Entwicklung und Durchführung experimenteller Methoden zur verbesserten Modellierbarkeit uranhaltiger salinarer Lösungen (EDUKEM)

Summary

This project is focused on uranium as the major component of nuclear fuel cycle. The major purpose is the provision of quality assured thermodynamic data for tetra- and hexavalent uranium to predict its environmental behavior. This shall enable a better assessment of speciation and solubility limits in diluted to highly saline solutions as expected near nuclear waste repositories as well as for the remediation of the various legacies of uranium mining and milling. Therefore, the focus is on complexation reactions with inorganic ligands found in the environment.

As HZDR has strong capabilities and expertise in actinide spectroscopy, its contribution to the above targets mainly covers speciation studies by time-resolved laser-induced fluorescence spectroscopy (TRLFS), fluorimetry, UV/vis spectroscopy and extended X-ray absorption fine structure (EXAFS). This set has complementary strengths and provides rather low detection limits, down to 10^–6 molar for U(IV) and 10^–10 molar for U(VI). This will not only promote the characterization of complex system, e.g., encountered in nuclear waste management, but also allow a fingerprinting of unknown substances and mixtures which is more reliable than just being based on only one spectroscopy. In such a way difficult to access, systems and conditions should be explored to obtain an integral overview about aqueous uranium chemistry. This especially holds for reducing conditions. All data (thermodynamic as well as associated ion-ion-interaction parameters) will be implemented into the THEREDA database.

Publications

Oral presentations:

• Steudtner, R.; Drobot, B.; Haubitz, T.; Schernikau, M.; Lehmann, S.; Bader, M.; Vogel, M.: "Luminescence spectroscopy of An/Ln in environmental systems" ATAS 2016 - International Workshop on Advanced Techniques in Actinide Spectroscopy, 07.-10.11.2016, Richland, USA.
• Lehmann, S.; Bok, F.; Ikeda-Ohno, A.; Muñoz, A.G.: "Redox Stability of Uranium in High Ionic Strength Media: An Electrochemical and Spectroscopic Study", PRIME 2016 - Pacific rim meeting on electrochemical and solid-state science, 02.-07.10.2016, Honolulu, Hawaii, USA.
• Lehmann, S.; Steudtner, R.; Brendler, V.: "Speciation of tetravalent uranium with inorganic ligands in aqueous solution investigated by UV/vis and time-resolved laser-fluorescence measurements" Ninth International Conference on Nuclear and Radiochemistry - NRC9, 29.08.-02.09.2016, Helsinki, Finland.
• Steudtner, R.; Drobot, B.; Haubitz, T.; Lehmann, S.; Vogel, M.: "Luminescence spectroscopy of uranium" KIT-INE colloquium, 27.07.2016, Karlsruhe, Germany.

Posters:

• Lehmann, S.; Steudtner, R.; Brendler, V.: "Speciation of U(IV) sulfate in aqueous solution - spectroscopic characterization and thermodynamic model", Migration 10.-15.09.2017, Barcelona, Spain.
• Lehmann, S.; Steudtner, R.; Brendler, V.: "U(IV) Absorption and fluorescence spectroscopy" HZDR PhD seminar, 17.-19.10.2016, Oberwiesenthal, Germany.
• Lehmann, S.; Steudtner, R.; Brendler, V.: "EDUKEM project - first spectroscopic insights into the U(IV)/U(VI) speciation in concentrated NaCl solution" HZDR PhD seminar, 2.-4.11.2015, Altenberg, Germany.
• Lehmann, S.; Steudtner, R.; Brendler, V.: "EDUKEM project - first spectroscopic insights into the U(IV)/U(VI) speciation in concentrated NaCl solution" The ThUL School in Actinide Chemistry, 28.09.-02.10.2015, Karlsruhe, Deutschland.
• Lehmann, S.; Steudtner, R.; Brendler, V.: "EDUKEM project - first spectroscopic insights into the U(IV)/U(VI) speciation in concentrated NaCl solution" ABC-Salt IV Workshop 2015, 14. 15.04.2015, Heidelberg, Deutschland.