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

CERTIFICATION REPORT: Preparation and certification of a new batch of 242Pu spike: IRMM-049e

This report describes the preparation and certification of the 242Pu spike reference material IRMM-049e, applied for determination of plutonium content in nuclear materials by isotope dilution mass spectrometry (IDMS) in nuclear safeguards, nuclear security and in the industry. As the stock of IRMM-049d is close to exhaustion, it was decided to produce about 90 ampoules of a new spike certified reference material (CRM) IRMM-049e and, therefore to maintain the provision of the IRMM-049 series of spike CRMs. IRMM-049e is the first of the IRMM-049 series produced in compliance with ISO 17034:2016. The amount content of 242Pu in IRMM-049e was characterised on 10 randomly stratified selected units by Isotope Dilution – Thermal Ionisation Mass Spectrometry (ID-TIMS) using the IRMM-1027o CRM as a spike. The plutonium isotope amount ratios were measured using the same 10 selected units by TIMS. The material was finally certified for the amount content of 242Pu and the total Pu, the mass fractions of 242Pu and total Pu, the Pu isotope amount ratios as well as the plutonium isotope abundances as amount and mass fractions, and for the molar mass of Pu in IRMM-049e. The certified values were confirmed by ID-TIMS using the IRMM-086 (239Pu spike) and verified against the reference value of the external certified test sample Pu EQRAIN-13 provided by CEA/CETAMA. These verification studies were carried out in the frame of the on-going inter-calibration campaign using state-of-the art measurement procedures linking together different JRC plutonium spike reference materials and also external reference materials to underpin the confidence in the use of JRC isotopic plutonium reference materials for safeguards verification. Between unit-homogeneity was quantified in accordance with ISO Guide 35:2006. No stability study was performed for this reference material since the general behaviour of this material is well known from past experience. However, a post-certification stability monitoring will be done every two years to control its stability after issuance of the certificate. The uncertainties of the certified values were estimated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties related to characterisation and possible inhomogeneity. The main purpose of this material is for use as a spike isotopic reference material for quantification of plutonium in an unknown nuclear sample. IRMM-049e is supplied in a screw-cap glass ampoule containing 10 mL nitric acid solution (c = 5 mol/L) with a certified plutonium (total Pu) mass fraction of (91.52 ± 0.12) µg/g and a certified 242Pu amount content of (0.35828 ± 0.00045) µmol/g. Because the IRMM-049e material is a true solution and as such, can be regarded as completely homogeneous, there is no minimum sample intake to be taken into account for the analysis.JRC.G.2-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

Meridional circulation across the Antarctic Circumpolar Current serves as a double 231Pa and 230Th trap

Upwelling of Circumpolar Deep Water in the Weddell Gyre and low scavenging rates south of the Antarctic Circumpolar Current (ACC) cause an accumulation of particle reactive nuclides in the Weddell Gyre. A ventilation/reversible scavenging model that successfully described the accumulation of 230Th in this area was tested with other particle reactive nuclides and failed to adequately describe the depth-distributions of 231Pa and 210Pb. We present here a modified model that includes a nutrient-like accumulation south of the Antarctic Polar Front in an upper meridional circulation cell, as well as transport to a deep circulation cell in the Weddell Gyre by scavenging and subsequent release at depth. The model also explains depletion of 231Pa and 230Th in Weddell Sea Bottom Water (WSBW) by ventilation of newly formed deep water on a timescale of 10 years, but this water mass is too dense to leave the Weddell Gyre. In order to quantify the processes responsible for the 231Pa- and 230Th-composition of newly formed Antarctic Bottom Water (AABW) we present a mass balance of 231Pa and 230Th in the Atlantic sector of the Southern Ocean based on new data from the GEOTRACES program. The ACC receives View the MathML source6.0±1.5×106 dpms−1 of 230Th from the Weddell Sea, similar in magnitude to the net input of View the MathML source4.2±3.0×106 dpms−1 from the north. For 231Pa, the relative contribution from the Weddell Sea is much smaller, only 0.3±0.1×1060.3±0.1×106, compared to View the MathML source2.7±1.4×106 dpms−1 from the north. Weddell Sea Deep Water (WSDW) leaving the Weddell Gyre northward to form AABW is exposed in the ACC to resuspended opal-rich sediments that act as efficient scavengers with a Th/Pa fractionation factor F≤1F≤1. Hydrothermal inputs may provide additional removal with low F. Scavenging in the full meridional circulation across the opal-rich ACC thus acts as a double 231Pa and 230Th trap that preconditions newly formed AABW

