Simulation of Crystallization of Molten Corium inside Core Catcher of VVER- 1000

Abstract

Modern NPP designs require a device for core melt localization within the containment as a key element of severe accident management. In KKNPP a crucible type core catcher has been installed for retention and cooling of molten corium inside the containment in case of core melt accident. Heat from this molten corium is initially removed from lateral and bottom walls of core catcher and later water is supplied on top melt to intensify the cooling of molten corium. Heat removal from molten corium results in crystallization of molten corium inside the core catcher. The crystallization of molten corium is necessary for the entrapment of radioactive fission products inside the core catcher. The paper deals with the calculation of crystallization time of molten corium inside the core catcher of KKNPP. Different components of melt (oxidic and metallic) and undissolved Oxidic sacrificial material (OSM), which has not melted during OSM and corium interaction has been considered in the calculation of melt crystallization time. Calculations for time determination is performed through the numerical simulation of temperature state of crystallized ingot with the use of finite volume method in axially symmetrical approach. Body fitted coordinate system coupled with the energy solver has been used to generate grids for the considered complex computational domain and to solve the energy equation for the same