Academic literature on the topic 'Noble gas diffusion'

Heat transfer in the solid Earth drives processes that modify temperatures, leaving behind a clear signature that we can measure using noble gas thermochronology. This allows us to record the thermal histories of rocks and obtain the timing, rate, and magnitude of phenomena such as erosion, deformation, and fluid flow. This is done by measuring the net balance between the accumulation of noble gas atoms from radioactive decay and their loss by temperature-activated diffusion in mineral grains. Together with knowledge about noble gas diffusion in common minerals, we can then use inverse models of this accumulation–diffusion balance to recover thermal histories. This approach is now a mainstream method by which to study geodynamics and Earth evolution.

The present work involves in determining isotropic and effective pair potential energy of binary gas mixtures of Kr–Xe , Kr–C2H6 , Xe–C2H6 , Kr–C3H8 , and Xe–C3H8 from thermophysical properties consisting of viscosity and second virial coefficients through inversion method. Typically, the calculated intermolecular potential energy of Kr–Xe system has compared with HFD model potential reported in literature. A desirable harmony between our model potential and HFD model has been obtained. In order to assess the potential energies obtained, transport properties including viscosity, diffusion, thermal diffusion factor, and thermal conductivity of aforementioned mixtures were predicted using the calculated models potential. The deviation percentage of the calculated viscosity and thermal conductivity of above-mentioned mixtures from the literature values are, respectively, within ±2%, ±3%.

Molecular dynamics is a popular method to observe the movement of interacting molecules. In this study molecular dynamics method was used to observe the phenomenon of iron corrosion and analyze effect of noble gases as a corrosion inhibitor for iron in liquid metal PbBi. Physical quantities are evaluated from the results of this study including: Mean Square Displacement (MSD), the diffusion coefficient, and for the crystal structure is visualized using Ovito program. The ron is placed in the middle high temperature liquid PbBi, the noble gases is injected into the liquid metal. Based on the three kinds of the noble gases (helium, neon, and argon) thhat injected into the molten metal PbBi, it obtained that Argon is the most effective in inhibiting the corrosion of iron. Argon is able to reduce the corrosion rate of 80.29% iron for temperature of 1023K. One reason to use the noble gas because these gases are difficult to react with other elements. Keywords: Molecular Dynamics, Corrosion in Liquid metals, Nobel Gases, Inhibitors

Ancient rocks have survived plate tectonic recycling for billions of years, but key questions remain about how and when they were exhumed to the surface. Constraining exhumation histories over long timescales is a challenge because much of the rock record has been lost to erosion. Argon and helium noble gas thermochronology can reconstruct deep-time <350 °C thermal histories by using the distinct temperature sensitivities of minerals such as feldspar, zircon, and apatite, while exploiting grain size and radiation damage effects on diffusion kinetics. Resolution of unique time–temperature paths over long timescales requires multiple chronometers, appropriate kinetic models, and inverse simulation techniques to fully explore and constrain possible solutions. Results suggest that surface histories of ancient continental interiors are far from uninteresting and may merely be misunderstood.

