This thesis has been developed in the framework of an Internship in Electricté de France (EDF). In a world where competitiveness between low carbon electricity providers is at its fiercest and the stakes given the ecological transition are highest, EDF aims to strengthen its position as one of the world leaders in the field. To achieve this goal, the company wishes to preserve as well as develop its expertise and its capacity to manage potential accidents as maintaining high levels of safety remains its top priority. In particular, the National Emergency Response Center’ understanding of the impact of the safety injection system’s availability during accidental transients, such as the Loss Of Coolant Accident (LOCA), is essential.