Comparative Investigation between In Situ Laser Ablation Versus Bulk Sample (Solution Mode) Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Analysis of Trinitite Post-Detonation Materials

In the event of the interception of illicit nuclear materials or detonation of a nuclear device, timely and accurate deciphering of the chemical and isotopic composition of pertinent samples is pivotal in enhancing both nuclear security and source attribution. This study reports the results from a first time (to our knowledge), detailed comparative investigation conducted of Trinitite post-detonation materials using both solution mode (SM) and laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS) techniques. Trace element abundances determined for bulk Trinitite samples subsequent to digestion and preparation for SM-ICP-MS analysis compare favorably to calculated median concentrations based on LA-ICP-MS analyses for the identical samples. The trace element concentrations obtained by individual LA-ICP-MS analyses indicate a large scatter compared to the corresponding bulk sample SM-ICP-MS results for the same sample; this feature can be attributed to the incorporation into the blast melt of specific, precursor accessory minerals (minerals in small quantities, such as carbonates, sulfates, chlorites, clay, and mafic minerals) present at ground zero. The favorable comparison reported here validates and confirms the use of the LA-ICP-MS technique in obtaining accurate forensic information at high spatial resolution in nuclear materials for source attribution purposes. This investigation also reports device-like Pu-240/Pu-239 ratios (approximate to 0.022) for Pu-rich regions of the blast melt that are also characterized by higher Ca and U contents, which is consistent with results from previous studies.