Puentes de García Rodríguez, Spain
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Richard L.,University of Lorraine | Gaona X.,Amphos 21 | Gaona X.,Karlsruhe Institute of Technology
Geochimica et Cosmochimica Acta | Year: 2011

A critical evaluation has been made of the thermodynamic properties reported in the literature for 43 organic iodine compounds in the solid, liquid, or ideal gas state. These compounds include aliphatic, cyclic and aromatic iodides, iodophenols, iodocarboxylic acids, and acetyl and benzoyl iodides. The evaluation has been made on the basis of carbon number systematics and group additivity relations, which also allowed to provide estimates of the thermodynamic properties of those compounds for which no experimental data were available. Standard molal thermodynamic properties at 25 °C and 1 bar and heat capacity coefficients are reported for 13 crystalline, 29 liquid, and 39 ideal gas organic iodine compounds, which can be used to calculate the corresponding properties as a function of temperature and pressure. Values derived for the standard molal Gibbs energy of formation at 25 °C and 1. bar of these crystalline, liquid, and ideal gas organic iodine compounds have subsequently been combined with either solubility measurements or gas/water partition coefficients to obtain values for the standard partial molal Gibbs energies of formation at 25 °C and 1 bar of 32 aqueous organic iodine compounds. The thermodynamic properties of organic iodine compounds calculated in the present study can be used together with those for aqueous inorganic iodine species to predict the organic/inorganic speciation of iodine in marine sediments and petroleum systems, or in the near- and far-field of nuclear waste repositories. © 2011 Elsevier Ltd.


Colas E.,Amphos 21 | Grive M.,Amphos 21 | Rojo I.,Fundacio Center Tecnologic | Duro L.,Amphos 21
Journal of Solution Chemistry | Year: 2013

α-Hydroxy carboxylate ligands like gluconate or polyaminocarboxylate ligands such as ethylenediaminetetraacetate (EDTA) are frequently used in decontamination procedures at nuclear power plants. The presence of these organic substances among nuclear wastes could enhance the solubility of actinides by forming soluble complexes. Thermodynamic data on the stability of gluconate and EDTA with actinides are essential to predict their increase in mobility, especially in high pH systems characteristic of cement environments of a nuclear waste repository. In this work, the solubility of thorium oxyhydroxide in the presence of gluconate and EDTA has been studied. The results highlight the key role of these organics in increasing the solubility of thorium at pHc = 12. The presence of calcium at concentrations below 10-2 mol·dm-3 (characteristic of cement porewaters corresponding to cement compositions at the second degradation stage) does not seem to affect significantly the thorium solubility under the studied conditions. © 2013 Springer Science+Business Media New York.


Grive M.,Amphos 21 | Duro L.,Amphos 21 | Colas E.,Amphos 21 | Giffaut E.,Parc de la Croix Blanche andra
Applied Geochemistry | Year: 2015

The thermodynamic database ThermoChimie is developed to meet the needs of performance assessment of radioactive waste disposals, particularly in the context of the Cigéo project (www.cigéo.com). To this purpose, the selection of thermodynamic data on radionuclides and chemotoxic elements has been subject to special attention. The aim of this publication is to present the methodology used in the selection of data on radiological and chemical pollutants in the disposal context for ThermoChimie. Data on radionuclides have been selected in the range of conditions of interest for the French radioactive waste disposal concepts, under Callovo-Oxfordian and cementitious conditions. Temperatures up to the thermal peak of 90. °C and high ionic strengths likely developed due to the degradation of certain ILW-LL waste packages are considered in the selection of thermodynamic data in ThermoChimie. The validity of the selected data is assessed with regard to experimental laboratory results as well as natural analogue systems. The selection of stability constants of aqueous species and solid compounds of radionuclides is based on literature review, dedicated experimental programs and estimation methods, leading to consistent data sets with associated uncertainties. The ThermoChimie database is presented as an efficient support to performance assessment, with traceable references and uncertainties for each datum. All the data are accessible under the public website www.thermochimie-tdb.com. © 2014 Elsevier Ltd.


