Séparation isotopique par laser

L'enrichissement de l'Uranium consiste à augmenter la teneur de l'isotope 235 (0,7 % dans l'uranium naturel) jusqu'aux teneurs utilisables dans les réacteurs produisant l'électricité (entre 3 et 5 %) en rejetant un produit très appauvri de cet isotope (moins de 0,2 %). Cette activité importante intervient pour environ 10 % dans le coût du kWh d'origine électronucléaire c'est-à-dire pour environ 2 centimes. Exprimée en termes de marche mondial, l'activité enrichissement représente environ 25 milliards de francs. Les besoins mondiaux s'élèvent à environ 30 MUTS/an (l'UTS est l'Unité de Travail de Séparation, on retiendra que 10 UTS sont nécessaires pour produire un kg d'Uranium enrichi à 5 % à partir de 10 kg d'Uranium naturel). Ils sont couverts principalement par les procédés de diffusion gazeuse et d'ultracentrifugation. L'usine de diffusion gazeuse Georges Besse située dans la Drôme a une capacité de 10,8 MUTS/an, elle couvre le quart des besoins mondiaux. Le marche mondial se caractérise aujourd'hui par une surcapacité de production. À l'horizon 2010, les usines actuelles de diffusion gazeuse très consommatrices en énergie (2450 kWh par UTS) devront être remplacées par des usines nouvelles permettant un abaissement très significatif du coùt de l'UTS. Le procédé SILVA (Séparation Isotopique par Laser sur Vapeur Atomique) est le procédé étudié en France qui pourrait se substituer avantageusement à la diffusion gazeuse. Ce procédé, qui utilise une excitation résonnante de l'Uranium 235, se caractèrise par une séparation effectuée en une étape (1400 étapes pour la diffusion gazeuse), une consommation énergétique environ 25 à 40 fois moindre, une taille environ dix fois plus petite et un objectif de coût environ moitié de celui de la diffusion gazeuse amortie. Le CEA y consacre, en collaboration avec le futur opérateur industriel COGEMA, environ 427 millions de francs cette année. Le procédé SILVA est composé de deux grands sous-ensembles : - le séparateur qui génère la vapeur atomique, - l'atelier laser qui fournit les photons permettant l'ionisation sélective de l'Uranium 235. Un schéma de principe est représenté sur la figure 1. Ces deux entités seront décrites successivement en insistant plus particulièrement sur l'atelier laser, objet de cette présentation

Rétention of radioactive methyl iodide in the context of nuclear industry: on the quantification of isotopic exchange contribution inside activated carbons

International audienceSince the Fukushima accident, an interest has been renewed for R&D works on radioactive iodine releases mitigation by adsorbents. More particularly, the behavior of KI and TEDA co-impregnated activated carbons (AC) employed within nuclear facilities to trap volatile iodine species (I2/CH3I), is studied. Indeed, uncertainties remain about the influencing parameters and the involved retention mechanisms. We adopted complementary approach based on both experimental and theoretical investigations. Numerous techniques were used to probe the intrinsic AC properties. Moreover, a step-by-step methodology was employed for CH3I retention experiments owing to the complexity of radioactive iodine handling. Batch reactor studies were conducted first towards stable CH3I. These data were useful to probe physisorption and chemisorption phenomena. A specific model was then deduced from these studies to predict breakthrough curves for a non-impregnated AC. Efforts should be nevertheless performed to implement KI and TEDA reactions. Therefore, complex test benches (decontamination factors (DF), breakthrough curves) were developed within the PERSEE facility to study CH3127+131I dynamic adsorption on KI and TEDA simply impregnated AC. These results improve the knowledge about the role played by KI and TEDA. Indeed, TEDA was found to enhance CH3I retention under humid conditions and, for the first time, the KI contribution was isolated and quantified: the KI action towards 131I was highlighted after the breakthrough phase through an isotopic redistribution mechanism. We will attempt to finely quantify the contribution due to isotopic exchange. The challenge is to identify new synthesis strategies promoting this reaction before its kinetic modelling under various conditions

Rétention of radioactive methyl iodide in the context of nuclear industry: on the quantification of isotopic exchange contribution inside activated carbons

International audienceIn this paper, the behavior of TEDA and KI impregnated activated carbons (AC) towards the capture of methyl iodide (CH3I) is investigated using complementary methodologies. On the one hand, radioactiveCH3I decontamination factors (DF) were determined at different water vapor contents for variouscommercial activated carbons. A combination between the retention performances and the physicochemical properties is performed to gain insights about the AC influencing parameters on Y-labelled CH3I capture. On the other hand, new experimental methodologies are developed in order to measureboth stable and Y-labelled CH3I breakthrough curves (BTC) for KI or TEDA impregnated AC {T = 20 -30 °C, dry conditions}. These works improve the knowledge about the role played by KI and TEDA. Indeed, TEDA is found to enhance CH3I retention especially under humid conditions and, for the firsttime, the KI contribution is isolated and quantified: the KI action towards 131I is highlighted after the breakthrough phase through an isotopic redistribution mechanism

Infrared Spectroscopy of Ruthenium Tetroxide and High-resolution analysis of the v3 band

International audienc

On-line measurements of RuO4_4 during a PWR severe accident

International audienceAfter the Fukushima accident, it became essential to have a way to monitor in real time the evolution of a nuclear reactor during a severe accident, in order to react efficiently and minimize the industrial, ecological and health consequences of the accident. Among gaseous fission products, the tetroxide of ruthenium RuO$_4$ is of prime importance since it has a significant radiological impact. Ruthenium is a low volatile fission product but in case of the rupture of the lower head by the molten corium, the air entering into the vessel oxidizes Ru into gaseous RuO$_4$, which is not trapped by the Filtered Containment Venting Systems. To monitor the presence of RuO$_4$ allows making a diagnosis of the core degradation and quantifying the release into the atmosphere.To monitoring the presence of RuO$_4$, FTIR measurement was selected. To study the feasibility of the monitoring, high-resolution IR measurements were realized at the French synchrotron facility SOLEIL on the infrared beam line AILES. Thereafter theoretical calculations were done to simulate the FTIR spectrum to describe the specific IR fingerprint of the molecule for each isotope and based on its partial pressure in the air

High-resolution Infrared Spectroscopy and analysis of the ν₂ /ν₄ bending dyad of Ruthenium Tetroxide

International audienceRuO 4 is a heavy tetrahedral molecule of interest in several fields. Due to its chemical toxicity and radiological impact of its 103 and 106 isotopologues, the possible remote sensing of this compound in the atmosphere has renewed interest in its spectroscopic properties. We investigate here, for the first time at high resolution, the bending modes region in the far infrared. High resolution FTIR spectra have been recorded near room temperature, using a specially designed cell and an isotopically pure sample of 102 RuO 4. New assignments and effective Hamiltonian parameter fits for the main isotopologue (102 RuO 4) have been performed, treating the whole ν 2 /ν 4 bending mode dyad. We provide precise effective Hamiltonian parameters, including band centers and Coriolis interaction parameters

Hydrolyse basique du polyurethane irradie identification des produits de degradation et interaction avec l'europium(III)

National audienc

Line intensity measurements and analysis in the ν 3 band of ruthenium tetroxide

International audienc