In case of accidental release of radionuclides in a nuclear facility or in the environment, there is a risk of external and internal contamination for living organisms (mammals, plants, etc.). Researches conducted to date on nuclear and environmental toxicology are essentially based on experimental studies on a "macroscopic" scale. However, the properties of atomic and molecular entities formed during the transport or transfer of radionuclides can play an important role when looking, for example, to implement effective measures in order to reduce their chemical toxicity. Recent theoretical implementations used in our laboratory allowed us to quantitatively model the structural, dynamic and thermodynamic properties of hydrated actinide ions. The objective of this thesis is to apply these theoretical chemistry models (quantum chemistry, molecular dynamics) to the analysis and understanding of the molecular mechanisms involved in the interaction of a radionuclide with its environment.