Le réchauffement climatique est lié aux augmentations des concentrations de gaz à effet de serre dans l'atmosphère terrestre et en particulier aux émissions anthropiques de CO₂. La séquestration géologique a la capacité et la longévité potentielles pour diminuer de façon significative les émissions anthropiques de CO₂. Cette séquestration à grande profondeur induit des risques de fuite des réservoirs géologiques. Parmi les scénarios de fuite envisagés, celui d'une fuite diffuse est le plus inquiétant puisque sans surveillance, cette fuite pourrait perdurer et entrainer des séquelles sur l'environnement ainsi que des risques pour les populations. Des outils et protocoles de surveillance doivent donc être mis au point pour la surveillance en proche surface. Ce travail de thèse s'inscrit dans le cadre de cette problématique. Il a pour objectif la caractérisation, la quantification et la modélisation du transport et des interactions du CO₂ dans une zone non saturée carbonatée. Ce travail a suivi une approche expérimentale sur un site pilote naturel à Saint-Emilion (Gironde, France), avec la réalisation de fuites diffuses en ZNS carbonatée. Cette étude aborde plusieurs thématiques: la description et l'instrumentation du site pilote naturel ; la caractérisation physico-chimique de l'hétérogénéité du réservoir carbonaté ; l'étude du fonctionnement naturel de la ZNS carbonatée et en particulier la mise en place d'une ligne de base des concentrations en CO₂ ; la caractérisation de l'extension des panaches de gaz suite à des expériences de fuite diffuse dans la ZNS carbonatée et l'étude par simulation numérique des interactions gaz-eau-roche lors d'une fuite diffuse de CO₂ dans une ZNS carbonatée. Les résultats de ces travaux montrent l'importance de la caractérisation de l'hétérogénéité du réservoir carbonaté ainsi que des techniques d'échantillonnage et d'analyse des différentes phases en présence. L'établissement de la ligne de base a une importance particulière pour permettre de distinguer les variations naturelles de celles induites par une fuite diffuse de CO₂ dans la ZNS carbonatée. Les modes de transport du CO₂ vont évoluer en fonction des paramètres physico-chimiques. Ce transport se fait par advection et/ou par diffusion. L'utilisation de gaz inertes au niveau du site de séquestration géologique est très importante puisque la détection de ces traceurs permettrait de prédire les arrivées de panaches de CO₂ en proche surface. Par ailleurs, les interactions chimiques doivent être prises en compte dans les modèles de transport afin de pouvoir définir les facteurs de retard et l'impact d'une fuite diffuse de CO₂ sur une ZNS carbonatée
Global warming is related to atmospheric greenhouse gas concentration increase and especially anthropogenic CO₂ emissions. Geologic sequestration has the potential capacity and the longevity to significantly diminish anthropogenic CO₂ emissions. This sequestration in deep geological formation induces leakage risks from the geological reservoir. Several leakage scenarios have been imagined. Since it could continue for a long period, inducing environmental issues and risks for human, the scenario of a diffusive leakage is the most worrying. Thus, monitoring tools and protocols are needed to set up a near-surface monitoring plan. The present thesis deals with this problematic. The aims are the characterisation, the quantification and the modelling of transport and interactions of CO₂ in a carbonate unsaturated zone. This was achieved following an experimental approach on a natural pilot site in Saint-Emilion (Gironde, France), where diffusive gas leakage experiments were set up in a carbonate unsaturated zone. Different aspects were investigated during the study: natural pilot site description and instrumentation; the physical and chemical characterisation of carbonate reservoir heterogeneity; the natural functioning of the carbonate unsaturated zone and especially the set-up of a CO₂ concentrations baseline; the characterisation of gas plume extension following induced diffusive leakage in the carbonate unsaturated zone and the study of gas-water-rock interactions during a CO₂ diffusive leakage in a carbonate unsaturated zone through numerical simulations. The results show the importance of the carbonate reservoir heterogeneity characterisation as well as the sampling and analysing methods for the different phases. The baseline set-up is of main interest since it allows discrimination between the induced and the natural CO₂ concentrations variations. The transfer of CO₂ in a carbonate unsaturated zone is varying in function of physical and chemical properties. This transfer is done by diffusion and/or advection. Because the detection of the noble gases allows the prediction of CO₂ plume arrival, the use of tracers in the sequestration site is of main importance. The chemical interactions have to be taken under account in transport models in order to predict delay factors and the impact of a CO₂ leakage in a carbonate unsaturated zone

Water is of central importance in the transport of solutes, whether by diffusion or mass flow, and whether in soils or plants (Lösch 1995). It is also extremely important for the biota that live in the soil (Parr et al. 1981). Water is an unusual component of the environment, because its structure suggests it should be a gas at normal temperatures rather than a liquid, and it is the only common compound in the biosphere that occurs to a significant extent in the vapour, liquid and solid phases. We begin this chapter with a very brief statement of the thermodynamic approach to the study of water, which defines the water potential. Without an understanding of chemical potentials, it is difficult to deal with the relationships of ions and water in the soil and the plant. Therefore, in this chapter we give an introduction to this subject with special reference to water, which we then take further in chapters 4 and 5. A clear exposition of this is given in Nobel (1991). The concept of chemical potential is fundamental. It is a measure of the energy state of a particular compound in a particular system, and hence of the ability of a unit amount of the compound to perform work and thereby cause change. In particular, the difference in potential at different points in a system gives a measure of the tendency of the component to move from the region with the high potential to the region with the low potential. A component of a system can have various forms of potential energy in this sense, all of which contribute to the total chemical potential. Here, we exclude chemical reaction energy and kinetic energy. The main forms of energy that contribute to the chemical potential of a specified compound or material are due to its concentration (which may release energy on dilution), to its compression (which may perform work on expansion), to its position in an electrical field (which may release energy if the component is electrically charged and moves within the field), and to its position in the gravitational field (which may release energy as the component moves downwards).

