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Structure, stabilité thermique et résistance sous irradiation externe de verres aluminoborosilicatés riches en terres rares et en molybdène

Abstract : In France, the highly radioactive nuclear liquid wastes arising from spent nuclear fuel reprocessing (fission products + minor actinides (FPA)) are currently immobilized in an aluminoborosilicate glass called "R7T7". In the future, the opportunity of using new aluminoborosilicate glass compositions (HTC glasses) is considered in order to increase the waste loading in glasses and thus significantly decrease the number of glass canisters. However, the increase of the concentration of FPA could lead to the crystallization of rare-earth-rich phases (Ca2RE8(SiO4)6O2) or molybdenum-rich phases (CaMoO4, Na2MoO4) during melt cooling, which can modify the confinement properties of the glass (chemical durability, self-irradiation resistance...), particularly if they can incorporate radionuclides α or β in their structure. This thesis can be divided into two parts: The first part deals with studying the relationship that can occur between the composition, the structure and the crystallization tendency of simplified seven oxides glasses, belonging to the SiO2-B2O3-Al2O3-Na2O-CaO-MoO3-Nd2O3 system and derived from the composition of the HTC glass at 22,5 wt. % in FPA. The impact of the presence of platinoid elements (RuO2 in our case) on the crystallization of the different phases is also studied. The second part deals with the effect of actinides α decays and more particularly of nuclear interactions essentially coming from recoil nuclei (simulated here by heavy ions external irradiations) on the behaviour under irradiation of an aluminoborosilicate glass containing apatite Ca2Nd8(SiO4)6O2 crystals, that can incorporate actinides in their structure. Two samples containing apatite crystals with different size are studied, in order to understand the impact of microstructure on the irradiation resistance of this kind of material.
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Submitted on : Wednesday, November 23, 2011 - 6:00:16 PM
Last modification on : Wednesday, October 14, 2020 - 4:06:46 AM
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Nolwenn Chouard. Structure, stabilité thermique et résistance sous irradiation externe de verres aluminoborosilicatés riches en terres rares et en molybdène. Matériaux. Université Pierre et Marie Curie - Paris VI, 2011. Français. ⟨pastel-00644194⟩

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