Under normal operation, nuclear plants release small amounts of radioactive waste. In the unlikely event of a severe accident, followed by successive failures of physical barriers and problems in the control systems and protection of the reactor, the release of radioactive materials can become significant. The problems generated from these catastrophic events can lead to the achievement of high levels of radioactivity in the vicinity of the plant, posing a threat to humans, society and local life. In either of these scenarios, appropriate models and computational tools are needed to predict and evaluate the radiological consequences for the population and the environment. The purpose of studying the dispersion of radionuclides produced and released by a nuclear accident is to provide the information necessary to mitigate its effects. The aim of this work is to evaluate the possible failures in the Nuclear Power Plants (NPPs) of Angra dos Reis (Brazil) which may result in a severe accident. Atmospheric circulation and dispersion models were used to evaluate the displacement of the plume that is strongly influenced by the complex topography of the region.