ANALYSIS OF THE PHEBUS FPT3 CORE DEGRADATION USING SEVERE ACCIDENTS CODES (ICARE/CATHARE, ATHLET-CD, MELCOR)

摘要

The conclusion will be focused on the preliminary synthesis of the Severe Accident Code capabilities to simulate the control rod behaviour in a fuel rod assembly during the course of severe accident transient. There are still some difficulties to reproduce the final degradation of the bundle using codes. The nearly total destruction of the control rod is well reproduced in the calculations. Effects of spreading molten materials of the control rods towards fuel rods of the bundle are suspected, meaning that the main effect of the B4C control rod on the bundle behaviour is connected with B_4C-SS eutectics formation and liquid B_4C-SS-Zry relocation. These phenomena are not accounted for in the SA codes. The need for further code developments of the early phase of core degradation is recognized for the absorber rod material behaviour. BECARRE experiments, in the framework of the International Source Term Program should help us in the understanding and improving the modelling.