Thermal-hydraulic analysis of the LORELEI test device for the Jules Horowitz Reactor

LORELEI (Light Water One-Rod Equipment for LOCA Experimental Investigation) test device is currently under design in the framework of the planned experimental facilities of the Jules Horowitz Reactor. The main objective of this device is to analyze the thermal-mechanical behavior of the fuel rod and its consequences during a Loss of Coolant Accident (LOCA). The objective of this Thesis is to produce a comprehensive thermal analysis of the LORELEI apparatus by means of CATHARE2 code in order to verify the behavior of the device and to determine the best thermal-hydraulic conditions for the experimental performing. The preliminary part of this thesis aims to illustrate the system and mathematical architecture of the code with a general explanation of the thermal mechanical laws implemented for the FUEL module. An overview of the experimental apparatus, devised so far, is briefly presented to show the characteristics of LORELEI apparatus that can be considered the State of the Art of the LOCA-type facilities. According to the last updated LORELEI geometry, an exhaustive description of apparatus is finalized for a better understanding the CATHARE modeling proposed. This work is aimed to simulate the experimental phase called Re-irradiation phase. This is not a part of the LOCA accidental sequence but it is modeled to provide a study concerning the nominal conditions and to find out the device thermal-hydraulic limits. In this first phase, needed to create a realistic fission product inventory, the device is filled with water and the fuel rod is cooled by using convection flow. The work of this Thesis starts with the simulation of the first part of a LOCA accidental scenario. The fuel cladding temperature is increased and a small amount of water is set in the bottom of the device to produce steam needed for exothermic reactions of the fuel cladding.