Domenech C.,Amphos 21 | Domenech C.,University of Barcelona | Garcia D.,Amphos 21 | Pekala M.,Amphos 21
Science of the Total Environment | Year: 2015

Radionuclide retardation processes during transport are expected to play an important role in the safety assessment of subsurface disposal facilities for radioactive waste. The linear distribution coefficient (Kd) is often used to represent radionuclide retention, because analytical solutions to the classic advection-diffusion-retardation equation under simple boundary conditions are readily obtainable, and because numerical implementation of this approach is relatively straightforward. For these reasons, the Kd approach lends itself to probabilistic calculations required by Performance Assessment (PA) calculations. However, it is widely recognised that Kd values derived from laboratory experiments generally have a narrow field of validity, and that the uncertainty of the Kd outside this field increases significantly. Mechanistic multicomponent geochemical simulators can be used to calculate Kd values under a wide range of conditions. This approach is powerful and flexible, but requires expert knowledge on the part of the user.The work presented in this paper aims to develop a simplified approach of estimating Kd values whose level of accuracy would be comparable with those obtained by fully-fledged geochemical simulators. The proposed approach consists of deriving simplified algebraic expressions by combining relevant mass action equations. This approach was applied to three distinct geochemical systems involving surface complexation and ion-exchange processes. Within bounds imposed by model simplifications, the presented approach allows radionuclide Kd values to be estimated as a function of key system-controlling parameters, such as the pH and mineralogy.This approach could be used by PA professionals to assess the impact of key geochemical parameters on the variability of radionuclide Kd values. Moreover, the presented approach could be relatively easily implemented in existing codes to represent the influence of temporal and spatial changes in geochemistry on Kd values. © 2015 Elsevier B.V.


Pique A.,CAT ENVIRO Geochemical Consultancy | Arcos D.,Amphos 21 | Grandia F.,Amphos 21 | Molinero J.,Amphos 21 | And 2 more authors.
Ambio | Year: 2013

Scenarios of barrier failure and radionuclide release to the near-surface environment are important to consider within performance and safety assessments of repositories for nuclear waste. A geological repository for spent nuclear fuel is planned at Forsmark, Sweden. Conceptual and numerical reactive transport models were developed in order to assess the retention capacity of the Quaternary till and clay deposits for selected radionuclides, in the event of an activity release from the repository. The elements considered were carbon (C), chlorine (Cl), cesium (Cs), iodine (I), molybdenum (Mo), niobium (Nb), nickel (Ni), radium (Ra), selenium (Se), strontium (Sr), technetium (Tc), thorium (Th), and uranium (U). According to the numerical predictions, the repository-derived nuclides that would be most significantly retained are Th, Ni, and Cs, mainly through sorption onto clays, followed by U, C, Sr, and Ra, trapped by sorption and/or incorporation into mineral phases. © 2013 The Author(s).


Colas E.,Amphos 21 | Grive M.,Amphos 21 | Rojo I.,Center Tecnologic | Duro L.,Amphos 21
Radiochimica Acta | Year: 2011

Thorium complexation with gluconate has been studied from solubility experiments at gluconate concentrations between 10-6 and 10 -1 mol/l, with pHc between 9 and 13 and I = 0.5 M (NaClO4). Solubility experiments indicate the formation of a 1:1 thorium: gluconate complex. The stability constant for this species, extrapolated to I = 0 by using the SIT (specific interaction theory), has been determined to be log10 K° = - 11.5±0.6 for the reaction: Th4+ +GH4 - +2H2O = Th(OH) 2(GH2)-+4H+ In the presence of ThO2 xH2O, sorption of the organic ligand onto solid surface seems to limit thorium dissolution. © by Oldenbourg Wissenschaftsverlag, München.


