CORI: Cement - Organics - Radionuclides - Interactions

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Summary

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 [1].

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.

References

1. 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).
2. 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

Journal papers

• Friedrich, S., Sieber, C., Drobot, B., Tsushima, S., Barkleit, A., Schmeide, K., Stumpf, T., Kretzschmar, J.: Eu(III) and Cm(III) complexation by the aminocarboxylates NTA, EDTA, and EGTA studied with NMR, TRLFS, and ITC – an improved approach to more robust thermodynamics. Molecules 28, 4881 (2023).
• Dettmann, S., Huittinen, N., Jahn, N., Kretzschmar, J., Kumke, M.U., Kutyma, T., Lohmann, J., Reich, T., Schmeide, K., Shams Aldin Azzam, S., Spittler, L., Stietz, J.: Influence of gluconate on the retention of Eu(III), Am(III), Th(IV), Pu(IV), and U(VI) by C-S-H (C/S = 0.8). Front. Nucl. Eng. 2, 1124856 (2023).
• Kretzschmar, J., Tsushima, S., Lucks, C., Jäckel, E., Meyer, R., Steudtner, R., Müller, K., Rossberg, A., Schmeide, K., Brendler, V.: Dimeric and trimeric uranyl(VI)–citrate complexes in aqueous solution. Inorganic Chemistry 60, 7998-8010 (2021).
• 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).

Talks

• Schmeide, K., Kretzschmar, J., Huittinen, N.M.: Influence of selected organics on the retention of uranium(VI) by calcium-(aluminate-)silicate-hydrate phases. Joint 6th International Workshop on Mechanisms and Modelling of Waste / Cement Interactions. 20.-22.11.2023, Prague, Czech Republic.
• Schmeide, K., Philipp, T., Huittinen, N.M., Shams Aldin Azzam, S., Kretzschmar, J.: U(VI) retention on bentonite and cementitious materials: Effect of increased ionic strengths and presence of organics. 18th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere - Migration 2023, 24.-29.09.2023, Nantes, France.
• Gaona, X., Ait Mouheb, N., Altmaier, M., Bosbach, D., Deissmann, G., Geckeis, H., Kretzschmar, J., Schmeide, K., Stumpf, T.: Cement-based materials in the multi-barrier system of nuclear waste repositories – impact on radionuclide retention. Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Germany.
• Schmeide, K., Philipp, T., Huittinen, N., Sieber, C., Kretzschmar, J.: Bentonite and concrete: Efficient barrier materials for actinide retention under hyperalkaline conditions at increased ionic strengths and in presence of organics. General Assembly of the European Geosciences Union (EGU) 2023, 23.-28.04.2023, Vienna, Austria.
• Kretzschmar, J., Stumpf, T.: NMR spectroscopy of selected aqueous systems investigated at HZDR-IRE. Actinides revisited – 2022, 21.-23.09.2022, Dresden, Germany.
• Schmeide, K., Huittinen, N., Shams Aldin Azzam, S., Brendler, E., Kretzschmar, J.: Uranium(VI) retention by calcium aluminosilicate hydrates (C-A-S-H) – Impact of temperature, ionic strength, and organic ligands. RadChem 2022 - 19th Radiochemical Conference, 15.-20.05.2022, Mariánské Lázně, Czech Republic.

Posters

• Kretzschmar, J., Schmeide, K., Brendler, V., Stumpf, T.: NMR spectroscopy at the Institute of Resource Ecology. 44th GDCh FGMR Annual Discussion Meeting 2023. 18.09.-21.09.2023, Konstanz, Germany.
• Schmeide, K.: Contribution of bentonite and cementitious material to actinide retention under hyperalkaline conditions and increased ionic strength. DAEF 2022 – 3rd Conference on Key Topics in Deep Geological Disposal – Challenges of a Site Selection Process: Society – Procedures – Safety, 04.-06.07.2022, Köln, Germany.
• Kretzschmar, J., Tsushima, S., Drobot, B., Steudtner, R., Schmeide, K., Brendler, V., Stumpf, T.: Dimeric and Trimeric Uranyl(VI)–Citrate Complexes: ¹⁷O-, ²³Na-, and ¹³⁹La-NMR – Helpful Probes for (Super-)Structure Determination. GDCh Jahrestagung der Fachgruppe Magnetische Resonanz (FGMR), 27.09.-01.10.2021, Germany.

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