Calcul et analyse du phénomène de dispersion dans l'Echauffement Direct de l'Enceinte avec le logiciel MC3D

Titre du congrès :ICAPP seventh International Conference on Advances in Nuclear Power Plants Ville du congrès :Nice Date du congrès :13/05/2007

During the course of a severe accident in NPP's, the Direct Containment Heating (DCH) phenomenon is characterized by a pressurized ejection of the melt out of the vessel resulting in a strong heating an pressurization of the containment atmosphere. The current existing models are highly dependent on the geometry and are not accurate for, at least, French reactors, as well as for the European Pressurized Reactor (EPR). To investigate the phenomenon numerically with details, we are using the 3-dimensional code MC3D. The analysis is based on the DISCO experimental programs (FZK, Germany). Currently, the efforts are put on the hydrodynamical aspects in order to understand the mechanisms for dispersion and corium fragmentation that will lead the energy transfers as well as the chemical aspects (oxidation, and then combustion). We present the results of calculations for two geometries with a rough meshing (including some 3-D cases) so that a lot of calculations could be performed. The results regarding the main features of upward dispersion show that the phenomenon can be accurately described. This allows us in turn to better appreciate and understand the experimental results and, in a way, complete the databank.