Development of a versatile sample preparation method and its application for rare-earth pattern and Nd isotope ratio analysis in nuclear forensics

An improved sample preparation procedure for trace-levels of lanthanides in uranium-bearing samples was developed. The method involves a simple co-precipitation using Fe(III) carrier in ammonium carbonate medium to remove the uranium matrix. The procedure is an effective initial pre-concentration step for the subsequent extraction chromatographic separations. The applicability of the method was demonstrated by the measurement of REE pattern and 143Nd/144Nd isotope ratio in uranium ore concentrate samples.JRC.E.7-Nuclear Safeguards and Forensic

Preparation and certification of IRMM-1000a (20 mg) and IRMM-1000b (50 mg) - Certified uranium reference material for the production date

This report describes the development and certification of IRMM-1000a and IRMM-1000b, a uranium reference material certified for the production date based on the 230Th/234U radiochronometer. The certified value was assigned following ISO Guide 34:2009 [ ]. The starting material was low-enriched uranium with a relative mass fraction, m(235U)/m(U) of 3.6%. The chemical separation of the 230Th decay product from its parent nuclide 234U to the maximum extent of completeness was achieved. The certified production date was confirmed using the 230Th/234U radiochronometer, and corresponds to the last chemical separation, i.e. the removal of 230Th from the material to the maximum extent achievable. The between unit-homogeneity and the stability of the certified value were assessed in accordance with ISO Guide 35:2006 [ ]. The material was characterised by taking into account the date and time elapsed of the last chemical and complete separation of 230Th from 234U. The completeness of the separation was confirmed firstly by determining the U/Th separation factors and uranium recoveries using -ray spectrometry, and then by means of ICP-MS measurements using a 232Th tracer. After sufficient ingrowth of thorium into the characterised uranium reference material, measurements of the 234U and the 230Th amount contents were carried out by isotope dilution mass spectrometry (IDMS) in compliance with ISO/IEC 17025:2005 [ ]). Subsequently, the determined n(230Th)/n(234U) was used in the calculation to confirm the certified production date. The uncertainty of the certified value was estimated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) [ ] and includes uncertainties related to characterisation, possible inhomogeneity and instability. The material is intended for calibration of methods, quality control, and assessment of method performance with isotope mass spectrometry and radiometry techniques. As any reference material, it can also be used for control charts or validation studies. The certified reference material is available in two sizes: 20 mg (IRMM-1000a) and 50 mg uranium (IRMM-1000b) as dried uranyl nitrate in screw-cap Teflon (PFA) vials. There is no minimum sample intake to be taken into account.JRC.D.2-Standards for Innovation and sustainable Developmen

IRMM-1000a and IRMM-1000b: uranium reference materials certified for the production date based on the 230Th/234U radiochronometer Part II: Certification

The IRMM-1000a and IRMM-1000b uranium reference materials, of 20 mg uranium and 50 mg uranium, respectively, were produced by the European Commission Joint Research Centre’s Institute for Reference Materials and Measurements (EC-JRC-IRMM) in collaboration with the Institute for Transuranium Elements (EC-JRC-ITU). They are the first uranium reference materials certified for the production date based on the 230Th/234U radiochronometer, i.e. the date of the last chemical separation of these two radionuclides. Such certified reference materials (CRMs) are required for proper validation of measurement procedures in Nuclear Forensics in order to determine the "age" of uranium samples and to establish traceability of the measurement results to the SI. The certified reference value and its uncertainty, homogeneity and stability of the material were established in accordance with the ISO Guide 34:2009 and the 'Guide to the Expression of Uncertainty in Measurement'.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

REIMEP-22 U age dating - Determination of the production date of a uranium certified test sample Inter-laboratory comparison, Report to participants

The REIMEP-22 inter-laboratory comparison (ILC) "U Age Dating - Determination of the production date of a uranium certified test sample" was organised by JRC-IRMM as support to the Nuclear Forensics International Technical Working Group (ITWG) This ILC was organised prior to the release of the candidate certified reference material IRMM-1000, produced in cooperation with JRC-ITU. The aim of REIMEP-22 was to determine the production date of the uranium certified test sample (i.e. the last chemical separation date of the material) using the disequilibrium between the 230Th-234U and 231Pa-235U nuclides as chronometers. The first was compulsory, the latter optional. Participants in REIMEP-22 received either a 20 mg or 50 mg low-enriched uranium sample of known age in solid uranyl nitrate form, depending on the type of analytical technique they used. Participating laboratories were asked to measure and report either the isotope amount ratio n(230Th)/n(234U) for the 20 mg uranium samples or the activity ratio A(230Th)/A(234U) for the 50 mg uranium samples and to report the calculated production date of the certified test samples. The participants were asked to apply their standard analytical procedures and report the results with the associated uncertainties. REIMEP-22 was announced to participants in June 2013 and fourteen laboratories registered for REIMEP-22 by October 2013. The shipment of the samples to the participants took place between December 2013 and late January 2014. Finally, by May 2014, nine laboratories reported results for the 20 mg uranium sample (using mass spectrometry and reporting amount ratios) and four laboratories for the 50 mg uranium sample (using gamma-spectrometry and reporting activity ratios). The reported measurement results have been evaluated against the certified reference value by means of zeta-scores in compliance with international guidelines. In general the REIMEP-22 participants' results were satisfactory. This report presents the REIMEP-22 participants' results; including the evaluation of the questionnaire.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

