Geochemical investigations related to the Yucca Mountain environment and potential nuclear waste repository
- Southwest Research Institute, San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses
This report presents final results of the Geochemistry Research Project conducted at the Center for Nuclear Waste Regulatory Analyses (CNWRA) for the Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research. The study focused on experimental determinations and theoretical interpretations of fundamental thermodynamic and kinetic properties of minerals and reactions that characterize geochemical processes at the proposed nuclear waste repository site at Yucca Mountain and that could affect the capacity of the site to isolate nuclear waste. Technical results are presented in three major sections covering (i) cation exchange studies on clinoptilolite, (ii) kinetic and solubility studies on analcime and Na-clinoptilolite, and (iii) conceptual and numerical geochemical modeling of natural and repository systems. Experimental studies were designed to advance knowledge of the fundamental properties of the zeolite minerals clinoptilolite and analcime through controlled tests at 25{degrees}C, and to interpret the data in the context of the geochemical system at Yucca Mountain. Cation exchange equilibria were determined for clinoptilotite and binary solutions of Na{sup +} with K{sup +}, Ca{sup 2+}, and Sr{sup 2+} at several solution concentrations. Results were interpreted using a Margules solid solution model for clinoptilolite coupled with a Pitzer activity coefficient model for aqueous solutions. Experimental data for analcime and clinoptilolite dissolution rates were interpreted using postulated rate mechanisms, and corresponding rate constants were determined. Dissolution rate data for analcime can be rationalized by alternate mechanisms which invoke either the presence of ultrareactive material or rate dependence on aqueous aluminum. Reversed solubility determinations were interpreted to obtain equilibrium constants for dissolution reactions and standard state Gibbs free energies of formation of the minerals.
- Research Organization:
- Nuclear Regulatory Commission, Washington, DC (United States). Div. of Regulatory Applications; Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses
- Sponsoring Organization:
- Nuclear Regulatory Commission, Washington, DC (United States)
- OSTI ID:
- 60781
- Report Number(s):
- NUREG/CR--6288; ON: TI95004715
- Country of Publication:
- United States
- Language:
- English
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