Currently, reprocessing of spent nuclear fuels is performed using solvent extraction from aqueous solutions (PUREX-process). Pyrochemical reprocessing in molten salts (mainly alkali chlorides) were long considered as an attractive alternative due to high resistance of inorganic salts to radiolysis, absence of neutron moderators, proliferation resistance and lesser volumes of generated liquid wastes.<br/>Nuclear fuel refabrication is one of main steps in the reprocessing technology. Uranium and plutonium oxides can be obtained by electrolysis or by treating melts containing dissolved uranium and plutonium chlorides with oxygen or oxygen containing gas mixtures. Oxygen is also one of primary impurities in the inert atmosphere that can affect electrodeposition or electrorefining of uranium and plutonium metals. Information about interaction of oxygen with uranium species in molten salts is necessary for choosing the process regimes and correct design of refabrication and reprocessing equipment.<br/>Reaction of pure oxygen with solutions of uranium tetrachloride in a number of fused chloride solvents of industrial interest (NaCl–CsCl, NaCl–KCl–CsCl and LiCl–KCl eutectics) was studied here at 550 °C and 650 °C.<br/>In situ high-temperature electronic absorption spectroscopy measurements of uranium-containing melts was applied to study the kinetics of the reactions taking place and characterize soluble products formed. The reaction kinetic parameters, such as reaction rates, rate constants and temperature constants, were determined. The activation energy of the reaction for each system was evaluated. Any insoluble products formed during the reactions were separated from the melts and characterized by X-ray powder diffraction measurements.

Interaction of oxygen with uranium(IV)-containing molten chlorides: A kinetics study

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ACS Fall 2022

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