[en] Three experiments on melt-concrete interaction have been carried out in the BETA facility to investigate the zirconium oxidation processes during concrete attack and their influence on concrete erosion and aerosol release. The results clearly show the dominance of the condensed phase chemistry, that is the chemical reaction of Zr and SiO₂ leading to the rapid oxidation of 80 kg of Zr and the formation of Si in the metallic melt within a few minutes only. The high chemical energy release from this reaction produces fast concrete erosion and a pronounced gas spike dominated by hydrogen release. After the completion of Zr oxidation the erosion is determined by the much lower internal decay heat level with moderate interaction processes. The temperature of the melt is measured to decrease very fast to the freezing temperature which can be explained by the very effective heat removal to the melting concrete. The overall downward erosion of 40 to 50 cm of the concrete crucible produces characteristic 2-dimensional cavity shapes. Aerosol release including simulated fission product behavior is reported with respect to aerosol rates, chemical composition, and characteristic particle size. (orig.)