Browsing by Author "Advocat, T"

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    Alteration of cold crucible melter titanate-based ceramics: comparison with hot-pressed titanate-based ceramic
    (Materials Research Society, 1997) Advocat, T; Leturcq, G; Lacombe, J; Berger, G; Day, RA; Hart, KP; Vernaz, E; Bonnetier, A
    Synroc ceramics were synthesized in an induction-heated cold crucible at laboratory scale (1 kg) from an oxide mixture, and at industrial prototype scale (45 kg) from Synroc previously produced by sintering under load at high temperature. After melting, both materials contained the major phases of Synroc-C. The chemical durability of both melted materials, as determined by static leaching of powder samples in initially pure water at 90°C with an SA/V ratio of 20000m−1, was equivalent to that of conventional hot-pressed Synroc-C. Cerium, used in this investigation to simulate the presence of tri-and tetravalent actinides, was found in steady-state concentrations on the order of 1 ppb (i.e. NL(Ce) ≤ 10−6 g·m−2). The concentration in the leachates was independent of the initial CeO2 content of the Synroc (at least up to 10 wt%); moreover, it is similar to the results obtained with hot-pressed Synroc-C specifically formulated for conditioning long-lived actinides. © Materials Research Society 1997
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    Physical stability and durability of heavy-ion irradiated crystalline zirconolite CaZrTh2O7 ceramic designed for minor actinide disposition
    (Commissariat à l'énergie atomique (CEA), 2004-07-01) Advocat, T; McGlinn, PJ; Smith, KL; Gosset, D; Rabiller, H; Zhang, ZM; Lumpkin, GR; Chaumont, J
    External irradiation studies with heavy ions Pb3+ accelerated at 510 keV were conducted on non radioactive zirconolite ceramic pellets, containing actinide surrogates such as Rare Earth Elements (REE). Ion irradiation of ceramic pellet surfaces has transformed the outermost several tenths of nanometers of the surface into a metamict state. The chemical durability in water of the irradiated zirconolite ceramics was measured at 100 deg C. The dissolution behavior is similar to that for the fully crystalline materials, and natural zirconolite minerals as well, which are at least several hundred million years old and self-irradiated up to 10 20}alpha decay/g due to the presence of appreciable quantities of Th and U. The amorphization process of the crystalline structure by the alpha decay does not modify the high chemical durability of zirconolite.