Étude de la réduction de UO2F2 à haute température sous air humide et sous dihydrogène humide

The aim of this work was to clarify the reduction process of UO2F2 and to identify some intermediate compounds likely to be formed in the course of this process. Gravimetric studies have been carried out in water or molecular hydrogen atmospheres. Each compound isolated has been identified by X-Ray diffraction analysis. We first investigated the conversion of UO2F2 into U3O8 in a water partial pressure of 300 mbar at 700, 750 and 800°C. Thus, we have determinated the influence of the temperature on the reaction kinetics at a fixed vapor pressure. After identification of the two intermediates β-UO3 and UO2,9, we have proposed differents mechanims. As well, the reduction of UO2F2 in a dihydrogen atmosphere at 700°C was investigated. This reaction leads, in two steps, to the nuclear fuel by the way of U3O8

the vacuumable gel technology for the nuclear decontamination of solid surfaces state of the art and current developments for decommissioning operations.

International audienceVacuumable gels are self-drying and cracking gels which have been developed in the nuclear field. They are composed of mineral colloidal particles dispersed in a decontaminating solution. These gels can be spread on the contaminated surface and rapidly trap the radio-contaminants by sorption after eventually having corroded the substrate on several tens of microns. The gel then dries and fractures into a non-powdery solid removable by brushing or vacuum cleaning. The main advantage of this process is the only production of solid wastes;avoiding any radioactive effluents to be managed. Innovative formulations have recently emerged such as thermo-responsive gels for the decontamination of small and complex geometry items or;more recently;gels allowing the elimination of sticky contaminated bitumen stains. Vacuumable gels are implemented by spraying on the contaminated surfaces using classical pulverization devices. However;this application mode appears not always to be adequate to the encountered situations. In this way;studies are currently performed on the development of implementation modes in hostile and restrictive environments (highly contaminated zones;gloveboxes / ). The state of the art of the development of this technology is given here as well as recent advances in terms of research and development for decommissioning operations

Evidence from the Oxford Classification cohort supports the clinical value of subclassification of focal segmental glomerulosclerosis in IgA nephropathy

Focal segmental glomerulosclerosis (FSGS) is a common finding in IgA nephropathy (IgAN). Here we assessed FSGS lesions in the Oxford Classification patient cohort and correlated histology with clinical presentation and outcome to determine whether subclassification of the S score in IgAN is reproducible and of clinical value. Our subclassification of lesions in 137 individuals with segmental glomerulosclerosis or adhesion (S1) identified 38% with podocyte hypertrophy, 10% with hyalinosis, 9% with resorption droplets within podocytes, 7% with tip lesions, 3% with perihilar sclerosis, and 2% with endocapillary foam cells. Reproducibility was good or excellent for tip lesions, hyalinosis, and perihilar sclerosis; moderate for podocyte hypertrophy; and poor for resorption droplets, adhesion only, and endocapillary foam cells. Podocyte hypertrophy and tip lesions were strongly associated with greater initial proteinuria. During follow-up of patients without immunosuppression, those with these features had more rapid renal function decline and worse survival from a combined event compared to S1 patients without such features and those without FSGS. Also in individuals with podocyte hypertrophy or tip lesions, immunosuppressive therapy was associated with better renal survival. In IgA nephropathy, the presence of podocyte hypertrophy or tip lesions, markers of podocyte injury, were reproducible. These features are strongly associated with proteinuria and, in untreated patients, carry a worse prognosis. Thus, our findings support reporting podocytopathic features alongside the S score of the Oxford Classification

Photocatalysis and H2O2/UV-C - Application to nuclear wastes

SSCI-VIDE+CARE+CGU:FDA:JMHInternational audienceThe efficiency of photocatalytic methods based on TiO2 (Degussa P-25) and UV/H2O2 as means of degrading, mineralizing Ethylenediaminetetraacetic acid (EDTA) alone or complexes with radioelement and recovering the radioelement (Co) were studied under UV-C irradiation. EDTA was chosen because it is present in high proportions at nuclear facilities, where it is used for cleaning and decontamination purposes because of its chelating properties. In a first step the photonic flux of the UV-C lamps was established using actinometric and Keitzâs methods. Then adsorption capacities of TiO2 to adsorb Co complexes or not with EDTA have been studied. Finally, we compared the disappearance and mineralization rates, the intermediate by-products formed in the degradation of EDTA under UV-C photolysis, photocatalysis and H2O2/UV-C and studiedthe effect of pH. The results show that the efficiency of the UV/TiO2 and UV/H2O2 processes was found to be similar, provided H2O2 was added continuously during the UV/H2O2 process. The photonic efficiency was calculated and found to be equal to 0.9% in the case of photocatalysis and 1.4% in that of UV/H2O

