Improving Nuclear Fuel Reprocessing

Mixtures containing several interacting species are difficult to characterize, analyze, and understand. Examples of such systems include the solvent mixtures used for the nuclear fuel reprocessing. Poisons are produced as uranium fuel undergoes fission which are detrimental to sustained fission. A proposed solvent system to extract these fission products includes phosphonic acid chelating ligands in a mixture of methanol and supercritical CO$_2$. Methanol has been shown to be effective at increasing the recovery of fission products but its role was not well understood. Using PFG-NMR, we have been able to conclusively show that methanol self-assembles into small clusters and that these small clusters preferentially solubilize the phosphonic acid chelating ligands as monomers which serves to enhance overall fission product recovery compared to the thermodynamically favorable phosphonic acid dimers. This improved understanding allows for the design of new ligands and improved solvent conditions to optimize the regeneration of nuclear fuel thereby minimizing nuclear waste.

Publications

Graham, T.R., Pope, D.J., Ghadar, Y., Clark, S., Clark, A., Saunders, S.R. “Alcohol Clustering Mechanisms in Supercritical Carbon Dioxide using Pulsed Field Gradient, Diffusion NMR and Network Analysis – Feedback on Step-Wise Self-Association Models” Journal of Physical Chemistry – B. Accepted

Funding

Collaborators

Aurora Clark – WSU Chemistry
Sue Clark – WSU Chemistry, PNNL