Employing methods that aid in tracking down illicit nuclear materials, such as uraninite (UO<sub>2</sub>) or uranium ore concentrate (UOC), are of utmost importance in forensic analyses for source attribution purposes. Natural uranium ores and UOCs are part of the early stages of the nuclear fuel cycle and constitute commonly intercepted materials. Consequently, there is a need to better understand and document the forensic signatures of different ore types such that an origin can be determined for seized illicit nuclear materials. Recently, several studies have successfully attributed uranium ores and UOCs to specific mining/geographic areas based on trace element abundances (e.g., rare earth elements-REEs) and isotopic (Sr, U) fingerprinting. Uranium ore and UOCs are also known to contain a myriad of trace elements that persist as impurities through the enrichment process, such as aluminum, calcium, potassium among others. Moreover, natural uraninite is commonly associated with secondary Ca- and Fe-rich alteration zones/phases that are characterized by variable REE contents. Hence, this study represents a first-time investigation of the Ca and Fe isotope signatures of natural uraninite and its associated alteration products, with the primary objectives being three-fold: 1- Establish baseline Ca and Fe isotopic signatures for U deposits worldwide; 2- Better understand the physical conditions (temperature, redox) involved with uraninite formation and its subsequent alteration; and 3- Determine the feasibility of Ca and/or Fe isotope measurements as forensic signatures of nuclear materials for source attribution purposes.

Calcium and iron isotope analysis of uraninite and other uranium-rich materials: Development of potential new forensic isotope tracer methods

255th National Meeting (2018)

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