所属领域：
钍基熔盐堆核能系统
资源类型：
工业技术
/ 能源与动力工程
文献作者：
MUNGALL, JE; MARTIN, RF
文献发表年份：
1994
文献期刊：
GEOCHIMICA ET COSMOCHIMICA ACTA
文献摘要：Pumice produced during the subplinian phase of eruption of a peralkaline trachyte lava on the island of Terceira, Azores, has undergone extensive leaching at ambient conditions by groundwater, while remaining in a glassy state. Over 25% of F, Na, K, Si, Fe, Ti, and Mn originally present has been removed, whereas U, Al, Nb, Ca, Y, and Rb show smaller but significant losses. Thorium, Zr, Hf, Ta, and Lu have remained immobile. Water content (measured as LOI) has increased up to tenfold, whereas the Sr content has risen by up to 80%. The absence of devitrification requires that leached elements escaped by diffusing through the glass; a coefficient of chemical diffusion D(Na) between 1.8 X 10(-19) cm2 s-1 and 6.1 X 10(-19) cm2 s-1 has been calculated, in excellent agreement with previously published experimentally derived values for comparably low temperatures. Water has not replaced the leached cations on a charge-equivalent basis, a finding that requires an explanation other than simple binary interdiffusion. We suggest that a simultaneous influx of molecular water and cation exchange between Na+ in the glass and H+ in the groundwater opens the glass structure and frees cations, which can diffuse outward by hydrolysis of bridging oxygen atoms. Reported mobilities have important implications for such diverse fields as igneous petrology, nuclear waste management, and agriculture.
文献类型： Article
文献语种： English