Hydrogen combustion loads - plexus calculations

The mechanical behaviour of the containment during severe accidents is important in order to maintain tightness of the reactor building. This integrity could be affected by combustion phenomena and, especially, hydrogen detonation. Direct detonation initiation is highly unlikely, but this combustion mode resulting from the DDT phenomenon has to be taken into account in safety analyses. In order to obtain representative pressure loads, the IPSN has supported the development of specific combustion models in the PLEXUS code. This modelling has been successfully validated on tube experiments with and without obstacles and validation work is currently underway on a selected RUT experiment. This model has also been applied in two-dimensional calculations in different geometries (upper dome, pressuriser relief tank bunker, etc.). The influence of various obstacle configurations and mixtures has been investigated in order to be representative of various dynamic pressure loads on different walls (containment, inner walls). These results will be used to study the mechanical behaviour of the previously described structures for safety analysis. (orig.)