Current understanding of the flow and settling dynamics of nuclear waste suspensions and sludges is poor due both to the complex nature of the particle phase, its interaction with the fluid phase, the influence of flocculation and other time-dependent properties, as well as a scarcity of useful data for such materials and flows and the physical, chemical and radiological difficulties in gathering such data from real waste repositories. The modelling will provide predictions of similar flows will be obtained using a coupled large eddy simulation/Lagrangian particle tracking technique, with the influence of levels of turbulence, and the direction of gravity, on particle agglomeration and settling behaviour, and the shear break-up of particle aggregates explored.