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We have compared the transport behavior in various environments of radionuclides originating from underground nuclear tests at the Nevada Test Site (NTS). Under saturated conditions in both alluvium and fractured volcanic rock, 36 C1, 129 I, and 3 H exhibit mutually consistent and presumably conservative behavior during saturated flow. At the saturated fractured rock site, "Tc was conservative under most conditions, but was not present in samples containing high levels of iron oxyhydroxides formed in the well water. 125 Sband 137 Cs transport was observed in fracture flow, but concentrations of Sb were somewhat attenuated and Cs was strongly retarded. Total activity levels of these nonconservative nuclides were not affected by the particulate phenomena that reduced "Tc levels. Studies of transport in unsaturated alluvium showed that neither 36 C1 nor 129 I were conservative relative to tritium. Observations of the relative transport behavior of the radionuclides as functions of both time and distance permit deductions about the nature of their source terms.

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The phenomena involved in portland cement hydration and interactions with nanosilica are very complex and not yet fully understood. In addition, few papers have currently proposed to investigate the microstructure and mechanical properties of ternary mixtures using portland cement, colloidal nanosilica, and highly reactive mineral additions. This article investigates, for the first time, the behavior of different highly reactive mineral additions (silica fume and metakaolin) when partially replaced by colloidal nanosilica in the microstructure and hydration of cementitious materials. For the study of the cementitious material microstructures, a Langavant calorimeter, compressive strength, Xray diffraction, thermogravimetry, infrared spectroscopy, and mercury intrusion porosimetry were used. The pastes with a 1% substitution of highly reactive mineral additions by nanosilica showed higher compressive strength and more refined porosity than the pastes with only silica fume or metakaolin. The results show that nanosilica appears to have better synergism with metakaolin than with silica fume.

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