The nuclear industry is experiencing renewed interest in Generation IV technologies and their potential to provide safe, sustainable, and low-carbon energy. Among these concepts, Sodium-cooled Fast Reactors (SFRs) are widely regarded as one of the most mature and promising options. Within this framework, HEXANA is developing an innovative SFR-based Small Modular Reactor aimed at supporting the decarbonization of energy-intensive industrial sectors through the production of both electricity and high-temperature heat. Several challenges must be overcome to complete the project and build the first-of-a-kind (FOAK) reactor by 2035, above all proving the reliability and the safety of the system. In this context, the aim of this work is to investigate the thermohydraulic behavior of the core cooling system by means of 0D/1D numerical simulations, focusing on representative transient scenarios occuring without the intervention of active safety system.