Post-doctoral position - Physical chemistry of condensed matter - NMR at CEA Grenoble

Framework. In France, bituminized waste products (BWPs) have been produced to immobilize precipitation sludges resulting from effluent decontamination operations in nuclear fuel reprocessing facilities. Part of these BWPs is intended for being stored in geological conditions. Since water should resaturate the geological storage site, studying the behavior of BWPs under leaching conditions is a key point to describe the long term behavior of these wastes in geological storage conditions. In a previous study [1] it has been shown by using Nuclear Magnetic Resonance tools that water migration in a BWP containing simultaneously salts of low and high solubility, barium sulfate and sodium nitrate respectively, leads to the formation of a heterogeneous porosity profile along the sample:

-          a first zone, close to the BWP/leachate interface, characterized by a high porosity rate and pore sizes of the order of ten micrometers;

-          a second zone, located well below the previously described one, characterized by a lower porosity rate and pore sizes of the order of micrometer;

Description and objectives. The main objective of this post-doctoral study is to determine the influence of the solubility and of the content of salts incorporated in the bituminous matrix on water migration during leaching tests of BWP. Consequences of this migration on BWP microstructure will be then evaluated. Industrial BWP and simplified BWPs, varying one from each other by the amount and nature of salts incorporated in the bituminous matrix, will be leached in pure water and in a solution similar to the solution that could be encountered in geological storage conditions. Water migration in BWP will be first evaluated by using gravimetry. 1H-NMR study will then be carried out in order to determine the water concentration profile along samples. Local dynamics properties of water (NMR relaxometry) and water molecule diffusional process along profiles concentration (PFGNMR) will also be characterized. Aging of the microstructure of BWPs during leaching test will finally be evaluated by using X-ray tomography, Environmental Scanning Electron Microscopy and Small Angles Neutrons Diffusion. These experimental results will be the basis for the development of theoretical model that would allow the description of the BWP behavior under leaching conditions.

Applicant profile: Soft-matter physical-chemistry – Polymeric materials
Good knowledge of Nuclear Magnetic Resonance techniques, especially of tools of nuclear magnetic relaxation and of field gradient experiments.
Use of data processing tools, such as Matlab for example.
Language: French - English

Place and Contacts. This post-doctoral project will take place mainly at Cea Grenoble (DSM/INAC). Further experimetns will take place at Cea Marcoule (DEN). It will be followed by A. Guillermo (SPrAM/PCI) and M. Bardet (SCIB/LRM) for their skills in NMR techniques, J.B. Champenois, A. Poulesquen, A. Dannoux-Papin (SPDE/LP2C) for BWP elaboration and their behavior during leaching tests and O. Diat (ICSM) for his knowledge of small angle diffusion techniqes (SAXS et SANS).
[1]Le Feunten et al, NMR 1D-imaging of water infiltration into mesoporous matrices, Magnetic Resonance Imaging 29 (2011) 443–455.