Procedure and tools for deterministic analysis and control of hydrogen behavior in severe accidents

A systematic step-by-step procedure for the deterministic analysis of hydro gen behaviour and mitigation in severe accidents is presented. The procedur e can be subdivided into four main parts: (1) modeling of the H-2-air-steam mixture generation in the containment, (2) prediction of the risk potentia l of this mixture with respect to flammability, flame acceleration and deto nation on-set, using newly developed criteria, (3) numerical simulation of the appropriate combustion regime with verified 3D-computational fluid dyna mics (CFD) tools, and (4) consequence analysis based on the calculated pres sure and temperature loads. The methodology was used to examine the relativ e merits of different mitigation schemes in studies for a future plant desi gn. Two options for hydrogen control were investigated (a) recombiners only , (b) recombiners with few igniters. Option (a) still allows accumulation o f considerable hydrogen masses in the containment, which could lead to sign ificant dynamic pressure loads to the outer containment shell. Option (b) l ead in the investigated plant and accident scenario to early ignition of st anding flames and negligeable pressure development. (C) 2000 Elsevier Scien ce B.V. All rights reserved.