Core degradation simulation of the PHEBUS FPT3 experiment using COMPASS code

As a part of the integrated severe accident code development project in Korea, KAERI (Korea Atomic Energy Research Institute) has been developing a stand-alone severe accident analysis code, COMPASS (COre Meltdown Progression Accident Simulation Software), which simulates the in-vessel severe accident phenomena including the core heat up, material melting and relocation, corium behavior in the lower plenum, and vessel failure. For the purpose of COMPASS code validation, a numerical simulation was conducted for the PHEBUS FPT3 experiment, which is an integrated severe accident experiment, initiated in 1988 by IRSN. In the COMPASS code, the core and surrounding structure in a test section consist of a two-dimensional node system, and the mass and energy equations are established for the main component in the core and surrounding structures. The temperature evolution of the core and surrounding structure at various locations of the test section are pursued and compared with the experimental data as well as the numerical results of the MELCOR code. The hydrogen generation rate and final mass distribution are compared among the experimental data and the numerical results of COMPASS and MELCOR. Generally, the COMPASS and MELCOR codes predicted the temperature evolution and hydrogen generation rate during the experiment well. In addition, COMPASS predicted a slightly smaller mass relocation compared with the experimental data, whereas MELCOR has a larger mass relocation.