In the last decade a new platform, i.e. a set of modelling tools, called SIMTONIA, was developed at CER (Centre for Energy Research) to be prepared for the reconstruction of the full-scope training simulator of Paks NPP (Nuclear Power Plant). Using these new tools, we built successfully up a touchscreen based compact training simulator for the plant within a relatively short period of time. In the new compact simulator, most models were created by a simple automatic generation process of technological diagrams based on the data obtained from the present full-scope simulator of Paks NPP. In this paper, we briefly introduce the SIMTONIA modelling framework and its application for the construction of a new compact training simulator. The vitality of the new simulator is demonstrated by running transient scenarios and comparing the results with the ones obtained from the present full-scope simulator.