Nuclear power plants are designed with multiple safety systems to prevent and mitigate accidental releases of radioactive materials. Nevertheless, it remains essential to assess the potential consequences of such releases to ensure the protection of the population and the environment. This thesis examines how to assess the radiological consequences of accidental releases from nuclear power plants, with a focus on nuclear safety and public health. These studies are essential to show that nuclear facilities are safe, meet regulatory dose limits, support the ALARA principle (As Low As Reasonably Achievable) and serve as the last line of defense in safety strategies. As nuclear energy is expected to play a major role in low-carbon electricity generation, improving the accuracy and reliability of atmospheric dispersion and dose evaluation methods is increasingly important.