Experimental investigation of quenching phenomena in high temperature conical debris bed – Part 1: MONET tests.

• The quenching phenomena of multi-dimensional porous debris bed were studied using experiments. • Visualization of quenching of porous debris bed is performed. • Quench front movement inside the debris bed were mapped. • Different zones of heat transfer during quenching of porous debris bed are identified. In case of severe accidents in light water reactors (LWRs), the coolability of relocated corium from the reactor vessel is a significant safety issue. In a flooded cavity, a porous corium debris bed is expected to develop on the bottom of the cavity pool due to the melt jet breakup and fragmentation. The debris bed needs to be quenched by water either flooding from the top or flooding from the bottom until continuous cooling is established. If it is not quenched, this mass will begin to re-melt due to decay heat and leads to Molten Corium Concreate Interaction (MCCI). Most of the studies reported have conservative assumptions of one-dimensional homogeneous particulate beds with top or bottom flooding condition of coolant. Understanding of debris beds quenching with multi-dimensional characteristics are limited. To investigate the quenching behavior of the conical debris bed by means of experiments, a test facility MCCI-mitigatiON through passive cooling Effect Test (MONET) apparatus is established. Specifically, the objective is to understand the mechanism of heat transfer and quench front movement inside the conical heated debris bed during quenching by cooling water supplied from the bottom of the bed. Two different particle bed bottom wall boundary conditions are studied; closed bottom wall and open bottom wall to understand the effect of water ingression from the bottom wall. The particulate debris bed is formed with two different types of particles; Ø 3 mm SS 304 and Ø 3 mm alumina. In addition, the effect on the quench front movement inside the particle bed has been reported by using temperature measurements together with direct visualizations. [ABSTRACT FROM AUTHOR]