Güttler, Celine

► Research

BMWI joint project GraZ II: “Geochemical radionuclide retention at cement alteration phases”
The secure long-term storage of high-level waste is an actual and serious issue for the current and
future global population. Internationally, a repository using a multi-barrier system in deep geological
layers is considered for the safe storage of high-level waste, comprising a technical, geotechnical and
geological barrier. In practice, the high-level radioactive waste would be encapsulated in containers and
subsequently embedded in boreholes, for example, which are lined with sand, clay and cement-based
materials for strengthening. The boreholes are surrounded by a host rock for which granite, rock salt
and clay are considered in Germany. Within the very long period of time envisaged for the safe storage
of the high-level waste, corrosion or other processes may cause damage to the technical barrier,
resulting in a direct exposure between the geotechnical as well as geological barriers and the high-level
radioactive waste. Therefore, the investigation of the retention capacity of radionuclides at the
geotechnical and geological barrier is essential for the long-term safety assessment of a repository.
Within the scope of the research work and the project „GRaZ II“, the retention capacity of radionuclides
at the geotechnical and geological barrier is investigated at geologically relevant pH values and ionic
strengths with a particular focus on cement-based materials and their alteration products (C-S-H
phases). The evaluation of radionuclide retention in cement-based materials as well as C-S-H phases
shall be carried out using batch experiments and laser ablation in combination with ICP-MS. At the
beginning of the doctoral thesis, a valid quantification method for various solid samples, but with focus
on the C-S-H phases, shall be developed in order to realize the characterization of doped C-S-H phases.