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The fate of radiolytic oxidants during spent fuel leaching in the presence of dissolved near field hydrogen
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Kastriot Spahiu
Published/Copyright:
September 25, 2009
Summary
In most European disposal concepts, one expects large amounts of dissolved hydrogen produced by the anoxic corrosion of iron inside a damaged container. At repository temperatures (<100 °C), dissolved hydrogen is quite inert and is not expected to contribute to the redox capacity of the deep groundwaters. In a previous work from this laboratory we observed a large impact of dissolved hydrogen on the dissolution of the spent fuel in stainless steel autoclaves. In this work we report data on spent fuel dissolution obtained using quartz lined autoclaves to ensure that there is no contact between the solution and the metallic parts; we also made a number of other experimental improvements. The autoclave was filled with a solution 10 mM NaCl, 2 mM NaHCO3 and with H2+0.03% CO2 at a pressure of 0.5 MPa in the remaining free volume. The leaching of PWR spent fuel powder, placed in a gold basket, was studied during more than one year by analysing solution samples taken at regular time intervals. Special care was devoted to the study of the initial phase of the dissolution that was not investigated previously. In spite of the ten times lower hydrogen concentration as compared to the study in stainless steel autoclaves, extremely low concentrations of uranium (less than 10-9 M) were again measured in the solution samples; this was the case also for most of the redox sensitive fuel components. The uranium levels in solution remained practically constant during the whole leaching period, indicating the absence of any oxidative dissolution of the spent fuel matrix. In order to follow the fate of radiolytic oxidants, gas phase analyses were also carried out. The radiolytic oxygen levels in the autoclave measured after one year leaching were below the detection limit. A discussion of the fate of the radiolytic oxidants in these experiments and the mechanism of the hydrogen activation is also presented. The main conclusion is that for concentrations of dissolved hydrogen above 4 mM, no measurable oxidative dissolution of the UO2 matrix seems to occur in the studied systems.
Published Online: 2009-9-25
Published in Print: 2004-11-1
© 2004 Oldenbourg Wissenschaftsverlag GmbH
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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
