On dryout heat flux in severe accident debris bed

In this work we have analysed the two-phase flow and heat transfer in the porous debris bed form during late-phase invessel severe accident scenario in light water reactors. The heat transfer in debris bed is limited by dryout heat flux. We have carried out calculation of dryout heat flux based on different zero-dimensional two-phase flow models in porous bed. We have suggested improvement over the existing models based numerical optimization for dryout heat flux. We have also studied the behavior of vertical profile of saturation over a wide range of volumetric heat generation rate. The effects of porous media hydrodynamic model parameters have been explored. (author)