* Determine the fate of radionuclides released into the environment by facilities under normal operating conditions and in accident situations, to answer the questions put by public authorities, nuclear operators, local authorities and the public.
* Model the mechanisms influencing the fate of radionuclides (explanatory models) in close correlation with field and laboratory experiments. The equations and parameters of these models must be as representative as possible.
* Develop the tools required to find a rapid response to the issues raised: qualified operational code with optimized algorithms and number of parameters, together with databases containing radioecological information or describing the environment studied.
* Take into account the spatio-temporal variability of the environment, as well as uncertainties relating to the use of transfer models, in order to integrate the degree of confidence attached to quantitative estimations, particularly whenever they are compared with in situ measurements or regulatory thresholds.
The themes studied favor the development of close interaction between explanatory models, operational models, and laboratory experiments.