[en] In a compartment model the considered parts of the environment (e.g. sea, lake, sediment or tilled land) are described by reservoirs, compartments, in which the concentrations of radionuclides are assumed to be homogenous in the whole compartment. The transfer of the radioactive material from one compartment to another is described by flows, in which the amount of transferred material is proportional to the transfer coefficient and to the activity concentration in the compartment. In the DETRA (Doses via Environmental Transfer of Radionuclidies) computer program the transfer of radionuclides can be calculated either by a dynamic or a stationary solution. The evaluation of radiation doses from the calculated concentrations is computed by using concentration factor method. The program DETRA has been developed for the safety analyses of nuclear waste disposal but also the estimation of the transfer of other releases (also non-radioactive) is possible by using the model. The model has been used in the safety analyses of the disposal of radioactive low-level and medium-level wastes and spent nuclear fuel. The repositories are assumed to be situated in Olkiluoto on the west coast of Finland. In this work results of models, that describe the release of radionuclides from repositories and transfer with the ground water to the biosphere, are used in calculations. The transfer of radionuclides in the biosphere has been evaluated on three scales: local, Baltic and global scales. The transfer and accumulation of different release nuclidies has been analysed. Also the main results of safety analyses are presented. The results have been compared with the concentrations and dose impacts of the naturally occurring radionuclides. The model itself and its parameters include many uncertainties. How well the model describes a known transfer environment includes also uncertainty factors. The conditions in the biosphere will change during the long time spans studied. The model is analysed by studying the behaviour of naturally occurring and fallout radionuclides. The main result of the sensitivity analyses are also presented