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.

The particulate (including colloidal) fraction of natural solutions may be an efficient vector for the dissemination of heavy elements in the geosphere, in particular the radioelements originating from a radioactive waste repository. The scavenging properties of inorganic fine particles (silica, muscovite) toward heavy elements (actinides and lanthanides) were studied by two different complementary approaches, namely sorption experiments either with fine particle suspensions or with mineral monoliths considered as macroscopic surfaces of fine particles. In the former case, the partition coefficient was determined by solution analysis with radiochemical techniques, and in the latter case, the amount of elements fixed on mineral surfaces was evaluated by Rutherford Backscattering Spectrometry (RBS). In both cases, well-defined model systems representative of colloids found in natural waters (silica, alumino-silicate) were used. Results are presented and discussed as a function of pH, nature of particles and surfaces as well as speciation of elements.

The behaviour of two silicates (albite and olivine) toward aqueous dissolution has been investigated with emphasis to two aspects: (1) similarities and differences with silicate glasses; and (2) influence of ion bombardment which transforms the initially crystalline structure to a glass-like one. The occurrence on leached materials of hydrated layers enriched with metallic elements is checked by using high-energy ion beam analytical techniques.

(1982). On the registration of low energy (E 1 keV/amu) ion tracks in dielectric. Radiation Effects: Vol. 65, No. 1-4, pp. 133-137.

We have studied the chemical reactivity of various silicate surfaces (muscovite mica, olivine, feldspar and glasses) irradiated with increasing fluences (> 1010 ions. cm−2) of low energy Pb ions (E ≲ 3keV/amu). This chemical reactivity is markedly enhanced above a critical fluence (≥ 5.1012 Pb cm−2 which is very similar for all silicates investigated. We also studied the effect of a thermal annealing on the chemical reactivity of irradiated glass surfaces.