| Abstrakt: |
This study details thermal reactions between glasses, common minerals, and Trinitite post-detonation material with the fluorinating agent nitrogen trifluoride ( NF3). The ultimate goal of our investigation is to develop a relatively rapid method for the effective separation of bomb components from complex matrices resulting from a nuclear explosion. Trinitite samples, silicate minerals (quartz; plagioclase and microcline), amorphous SiO2, calcite, a natural glass (obsidian), and two synthetic glasses were characterized extensively before and after the fluorination to fully understand the effects of the NF3 thermal treatment. Samples were reacted with NF3 using a combined thermogravimetric (TG) differential thermal analysis (DTA) unit, as well as in a stainless steel bomb reactor connected to a fluorination line. Subsequent to the NF3 treatment, samples were imaged by scanning electron microscopy in order to document changes in grain size and morphology. Energy dispersive spectroscopy was performed to determine changes in major element abundances. Results demonstrate that rates of reaction are dependent on grain size, temperature, pressure, and time of fluorination. All mineral samples experienced mass loss during fluorination. Specifically, amorphous SiO2 (~?90% mass loss) experienced the most while calcite experienced the least (~?18%). Major element analysis reveals that mass loss is attributable to the volatilization of silica (SiO2) in Si-bearing phases, or sample decomposition in calcite due to fluorination. Results for fluorinated samples of Trinitite demonstrate that mass loss occurs at different rates for each sample, but each sample experienced an expected large decrease in Si content (resulting from volatilization of SiF4). Hence, the concentration of metals in the residual material increased due to the volatilization of Si. These results validate that this thermal-fluorination technique allows the separation of silica from minerals (i.?e. naturally occurring crystalline materials) and glasses (i.?e. amorphous materials), leaving behind non-volatile fluorinated species and refractory phases. The results from our investigation clearly indicate that the NF3 treatment of nuclear materials is a technique that provides effective separation of bomb components from complex matrices (e.?g. post-detonation samples), which will aid with rapid and accurate source attribution. [ABSTRACT FROM AUTHOR] |
