[en] In the case of a core melt accident, outside spraying of the containment is one of the emergency cooling possibilities. For the experimental investigations of heat and mass transfer in laboratory scale, a model containment was built with a diameter of one meter. Additionally a cylinder may be inserted between sump and hemisphere, to enlarge the height of the model containment. The maximum heat power is 11 kW. Thermocouples are used to measure the temperatures at the inside of the containment wall, in the sump and in the containment atmosphere. It is possible to measure the velocity profile under the spherical upper plenum by laser-doppler-anemometrie. Parameter of the experiments were inside coating, height from sump to hemisphere, initial air pressure, cooling water mass flow and sump heating power. The production of inerts, a possible leakage of a controlled blow down gives a change in inerts. The choice of the amount of gas at the start of each experiment allows to consider above facts. The measurements of heat transfer by free convection (Nu/sub FK/) are for big amount of inerts quite good but for lower parts not sucessful.The mass transfer (Sh) has a good reproducibility. By low amount of inerts laminar flow occurs. The influence of the density ratio is much smaller than in the heat transfer correlation, but necessary to consider the turbulent character of the flow. The velocity measurements show a central upstreaming and a down movement along the walls of the pilot plant. A high degree of turbulence was detected. The heat and mass transfer correlations are the experimental base of the calculation of the total inner heat transfer coefficient in the containment simulation code CONTRO. (author)