[en] One of the possible means to increase burn-up of the fuel for LWR nuclear power plants is to introduce natural instead of enriched uranium at both ends of the fuel assembly. In the reactor core natural uranium is placed in zones of low neutron flux and forms axial blankets of fertile material. The purpose of the present paper was to examine, using the example of the Krsko NPP, the technoeconomical effects and the practical applicability of the described procedure. From the computational point of view, the problem of determining reactor physics parameters of the core with axially inhomogeneous fuel assemblies is more complex than problem of calculating the standard LWR core. In the frame of the available computer program package three approaches, having different complexity and different accuracy, were chosen. The results obtained were compared with each other in order to estimate the adequacy of the methodology applied. The analysis of the technoeconomical effects of using natural uranium in a LWR core was then performed. (author)