GRaZ II: Geochemical retention of radionuclides on cement alteration phases

Summary

The current research aligns to conditions reported by the 'AnSichT' project, which evaluated the feasibility of a repository in German clay formations [1]. According to the developed site model 'NORD', Ca-bentonite will be used in the geo-engineered barrier as buffer and borehole sealing material. Concrete will be emplaced at different places within the repository for sealing and stabilization. Formation waters are characterized by medium to high ionic strengths [2]. Increased salinities can lead to an enhanced degradation of concrete upon water ingress and thus promote the formation of hyperalkaline cement pore waters (10 < pH < 13). The results obtained in the previous BMWi project 'GRaZ' (no. 02E11415B) have shown that such hyperalkaline solutions can react with the bentonite buffer as well as with the surrounding clay host rock and can alter their retention potential towards uranium(VI) [3]. Complex pore waters of increased ionic strength can affect the uranium(VI) and curium(III) retention potential of cementitious phases [4,5].

Further important parameters potentially influencing actinide retention are dissolved iron and organic ligands, released due to corrosion of steel components and concrete, respectively, of the technical barrier. Since reducing conditions are predicted for deep underground nuclear waste repositories in the long term the focus of the current studies is on reduced oxidation states of actinides. Thus, the retention of actinides (uranium, plutonium, curium) by cementitious phases of varying composition and by Ca-bentonite is studied under reducing conditions. Thereby, the influence of low molecular weight organic ligands as well as of dissolved cations (iron(II) or iron(III)) is studied. Competing effects on actinide retention or complexation will be identified and redox transformations will be quantified. The stability of actinide-doped phases at increased ionic strength is studied by applying complexly composed solutions. Furthermore, spectroscopic investigations on the binary systems uranium(VI) – organic ligand and uranium(IV) – organic ligand are performed to identify molecular structures and determine complex formation constants in the hyperalkaline pH range characteristic of cementitious-rich repositories.

This research project is performed in collaboration with the R&D projects of the cooperation partners listed above.

References

1. Jobmann, M., Bebiolka, A., Jahn, S., Lommerzheim, A., Maßmann, J., Meleshyn, A., Mrugalla, S., Reinhold, K., Rübel, A., Stark, L., Ziefle, G.: Projekt ANSICHT - Sicherheits- und Nachweismethodik für ein Endlager im Tongestein in Deutschland - Synthesebericht, TEC-19-2016-AB, DBE Technology & GRS, Peine, Germany (2017).
2. Lommerzheim, A., Jobmann, M.: Endlagerkonzept sowie Verfüll- und Verschlusskonzept für das Standortmodell NORD, TEC-08-2014-Z. DBE Technology, Germany (2014).
3. Philipp, T., Shams Aldin Azzam, S., Rossberg, A., Huittinen, N., Schmeide, K., Stumpf, T.: U(VI) sorption on Ca-bentonite at (hyper)alkaline conditions – Spectroscopic investigations of retention mechanisms. Science of the Total Environment 676, 469-481 (2019).
4. 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).
5. Wolter, J.-M., Schmeide, K., Weiss, S., Bok, F., Brendler, V., Stumpf, T.: Stability of U(VI) doped calcium silicate hydrate gel in repository-relevant brines studied by leaching experiments and spectroscopy. Chemosphere 218, 241-251 (2019).

Publications within the GRaZ II 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).
• Heller, A., Senwitz, C., Foerstendorf, H., Tsushima, S., Holtmann, L., Drobot, B., Kretzschmar, J.: Europium(III) meets etidronic acid (HEDP): a coordination study combining spectroscopic, spectrometric, and quantum chemical methods. Molecules 28, 4469 (2023).
• Philipp, T., Huittinen, N., Shams Aldin Azzam, S., Stohr, R., Stietz, J., Reich, T., Schmeide, K.: Effect of Ca(II) on U(VI) and Np(VI) retention on Ca-bentonite and clay minerals at hyperalkaline conditions – New insights from batch experiments and luminescence spectroscopy. Sci. Total Environ. 842, 156837 (2022).
• Kretzschmar, J., Wollenberg, A., Tsushima, S., Schmeide, K., Acker, M.: 2-Phosphonobutane-1,2,4,-tricarboxylic acid (PBTC): pH-dependent behavior studied by means of multinuclear NMR spectroscopy. Molecules 27, 4067 (2022).
• Stockmann, M., Fritsch, K., Bok, F., Marques Fernandes, M., Baeyens, B., Steudtner, R., Müller, K., Nebelung, C., Brendler, V., Stumpf, T., Schmeide, K.: New insights into U(VI) sorption onto montmorillonite from batch sorption and spectroscopic studies at increased ionic strength. Sci. Total Environ. 806, 150653 (2022).
• 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).

