Qualification of Thermodynamic Data for Geochemical Modeling of Mineral–Water Interactions in Dilute Systems
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| ANL-WIS-GS-000003 REV 01.pdf (3.08 MB) | 3.08 MB |
| ANL-WIS-GS-000003 REV 01 ERD 01.pdf (1.07 MB) | 1.07 MB |
This report is developed from Technical Work Plan for: Thermodynamic Databases for Chemical Modeling (BSC 2006 [DIRS 177885]). The purpose of this analysis report is to update the thermochemical database data0.ymp.R4 (Output DTN: SN0410T0510404.002). Various data have been added, corrected, or corroborated, partly in response to four Condition Reports (CRs): CR 6489, CR 6731, CR 7542, and CR 7756. The most notable changes are a general revision of phosphate data to achieve consistency with the recommendations from the Committee on Data for Science and Technology (CODATA) (Cox. et al. 1989 [DIRS 150874]) for key thermodynamic data for the aqueous species HPO42− and H2PO4− (this action is in response to part of CR 6731) and additions and corrections for uranium minerals observed in UO2 drip tests and natural analogues (CR 7756). The resulting principal product is the thermochemical database data0.ymp.R5 (Output DTN: SN0612T0502404.014).
The thermochemical databases in the data0.ymp.R* series are used with the computer software package EQ3/6 (e.g., EQ3/6 V8.0; see Section 3.1.1). These databases are used in predictive models for waste form and waste package corrosion, modeling of in-package and in-drift chemical conditions, and for prediction of dissolved radionuclide concentrations. They are also used to support criticality assessments and modeling of reactive transport of radionuclides in groundwater. The members of this database series support chemical modeling of solid–fluid interactions in systems with dilute aqueous solutions (ionic strengths of up to one molal) at temperatures of 0°C to 300°C along the liquid-vapor saturation curve of pure water. The limitation to dilute systems is tied to the support for model equations for thermodynamic activity coefficients of aqueous species. The databases in this series are suitable for use with either of two activity coefficient models, the B-dot equation (Helgeson 1969 [DIRS 137246]) and the Davies equation (Wolery 1992 [DIRS 100836], pp. 38 and 39). The B-dot equation requires a database of hard core diameters or “ion sizes” for aqueous species (see Section 6.5). The Davies equation requires no special data, only the electrical charge numbers of the aqueous ions. Both models are known to become inaccurate at high ionic strength.
