Simulation of H2 distribution and combustion in LWR containments using Lumped Parameter Codes

Abstract This article focuses on the validation of the Lumped Parameter (LP) computer codes COCOSYS and ASTEC in the field of containment phenomena during severe accidents. The release of hydrogen (H2) as an open jet from the primary circuit into the containment might cause atmospheric H2-stratifications which in turn may result in an ignitable atmospheric mixture. If this mixture is ignited, the integrity of the containment can be endangered due to the pressure and temperature rise, resulting from the combustion process. The emphasis of the paper lies on these three phenomena referring to possible successive phases of a loss of coolant accident.