Photodegradation of the radionuclide complexants

SSCI-VIDE+CARE+CGU:FDAInternational audienceThe degradation and mineralization of radionuclide complexants in nuclear liquid waste was studied by using different Advanced Oxidation Processes (AOPs). Three complexants of radionuclide were chosen for this study, tributylphosphate (TBP), dibutylphosphate (DBP) and ethylenediaminetetraacetic acid (EDTA). The efficiency of photocatalytic methods based on TiO2 (Evonik P-25) as means of degrading, mineralizing, TBP, DBP and EDTA were studied under UV-A and UV-C irradiation. In the case of EDTA, we also compared the efficiency of the photocatalytic process TiO2/UV-C and of the photolysis of H2O2 (H2O2 /UV-C) of EDTA alone and complexes with cobalt as radioelement and studied the recovery of the cobalt. In addition to HPLC, GC and TOC analysis allowing to determine the disappearance and the mineralization rates and the intermediate products formed, 31P NMR was used to follow the fate of phosphorus atom. Our results show that DBP is an intermediate product of the degradation of TBP and that the same types of carboxylic acids are formed during the degradation of TBP and DBP compounds. We also show that the kinetics of the mineralization process is described in both cases by the Langmuir-Hinshelwood model, with identical rate constants. The experiments realized with 59Co-EDTA allowed to highlight the efficiency of the UV/TiO2 and UV/H2O2 processes and to optimize them. This degradation is accompanied by an important mineralization of carbon and nitrogen initially present in EDTA and the intermediate formation of smaller molecules such as acetic acid and oxalic acids. Once separated from organic ligands, cobalt can afterwards be trapped in mineral materials in view of its storage. The efficiency of the UV/TiO2 and UV/H2O2 processes was found to be similar, provided H2O2 was added continuously during the UV/H2O2 process

Organometallic compound degradation by Advanced Oxidation Processes

Internationa

H2O2 and/or photocatalysis under UV-C irradiation for the removal of EDTA, a chelating agent present in nuclear waste waters

SSCI-VIDE+CARE+FDA:JMH:CGUInternational audienceIn this study, we compare the efficiency of photocatalytic processes based on TiO2 (Degussa P-25) and UV/H2O2 as a means of degrading and mineralizing ethyl enediaminetetraacetic acid (EDTA) under UV-C irradiation. EDTA was the molecule studied here because it is present in high proportions at nuclear facilities, where it is used for cleaning and decontamination purposes because of its chelating properties. The photonic power of the UV-C lamps used (13 and 15W) was established using actinometric and Keitz's methods. The adsorption of EDTA on TiO2 Degussa P-25 corresponds to a Langmuir isotherm, and the photocatalytic degradation process is consistent with the Langmuir-Hinshelwood model. During the photocatalytic process, an increase in the initial EDTA concentration favors the formation of large quantities of intermediates, which occupy the active sites, thus delaying the production of detectable quantities of oxalic acid. The results obtained here also show that nitrogen originating from EDTA molecules is mainly converted into ammonium and nitrate ions with a conversion rate of 67%. In addition, the amount of oxalic acid formed increases with the pH. The efficiency of the UV/TiO2 and UV/H2O2 processes as a means of EDTA degradation was found to be similar, provided H2O2 was added continuously during the UV/H2O2 process. The quantum efficiency was calculated and found to be equal to 0.9% in the case of photocatalysis and 1.4% in that of UV/H2O2. (C) 2014 Elsevier B.V. All rights reserved

Degradation of a cobalt(II)-EDTA complex by photocatalysis and H2O2/UV-C. Application to nuclear wastes containing Co-60

SSCI-VIDE+CARE+CGU:JMHInternational audienceThe Co-60 present in some low-level effluents forms complexes with organic ligands such as ethylenediaminetetraacetic acid (EDTA). These complexes make it difficult to remove the Co-60 using conventional filtration methods. The aim of this study was to test the use of titanium-based photocatalysis (TiO2/UV) and photochemical methods involving the use of oxidation agents (H2O2/UV-C) (both of which are advanced oxidation processes) to degrade EDTA and recover Co-60 once it has been released from the complex. In preliminary experiments on the Co-59-EDTA complex, we tested the efficiency of the TiO2/UV and H2O2/UV-C processes as means of degrading EDTA molecules and releasing cobalt in its cationic forms Co2+ and Co3+. These cations can be trapped by either precipitating and/or adsorbing them on TiO2 depending on the pH. When this treatment was applied experimentally to radioactive wastes, it turned out to be highly effective since it improved the decontamination factor (DF: initial volumic activity/final volumic activity) twofold