Geochemical controls on shale groundwaters: Results of reaction path modeling
The EQ3NR/EQ6 geochemical modeling code was used to simulate the reaction of several shale mineralogies with different groundwater compositions in order to elucidate changes that may occur in both the groundwater compositions, and rock mineralogies and compositions under conditions which may be encountered in a high-level radioactive waste repository. Shales with primarily illitic or smectitic compositions were the focus of this study. The reactions were run at the ambient temperatures of the groundwaters and to temperatures as high as 250/degree/C, the approximate temperature maximum expected in a repository. All modeling assumed that equilibrium was achieved and treated the rock and water assemblage as a closed system. Graphite was used as a proxy mineral for organic matter in the shales. The results show that the presence of even a very small amount of reducing mineral has a large influence on the redox state of the groundwaters, and that either pyrite or graphite provides essentially the same results, with slight differences in dissolved C, Fe and S concentrations. The thermodynamic data base is inadequate at the present time to fully evaluate the speciation of dissolved carbon, due to the paucity of thermodynamic data for organic compounds. In the illitic cases the groundwaters resulting from interaction at elevated temperatures are acid, while the smectitic cases remain alkaline, although the final equilibrium mineral assemblages are quite similar. 10 refs., 8 figs., 15 tabs.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 6428051
- Report Number(s):
- ORNL/TM-10944; ON: DE89007886
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
GEOCHEMISTRY
MATHEMATICAL MODELS
HIGH-LEVEL RADIOACTIVE WASTES
UNDERGROUND DISPOSAL
E CODES
GRAPHITE
GROUND WATER
ORGANIC COMPOUNDS
PH VALUE
RADIOACTIVE WASTE DISPOSAL
REDOX REACTIONS
SHALES
TEMPERATURE DEPENDENCE
CARBON
CHEMICAL REACTIONS
CHEMISTRY
COMPUTER CODES
ELEMENTAL MINERALS
ELEMENTS
HYDROGEN COMPOUNDS
MANAGEMENT
MATERIALS
MINERALS
NONMETALS
OXYGEN COMPOUNDS
RADIOACTIVE MATERIALS
RADIOACTIVE WASTES
ROCKS
SEDIMENTARY ROCKS
WASTE DISPOSAL
WASTE MANAGEMENT
WASTES
WATER
052002* - Nuclear Fuels- Waste Disposal & Storage
053000 - Nuclear Fuels- Environmental Aspects