Contact

Dr. Vinzenz Brendler
Head of Division
Surface Processes
v.brendler@hzdr.de
Phone: +49 351 260 - 2430
Fax: +49 351 260 - 3553

Dr. Nina Maria Huittinen
Surface Processes
n.huittinenAthzdr.de
Phone: +49 351 260 - 2148

Dr. Robin Steudtner
Institute of Resource Ecology
r.steudtnerAthzdr.de
Phone: +49 351 260 - 2895

Aquatic Actinide Chemistry and Thermodynamics at Elevated Temperature Conditions (ThermAc)


Financed by:
German Federal Ministry of Education and Research (BMBF, 02 NUK 039B)
Funding period:
2015/03/01 – 2018/02/28
Cooperation Partner:
KIT / GRS / TUM / FZJ / PSI / Amphos21 / Heidelberg University
People:
V. Brendler, C. Franzen, N. Huittinen, R. Steudtner
Students:
T. Haubitz, H. Lösch, E. Ritter


Summary

For the safety assessment of high-level nuclear waste repositories in deep geological formations, a sound understanding on the migration behavior of mobilized radionuclides from the spent nuclear fuel is required. In recent decades, the solution chemistry of actinides, including hydrolysis and complexation with organic- and inorganic ligands, as well as the interactions of actinides at interfaces present in the geo- and biosphere have been intensely investigated. These studies are, however, often conducted at ambient temperatures (20-30 °C), which hampers the prediction of actinide migration in the environment of heat generating high-level nuclear waste repositories. It is estimated that maximum temperatures in the near field of a SNF repository could reach 100 °C, depending on the waste form and host rock under consideration. Under these conditions, water properties such as the density, dielectric constant, viscosity and ion product are different from room temperature conditions, which may influence the speciation of metal ions in solution. Thus, for a reliable safety assessment of future SNF repositories, already existing results on actinide complexation with relevant (solubility determining) inorganic ligands at ambient conditions, should be complemented with data obtained at higher temperatures.

This project focuses on investigations of actinide complexation reactions with common inorganic ligands found in the environment at elevated temperatures (up to 100 °C). Various experimental methods, such as time-resolved laser fluorescence spectroscopy (TRLFS), attenuated total reflectance Fourier-Transform infrared (ATR-FT-IR) spectroscopy, UV-vis, and isothermal titration calorimetry (ITC), are employed to derive complexation constants and thermodynamic parameters of the formed complexes. In addition, complementary to the experimentally derived thermodynamic data, the temperature dependency of the complex stability constant (logK), are calculated by different approximation methods.

ThermAc

Left: Emission spectra of U(VI)-sulfate complexes obtained with time-resolved laser fluorescence spectroscopy (TRLFS) at varying temperatures between 5 °C and 60 °C. Right: Calculated species distribution for U(VI)-sulfate complexes at 40 °C.

Publications

Thesis:

  • Eva Ritter (2017): "Einfluss von Temperatur und Sulfat auf die Uran(VI)-Speziation im aquatischen System", Masterarbeit, Technische Universität Dresden
  • Toni Haubitz (2016): "Einfluss von Sulfat auf die Uran(VI)-Speziation im aquatischen System", Bachelorarbeit, Brandenburgische Technische Universität Cottbus – Senftenberg

Oral presentations:

  • R. Steudtner, K. Müller, B. Drobot, C. Franzen, T. Haubitz, V. Brendler (2016): "Uranium(VI) hydrolysis up to 60 °C: A multi-method spectroscopic approach", ThermAc MidTerm Workshop, 01.12.-02.12.2016, Dresden, Germany
  • M. Altmaier, F. Brandt, V. Brendler, I. Chiorescu, E. Colàs, H. Curtius, F. Endrizzi, C. Franzen, X. Gaona, M. Grivé, S. Hagemann, C. Koke, D.A. Kulik, S. Krüger, J.-Y. Lee, M. Maiwald, G.D. Miron, P.J. Panak, A. Skerencak-Frech, R. Steudtner, T. Thoenen, S. Tsushima (2016): "ThermAc - a collaborative project investigating aquatic chemistry and thermodynamics of actinides at elevated temperature conditions." Plutonium Futures, 18.-22.09.2016, Baden-Baden, Germany
  • C. Franzen, T. Haubitz, B. Drobot, T. Firkala, V. Brendler, R. Steudtner (2016): "U(VI) – SO42− complexation at elevated temperature – a combination of spectroscopy and thermodynamic modeling", Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Posters:

  • P.J. Panak, M. Altmaier, F. Brandt, V. Brendler, I. Chiorescu, E. Colàs, H. Curtius, F. Endrizzi, C. Franzen, X. Gaona, M. Grivé, S. Hagemann, C. Koke, D.A. Kulik, S. Krüger, J.-Y. Lee, M. Maiwald, A. Skerencak-Frech, R. Steudtner, T. Thoenen, S. Tsushima (2016): "ThermAc: A Joint Project on Aquatic Actinide Chemistry and Thermodynamics at Elevated Temperature Conditions." 9th international conference on nuclear and radiochemistry (NRC9), 29.08.-02.09.2016, Helsinki, Finland
  • M. Altmaier, F. Brandt, V. Brendler, I. Chiorescu, E. Colàs, H. Curtius, F. Endrizzi, C. Franzen, X. Gaona, M. Grivé, S. Hagemann, C. Koke, D.A. Kulik S. Krüger, J.-Y. Lee, M. Maiwald, P.J. Panak, A. Skerencak-Frech, R. Steudtner, T. Thoenen, S. Tsushima (2016): "ThermAc - a collaborative project on aquatic chemistry and thermodynamics of actinides at elevated temperature conditions." International Symposium on Solubility Phenomena and Related Equilibrium Processes (ISSP), 24.-29.7.2016, Genf, Schweiz
  • Bosbach, D.; Altmaier, M.; Gaona, X.; Endrizzi, F.; Brendler, V.; Steudtner, R.; Franzen, C.; Tsushima, S.; Panak, P. J.; Skerencak-Frech, A.; Hagemann, S.; Brandt, F.; Krüger, S.; Colàs, E.; Grivé, M.; Thoenen, T.; Kulik, D. A. (2016): "ThermAc: A Joint Project on Aquatic Actinide Chemistry and Thermodynamics at Elevated Temperature Conditions." Goldschmidt2016, 26.06.-01.07.2016, Yokohama, Japan
  • Altmaier, M.; Gaona, X.; Endrizzi, F.; Brendler, V.; Steudtner, R.; Franzen, C.; Tsushima, S.; Panak, P. J.; Skerencak-Frech, A.; Hagemann, S.; Brandt, F.; Krüger, S.; Colàs, E.; Grivé, M.; Thoenen, T.; Kulik, D. A. (2015): "ThermAc: A Joint Project on Aquatic Actinide Chemistry and Thermodynamics at Elevated Temperature Conditions." Migration 2015, 13.-18.09.2015, Santa Fe, NM, USA


Contact

Dr. Vinzenz Brendler
Head of Division
Surface Processes
v.brendler@hzdr.de
Phone: +49 351 260 - 2430
Fax: +49 351 260 - 3553

Dr. Nina Maria Huittinen
Surface Processes
n.huittinenAthzdr.de
Phone: +49 351 260 - 2148

Dr. Robin Steudtner
Institute of Resource Ecology
r.steudtnerAthzdr.de
Phone: +49 351 260 - 2895