Spatially resolved spectroscopies for the identification of interfacial processes and species of 3 - valent lanthanides and actinides

BMBF grant 02NUK089C

Duration: 01.04.2024 – 31.08.2027

Project leader: Prof. Thorsten Schäfer de

Personnel in charge: Valentin Gabert

Cooperation partners Dr. Susan Britz (GRS), Prof. Vinzenz Brendler (HZDR)


The overall aim of the project is to address deficits in the characterization and identification of sorption, incorporation and migration processes, complex structures and binding forms of the surface species. Furthermore, the solution speciation of radionuclides and repository-relevant analogues will be investigated as a function of the chemical environment; the combination of state-of-the-art spectroscopic techniques and associated method development represents the innovation of the SPIEG3L project.

The trivalent f-elements Am (III), Cm (III) and Eu (III) (which is used as chemical analogue) will be identified and characterized with respect to surface and solution complexes, local precipitation and incorporation under varying geochemical conditions directly on sediment samples and pure minerals.

In a multiphase approach, a direct coupling of time-resolved fluorescence spectroscopy (TRLFS) and other spectroscopic methods with methods for spatial resolution will be developed and carried out. The aim is a lateral and vertical spatially resolved identification of surfaces and their bonding forms, as well as solution complexes and secondary phases. This is to be done either directly after migration tests or on separately obtained drill cores, whereby the element distribution is to be determined using LA-ICP-MS.

Spectroscopic methods such as Raman or scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDX), TRLFS in conjunction with force field (AFM) will be successively used to identify the reactions at the solid-liquid interface. 3D tomography such as micro-computed tomography (µCT) and positron emission tomography (GeoPET) are also planned.

For the experiments themselves, various geochemical boundary conditions with different parameters for pH, ionic strength, ligand and/or metal concentration will be defined, which are relevant for the long-term safety assessment of potential repository sites.

In the SPIEG3L project, advective processes through saturated columns are to be considered first in order to use them directly in the SMILE joint project (BMWi FKZ 02E 11668A-C). Furthermore, classical column experiments enable the spatially resolved characterization of the species distribution directly in the columns post moretm. By working simultaneously with trivalent f elements, the assumed analogy is verified at the molecular level and, if successful, can also be transferred to elements such as Pu (III) and Np (III).

All this information provides valuable contributions to the understanding of the retention processes in the host rock; these play an important role in the assessment of radionuclide migration in the context of long-term safety assessment.