A dynamic radioecological model was developed to estimate radiation doses and stochastic health risks due to atmospheric releases in case of a nuclear reactor accident. Activities in some foodstuffs, feedstuffs and grass, and doses from different pathways for age groups and stochastic risks can be calculated by the model. Dynamic features include food harvesting, sowing times, feeding regimes, and the growing up of a person. The model can be coupled to any atmospheric dispersion model which can calculate radionuclide concentrations or to any measurement data at predetermined time intervals. Model features are based on ECOSYS-87 model with some modifications. Since the Chernobyl accident, there had been an increase in real world data to assess capabilities of software developed to calculate radionuclide concentrations in environment. In this study, the developed software was validated against measured concentrations and estimated individual doses for Cs-137 following the accident at Chernobyl in 1986, presented in International Atomic Energy Agency Scenario S. Results obtained using the model compare well with dose estimates and activities in the environment.