Role of humic substances and colloids in the behavior of radiotoxic elements in relation to nuclear waste disposal - Confinement or enhancement of migration

The potential role of humic substances and colloids on the fate of radiotoxic pollutants should be evaluated in particular around a nuclear waste repository. The different processes involving these entities such as complexation or sorption can strongly affect the behavior of radionuclides. In particular, results on the complexation of actinides with humic substances, investigated by laser induced fluorescence and spectrophotometry will be presented as well as data on the retention of colloids in the presence or not of heavy elements on mineral surfaces measured by Rutherford Backscattering spectrometry. From these studies, the impact of colloids and humic substances on radiotoxic element behavior will be discussed in terms of confinement or enhancement of migration in the geological media.