Electrochemical characterisation of CaCl sub(2) deficient LiCl-KCl-CaCl sub(2) eutectic melt and electro-deoxidation of solid UO sub(2)

• Published in: Journal of nuclear materials 2016-03, Vol.470, p.179-186
• Main Authors: Vishnu, DSri Maha, Sanil, N, Mohandas, K S, Nagarajan, K
• Format: Article
• Language: English
• Subjects: Cathodic polarization; Electrodes; Graphite; Melts; Pellets; Polarization; Tungsten; Uranium
• ISSN: 0022-3115
• DOI: 10.1016/j.jnucmat.2015.12.003

The CaCl sub(2) deficient ternary eutectic melt LiCl-KCl-CaCl sub(2) (50.5: 44.2: 5.3 mol %) was electrochemically characterised by cyclic voltammetry and polarization techniques in the context of its probable use as the electrolyte in the electrochemical reduction of solid UO sub(2) to uranium metal. Tungsten (cathodic polarization) and graphite (anodic polarization) working electrodes were used in these studies carried out in the temperature range 623 K-923 K. The cathodic limit of the melt was observed to be set by the deposition of Ca super(2+) ions followed by Li super(+) ions on the tungsten electrode and the anodic limit by oxidation of chloride ions on the graphite electrode (chlorine evolution). The difference between the onset potential of deposition of Ca super(2+) and Li super(+) was found to be 0.241 V at a scan rate of 20 mV/s at 623 K and the difference decreased with increase in temperature and vanished at 923 K. Polarization measurements with stainless steel (SS) cathode and graphite anode at 673 K showed the possibility of low-energy reactions occurring on the UO sub(2) electrode in the melt. UO sub(2) pellets were cathodically polarized at 3.9 V for 25 h to test the feasibility of electro-reduction to uranium in the melt. The surface of the pellets was found reduced to U metal.