Reaction mechanisms of La3+ and Zr4+ in LiCl-KCl eutectic molten salt - cyclic and square wave voltammetry data simulations
Loading...
Date
2011-05-01
Journal Title
Journal ISSN
Volume Title
Publisher
IOP Publishing
Abstract
Nuclear energy increasingly represents an important option for generating clean CO2-free electricity. This has
generated a nuclear renaissance with increased interest in both innovative nuclear reactors and fuel cycle
technologies. The innovative reactor concepts proposed have mainly involved closed fuel cycles with implied
recycling of irradiated fuel. Pyroelectrochemical processes based on a molten alkali chloride/fluoride
electrolyte system show considerable promise, and as such have received considerable attention for fuel
reprocessing. Lanthanum and zirconium are two fission products that are expected to be present in irradiated fuels. The present investigation addresses the electrochemical reduction of La3+ and Zr4+ in LiCl - KCl eutectic molten salt using transient techniques such as cyclic voltammetry (CV), square wave voltammetry (SWV) and chronopotentiometry (CP) from 425 to 550° C, at two concentration levels. Experimental CV data from 50 to
500 mV/sec appears to indicate that the lanthanum reaction mechanism involve a single step reduction
process, i.e., La3+ + 3e- ↔ La. Hence a theoretical simulation of this experimental data should be straightforward as verification of the reaction mechanism. However, zirconium experimental CV data also from 50 to 500 mV/sec appears to indicate that its reduction proceeds through an ab initio sluggish charge-transfer
step coupled with an adsorption/underpotential deposition: Zr4+ + 2e- ↔ Zr2+ followed by a second and
faster step where two electrons further are transferred: Zr2+ + 2e- ↔ Zr. A theoretical simulation of the
experimental voltammograms has been also conducted to verify this reaction mechanism. We show the parameter Λ in their potential separation, ∆Epp and scan rate plot to indicate the reversibility of their electrochemical process, and evaluate their standard electrochemical rate constant. Deconvolution of the SWV data for lanthanum and zirconium confirms that the reduction of La3+ proceeds through three-electron one-step reaction mechanism while that of Zr4+ proceeds through two two-electron step reactions independent of temperature and concentrations levels. © 2011 The Electrochemical Society
Description
Keywords
Simulation, Electrochemistry, Fuel cycle, Irradiation, Zirconium, Lanthanum
Citation
Fabian, C. P., Chamelot, P., Massot, L., Caravaca, C., Luca, V., & Lumpkin, G. (2011). Reaction mechanisms of La3+ and Zr4+ in LiCl-KCl eutectic molten salt - cyclic and square wave voltammetry data simulations. Paper presented at the 219th ECS Meeting, Montreal, Quebec, Canada, May 1-6, 2011. In ECS Meeting Abstracts, MA2011-01(41),1910. doi:10.1149/MA2011-01/41/1910