Electrochemical processing in molten salts – a nuclear perspective

This work presents an electrochemical study of LiCl-KCl-UCl3 solutions at the temperature range 673–823 K on inert and reactive electrodes, i.e. W and Cd, respectively. On inert electrode, U(III) ions were reduced to metallic uranium through one step and the mechanism of the cathode reaction was irreversible. The diffusion coefficients of U(III) ions in molten chloride eutectic and liquid cadmium were calculated. On reactive electrode, U(III) ions were reduced with depolarization and were accompanied by the formation of intermetallic compound UCd11. The reactions of the cathodic deposition and anodic dissolution of the U-Cd alloy were studied and the conditions of the alloy formation via galvanostatic electrolysis were found. The solubility and the activity of uranium in liquid cadmium were determined.

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confidence: 99%

Electrochemistry of Uranium on Liquid Cadmium Electrode in LiCl-KCl Eutectic

Novoselova,

Smolenski,

Mushnikov

2024

“…[16][17][18][19][20][21][22][23][24][25] Several important metals and alloys, including actinide metals and their alloys, e.g., U, Th, U-Pu, Pu-Fe, U-Ti, U-Mo, U-Nb alloys, etc, have been prepared using this method from their respective oxides. [26][27][28][29][30][31][32][33][34][35][36][37] Fray-Farthing-Chen (FFC) Cambridge process is one such process, wherein the reduction of metal oxide cathode is effected by electrons (electro-reduction), and the process is conventionally conducted in CaCl 2 melt at 900 °C. 38,39 A cell voltage less than the decomposition potential of CaCl 2 melt is applied between the metal oxide cathode and graphite anode.…”

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confidence: 99%

“…8 The electro-reduction of ThO 2 requires a relatively high potential. 32,33 It is also considered an electrical insulator and has an electrical conductivity of 10…”

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confidence: 99%

Studies on Preparation of Thorium-Based Intermetallics in CaCl₂ Melt by Electrochemical De-Oxidation Process

Mukherjee,

Khan,

Kumaresan

2023

Thorium and its alloys find immense applications in nuclear technology. In the present study, the feasibility of direct electrochemical de-oxidation of mixed ThO2-NiO (7:3 molar ratio) and ThO2-Fe2O3 (7:1.5 molar ratio) to Th7Ni3 and Th7Fe3 intermetallics was investigated for the first time in CaCl2 melt at 900oC using FFC Cambridge process. Electro-reduction mechanisms of the mixed metal oxides were elucidated by conducting constant voltage electrolysis at 3.1 V cell potential with sintered mixed metal oxides pellet cathode and HD graphite anode in molten CaCl2 for different time intervals. The electrolysed products were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray analysis techniques. Reduction of the less stable metal oxide, e.g. NiO or Fe2O3 occurred at the initial phase of electrolysis and de-oxidation of more stable ThO2 took place in presence of newly formed metallic Ni or Fe in the later stage leading to the formation of Th7Ni3 or Th7Fe3. Electro-reduction mechanism of ThO2 was evaluated using cyclic voltammetry technique with ThO2 filled Mo cavity electrode and single-step reduction of ThO2 to Th was perceived.

“…Various types of salts were investigated, including halides (primarily chlorides), nitrates, sulfates, carbonates, molybdates and tungstates. [7][8][9][10][11][12] Alkali chloride melts received the most attention, and behavior and speciation of many elements (including actinides and fission products) in those media are fairly well understood. Chloride melts are normally handled under an inert atmosphere and require careful selection of construction materials with sufficient corrosion resistance to fused chlorides.…”

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confidence: 99%

Cathodic Processes in Uranium Containing Molybdate Melts

Volkovich

Smolenski

Рыжов

et al. 2023

Cathodic processes in Li2MoO4–K2MoO4–MoO3 UO2MoO4 and K2MoO4–MoO3 melts containing added UO2MoO4 were investigated at 550–800 oC using cyclic voltammetry, cathodic polarization and bulk electrolysis. Cathodic reduction of molybdate melts (not containing uranium) resulted in formation of molybdenum dioxide. Products of the cathodic reactions in the melts containing uranium molybdate predominantly consisted of crystalline uranium oxides (mostly UO2 and U4O9) and MoO2. Minor products formed included other uranium oxides (U3O8, U13O34), mixed uranium-molybdenum oxides (U1.5Mo10O32, Mo2UO8) and molybdates (provisionally attributed to K2U(MoO4)3). Effect of temperature, cathodic current density 0.05–1 A/cm2), excess MoO3 concentration (30–50 mol. %) on the composition of the cathodic reaction products were analyzed. Oxygen-to-uranium atomic ratio (oxygen coefficient) for primary uranium oxide phases was determined and varied from 1.963 to 2.161 for UO2±x and from 2.209 to 2.287 for U4O9±y. The effect of the electrolysis regime on the composition of the cathodic product was also considered. Constant-current and constant-potential electrolysis, as well pulsed-current, pulsed-potential and pulsed-reversed-current electrolysis were investigated with varying the parameters of alternating pulses (duration, current density or potential). Chemical and phase composition of the products produced by bulk electrolysis was fully characterized.