Uranium and plutonium isotopic analysis in Atalante facility for the 2022-NMRoRo

International audienc

Americium isotope analysis by Thermal Ionization Mass Spectrometry using the total evaporation method: investigation of method accuracy using a new CETAMA/EC-JRC certified reference material

International audienceIn spent nuclear fuel, americium is one of the major contributors to waste long-term radiotoxicity, onceplutonium has been removed. Its isotope and concentration analysis with low uncertainty is of prime interestfor nuclear wastes management, environmental monitoring and on-site surveillance of the historicalradioactive fallout. 241Am isotope analysis is also important for nuclear forensics since it acts as a clock forplutonium separation: 241Am being a descendant of 241Pu.Thermal Ionization Mass Spectrometry (TIMS) is a reference technique for actinide isotope measurementwith high accuracy (measurement trueness and precision). The total evaporation method (TE method) is thereference technique for isotopic analysis. It consists in evaporating, ionizing and collecting the whole sampledeposited onto the TIMS filament. This method overcomes the isotope fractionation which is one of themain uncertainty sources of TIMS measurements, helps decreasing the quantity of analyte and increases themeasurement accuracy compared to the traditional method.However, americium metrological isotope analyses are scarce, due to the lack of Certified ReferenceMaterial (CRM). The CRM scarcity has limited the americium measurement uncertainty to about 0.5% andrenders the method evaluation with TIMS difficult. Considering the lack of americium CRM and ID-MSspike solution, the Analysis method establishment committee (CETAMA) of the French Atomic EnergyCommission (CEA) and the Joint Research Centre of the European Commission (EC-JRC) produced anamericium CRM with a high 243Am isotope abundance. An interlaboratory comparison (ILC) was organizedby the CETAMA in order to verify the certified values and evaluate the laboratories’ performances foramericium isotope ratio and concentration measurements.The goal of this study is to use the ILC assigned values in order to investigate the accuracy of americiumisotope measurement using the TE method by TIMS [1].Different measurements were performed on this CRM in order to determine the isotope ratios and theconcentration. 100 ng of Am was deposited onto a filament and analyzed with the TE method. The 241Am,242mAm and 243Am isotopes were collected with Faraday cup coupled to 1012 Ω current amplifier (FC12),Secondary Electron Multiplier (SEM) and Faraday cup coupled to 1011 Ω current amplifier (FC11),respectively. The detectors SEM and FC12 increase the sensitivity compared to FC11 for the isotopedetection of the lower abundance. Compared to the assigned value, a bias below 0.0001% was observed forthe 241Am/243Am isotope ratio. The uncertainty was estimated at 0.11% (k=2). The americium concentrationwas determined by isotope dilution. The bias was below 0.02% and a concentration uncertainty of 0.81%(k=2) was estimated. This study demonstrated the TIMS performance in order to perform americiumconcentration and isotope analysis with high accuracy

Analyse isotopique du néodyme dans des échantillons irradiés après séparation simultanée des lanthanides, de l'américium et du curium

