VIKTORIA experiments in the frame of R&D project on sump filtration during a Loss Of Coolant Accident: effect of the type of filter, the mass of fiber and the presence of zinc

A R&D project has been done to investigate the clogging of filters used in a recirculation mode for long term coolability. Experiments were performed in the VIKTORIA loop, which was equipped with two types of filters used in French reactors with too different geometries: rectangular pockets or planar grids. The debris carried to the filter generates at 80°C (with chemistry) a quick increase of the head losses across the filter (1 to 7 kPa according to the debris source term) that could be due to rapid chemical effects further to fibers corrosion. Due to different designs, the two filters behave differently with lower head losses for the planar type filters due to low thickness of the debris bed collected on the grids. Experiments performed with less amount of fibers (by replacement of part of fibers by RMI – Reflective Metallic Insulation) led to reducing the head loss: we do not have observed thin bed effect (concentration of the particles in a thinner layer of fibers) which was not obvious. The increase of the duration of the corrosion of zinc in acidic conditions lead to increase head losses by factor 4 due to additional formation of chemical precipitates containing zinc oxides.