[en] An exact and complete solution of fuel rod analysis is not possible within the present knowledge. So one has to make assumptions to simplify either the complexity of the state of deformation or the complexity of material behavior, which includes the analysis of only a small section of the fuel rod. The author wants to point out, that both lines of analysis are important and complementary to each other. The URANUS-code follows the first line: a quasi 2d thermal and mechanical integral fuel rod analysis is combined with highly complex material behaviour. The quasi 2d solution has been compared with a 2d-finite element solution. An excellent agreement in the axial friction force distribution was found. The mechanical description takes seven components of strain into account: elastic, time-independent plastic, creep, thermal and strains due to swelling, cracking and densification. Models for temperature distributions heat generation, gap closure, pellet cracking, crack healing, fission gas release, corrosion, O/M distribution and Pu-redistribution are included. In the paper the new basic mechanical concept, which is a superposition of a 1d-radial solution and a 1d-axial solution is given as well as all basic equations. The mechanical concept determines the code structure, which also is shown in detail. (Auth.)