Thermodynamic Stabilities of U(VI) Minerals: Estimated and
                        Observed Relationships

Finch, Robert J.

doi:10.1557/proc-465-1185

Cited by 27 publications

(35 citation statements)

References 21 publications

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“…These values given by Chen et al (1999 [DIRS 123270]) are in strong agreement with that estimated using the log K value of Moll et al (1996 [DIRS 106349]). This value is also in good agreement with that reported by Finch (1997) [DIRS 106347]) and Nguyen et al (1992 [DIRS 100809 , and also other solubility studies, the results of which will be used as corroborative data. There have been several solubility studies conducted for uranophane.…”

Section: Soddyite ((Uo 2 ) 2 Sio 4 ·2h 2 O)supporting

confidence: 91%

Qualification of Thermodynamic Data for Geochemical Modeling of Mineral-Water Interactions in Dilute Systems

Wolery¹,

Jové-Colón²

2004

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Section: Soddyite ((Uo 2 ) 2 Sio 4 ·2h 2 O)supporting

confidence: 91%

Qualification of Thermodynamic Data for Geochemical Modeling of Mineral-Water Interactions in Dilute Systems

Wolery¹,

Jové-Colón²

2004

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“…Thermodynamic databases from numerous literature sources were used to update the computer codes (Alwan and Williams 1980, Chen et al 1999, Finch 1997, Grenthe et al 1992, Kalmykov and Choppin 2000, Langmuir 1978, O'Hare et al 1976, Sergeyeva et al 1972, and Vochten and Haverbeke 1990. It is important to note that because of the complex chemistry of U, there is significant debate within the literature regarding the stoichiometry and the thermodynamic values assigned to aqueous U species and secondary mineral phases.…”

Section: Modelingmentioning

confidence: 99%

Effect of Concrete Waste Form Properties on Radionuclide Migration

Mattigod¹,

Bovaird²,

Wellman³

et al. 2009

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SummaryAssessing long-term performance of Category 3 waste cement grouts for radionuclide encasement requires knowledge of the radionuclide-cement interactions and mechanisms of retention (i.e., sorption or precipitation); the mechanism of contaminant release; the significance of contaminant release pathways; how waste form performance is affected by the full range of environmental conditions within the disposal facility; the process of waste form aging under conditions that are representative of processes occurring in response to changing environmental conditions within the disposal facility; the effect of waste form aging on chemical, physical, and radiological properties; and the associated impact on contaminant release. This knowledge will enable accurate prediction of radionuclide fate when the waste forms come in contact with groundwater. Numerous sets of tests were initiated in fiscal years (FY) 2006 through2009 to evaluate 1) diffusion of iodine (I) and technetium (Tc) from concrete into uncontaminated soil after 1 and 2 years, 2) I and rhenium (Re) diffusion from contaminated soil into fractured concrete, 3) I and Re (set 1) and Tc (set 2) diffusion from fractured concrete into uncontaminated soil, 4) the moisture distribution profile within the sediment half-cell, 5) the reactivity and speciation of uranium (VI) [U(VI)] compounds in concrete porewaters, 6) the rate of dissolution of concrete monoliths, and 7) the diffusion of simulated tank waste into concrete.In FY 2008, concrete-soil half-cells initiated during FY 2007 using fractured concrete prepared with and without metallic iron, half of which were carbonated, were sectioned to evaluate the diffusion of I and Re in the concrete part of the half-cell. Probit plots were constructed from this data set.A second set of diffusion experiments, which had been initiated during FY 2007 using concrete-soil half-cells containing Tc, was sectioned in FY 2008 to measure the diffusion profile in the soil half-cell. These half-cells were prepared with and without metallic iron (Fe) and set up under unsaturated conditions (4%, 7%, and 15% moisture content by weight). Probit plots were constructed from this data set. In FY 2008, a set of concrete-soil half-cells were initiated. The half-cells were sectioned in FY 2009 to measure the diffusion profile in the concrete half-cell. Concentration and probit analysis was performed on the half-cells.A study was initiated during FY 2004 to better understand the reactivity of limited solubility U(VI)-bearing compounds in Portland cement grout specimens. The U(VI) nitrate-spiked specimens were aged for various time spans ranging from 2 weeks to 1 year. The uranium phases in these specimens were identified to be soddyite, becquerelite, uranophane, and autunite. Reliable thermochemical data are not available for these phases under conditions present in concrete waste forms. Therefore, to gather such data, synthetic routes were developed for the precipitation of pure uranium phases. From FY 2007 to FY 2008, the solubility meas...

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“…Table 2 lists U(VI) species that can form under these Eh and pH conditions in the aerobic YM repository with calcium-silica saturation. For these major U(VI) species that have been observed, Table 2 also shows their Gibbs energies of formation, G º f,298 (Freeze, Cherry 1979;Bruton, Shaw 1988;Finch 1997;Chen et al 1999). Figure 10 shows that under aerobic condition in the YM repository U(VI) species are expected to form.…”

Section: Silicates Suppress the Formation Of Calcium Hydroxidementioning

confidence: 99%

“…10 represent quartz (lower) and amorphous silica (upper) equilibria. The mineral stability fields defined by the light dashed lines are based on the Gibbs energies for the minerals given by Finch (1997 2 ) vs. log[H4SiO4] diagram for the SiO2-CaO-UO3-H2O system, the predicted stability fields for these phases replace most of the field for uranophane (Chen et al 1999).…”

Section: Silicates Suppress the Formation Of Calcium Hydroxidementioning

confidence: 99%

“…Because the uranyl oxide hydrates, (UO 2 ) x (OH) y , are the first corrosion products to form on UO 2 (Fig 7), their paragenesis is the principal reaction path for uraninite corrosion (Finch 1997). Kinetics favor the early formation of (UO 2 ) x (OH) y , such as schoepite (Table 2), which can apparently form from solutions with low silica.…”

Section: Silicates Suppress the Formation Of Calcium Hydroxidementioning

confidence: 99%

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Cost-Effective Cementitious Material Compatible with Yucca Mountain Repository Geochemistry

Dole¹

2004

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Thermodynamic Stabilities of U(VI) Minerals: Estimated and Observed Relationships

Cited by 27 publications

References 21 publications

Qualification of Thermodynamic Data for Geochemical Modeling of Mineral-Water Interactions in Dilute Systems

Qualification of Thermodynamic Data for Geochemical Modeling of Mineral-Water Interactions in Dilute Systems

Effect of Concrete Waste Form Properties on Radionuclide Migration

Cost-Effective Cementitious Material Compatible with Yucca Mountain Repository Geochemistry

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