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Nuclear energy represents an important option for generating largely clean CO2-free electricity. Zirconium is a fission product in the nuclear reaction that needs to be extracted from irradiated fuels used in Gen-IV molten salt reactors. The present investigation addresses the electrochemical reduction of solution soluble Zr4+(soln)to surface confined Zro(s−c)at a molybdenum electrode in a LiF—CaF2eutectic molten salt at 840 °C using DC cyclic, square-wave and AC voltammetry. Cyclic voltammograms simulated by the reaction scheme: Zr4+(soln)+ 4e−→ Zro(soln); Zro(soln)↔ Zr*(s−c); Zr*(s−c)→ Zr4+*(s−c)+ 4e−; Zr4+*(s−c)→ Zr4+(soln); Zr*(s−c)+ Zr4+(soln)↔ 2Zr2+(soln); Zr2+(soln)↔ Zr2+*(s−c)and Zr2+*(s−c)→ Zr4+*(s−c)+ 2e−provided excellent agreement with experimental data over the scan rate range of 50 to 500 mV s−1. The interpretation of the simulation is that the reduction of Zr4+(soln)to Zro(metal)takes place via a transiently soluble Zro(soln)in an overall 4-electron essentially reversible diffusion-controlled process having a reversible formal potential (Eof) of −1.22 V (vs Pt). A minor oxidation process observed at −0.455 V (vs Pt) on the reversing the potential scan direction is simulated via the reaction step Zr(s−c)+ Zr4+(soln)↔ 2Zr2+(s−c)followed by Zr2+(s−c)→ Zr4+(sol)+ 2e−. The sharply rising initial component where reduction of Zr4+(sol)commences, contains evidence of a nucleation-growth mechanism associated with the electrocrystallisation of zirconium metal. This initial rapid growth of current is not fully accommodated in the simulations, but all features found beyond the peak potential are supported by the theory. A comparison with theory based on a direct reduction of Zr4+(soln)to the metallic state having unit activity is provided. It is proposed that an analogous mechanism applies at a Ni electrode, except that a Ni-Zr alloy formation occurs instead of Zr metal.

Nuclear energy increasingly represents an important option for generating largely clean CO2-free electricity and zirconium is a fission product that is expected to be present in irradiated fuels. The present investigation addresses the electrochemical reduction of Zr4+ to Zro in LiCl - KCl eutectic molten salt in the temperature range 425-550degC using cyclic voltammetry (CV), square-wave voltammetry (SWV) and bulk electrolysis. Simulations of the CV data indicate that the initial reduction proceeds through surface confined steps: Zr4+* + 2e[?] - Zr2+* and Zr2+* + 2e[?] - Zr* processes (* adsorbed species) followed by a peak-shaped complex diffusion controlled step that consists of a combination of closely spaced processes associated with the reactions Zr4+ + 4e[?] - Zro and Zr4+ + 3e[?] - Zr+*. Zr+*, probably in the form of ZrCl* is then further reduced to Zro* at even more negative potentials. The simulations provide the first quantitative analysis of the thermodynamics and kinetics of the Zr4+ reduction in the LiCl-KCl eutectic.

The hydrodynamics of a rotating cylinder electrode were modeled to predict tertiary current distributions during electrodeposition of copper from acidic sulfate media, and to evaluate the effects of the resulting density gradients close to the electrode. Assuming no such density variations, then predictions of transport-limited current densities were in good agreement with Mizushina's empirical law and with LevEque's theoretical description, but not with measured values. Assuming a linear density variation with copper concentration, predictions of concentration profiles agreed to within 3 % of experimentally measured limiting current densities at the rotating cylinder electrode. For solution compositions relevant to copper electrowinning, a diffusion coefficient for cupric ions of 1.2x10-9 m2/s at 45 oC, was inferred by solving the continuity, Navier-Stokes and mass balance equations with Fluent(r) computational fluid dynamics software.

Nuclear energy increasingly represents an important option for generating largely clean CO2-free electricity and zirconium is a fission product that is expected to be present in irradiated fuels. The present investigation addresses the electrochemical reduction of Zr4+to Zroin LiCl - KCl eutectic molten salt in the temperature range 425–550°C using cyclic voltammetry (CV), square-wave voltammetry (SWV) and bulk electrolysis. Simulations of the CV data indicate that the initial reduction proceeds through surface confined steps: Zr4+*+ 2e−↔ Zr2+*and Zr2+*+ 2e−↔ Zr*processes (* adsorbed species) followed by a peak-shaped complex diffusion controlled step that consists of a combination of closely spaced processes associated with the reactions Zr4++ 4e−→ Zroand Zr4++ 3e−→ Zr+*. Zr+*, probably in the form of ZrCl*is then further reduced to Zro*at even more negative potentials. The simulations provide the first quantitative analysis of the thermodynamics and kinetics of the Zr4+reduction in the LiCl-KCl eutectic.