Results of the colloid and radionuclide retention experiment (CRR) at the Grimsel Test Site (GTS), Switzerland – impact of reaction kinetics and speciation on radionuclide migration
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Horst Geckeis
Summary
The influence of smectite colloids on the migration behaviour of U(VI), Th(IV), Pu(IV), Am(III), Np(V), Sr(II) and Cs(I) is investigated within the Colloid and Radionuclide Retardation experiment (CRR). Two in situ experiments in a well-characterized granitic fracture zone are carried out in presence and absence of bentonite colloids. Radionuclide retardation observed in the field studies increases in the sequence Np(V)∼U(VI)<Sr(II)<Cs(I), where a small fraction of colloid borne breakthrough is only stated for Cs(I) in presence of bentonite colloids. Am(III) and Th/Pu(IV) mainly migrate as colloids without retardation in the presence and absence of smectitic colloids. The radionuclide migration behaviour is discussed on the basis of results obtained in laboratory batch sorption experiments and spectroscopic studies. Consistent with the field observation, laboratory derived Kd values increase in the order Np(V)∼U(VI)<Sr(II)<Cs(I). Significant kinetic hindrance for the sorption to fault gauge minerals is observed for Sr(II) and Cs(I), but notably for Am(III) and Pu(IV). The slow sorption reaction of tri- and tetravalent actinide ions is explained by their kinetically hindered dissociation from colloidal species. In order to explain the colloidal behaviour of tri- and tetravalent actinides even in absence of bentonite colloids, ultracentrifugation and spectroscopic experiments are performed. It is found that up to 60% of Pu(IV) and Am(III) species can be centrifuged off. Adding Cm(III) (5×10-8 mol L-1) into both injection solutions instead of Am(III) allows for a spectroscopic study by using the time resolved laser fluorescence spectroscopy (TRLFS). Peak position and fluorescence lifetimes (λ=604 nm, τ=110-114 μs) together with the fact that Cm(III) can be widely separated by ultracentrifugation, suggest the existence of inner-sphere surface complexes on groundwater and bentonite colloids. Carbon K-edge XANES analysis of the bentonite colloids reveal the presence of natural organic constituents. They are mainly of aliphatic nature containing high fractions of carboxylate groups. A contribution of these organic species towards the bentonite colloid stability and sorption of actinides is assumed to be likely.
© 2004 Oldenbourg Wissenschaftsverlag GmbH
Articles in the same Issue
- Preface: Migration Conference 2003
- Actinide chemistry: from weapons to remediation to stewardship
- Thermodynamics and solubility of (UxNp1-x)O2(am) solid solution in the carbonate system
- Solubility and colloid formation of Th(IV) in concentrated NaCl and MgCl2 solution
- Effect of reducing agents on the uranium concentration above uranium(IV) amorphous precipitate in Boom Clay pore water
- On Mo-Ru-Tc-Pd-Rh-Te alloy particles extracted from spent fuel and their leaching behavior under Ar and H2 atmospheres
- Modeling of the complex formation of metal ions with humic acids
- Application of the NICA-Donnan model for proton, copper and uranyl binding to humic acid
- Protonation and complexation of isosaccharinic acid with U(VI) and Fe(III) in acidic solutions: potentiometric and calorimetric studies
- Carbonate complexation of neptunium(IV) in highly basic solutions
- Fluorescence characteristics of complex formation of europium(III)-salicylate
- The reduction of U(VI) by near field hydrogen in the presence of UO2(s)
- Electrochemical aspects of radiolytically enhanced UO2 dissolution
- Effect of alpha radiolysis on doped UO2 dissolution under reducing conditions
- The redox behaviour of plutonium in humic rich groundwater
- The fate of radiolytic oxidants during spent fuel leaching in the presence of dissolved near field hydrogen
- Structural changes of uranyl moiety with reduction from U(VI) to U(V)
- Trivalent actinide coprecipitation with powellite (CaMoO4): Secondary solid solution formation during HLW borosilicate-glass dissolution
- Reproducibility of the uptake of U(VI) onto degraded cement pastes and calcium silicate hydrate phases
- Uranium adsorption on weathered schist – intercomparison of modelling approaches
- Contribution of minerals to the sorption of U(VI) on granite
- Distribution and geochemical association of actinides in a contaminated soil as a function of grain size
- Interactions between anionic complex species of actinides and negatively charged mineral surfaces
- Measurements and modelling of Pm sorption onto TiO2 and goethite
- Effect of humic acid on the sorption of Cm(III) onto γ-Al2O3 studied by the time-resolved laser fluorescence spectroscopy
- Am(III) and Eu(III) uptake on hematite in the presence of humic acid
- Luminescence properties of tetravalent uranium in aqueous solution
- Scanning transmission X-ray microscopy as a speciation tool for natural organic molecules
- Formation of hydroxyapatite in soils using calcium citrate and sodium phosphate for control of strontium migration
- Influence of humic substances on the 63Ni migration through crushed rock media
- U, Th, Eu and colloid mobility in a granite fracture under near-natural flow conditions
- Sorption behavior of europium(III) and curium(III) on the cell surfaces of microorganisms
- Interactions of trivalent and tetravalent heavy metal-siderophore complexes with Pseudomonas fluorescens
- In-situ diffusion of HTO, 22Na+, Cs+ and I- in Opalinus Clay at the Mont Terri underground rock laboratory
