Etude du comportement thermo-mécanique d'une boucle préssurisée de type PWR lors d'un LBLOCA au niveau de la section en-pile par le code système RELAP5/MOD3.2

In this thesis, we study a Large-Break Loss of Coolant Accident (LBLOCA) where a rupture occurs on the inner pressure tube of the fuel bundle test section of the CALLISTO test loop facility. Following the LOCA a rarefaction wave propagates inside the helium gap of the double-walled pressure vessel of one In-Pile Section (IPS). The scenario under consideration is a large brittle fracture in the inner pressure tube under the effect of neutron-thermal-mechanical loading. The simulation is conducted using the RELAP5/MOD3.2 thermal hydraulic system code. The assessment study was carried out by comparison of the calculated values against the facility design data and the available experimental data. The reference facility, namely CALLISTO, is composed of an out-of-pile part containing the necessary cooling systems and equipment operating under high temperature and high pressure conditions (155 bar, 300 ° C). The primary circuit connected to three IPSs; each of them is provided with a nine fuel rod cluster. The behavior of the main loop and helium gap parameters following this accident are represented and discussed. The new RELAP5 model of the CALLISTO test facility could be considered as a good basis for future safety analysis including small and medium break scenarios.