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Nuclear Magnetic Resonance study of bituminous waste products under leaching conditions

Mardi 28 novembre 2017 13:30 - Duree : 1 heure
Lieu : LNCMI, salle de conférences "René Pauthenet" (bâtiment J, 2ème étage) - 25 rue des martyrs - 38000 Grenoble

Orateur : Rémi BLINDER (Univ. Grenoble Alpes, CEA, INAC-MEM, UMR 9001)

During the last decades, some nuclear wastes of low/intermediate activity level produced by the French nuclear industry have been incorporated into a bituminous matrix. The behavior under leaching conditions of the resulting bituminous waste product (BWP), composed of 60 wt % of bitumen and 40 wt % of salts and synthesized by extrusion process, is a key issue for their acceptability into a geological disposal. The current models of the leaching process only describes the water uptake induced by the dissolution of soluble salts [1-3]. Nevertheless, an earlier experimental study [4] of simplified BWP containing either BaSO4 –insoluble- or NaNO3 –soluble- salts (or a combination of both), has shown that the incorporation of insoluble salts induces, for a given mass fraction, an enhancement in the water uptake, both seen in the increased water quantity and in the depth of the progression front. It reveals the existence of a new leaching mechanism which has yet to be considered in the theoretical models. The present work aims at better characterizing this mechanism, as well as describing its quantitative effect on the behavior of the industrial matrices. In this respect, we use Pulsed-Field Gradient Nuclear Magnetic Resonance (PFG-NMR), typically on the proton (1H) nucleus. It is an advantageous technique as it allows : (1) to establish water concentration profiles, using a simple 1D-imaging sequence, and (2) to measure the water self-diffusion coefficient. The former allows to monitor the water progression as it evolves on long (months) timescales while the latter provides short timescale information related to the microscopic porosity of the medium. In this presentation, I will discuss results that were obtained on industrial matrices using PFG-NMR, as well as other complementary techniques such as Environmental Scanning Electron Microscopy. These results will be discussed in the light of other results, obtained on various simplified BWP, differing by the solubility/granulometry of the embedded salts.

References

[1] J. Sercombe, B. Gwinner, C. Tiffreau, B. Simondi-Teisseire, F. Adenot, Journal of Nuclear Materials, 349 (2006) 96-106

[2] B. Gwinner, J. Sercombe, C. Tiffreau, B. Simondi-Teisseire, I. Felines, F. Adenot, Journal of Nuclear Materials, 349 (2006) 107-118

[3] N. Mokni, S. Olivella, X. Li, S. Smets, E. Valcke, Physics and Chemistry of the Earth, 33 (2008) 436-443

[4] S. Le Feunteun, O. Diat, A. Guillermo, A. Poulesquen, R. Podor, Magnetic Resonance Imaging, 29 (2011) 443-455

Contact : anne-laure.barra@lncmi.cnrs.fr

Discipline évènement : (Physique)
Entité organisatrice : (LNCMI)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire LNCMI)
Site de l'évènement : Polygone scientifique

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