43 research outputs found
Oxydes d'actinides à façon pour la fabrication de combustibles nucléaires de Génération IV
International audienceCette Ă©tude sâinscrit dans le cadre des recherches menĂ©es sur le traitement-recyclage descombustibles nuclĂ©aires du futur et, plus prĂ©cisĂ©ment, sur la fabrication de nouveaux combustiblessous forme de pastilles Ă partir de poudres dâoxydes Ă base dâactinides de diffĂ©rentesmorphologies. DiffĂ©rents procĂ©dĂ©s de conversion sont envisagĂ©s pour la synthĂšse dâoxydesdâactinides Ă partir de lâuranium et du plutonium issus du traitement des combustibles usĂ©s.Plusieurs Ă©tudes menĂ©es au CEA sur le procĂ©dĂ© de conversion par voie oxalique ont permisdâaboutir Ă des oxalates et Ă des oxydes dâactinides de morphologies trĂšs variĂ©es en fonction desparamĂštres de prĂ©cipitation
Synthesis and characterization of mixed An(IV)An(III) oxalates (An(IV) = Th, Np, U or Pu and An(III) = Pu or Am)
International audienceReaction of a solution containing a tetravalent actinide An(IV), a trivalent actinide An(III) and a single-charged cation such as hydrazinium in presence of oxalic acid in acidic medium under controlled conditions, leads to the precipitation of mixed An(IV)-An(III) oxalate compounds never reported before. By varying the (An,An) pair and depending on the An-An ratio, two original series were obtained (NH,HO)AnAn(CO).4HO (1) and (NH,HO)(AnAn(CO).HO).4HO (2). The crystal structures were identified from powder diffraction patterns by analogy to hydrazinium uranium (IV) lanthanide (III) oxalates whose structures were solved recently by single-crystal X-ray diffraction. Complementary investigations by UV-visible and Infra-Red spectroscopies and thermogravimetric analysis confirm the presence of both tetravalent and trivalent states of actinides in structures (1) and (2) and the role of single-charged cation and water molecules.The originality of both structures is the existence of a mixed crystallographic site for the tetravalent actinide and the trivalent one, the charge balance being ensured by the adjustment of the single-charged ions within the structure. The main difference is that actinides are ten-coordinated in (1) and nine-coordinated in (2).This is the first evidence of a mixed actinide(IV)-actinide(III) site in an oxalate structure
Synthesis and dissolution of mixed oxides (u1-xpux)o2 with different morphologies
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Single-Crystal to Single-Crystal Transformation in the Thorium-TEDGA-Oxalate-Nitrate System Description and Comparison of the Main Structural Features
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Structural study of (N2H5,H)2.9U1.1Ce0.9(C2O4)5·10H2O from a conventional X-ray diffraction diagram obtained on a powder synthesized by a fast vortex process
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Development and characterization of novel Ni/GDC catalysts for hydrogen production
SSCI-VIDE+CARE+ACV:PVEInternational audienceNon