The purpose of this work was to develop a comprehensive model of a lead-cooled fast reactor and to apply it to the transient analysis of this reactor. The executive branch of the European Union is pursuing several ideas for advanced reactors, including a design called the European Lead-cooled System (ELSY). This design is being developed within the frame of the Lead-cooled European Advanced DEmonstration Reactor (LEADER) project. The FAST Reactors Group at the Paul Scherrer Institut has been at the forefront of fast reactor research in general and has developed a code capable of analyzing the behavior of the European Commission's new design ideas in-depth. This study used the group's code and previous experience with ELSY to develop this model.