Physicochemical relationships during a KCl-bentonite hydrothermal reaction

Clay Minerals ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 475-482 ◽  
Author(s):  
J. Linares ◽  
F. Huertas ◽  
E. Caballero ◽  
C. Jimenez de Cisneros
Keyword(s):  
Radioactive Waste ◽  
Performance Assessment ◽  
Waste Disposal ◽  
Adsorption Process ◽  
Hydrothermal Reaction ◽  
Radioactive Waste Disposal ◽  
Solution Temperature ◽  
Different Temperatures ◽  
Radioactive Waste Repositories ◽  
Waste Repositories

AbstractA dioctahedral bentonite was treated hydrothermally with KCI solutions (0.025-1 M) at different temperatures (60-200°C) and times (1-360 days) to evaluate its use as a barrier for radioactive waste disposal. Equations relating adsorbed K on smectite with initial and equilibrium K concentrations in solution, temperature and time have been obtained. These equations are useful for modelling the influence and behaviour of these variables and contribute to the performance assessment calculations for radioactive waste repositories. Likewise, the thermodynamic parameters of the K adsorption process have been calculated. Other relationships, including silica in solution and pH, are also shown.

Intercomparison of Models of 14C in the Biosphere for Solid Radioactive Waste Disposal

Radiocarbon ◽  
2013 ◽  
Vol 55 (2) ◽  
pp. 814-825 ◽  
Author(s):  
Shelly Mobbs ◽  
George Shaw ◽  
Simon Norris ◽  
Laura Marang ◽  
Trevor Sumerling ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Nuclear Power ◽  
Radioactive Waste Disposal ◽  
Natural Processes ◽  
Radioactive Waste Repositories ◽  
Release Area ◽  
Key Drivers ◽  
Reactor Operating ◽  
Waste Repositories

Radiocarbon is present in solid radioactive wastes arising from the nuclear power industry, in reactor operating wastes, and in graphite and activated metals that will arise from reactor decommissioning. Its half-life of 5730 yr, among other factors, means that 14C may be released to the biosphere from radioactive waste repositories. These releases may occur as 14C-bearing gases, especially methane, or as aqueous species, and enter the biosphere from below via natural processes or via groundwater pumped from wells. Assessment of radiation doses to humans due to such releases must take account of the major role of carbon in biological processes, requiring specific 14C assessment models to be developed. Therefore, an intercomparison of 5 14C assessment models was organized by the international collaborative forum, BIOPROTA. The intercomparison identified significantly different results for the activity concentrations in the soil, atmosphere, and plant compartments, based upon the different modeling approaches. The major source of uncertainty was related to the identification of conditions under which mixing occurs and isotopic equilibrium is established. Furthermore, while the assumed release area plays a role in determining the calculated atmospheric 14C concentrations, the openness of the plant canopy and the wind profile in and above the canopy are the key drivers. The intercomparison has aided understanding of the processes involved and helped to identify areas where further research is required to address some of the uncertainties.

The structure and composition of solid complexes comprising of Nd(III), Ca(II) and D-gluconate isolated from solutions relevant to radioactive waste disposal

2020 ◽  
Vol 92 (10) ◽  
pp. 1709-1715 ◽  
Author(s):  
Éva Böszörményi ◽  
Jorge Lado ◽  
Csilla Dudás ◽  
Bence Kutus ◽  
Márton Szabados ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Radioactive Waste ◽  
Complex Compounds ◽  
Radioactive Waste Disposal ◽  
Complexing Agents ◽  
Suitable Model ◽  
Ionic Radii ◽  
Radioactive Waste Repositories ◽  
Waste Repositories ◽  
Solid Complexes

AbstractCertain complexing agents (such as D-gluconate, D-isosaccharinate, etc.) as well as actinides and lanthanides are simultaneously present in cementitious radioactive waste repositories and (in the presence of water) are capable of forming complex compounds. Such processes may immobilize radionuclides and are of importance in the thermodynamic modelling of the aqueous chemistry of waste repositories. Nd(III) is considered to be a suitable model for trivalent lanthanides and actinides, due to the similarity of their ionic radii. In the current work, solid complexes isolated from aqueous solution containing Nd(III), Ca(II) and D-gluconate (Gluc−) were investigated. In an aqueous solution containing Nd(III) and Gluc−, the formation of a precipitate was observed at pH ≥ 8. This precipitate was found to redissolve around pH ~ 11, but reprecipitated when Ca(II) ions were added to the solution. In order to gain an insight in binary and ternary aqueous systems, in the present work we report the structure of these solid complexes obtained from XRD, FT-IR, Raman, SEM-EDAX and UV-DRS measurements. The structure of these solids, where possible, was compared with those identified in solution. The compositions of these complexes are suggested to be NdGlucH−1(OH) · 2H2O and CaNdGlucH−1(OH)3 · 2H2O, respectively. In these, the chemical environment of the Nd(III) was found to be the same as that in the NdGlucH−1(OH)0(aq) solution species.

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