Influence of iron and organics on uranium and curium retention on Ca-bentonite and cemetitious materials
This thesis is part of the GRaZ II project (Geochemical retention of radionuclides on cement alteration phases). In this project the safety of repositories in deep geological clay formations will be investigated. Ca-bentonite is used as buffer and borehole sealing material while concrete is used for sealing and stabilizing of the repository. The formation waters in these regions are characterized by high salinity. In the event of an inflow of water into the repository, degradation of the cement can lead to highly alkaline conditions in the repository. This in turn can mobilize small organic ligands from the cement or the waste itself as well as iron from the steel casks in which the nuclear waste is stored.
A main goal of this thesis is the investigation of the interaction of uranium as well as curium and plutonium with iron(II) or small organic ligands (citrate) on Ca-bentonite or cementitious phases. It is of interest whether this has an effect on the retention of these actinides in the repository since an efflux of contaminated ground water from the repository is to be avoided.
For characterization of actinide surface complexes and structural changes in the bentonite and cementitious phases TRLFS, XPS, XRD, FT-IR, SEM and NMR will be used.