Analysis of fuel-coolant interaction with SOKRAT/VAPEX code

For a number of years, a stand-alone code VAPEX intended for the simulation of fuel-coolant interaction has been under development at EREC [1]. Recently, a new module VAPEX-M has been developed and implemented as a part of an integral code SOKRAT [2] aimed for analysis of severe accidents. In the VAPEX-M module, the Lagrangian approach is used for the molten corium. The module describes the main processes of heat and mass transfer (heat fluxes from the high-temperature melt into the liquid and vapour phases, hydrogen production rate due to the oxidation of zirconium and steel) and provides relevant data into the thermohydraulic code provided by SOKRAT. The results of verification studies carried out by the combined SOKRAT/VAPEX code are presented. Three experimental series reported in the literature were chosen for the verification calculations: MAGICO [3], QUEOS [4], and FARO [5]. These experiments allow different aspects of fuel-coolant interaction to be verified: drag correlations (MAGICO), evaporation rate (QUEOS), fuel fragmentation and interaction with the coolant in all complexity (FARO). (orig.)