Rod Ejection Accident 3D-dynamic analysis in trillo NPP with RELAP5/PARCS V2.7

The Rod Ejection Accident (REA) belongs to the Reactivity-Initiated Accidents (RIA) category of accidents, and it is part of the licensing basis accident analyses required for pressurized water reactors (PWR). The REA consist of a rod ejection due to the failure of its driving mechanism. The evolution is driven by a continuous reactivity insertion. In the present work, we have analyzed this transient in Trillo NPP at different power conditions at the beginning of cycle (BOC) and at the end of cycle (EOC) using the coupled code RELAP5MOD3.3/PARCSv2.7. The transient departs from an initially critical core, being the ejection speed of the control rod a typical bounding value. The simulation includes the SCRAM signal in order to compare our best-estimate results with the results from the conservative calculations provided by the NPP. These analyses will allow knowing more accurately characterize the PWR real plant phenomenology in the RIA most limiting conditions, in this way the conclusions will be realistic. The aim is to improve the understanding of these accidents using advanced methods.