Results 1 - 10 of 13468
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[en] A satisfactory method was established for synthesizing four samples of tin (IV) antimonates. The stability of the prepared materials increases with decreasing the Sb/Sn molar ratios, its ion exchange capacity was found in the order of Sn Sb-IV > SnSb-III > SnSb-II > SnSb-I, where the material having the greater antimony content had greater uptake of ions due to the increased acidities of the species by increasing the antimony. Straight lines are obtained for the plots of distribution coefficients (kd) against HNO3 concentrations for 134Cs, 85Sr, 60Co and 152+154Eu.
[en] We summarize recent advances in modeling of solidification microstructures using computational methods that bridge atomistic to continuum scales. We first discuss progress in atomistic modeling of equilibrium and non-equilibrium solid-liquid interface properties influencing microstructure formation, as well as interface coalescence phenomena influencing the late stages of solidification. The latter is relevant in the context of hot tearing reviewed in the article by M. Rappaz in this issue. We then discuss progress to model microstructures on a continuum scale using phase-field methods. We focus on selected examples in which modeling of 3D cellular and dendritic microstructures has been directly linked to experimental observations. Finally, we discuss a recently introduced coarse-grained dendritic needle network approach to simulate the formation of well-developed dendritic microstructures. The approach reliably bridges the well-separated scales traditionally simulated by phase-field and grain structure models, hence opening new avenues for quantitative modeling of complex intra- and inter-grain dynamical interactions on a grain scale
[en] Fixing radioactive waste is disclosed in which the waste is collected as a slurry in aqueous media in a metering tank located within the nuclear facilities. Collection of waste is continued from time to time until a sufficient quantity of material to make up a full shipment to a burial ground has been collected. The slurry is then cast in shipping containers for shipment to a burial ground or the like by metering through a mixer into which fixing materials are simultaneously metered at a rate to yield the desired proportions of materials. (U.S.)
[en] The bituminization process is the choice at three reprocessing centers in Europe, where they are actually solidifying medium and low level wastes. When the reprocessing centers in the U.S. face the problem of waste disposal, a proven system is available. However, the bitumen binder is not recommended for high level wastes, although a process using the extruder-evaporator is readily adaptable. In the interim the commercial power plants in both Europe and the U.S. are using the VRS based on cost benefit and proven technology
[en] Heterogeneous nucleation is an important phenomenon in solidification processes. A smooth interface between the nucleus and its substrate is assumed for considerations on heterogeneous nucleation in classical nucleation theory, but this condition cannot always be satisfied for the factual heterogeneous nucleation process. The formation of a nucleus on a coarse substrate is investigated, and the effect of the roughness factor of the substrate on the nucleation barrier is discussed based on Wenzel's wetting model. It is shown that the heterogeneous nucleation barrier is generally less than that of the homogeneous nucleation barrier, and a lower intrinsic wetting angle between the nucleus and the substrate leads to easier nucleation. However, it is also found that, when the intrinsic wetting angle is less than 90°, higher roughness leads to easier heterogeneous nucleation; for a certain roughness factor, an intrinsic critical wetting angle exists which decreases the heterogeneous nucleation barrier to 0. On the other hand, when the intrinsic wetting angle is larger than 90°, higher roughness leads to a larger heterogeneous nucleation barrier; for a certain roughness factor, an intrinsic critical non-wetting angle exists which increases the heterogeneous nucleation barrier to the value of the homogeneous nucleation. It thus leads to the ineffectiveness of the foreign substrate for nucleation.