CORI: Cement - Organics - Radionuclides - Interactions
The safe disposal of radioactive waste materials in deep geological formations behind multiple protective barriers is followed worldwide as preferred strategy to ensure long-term confinement of the waste to protect people and environment. Cement and cement-based materials are used for the solidification of low- and intermediate-level radioactive waste and moreover, are applied to ensure mechanical stability and sealing of disposal tunnels in nuclear waste repositories. Cement commonly contains polymeric additives (so-called superplasticizers, e.g. polycarboxylate ethers) as well as low molecular weight organics (e.g. citrate, gluconate) to improve the workability of the concrete. Moreover, the radioactive waste itself can contain organic materials. Under hyperalkaline conditions evolving in cementitious environments, such organic components are expected to degrade whereby new organic molecules are formed. Both the original organics as well as their degradation products can potentially act as ligands for radionuclides, thus forming highly soluble and mobile radionuclide complexes. Thus, for a realistic safety assessment of deep geological repositories, the effect of such organic molecules on radionuclide mobility has to be studied.
The CORI project is a collaborative EURAD project that involves numerous international partners investigating interaction processes in the system cement – organics – radionuclides .
In our subproject we are studying the uranium(VI) retention by calcium aluminate silicate hydrate (C-A-S-H) phases and Al-containing tobermorite-like phases in the absence and presence of organics to identify potential effects of organic ligands on uranium(VI) retention by cementitious materials. These investigations are complemented by comprehensive spectroscopic investigations on the binary system uranium(VI) – organic ligand to identify molecular structures and determine complex formation constants in the hyperalkaline pH range characteristic of cementitious-rich repositories.
- Altmaier, M., Blin, V., Garcia, D., Henocq, P., Missana, T., Ricard, D., Vandenborre, J.: CORI – Research on Cement-Organics-Radionuclides-Interactions within the Collaborative EURAD Project. Poster, Migration (2019).
- Wolter, J.-M., Schmeide, K., Huittinen, N., Stumpf, T.: Cm(III) retention by calcium silicate hydrate (C-S-H) gel and secondary alteration phases in carbonate solutions with high ionic strength: A site-selective TRLFS study. Scientific Reports 9, 14255 (2019).
Publications within the CORI project
- Kretzschmar, J., Tsushima, S., Drobot, B., Steudtner, R., Schmeide, K., Stumpf, T.: Trimeric uranyl(VI)–citrate forms Na+, Ca2+, and La3+ sandwich complexes in aqueous solution. Chemical Communications 56, 13133-13136 (2020).