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Contribution of various techniques to U(VI) and Pu(IV) mass transfer kinetics in liquid-liquid extraction: towards the kinetics regime determination thanks to 3 technics

Abstract : In the frame of the development of Generation IV reactors, CEA is developing an advanced liquidliquid extraction process for the multirecycling of plutonium from the spent nuclear fuels. Thermodynamic data have already been acquired for the modeling of the extraction equilibriums in this process, but accurate kinetic data are also required to simulate the process in short-time contactors and for its scale-up in industrial contactors such as pulsed columns. This paper summarizes the acquisition of mass transfer coefficients of uranium(VI) and plutonium(IV) between nitric acid and a monoamide-based solvent upon extraction with three different techniques: the single drop technique, the Nitsch cell and the rotating membrane cell (RMC). The influence of temperature, nitric acidity, viscosity of the organic phase, the drop size and the nature of the continuous phase (aqueous or organic) on the transfer of uranium and plutonium during the extraction step was studied. The results obtained by the single drop technique showed that U(VI) and Pu(IV) mass transfer constants are quite similar. These data were compared with the literature as with results obtained in similar conditions with the TBP solvent currently used in the PUREX process. They revealed that the kinetics of U(VI) extraction with this monoamide solvent is about three times slower than with TBP, probably because of the higher viscosity of the monoamide-based solvent. The single drop method allowed the most complete study but the other methods brought some qualitative information to better understand the phenomena involved in the transfer of uranium and plutonium with this system. The global results point out that the resistance to the transfer is essentially located in the organic phase and the diffusion process would mainly control the kinetics. An attempt to estimate the chemical and the diffusionnal kinetic constants based on experimental results led also to the same conclusion. These results lead to a better understanding of this extraction system and will help to simulate experimental profiles of uranium and plutonium concentrations measured in continuous tests performed in mixer-settlers or pulsed columns with this monoamide solvent.
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https://hal-cea.archives-ouvertes.fr/cea-02509776
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Submitted on : Tuesday, March 17, 2020 - 10:52:08 AM
Last modification on : Wednesday, May 20, 2020 - 1:14:31 AM
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  • HAL Id : cea-02509776, version 1

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A. Lelias, R. Berlemont, B. Dinh, M. Montuir, M. Miguirditchian, et al.. Contribution of various techniques to U(VI) and Pu(IV) mass transfer kinetics in liquid-liquid extraction: towards the kinetics regime determination thanks to 3 technics. ATALANTE 2016 - Nuclear Chemistry for Sustainable Fuel Cycles, Jun 2016, Montpellier, France. ⟨cea-02509776⟩

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