Redox Equilibrium of U^<4+>/U^<3+> in Molten NaCl-2CsCl by UV-Vis Spectrophotometry and Cyclic Voltammetry

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In order to investigate the redox equilibrium of uranium ions in molten NaCl–2CsCl, UV–Vis absorption spectrophotometry measurements were performed for U4+ and U3+ in molten NaCl–2CsCl at 923 K under simultaneous electrolytic control of their ratio. Prominent absorption bands at 480 and 570 nm were assigned to U3+, and their molar absorptivities were determined to be 1,260±42 and 963±32 mol−1·l·cm−1 respectively. From the dependence of the rest potential of the melt on the spectrophotometrically determined ratio of [U4+]/[U3+], the standard redox potential of the couple U4+/U3+ at 923 K was determined to be −1.481±0.004 V vs. Cl2/Cl−. Cyclic voltammetry measurements were carried out for the couple U4+/U3+, and the results agreed well with this standard redox potential value. By the results of cyclic voltammetry, a temperature dependence of the standard redox potential was found to be −2.094+6.639×10−4T (T=823–923 K).
社団法人日本原子力学会の論文
2005-12-25