Mechanical properties of radiation damaged geomaterials

• Applicant: Dr. Tobias Beirau
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 374360049

Radioactive radiation can strongly modify the material properties of condensed matter. With respect to nuclear waste disposal, the better understanding of such phenomena is highly important for the assessment of the long-term stability of possible host matrix materials. Therefore, the planned project will be focused on the alpha-radiation damage related modifications of the mechanical properties, i.e., modulus and hardness, of geomaterials, which is up to now poorly understood. Revealing the correlation between specific crystal structures and their affinities to alpha-decay induced amorphization and vice versa thermally induced recrystallization, as the radiation damaged state is meta-stable, will be the main goal of the planned studies. The nanoindentation technique will allow following the variations of the materials stiffness and hardness very precisely. These results will be completed by additional spectroscopic (RUS, Raman and IR), microscopic (TEM) and calorimetric (DSC/TG) measurements. As analogues for crystalline encapsulating materials for actinide disposal natural Uranium and Thorium containing minerals (zircon, pyrochlore and allanite) with different degrees of structural damage have been chosen for this study. To better understand the damage and recrystallization process additionally artificially damaged (ion beam irradiation) zircons will be investigated in the planned studies. The chosen natural minerals have already been exposed to nuclear radiation over geological time-scales and therefore they are ideal model substances for studying the long-term influences of alpha-decay damage. The influence of radiation damage and thermally induced structural reorganization on the incorporation of water and already incorporated structural water will also be investigated, as it may play an important role for the stability. The planned project will lead to new, highly important results concerning the structural damage related modifications of the mechanical properties of geomaterials, which is an essential point for the estimation of the long-term stability.

• DFG Programme: Research Grants
• Major Instrumentation: Nanoindentationsgerät
• Instrumentation Group: 2930 Härteprüfmaschinen, Reibungs- und Verschleiß-Prüfmaschinen