This title appears in the Scientific Report : 2014 

Chemical and structural investigations of BaxRa1-xSO4 on the atomic level by TEM and APT
Weber, Juliane (Corresponding Author)
Breuer, Uwe / Klinkenberg, Martina / Brandt, Felix / Savenko, Aleksei / Bosbach, Dirk
Nukleare Entsorgung und Reaktorsicherheit; IEK-6
Atom Probe & Microscopy, Stuttgart (Germany), 2014-08-31 - 2014-09-05
Helmholtz Interdisciplinary Doctoral Training in Energy and Climate Research (HITEC)
Safety Research for Nuclear Waste Disposal
Experimental studies related to long-term safety assessments for the deep geologic disposal of spent nuclear fuel suggest that Ra and the formation of the BaxRa1-xSO4 solid solution will be relevant regarding the long-term radiotoxicity. Doerner and Hoskins derived thermodynamic properties for the formation of a BaxRa1-xSO4 solid solution, e.g. the partition coefficient, from kinetically influenced co-precipitation experiments [1]. Their model is based on assumptions about the uptake and distribution of Ra in the BaxRa1-xSO4 solid. Klinkenberg et al. [2] followed a close-to-equilibrium approach and carried out ToF-SIMS analysis of the solid indicating the uptake of Ra in amounts predicted by thermodynamics. However, for a detailed investigation of the recrystallization process, nano-analytical methods need to be established. Here, we present a method development for the combined characterization of BaSO4 (barite) by atom probe tomography (APT) and transmission electron microscopy (TEM). This method will be applied to the characterization of BaxRa1-xSO4. Preparation is done by focused ion beam (FIB) from particles with a size of 10 40 µm. Since the development of the laser-assisted APT the analysis of electrically non-conductive but thermally conductive materials is possible. Non-conductivity and poor thermal conductivity of barite leaves the APT-analysis of this mineral challenging. [1] H.A. Doerner & W.M. Hoskins, Journal of the American Chemical Society,(1925), 47, 662-675.[2] M. Klinkenberg et al., Environmental Science & Technique, (2014) in review.