Title Thermal-Hydraulic Study of the MEGAPIE- Target with the Computer Code RELAP5

The disposal of radioactive waste might decide the future of nuclear energy. Transmuting the radioactive waste by an Accelerator Driven System (ADS) might provide a solution to this problem. The protons coming from the accelerator carry out a spallation reaction with material of the target obtaining neutrons, which transmute plutonium, minor actinides and long-lived fission products into short-lived radioisotopes or stable nuclei. The feasibility however of the ADS system has still to be proven. The MEGAPIE (MEGAwatt PIlot Experiment) project has the purpose of demonstrating the safety operation of a Lead-Bismuth spallation target with proton beam power of 1MW. One of the tasks of the MEGAPIE Project is to design an adequate cooling system of the liquid Lead-Bismuth Eutectic used as spallation source. This cooling system has the purpose of counteracting the enormous amount of heat given from the proton source to the Lead-Bismuth Eutectic and to the structural materials. In this Report are shown the results of the experiments that were made with RELAP5, a computer simulation code adequate for thermal-hydraulic calculations. It was analyzed the thermal-hydraulics of the cooling system under normal and transient conditions