In the Hydrogen and Aerosol Behavior team, we investigate processes within the containment vessel that play a critical role in the progression of postulated severe accidents in light-water reactors. For example, while accident-induced hydrogen release can cause explosions and thereby jeopardize the integrity of the containment vessel, the aerosols generated during an accident serve as the primary carriers of radioactivity. Therefore, experiments on hydrogen recombination and aerosol behavior are the focus of our large-scale test facilities. Using experimental data, we expand our fundamental understanding of the processes occurring during accidents and develop numerical models for accident simulations.