The demand for energy is constantly increasing and nuclear power remains an important option for many countries to provide energy for development and fight climate change. In Tunisia, two sites are preselected for Nuclear Power Plant (NPP) implantation: Marsa-Dhouiba site in the far north of the country and Skhira site in the South-East. Estimating of health effects on humans (population and workers) following the accidental release of radioactive gaseous materials into the air from a Nuclear Power Plant is essential for the safety and environmental analyses that are needed for reactor licensing. So, the early offsite consequences of severe accident should be assessed before construction of proposed NPP for many purposes, such as site evaluation of NPP, evaluation of the exclusion area and low population zone. Also, the emergency plan must be evaluated to define the mitigation actions. These actions may represented by sheltering, evacuation, distribution of stable iodine tablets and/or relocation and where these actions should take place after the nuclear accident especially in the downwind sectors to decrease the consequences of accident. The hypothetical scenario considered in this paper is a design-basis accident, loss of coolant accident. The RASCAL code was applied to evaluate the health effects and define the protective actions in the event of a nuclear accident for both sites. The health effects can be treated as two important dosimetric parameters: the total effective dose equivalent (TEDE) around the reactor sites and the thyroid commitment dose equivalent (TCDE). After making an analysis of meteorological parameters for both sites, atmospheric dispersion modeling is made for each of the four seasons and finally recommendations for immediate protective actions are discussed.