Absorption spectra and cyclic voltammograms of uranium species in molten lithium molybdate–sodium molybdate eutectic at 550 ºC

T. Nagai 1 , A. Uehara 2 , M. Fukushima 3 , M. Myochin 4 , T. Fujii 5 , N. Sato 6 , and H. Yamana 7
  • 1  Japan Atomic Energy Agency, Nuclear Fuel Cycle Engineering Laboratories, Ibaraki 319-1194, Japan
  • 2  Kyoto University, Research Reactor Institute, Osaka 590-0494, Japan
  • 3  Japan
  • 4  Japan
  • 5  Kyoto University, Research Reactor Institute, Sennan Osaka 590-0494, Japan
  • 6  Japan Atomic Energy Agency, Advanced Science Research Centre, Tokai, Ibaraki 319-1195, Japan
  • 7  Japan

Abstract

Absorption spectra of uranium species dissolved in molten lithium molybdate–sodium molybdate eutectic of 0.51Li2MoO4–0.49Na2MoO4 mixture at 550 ºC were measured by UV/Vis/NIR spectrophotometry, and their redox reactions were investigated by cyclic voltammetry. We found that the major ions of uranium species dissolved in the melt were uranyl penta-valent. After purging dry oxygen gas into the melt, penta-valent species were oxidized to the uranyl hexa-valent. In the cyclic voltammetry of the melt without uranium species, it was confirmed that the lithium-sodium molybdenum oxide compounds were deposited on the working electrode at the negative potential and the lithium molybdenum oxide compounds were deposited on the counter electrode at positive potential. When UO2 was dissolved into the melt, the reductive reaction of the uranium species was observed at the reductive potential of the pure melt. This suggests that the uranium species dissolved in the melts could be recovered as mixed uranium-molybdenum oxides by electrolysis.

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