[en] Calculations have been performed for the thermal and mechanical design of the fuel elements of FDR-2. This had to be done in accordance with the German licensing authorities opinion about the maximum center temperature in the fuel, maximum plastic deformation in the cladding and sufficient margin with respect to fatigue fracture. This means that a detailed life history of the most critical fuel rods had to be considered. The main design criterium for the fuel rods is the full power cycling feasibility of the ship reactor core which avoids restrictions on the manoeuvrability of the ship. Furthermore the thermomechanical behavior of some fuel rods during the restart of the reactor after partial reloading of the core was studied. The fuel modeling code SATURN-LG has been used, which calculates quasistationary the thermomechanical state of light water reactor fuel rods as a function of the operating conditions. For two fuel rods the values of the most important physical quantities dependent on the reactor operating history will be presented and discussed. Some remarks about the underlying models and the uncertainties in the fuel rod behavior prediction will be made