Thermodynamics of Trivalent Actinides in Concentrated Electrolyte Solutions: Modelling the Chloride Complexation of Cm(III)

Könnecke, Th.; Fanghänel, Th.; Kim, J. I.

doi:10.1524/ract.1997.76.3.131

Cited by 18 publications

(8 citation statements)

References 11 publications

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“…4 agree fairly well with the values previously determined by Kim et al [18] and Decambox et al [16]. The further increase of the lifetime when carbonate concentration is increased above 0.1 molal, which is also observed in previous studies, could not be explained by a speciation model with Cm(C0 3 Applying Eq. (2), the relative fluorescence intensity factors are calculated to be 1.1 ± 0.1 for Cm(C0 3 ) 2 " 1.6 ± 0.2 for Cm(C0 3 )l" 3.9 ± 0.3 for Cm(C0 3 )r In Fig.…”

Section: Life Times and Hydration Numbers (Upper Part) And The Calcsupporting

confidence: 92%

“…Time resolved laser fluorescence spectroscopy (TRLFS) enables the speciation of Cm(III) to be measured in the nanomolar concentration range. Previous studies have been performed on hydrolysis [1], chloride complexation [2,3], and sulfate complexation [4] of Cm(III) in concentrated brines. The main objective of this contribution is to establish the speciation of Cm(HI) in carbonate solutions at constant ionic strength and to study the spectroscopic properties of the various carbonate complexes.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamics of Cm(III) in Concentrated Electrolyte Solutions. Carbonate Complexation at Constant Ionic Strength (1 m NaCl)

et al. 1998

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Curium / Actinides / Carbonate complexation / Fluorescence spectroscopy SummaryThe carbonate complexation of Cm(III) is investigated by means of time resolved laser fluorescence spectroscopy (TRLFS) at 25°C in 1 m NaCl as a function of the carbonate concentration. In the first set of experiments, the carbonate concentration is controlled by the C0 2 equilibrium partial pressure, (pC0 2 = 10-1000 mbar) and pH whereas the second set of batch experiments is performed at higher carbonate concentrations ([CO §~] > 10 4 molal). Both data sets overlap in the intermediate range and fit well together. The carbonate complexes CmCOJ, Cm(C0 3 ) 2 and Cm(C0 3 ) 3~ are quantified spectroscopically in the trace concentration range by peak deconvolution of fluorescence emission spectra. At pC0 2 = 500 or 1000 mbar and pH < 6.5, there is evidence for the formation of a Cm(III) bicarbonate complex to a small extent. Up to pH 9.5 there is no indication for the formation of mixed hydroxo carbonate complexes. At high carbonate concentrations (> 0.1 molal), the formation of an additional complex, Cm(C0 3 )4~, is indicated. The stability constants determined in 1 molal NaCl solution are found to be: logy?(CmHCO! + ) = 1.9; logy?(CmC0 3 + ) = 5.90; log0(Cm(CO 3 ) 2 ) = 10.27; log^(Cm(C0 3 )D = 13.18; log/? (Cm(C0 3 )D = 14.18.

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Section: Life Times and Hydration Numbers (Upper Part) And The Calcsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Thermodynamics of Cm(III) in Concentrated Electrolyte Solutions. Carbonate Complexation at Constant Ionic Strength (1 m NaCl)

et al. 1998

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“…Cm(III) has been chosen as a representative for trivalent actinides, because of its high fluorescence spectroscopic sensitivity. Previous studies have been performed on hydrolysis [1], chloride complexation [2,3], sulfate complexation [4], and carbonate/bicarbonate complexation [5,6] of Cm(III) in concentrated chloride brines. Recently an overview about the spectroscopic evaluation of thermodynamics of trivalent actinides in brines is published [7,8].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of Cm(III) in Concentrated Electrolyte Solutions. Fluoride Complexation in 0-5 m NaCl at 25°C

