Engineering Properties, Hydraulic Behaviour and Theoretical Modelling of Nuclear Waste Flows - 11098

A large amount of nuclear waste in the UK is stored in ponds as a solid-liquid slurry, and liquid flows containing suspensions of solid particles are encountered in the processing and disposal of this waste. The slurry systems encountered are complex and it is important to understand how particles interact and aggregate, their behaviour in terms of their settling and re-suspension characteristics, and the properties of deposited beds. A clearer understanding of these issues can allow the refinement of approaches to waste management, potentially leading to reduced uncertainties in radiological impact assessments, smaller waste volumes, lower costs and accelerated clean- up. This paper describes our research in three complementary areas that support the treatment of such waste, namely: the engineering properties of nuclear waste slurries; their hydraulic behaviour; and the theoretical modelling of such flows. Engineering properties have been studied by deconstructing the slurries' complex overall properties to singular particle-particle interactions, allowing the mechanisms involved in particle aggregation to be more readily understood, and the behaviour of flows in pipes has been examined to elucidate the influence they have on the particles in terms of their dispersion, deposition and re-suspension characteristics, and the influence the particles have on the flow. Lastly, computational fluid dynamic models are described, and their usefulness illustrated through application to duct flows, with their ability to predict detailed flow characteristics considered. Overall, the results described have enabled the characterisation of a range of particulate systems, with results pointing to a number of important factors that help to explain the observed variability in industrial slurry behaviour. Additionally, it has enhanced our understanding of, and ability to predict, flows of particles which in turn is of value in enabling the design of cost effective and efficient waste treatment processes.