An experimental study of the coolability of debris beds with geometry variations

The coolability of porous debris beds consisting of a simulant of solidified corium was investigated in an experimental study. The focus was on the effects of the geometrical shape of the debris bed and multidimensional flooding on the dryout heat flux. Dryout heat flux (DHF) was measured for six variations of the debris bed geometry, one of which was a classical, top-flooded cylinder and five that had more complex geometries. The complex geometries included conical and heap-shaped beds which can be considered prototypic to reactor scenarios. It was found that the multi-dimensional flooding related to heap like geometries increases the DHF compared to top flooding by 47-73%. It was emphasized that the debris bed height has to be taken into account when assessing the coolability of realistic geometries: the heap like geometry increases the dryout heat flux by facilitating multi-dimensional infiltration of water into the bed, but it also decreases the dryout power by having a greater height. The measured DHF increase represents a limit for the debris bed height, because if the increase in bed height is greater than the DHF increase, the direct benefit from the multi-dimensional flooding is lost. In addition, post-dryout conditions and their significance in the overall coolability of multi-dimensionally flooded beds were discussed. (C) 2016 Elsevier Ltd. All rights reserved.