The aims of this work are to determine the maximum efficiency in the generation and conversion of energy to electricity, and to obtain the exergy efficiency in a pebblebBed modular reactor. The dynamics of the process of energy generation in the nuclear fuel is represented by a point reactor kinetics model, and the process of transport of this energy toward the coolant fluid was based on the conservation laws of mass, energy, and momentum. The conversion to mechanical energy in the turbogenerators, as well as the operation of the heat exchangers, was also made on the simplified models based on physical laws. The results obtained of the energy and exergy balances were applied in order to calculate the maximum efficiency considering a change in the original design and the utilization of the energy lost in the cooling process, respectively.