Development of Uranium Reference Particles to Support Nuclear Safeguards

Controlled hydrolysis of certified uranium hexafluoride, carried out in a specifically constructed aerosol chamber, leads to the production of uranyl fluoride particulates which ¿deposited on a graphite planchet support ¿ may be used as a quality control reference material. The particle size and surface distribution depends on several parameters, such as relative humidity inside the aerosol chamber and the concentration of gaseous uranium hexafluoride, determined by the distillation conditions. The best quality samples were obtained a RH ranging from 55 to 70% and low gas amount. These improvements for a single deposition were used to prepare a reference sample with two different uranium enrichments. Preliminary SIMS measurements proved good results with respect to both type of particles. It was also revealed that ¿ in some case ¿ the micrometer size uranium particles are accompanied by a large medium background.JRC.DG.D.2-Reference material

Ischemic cardiomyopathy revealed by central retinal artery occlusion (CRAO)

Here we report a case of central retinal artery occlusionrevealing an ischemic cardiomyopathy. A 54-year old smoker man presented at the hospital because of sudden visual loss in his left eye. There was cherry-red spot in the macula in his left eye. We performed a fluorescein angiogram and cervical color Doppler. Later   investigations revealed an ischemic cardiomyopathy undiagnosed until then.Key words: Central retinal artery occlusion, ischemic cardiomyopathy, cardiac thrombu

Etude des Processus d'Evaporation et d'Ionisation de l'Uranium - Thèse Présentée pour l'Obtention du Grade de Docteur en Sciences de l'Université Louis Pasteur de Strasbourg

Développer des compétences et mettre en place des équipements destinés à l'analyse de quantités de matière extrêmement faibles. Ainsi, on a vu s'accroître la capacité de détecter des traces provenant d'activités anthropogéniques telles que les empreintes produites par des processus d'origine industrielle dans des échantillons de l'environnement. Une application très spécifique de ces techniques analytiques utilisées dans l'analyse de traces et d¿ultratraces consiste à mesurer les rapports d¿abondances isotopiques de l¿uranium. Cette application permet de dévoiler les activités liées à l¿enrichissement de l¿uranium en recourant au prélèvement d¿échantillons de frottis au sein ou en proximité d¿une installation nucléaire. Dans ce domaine, l¿analyse de particules d¿uranium individuelles constitue un puissant moyen d¿investigation introduit pour la vérification nucléaire. Cependant, un des défis majeurs auxquels les analystes se trouvent confrontés est lié aux dimensions desdites particules qui exhibent la plupart du temps un diamètre extrêmement faible (inférieur à 1 µm) associé à une teneur en uranium de l¿ordre des sub-picogrammes. Il s¿ensuit alors que même les appareils de mesure les plus sensibles doivent être utilisés au voisinage de leurs limites de détection instrumentale.JRC.E.8-Nuclear safeguards and Securit

Development of an Improved Method to Perform Single Particle Analysis by TIMS for Nuclear Safeguards

A method is described that allows measuring the isotopic composition of small uranium oxide particles (less than 1 µm in diameter) for nuclear safeguards purposes. In support to the development of reliable tools for the identification of uranium and plutonium signatures in trace amounts of nuclear materials, improvements in Scanning Electron Microscopy (SEM) en Thermal Ionization Mass Spectrometry (TIMS) in combination with filament carburization and Multiple Ion Counting (MIC) detection were investigated. The method that has been set up enables the analysis of single particles by a combination of analytical tools, thus yielding morphological, elemental and isotopic information. Hereby individual particles of certified reference materials containing uranium at femtogram levels were analyzed. The results should that the combination of techniques proposed in this work is suitable for the accurate determination of uranium isotope ratios in single particles with improved capabilities for the minor abundant isotopes.JRC.DG.D.2-Reference material

On the mechanism of indium(III) complex formation with metallochromic indicators

The equilibria and kinetics of the interaction of In(III) with Alizarin Red S (ALZS) and Methyl Thymol Blue (MTB) dyes in aqueous solution were investigated. Spectrophotometric titrations at different pHs (1.8–2.7 range) revealed that, concerning the In-ALZS system, under conditions of metal excess the prevailing complex is ML, while stopped flow experiments have shown that, in the investigated pH range the kinetics are monophasic although the ML complex is formed through different paths involving both In(H2O)63+ and In(H2O)5(OH)2+ as active species reacting with the monoprotonated ligand (HL). The In-MTB system was studied with the same methodology in the pH range 1.0–2.0. The complex (MH3L) prevails although the above metal species react with differently protonated forms of the ligand. The In-MTB system displays a biphasic kinetic behavior involving a network of reaction steps, where fast pre-equilibria related to metal coordination at the carboxylates/nitrogen site, precedes slow coordination at the phenol/phenol or phenol/quinone sites. The key role in the reaction mechanism is played by the ligand features rather than by the solvent/ligand substitution process

Certified reference materials and reference methods for nuclear safeguards and security