et al. 1999

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Trivalent actinides / Curium / Fluoride complexation / Pitzer model SummaryThe fluoride complexation of Cm(III) is investigated by means of time-resolved laser fluorescence spectroscopy (TRLFS) at 25°C. In the first set of experiments, the speciation of Cm(III) is investigated in 1 m NaCl as function of the fluoride concentration (m F < 8 · 10 1 m). The monofluoride complex CmF 2+ is identified and its formation constant is determined to be log^(CmF 2+ ) = 2.46 ± 0.05. At the highest fluoride concentration there is evidence for the formation of a Cm(III) difluoride complex to a small extent. However, as the fluoride concentration interval is limited by the precipitation of CmF,(s), the stability constant of CmP + can not be quantified. In the second set of experiments the formation of CmF 2+ is studied in 0-5 m NaCl. The ionic strength dependence of the formation constant is described by modeling the activity coefficients with the ion interaction approach (Pitzer equations). The formation constant at / = 0 is calculated to be log^°(CmP + ) = 3.44 ± 0.05.

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“…In order to evaluate the aqueous speciation as well as the saturation state with respect to REE containing secondary phases we treated all REE as one component, with the well known hydrolysis constants for Eu (log β 0 1 = 6.2 [9] and log β 0 2 = 12.7 [10]), as well as the solubility products for Eu(OH) 3 (am) K sp = 10 −24.4 and for Eu(OH) 3 (cr) K sp = 10 −26.5 [11]. However, in order to account for the high salinity we used Pitzer parameters for Cm [12]. The solubility product of Nd 0.5 Na 0.5 MoO 4 (K sp = 10 −8.92 [13]) was used as a reference for REE containing secondary molybdate solid solutions with powellitelike structure.…”

Section: Methodsmentioning

confidence: 99%

Formation of secondary phases after long-term corrosion of simulated HLW glass in brine solutions at 190 °C

Zimmer¹,

Bohnert²,

Bosbach³

et al. 2002

Radiochimica Acta

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The behavior of rare earth elements (REE) as chemical analogues for actinides during glass corrosion was studied with static long-term batch experiments (7.5 years) at 190 • C. Corrosion tests were carried out using a simulated inactive high level waste (HLW) glass powder. Two different highly concentrated salt solutions (NaCl-rich and MgCl 2 -rich) have been used to simulate the potential corrosion by aqueous solutions in geological salt formations. Samples with surface-to-volume ratios (S/V) of 1000 m −1 and 10 000 m −1 were investigated. The chemical composition of the aqueous solution and the formation of secondary phases at the glass/solution interface as well as their elemental composition, especially with respect to the behavior of REE was studied. The glass corrosion behavior and secondary phase formation was significantly different in the two brines. In the MgCl 2 -rich salt solution, with a final pH < 3.5, hydrous Mg-silicates and (Ba,Sr)SO 4 solid solutions with considerable amounts of Sr (up to 15 wt. %) have been observed. Further, REE-sulfates and REE-molybdates with an indication of dissolution (etch pits) as secondary phases could be identified. In the NaCl-rich solution with a final high pH, REE-containing hydrous silicates (up to 35 wt. %) and (Ba,Sr)SO 4 solid solutions with small amounts of Ce (up to 5 wt. %) have been observed. Frequently observed Ca-molybdates (powellite) did not contain detectable amounts of REE.

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Thermodynamics of Trivalent Actinides in Concentrated Electrolyte Solutions: Modelling the Chloride Complexation of Cm(III)

Cited by 18 publications

References 11 publications

Thermodynamics of Cm(III) in Concentrated Electrolyte Solutions. Carbonate Complexation at Constant Ionic Strength (1 m NaCl)

Thermodynamics of Cm(III) in Concentrated Electrolyte Solutions. Carbonate Complexation at Constant Ionic Strength (1 m NaCl)

Thermodynamics of Cm(III) in Concentrated Electrolyte Solutions. Fluoride Complexation in 0-5 m NaCl at 25°C

Formation of secondary phases after long-term corrosion of simulated HLW glass in brine solutions at 190 °C

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