Three-dimensional CFD analysis of hydrogen-air-steam explosions in APR1400 containment

The present study concerns the three-dimensional CFD analysis of hydrogen explosions in APR1400 containment. Initial conditions for combustion simulations are obtained by a cost-effective coupling with a lumped parameter code for preceding mixture distribution analysis. Three severe accident scenarios are examined: Small-Break Loss-Of-Coolant Accident (SB-LOCA) and Station Black-Out (SBO) with activated as well as deactivated three-way valve. Only in the last case, thermal ignition of the hydrogen-air-steam mixture could be triggered. Flame propagation in the containment and particularly in the In-containment Refueling Water Storage Tank (IRWST) is investigated in detail. Additional generic scenarios demonstrate the methods ability to reproduce strong Flame Acceleration (FA) and even the hazardous Deflagration-to-Detonation Transition (DDT).