A novel method has been developed for the measurement of the 34 S/ 32 S isotope ratio in uranium ore concentrate (yellow cake) samples for origin assessment in nuclear forensics. The leachable sulphate is separated and pre-concentrated by anion exchange separation followed by the 34 S/ 32 S ratio measurement by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The effect of sample composition on the accuracy was investigated and optimized. Matching of the sample to the bracketing standard was necessary to obtain accurate results. The method was validated by the measurement of standard reference materials (IAEA-S-2, IAEA-S-3 and IAEA-S-4) and the d 34 S value could be determined with an uncertainty between 0.45& and 1.9& expressed with a coverage factor of 2. The method was then applied for the analysis of uranium ore concentrates of world-wide origin. In the studied materials distinct 34 S/ 32 S isotope ratios could be observed, which can be a promising signature for the nuclear forensic investigations to identify the source of unknown nuclear materials.
A novel procedure has been developed for the measurement of (143)Nd/(144)Nd isotope ratio in various uranium-bearing materials, such as uranium ores and ore concentrates (UOC) in order to evaluate the usefulness and applicability of variations of (143)Nd/(144)Nd isotope ratio for provenance assessment in nuclear forensics. Neodymium was separated and pre-concentrated by extraction chromatography and then the isotope ratios were measured by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The method was validated by the measurement of standard reference materials (La Jolla, JB-2 and BCR-2) and the applicability of the procedure was demonstrated by the analysis of uranium samples of world-wide origin. The investigated samples show distinct (143)Nd/(144)Nd ratio depending on the ore type, deposit age and Sm/Nd ratio. Together with other characteristics of the material in question, the Nd isotope ratio is a promising signature for nuclear forensics and suggests being indicative of the source material, the uranium ore.
The paper describes the preparation and production of the reference materials, IRMM-1000a and IRMM-1000b, certified for the production date based on the 230Th/234U radiochronometer in compliance with ISO Guide 34:2009. The production date of the reference materials corresponds to the last separation of 230Th from 234U, i.e. when the initial daughter nuclide content in the material was finally removed. For the preparation low-enriched uranium was used, which was purified using a unique methodology to guarantee high U recovery and Th separation efficiency. The CRM is intended for calibration, quality control, and assessment of method performance in nuclear forensics and safeguards.
The paper describes the applicability of different characteristics (signatures) in nuclear safeguards and forensics for assessment of uranium material provenance in terms of production process. The study follows a uranium ore concentrate production from an ore to a U3O8 product. It turned out that rare-earth elemental pattern, radiochronometry (age of ore body and material production date), sulphur and organic impurities are useful to find out the origin or history of the material, while certain trace-elements and isotopics of Pb or Sr were found to be inconclusive. The results will be important to understand the signatures in nuclear safeguards and forensics.Electronic supplementary materialThe online version of this article (doi:10.1007/s10967-017-5247-5) contains supplementary material, which is available to authorized users.
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