Electroanalytical measurements of binary-analyte mixtures in molten LiCl-KCl eutectic: Uranium(III)- and Magnesium(II)-Chloride

• Published in: Journal of nuclear materials 2017-04, Vol.486 (C), p.369-380
• Main Authors: Rappleye, Devin, Newton, Matthew L., Zhang, Chao, Simpson, Michael F.
• Format: Article
• Language: English
• Subjects: Chloride; Diffusion coefficient; Electrochemical analysis; Electrochemistry; Eutectics; Lithium chloride; Magnesium; Nuclear fuels; Potassium chloride; Spent nuclear fuels; Uranium; Voltammetry
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2017.01.047

The electrochemical behavior of MgCl2 in molten LiCl-KCl eutectic was investigated to evaluate its suitability as a surrogate for PuCl3 in studies related to the eletrorefining of used nuclear fuel. The reduction of Mg2+ was found to be electrochemically reversible up to 300 mV s−1 at 773 K. The diffusion coefficient for Mg2+ was calculated to be 1.74 and 2.17 × 10−5 cm2 s−1 with and without U3+ present, respectively, at 773 K using cyclic voltammetry (CV). Upon comparison to literature data, the diffusion coefficient of Mg2+ differs by only 8.8% (with U3+ present) from that of Pu3+ and the difference in peak potentials was only 79 mV. Binary-analyte mixtures of UCl3 and MgCl2 in eutectic LiCl-KCl were further investigated using CV, normal pulse voltammetry (NPV), chronoamperometry (CA) and open-circuit potential (OCP) measurements for the purpose of comparing each technique's accuracy in measuring U3+ and Mg2+ concentrations. Of all the techniques tested, NPV resulted in the lowest error which was, on average, 11.4% and 9.81% for U3+ and Mg2+, respectively. [Display omitted]