Radiation damages on mesoporous silica thin films and bulk materials
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Radiation damages on mesoporous silica thin films and bulk materials X. Deschanels1, S. Dourdain1, C. Rey1, G. Toquer1, A. Grandjean1, S. Pellet-Rostaing1 and O. Dugne2 and C. Grygiel3 and F. Duval4 and Y. Serruys5 1 Institut de Chimie Séparative de Marcoule, UMR5257 CEA-CNRS-UM2-ENSCM, F-30207 Bagnols sur Cèze, France. 2
CEA Marcoule-DTEC, F-30207 Bagnols-sur-Cèze, France.
3
CIMAP, CEA-CNRS-ENSICAEN-UCBN, F-14070 Caen Cedex 5, France.
4
CNRS, CEMHTI, UPR3079, F-45071 Orleans 2.
5
CEA, DEN, Serv Rech Met Phys, Lab JANNUS, F-91191 Gif Sur Yvette, France.
ABSTRACT Mesoporous silicas are highly potential materials for applications in the nuclear field like separation, recycling or nuclear wastes confinement. In this work, the effects of the radiation damage on the mesoporous network were investigated by XRR (X-Rays Reflectivity) and nitrogen adsorption isotherm on respectively mesoporous organized thin films (SBA) and disordered bulk mesoporous materials (Vycor glass). The article attempts to answer the question of the existence of a relationship between the rigidity of the mesoporous silica network, and the behavior of silica materials under irradiation. INTRODUCTION Two main solutions are usually proposed for conditioning nuclear wastes. The first one, used for low and intermediate level activity wastes, consists in embedding the contaminated particles or species in a matrix (hull compaction process, cementation process, bitumen process…). In the second concept used for the immobilization of high level waste (HLW) arising from the reprocessing of the spent fuel, radionuclides are incorporated in the network of mineral matrices such as ceramics or glasses. Thanks to their random network, borosilicate glasses are able to accommodate a wide range of extremely complex waste stream compositions (containing up to 30 different elements). This matrix is obtained by a melting process at a relatively high temperature (close to 1200°C). This high temperature process can be problematic in case of volatile species such as iodine or caesium. It is thus of interest to develop a new, low temperature process, to incorporate mobile species into inorganic matrices. Over the past two decades, the development of mesoporous materials provided a number of new possibilities for encapsulating nuclear wastes [1-2]. Mesoporous silicates are typically synthesized under mild or hydrothermal conditions using a structure-directing agent or template that can be removed subsequently, leaving a material with void spaces. These soft synthetic routes are a first determining advantage of mesoporous solids as conditioning matrices for volatile species (ie, I and Cs). A second advantage is that their porosity can be closed under relatively soft conditions like mild thermal treatment, or suited chemical stresses, in order to ensure a durable confinement. This ability of mesoporous structure to collapse under given stresses is thus of great advantage regarding the foreseen applications, but it also raises the question of the behaviour of such materi
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