A fruitful industry partnership

Six research students on the EPSRC CDT Fluid Dynamics and EPSRC CDT Future Fluid Dynamics have been, or are being, supported by Sellafield Ltd through their Academic Centre of Expertise for Sludge (Particulates and Fluids) at the University of Leeds.  This Centre is focused on providing support to Sellafield Ltd’s long-term objectives of the safe retrieval, conditioning, storage and ultimate disposal of waste sludges (any mixture of solid particles and liquid), and efficient plant operation. 

Jacob Anderson undertook high-fidelity numerical simulations to bring new understanding to the field of turbulent multiphase flows by exploring the agglomeration behaviour of non-spherical colloidal particles representative of those found in practice. This included the study of behavioural modification of particle systems, wherein the behaviour of particle-laden flows sensitive to chemical and material properties can be manipulated through the addition of additives to improve the flow, mixing and separation of wastes. Modification of such flows in this way can be used during waste retrieval, and during post-operational clean out (POCO) of plant at the end of its operating life to reduce the risk and hazard from the plant, and to reduce its forward lifetime costs. The understanding generated is being applied to potentially reduce the volume and cost of waste processing by using high solids volume fraction flows where particle agglomeration is discouraged, or to encourage flocculation to assist settling of non-settleable material that could be detrimental to downstream radionuclide scrubbing processes. Jacob’s work is currently being extended by Connor Nolan who, amongst other things, will explore the particle-laden flows containing polymers to aid particle flocculation and settling, including the use of machine learning algorithms to allow the more ready application of the techniques developed in practice. Joel Brown, who recently joined the Centre for Doctoral Training, will also extend this work to practically relevant flow conditions.  

Isabel Latimer is studying gas migration and retention in viscoelastic sediments, such as occurs from sludge that has accumulated over many years in storage ponds housing legacy spent Magnox nuclear fuel. Her project is enhancing our knowledge of these systems by examining the mechanisms of bubble growth and release in sediments, with particular focus on characterising the interplay between sediment microstructure (e.g. porosity) and fluid rheology on the dynamics of initial single bubble growth, secondary formation of interconnected bubble networks and the resulting influence on continuous gaseous release. The project combines state-of-the-art x-ray CT measurements and visual data analysis with Lattice-Boltzmann and Monte Carlo techniques to simulate gas flow through porous networks, as well as analytical modelling to link sediment rheology to bubble growth dynamics. This work is being continued by Akash Bhardwaj who also recently joined the Centre for Doctoral Training. 

Ahmad Mohamadiyeh is studying the erosion of sediment beds using impinging jets which are used in various industrial applications, including the nuclear industry where they are used inside storage tanks at Sellafield to erode precipitated nuclear particles and keep them in suspension. The focus of the project is to experimentally investigate the effect of particle properties on erosion, including studies with different size distributions of particles, particle shapes, cohesion and density. Ultrasonic velocity profiling and image analysis are being used to study and track erosion profiles, measuring crater and clearance sizes, and numerical simulations are being employed to understand the hydrodynamics of impinging jet flows, such as levels of turbulence, recirculation and their effects on erosion. Studying these fundamentals of impinging jet erosion aids Sellafield in further understanding and optimising waste management and POCO activities.