Confidence in comparability and reliability of measurement results in nuclear material and environmental sample analysis are established via certified reference materials (CRMs), reference measurements, and inter-laboratory comparisons (ILCs). Increased needs for quality control tools in proliferation resistance, environmental sample analysis, development of measurement capabilities over the years and progress in modern analytical techniques are the main reasons for the development of new reference materials and reference methods for nuclear safeguards and security. The Institute for Reference Materials and Measurements (IRMM) is one of the leading institutes that supplies nuclear reference materials to fulfill the existing requirements for nuclear material and environmental sample analyses. IRMM’s activities range from the preparation and certification of large quantities of the so-called "large-sized dried” (LSD) spikes for accurate measurement of the uranium and plutonium amount content in dissolved nuclear fuels by isotope dilution mass spectrometry (IDMS), over certified synthetic uranium isotope mixtures, to the development of particle reference materials applied for the detection of nuclear signatures in environmental samples. IRMM is currently replacing some of its exhausted stocks of CRMs with new ones whose specifications are up-to-date and tailored for the demands of modern analytical techniques. Some of the existing materials will be re-measured to improve the uncertainties associated with their certified values, and to enable laboratories to reduce their combined measurement uncertainty. Furthermore, IRMM initiated and coordinated the development of a Modified Total Evaporation (MTE) technique for accurate measurements of minor isotope-amount ratios of uranium and plutonium in nuclear material and, in combination with a multi-dynamic measurement technique and filament carburization, in environmental samples. Currently IRMM is engaged in a study on the development of plutonium reference materials for “age dating”, i.e. determination of the time elapsed since the last separation of plutonium from its daughter nuclides. The decay of a radioactive parent isotope and the build-up of a corresponding amount of daughter nuclide serve as chronometer to calculate the age of a nuclear material. There are no such certified reference materials available yet.JRC.D.2-Standards for Innovation and sustainable Developmen

Uranium hexafluoride (UF6) gas source mass spectrometry for certification of reference materials and nuclear safeguard measurements at IRMM

Uranium hexafluoride gas source mass spectrometry at IRMM is based on two foundations, firstly the operation of a UF6 gas source mass spectrometer (GSMS) and secondly the preparation of primary UF6 reference materials, which were converted from gravimetrically prepared mixtures of highly enriched oxides of 235U and 238U. Recently a new GSMS for uranium isotopic measurements using UF6 gas, the "URANUS" from Thermo Fisher, was installed at IRMM, which also allows measurements of the so-called "minor" isotope ratios n(234U)/n(238U) and n(236U)/n(238U). In this paper the design and the implementation of measurement techniques for the new URANUS GSMS are described. This includes the "single standard" and the "double standard" (DS) method as well as the newly developed "memory corrected double standard" method (MCDS). This required a detailed investigation of memory effects within the GSMS instrument, in particular regarding the dependence of memory effects on the isotope ratios of samples and standards. The results of this study led to new recommendations for the selection of the standards for a given sample and for suitable measurement procedures. The measurement performance for the "major" isotope ratio n(235U)/n(238U) as well as the “minor” isotope ratios n(234U)/n(238U) and n(236U)/n(238U) is presented and compared with other mass spectrometric techniques. With the installation and validation of the new URANUS GSMS instrument IRMM has established two new complementary techniques for measuring the full isotopic composition of uranium samples. UF6 GSMS in combination with the MCDS method is considered the preferred technique for samples in the UF6 form and for smaller uncertainties for measurements of the major ratio n(235U)/n(238U), while thermal ionization mass spectrometry (TIMS), in combination with the "modified total evaporation" (MTE) method as well as ion counting and high abundance sensitivity for the detection of 236U, provides a superior measurement performance for the minor isotope ratios n(234U)/n(238U) and n(236U)/n(238U).JRC.D.2-Standards for Innovation and sustainable Developmen

Analysis of Single Micro-Sized Uranium Particles by Thermal Ionization Mass Spectrometry

In this work, a method is described that allows measuring the U enrichment in small uranium oxides particles (less than 1 µm in diameter) by the use of Thermal Ionization Mass Spectrometry (TIMS). This project is driven by the need of improving IRMM's capabilities in the area of low-level isotopic analysis for the support in "Environmental Sampling" for nuclear safeguards. The particle manipulation and analysis techniques presented here enable the examination of a single particle of interest by a combination of analytical techniques, thus yielding surface morphological, elemental and isotopic information. Individual particles of NUSIMEP-6 and NBS-200 samples containing pg-size amounts or uranium were analyzed. First experimental data showed the technique used in this work was an accurate method for the determination of the U isotope ratios, including the minor isotopes, which were derived with good precision.JRC.DG.D.2-Reference material

Filament Chemistry of Uranium in Thermal Ionisation Mass Spectrometry

In this work, the filament chemistry of uranium was investigated under conditions encountered in thermal ionisation mass spectrometry (TIMS), using a rhenium filament material without the addition of ionisation enhancers. The investigations were conducted using several analytical techniques such as X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and the modified-Knudsen Cell Mass Spectrometry (KCMS). The techniques provide useful information on the mechanisms associated with uranium evaporation and ionisation using a rhenium filament as surface ionisation source. The experimental results showed the sample behaviour to be consistent with the existence of a typical UO2 phase forming on the filament surface. The composition of the resulting vapour phase is dominated by the presence of uranium oxide species, with a smaller fraction of uranium ions.JRC.E.7-Nuclear Safeguards and Forensic

Investigation of Uranium Isotopic Signatures in Real-Life Particles from a Nuclear Facility by Thermal Ionization Mass Spectrometry

An improved method was recently developed for the isotopic analysis of single-reference uranium oxide particles for nuclear safeguards. This method is a combination of analytical tools including in situ SEM micromanipulation, filament carburization and multiple ion counting (MIC) detection, which is found to improve sensitivity for thermal ionization mass spectrometry (TIMS) isotope ratio analysis. The question was raised whether this method could be applied for the detection of nuclear signatures in real-life particles with unknown isotopic composition. Therefore, environmental dust was collected in different locations within a nuclear facility. The screening of the samples to find the uranium particles of interest was performed using a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray (EDX) detector. The comparison of the measurement results to reference data evaluated by international safeguards authorities was of key importance for data interpretation. For the majority of investigated particles, detection of uranium isotopic signatures provided information on current and past nuclear feed operations that compared well with facility declarations.JRC.DG.D.2-Reference material