Contribution à l'étude de la stabilité des minéraux constitutifs de l'argilité du Callovo-Oxfordien en présence de fer à 90° C

Abstract : In the context of underground disposal of high-level radioactive waste, interactions between metallic iron and Callovo-Oxfordian rock (COx), its purified clay fraction (SCOx) or pure clay phases (kaolinite, illite, smectites) were investigated at 90°C under anoxic atmosphere in chlorine solution. Role of COx non clay minerals in these reactions was also studied. Rapid metallic iron oxidation conducts to iron cations release in solution, pH increase (8-10) and Eh decrease (reducive conditions). The partial dissolution of initial clay phases and the crystallization of Fe-serpentines (odinite or berthierine mainly) and of low amount of magnetite were observed. The introduction of O2 into the system leads to Fe-serpentines destabilisation. Iron exsolution conducts to iron oxides and hydroxides formation and clay particles with composition close to the initial ones precipitate. Addition of quartz into the system leads to the partial dissolution of this mineral and to the modification of reaction pathways. Precipitation of magnetite is reduiced and Fe-serpentines are silica enriched. In the case of kaolinite-metallic iron interaction, combinated used of XRD, MET, XPS and textural analyses evidences the growth of berthierine on the basal face of kaolinites, resulting in Fe-serpentine-kaolinite demixed particles. Through the used of spectroscopic analyses (Mössbauer, XAS and STXM), we were able to determine Fe2+/Fe3+ and AlIV/AlVI ratio in elementary particles, which allows proposing structural formulae for the Fe-serpentines
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Camille Rivard. Contribution à l'étude de la stabilité des minéraux constitutifs de l'argilité du Callovo-Oxfordien en présence de fer à 90° C. Sciences de la Terre. Institut National Polytechnique de Lorraine, 2011. Français. ⟨NNT : 2011INPL090N⟩. ⟨tel-01749547⟩

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