RANS modeling of fluid flow and dust deposition in nuclear pebble-beds

In the nuclear pebble-beds, occurrence of localized hot-spots in the fluid flow, as well as accumulation of abraded graphite dust are two of the major concerns during a potential accident. The present paper deals with the Reynolds Averaged Navier Stokes modeling of the fluid flow and dust deposition in a chosen set of pebble-bed configurations. A standard k-ε model with enhanced wall treatment is used for modeling the flow turbulence. For the dust phase, a continuous random walk model, coupled with a carefully chosen near-wall anisotropic model is used to predict the dust transport and deposition. The chosen standard k-ε model is first validated by applying it to study the flow behavior in a so-called single cubic pebble-bed arrangement where q-DNS data is available for validation. The validated model is then applied to analyze the complex flow behavior in a structured and an unstructured pebble-bed arrangement. The chosen dust deposition model is first validated across five different test-cases where experimental data is available for validation. The validated model is then applied to analyze the complex three dimensional deposition patterns in a structured and an unstructured pebble-bed configurations.