In case of a core melt accident in a European light water nuclear reactor the pressure vessel may fail, in spite of depressurization of the primary circuit, still at an elevated pressure of 1 to 2 MPa. Then, the molten core debris will be ejected forcefully into the reactor cavity and beyond, depending on the specific reactor design. This may pressurize the reactor containment building beyond its failure pressure. The pressurization of the containment is due to the debris-to-gas heat transfer but also to a large part to hydrogen combustion. Hydrogen combustion contributes to peak containment pressure if the energy release rate is greater than the heat transfer rate to structures and occurs concurrent with the debris-to-gas heat transfer. This paper presents experimental and analytical results of the combustion of hydrogen jets blown into a scaled reactor containment with a prototypic atmosphere of air, steam and preexisting hydrogen. Experimental data are the pressure and temperature histories in the containment and pre- and posttest gas species concentrations. These data are used to validate models in the combustion code C0M3D, and once validated will be used to extrapolate to prototypic scale.
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