Simulation of graphite dust resuspension in a turbulent square dust flow

In a pebble-bed High Temperature Reactor (HTR) core where thousands of graphite pebbles are amassed, the friction between the outer graphite layers of the fuel elements triggers the formation of carbonaceous dust. This dust is eventually conveyed by the coolant gas and deposits in the primary circuit of the reactor. In the event of a Loss of Coolant Accident (LOCA) radioactive carbonaceous dust may be resuspended and escape the system boundaries. There is therefore a need to predict the dust resuspension during a LOCA.
A resuspension model is here presented and coupled with computational fluid dynamics. A Reynolds-averaged Navier–Stokes is employed to simulate the turbulent flow in a wall-bounded channel flow. Micro-sized graphite particles are initially placed on the bottom wall surface of the virtual channel flow. The gas velocity is gradually increased and the resuspended fraction is plotted as a function of the wall shear velocity. The number of reentrained particles increases with gas velocity. The overall resuspended fraction matches experimental data available from the literature. It is found that particles far from the side walls reenter the turbulent flow much faster than those near the corner.
Findings from this study can be used for the prediction of carbonaceous dust resuspension in a HTR during a LOCA.