PRELIMINARY TRANSMISSION ELECTRON MICROSCOPY INVESTIGATION OF CESIUM EXCHANGE WITH NONTRONITE

¹³⁷Cs is a radioactive isotope and a component of nuclear waste. The beta decay of ¹³⁷Cs releases gamma radiation which can cause cellular damage and potentially cancer. With recent instability in North Korea and the developing nuclear technologies program in Iran, nuclear waste possessing ¹³⁷Cs is of great concern. In this investigation a ~0.1 M solution of non-radioactive ¹³³CsCl was exchanged with the smectite group member nontronite (NAu-2) from the Uley mine in South Australia. The exchange produced an opaque tan paste. A JEOL JEM-2100 transmission electron microscope (TEM) was used for the investigation in both bright field mode and scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) elemental mapping mode. TEM study of Cs-exchanged nontronite (NAu-2) indicates the mineral readily accepts Cs into its structure. Discrete crystals and turbostratic crystals of Cs-nontronite are present and three differing textures are observed; lamellar aggregates, nearly tabular particles, and irregular elongated aggregates. The lamellar aggregate texture represents approximately 80-85% of the particles, the tabular particles represent 10-15% and the irregular elongated aggregates represent 5-10% of the particle population. Energy dispersal spectroscopy (EDS) analysis indicates extensive Cs exchange with the nontronite structure. STEM-EDS analysis indicates a relatively even distribution of Cs and other elements throughout the particle as opposed to previous Cs-montmorillonite exchanges where islands of K appear. STEM analysis supports spot EDS analysis. Magnesium and sodium are dispersed evenly but possess potential patchiness in segments that correspond with each other. Current results suggest further TEM investigations of Cs interaction with other smectite minerals and related phases are warranted.