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  • Uranium speciation studies at alkaline pH and in the presence of hydrogen peroxide using time-resolved laser-induced fluorescence spectroscopy

     Martinez Torrents, Albert; Meca, Sandra; Baumann, Nils; Marti Gregorio, Vicenç; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Casas Pons, Ignasi
    Polyhedron
    Date of publication: 2013-05
    Journal article

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    Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used to study the speciation of uranium(VI) at very alkaline pH (11-13), at room temperature and in the absence of CO2. In this case, at pH = 11, two different fluorescence lifetimes appeared, which were attributed to the species UO2(OH)(3)(-) and (UO2)(3)(OH)(7)(-). At pH = 13, no fluorescence was detected, indicating that the predominant species, UO2(OH)(4)(2-), is not fluorescent. At pH = 12, the lifetime obtained is attributed to the predominant species UO2(OH)(3). Because of the absence of fluorescence of the UO2(OH)(4)(2-) species at room temperature, measurements at 10 K were made, obtaining two different lifetimes in the pH range between 12 and 13.5, indicating the presence of two different species: UO2(OH)(3)(-) and UO2(OH)(4)(2-). The difference between the lifetimes allowed the calculation of the contribution of each species to the total fluorescence signal intensity. From the experiments carried out in the presence of hydrogen peroxide, it was observed that hydrogen peroxide produces a quenching effect to the fluorescence of the uranium species. At pH 12 the quenching is static, which points to the formation of a non-fluorescent complex between U(VI) and hydrogen peroxide. Using the Stern-Volmer equation for static quenching, the equilibrium formation constant of the first species, UO2O2(OH)(2)(2-), was calculated to be logK(0) = 28.7 +/- 0.4, which is similar to the one determined using UV-Visible spectrometry, 28.1 +/- 0.2 Meca et al. (2011) [42]. (C) 2013 Elsevier Ltd. All rights reserved.

    Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used to study the speciation of uranium(VI) at very alkaline pH (11–13), at room temperature and in the absence of CO2. In this case, at pH = 11, two different fluorescence lifetimes appeared, which were attributed to the species UO2(OH)3− and (UO2)3(OH)7−. At pH = 13, no fluorescence was detected, indicating that the predominant species, UO2(OH)42−, is not fluorescent. At pH = 12, the lifetime obtained is attributed to the predominant species UO2(OH)3−. Because of the absence of fluorescence of the UO2(OH)42− species at room temperature, measurements at 10 K were made, obtaining two different lifetimes in the pH range between 12 and 13.5, indicating the presence of two different species: UO2(OH)3− and UO2(OH)42−. The difference between the lifetimes allowed the calculation of the contribution of each species to the total fluorescence signal intensity. From the experiments carried out in the presence of hydrogen peroxide, it was observed that hydrogen peroxide produces a quenching effect to the fluorescence of the uranium species. At pH 12 the quenching is static, which points to the formation of a non-fluorescent complex between U(VI) and hydrogen peroxide. Using the Stern–Volmer equation for static quenching, the equilibrium formation constant of the first species, UO2O2(OH)22−, was calculated to be logK0 = 28.7 ± 0.4, which is similar to the one determined using UV–Visible spectrometry, 28.1 ± 0.2 Meca et al. (2011) [42].

  • Dynamic leaching studies of 48 MWd/kgU UO2 commercial spent nuclear fuel under oxic conditions

     Serrano Purroy, D.; Casas Pons, Ignasi; Gonzalez Robles, E.; Glatz, Jean Paul; Wegen, D.H.; Clarens Blanco, Frederic; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Martínez Esparza, A.
    Journal of nuclear materials
    Date of publication: 2013-03
    Journal article

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    The leaching of a high-burn-up spent nuclear fuel (48 MWd/KgU) has been studied in a carbonate-containing solution and under oxic conditions using a Continuously Stirred Tank Flow-Through Reactor (CSTR). Two samples of the fuel, one prepared from the centre of the pellet (labelled CORE) and another one from the fuel pellet periphery, enriched with the so-called High Burn-Up Structure (HBS, labelled OUT) have been used. For uranium and actinides, the results showed that U, Np, Am and Cm gave very similar normalized dissolution rates, while Pu showed slower dissolution rates for both samples. In addition, dissolution rates were consistently two to four times lower for OUT sample compared to CORE sample. Considering the fission products release the main results are that Y, Tc, La and Nd dissolved very similar to uranium; while Cs, Sr, Mo and Rb have up to 10 times higher dissolution rates. Rh, Ru and Zr seemed to have lower dissolution rates than uranium. The lowest dissolution rates were found for OUT sample. Three different contributions were detected on uranium release, modelled and attributed to oxidation layer, fines and matrix release.

  • Kinetics of hydrogen peroxide consumption in aqueous phase at different hydrogen partial pressures

     Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Sureda Pastor, Rosa Maria; Pablo Ribas, Joan de
    Radiochimica acta
    Date of publication: 2012
    Journal article

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  • Uranium speciation in river sediments contaminated by phosphate ores

     Meca, S.; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Marti Gregorio, Vicenç; Pablo Ribas, Joan de
    Environmental chemistry letters
    Date of publication: 2012-03
    Journal article

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    Large amounts of phosphate ores with high concentrations of uranium were dumped by a phosphate plant into the Flix water reservoir in the Ebre River, Catalonia, NE Spain. These phosphate wastes have been mixed over the years with effluents from other industries as well as with the sediments of the river, resulting in a complex mixture of solid wastes and sediments. No investigations on uranium speciation in such sediments were made because of the complexity of the sediments composition as well as the relatively low uranium content. However, these studies are necessary in order to predict the release of the uranium to the river waters. Here, we studied uranium speciation in sediments from two sampling points of the Flix water reservoir and at depths from 5 to 113 cm. We used room temperature time-resolved laser fluorescence spectroscopy and a three-step sequential extraction procedure described by the Standards, Measurements, and Testing Programme of the European Union. We found that uranium was mainly present in the sediment samples as meta-autunite [Ca(UO2)2(PO4)2 10–12H2O], whose low solubility will result in a low release of uranium to the river waters. In addition, we found that some uranium was linked to sediments by forming surface complexes. We therefore made the first study of uranium speciation in the sediments of the Flix water reservoir.

  • Instant release fraction and matrix release of high burn-up UO2 spent nuclear fuel: Effect of high burn-up structure and leaching solution composition

     Serrano Purroya, D.; Clarens Blanco, Frederic; Gonzalez Robles, E.; Glatz, Jean Paul; Wegen, D.H.; Pablo Ribas, Joan de; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Martínez Esparza, A.
    Journal of nuclear materials
    Date of publication: 2012-08
    Journal article

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    wo weak points in Performance Assessment (PA) exercises regarding the alteration of Spent Nuclear Fuel (SNF) are the contribution of the so-called Instant Release Fraction (IRF) and the effect of High Burn-Up Structure (HBS). This manuscript focuses on the effect of HBS in matrix (long term) and instant release of a Pressurised Water Reactor (PWR) SNF irradiated in a commercial reactor with a mean Burn-Up (BU) of 60 GWd/tU. In order to study the HBS contribution, two samples from different radial positions have been prepared. One from the centre of the SNF, labelled CORE, and one from the periphery, enriched with HBS and labelled OUT. Static leaching experiments have been carried out with two synthetic leaching solutions: bicarbonate (BIC) and Bentonitic Granitic Groundwater (BGW), and in all cases under oxidising conditions. IRF values have been calculated from the determined Fraction of Inventory in Aqueous Phase (FIAP). In all studied cases, some radionuclides (RN): Rb, Sr and Cs, have shown higher release rates than uranium, especially at the beginning of the experiment, and have been considered as IRF. Redox sensitive RN like Mo and Tc have been found to dissolve slightly faster than uranium and further studies might be needed to confirm if they can also be considered part of the IRF. Most of the remaining studied RN, mainly actinides and lanthanides, have been found to dissolve congruently with the uranium matrix. Finally, Zr, Ru and Rh presented lower release rates than the matrix. Higher matrix release has been determined for CORE than for OUT samples showing that the formation of HBS might have a protective effect against the oxidative corrosion of the SNF. On the contrary, no significant differences have been observed between the two studied leaching solutions (BIC and BGW).

  • Disolución Del Combustible Nuclear Gastado en un Almacenamiento Geológico Profundo. Efecto De Los Productos Radiolíticos Y De Formación De Fases Secundarias  Open access

     Sureda Pastor, Rosa Maria
    Defense's date: 2012-09-13
    Department of Chemical Engineering, Universitat Politècnica de Catalunya
    Theses

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    La gestión adecuada de los residuos radiactivos de elevada actividad es uno de los desafíos más complejos en nuestra sociedad industrializada y que suscita gran polémica social. La cantidad de residuos radiactivos producidos ha aumentado considerablemente debido principalmente a la creciente utilización de las centrales nucleares en la generación de energía eléctrica. El almacenamiento en formaciones geológicas contacto, la concentración de radionucleido en disolución y el pH. Los resultados muestran que la formación de esta fase secundaria sobre la superficie del CNG podría representar uno de los principales procesos de retención de radionucleidos. Por otra parte, la estabilidad de estas fases minerales se verá directamente afectada por dos de los variables más críticas en el campo próximo de un AGP que son la radiación y la temperatura. Los efectos a nivel atómico de la radiación ionizante sobre la estructura de los silicatos de U(VI): soddyíta (UO2)2(SiO4)(H2O)2 y uranofana Ca(UO2)2(SiO3OH)2·5H2O, se han investigado utilizando la técnica de microscopía electrónica de transmisión (TEM), permitiendo la observación in situ de los procesos de amorfización/nanocristalización de estas fases. Los estudios térmicos llevados a cabo mediante termogravimetría (TG) y calorimetría diferencial de barrido (DSC) combinado con la caracterización por difracción de rayos X (XRD) han permitido evidenciar la importancia de los procesos de deshidratación en la integridad estructural de cada fase. Finalmente, se ha estudiado la cinética de la reacción entre el peróxido de hidrógeno y el hidrógeno a temperatura ambiente y en ausencia de productos catalíticos. El seguimiento de la reacción se ha realizado a partir de la disminución de la concentración de peróxido de hidrógeno en disolución con el tiempo, observándose un aumento en la velocidad de reacción a medida que la presión de hidrógeno aumenta. Estos resultados indican que el hidrógeno podría actuar como inhibidor de la disolución de la matriz de CNG consumiendo la principal especie responsable del proceso de alteración oxidativa. profundas (AGP) se presenta como la opción más viable y definitiva para estos residuos. Para garantizar la seguridad del repositorio es necesario desarrollar modelos que predigan el comportamiento del combustible nuclear gastado (CNG) a largo plazo, así como la liberación y migración de radionucleidos (RN) al medio ambiente. La alteración del CNG dependerá de una serie de procesos que tienen lugar una vez el agua subterránea entre en contacto con la superficie del combustible como son, la formación de productos radiolíticos, su efecto en la oxidación de la matriz de UO2 y posterior disolución, y por último la precipitación de fases secundarias. El estudio de estas fases como productos finales del proceso de disolución oxidativa de la matriz es de gran interés ya que pueden afectar a la movilización de actínidos y productos de fisión, y al comportamiento a largo plazo del propio combustible. A parte de estos procesos, también hay que considerar la corrosión anóxica de la cápsula de acero que generará una gran cantidad de hidrógeno que puede influir en la disolución del CNG. Con el objetivo de profundizar en algunos aspectos relacionados con los productos radiolíticos y fases secundarias en el entorno más cercano al residuo, el denominado campo próximo de un AGP, en esta tesis se han desarrollado una serie de estudios que se resumen a continuación. En la primera parte, se ha estudiado la influencia de los productos radiolíticos: hipoclorito, clorito y clorato en la velocidad de disolución del UO2 como análogo a la matriz de CNG. Las velocidades de disolución obtenidas en el caso del hipoclorito, siguiendo la misma metodología experimental, resultaron ser más elevadas que las velocidades obtenidas en presencia de los principales oxidantes, como el oxígeno o el peroxido de hidrógeno. Una segunda parte se ha centrado en aumentar el conocimiento de las fases secundarias de U(VI) más representativas del proceso de alteración oxidativa del CNG. Concretamente, se ha estudiado la adsorción de cesio y estroncio sobre el peroxido de uranilo, studtita (UO2O2 4H2O), en función de distintos parámetros como el tiempo de

    La gestió adequada dels residus radioactius d’elevada activitat és un dels desafiaments més complexos en la nostra societat industrialitzada i que suscita gran polèmica social. La quantitat de residus radioactius produïts ha augmentat considerablement degut principalment a la creixent utilització de les centrals nuclears en la generació d’energía eléctrica. L’ emmagatzematge en formacions geològiques profundes (MGP) es presenta com a opció més viable i definitiva per aquests residus. Per tal de garantir la seguretat del repositori es necessari desenvolupar models que prediguin el comportament del combustible nuclear gastat (CNG) a llarg termini, així com l’alliberament i migració de radionúclids (RN) al medi ambient. L’alteració del CNG dependrà d’una sèrie de processos que tenen lloc un cop l’aigua subterrània entri en contacte amb la superfície del combustible como son, la formació de productes radiolítics, el seu efecte en l’oxidació de la matriu de UO2 i posterior dissolució, i por últim la precipitació de fases secundàries. L’estudi d’aquestes fases com a productes finals del procés de dissolució oxidativa de la matriu es de gran interès ja que poden afectar a la mobilització d’actínids i productes de fissió, i al comportament a llarg termini del propi combustible. A part d’aquests processos també s’ha de considerar la corrosió anòxica de la càpsula d’acer, la qual generarà una gran quantitat d’hidrogen que pot influir en la dissolució del CNG. Amb l’objectiu de profunditzar en alguns aspectes relacionats amb els productes radiolítics i fases secundàries en l’entorn més proper al residu, l’anomenat camp pròxim d’un MGP , en aquesta tesis s’han desenvolupat una sèrie d’estudis que es resumeixen a continuació. En la primera part, s’ha estudiat la influencia dels productes radiolíticos: hipoclorit, clorit i clorat en la velocitat de dissolució del UO2 como anàleg a la matriu de CNG. Les velocitats de dissolució obtingudes en el cas del hipoclorit, seguint la mateixa metodologia experimental, varen resultar ser més elevades que les velocitats obtingudes en presencia dels principals oxidants, como l’oxigen o el peròxid de hidrogen. Una segona part s’ha centrat en augmentar el coneixement de fases secundàries de U(VI) més representatives del procés d’alteració oxidativa del CNG. Concretament, s’han estudiat l’adsorció de cesi i estronci sobre el peròxid d’uranil, studtita (UO2O2 4H2O), en funció de diferents paràmetres com son el temps de contacte, la concentració de radionúclid en dissolució i el pH. Els resultats mostren que la formació d’aquesta fase sobre la superfície del CNG podria representar un dels principals processos de retenció de radionúclids. Per altre banda, l’estabilitat d’aquestes fases minerals es veurà directament afectada per dues de les variables més crítiques en el camp pròxim d’un (MGP) que son la radiació i la temperatura. Els efectes a nivell atòmic de la radiació ionitzant sobre l’estructura dels silicats de U(VI): soddyíta (UO2)2(SiO4)(H2O)2 i uranofana Ca(UO2)2(SiO3OH)2·5H2O, s’han investigat utilitzant la tècnica de microscopía electrònica de transmissió (TEM), que permet l’observació in situ dels processos d’amorfització/nanocristalizació d’aquestes fases. Els estudis tèrmics s’han realitzat mitjançant les tècniques de termogravimetria (TG) i calorimetria diferencial d’escombrat (DSC) combinat amb la caracterització per difracció de raigs X (XRD) que han permès evidenciar la importància dels processos de deshidratació en la integritat estructural de cada fase. Finalment, s’ha estudiat la cinètica de la reacció entre el peròxid de hidrogen i el hidrogen a temperatura ambient i en absència de productes catalítics. El seguiment de la reacció s’ha realitzat a partir de la disminució de la concentració de peròxid de hidrogen en dissolució amb el temps. S’ha observat un augment en la velocitat de reacció a mesura que la pressió de hidrogen augmenta. Aquests resultats indiquen que el hidrogen podria actuar com a inhibidor de la dissolució de la matriu de CNG consumint la principal espècie responsable del procés d’alteració oxidativa.

    Adequate management of High-activity radioactive waste is one of the most complex challenges in our industrialized society, which generates a lot of social controversy surrounding this issue. The amount of radioactive waste produced has increased considerably due, mainly, to the increased use of nuclear energy in generating electricity. Storage in deep geological formations is presented as the most viable option for a final disposal of these wastes. To ensure the safety of the repository it is necessary to develop models that predict the behavior of spent nuclear fuel (SNF) in the long-term storage, as well as the release and migration of radionuclides to the environment. The alteration of SNF under expected representative repository conditions will depend on a number of processes that take place once the groundwater come in contact with the surface of the fuel, such as the formation of radiolitic products, its effect on the matrix oxidation and subsequent dissolution, released of radionuclides contained in the fuel matrix and finally, precipitation of secondary phases. The study of these phases as end products of the oxidative dissolution process is of major interest due to the fact that they may affect the mobilization of actinides and fission products by geochemical processes such as adsorption. A part of these processes, we must also consider the anoxic corrosion of the steel capsule that will generate a large amount of hydrogen which can influence in the dissolution of SNF. In order to get deeper into some aspects of radiolytic products and secondary phases in the near-field of a High-level Nuclear Waste (HLNW) repository, in this thesis we have developed a series of studies which are summarized below. In the first part, the influence of hypochlorite, chlorite and chlorate in the dissolution rate of UO2 as a chemical analogue of the spent fuel matrix, has been studied experimentally. The dissolution rates obtained in this work are found to be higher than the rates determined in the presence of either oxygen or hydrogen peroxide obtained with same experimental methodology. A second part is focused on increasing the knowledge of the most representative secondary phases of U(VI) formed during the oxidative alteration of SNF. Specifically, the adsorption of cesium and strontium onto uranyl peroxide, studtite (UO2O2 4H2O), has been studied as a function of time, radionuclide concentration in solution and pH. The results show that this secondary solid phase formation on the SNF surface could be an important mechanism involved in the retention of radionuclides. On the other hand, the stability of these mineral phases will be directly affected by two of the most critical variables in the near-field of HLNW are radiation and temperature. Atomic-level effects of ionizing radiation on the structure of U(VI) silicates: soddyite (UO2)2(SiO4)(H2O)2 and uranophana Ca(UO2)2(SiO3OH)2·5H2O have been investigated using electron beam irradiation in a transmission electron microscope (TEM), which allows in situ observation of amorphization/nanocristallization processes of these phases. Thermal studies carried out by thermogravimetry (TG) and differential scanning calorimetry (DSC) combined with X-ray diffraction (DRX) have demostrated the importance of dehydration processes in the structural integrity for each phase. Finally, the reaction between aqueous hydrogen peroxide solutions and hydrogen has been studied at room temperature and in the absence of catalytic products. The reaction evolution has been determined by the decrease of hydrogen peroxide concentration with time. A clear effect has been observed, and the rate of reaction is found to be enhanced as the hydrogen pressure is increased. These results indicate that hydrogen could act as an inhibitor of spent fuel matrix dissolution through the consumption of the main species responsible for the oxidative alteration process.

  • Study of Radionuclide Release in commercials UO2 Spent Nuclear Fuels

     Gonzalez-robles Corrales, Ernesto
    Defense's date: 2011-11-22
    Department of Chemical Engineering, Universitat Politècnica de Catalunya
    Theses

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    Determination of the equilibrium formation constants of two U(VI)-peroxide complexes at alkaline pH  Open access

     Meca, S.; Martinez Torrents, Albert; Marti Gregorio, Vicenç; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Pablo Ribas, Joan de
    Dalton transactions
    Date of publication: 2011
    Journal article

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    The formation of uranyl-peroxide complexes was studied at alkaline media by using UV-Visible spectrophotometry and the STAR code. Two different complexes were found at a H2O2/U(VI) ratio lower than 2. A graphical method was used in order to obtain the formation constants of such complexes and the STAR program was used to refine the formation constants values because of its capacity to treat multiwavelength absorbance data and refining equilibrium constants. The values obtained for the two complexes identified [...] At hydrogen peroxide concentrations higher than 10-5 mol dm-3, and in the absence of carbonate, the UO2(O2)2(OH)2 4- complex is predominant in solution, indicating the significant peroxide affinity of peroxide ions for uranium and the strong complexes of uranium(VI) with peroxide.

  • Effects of ionizing radiation and temperature on uranyl silicates: Soddyite (UO2)2(SiO4)(H2O)2 and uranophane Ca(UO2)2(SiO3OH)2 3.5H2O

     Sureda Pastor, Rosa Maria; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Quiñones Ruiz, Jose Miguel; Zhang, Jun-Ying; Ewing, R.C.
    Environmental science and technology
    Date of publication: 2011-03-15
    Journal article

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  • Transport of strontium through a Ca-bentonite (Almeria, Spain) and comparison with MX-80 Na-bentonite: experimental and modelling

     Valderrama Angel, Cesar Alberto; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Martínez Martínez, María R.
    Water, air and soil pollution
    Date of publication: 2011-06
    Journal article

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  • Sorption and mobility of Sb(V) in calcareous soils of Catalonia (NE Spain): Batch and column experiments

     Martínez Lladó, Xavier; Valderrama Angel, Cesar Alberto; Rovira Boixaderas, Miguel Arcangel; Marti Gregorio, Vicenç; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de
    Geoderma
    Date of publication: 2011-01-15
    Journal article

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    The sorption of Sb(V) onto natural calcareous soils was studied in batch and column experiments as a function of physicochemical properties of the soil, namely: organic matter, the active fraction of Fe and Al and the pH of the soils. Batch experiments were performed in order to determine the sorption capacity and the kinetic rate of the sorption. Freundlich isotherm described properly the equilibrium experimental data and the kinetic results show that the sorption was very slow in all the soils studied (equilibrium after 7 days) when compared with literature data for Sb(V) sorption onto soils with higher iron content. Column experiments were carried out in order to determine the mobility of Sb(V) in the soils. The Thomas model can describe partially the breakthrough curves obtained for the Sb(V) sorption on the soils. The fitting of the model to the experimental data would indicate that transport and kinetic parameters also affected the dynamic sorption behavior. The experimental breakthrough curves can be properly described by the convective–dispersive equation (CDE) by using the CXTFIT code, and the parameters obtained by the model were in concordance to the sorption capacity reported in the column experiments. This study indicates that sorption of Sb(V) onto the soils is mainly affected in batch experiments by their ‘active’ Fe and Al content; while in column experiments organic matter content appeared as an important parameter. Desorption experiments resulted in a metalloid recovery above 90%, which indicates a fast and effective method to recover Sb(V) from calcareous soils and has implications for its geochemical behavior (vertical mobility in soil profiles) as a result of its relatively low Sb retention.

  • Statistical testing based methodology for the analysis of soil pollution evidence

     Marti Gregorio, Vicenç; Pablo Ribas, Joan de; Gibert Agullo, Oriol; Gimenez Izquierdo, Francisco Javier; Martínez Lladó, Xavier; De Fays, Isolda
    International UFZ-Deltares/TNO Conference, on Management of Soil, Groundwater and Sediments
    Presentation's date: 2010-09-22
    Presentation of work at congresses

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  • Assessment of heterotrophic and autotrophic denitrification in aquifers by using batch tests

     Calderer, M.; Marti Gregorio, Vicenç; Pablo Ribas, Joan de; Rovira Boixaderas, Miguel Arcangel; Gibert Agullo, Oriol; Gimenez Izquierdo, Francisco Javier
    International UFZ-Deltares/TNO Conference, on Management of Soil, Groundwater and Sediments
    Presentation's date: 2010-09-22
    Presentation of work at congresses

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  • Sorption of strontium on uranyl peroxide: implications for a high-level nuclear waste repository

     Sureda Pastor, Rosa Maria; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Martínez Lladó, Xavier
    Journal of hazardous materials
    Date of publication: 2010-09-15
    Journal article

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    Strontium-90 is considered the most important radioactive isotope in the environment and one of the most frequently occurring radionuclides in groundwaters at nuclear facilities. The uranyl peroxide studtite (UO2O2 center dot 4H(2)O) has been observed to be formed in spent nuclear fuel leaching experiments and seems to have a relatively high sorption capacity for some radionuclides. In this work, the sorption of strontium onto studtite is studied as a function of time. strontium concentration in solution and pH. The main results obtained are (a) sorption is relatively fast although slower than for cesium; (b) strontium seems to be sorbed via a monolayer coverage of the studtite surface, (c) sorption has a strong dependence on ionic strength, is negligible at acidic pH, and increases at neutral to alkaline pH (almost 100% of the strontium in solution is sorbed above pH 10). These results point to uranium secondary solid phase formation on the spent nuclear fuel as an important mechanism for strontium retention in a high-level nuclear waste repository (HLNW). (C) 2010 Elsevier B.V. All rights reserved.

  • Reactive transport of arsenic(III) and arsenic(V) on natural hematite: Experimental and modeling

     Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Martínez Martínez, María R.; Rovira Boixaderas, Miguel Arcangel; Valderrama Angel, Cesar Alberto
    Journal of colloid and interface science
    Date of publication: 2010-08-01
    Journal article

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  • Cesium sorption on studtite (UO2O2·4H2O)

     Gimenez Izquierdo, Francisco Javier; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de; Casas Pons, Ignasi; Sureda Pastor, Rosa Maria; Martínez Lladó, Xavier; Martínez Esparza, A.
    Radiochimica acta
    Date of publication: 2010
    Journal article

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  • Effect of temperature on studtite stability: Thermogravimetry and differential scanning calorimetry investigations

     Rey, A; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Quiñones Ruiz, Jose Miguel; Pablo Ribas, Joan de
    Journal of nuclear materials
    Date of publication: 2009-03
    Journal article

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  • Arsenic removal by goethite and jarosite in acidic conditions and its environmental implications

     Asta, Maria P.; Cama Robert, Jordi; Gimenez Izquierdo, Francisco Javier; Martínez Martínez, María R.
    Journal of hazardous materials
    Date of publication: 2009-06-25
    Journal article

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    Schwertmannite (Fe8O8(OH)5.5(SO4)1.25), jarosite (KFe3(SO4)2(OH)6) and goethite (FeOOH) control natural attenuation of arsenic in acid mine drainage (AMD) impacted areas. Batch experiments were conducted to examine the sorption capacity of synthetic goethite and synthetic jarosite at highly acidic pH (1.5–2.5), at two ionic strengths (0.02–0.15 mol dm−3, NaCl) and at sulphate concentrations in the range of 5 × 10−3 to 2.8 × 10−1 mol dm−3. In the absence of competitive effects of other anions, K-jarosite presents better removal efficiency than goethite for As(V). The maximum sorption capacity is estimated to be 1.2 × 10−4 and 7.0 × 10−6 mol m−2 for jarosite and goethite, respectively, under similar experimental conditions. The variation of arsenic sorbed on goethite as a function of the equilibrium arsenic concentration in solution fits a non-competitive Langmuir isotherm. In the case of K-jarosite, sorption data could not fit a Langmuir or Freundlich isotherm since sulphate–arsenate anion exchange is probably the sorption mechanism. Ionic strength and pH have little effect on the sorption capacity of goethite and jarosite in the small range of pH studied. The presence of sulphate, which is the main anion in AMD natural systems, has a negative effect on arsenic removal since sulphate competes with arsenate for surface sorption sites. Moreover, mobilization of arsenic in the transformation of schwertmannite to jarosite or goethite at pH 2–3 is proposed since the sorption capacities of goethite and K-jarosite are considerably lower than those reported for schwertmannite.

  • Formación y Estabilidad de Fases Secundarias de UO2 en las condiciones de un almacenamiento Geológico profundo.

     Rey Cubero, Alexandra
    Defense's date: 2009-04-29
    Department of Engineering Design, Universitat Politècnica de Catalunya
    Theses

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  • Effect of HBS structure in fast release fraction of 48 GWd/tU PWR fuel

     Pablo Ribas, Joan de; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Clarens Blanco, Frederic
    International Materials Research Congress
    Presentation's date: 2009-05-26
    Presentation of work at congresses

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  • Thorium sorption onto magnetite and ferrihydrate in acidic conditions

     Rojo, I.; Seco, F.; Rovira, M.; Gimenez Izquierdo, Francisco Javier; Cervantes, G.; Marti Gregorio, Vicenç; Pablo Ribas, Joan de
    Journal of nuclear materials
    Date of publication: 2009-01-01
    Journal article

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    Sorption of Th(IV) onto two-line ferrihydrite and magnetite in NaClO4 solutions has been studied as a function of pH and ionic strength revealing that sorption onto both solids increases with pH while it is independent on ionic strength. Sorption capacity of both solids is high, the maximum sorption (almost 100% of Th(IV)) occurs at pH higher than 3.5 for ferrihydrite, and higher than 3.0 for magnetite. Sorption variation with pH was modeled with three different models using the FITEQL 4.0 code: non-electrostatic model, constant capacitance model, and diffuse-double layer model. In all cases, good fit to the experimental data is obtained with one-species: a corner-sharing bidentate-mononuclear surface complex, (triple bond; length of mdashFeO)2Th2+, which coincides with the surface complex postulated on these solids surface in previous spectroscopic studies; however, the monodentate species triple bond; length of mdashFeOThOH2+ also gives a satisfactory fit. Under the experimental conditions of the present study, any effect of possible thorium colloid formation is negligible.

  • Stability of natural and syntehtic uranium (VI) peroxide hydrates under ionizing radiation

     Rey, Alexandra; Utsunomiya, Satoshi; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Ewing, Rodney C.; Pablo Ribas, Joan de
    American mineralogist
    Date of publication: 2009-01-01
    Journal article

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  • GROUND WATER POLLUTION FORM AGRICULTURAL AND INDUSTRIAL SOURCES

     Oliva Moncunill, Josep; Martínez Martínez, María R.; Torras Grane, Josep; Gibert Agullo, Oriol; Pablo Ribas, Joan de; Gimenez Izquierdo, Francisco Javier
    Participation in a competitive project

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  • The role of uranium peroxide studtite on the retention of Cs, Sr and Se(VI)

     Pablo Ribas, Joan de; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Sureda Pastor, Rosa Maria; Rovira Boixaderas, Miguel Arcangel
    International Materials Research Congress
    Presentation's date: 2009-05-26
    Presentation of work at congresses

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  • Combined effect of H2O2 and HCO3- on UO2(s) dissolution rates under anoxic conditions

     Casas Pons, Ignasi; Pablo Ribas, Joan de; Clarens Blanco, Frederic; Gimenez Izquierdo, Francisco Javier; Merino, J; Bruno, J.; Martínez Esparza, A.
    Radiochimica acta
    Date of publication: 2009
    Journal article

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  • Leaching of 53 MW/d kg U spent nuclear fuel in a flow-through reactor

     Serrano Purroy, D.; Clarens Blanco, Frederic; Glatz, J P; Wegen, D; Christiansen, B; Pablo Ribas, Joan de; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Martínez Esparza, A.
    Radiochimica acta
    Date of publication: 2009
    Journal article

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  • Antimony(V) sorption and mobility in calcareous soils

     Marti Gregorio, Vicenç; Rovira Boixaderas, Miguel Arcangel; Martinez-Lladó, X; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de
    Geochimica et cosmochimica acta
    Date of publication: 2008-07
    Journal article

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  • Sorption of selenium(IV) and selenium(VI) onto natural iron oxides: Goethite and Hematite

     Rovira Boixaderas, Miguel Arcangel; Gimenez Izquierdo, Francisco Javier; Martínez Lladó, Xavier; Martínez-Lladó, X; Pablo Ribas, Joan de; Duro, L
    Journal of hazardous materials
    Date of publication: 2008-06
    Journal article

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  • Determination of UO2(s) dissolution rates in a hydrogen peroxide medium as a function of pressure and temperature

     Casas Pons, Ignasi; Borrell Matas, Marc; Sanchez, L; Pablo Ribas, Joan de; Gimenez Izquierdo, Francisco Javier; Clarens Blanco, Frederic
    Journal of nuclear materials
    Date of publication: 2008-03
    Journal article

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  • UO2 dissolution in the presence of hydrogen peroxide at pH>11

     Meca, S; Marti Gregorio, Vicenç; Pablo Ribas, Joan de; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi
    Radiochimica acta
    Date of publication: 2008-09
    Journal article

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  • Sorption of selenium(IV) and selenium(VI) onto natural iron oxides: Goethite and hematite

     Rovira Boixaderas, Miguel Arcangel; Gimenez Izquierdo, Francisco Javier; Martínez Martínez, María R.; Marti Gregorio, Vicenç; Pablo Ribas, Joan de; Martinez-Llado, X; Duro, L
    Journal of hazardous materials
    Date of publication: 2008-01
    Journal article

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    Selenium is a toxic element with a relatively high mobility in the natural waters. Iron oxy-hydroxides might play an important role in the migration of this element as well as on its removal from contaminated water. In this work we study the interaction of Se(IV), and Se(VI) with natural iron oxides hematite and goethite through two series of batch experiments at room temperature. In the first series, sorption as a function of initial selenium concentration is studied and the results have been fitted with Langmuir isotherms. In a second series of experiments, sorption is studied as a function of pH, being the main trend an increase of the sorption at acidic pH. The variation of the sorption with pH has been modelled with a triple layer surface complexation model and using the FITEQL program. The experimental data have been modelled considering for the Se(IV) the formation of the FeOSe(O)O− complex onto the hematite surface, and a mixture of FeOSe(O)O−, and FeOSe(O)OH onto the goethite surface. For Se(VI) the surface complex considered is FeOH2 +–SeO4 2− on both goethite and hematite.

  • Sorption of antimony (V) onto synthetic goethite in carbonate medium

     Martinez-Llado, X; Martínez Lladó, Xavier; Pablo Ribas, Joan de; Gimenez Izquierdo, Francisco Javier; Ayora Ibáñez, Carlos; Marti Gregorio, Vicenç; Rovira Boixaderas, Miguel Arcangel
    Solvent extraction and ion exchange
    Date of publication: 2008-06
    Journal article

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    The sorption kinetics of antimony(V) on synthetic goethite is very fast compared to the sorption of other metals on goethite (e.g. arsenic and selenium) and depends on temperature, with an activation energy of 49+9 kJ . mol21 in the temperature range 15–358C. Sorption isotherms have been developed at different temperatures and ionic strength values. The results have been modelled using a Langmuir isotherm and there is not a considerable influence of neither the temperature in the range studied (158C–358C), nor the ionic strength (between 0.001 and 0.01 mol . dm23). Sorption is very high at pH values lower than 8, at more alkaline pH, the sorption decreases with pH, as expected considering the Antimony(V) predominating complex in solution, Sb(OH)6 2. Triple-layer model successfully describes the data obtained by assuming a bidentate edge-sharing surface complex of antimonate on the surface of goethite.

  • Secondary phase formation on UO2 in phosphate media

     Rey, A.; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Clarens Blanco, Frederic; Pablo Ribas, Joan de
    Applied geochemistry
    Date of publication: 2008-04-08
    Journal article

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    he dissolution of UO2 (a chemical analog of uraninite and of spent nuclear fuel) has been studied by using a flow-through reactor. The UO2 dissolution rates at total View the MathML source concentrations of 10−4, 10−5, and 10−6 mol dm−3 have been determined to be: 1.3 × 10−10 mol m−2 s−1, 6.7 × 10−11 mol m−2 s−1, and 2.0 × 10−11 mol m−2 s−1, respectively. The dissolution rates determined are found to be higher than the ones determined for similar carbonate concentrations. Moreover, the surface of the UO2 has been studied in static tests by means of the scanning force microscopy technique (SFM) in order to follow the formation of any secondary solid phase on its surface. The formation of chernikovite (H2(UO2)2(PO4)2 · 8H2O) has been observed at a 10−4 M total View the MathML source concentration, while no uranyl-phosphate secondary phases have been found at lower View the MathML source concentrations. In experiments performed in the presence of both carbonate and phosphate, no precipitation of secondary phases has been observed. It is postulated that this is due to the formation of the highly stable uranyl-carbonate complexes in solution.

  • Arsenic sorption onto natural hematite, magnetite, and goethite

     Gimenez Izquierdo, Francisco Javier; Martínez Martínez, María R.; Pablo Ribas, Joan de; Rovira, M; Duro, L
    Journal of hazardous materials
    Date of publication: 2007-03
    Journal article

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  • A spectroscopic study of uranium(VI) interaction with magnetite

     El Aamrani, Fatima Zohra; Gimenez Izquierdo, Francisco Javier; Rovira Boixaderas, Miguel Arcangel; Seco, F; Duro, L; Grive, M; Bruno Salgot, Jorge; Pablo Ribas, Joan de
    Applied surface science
    Date of publication: 2007-08
    Journal article

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  • Interaction of uranium with in situ anoxically generated magnetite on steel

     Rovira Boixaderas, Miguel Arcangel; El Aamrani, Fatima Zohra; Duro, L; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Bruno Salgot, Jorge
    Journal of hazardous materials
    Date of publication: 2007-08
    Journal article

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  • Sorption of cesium on freshly precipitated studtite (UO4·4H2O). Kinetics of sorption and sorption isotherm

     Gimenez Izquierdo, Francisco Javier
    International Workshop on Mobile Fission and Activation Products in Nuclear Waste Disposal
    Presentation's date: 2007-01-11
    Presentation of work at congresses

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  • Rn fractional release of high-burnup fuel:effect of hbs and estimation of accesible grain boundary

     Clarens Blanco, Frederic; Serrano-Purroy, D; Martínez-Esparza, A; Wegen, D; Gonzalez-Robles, E; Pablo Ribas, Joan de; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Christiansen, B; Glatz, J P
    MRS Symposium: Scientific basis for nuclear waste managementEMENT
    Presentation of work at congresses

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  • Stability of synthetic uranium(VI) peroxide hydrates under ionizing radiation

     Gimenez Izquierdo, Francisco Javier
    Migration 2007
    Presentation's date: 2007-01-01
    Presentation of work at congresses

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  • Sorption of cesium on freshly precipitated studtite (UO4¿4H2O). Kinetics and sorption and sorption isotherm

     Gimenez Izquierdo, Francisco Javier; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de; Casas Pons, Ignasi; Martínez-Esparza, A
    MOBILE FISSION AND ACTIVATION PRODUCTS IN NUCLEAR WASTE DISPOSAL
    Presentation of work at congresses

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  • KINETICS OF UO2(s) DISSOLUTION IN THE PRESENCE OF HYPOCHLORITE, CHLORITE AND CHLORATE SOLUTIONS

     Sureda, R; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de
    MRS Symposium: Scientific basis for nuclear waste managementEMENT
    Presentation of work at congresses

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  • MAGNETITE SORPTION CAPACITY FOR STRONTIUM AS A FUNCTION OF pH

     Pablo Ribas, Joan de; Rovira Boixaderas, Miguel Arcangel; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Clarens Blanco, Frederic
    MRS Symposium: Scientific basis for nuclear waste managementEMENT
    Presentation of work at congresses

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  • Sorption of selenium (IV) and selenium (VI) onto magnetite

     Martínez Martínez, María R.; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Rovira Boixaderas, Miguel Arcangel; Duro, L
    Applied surface science
    Date of publication: 2006-03
    Journal article

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  • The use of a high-FeO olivine as a redox buffer in a nuclear waste repository

     Gimenez Izquierdo, Francisco Javier; Rovira Boixaderas, Miguel Arcangel; Clarens Blanco, Frederic; Casas Pons, Ignasi; Duro Pérez, Lara; Grivé, M; Bruno Salgot, Jorge; Pablo Ribas, Joan de
    Journal of contaminant hydrology
    Date of publication: 2006-06
    Journal article

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  • Arsenite adsorption on different natural iron oxide minerals: hematite, goethite and magnetite

     Gimenez Izquierdo, Francisco Javier; Martínez Martínez, María R.; Pablo Ribas, Joan de; Rovira, M; Duro, L; Martinez-Lladó, X
    5th European Meeting on Chemical Engineering and Environment
    Presentation of work at congresses

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  • Development of a Matrix Alteration Model (MAM)

     Martínez, A Esparza; Cuñado, M A; Gago, J A; Quiñones Ruiz, Jose Miguel; Iglesias, E; Cobos, J; González, A De La Huebra; CERA, E; Merino, J; BRUNO, J; Pablo Ribas, Joan de; Casas Pons, Ignasi; Clarens Blanco, Frederic; Gimenez Izquierdo, Francisco Javier
    ENRESA: Empresa Nacional de Residuos Radiactivos
    Date of publication: 2005-01
    Journal article

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  • The dissolution of high-FeO olivine rock from the Lovasjärvi intrusion (SE-Finland) at 25ºC as a function of pH

     Duro Pérez, Lara; El Aamrani, Fatima Zohra; Rovira Boixaderas, Miguel Arcangel; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Pablo Ribas, Joan de; Bruno Salgot, Jorge
    Applied geochemistry
    Date of publication: 2005-07
    Journal article

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  • The oxidative dissolution of unirradiated UO2 by hydrogen peroxide as a fucntion of pH

     Clarens Blanco, Frederic; Pablo Ribas, Joan de; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Rovira Boixaderas, Miguel Arcangel; Merino, J; CERA, E; Bruno Salgot, Jorge; Quiñones Ruiz, Jose Miguel; Martínez-Esparza, A
    Journal of nuclear materials
    Date of publication: 2005-10
    Journal article

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  • Oxidation and dissolution of UO2 in bicarbonate media: Implications for the spent fuel oxidative dissolution mechanism

     Gimenez Izquierdo, Francisco Javier; Clarens Blanco, Frederic; Casas Pons, Ignasi; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de; Bruno Salgot, Jorge
    Journal of nuclear materials
    Date of publication: 2005-10
    Journal article

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  • Radiolytic modelling of spent fuel oxidative dissolution mechanism. Calibration against UO2 dynamic leaching experiments

     Merino, J; CERA, E; Bruno Salgot, Jorge; Quiñones Ruiz, Jose Miguel; Casas Pons, Ignasi; Clarens Blanco, Frederic; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Rovira Boixaderas, Miguel Arcangel; Martínez-Esparza, A
    Journal of nuclear materials
    Date of publication: 2005-11
    Journal article

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