Application of the ruthenium and technetium thermodynamic data bases used in the EQ3/6 geochemical codes [electronic resource].
- Livermore, Calif : Lawrence Livermore National Laboratory, 1985.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Physical Description:
- 63 pages : digital, PDF file
- Additional Creators:
- Lawrence Livermore National Laboratory
United States. Department of Energy. Office of Scientific and Technical Information
- Based on a critical review of the available thermodynamic data, computerized data bases for technetium and ruthenium were created for use with the EQ3/6 geochemical computer codes. The technetium data base contains thermodynamic data for 8 aqueous species and 15 solids; 26 aqueous species and 9 solids were included in the ruthenium data base. The EQ3NR code was used to calculate solubility limits for ruthenium (8 x 10⁻¹⁶ M) in ground water from Yucca Mountain, a potential nuclear waste repository site near the Nevada Test Site (NTS). The code confirmed the essentially unlimited solubility of technetium in oxidizing conditions, such as those that are believed to exist in the unsaturated zone at Yucca Mountain and the Cambric Nuclear event site at the NTS. Ruthenium migration observed from the Cambric site was evaluated. The solubility limit for ruthenium (as the aqueous species RuO₄⁻) when constrained by RuO₂ is approximately equal to the concentration of ruthenium found in the cavity ground water (i.e., 2.1 x 10⁻¹¹ vs 4.5 x 10⁻¹¹ M). Differences in ruthenium solubility limits between Yucca Mountain and Cambric are primarily due to differences in ground-water pH. Technetium solubility (3 x 10⁻⁸ M) for moderately reducing conditions (Eh = -0.1 V) using the metastable oxide, TcO₂.2H₂O, as the solubility constraint is within the range of experimental values recently published in a study of technetium sorption on basalt. Previously published technetium solubilities of 10⁻¹² to 10⁻¹⁶ M were apparently based on a technetium data base that did not include aqueous species other than TcO₄⁻. When TcO(OH)₂° is included in the data base, the calculated values are much closer to the experimental results. Eh-pH diagrams were also generated for a variety of conditions using the SOLUPLOT code.
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