Littérature scientifique sur le sujet « Surface radiolysis »
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Articles de revues sur le sujet "Surface radiolysis"
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Mukherjee, Smita, Marie-Claude Fauré, Michel Goldmann et Philippe Fontaine. « Two step formation of metal aggregates by surface X-ray radiolysis under Langmuir monolayers : 2D followed by 3D growth ». Beilstein Journal of Nanotechnology 6 (15 décembre 2015) : 2406–11. http://dx.doi.org/10.3762/bjnano.6.247.
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In order to form a nanostructured metallic layer below a Langmuir monolayer, radiolysis synthesis was carried out in an adapted geometry that we call surface X-ray radiolysis. In this procedure, an X-ray beam produced by a synchrotron beamline intercepts the surface of an aqueous metal-ion solution covered by a Langmuir monolayer at an angle of incidence below the critical angle for total internal reflection. Underneath the organic layer, the X-ray beam induces the radiolytic synthesis of a nanostructured metal–organic layer whose ultrathin thickness is defined by the vertical X-ray penetration depth. We have shown that increasing the X-ray flux on the surface, which considerably enhances the kinetics of the silver layer formation, results in a second growth regime of silver nanocrystals. Here the formation of the oriented thin layer is followed by the appearance of a 3D powder of silver clusters.
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Imanova, Gunel. « Molecular hydrogen production by radiolysis of water on the surface of nano-ZrO2 under the influence of gamma rays ». Synthesis and Sintering 2, no 1 (19 février 2022) : 9–13. http://dx.doi.org/10.53063/synsint.2022.21105.
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In this research, the radiation-heterogeneous processes of water decomposition on the surface of zirconium dioxide nanoparticles (n-ZrO2) were studied. The kinetics of buildup of molecular hydrogen during the radiolytic processes of water decomposition was also examined. The production of H2 and H2O2 through water radiolysis was investigated to develop a computational model and disclose the kinetic behavior of water radiolysis. The enthalpy of ZrO2 nanoparticles was studied at the temperature range T=1200-2900 K, in which ZrO2 nanoparticles has a two-phase transition. Some of the electrons were transported to the surface of the nanoparticles during the physical and physicochemical stages of the process and emitted into the water. At the same time, the migration of energy carriers in radioactively active oxide compounds changed at different intervals depending on the composition, structural stability, and electro-physical properties of the oxides.
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Pastina, Barbara, et Jay A. LaVerne. « An Alternative Conceptual Model for the Spent Nuclear Fuel–Water Interaction in Deep Geologic Disposal Conditions ». Applied Sciences 11, no 18 (15 septembre 2021) : 8566. http://dx.doi.org/10.3390/app11188566.
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For the long-term safety assessment of direct disposal of spent nuclear fuel in deep geologic repositories, knowledge on the radionuclide release rate from the UO2 matrix is essential. This work provides a conceptual model to explain the results of leaching experiments involving used nuclear fuel or simulant materials in confirmed reducing conditions. Key elements of this model are: direct effect of radiation from radiolytic species (including defects and excited states) in the solid and in the first water layers in contact with its surface; and excess H2 may be produced due to processes occurring at the surface of the spent fuel and in confined water volumes, which may also play a role in keeping the spent fuel surface in a reduced state. The implication is that the fractional radionuclide release rate used in most long-term safety assessments (10−7 year−1) is over estimated because it assumes that there is net UO2 oxidation caused by radiolysis, in contrast with the alternative conceptual model presented here. Furthermore, conventional water radiolysis models and radiation chemical yields published in the literature are not directly applicable to a heterogeneous system such as the spent fuel–water interface. Suggestions are provided for future work to develop more reliable models for the long-term safety assessment of spent nuclear fuel disposal.
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Erlandsen, Stanley, Ming Lei, Ines Martin-Lacave, Gary Dunny et Carol Wells. « High Resolution CryoFESEM of Microbial Surfaces ». Microscopy and Microanalysis 9, no 4 (août 2003) : 273–78. http://dx.doi.org/10.1017/s1431927603030502.
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The outer surfaces of three microorganisms, Giardia lamblia, Enterococcus faecalis, and Proteus mirabilis, were investigated by cryo-immobilization followed by sublimation of extracellular ice and cryocoating with either Pt alone or Pt plus carbon. Cryocoated samples were examined at −125°C in either an in-lens field emission SEM or a below-the-lens field emission SEM. Cryocoating with Pt alone was sufficient for low magnification observation, but attempts to do high-resolution imaging resulted in radiolysis and cracking of the specimen surface. Double coating with Pt and carbon, in combination with high resolution backscatter electron detectors, enabled high-resolution imaging of the glycocalyx of bacteria, revealing a sponge-like network over the surface. High resolution examination of bacterial flagella also revealed a periodic substructure. Common artifacts included radiolysis leading to “cracking” of the surface, and insufficient deposition of Pt resulting in the absence of detectable surface topography.
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Garibov, Adil, Yadigar Jafarov, Gunel Imanova, Teymur Agayev, Sevinj Bashirova et Anar Aliyev. « Mechanism of Hydrogen Production in The Processes of Radiation Heterogeneous Splitting of Water with the Presence of Nano-Metal and Nano-MeO ». East European Journal of Physics, no 1 (5 mars 2024) : 460–75. http://dx.doi.org/10.26565/2312-4334-2024-1-51.
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In the study, the optimal values of the ratio of the distance between particles to the particle size in the radiation-heterogeneous radiolysis of water in nano-Me and nano-MeO systems were determined. In those systems, the effect of water density and system temperature on the radiation-chemical release of molecular hydrogen obtained from thermal and radiation-thermal decomposition of water was considered. The article also determined the effect of particle sizes and the type of sample taken on the radiation chemical yield of molecular hydrogen. In the presented article, the change of molecular hydrogen according to adsorbed water and catalyst was studied. Thus, in the case of a suspension of nano-zirconium in water, the energy of electrons emitted from the metal is completely transferred to water molecules, which leads to an increase in the yield of hydrogen. When radiolysis of water in the presence of nano-metals, energy transfer can be carried out mainly with the participation of emitted electrons. Therefore, in the case of radiolysis of water in suspension with n-Zr, the yield of hydrogen increases by 5.4 times compared to the processes of radiolysis in an adsorbed state. However, in radiation-heterogeneous processes of obtaining hydrogen from water in contact with metal systems, it is necessary to take into account that as a result of these processes surface oxidation occurs and after a certain time the systems are converted to n-Me-MeO+H2Oliq. systems. For nano sized oxide compounds, the mean free path of secondary electrons formed as a result of primary processes of interaction of quanta with atoms is commensurate with the particle sizes of nano-oxides (λ ≈ R_(H-оxides)). Further, these electrons interact with the electronic subsystem of silicon. For nanocatalysts, the length of free paths of secondary and subsequent generations of electrons is greater than the size of catalyst particles (R_cat≤100nm). Usually, their energy is sufficient to conduct independent radiolytic processes in the contact medium of the catalyst.
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Carrasco-Flores, Eduardo A., et Jay A. LaVerne. « Surface species produced in the radiolysis of zirconia nanoparticles ». Journal of Chemical Physics 127, no 23 (21 décembre 2007) : 234703. http://dx.doi.org/10.1063/1.2806164.
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Colín-García, M., F. Ortega-Gutiérrez, S. Ramos-Bernal et A. Negrón-Mendoza. « Heterogeneous radiolysis of HCN adsorbed on a solid surface ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 619, no 1-3 (juillet 2010) : 83–85. http://dx.doi.org/10.1016/j.nima.2009.10.074.
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Wang, Honglong, Yaping Sun, Jian Chu, Xu Wang et Ming Zhang. « Intensive study on structure transformation of muscovite single crystal under high-dose γ -ray irradiation and mechanism speculation ». Royal Society Open Science 6, no 7 (juillet 2019) : 190594. http://dx.doi.org/10.1098/rsos.190594.
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Intensive study on structure transformation of muscovite single crystal under high-dose γ -ray irradiation is essential for its use in irradiation detection and also beneficial for mechanism cognition on defect formation within a matrix of clay used in the disposal of high-level radioactive waste (HLRW). In this work, muscovite single crystal was irradiated with Co-60 γ ray in air at a dose rate of 54 Gy min −1 with doses of 0–1000 kGy. Then, structure transformation and mechanism were explored by Raman spectrum, Fourier-transform infrared spectrum, X-ray diffraction, thermogravimetric analysis, CA, scanning electron microscope and atomic force microscopy. The main results show that variations in the chemical/crystalline structure are dose-dependent. Low-dose irradiation sufficiently destroyed the structure, removing Si–OH, thus declining hydrophilicity. With dose increase up to 100 kGy, CA increased from 20° to 40°. Except for hydrophilicity variation, shrink occurred in the (004) lattice plane which later recovered; the variation range at 500 kGy irradiation was 0.5% close to 0.02 Å. The main mechanisms involved were framework break and H 2 O radiolysis. Framework break results in Si–OH removal and H 2 O radiolysis results in extra OH introduction. The extra introduced OH probably results in Si–OH bond regeneration, lattice plane shrink and recovered surface hydrophilicity. The importance of framework break and H 2 O radiolysis on structure transformation is dose-dependence. At low doses, framework break seems more important while at high doses H 2 O radiolysis is important. Generally, variations in the chemical structure and surface property are nonlinear and less at high doses. This indicates using the chemical structure or surface property variation to describe irradiation is correct at low doses but not at high doses. This finding is meaningful for realizing whether muscovite is suitable for detecting high-dose irradiation or not, and mechanism exploration is efficient for identifying the procedure for defect formation within the matrix of clay used in disposal HLRW in practice.
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Yamaguchi, Akinobu, Ikuya Sakurai, Ikuo Okada, Hirokazu Izumi, Mari Ishihara, Takao Fukuoka, Satoru Suzuki et Yuichi Utsumi. « Solid/liquid-interface-dependent synthesis and immobilization of copper-based particles nucleated by X-ray-radiolysis-induced photochemical reaction ». Journal of Synchrotron Radiation 27, no 4 (19 mai 2020) : 1008–14. http://dx.doi.org/10.1107/s1600577520005184.
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X-ray-radiolysis-induced photochemical reaction of a liquid solution enables the direct synthesis and immobilization of nano/micro-scale particles and their aggregates onto a desired area. As is well known, the synthesis, growth and aggregation are dependent on the pH, additives and X-ray irradiation conditions. In this study, it was found that the topography and composition of synthesized particles are also dependent on the types of substrate dipped in an aqueous solution of Cu(COOCH3)2 in the X-ray-radiolysis-induced photochemical reaction. These results are attributed to the fact that a secondary electron induced by the X-ray irradiation, surface or interface on which the particles are nucleated and grown influences the particle shape and composition. This study will shed light on understanding a novel photochemical reaction route induced under X-ray irradiation. The development of this process using the X-ray-radiolysis-induced photochemical reaction in aqueous liquids enables us to achieve the rapid and easy operation of the synthesis, growth and immobilization of special nano/micro-scale complex materials or multifunctional composites.
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Duro, L., O. Riba, A. Martínez-Esparza et J. Bruno. « Modelling the Activation of H2 on Spent Fuel Surface and Inhibiting Effect of UO2 Dissolution ». MRS Proceedings 1518 (2013) : 133–38. http://dx.doi.org/10.1557/opl.2013.76.
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ABSTRACTThe dissolution of spent nuclear fuel is defined in two different time steps, i) the Instant Release Fraction (IRF) occurring shortly after water contacts the solid spent fuel and responsible of the fast release of those radionuclides that have been accumulated in the zones of the spent fuel pellet with low confinement, such as gap and grain boundaries and ii) the long term release of radionuclides confined in the spent fuel matrix, much slower and dependent on the conditions of the water that contacts the spent fuel.Several models have been developed to date to explain the dissolution behavior of spent nuclear fuel under disposal conditions. The Matrix Alteration Model (MAM) is one of the most evolved radiolytic models describing the dissolution mechanism in which an Alteration/Dissolution source term model is based on the oxidative dissolution of spent fuel. Under deep repository conditions and at the expected of water contacting time (after 1000 years of spent fuel storage), α radiation will be the main contributor to water radiolysis. In the current study, simulations evaluating the effect of surface area on the alteration/dissolution of spent fuel matrix are performed considering different particle sizes of spent fuel and simulations integrating the actinides dissolution have been performed considering the precipitation of secondary phases.
Thèses sur le sujet "Surface radiolysis"
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Gaillard, Jérémy. « Réactivité de l’eau à la surface des oxydes mixtes (U,Pu)O2 ». Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20225.
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L'interaction de l'eau avec les surfaces d'oxyde d'actinides demeure relativement peu étudiée. L'adsorption d'eau à la surface de PuO2 et (U,Pu)O2 conduit à la génération de H2 par radiolyse mais également à l'évolution de l'état de surface. L'étude de l'interaction de l'eau avec les surfaces d'oxydes mixtes (U,Pu)O2 requiert de mettre en œuvre des techniques d'analyses peu intrusives. L'étude de l'hydratation de la surface de CeO2 permet d'étudier la pertinence de différentes techniques d'analyses. Les résultats montrent que l'adsorption d'eau à la surface de CeO2 conduit à une évolution de l'état de surface et la formation d'une couche superficielle de type hydroxyde. La réactivité de l'eau à la surface de CeO2 dépend de la température de calcination du précurseur de l'oxyde. Le traitement thermique des surfaces hydratées permet de régénérer l'état de surface. Cette étude sur CeO2 souligne l'intérêt des techniques d'analyse mises en œuvre quant à l'étude de l'hydratation des surfaces. La génération de dihydrogène par radiolyse de l'eau adsorbée est étudiée par une méthode expérimentale fondée sur le renouvellement d'eau à la surface du matériau. L'accumulation de H2 est linéaire durant les premières heures puis tend vers un état stationnaire. Un mécanisme de consommation de H2 est proposé pour expliquer cet équilibre et également l'évolution des surfaces d'oxyde mixtes (U,Pu)O2 témoignée par l'évolution des cinétiques d'accumulation de H2. La cinétique d'accumulation dépend du débit de dose, de la surface spécifique de l'oxyde, de l'humidité relative de l'atmosphère en équilibre ainsi que du taux de plutonium et de l'état de surfaceThe interaction of water with actinides oxide surfaces remains poorly understood. The adsorption of water on PuO2 surface and (U,Pu)O2 surface leads to hydrogen generation through radiolysis but also surface evolution.The study of water interaction with mixed oxide (U,Pu)O2 and PuO2 surfaces requires the implementation of non intrusive techniques. The study of the hydration of CeO2 surface is used to study the effectiveness of different techniques. The results show that the water adsorption leads to the surface evolution through the formation of a hydroxide superficial layer. The reactivity of water on the surface depends on the calcination temperature of the oxide precursor. The thermal treatment of hydrated surfaces can regenerate the surface. The study on CeO2 hydration emphasizes the relevancies of these techniques in studying the hydration of surfaces.The hydrogen generation through water radiolysis is studied with an experimental methodology based on constant relative humidity in the radiolysis cell. The hydrogen accumulation is linear for the first hours and then tends to a steady state content. A mechanism of hydrogen consumption is proposed to explain the existence of the steady state of hydrogen content. This mechanism enables to explain also the evolution of the oxide surface during hydrogen generation experiments as shown by the evolution of hydrogen accumulation kinetics. The accumulation kinetics depends on the dose rate, specific surface area and the relative humidity but also on the oxide aging. The plutonium percentage appears to be a crucial parameter in hydrogen accumulation kinetics
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Lousada, Patrício Cláudio Miguel. « Reactions of aqueous radiolysis products with oxide surfaces : An experimental and DFT study ». Doctoral thesis, KTH, Tillämpad fysikalisk kemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119780.
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The reactions between aqueous radiolysis products and oxide surfaces are important in nuclear technology in many ways. In solid-liquid systems, they affect (and at the same time are dependent on) both the solution chemistry and the stability of materials under the influence of ionizing radiation. The stability of surface oxides is a factor that determines the longevity of the materials where such oxides are formed. Additionally, the aqueous radiolysis products are responsible for corrosion and erosion of the materials. In this study, the reactions between radiolysis products of water – mainly H2O2 and HO radicals – with metal, lanthanide and actinide oxides are investigated. For this, experimental and computational chemistry methods are employed. For the experimental study of these systems it was necessary to implement new methodologies especially for the study of the reactive species – the HO radicals. Similarly, the computational study also required the development of models and benchmarking of methods. The experiments combined with the computational chemistry studies produced valuable kinetic, energetic and mechanistic data. It is demonstrated here that the HO radicals are a primary product of the decomposition of H2O2. For all the materials, the catalytic decomposition of H2O2 consists first of molecular adsorption onto the surfaces of the oxides. This step is followed by the cleavage of the O-O bond in H2O2 to form HO radicals. The HO radicals are able to react further with the hydroxylated surfaces of the oxides to form water and a surface bound HO• center. The dynamics of formation of HO• vary widely for the different materials studied. These differences are also observed in the activation energies and kinetics for decomposition of H2O2. It is found further that the removal of HO• from the system where H2O2 undergoes decomposition, by means of a scavenger, leads to the spontaneous formation of H2. The combined theoretical-experimental methodology led to mechanistic understanding of the reactivity of the oxide materials towards H2O2 and HO radicals. This reactivity can be expressed in terms of fundamental properties of the cations present in the oxides. Correlations were found between several properties of the metal cations present in the oxides and adsorption energies of H2O, adsorption energies of HO radicals and energy barriers for H2O2 decomposition. This knowledge can aid in improving materials and processes important for nuclear technological systems, catalysis, and energy storage, and also help to better understand geochemical processes.QC 20130322
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Luna, Barron Ana Laura. « Synthesis and characterization of new modified photocatalysts for environmental and energy applications ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS105/document.
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De nos jours, la pollution de l'environnement et la crise énergétique sont largement concernés partout dans le monde. Il est une tâche urgente de développer des technologies respectueuses de l'environnement pour les énergies propres alternatives. La photocatalyse est une des méthodes les plus prometteuses pour ces sujets. Le semi-conducteur le plus utilisé dans la photocatalyse est TiO₂ en raison de ses excellentes propriétés physiques et chimiques, de haute disponibilité et à faible coût. La modification de TiO₂ avec des nanoparticules métalliques ont démontré un effet bénéfique sur l'activité photocatalytique de TiO₂.Identifier les facteurs qui régissent la cinétique des processus photocatalytiques et de comprendre le rôle que les nanoparticules métalliques jouent est inhérente à atteindre l'objectif souhaité de développer des systèmes photocatalytiques plus efficaces.Bien que de grands progrès ont été réalisés dans l'étude de l'effet de la modification de surface de TiO₂ avec des IP mono et bimétalliques sur son activité photocatalytique, beaucoup reste encore inconnue. La plupart des enquêtes ont été fondées sur l'étude de la cinétique ou des mécanismes impliqués dans la photocatalyse. Il existe peu d'études rapportées, qui intègrent l'absorption, la dynamique des porteurs de charge et de l'activité photocatalytique.Ce dernier a motivé le développement de ce travail, dont l'objectif principal d'étudier systématiquement l'effet des NPs métalliques sur la surface d'oxyde de titane dans les trois directeurs étapes des procédés photocatalytiques: (1) l'absorption de la lumière (génération de paire électron-trou) (2) dynamique des porteurs de charge, et (3) l'efficacité de l'activité photocatalytiqueNowadays, environment pollution and energy crisis are widely concerned all over the world. It is an urgent task to develop environment-friendly technologies for alternative clean energies. Photocatalysis is one of the most promising methods for such subjects. The most used semiconductor in photocatalysis is TiO₂ due to its excellent physical and chemical properties, high availability and low cost. The modification of TiO₂ with metal nanoparticles has demonstrated have a beneficial effect in the photocatalytic activity of TiO₂.Identifying the factors that govern the kinetics of the photocatalytic processes and understanding the role that metal nanoparticles play is inherent to achieve the desired goal of developing more efficient photocatalytic systems.Although great strides have been made in the study of the effect of surface modification of TiO₂ with mono- and bimetallic NPs on its photocatalytic activity, a lot still remains unknown. Most of the investigations have been based on the study of kinetics or mechanisms involved in photocatalysis. There are few reported studies, which integrate the absorption, dynamics of charge carriers and photocatalytic activity.The later has motivated the development of the present work, having the main objective to study systematically the effect of metal NPs on titania surface in the three principals steps of the photocatalytic processes: (1) absorption of light (generation of electron-hole pair), (2) dynamic of charge carriers, and (3) efficiency of the photocatalytic activity
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Deroche, Arnaud. « Réactivité de l’eau à la surface des oxydes d’actinide. Modifications surfaciques et radiolyse ». Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS112/document.
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Les oxydes d’actinides sont des matériaux hygroscopiques. L’adsorption de l’eau à leurs surfaces est susceptible d’entrainer des modifications quant à la nature ou à son état. Dans le cas des oxydes à fort débit de dose, vient s’ajouter les effets de radiolyse de l’eau, entrainant sa décomposition et générant du dihydrogène. Ces deux aspects, étude de surface et radiolyse de l’eau, ont été étudiés ici. L’étude de la génération de dihydrogène par radiolyse de l’eau adsorbée à la surface a montré que cette génération linéaire dans les premiers temps atteint une concentration stable au bout de plusieurs heures. Cet état stationnaire a été très peu observé, et est absent dans le cas d’humidité importante. Un conditionnement dans une atmosphère contenant du dihydrogène a permis de mettre en lumière une réaction de consommation du dihydrogène par le matériau. Ces expériences ont permis de faire émerger un modèle cinétique basé sur deux réactions de production et de consommation de dihydrogène. La première correspond à la décomposition de l’eau sous l’effet du rayonnement, et pour la seconde il est suspecté une réduction partielle de la surface avec la formation d’une phase sous-stœchiométrique en surface. Cependant, aucune technique d’analyse de surface n’a permis de mettre en évidence formellement cette phase. La chromatographie gazeuse inverse est une technique peu intrusive vis-à-vis des couches d’eau adsorbée du fait des températures et des pressions mis en jeux et de l’absence de dépôt d’énergie. Cette technique a été employée sur des oxydes de thorium et d’uranium. Sur oxyde de thorium, il en résulte un impact de la température de calcination, avec un maximum d’énergie de surface pour une calcination à 650°C. Par ailleurs, il a été montré que la préparation du dioxyde de thorium pouvait impacter l’état de sa surface. En effet, il a été observé une déshydratation de l’oxalate de thorium au fil du temps, impactant la structure de ce dernier. Cette modification se répercute sur la surface de l’oxyde final par une chute de l’énergie de surface et par une modification sur la répartition des sites d’adsorption en surface. Néanmoins un traitement chimique de l’oxalate permet de retrouver la réactivité de surface et une distribution des sites d’adsorption. L’hydratation de la surface montre une augmentation de l’énergie de surface, mais cette augmentation n’est observée que pour des hydratations de longues duréesActinide oxides are hygroscopic materials. The adsorption of water on their surfaces is likely to cause changes in the nature or condition. In the case of oxides with a high dose rate, the effects of radiolysis of the water causes the decomposition of water and generates hydrogen. These two aspects: surface study and radiolysis of water have been studied here.The study of the generation of dihydrogen by radiolysis of water adsorbed on the surface has shown that this linear generation in the early stages reaches a stable concentration after several hours. This stationary state has been very little observed, and is absent in the case of significant humidity. Conditioning in a dihydrogen-containing atmosphere made it possible to highlight a reaction of consumption of dihydrogen by the material. These experiments led to the emergence of a kinetic model based on two reactions of production and consumption of dihydrogen. The first corresponds to the decomposition of the water under the effect of the radiation, and for the second it is suspected a partial reduction of the surface with the formation of a sub-stoichiometric phase on the surface, however no technique of analysis of surface has not formally highlighted this phase.Inverse gas chromatography is a technique that is not very intrusive with respect to the adsorbed water layers because of the temperatures and pressures involved and the absence of energy deposition. This technique has been used on oxides of thorium and uranium. On thorium oxide, this results in an impact of the calcination temperature, with a maximum of surface energy for calcination at 650 ° C. In addition, it has been shown that the preparation of thorium dioxide can impact the state of its surface. Indeed, it has been observed dehydration of thorium oxalate over time, impacting the structure of the latter. This modification affects the surface of the final oxide by a drop-in surface energy and a change in the distribution of surface adsorption sites. Nevertheless, a chemical treatment of oxalate makes it possible to recover the surface reactivity and a distribution of the adsorption sites. The hydration of the surface shows an increase in surface energy, but this increase is observed only for hydrations of long duration.Keywords: water sorption, radiolysis, plutonium, inverse gas chromatography, thorium, uranium
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Diot, Guillaume. « Étude de l'interface oxyde de graphène / 1-eicosyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide par la procédure des films de Langmuir : influence de l'ajout d'or dans la sous-phase ». Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS628.
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Les supercondensateurs à base de liquide ionique (LI) comme électrolyte et de graphène comme électrode sont des dispositifs prometteurs. Ils possèdent une grande densité de puissance mais souffrent d’une faible densité de stockage de l’énergie comparé au batterie actuelles. L’ajout de nanoparticules d’or entre les feuillets de graphène et le LI semble prometteur pour améliorer ces propriétés. Nous utilisons la méthode des films de Langmuir, une procédure permettant d’élaborer et d’étudier des monocouches et des interfaces sur une surface d’eau sous diverses conditions physico-chimiques, pour étudier l’interface oxyde de graphène (GO)/LI. Nous utilisons le liquide ionique [C20mim]+[NTf2]- et l’oxyde de graphène (capables de former un film stable à la surface de l’eau). Nous utilisons l’irradiation de la surface par des rayons X couplée à l’ajout de sel d’or HAuCl4·3H2O dans la sous phase pour former par radiolyse des nanoparticules d’or (AuNPs) sous le film organique. L’objectif de cette thèse est d’étudier la formation de l’interface entre l’OG et le liquide ionique sans et en présence de AuNPs aux interfaces. Pour ce faire, nous utilisons un solvant commun aux deux espèces : le NMP. Ensuite, déposant le film sur une sous-phase formée par une solution d’or, nous utilisons la radiolyse de surface par rayons X pour produire des nanoparticules d’or en contact avec ce film. Nous avons donc tout d’abord étudié l’influence du solvant NMP sur les films purs de liquide ionique et d’oxyde de graphène. La présence de NMP résiduel dans la couche de liquide ionique influence les structures formées. Le NMP est un solvant capable de former une couche stable d’oxyde de graphène à l’interface air/eau. Ainsi, le NMP est à prendre en compte dans l’organisation des interfaces pour le mélange mixte. Nous avons ensuite étudié les films mixtes de LI et GO. Nous avons montré que l’organisation du LI dépendait de la nature des deux interfaces qui entourent sa monocouche. A basse pression de surface, les feuillets de GO recouvrent partiellement la monocouche de LI adsorbée à la surface de l’eau. La monocouche de LI est dans une phase désordonnée qu’elle soit ou non recouverte par ces feuillets. A haute pression, une partie du liquide ionique migre au-dessus des feuillets de GO. On voit apparaitre une coexistence entre deux structures formées par le LI, une structure monocouche hexagonal 2D et une structure multicouche organisée en un réseau monoclinique. Nous avons ensuite utilisé la radiolyse de surface pour former des AuNPs en contact avec le film organique. La sous-phase utilisée est alors une solution d’ions d’or. Nous montrons qu’il existe deux régimes en fonction de la quantité d’or en sous-phase. Pour une quantité d’ions d’or inférieure à 500 fois celle de molécules de LI déposées en surface, nous observons la formation de AuNPs. Pour une quantité d’or supérieure ou égale à 500 fois la quantité de molécules de liquide ionique, la formation de AuNPs n’a lieu qu’à des pressions de surface inférieures à celle du collapse du film . Au-dessus de cette pression de surface, on n’observe plus la formation des AuNPs mais l’apparition d’une structure triclinique. Celle-ci résulte de la substitution de l’anion du liquide ionique par l’ion d’or. Enfin nous avons étudié les effets de l’irradiation sur un film mixte de GO-LI déposé sur une solution d’or. Le film adopte alors une combinaison des comportements observés sur les films mixtes LI-GO déposés sur eau et des films purs de LI et d’OG sur solution d’or. A basse pression, on retrouve le comportement structural observé sur eau pure mais la présence de NMP résiduel induit la formation de AuNPs. A haute pression, les molécules de LI ne recouvrent plus les feuillets de GO. On observe l’apparition de la structure triclinique ainsi que de AuNPs toujours attribuées à la présence du NMP résiduelSupercapacitors based on ionic liquid (IL) as electrolyte and graphene as electrode are promising devices. They have a large number of charge-discharge cycles much faster than the current batteries but suffer from low energy storage density. The addition of gold nanoparticles between graphene sheets and IL appears promising to improve their performances. We use the Langmuir film method, a procedure for studying layers and interfaces on a water surface under various physico-chemical conditions, to study the graphene oxide (GO)/IL interface. We use the ionic liquid [C20mim]+[NTf2]- and graphene oxide (capable of forming a stable film on the surface of the water). We use irradiation of the surface by X-rays coupled with the addition of HAuCl4 3H2O gold salt in the sub-phase to form by radiolysis gold nanoparticles under the organic film. The objective of this thesis is to study the formation of the interface between graphene oxide and ionic liquid without and in the presence of gold nanoparticles at the interfaces. In this goal, we use a solvent common to both species: NMP. Then, depositing the film on a sub-phase formed by a solution of gold, we use surface radiolysis by X-rays to form gold nanoparticles in contact with this film. We therefore first studied the influence of the solvent NMP on pure films of ionic liquid and graphene oxide. We have demonstrated the presence of residual NMP in the IL film that influences the formed structures. NMP was shown to be a solvent capable of forming a stable film of graphene oxide at the air/water interface. Thus, the NMP will be considered in the organization of the interfaces for the mixed film. We then studied the mixed films of IL and GO. We showed that the organization of the IL depended on the nature of the two interfaces surrounding its monolayer. At low surface pressure, the GO sheets partially cover the IL monolayer adsorbed to the water surface. IL monolayer is in a disorderly phase whether or not it is covered by GO sheets. At high pressure, part of the IL migrates above the GO sheets. We see a coexistence between two structures formed by the IL, a hexagonal 2D monolayer structure and a multilayer structure organized in a monoclinic network. We then used surface radiolysis to form gold nanoparticles in contact with the organic film. The sub-phase used is then a solution of gold ions. We show that there are two regimes depending on the quantity of gold in the sub-phase. For a quantity of gold ions less than 500 times that of IL molecules deposited on the surface, we observe the formation of gold nanoparticles. For a quantity of gold greater than or equal to 500 times the quantity of molecules of IL, the formation of gold nanoparticles takes place only at surface pressures lower than that of the collapse of the film. Above this surface pressure, we no longer observe the formation of gold nanoparticles but the appearance of a triclinic structure. This results from the substitution of the anion of the IL by the gold ion. Finally, we studied the effects of irradiation on a mixed GO-IL film deposited on a gold solution. The film adopts a combination of the behaviors observed on mixed IL-GO films deposited on water and pure IL and OG films on gold solution. At low pressure, we find the structural behaviour observed on pure water but the presence of residual NMP induces the formation of gold nanoparticles. At high pressure, IL molecules no longer cover GO sheets. We observe the appearance of the triclinic structure as well as gold nanoparticles always attributed to the presence of residual NMP
Chapitres de livres sur le sujet "Surface radiolysis"
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Liu, Yan, Xiaojing Liu, Sijia Du, Jiageng Wang et Hui He. « Multi-Physics Coupling Model for Thermal Hydraulics and Solute Transport in CRUD Deposits ». Dans Springer Proceedings in Physics, 396–411. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1023-6_35.
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AbstractThe porous Chalk River Unidentified Deposit (CRUD) depositions on the fuel cladding have a great impact on the heat transfer and power distribution of the reactor, resulting in a decrease in reactor safety and economy. In current paper, a multi-physics model is developed to simulate thermal hydraulics and boron hideout within the CRUD depositions. Processes including heat transfer, pressure drop, capillary flow, solute transport, chemical reactions and radiolysis reactions are fully coupled. The coolant flows through the capillary tubes in the porous medium and evaporates into steam at the surface of chimneys. The solute diffuses into the porous medium by capillary flow and maintains its chemical equilibrium. Chemistry and thermal hydraulics are coupled by saturation temperature that varies with solute concentrations. The new model can reasonably predict the distributions of temperature, pressure, Darcy velocity and chemical concentrations. This model shows the effect of evaporation at the chimney surface on CRUD temperature and boric acid concentration. In addition, the results show that boron hideout is caused by the accumulation of boric acid and the precipitation of Li2B4O7 at the bottom of CRUD. The influence of morphology parameters such as porosity, thickness, and chimney geometry on heat transfer and solute transport within CRUD depositions is also evaluated.
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Cassidy, T., P. Coll, F. Raulin, R. W. Carlson, R. E. Johnson, M. J. Loeffler, K. P. Hand et R. A. Baragiola. « Radiolysis and Photolysis of Icy Satellite Surfaces : Experiments and Theory ». Dans Satellites of the Outer Solar System, 297–313. New York, NY : Springer New York, 2010. http://dx.doi.org/10.1007/978-1-4419-7439-6_11.
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Gadzhieva, Nushaba. « IR-Spectroscopy of Radiation- Stimulated Processes of Adsorption, Radiolysis, and Hydrogenation on the Surface of Metals in Contact with Hydrocarbons ». Dans Infrared Spectroscopy - Principles, Advances, and Applications. IntechOpen, 2019. http://dx.doi.org/10.5772/intechopen.80431.
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Prasad, P. G. « Contemporary Approaches in the Synthesis and Fabrication of Nanoparticles ». Dans Materials Research Foundations, 24–51. Materials Research Forum LLC, 2024. http://dx.doi.org/10.21741/9781644902974-2.
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Nowadays engineered nanomaterials and nano phases are fabricated through the manipulation of factors during their synthesis. The current chapter encompasses the trends and challenges of the diversified synthetic strategies including the physic chemical and biological techniques. Methods such as solvo-thermal, reduction, microemulsion, microwave-assisted, sonochemical, electrochemical, polyol and radiolytic processes are discussed under chemical approach. The various physical procedures included are milling, high-energy irradiation, ion implantation, laser ablation and spray pyrolysis. The rising trends of green protocols using biological systems like plant extracts, enzymes and microorganisms towards the surface tuning of these are also discussed.
Actes de conférences sur le sujet "Surface radiolysis"
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Ramos Bernal, S., et A. Negrón-Mendoza. « Comparison between the homogeneous and heterogeneous reactions during the radiolysis of aconitic acid ». Dans The 8th Latin American congress on surface science : Surfaces , vacuum, and their applications. AIP, 1996. http://dx.doi.org/10.1063/1.51157.
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Schoenfeld, Michael P., Samim Anghaie et Mohamed S. El-Genk. « Radiolysis Concerns for Water Shielding in Fission Surface Power Applications ». Dans 008. AIP, 2008. http://dx.doi.org/10.1063/1.2844986.
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Kuznetsov, M., R. Redlinger, W. Breitung, J. Grune, K. Sempert et A. Friedrich. « Experimental and Numerical Simulation of Radiolysis Gas Detonations and Mechanical Response of BWR Exhaust Pipes ». Dans 18th International Conference on Nuclear Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/icone18-29697.
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Radiolysis gas (2H2+O2) can accumulate in BWR steam piping in case of steam condensation. An ensuing detonation of the radiolysis gas is the likeliest cause of a pipe and/or valve damage. In the current work we investigate a typical BWR exhaust pipe, which connects the high pressure steam piping with the ambient atmosphere, under the following “worst case” scenario: (a) accumulation of radiolysis gas in an exhaust pipe, (b) fast valve opening to the high pressure system with steam at 70 bar, and (c) adiabatic pressurization of the radiolysis gas by the steam. Taking into account a water surface level of 6 m from the open end this leads to an equilibrium state of 20 bar pressure and 602 K temperature for the pressurized radiolysis gas. The main purpose of the current work was an experimental and numerical evaluation of the maximum pressure load and the integrity of the BWR exhaust pipe in case of a detonation of the pressurized radiolysis gas.
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Domae, Masafumi, Hirotaka Kawamura et Taku Ohira. « Development of Alternative Reductant Application in PWR Primary Systems ». Dans 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75551.
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In primary coolant of pressurized water reactors (PWRs), high concentration dissolved hydrogen (DH) has been added, to prevent generation of oxidizing species through radiolysis of coolant. Recently, number of ageing plants is increasing and utilities are concerned about primary water stress corrosion cracking (PWSCC). Although mechanism of PWSCC is not fully clarified, some researchers consider that occurrence of PWSCC and crack propagation rate are affected by DH concentration. The authors consider that one of possible mitigation methods toward PWSCC is use of alternative reductant for hydrogen. From the radiation chemical aspect, aliphatic alcohols are typical scavengers of oxidizing radical generated through the radiolysis of water. The aliphatic alcohols are promising candidates of the alternative reductant. In the present work, possible alternatives of hydrogen were screened, and methanol was selected as the best candidate. Corrosion tests of type 304 stainless steels were carried out at 320°C in two conditions: (1) DH 1.5 ppm (part per million) and (2) methanol 2.9 ppm. Under two conditions, electrochemical corrosion potential was measured during the immersion tests. After the immersion tests, surface morphology of the stainless steel specimens was observed by scanning probe microscope. Major component of oxide film was analyzed by X-ray diffraction. From comparison of the test results, it is concluded that addition of methanol 2.9 ppm has almost the same effect as addition of DH 1.5 ppm.
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Yang, Bo, He-xi Wu et Yi-bao Liu. « Simulation and Analysis : The Dose Distribution of KBS-3 Spent Nuclear Fuel Canister by MCNP ». Dans 18th International Conference on Nuclear Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/icone18-29058.
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With the sustained and rapid development of the nuclear power plants, the spent fuel which is produced by the nuclear power plants will be rapidly rising. Spent fuel is High-level radioactive waste and should be disposed safely, which is important for the environment of land, public safety and health of the nuclear industry, the major issues of sustainable development and it is also necessary part for the nuclear industry activities. It is important to study and resolve the high-level radioactive waste repository problem. Spent nuclear fuel is an important component in the radioactive waste, The KBS-3 canister for geological disposal of spent nuclear fuel in Sweden consists of a ductile cast iron insert and a copper shielding. The ductile cast iron insert provides the mechanical strength whereas the copper protects the canister from corrosion. The canister inserts material were referred to as I24, I25 and I26, Spent nuclear fuel make the repository in high radiant intensity. The radiation analysis of canister insert is important in canister transport, the dose analysis of repository and groundwater radiolysis. Groundwater radiolysis, which produces oxidants (H2O2 and O2), will break the deep repository for spent nuclear fuel. The dose distribution of canister surface with different kinds of canister inserts (I24, I25 and I26) is calculated by MCNP (Ref. 1). Analysing the calculation results, we offer a reference for selecting canister inserts material.
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Enivweru, Doctor, Qingyu Wang, Abiodun Ayodeji et Ayouba Moussa Hassane. « A Study on the Onset of Secondary Hydriding in Defective Zr-2 Fuel for Boiling Water Reactors ». Dans ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-73284.
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Abstract One of the most common threats to the integrity of reactor fuel cladding is the geometric imperfections such as the missing pellet surface (MPS) that produces a remarkable surge in the local fuel-clad gap. The cooling water could occupy this gap leading to secondary hydriding (SH) and hydrogen embrittlement. Most studies on this subject have identified extensive radiolysis in boiling water reactors (BWRs) to be responsible for hydrogen evolution during accident conditions. However, the quantitative determination of hydrogen and how it affects zircaloy-2 during normal reactor operation has not been given adequate attention. To bridge this gap and to better predict the onset of cladding failure, this study investigates secondary hydriding and its characteristic phenomenon in a fuel cladded with zircaloy-2. Multiphysics model is used to model diffusion of heat and hydrogen, then the effect of an intermediary porous/non-protective oxide layer and the impact of dose rate from different types of radiation are studied. The contributions of the source term due to radiolysis of neutrons (n), gamma (γ), alpha (α) and beta (β) radiations are also considered. Results showed that neutrons, having a maximum dose rate of 39.9 kGy/s accounts for over 99% of ZrH precipitation in a UO2 fuel with MPS. The effect of oxide (ZrO2) thickness in SH, and the derivative of oxide thickness are also discussed.
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Quin˜ones, Javier, Juan Merino, Esther Cera, Jordi Bruno, Joaquin Cobos et Aurora Marti´nez-Esparza. « Radiolytic Modelling Intercomparison Exercise : Influence of Alpha Radiation on Spent Fuel Alteration Process ». Dans ASME 2003 9th International Conference on Radioactive Waste Management and Environmental Remediation. ASMEDC, 2003. http://dx.doi.org/10.1115/icem2003-4574.
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Radiolytic models have been usually considered useful tools for studying the behaviour of complex chemical systems under the presence of a radiation field. However, they still don’t have a wider acceptance due to limited availability of kinetic data, difficulty to handle heterogeneous systems, and a lack of model validation. We carry out an intercomparison exercise between two kinetic codes, “Chemsimul” and “Maksima”. The objective of the work is to model the influence of an alpha radiation field in the spent fuel alteration process under repository conditions. The experimental system to be modelled is the dissolution of UO2 α-doped pellets under initial anoxic conditions. These experiments have been carried out under well-controlled conditions, and good quality data are available to us for this purpose. The uranium concentration in solution will be predicted by considering the presence of an α-radiation field and its influence due to radiolysis of water on the pellet surface oxidation and subsequent dissolution. In this paper, a kinetic model for the alpha doped pellet under these conditions is presented. Both codes use the same initial fixed parameters in order to reproduce the pellet alteration process: system geometry, chemical composition of the solution, physicochemical characteristics of the solute and the oxidation conditions of the pellet surface (expressed in terms of U(VI)/U(IV) ratio). The last one is the key parameter in the model for simulating the initial quick dissolution process. The differences in the input data are related to intrinsic restrictions of each code. A review of the differences and the capacities of both codes is also included. The predictions obtained using the two codes are compared and the results obtained are in good agreement, having a small difference related to the way of solving the differential equations by each code. However, this difference is not considered to be of significance when comparing modelled and experimental data, leading to the conclusion that both codes can confidently be used in the radiolytic modelling of this kind of systems.
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Dobrevski, Ivan D., et Neli N. Zaharieva. « The Main Changes and Consequences by Burnup Extensions in PWRs : Some Recommendations for Negative Plant Performance Issue Limitations ». Dans 16th International Conference on Nuclear Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/icone16-48099.
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The higher duty cores are always attended with the onset of sub-cooled nucleate boiling (SNB) on the fuel cladding surfaces and the initial excess reactivity of core. The impacts of these factors on the chemical environments of the nuclear fuel cladding- and reactor coolant system- surfaces are discussed: The SNB at the cladding surfaces strongly influences the behavior of gases dissolved in cladding water layer phase, causing their stripping out which will favor the creation of oxidizing conditions. It is considered that the creation of oxidizing conditions in the nuclear fuel cladding environment is not a direct boiling consequence but it is a result of the synergic impact of the boiling- and water radiolysis- processes on the Pressurized Water Reactor fuel cladding surface areas. This requires new criteria for corrosion resistance properties of fuel cladding materials. These materials must have high corrosion resistance to oxidizing conditions. If only boric acid as neutron absorber is implemented, the critical boron concentration in coolant increases significantly when implementing an extended fuel cycle. This effect can be limited through application of 10B enriched boric acid or by application of such solid burnable absorbers as Gd2O3 integrated in UO2 fuel. Some recommendations to address negative plant performance issues are given in addition to the results of these investigations.
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Joe, Hyun-Jong, et Barclay G. Jones. « Modeling of Porous Crud Layer Based on Effects of Diffusion and Water Radiolysis on Anomalous Porous Crud Deposition on Fuel Pin Surfaces in PWRs ». Dans 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22602.
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Many studies have been undertaken to understand crud formation on the upper spans of fuel pin clad surfaces, which is called axial offset anomaly (AOA), is observed in pressurized water reactors (PWR) as a result of sub-cooled nucleate boiling. Separately, researchers have considered the effect of water radiolysis in the primary coolant of PWR. This study examines the effects of radiolysis of liquid water, which aggressively participate in general cladding corrosion and solutes within the primary coolant system, in the terms of pH, temperature, and Linear Energy Transfer (LET). It also discusses the effect of mass transfer, especially diffusion, on the concentration distribution of the radiolytic products, H2 and O2, in the porous crud layer. Finally it covers the effects of chemical reactions of boric acid (H3BO3), which has a negative impact on the mechanisms of water recombination with hydrogen, lithium hydroxide (LiOH), which has a negative effect on water decomposition, dissolved hydrogen (DH), and some trace impurities.
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Saji, Genn. « A Review of Root Causes of SCC Phenomena in BWR/RBMK : An Overview of Radiation-Induced Long Cell Action Relevant to SCC ». Dans 12th International Conference on Nuclear Engineering. ASMEDC, 2004. http://dx.doi.org/10.1115/icone12-49433.
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In a review of recent occurrences of Stress Corrosion Cracking (SCC) in Japanese Boiling Water Reactors (BWRs) and Russian High Power Channel-type Reactors (RBMKs), the author proposes a hypothetical mechanism which states; ‘radiation-induced ‘long cell action’ causing electrolytic corrosion.’ This article provides the currently available technical bases for the proposed mechanism which was introduced in a companion paper also presented at this conference [1]. There is some experimental evidence indicating that long cell action may not be negligible in nuclear reactor environments, when induced by the radiolysis of water. There are also some surprising similarities between SCC in the reactor systems and the basic mechanism of underground corrosion by long cell action. In this mechanism, the ‘long cell action’ is induced by a difference in availability of oxygen inside the soil. Conduction of electrons through an electric conductor over a long distance plays a significant role as they are released by dissolution of metallic ions and sucked up from the metal surface.
Rapports d'organisations sur le sujet "Surface radiolysis"
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Sutton, Mark. Level 4 Milestone (M4) : M41UF033201 - Review of Radiolysis of Brines on the Surface of a Waste Package. Office of Scientific and Technical Information (OSTI), août 2011. http://dx.doi.org/10.2172/1113495.
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Gray, W. J. Effect of surface oxidation, alpha radiolysis, and salt brine composition on spent fuel and UO/sub 2/ leaching performance : Salt Repository Project. Office of Scientific and Technical Information (OSTI), juin 1988. http://dx.doi.org/10.2172/6783908.
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