High temperature electrochemistry of molten fluoride salt for measurement of dissolved chromium

Abstract

An in situ electrochemical probe, utilising anodic stripping voltammetry (ASV), has been developed to measure dissolved Cr concentration in the molten salt LiF–KF–NaF (46·5-11·5-42 mol.-%), commonly referred to as FLiNaK. Tests were performed in a glassy carbon crucible in an argon atmosphere glovebox at a molten salt temperature of 650°C. Cyclic voltammetry was performed to determine reversibility and mid peak potential. The Cr²⁺/Cr⁰ reaction occurred with a mid peak potential of −0·51 V versus a 10 mol.-% Ni²⁺/Ni⁰ reference electrode. The integrated current from the anodic waves at this potential were used for Cr cation quantification. The integrated current from the ASV measurements correlated linearly with Cr concentration, measured independently using neutron activation analysis, over a range of 30-950 ppm (1·2-38 mmol L⁻¹). This study is significant for determining Cr concentrations in high temperature molten FLiNaK salts exposed to Cr containing structural materials.