A COMPOSITIONAL INVESTIGATION OF POST-DETONATION NUCLEAR DEBRIS: RESULTS FROM IN SITU INVESTIGATIONS OF TRINITITE GLASS

The world's first atomic test, Trinity, was conducted on July 16, 1945 at the White Sands Missile Range, near Alamogordo, NM. The device, nicknamed “Gadget”, contained a ²³⁹Pu core, and was characterized by an implosion-type design. Temperatures > 8000°K were generated in the explosion, and the surrounding desert sand was fused into a glassy material known as “trinitite” (Eby et al., 2010). The latter contains both geologic materials from the test site and materials of anthropogenic origin. This investigation focused on determining the mineralogical and elemental composition of trinitite involving a number of analytical techniques - both qualitative and quantitative.

Whole rock samples were made into 60-75 μm thick thin sections. Optical petrography was performed as the basis for qualitative analysis. Thin section maps of the samples were generated in both plain polarized (PPL) and cross-polarized light (XPL). Alpha-track radiography was conducted on the thin sections using CR-39 plastic detectors to locate areas of high alpha activity, which are likely caused by residual Pu and U fuel. Scanning electron microscopy (SEM) provided further qualitative data through backscatter electron (BSE) imaging. BSE images were overlain with optical and alpha track maps, which characterized heterogeneities on the scale of tens of microns, and provided correlations between all qualitative analyses. The resulting correlations yielded areas of interest for compositional analysis. Energy dispersive X-ray spectroscopy (EDS) provided semi-quantitative major element abundances and supplied areas of additional interest for quantitative electron microprobe analysis (EMPA). Preliminary EMPA and EDS results indicate a negative correlation between areas of alpha activity and SiO₂abundances.