Reaction of vitric Topopah Spring Tuff and J-13 ground water under hydrothermal conditions using Dickson-type, gold-bag rocking autoclaves
In support of the Nevada Nuclear Waste Storage Investigations Project, we conducted experiments to study the effects of repository-generated heat on glassy tuff present at Yucca Mountain, Nevada. Solid wafers of glassy tuff were reacted with a dilute ground water for several months at 250, 150, and 90{sup 0}C at 100 bar pressure in Dickson-type, gold-bag rocking autoclaves. The in-situ chemistry of the hydrothermal fluids was modeled; and the chemical affinities for all possible mineral precipitation reactions for species contained within the database were calculated using the EQ3/6 program. For the 250{sup 0}C experiment, the calculations predicted the precipitation of a zeolite mineral. Analyses of the run products showed that the wafer had been extensivley corroded, the glass shards were replaced by clinoptilolite (a zeolite), and pure clinoptilolite precipitated directly from solution. Modeling of the 150{sup 0}C experiment indicated that, although clay minerals were thermodynamically more highly supersaturated than zeolites in the first half of the experiment, by the end of the run a zeolite mineral was also predicted to precipitate. Analyses of the run products showed that no well-crystallized secondary minerals (clays or zeolites) had formed. In the 90{sup 0}C experiment, the degree of superstaturation for both clays and zeolites was lower than at either of the higher temperatures. The relative change in super-saturation for any one mineral was also lower as the run progressed. At the lower temperature (90 and 150{sup 0}C), slow precipitation kinetics may preclude the formation of the zeolite within the time span of these experiments. In general, the actual observations are in relatively good agreement with the geochemical model calculations made at each temperature.
- Research Organization:
- Lawrence Livermore National Lab., CA (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 60349
- Report Number(s):
- UCRL--53795; ON: DE88005234
- Country of Publication:
- United States
- Language:
- English
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Zeolitization of glassy Topopah Spring tuff under hydrothermal conditions
Hydrothermal interaction of solid wafers of topopah spring tuff with ground water and distilled water at 90/sup 0/C, 150/sup 0/C and 250/sup 0/C using dickson-type, gold-bag rocking autoclaves