Raposo J.R.,University of Santiago de Compostela | Dafonte J.,University of Santiago de Compostela | Molinero J.,Amphos 21
Hydrogeology Journal | Year: 2013

Climate change can impact the hydrological processes of a watershed and may result in problems with future water supply for large sections of the population. Results from the FP5 PRUDENCE project suggest significant changes in temperature and precipitation over Europe. In this study, the Soil and Water Assessment Tool (SWAT) model was used to assess the potential impacts of climate change on groundwater recharge in the hydrological district of Galicia-Costa, Spain. Climate projections from two general circulation models and eight different regional climate models were used for the assessment and two climate-change scenarios were evaluated. Calibration and validation of the model were performed using a daily time-step in four representative catchments in the district. The effects on modeled mean annual groundwater recharge are small, partly due to the greater stomatal efficiency of plants in response to increased CO2 concentration. However, climate change strongly influences the temporal variability of modeled groundwater recharge. Recharge may concentrate in the winter season and dramatically decrease in the summer-autumn season. As a result, the dry-season duration may be increased on average by almost 30 % for the A2 emission scenario, exacerbating the current problems in water supply. © 2012 Springer-Verlag Berlin Heidelberg.


The linkage between the iron and the carbon cycles is of paramount importance to understand and quantify the effect of increased CO2 concentrations in natural waters on the mobility of iron and associated trace elements. In this context, we have quantified the thermodynamic stability of mixed Fe(III) hydroxo-carbonate complexes and their effect on the solubility of Fe(III) oxihydroxides. We present the results of carefully performed solubility measurements of 2-line ferrihydrite in the slightly acidic to neutral-alkaline pH ranges (3.8-8.7) under constant pCO2 varying between (0.982-98.154kPa) at 25°C. The outcome of the work indicates the predominance of two Fe(III) hydroxo carbonate complexes FeOHCO3 and Fe(CO3)3 3-, with formation constants log*β°1,1,1=10.76±0.38 and logβ°1,0,3=24.24±0.42, respectively. The solubility constant for the ferrihydrite used in this study was determined in acid conditions (pH: 1.8-3.2) in the absence of CO2 and at T=(25±1)°C, as log*Ks ,0=1.19±0.41. The relative stability of the Fe(III)-carbonate complexes in alkaline pH conditions has implications for the solubility of Fe(III) in CO2-rich environments and the subsequent mobilisation of associated trace metals that will be explored in subsequent papers. © 2014 Elsevier Ltd.


Reiller P.E.,CEA Saclay Nuclear Research Center | Vercouter T.,CEA Saclay Nuclear Research Center | Duro L.,Amphos 21 | Ekberg C.,Chalmers University of Technology
Applied Geochemistry | Year: 2012

In this paper some of the needs for good quality thermodynamic data in radioactive waste management are highlighted. A presentation of the thermodynamic data produced within the 6th EC framework programme integrated project FUNMIG (Fundamental processes of radionuclide migration) and how these have helped in filling relevant thermodynamic data gaps is given. The manuscript does not intend to be a complete review of thermodynamic data, but a short overview of the aqueous complexation of Am(III), lanthanides (III), U(VI), and Th(IV) by sulfates, silicates, carbonates and phosphates. The work presented is based on the latest developments published in the literature and specifically addressed within the IP FUNMIG. © 2011 Elsevier Ltd.


Grive M.,Amphos 21 | Duro L.,Amphos 21 | Colas E.,Amphos 21 | Giffaut E.,Andra Inc
Applied Geochemistry | Year: 2015

The thermodynamic database ThermoChimie is developed to meet the needs of performance assessment of radioactive waste disposals, particularly in the context of the Cigéo project (www.cigéo.com). To this purpose, the selection of thermodynamic data on radionuclides and chemotoxic elements has been subject to special attention. The aim of this publication is to present the methodology used in the selection of data on radiological and chemical pollutants in the disposal context for ThermoChimie. Data on radionuclides have been selected in the range of conditions of interest for the French radioactive waste disposal concepts, under Callovo-Oxfordian and cementitious conditions. Temperatures up to the thermal peak of 90. °C and high ionic strengths likely developed due to the degradation of certain ILW-LL waste packages are considered in the selection of thermodynamic data in ThermoChimie. The validity of the selected data is assessed with regard to experimental laboratory results as well as natural analogue systems. The selection of stability constants of aqueous species and solid compounds of radionuclides is based on literature review, dedicated experimental programs and estimation methods, leading to consistent data sets with associated uncertainties. The ThermoChimie database is presented as an efficient support to performance assessment, with traceable references and uncertainties for each datum. All the data are accessible under the public website www.thermochimie-tdb.com. © 2014 Elsevier Ltd.

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