The Sodium-cooled Fast Reactor and the Lead-cooled Fast Reactor are among the six most promising systems selected by the Generation IV International Forum (GIF). Italian research is significantly involved in the major projects of the European Union which deal with these two technologies. Specifically, ERSE is partner in the European Lead-cooled SYstem (ELSY) project for the design of an innovative lead-cooled fast reactor which complies with the Generation IV requirements. In order to analyse the dynamic behaviour of the ELSY plant, ERSE has developed a detailed model of the secondary system which includes the eight steam generators and the main control loops. The steam generator is a nodal point for the feedback between the primary and secondary system. In case of ELSY, it adds to the common physical constraints (steam pressure and temperature) a lower limit of the feedwater temperature to avoid lead freezing during whatever operating condition. The innovative arrangement of the tube bundles brings about an angular distribution of the cold lead at the steam generator outlet, which strongly influences the choice of the proper location of the temperature meters. The paper reports the description of the model of the steam generator developed by ERSE. The model, built following the distinctive modular approach of LegoPST, correctly calculates the radial distribution of the lead temperature and the thermal-hydraulic behaviour of the steam generator, which are essential for the analysis of the plant dynamic behaviour and the control system testing by the simulation of the operational transients. A comparison with results of more detailed CFD simulations is also reported to point out the range of the model reliability.