The presented work is part of a joint research project performed in cooperation between the Forschungszentrum Dresden and University of Applied Sciences Zittau/Goerlitz. The paper deals with experimental investigations concerning the influence of an impinging jet on sedimented insulation material in the building sump of the reactor containment. One of the main tasks in reactor safety research is the safe heat dissipation from the reactor core and the containment of light-water reactors. In the case of loss of coolant accident (LOCA) the possibility of the entry of insulation material into the containment and the building sump of the containment and into the associated systems to the residual heat exhaust is a serious problem. In the long-term phase of a LOCA the coolant ejected by the pipe leakage falls several meters onto the sump water surface. On this way, the jet is mixed with air. Furthermore, the impinging jet will entrain air bubbles into the building sump of the reactor containment. The entrained air bubbles will rise and have an additional influence on the flow field in the sump and of the sedimented insulation material. Hence, the impinging jet has an influence of the insulation material transport in the sump. To investigate the influence of an impinging jet a special test facility was designed. The test facility “Tank” was build up with acrylic glass. Thereby it is possible to use laser PIV to measure the flow field and high-speed video to analyze the jet-structure in the test facility. With help of this instrumentation the following experiments were performed: • Experiments without air entrainment and different distances between pipe outlet and water surface in the test facility. • Experiments with air entrainment, different distances between pipe outlet and water surface in the test facility and different flow velocities of the impinging jet. • Experiments with a cold impinging jet and hot water in the test facility for a defined distance between pipe outlet and water surface and a defined jet velocity of the jet. The main goal of the experiments is to study the physical phenomena of the impinging jet and provide experimental data for verification of CFD models. The corresponding CFD investigations are reported by Krepper et al. [KRE10].

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