Experimental and analytical investigations for debris transport phenomena in multidimensional water flow

The investigations of insulation debris generation and transport gain in importance regarding the reactor safety research for PWR and BWR considering all types of LOCA as well as short and long term behaviour of emergency core coolant systems.
The background of experimental investigations consists of the generation of a wide data base developing and validating the CFD-models for the description of particle transport phenomena in flow (e.g. drift, subsidence, sedimentation, resuspension, agglomeration and head loss at hold-up devices) under various geometric and fluidic boundary conditions. Separate effect experiments for the investigation of particle transport phenomena in multidimensional water flow, sedimentation and resuspension processes were carried out at plexi glass test facilities (Column, Ring Channel) using modern flow measurement and digital image processing technologies. The behaviour of gravitating insulation particles in aqueous solution (sink rates or settling velocities) and sedimentation processes were observed at the test facility “Column” in 2D-geometry. Experiments for the determination of 2D-transport behaviour of different particle sizes in horizontal carrier flow were realised at facility “Ring Channel”. Experimental results were generated with constant cross section area along the whole channel length as well as with varied cross section areas (e.g. barriers) and strainers.
Model developments for CFD simulations of insulation material transportation, suspension, resuspension and the clogging and penetration at strainers are described. The check of model parameters and functions based on the separate effect experiments.
The paper includes the presentation of experimental results generated at the facilities, the theoretical concepts for modelling these phenomena with CFD-codes and the comparison between simulated and measured data.