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The Israeli National Nuclear Forensics Laboratory (INNFL) investigated four unknown samples during the Collaborative Material Exercise 7 (CMX-7). The samples, identified as depleted uranium, were marked ES-1 to ES-4. ES-2 isotopic composition (0.200 ± 0.004% U-235) was different from the other samples (0.300 ± 0.003% U-235). ES-2 phase exhibited characteristics similar to metallic crystalline uranium with its appearance and assay. However, its density (16.9 ± 1.7 g/cm3) deviated significantly from metallic uranium (19.1 g/cm3). A series of analyses indicated that vanadium was present (app. 3000 ppm) in porosive areas on ES-2 surface. The oxygen isotope ratios suggested thermal processing under environmental conditions. [ABSTRACT FROM AUTHOR]

• Uranium and cerium containing samples were examined as part of an international nuclear forensics exercise. • The main technique for characterization was the combined analysis by SEM-EDS/Raman of the surface. • Connection between the ingots was determined by uranium and cerium isotopic ratios as well as yttria and graphite surface contaminations. • Sample preparation history was interpreted based on surface contaminations, showing multiple impurities present in suggested production and processing sites. The objective of this paper is to describe nuclear forensics material characterization, as conducted in the Israeli National Nuclear Forensic Laboratory (INNFL) during an international exercise Collaborative Material Exercise 6 (CMX6) organized by the Nuclear Forensics international technical working group (ITWG). The characterized materials are uranium and cerium metal ingots. The goal was characterization of physical parameters, elemental and isotopic composition, morphology and chemical composition of the surface. Electron microscopy and Raman spectroscopy techniques were combined for morphological, structural and elemental study of the surface. The information from these analyses was used to answer the exercise questions, comparing the materials (labeled ES-1 and ES-2) to each other and to other samples described in the scenario. The INNFL investigation identified a connection between ES-1 and ES-2 based on several indicators, including the isotopic composition of the uranium present in both samples, as well as other surface contaminations, mainly yttria and graphite. Based on these finding the INNFL established a connection between ES-1 and ES-2 to ES-3B (theoretical sample with uranium traces) and has not established a connection to ES-3A (theoretical sample of plutonium powder). ES1 and ES-2 have been suggestively connected to their theoretical source, by their isotopic ratio. The INNFL conclusion was that the theoretical source materials (oxide and fluoride) were converted into the actual materials. [Display omitted] [ABSTRACT FROM AUTHOR]