The catalytic converter is an important device for the emission control from spark-ignition engines. Several concurrent physical/chemical processes such as convective heat transfer, gas phase chemical reactions, surface reactions, flow oscillations, water vapor condensation and diffusion mechanisms add complexity to modeling of flows inside catalytic converters. Under cold-start conditions, the fact that catalytic converters do not become operational during the initial operation allows a significant fraction of the overall pollutants to be emitted. In the present study, these complex transient phenomena have been examined using a previously validated numerical model.1 The numerical results suggest new material-dependent designs to improve both the transient conversion characteristics and the steady state conversion efficiency of catalytic converters. Moreover, from our model calculations, we have observed that for a given amount of the noble metal catalysts the light-off time and the monolith temperature are greatly affected by the noble-metal distribution along the honeycomb walls of a monolith. The results of the numerical simulations indicate that the light-off time is shortened by approximately 35% for CO, H2 and C3H6 when replacing a traditional homogeneous noble metal distribution by a simple, step-function distribution.2 The emissions of CO, H2 and C3H6 from the exhaust gas are, therefore, reduced without increasing the cost of noble metal catalysts used in converters. In order to avoid further deterioration of catalysts due to the thermal effects, an optimum noble metal distribution needs to be investigated with the understanding that the optimum noble metal distribution proposed has to be practical for the manufacturing. Since the main source of the exhaust emissions is generated during the cold-start period of the converter operation, the reduction of emissions shown in our model calculations is quite substantial.

Abstract In a postulated accident of fuel pin failure of sodium cooled fast reactor, a fission product cesium will be released from the failed pin as an aerosol such as cesium iodide and/or cesium oxide together with a fission product noble gas such as xenon and krypton. As the result, the xenon and krypton released with cesium aerosol into the sodium coolant as bubbles have an influence on the removal of cesium aerosol by the sodium pool in a period of bubble rising to the pool surface. In this study, cesium aerosol removal behavior due to inertial deposition, sedimentation and diffusion from a noble gas bubble rising through liquid sodium pool was analyzed by constructing a computer program which deals with the expansion and the deformation of the bubble together with the aerosol absorption. In the analysis, initial bubble diameter, sodium pool depth and temperature, aerosol particle diameter and density, initial aerosol concentration in the bubble were changed as parameter, and the sensitivities of these parameters on decontamination factor (DF) of cesium aerosol were investigated. From the results, it was concluded that the initial bubble diameter was most sensitive parameter to the DF of cesium aerosol in the rising bubble due to the inertial deposition. It was found that the sodium pool depth, the aerosol particle diameter and density have also important effect on the DF of cesium aerosol, but the sodium temperature has a marginal effect on the DF. To meet these results, the experiments for the investigation of cesium aerosol absorption behavior from rising noble gas bubble through sodium pool are under planning to validate the results for the sensitivities of above-mentioned parameters on the DF of cesium aerosol in the analysis.

PCCSAC-3D is a code originally developed for AC600 containment thermo-hydraulic analysis. Its validated capabilities include simulating the behaviors of steam-air mixture and liquid water under the unique conditions of an AC600/AP1000 containment after a DBA. The film-tracking model applied gives it the ability to simulate the liquid film both outside and inside the steel containment. Refined with some new models, the new version of the code, named PCCSAP-3D, can cover hydrogen behavior, fission products behavior (in the form of gas and aerosol) and iodine behavior. In the module of noncondensable gas, diffusion of up to 11 species are taken into consideration. A user-definable recombiner/ignitor model is developed to accommodate different types of hydrogen recombiners and ignitors. Given the source term as a boundary condition, the fission products model would be able to track up to 64 radio-isotopes after a LOCA. The leakage and spontaneous decay is accounted for all of these nuclides. Besides, the noble gases, gaseous iodine and fission product aerosols are treated separately. There is no removal mechanism of noble gases. Whereas removal mechanisms of radio-aerosols considered include spray, gravitational sedimentation, diffusio-phoresis and thermo-phoresis. A simple model for gaseous iodine comprises organic iodine and elemental iodine, in which the effects of spray and liquid adsorption are treated integrally. To evaluate the radioactivity consequences of a certain accident, a radioactivity calculation model is brought out to convert the molar concentration or mass concentration of radioactive material into radioactivity concentration. The new version of PCCSAP-3D code with models aforementioned is preliminarily validated by comparing the simulation results with safety analysis results reported in AP1000 Design Control Document. The accident scenario is set as a design basic LOCA with core melt.