International audienceDes irradiations analytiques sur des disques d’U0.85Am0.15O2 ont été menées par le CEA pour étudier lapossibilité de recycler les actinides mineurs dans de futurs réacteurs à neutrons rapide. Afind’améliorer la connaissance des données nucléaires, des analyses isotopiques des éléments Am, Cmet Nd doivent être menées sur les disques irradiés par Spectrométrie de Masse à Thermo-Ionisation(TIMS).L’une des sources de biais des mesures isotopiques réalisées par TIMS sont les interférencesisobariques. Elles conduisent à un biais analytique et peuvent être supprimées à l’aide de séparationschimiques menées par chromatographie liquide haute performance (HPLC). Dans cette étude lesconditions HPLC ont été optimisées afin d’obtenir des fractions purifiées d’Am, de Cm et de Nd à l’aided’une seule séparation réalisée sur une colonne échangeuse de cations. Comparée à la méthodeprécédemment utilisée au laboratoire requérant trois séparations HPLC et utilisant deux conditionsHPLC différentes, des améliorations ont été apportées en termes de durée et de quantité d'effluentsradioactifs générés. La validation de la méthode a ensuite été menée sur le standard isotopique de Ndnaturel JNdi-1 avant d’être appliquée avec succès aux disques irradiés issus des irradiationsanalytiques.Les valeurs de référence du standard JNdi-1 issues de la littérature sont déterminées à l’aide d’unenormalisation interne utilisée conventionnellement afin de s’affranchir du fractionnement isotopique.Néanmoins, en science nucléaire, une telle normalisation est impossible car il n’existe pas de rapportisotopique pouvant être considéré comme rapport de référence. Les données acquises sur ce standardont été comparées aux valeurs de référence à l'aide de la loi du fractionnement exponentielle, qui estun outil puissant pour détecter les biais analytiques. Les résultats montrent que les biais observésproviennent du fractionnement isotopique, ces derniers pouvant être minimisés en utilisant laméthode d’évaporation totale. Les données obtenues suggèrent la nécessité de réviser les valeurs deréférence du standard lorsque la composition isotopique du Nd est requise sans possibilité d’utiliser lanormalisation interne

Uranium and plutonium isotopic analysis in Atalante facility for the 2019-NMRoRo

International audienc

Development of an analysis method of minor uranium isotope ratio measurements using electron multipliers in Thermal Ionization Mass Spectrometry

International audienceA simple analytical procedure was developed to measure with high accuracy the isotope ratio of minor isotope of natural uranium present in small quantities using a thermal ionization mass spectrometer (TIMS). The reduction of quantities used for analysis and the measurement of non-abundant isotopes are of prime interest in the nuclear industry. Indeed it is necessary to reduce the analyst received dose and the effluent released, as well as realizing measurement at trace level. The new generation of TIMS is equipped with a multicollection system of electron multipliers: discrete dynode electron multiplier (SEM) and continuous dynode electron multiplier (MIC), that improve the sensitivity compared to faraday cups. The procedure developed was verified using Certified Reference Material IRMM 052. Results were evaluated relying on NF T 90-210 norm regarding method validation. First, the isotope ratio 234 U/ 238 U was examined by total evaporation using the SEM and MIC to measure 234 U and the faraday cup to measure 238 U. In a second approach, the isotope ratio 235 U/ 238 U was studied by total evaporation using the SEM to measure 235 U and the faraday cup to measure 238 U. The classical method with peak-jumping SEM measurement was also used. Total evaporation method employing only the faraday cup was used to confront the results obtained. The analyzable quantity was reduced from 250 ng to 50 ng for the 235 U/ 238 U isotope ratio and from 1270 ng to 50 ng for the 234 U/ 238 U isotope ratio with acceptable uncertainties thanks to the use of electron multipliers. For all experiments were the accuracy was achieved, the calculated uncertainties were below to 0.28 % for the 235 U/ 238 U isotope ratio and 5 % for the 234 U/ 238 U isotope ratio. I

Americium isotope analysis by Thermal Ionization Mass Spectrometry using the Total Evaporation Method

International audienceIn this paper, a simple analytical procedure was developed to measure americium isotope ratios and concentration with high accuracy. The method was tested during the participation in a round robin test organized by the Analytical Methods Committee of the French Atomic Energy Commission. The measurements were performed by Thermal Ionization Mass Spectrometry using the total evaporation method, which is a reference technique for determining actinide isotopic compositions. Expanded uncertainties were estimated at 0.1 % and 0.8 % for the 241 Am/ 243 Am isotope ratio and the Am concentration, respectively. Compared to the assigned value, biases below 0.0001% and 0.02% were calculated for the 241 Am/ 243 Am isotope ratio and the Am concentration, respectively

Contribution of the Faraday cup coupled to 10 12 ohms current amplifier for uranium 235/238 and 234/238 isotope ratio measurements by Thermal Ionization Mass Spectrometry

