Applying nuclear forensics in fingerprinting of uranium-bearing materials from a South African mine

Abstract

In this work, three samples selected for investigation, originated from the Nufcor uranium plant and were analyzed for nuclear forensics using ICP-MS and SEM with EDS functionality. The samples were uranium ore, ammonium diuranate slurry, and triuranium octoxide. This research aimed to apply nuclear forensics to fingerprint uranium ores from a South African mine. The study was motivated by the fact that no previous studies had been carried out to develop forensics signatures for a nuclear forensic library for South Africanuranium mines. For the three samples used in the study, each sample was duplicated and labelled. Then, each duplicated sample was diluted ten times, making 60 sub-samples for analysis. Depending on the form samples were received from Nufcor, samples were crushed and pulverized before digested with a PerkinElmer Titan MPSTM microwave and subsequently analyzed with NexION 2000 ICP-MS and SEM/EDS.The ICP-MS was used to measure the concentration of rare-earth elements and lead isotopic ratio in each sample. The typical within-run precision measurement was less than 0.02%. Verification measurements on reference standard as a sample were performed successfully and showed good agreement with the reference values. To avoid mass biased results, mass fractionation corrections were performed using lead NIST 981 certificate reference standard and rare-earth elements SRM traceable to NIST. The lead isotopic ratio and REE results measured showed unique signatures for South Africa compared to literature. The REE patterns obtained showed that origin location reflect significant variation within the mine and thus provided valuable information about the geochemical formation and origin.The FEI QuantaTM FEG 250 electron microscope with EDS capabilities was used to perform morphology and elemental characterization of the samples. The results obtained for analysis showed large grains size distribution in micromillimeter range for all the samples. For EDS analysis in all the samples, uranium was identified as the most dominant mineral ranging from 51.6 wt.% to 56.9 wt.%. Overall, the characterization, lead isotopic ratio, REE pattern, and SEM-EDS measurements implied in uranium ore, ADU, and U3O8 are a powerful geographical signature in uranium ore, ADU, andU3O8 for uranium attribution and a powerful approach for nuclear forensics studies. The results obtained can be added into a national vi nuclear forensics library for reference purposes; since South Africa is embarking on developing and establishing a national nuclear forensic library, these results support and strengthen the initiatives.