The characterisation of uranium materials for materials provenancing in nuclear forensics

Author: Tim Ditcham

Ditcham, Tim, 2019 The characterisation of uranium materials for materials provenancing in nuclear forensics, Flinders University, College of Science and Engineering

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This thesis describes efforts to further develop the capabilities of materials provenancing within nuclear forensics through the investigation and evaluation of new analytical techniques that may compliment or surpass the current techniques used for the analysis of chemical and elemental composition of UOCs and uranium ores. The efficacy of thermogravimetric analysis (TGA) for distinguishing between UOCs of different provenances was investigated through the analysis of eight UOCs from three different Australian uranium mines. Near-infrared spectroscopy, Raman spectroscopy and X-ray diffraction were used to identify the different compounds formed through the heating of UOC samples during TGA analysis, whilst scanning electron microscopy was used to investigate the morphologies of the eight UOC samples.

The 235U/238U and 234U/238U isotope ratios of eight UOCs and four uranium ore samples from four Australian uranium mines were analysed by multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS) to investigate whether samples from a particular location exhibited any significant intra-mine variability.

The efficacy of k0-neutron activation analysis (k0-NAA) towards the analysis of the trace and rare earth element (REE) composition of uranium ores was investigated. Fifteen of the sixteen uranium ore samples from Australia and North America and four uranium ore certified reference materials (CRMs) were analysed by k0-NAA, as pre-screening by delayed neutron activation analysis (DNAA) found that one of the samples contained a uranium concentration that would be unsafe to analyse with k0-NAA. Analysis of the CRMs and the uranium ore samples revealed that many of the REEs were significantly impacted by the presence of uranium fission products and other interferences formed during neutron irradiation. Where comparisons could be made, the chondrite-normalised REE patterns between the Australian uranium ores measured by k0-NAA and literature values from UOCs from the same locations were found to be in good agreement, with the exception of one sample.

Keywords: Nuclear forensics, uranium ore concentrate, uranium ore, thermogravimetric analysis, neutron activation analysis, delayed neutron activation analysis, multi-collector inductively-coupled plasma mass spectrometry, X-ray diffraction, scanning electron microscopy, Raman spectroscopy

Subject: Forensic & Analytical Chemistry thesis

Thesis type: Doctor of Philosophy
Completed: 2019
School: College of Science and Engineering
Supervisor: Rachel Popelka-Filcoff