- Results of the colloid and radionuclide retention experiment (CRR) at the Grimsel Test Site (GTS), Switzerland – impact of reaction kinetics and speciation on radionuclide migration
- Fracture flow and radionuclide transport in block-scale laboratory experiments
- Comparison between in situ and laboratory diffusion studies of HTO and halides in Opalinus Clay from the Mont Terri
- Solubility constraints on uranium concentrations in groundwaters of the Tono uranium deposit, Japan
- Mobility of uranium in tertiary argillaceous sediments – a natural analogue study
- Redistribution of U, Pb and REE in association with alteration of uranium minerals from the Koongarra deposit, Northern Territory, Australia
- Towards a common thermodynamic database for speciation models
- Geochemically derived non-gaseous radionuclide source term for the Asse salt mine – assessment for the use of a Mg(OH)2-based backfill material
- Simulation of remediation alternatives for a 137Cs contaminated soil
- Simulating reactive transport in time dependent multiphase flow problems
- Reactive transport modelling of a spent fuel repository in a stiff clay formation considering excavation damaged zones
- Coupled transport/reaction modelling of copper canister corrosion aided by microbial processes
Articles in the same Issue
- Preface: Migration Conference 2003
- Actinide chemistry: from weapons to remediation to stewardship
- Thermodynamics and solubility of (UxNp1-x)O2(am) solid solution in the carbonate system
- Solubility and colloid formation of Th(IV) in concentrated NaCl and MgCl2 solution
- Effect of reducing agents on the uranium concentration above uranium(IV) amorphous precipitate in Boom Clay pore water
- On Mo-Ru-Tc-Pd-Rh-Te alloy particles extracted from spent fuel and their leaching behavior under Ar and H2 atmospheres
- Modeling of the complex formation of metal ions with humic acids
- Application of the NICA-Donnan model for proton, copper and uranyl binding to humic acid
- Protonation and complexation of isosaccharinic acid with U(VI) and Fe(III) in acidic solutions: potentiometric and calorimetric studies
- Carbonate complexation of neptunium(IV) in highly basic solutions
- Fluorescence characteristics of complex formation of europium(III)-salicylate
- The reduction of U(VI) by near field hydrogen in the presence of UO2(s)
- Electrochemical aspects of radiolytically enhanced UO2 dissolution
- Effect of alpha radiolysis on doped UO2 dissolution under reducing conditions
- The redox behaviour of plutonium in humic rich groundwater
- The fate of radiolytic oxidants during spent fuel leaching in the presence of dissolved near field hydrogen
- Structural changes of uranyl moiety with reduction from U(VI) to U(V)
- Trivalent actinide coprecipitation with powellite (CaMoO4): Secondary solid solution formation during HLW borosilicate-glass dissolution
- Reproducibility of the uptake of U(VI) onto degraded cement pastes and calcium silicate hydrate phases
- Uranium adsorption on weathered schist – intercomparison of modelling approaches
- Contribution of minerals to the sorption of U(VI) on granite
- Distribution and geochemical association of actinides in a contaminated soil as a function of grain size
- Interactions between anionic complex species of actinides and negatively charged mineral surfaces
- Measurements and modelling of Pm sorption onto TiO2 and goethite
- Effect of humic acid on the sorption of Cm(III) onto γ-Al2O3 studied by the time-resolved laser fluorescence spectroscopy
- Am(III) and Eu(III) uptake on hematite in the presence of humic acid
- Luminescence properties of tetravalent uranium in aqueous solution
- Scanning transmission X-ray microscopy as a speciation tool for natural organic molecules
- Formation of hydroxyapatite in soils using calcium citrate and sodium phosphate for control of strontium migration
- Influence of humic substances on the 63Ni migration through crushed rock media
- U, Th, Eu and colloid mobility in a granite fracture under near-natural flow conditions
- Sorption behavior of europium(III) and curium(III) on the cell surfaces of microorganisms
- Interactions of trivalent and tetravalent heavy metal-siderophore complexes with Pseudomonas fluorescens
- In-situ diffusion of HTO, 22Na+, Cs+ and I- in Opalinus Clay at the Mont Terri underground rock laboratory
- Results of the colloid and radionuclide retention experiment (CRR) at the Grimsel Test Site (GTS), Switzerland – impact of reaction kinetics and speciation on radionuclide migration
- Fracture flow and radionuclide transport in block-scale laboratory experiments
- Comparison between in situ and laboratory diffusion studies of HTO and halides in Opalinus Clay from the Mont Terri
- Solubility constraints on uranium concentrations in groundwaters of the Tono uranium deposit, Japan
- Mobility of uranium in tertiary argillaceous sediments – a natural analogue study
- Redistribution of U, Pb and REE in association with alteration of uranium minerals from the Koongarra deposit, Northern Territory, Australia
- Towards a common thermodynamic database for speciation models
- Geochemically derived non-gaseous radionuclide source term for the Asse salt mine – assessment for the use of a Mg(OH)2-based backfill material
- Simulation of remediation alternatives for a 137Cs contaminated soil
- Simulating reactive transport in time dependent multiphase flow problems
- Reactive transport modelling of a spent fuel repository in a stiff clay formation considering excavation damaged zones
- Coupled transport/reaction modelling of copper canister corrosion aided by microbial processes
