Simulation of a LBLOCA in the CALLISTO test facility using the best estimate computer code RELAP5/SCDAP3.2

In this article, 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 (capability for light water irradiation in steady state and transient operation). Following the LOCA a rarefaction wave which 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/SCDAP3.2 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. ference facility of this work, namely CALLISTO, installed at the BR-2 research reactor, is mainly dedicated for PWR (pressurized water reactor) fuel bundle irradiation and qualification. It is composed of an out-of-pile part containing the necessary cooling systems and equipments and three in-pile sections connected to the primary system. Each one of these IPSs is provided with a nine fuel rod clusters operating under high temperature and high pressure conditions (155 bar, 300 °C). havior of the main loop and helium gap parameters following this accident are represented and discussed. eady-state results obtained using RELAP5 are consistent with experimental data. Transient results are compared with results reported in the safety analysis report data for the same accident sequence simulated by the constructor. LAP5 model for the CALLISTO test facility might be considered in the framework of future safety analysis including small and medium break scenarios taking into account the out-of-pile regulating system.