CFD Modelling of vortex reactors for precipitation reactions in the reprocessing of spent nuclear fuel

Reprocessing of waste from nuclear reactors in order to recover and reuse uranium (U) and plutonium (Pu) plays a critical role in the spent nuclear fuel (SNF) management. The proposed project focuses on the unit operation in SNF reprocessing, which involves precipitation of Pu(IV) oxalate and co-precipitation of U(IV)/Pu(III) oxalate crystals via the reactions between Pu and U nitrates and oxalic acid.

The precipitation reactions are performed in a continuous unbaffled vortex reactor agitated with a magnetic stirrer. A detailed understanding of the reactor hydrodynamic and mixing characteristics is needed and how it affects the precipitation process and resulting crystal properties.

This PhD project aims to address challenges associated with the development and application of digital process modelling tools to investigate the influence of reactor design and processing conditions on the crystal properties. In this project, precipitation process models, based on a population balance model, will be developed for the prediction of crystal size distribution, which will be integrated with a Computational Fluid Dynamics (CFD) software for taking into account the effect of the reactor hydrodynamics and mixing.

Experiments will be carried out to collect data as necessary for model development and refinement. The model can be used as an effective tool for providing an improved understanding of the underpinning science of precipitation processes and optimising the reactor design and safe operating conditions to produce crystals with a required size and shape distributions.