[en] The purpose of this investigation was to perform an analytical evaluation of a postulated loss of coolant incident in a large pressurized water reactor. A coupled thermal and stress finite element analysis of a fuel rod subjected to a hypothetical blowdown transient was carried out. The effect of two gap conditions and two initial stress states on the response of the fuel rod was studied. Both one-dimensional and three-dimensional models were investigated. To study the heat transfer in the gap region one assumes a conductive mode of heat transfer in the gap characterized by an equivalent thermal conductivity, which is dependent on the current gap width. Accordingly, coupled analysis procedure and computational scheme were established. A mesh generation computer program was developed for the three-dimensional model. The mesh program can be used, with minor modification, to include any degree of ovalization of the clad