EVALUATION OF THE HYDROGEN EXPLOSION HAZARD

An evaluation of the hydrogen explosion hazard during severe accidents is made using recent experimental and theoretical results. It is poss ible to estimate geometric conditions under which detonations can prop agate for a given mixture composition on the basis of detonation cell size data. Multidimensional modelling is suggested to improve the desc ription of detonation propagation conditions. The conditions of sponta neous detonation or strong explosion processes' initiation including a deflagration-to-detonation transition (DDT) and a detonation self-ini tiation mode in non-uniform mixtures (the shock wave amplification by coherent energy release mechanism) are analysed. Detonation self-initi ation is considered as the part of the DDT process that determines the minimum detonation formation distance. The evaluation of this distanc e in the self-initiation mode is suggested for various mixture composi tions on the basis of the values of minimum initiation energy or deton ation cell width. This approach gives the possibility of hydrogen expl osion hazard estimation in spite of the many uncertainties and importa nt unresolved questions about the DDT and spontaneous detonation.