Experimental study and modelling of liquid ejection through orifices by sparging gas

摘要

Corium coolability after a severe PWR accident involving core meltdown and RPV failure is one of the main issues in nuclear safety. The case considered here is a situation in which the corium is assumed to spread over a concrete floor and is flooded by water. In this framework, many research efforts are performed to study the physical phenomena, which may enhance the heat transfer between the corium and the water pool. Among these phenomena, melt entrainment above the corium crust by the sparging gas, released by the concrete ablation appears to be a potentially efficient cooling mechanism. The main target of the PERCOLA experimental program is to provide qualitative and quantitative information on this entrainment phenomenon. It consists in analytical tests performed with simulant materials of increasing viscosity to simulate the enrichment of the corium in SiO_2 during the MCCI. After a short reminder about the assessment of the efficiency of the ejection mechanism, the second part of this paper is devoted to a general description of the test program and to the presentation of the main results. In the last part, attention focuses on modelling the liquid entrainment phenomenon and on comparison between the experimental data and the calculation results of two different entrainment models.