During a Loss Of Coolant Accident, water is injected by the Emergency Core Cooling System (ECCS) to ensure the long-term core coolability and by the Containment Spray System (CSS) to remove residual heat and to maintain containment integrity. After the drainage of the RWST (Refueling Water Storage Tank), water is taken from the containment sump in the lower part of the nuclear reactor building. A filtering system is implemented at the bottom of the containment to collect debris produced by the pipe break as well as other latent materials, such as fiberglass, paint and concrete particles, and to minimize the amount of debris entering in the ECCS and CSS systems. Consequently, one of the major issues to be assessed is the plugging of the filtering system due to physical and chemical conditions which can lead to an inadequate net positive suction head (NPSH) margin for the ECCS and CSS pumps and can affect the mechanical integrity of the strainers. The "Institut de Radioprotection et de Sûreté Nucléaire" has launched an experimental R&D project investigating the possible plugging of the sump filter by integral tests performed in the VIKTORIA loop. The analyses of the experiments give very useful results regarding sedimentation, transport of debris and physical plugging, as well as the impact of chemical effects on strainer head loss evolution.