The Role of Kinetics in Advanced Nuclear Fuel Reprocessing

Jackson, Alex (2022) The Role of Kinetics in Advanced Nuclear Fuel Reprocessing. PhD thesis, UNSPECIFIED.

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Liquid/liquid extraction processes have been designed to selectively partition actinides with especially long-lived radiotoxicity from nuclear fuel waste streams. Uranium and plutonium partitioning has been possible through application of the PUREX and Advanced PUREX processes historically using TBP. Furthermore, the technology for the fabrication of nuclear fuel using mixed actinide salt precursors relies heavily on the availability of the i-SANEX and EUROGANEX processes which utilise the tendency of the organic ligand TODGA to extract trivalent lanthanides and actinides from nitric acid. As such, key properties and behaviours of TBP and TODGA have been the object of my research at Lancaster University. Using a Rotating Diffusion Cell (RDC), it is possible to interrogate the various chemical kinetic and diffusive contributions to actinide extraction by tracking the transfer of solutes over a fixed area membrane between the compartmentalised phases of nitric acid, containing dissolved metal ions, and TBP- or TODGA-loaded solvent. Furthermore, via manipulation of the rotation speed of the RDC several regimes of mass transfer may be reproduced, from low shear diffusion limiting conditions to high shear chemical kinetic control. The rate of extraction of the metal ions investigated is determined by UV-visible light absorbance spectroscopy. An analytical model coded in gPROMS has been developed for parameter estimation purposes, for example to obtain values for kinetic rate constants, based on the experimental extraction rates found. Parameters such as these, as well as insight into the dominant mechanisms of transfer, are fundamental in building the safety case for state of the art reprocessing and partitioning plants.

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Thesis (PhD)
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06 Jun 2022 08:40
Last Modified:
21 Nov 2022 12:19