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 6^th International Workshop on Mechanisms and Modelling of Waste / Cement Interactions. 20.-22.11.2023, Prague, Czech Republic. 
• Wollenberg, A., Acker, M., Kretzschmar, J., Schmeide, K., Tsushima, S., Chiorescu, I., Krüger, S.: Influence of the cement additive PBTC on aquatic uranium(VI) speciation and retention on cementitious material. Joint 6^th International Workshop on Mechanisms and Modelling of Waste / Cement Interactions. 20.-22.11.2023, Prague, Czech Republic.
• Wollenberg, A., Kretzschmar, J., Schmeide, K., Acker, M., Taut, S., Stumpf, T.: Characterisation of highly soluble U(VI)-PBTC complexes. 5^th International Caparica Conference on Pollutant Toxic Ions and Molecules (PTIM) 2023. 06.-09.11.2023, Caparica, Portugal.
• 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. 18^th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere - Migration 2023, 24.-29.09.2023, Nantes, France.
• Wollenberg, A., Kretzschmar, J., Tsushima, S., Kraft, R., Kumke, M., Acker, M., Taut, S., Stumpf, T.: Structural identification of aquatic U(VI)-PBTC complexes by spectroscopic investigations. 18^th 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 - 19^th Radiochemical Conference, 15.-20.05.2022, Mariánské Lázně, Czech Republic.

Posters

• Sieber, C., Kretzschmar, J., Drobot, B., Tsushima, S., Schmeide, K., Stumpf, T.: Eu(III) and Cm(III) complexation by nitrilotriacetic acid to further evaluate its impact on the radionuclide retention by cementitious phases. JuRadChem Field trip 2024, Paul-Scherrer-Institut, 29.02.- 03.03.2024, Villigen, Switzerland.
• Sieber, C., Kretzschmar, J., Drobot, B., Tsushima, S., Schmeide, K., Stumpf, T.: Eu(III) and Cm(III) complexation by nitrilotriacetic acid to further evaluate its impact on the radionuclide retention by cementitious phases. 18^th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere - Migration 2023, 24.-29.09.2023, Nantes, France.
• Kretzschmar, J., Schmeide, K., Brendler, V., Stumpf, T.: NMR spectroscopy at the Institute of Resource Ecology. 44^th GDCh FGMR Annual Discussion Meeting 2023. 18.09.-21.09.2023, Konstanz, Germany.
• Sieber, C., Kretzschmar, J., Drobot, B., Schmeide, K., Stumpf, T.: Impact of nitrilotriacetic acid on Eu(III) retention by repository relevant solid phases. Jahrestagung der Fachgruppe Nuklearchemie 2022, 04.-06.10.2022, Bergisch Gladbach, Germany.
• Schmeide, K.: Contribution of bentonite and cementitious material to actinide retention under hyperalkaline conditions and increased ionic strength. DAEF 2022 – 3^rd Conference on Key Topics in Deep Geological Disposal – Challenges of a Site Selection Process: Society – Procedures – Safety, 04.-06.07.2022, Köln, Germany.
• Sieber, C., Kretzschmar, J., Schmeide, K., Stumpf, T.: Complexation studies of Eu(III) with NTA at high ionic strengths. RadChem 2022 - 19^th Radiochemical Conference, 15.-20.05.2022, Mariánské Lázně, Czech Republic.
• 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.