurs on the anionic sites. [ABSTRACT FROM AUTHOR]