Transport properties of iodide in a sandy aquifer: Hydrogeological modelling and field tracer tests
Résumé
The release of radioactive iodine into geological media from nuclear waste disposal is an issue that has to
be considered since iodine is a biophilic element. 129I is, with 99Tc, one of the two long-lived radionuclides
that have the highest mobility in radioactive waste disposal. Within this context, iodide retardation is still
a matter of debate. A low value of the retardation factor is generally accepted in soils without organic
matter, but the possibility for sorption cannot be completely ruled out. Since isotopic exchange with naturally
occurring iodine is one of the main potential sorption mechanisms, site-specific retention parameters
are needed. In the present paper, we study iodide transport in a sandy aquifer. A hydrogeological
model was built to fit deuterium, bromide and iodide breakthrough data from in situ tracer test experiments.
Within the precision range of the fitting, iodide is excluded from 2.5% of the effective porosity by
anionic exclusion and presents a field retention factor (Kd) lower than 0.025 L/kg.