International audienceThis work highlights the possibility of improving, for given deposited quantities, the accuracy of uranium isotope ratio determination by Thermal Ionization Mass Spectrometry (TIMS) using Faraday cups coupled to a 10 12 current amplifying system. This system improves the electronic sensitivity compared to the same Faraday cups coupled to 10 11 current amplifiers. The analytical procedure developed in a previous work (Quemet et al., 2014) was applied in order to study the improvements in accuracy using the Faraday cups equipped with 10 12 current amplifier. The 234 U/ 238 U and 235 U/ 238 U isotope ratios were measured on the Certified Reference Material IRMM 052 (natural uranium). Results were evaluated relying on NF T 90-210 norm regarding method validation. The 234 U/ 238 U and 235 U/ 238 U isotope ratios were studied by total evaporation using different configurations. First, 234 U or 235 U was measured with a Faraday cup coupled to a 10 12 current amplifier and 238 U was measured with a Faraday cup coupled to a 10 11 current amplifier. Then, 234 U or 235 U was measured by discrete dynodes electron multiplier and 238 U was measured with a Faraday cup coupled to a 10 12 current amplifier. In comparison to the configurations using the 10 11 current amplifier, the analyzable quantity was reduced from 250 ng to 100 ng for the 235 U/ 238 U isotope ratio and from 50 ng to 3 ng for the 234 U/ 238 U isotope ratio with extended uncertainty below 0.28% for the 235 U/ 238 U isotope ratio, in compliance with the International Target Values (ITV 2010), and below 5% for the 234 U/ 238 U isotope ratio

Development and comparison of two high accuracy methods for uranium concentration in nuclear fuel: ID-TIMS and K-edge densitometry

International audienceThis study compares the two analytical methods for uranium concentration determination with high accuracy in uranium pellet: K-edge densitometer (KED) and the isotope dilution with Thermal Ionisation Mass Spectrometry measurements (ID-TIMS). Both techniques are compared in terms of time, generated radioactive effluent, simplicity, uncertainty estimation and detection limit. ID-TIMS shows lower detection limit and uncertainties than KED. However, the KED analysis time is shorter and generates less effluent. Both techniques were used for metrological analysis of uranium concentration in nuclear materials. The optimization of sample spike mixture isotope ratio for ID-TIMS to decrease uncertainties is also discussed

Irradiated UAmO2 transmutation discs analyses: from dissolution to accurate isotopic analyses

International audienceThis paper details the different steps for the isotopic determination of UAmO2 discs from analytical irradiation. MARIOS and DIAMINO irradiations were performed in materials testing reactors to study the behaviour of americium bearing blanket samples in regard of heterogeneous recycling in sodium-cooled fast reactor. Six irradiated discs were dissolved in hot cells and were analyzed to determine isotope ratios of uranium, plutonium, americium, curium and neodymium. The ratios were measured combining chemical separations and TIMS analyses. Using the double isotope dilution methodology helps measuring 238Pu/238U, 241Am/238U and 148Nd/238U ratios with uncertainty about a few per mil (k = 2)

Monitoring the plutonium depletion in dissolution residues of a spent fuel solution using a surrogate and plutonium isotope ratio measurements

International audienceThis study presents the development of an innovative experiment using a surrogate, for monitoring the depletion kinetics of plutonium dissolution residues in an irradiated fuel dissolution solution containing a high plutonium concentration. The surrogate, a (U,Pu)O2 compound, was synthesized from a plutonium having an isotopic composition different from the dissolution solution. This helps monitoring the plutonium residue depletion by TIMS measurements of the 240Pu/239Pu isotope ratio. Repeatability better than 83 ppm was achieved for the 240Pu/239Pu ratios in each aliquot of the dissolution profiles allowing qualitative and quantitative interpretation of the kinetic evolution that could not be reached by a conventional direct concentration determination