On the Use and Limitations of Age Dating in Nuclear Safeguards and Forensics: State-of-the- Practice and the Way Forward

The present work describes the current status and practices of the production date measurement of natural uranium materials. Although the age dating for nuclear safeguards and forensics is proven to work well for enriched and highly purified materials, severe discrepancies can be found for natural uranium (non-enriched) samples. This is caused by the incomplete separation and the effect of residual decay products in the final nuclear product. The current study presents the dating results obtained for various uranium-based nuclear materials (uranium core concentrates, UO3, UO2, UF4, and UF6) with known production dates from the front-end of the nuclear fuel cycle. The findings highlight the practical limitations and further analytical improvement needs for the age measurement of uranium-based materials. The work can serve as a basis for the implementation of reliable and adaptable age measurement in the tool-kit of nuclear safeguards and forensics in the future.JRC.E-Institute for Transuranium Elements (Karlsruhe

Pre-concentration of Trace Levels of Rare-Earth Elements in High Purity Uranium Samples for Nuclear Forensic Purposes

This paper describes the development of a method for the pre-concentration and analysis of trace-level amounts of rare-earth elements (REE) in high purity uranium (U) samples. The method comprises pre-concentration and subsequent group separation of REEs from the uranium matrix followed by their quantitative determination using inductively coupled plasma mass spectrometry. The achieved detection limit of the method (in the low pg/g range) in combination with the high chemical recovery (around 90%) enabled the investigation of REE pattern in high purity refined uranium oxides. Applying this method one could follow the REE pattern along the entire front-end of the nuclear fuel cycle.JRC.G.II.6-Nuclear Safeguards and Forensic

Application of Neodymium Isotope Ratio Measurements for the Origin Assessment of Uranium Ore Concentrates

A novel procedure has been developed for the measurement of 143Nd/144Nd 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 143Nd/144Nd 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 143Nd/144Nd 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.JRC.E.7-Nuclear Safeguards and Forensic

Strategies for DNA Analysis from Contaminated Forensic Samples

The capability of a standard forensic DNA purification kit (Charge Switch Forensic DNA Purification Kit, Invitrogen, USA) to decontaminate DNA samples from radionuclides typical for nuclear security scenarios was investigated with the aim to achieve sufficient decontamination for further processing the purified DNA sample in a standard forensic laboratory. It could be shown that measurement of the radionuclide in the initial lysis solution in combination with the decontamination factor for the investigated radionuclide allows demonstrating compliance with the necessary clearance limits for the purified DNA samples. Thus, we propose a strategy for analysing R/N contaminated DNA samples by separating DNA using the well-established Charge Switch method in a nuclear laboratory and then transferring the DNA to a forensic laboratory for further analysis.JRC.E.7-Nuclear Safeguards and Forensic

Measurement of sulphur isotope ratio (34S/32S) in uranium ore concentrates (yellow cakes) for origin assessment

A novel method has been developed for the measurement of the 34S/32S isotope ratio in uranium ore concentrate (yellow cake) samples for the origin assessment in nuclear forensics. The leachable sulphate is separated and pre-concentrated by anion exchange separation followed by the 34S/32S ratio measurement using 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 d34S 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 34S/32S isotope ratios could be observed, which can be a promising signature for the nuclear forensic investigations to identify the source of unknown nuclear materials.JRC.E.7-Nuclear Safeguards and Forensic

IRMM-1000a and IRMM-1000b uranium reference materials certified for the production date. Part I: Methodology, preparation and target characteristics

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. 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. The certified reference materials were produced jointly by the European Commission Joint Research Centre Institute for Transuranium Elements (EC-JRC-ITU) and Institute for Reference Materials and Measurements (EC-JRC-IRMM) in compliance with ISO Guide 34:2009. For the preparation low-enriched uranium was used, which was purified using a unique methodology to guarantee high U recovery and high Th separation efficiency. The complete elimination of Th from the initial material was verified by gamma spectrometry, by the addition of 232Th tracer to the starting material and its re-measurement from the final product and by the age dating of the freshly prepared material a few days after preparation. The reference material was produced in two sizes containing 20 mg uranium and 50 mg uranium, distributed by EC-JRC-IRMM as IRMM-1000a and IRMM-1000b. The CRM is intended for calibration of methods, quality control, and assessment of method performance with isotope mass spectrometry and radiometry techniques for uranium materials in nuclear forensics and safeguards.JRC.E.7-Nuclear Safeguards and Forensic