Preparation and certification of Large-Sized Dried (LSD) Spike - IRMM-1027p

IRMM Large-Sized Dried (LSD) Spikes are widely used as a fundamental part of the fissile material control of irradiated nuclear fuel and have been provided on a regular basis to safeguards authorities and industry for more than 10 years. This report describes the preparation and certification of a new batch of LSD Spikes. IRMM-1027p is a dried nitrate material in cellulose acetate butyrate (CAB), certified for the mass of uranium and plutonium and isotope amount ratios per unit. The material was produced following ISO Guide 34:2009. The certified reference materials uranium metal EC NRM 101, enriched uranium metal NBL CRM-116 and plutonium metal CETAMA MP2 were used as starting materials to prepare the mother solution. This solution was dispensed by means of an automated robot system into individual units and dried down. A solution of an organic substance, cellulose acetate butyrate (CAB), was dried on the spike material as a stabiliser to retain the dried material at the bottom of the vial. Between unit-homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. The certified values were obtained from the gravimetric preparation of the mother solution, taking into account the mass, purity and isotopic abundances of the starting materials, the mass of the mother solution, and the mass of an aliquot in each individual unit. The certified values were confirmed by isotope dilution thermal ionisation mass spectrometry (ID-TIMS) and thermal ionisation mass spectrometry (TIMS) as independent confirmation methods. Uncertainties of the certified values were estimated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties related to possible inhomogeneity and to characterisation. This spike CRM is applied as a calibrant to measure the uranium and plutonium amount content of dissolved spent nuclear fuel solutions using isotope dilution mass spectrometry (IDMS). Each unit contains about 50 mg of uranium with a relative mass fraction m(235U)/m(U) of 17.4 % and 1.8 mg of plutonium with a relative mass fraction m(239Pu)/m(Pu) of 97.8 % as dried nitrates in CAB. The whole amount of sample per unit has to be used for analysis.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

The GEOTRACES Intermediate Data Product 2014

The GEOTRACES Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEIs) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The IDP2014 covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The TEI data in the IDP2014 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including ASCII spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the IDP2014 also contains data quality flags and 1-? data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2014 data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes

NUSIMEP-9: Uranium isotope amount ratios and uranium mass in uranium micro-particles

The NUSIMEP (Nuclear Signatures Inter-laboratory Measurement Evaluation Programme) is an external quality control programme organised by the European Commission - Joint Research Centre, Directorate G – Nuclear Safety and Security, Unit G.2 for Standards for Nuclear Safety, Security and Safeguards (JRC-Geel, former IRMM), which aims at providing materials for measurements of trace amounts of nuclear materials in environmental matrices. Measurements of the uranium and plutonium isotopic ratios in small amounts, such as typically found in environmental samples, are required for nuclear safeguards, for the control of environmental contamination and for the detection of nuclear proliferation. The JRC-Geel, the Forschungszentrum Jülich (Germany) and the IAEA-SGAS (Seibersdorf, Vienna) joined forces to produce and characterise micrometre-sized uranium oxide particles, which can be used for safeguards purposes as Reference Materials (RM). In this context, JRC-Geel organised a new NUSIMEP proficiency test round, targeting more particularly the IAEA-NWAL network of analytical laboratories. However, NUSIMEP-9 was opened to all laboratories in various scientific fields. Thirty participants in NUSIMEP-9 received one certified test item, a carbon planchet on which were deposited some thousands U3O8 particles of about 1 µm diameter-size of single isotopic composition. They were requested to use their routine analytical procedures and report the n(234U)/n(238U), n(235U)/n(238U) and n(236U)/n(238U) isotope amount ratios of ten particles. Participants were also encouraged to measure and report the uranium mass per particle by measuring at least ten particles. At the end, 25 participants reported results for NUSIMEP-9. These results were evaluated against the certified reference values in accordance with ISO 13528:2015, while guaranteeing full confidentiality with respect to the link between measurement results and the participants’ identity. In general, laboratory's performances in measuring and reporting major and minor uranium isotope amount ratios in the NUSIMEP-9 particles were satisfactory. A few participants undertook to measure and report the uranium mass per particle in NUSIMEP-9 and their overall performance was satisfactory, although with a large scatter of the reported results. The final evaluation of the participant's performances in the uranium particle analysis of the NUSIMEP-9 test item, the findings and feedback of this proficiency test are presented in this report.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Uncertainty propagation in nuclear forensics

Uncertainty propagation formulae are presented for age dating in support of nuclear forensics. The age of radioactive material in this context refers to the time elapsed since a particular radionuclide was chemically separated from its decay product(s). The decay of the parent radionuclide and ingrowth of the daughter nuclide are governed by statistical decay laws. Mathematical equations allow calculation of the age of specific nuclear material through the atom ratio between parent and daughter nuclides, or through the activity ratio provided that the daughter nuclide is also unstable.The derivation of the uncertainty formulae of the age may present some difficulty to the user community and so the exact solutions, some approximations, a graphical representation and their interpretation are presented in this work. Typical nuclides of interest are actinides in the context of non-proliferation commitments. The uncertainty analysis is applied to a set of important parent-daughter pairs and the need for more precise half-life data is examined.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard