The modelling of the dispersion of liquid discharges in rivers relies heavily on the selection of appropriate models (hydrography, hydraulics and dispersion) in regard of the situation (normal operating conditions, crisis, case of expertise…) and operational criteria such as available data, calculation time and required precision. To ensure the best choice for a given case, this research aims to compare and characterize the optimal application areas of three modelling tools available at IRSN by considering their suitability for routine assessment (monitoring, site expertise, etc.) and accidental scenarios (situation assessment, decision support…), as well as their performance and operational constraints, including data requirements and response times. The tools compared are a 1D dynamic model (SYMBIOSE, developed at IRSN and co-owned by IRSN and EDF), a 2D analytical approach in steady-state conditions (CASTEAUR2D, developed at IRSN) and a numerical 2D model (TELEMAC 2D, originally applied by IRSN for flood risk assessment). The study focuses on the downstream of the Dampierre-en-Burly nuclear power plant (NPP) located on the Loire River, 50 km upstream from Orléans, which is already used as an application area for the TELEMAC 2D model at IRSN. To identify the privileged application domains of these tools, they are applied and compared on the base of in situ tritium activity concentrations measured in the Loire River by EDF during routine discharges of the NPP for low and medium flow rate conditions of the river and completed by an hypothetical case for high flow rate conditions. It can be concluded that SYMBIOSE excels in quick response but has limitations as it only provides mean activity concentration and maximum activity concentration values. CASTEAUR 2D offers accessible setup but simplifies river geometry. TELEMAC 2D provides authentic 2D data but demands more computational resources and expertise.