Reduction process of uranium(IV) and uranium(III) in molten fluorides |
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Authors: | C Hamel A Laplace O Dugne |
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Affiliation: | a CEA/DEN/VRH/DRCP/SCPS/LPP, site de Marcoule, Bâtiment 399, BP 17171, 30207 Bagnols sur Cèze, Cedex, France b Laboratoire de Génie Chimique UMR 5503, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, Cedex 04, France c Laboratoire EDF R&D, Groupe chimie et Corrosion, Site des Renardières, Ecuelles, 77818 Moret sur Loing, France d CEA/DEN/DTEC/STCF/LMAC, BP 111, 26702 Pierrelatte, Cedex, France |
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Abstract: | This study focused on the electroreduction process of uranium cations in molten fluorides. It involved cyclic voltammetry, chronopotentiometry with and without current reversal, and square wave voltammetry.The results indicate a two-step reduction process for uranium(IV). The first step U(IV)/U(III) exchanging one electron corresponds to a soluble/soluble system and is limited by U(IV) diffusion with DU(IV) = 1.25 ± 0.35 × 10−5 cm2 s−1 in LiF-NaF at 720 °C.In order to perform a thorough study of the second step U(III)/U(0) in the reduction process, the melt was chemically reduced in U(III) with U metal as reducing agent. Alternatively to the use of LiF-NaF where U metal is unstable at 720 °C, the chemical reduction of U(IV) in U(III) was performed in a LiF-CaF2-UF4 solution containing U metal at 810 °C. It has been confirmed that the reduction of U(III) proceeds in one step exchanging three electrons and by a diffusion controlled process with DU(III) = 2.2 ± 0.7 × 10−5 cm2 s−1 in LiF-CaF2 at 810 °C. |
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Keywords: | Uranium Molten fluorides Voltammetry Chronopotentiometry Electrowinning |
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