Thermohydraulic analysis of a valve break in theLORELEI test device

The LORELEI experimental setup in the Jules Horowitz Reactor (JHR) is dedicated for the study of fuel during a Loss of Coolant Accident (LOCA). The main objective of the LORELEI (Light-Water One-Rod Equipment for LOCA Experimental Investigation) is to study the thermal-mechanical behavior of fuel during such an accident and to analyze the fission products source term (including short half-life fission products). In order to study those phenomena, the fuel sample will experience a transient neutron flux field, which in turn will generate a Linear Heat Generation Rate (LHGR) and determine the temperature of the fuel and its cladding, simulating the behavior of the fuel and the cladding during a LOCA accident. In order to reproduce a LOCA-type transient sequence, the experimental test device will be located on a displacement device. The displacement device moves the test device in the neutron flux zone in order to generate the representative thermal conditions. In the re-irradiation, reflooding and post-quench cooling phases, the coolant is water and the above failure scenarios may result in a two-phase flow field. In order to model those two-phase transient scenarios, the CATHARE2 code was used. The CATHARE code is a French best-estimate thermalhydraulic code. CATHARE's acronym is: Code for Analysis of Thermalhydraulics during Accident and for Reactor safety Evaluation. This work aims to investigate one of the ''off normal scenarios'' in the LORELEI test device which could occur at the re-irradiation phase - a failure of a pipe or a valve in the valves box. In such a case, the water in the test device flows immediately (totally or partially) to the valves box and the fuel sample may be exposed. As a first step, a steady-state model of the re-irradiation phase has been developed and compared with a 3D FLUENT analysis. Then, the evolution of the thermohydraulic conditions in the failure was studied