Nuclear Forensics Signatures of Uranium Oxides from Aqueous Solution Reprocessing

The field of nuclear forensics is dedicated to the investigation of nuclear materials for the purposes of national and international security. Investigations in the field include the characterisation of intercepted radiological materials, to determine their origin, processing history and trafficking route. Findings can be used in the wider legal framework, as evidence to support legal proceedings and prosecution. It is therefore necessary that materials of potential interest are characterised for their nuclear forensic signatures, which serve as fingerprints of processing history, so that comparisons may be drawn between intercepted materials and materials of known provenance. Nuclear forensic signatures include, but are not limited to, particle morphology, microstructure and physical characteristics, such as colour.
In this thesis, nuclear forensic signatures for the preparation uranium oxides, chiefly U2O7, UO3 and U3O8, are investigated in respect of the precipitation intermediate used: uranyl peroxide tetrahydrate (studtite) or uranyl oxalate. Their nuclear forensic signatures are analysed within the context of aqueous reprocessing and thermal treatment at the back-end of the nuclear fuel cycle (NFC). In this part of the NFC, spent nuclear fuel is dissolved in nitric acid and converted to stable uranium oxides for eventual interim storage. This is often achieved via intermediates such as those examined here.