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. Thi s 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 representati ve pressure loads, the IPSN has supported the development of specific combustion models in the PLEXUS code. This modelling has been successf ully validated on tube experiments with and without obstacles and vali dation work is currently underway on a selected RUT experiment. This m odel has also been applied in two-dimensional calculations in differen t geometries (upper dome, pressuriser relief tank bunker, etc.). The i nfluence of various obstacle configurations and mixtures has been inve stigated in order to be representative of various dynamic pressure loa ds on different walls (containment, inner walls). These results will b e used to study the mechanical behaviour of the previously described s tructures for safety analysis. (C) 1997 Elsevier Science S.A.