Fundamental Study on Transport Model for Radionuclides under Unsaturated Condition around Near-Surface Underground

MRS Advances ◽  
2020 ◽  
Vol 5 (5-6) ◽  
pp. 223-232
Author(s):  
Takenori Ozutsumi ◽  
Masayuki Kogure ◽  
Yuichi Niibori ◽  
Taiji Chida
Keyword(s):  
Mass Transfer ◽  
Unsaturated Zone ◽  
Transport Model ◽  
Path Model ◽  
Local Flow ◽  
Near Surface ◽  
One Dimensional ◽  
Retardation Coefficient ◽  
The One ◽  
Unsaturated Condition

ABSTRACTThe low-level nuclear wastes such as decontamination waste from Fukushima are disposed in near-surface underground, where the intermittent recharge of rain and groundwater causes spatial distribution of water content. Therefore, pores of soils are not filled with water, that is, an unsaturated zone will be formed. In such a condition, since the water flow path are detoured by clogged gas in pores of soil in the unsaturated zone, the migration path of radionuclide would be different from the saturated zone. So far, the one-dimensional advection-dispersion equation (ADE) model has been widely used in order to explain experimental results under an unsaturated condition. However, the detouring of local flow-paths remarkably affects the mass transfer. The one-dimensional ADE evaluates such a detouring effect by using Peclet number and retardation coefficient as fitting parameters. In other words, the one-dimensional ADE model is difficult to explain mass transfer under an unsaturated condition. Therefore, the purpose of this study is explaining such complicated transport of radionuclides using a multi-path model based on phenomena in underground. The proposed multi-path model considering both water saturation and permeability distributions showed good agreement with the experimental data under an unsaturated condition.

scholarly journals Parameterization of middle atmospheric water vapor photochemistry for high-altitude NWP and data assimilation

2008 ◽  
Vol 8 (4) ◽  
pp. 13999-14032 ◽  
Author(s):  
J. P. McCormack ◽  
K. W. Hoppel ◽  
D. E. Siskind
Keyword(s):  
Water Vapor ◽  
Middle Atmosphere ◽  
Transport Model ◽  
Polar Vortex ◽  
Forecast Model ◽  
Stratospheric Polar Vortex ◽  
One Dimensional ◽  
Sources And Sinks ◽  
Free Running ◽  
The One

Abstract. This report describes CHEM2D-H2O, a new parameterization of H2O photochemical production and loss based on the CHEM2D photochemical-transport model of the middle atmosphere. This parameterization accounts for the altitude, latitude, and seasonal variations in the photochemical sources and sinks of water vapor over the pressure region from 100–0.001 hPa (~16–90 km altitude). A series of free-running NOGAPS-ALPHA forecast model simulations offers a preliminary assessment of CHEM2D-H2O performance over the June 2007 period. Results indicate that the CHEM2D-H2O parameterization improves global 10-day forecasts of upper mesospheric water vapor compared to forecasts using an existing one-dimensional (altitude only) parameterization. Most of the improvement is seen at high winter latitudes where the one-dimensional parameterization specifies photolytic H2O loss year round despite the lack of sunlight in winter. The new CHEM2D-H2O parameterization should provide a better representation of the downwelling of dry mesospheric air into the stratospheric polar vortex in operational analyses that do not assimilate middle atmospheric H2O measurements.

scholarly journals Parameterization of middle atmospheric water vapor photochemistry for high-altitude NWP and data assimilation

2008 ◽  
Vol 8 (24) ◽  
pp. 7519-7532 ◽  
Author(s):  
J. P. McCormack ◽  
K. W. Hoppel ◽  
D. E. Siskind
Keyword(s):  
Water Vapor ◽  
Middle Atmosphere ◽  
Transport Model ◽  
Polar Vortex ◽  
Forecast Model ◽  
Stratospheric Polar Vortex ◽  
One Dimensional ◽  
Sources And Sinks ◽  
Free Running ◽  
The One

Abstract. This paper describes CHEM2D-H2O, a new parameterization of H2O photochemical production and loss based on the CHEM2D photochemical-transport model of the middle atmosphere. This parameterization accounts for the altitude, latitude, and seasonal variations in the photochemical sources and sinks of water vapor over the pressure region from 100–0.001 hPa (~16–90 km altitude). A series of free-running NOGAPS-ALPHA forecast model simulations offers a preliminary assessment of CHEM2D-H2O performance over the June 2007 period. Results indicate that the CHEM2D-H2O parameterization improves global 10-day forecasts of upper mesospheric water vapor compared to forecasts using an existing one-dimensional (altitude only) parameterization. Most of the improvement is seen at high winter latitudes where the one-dimensional parameterization specifies photolytic H2O loss year round despite the lack of sunlight in winter. The new CHEM2D-H2O parameterization should provide a better representation of the downwelling of dry mesospheric air into the stratospheric polar vortex in operational analyses that do not assimilate middle atmospheric H2O measurements.

scholarly journals Modelling and Dynamic Simulation of One-Dimensional Isothermal Axial Dispersion Tubular Reactors with Power Law and Langmuir-Hinshelwood-Hougen Watson Kinetics

2021 ◽  
Vol 8 (2) ◽  
pp. 834-858
Author(s):  
Almoruf Olajide Fasola Williams
Keyword(s):  
Mass Transfer ◽  
Dynamic Response ◽  
Power Law ◽  
Axial Dispersion ◽  
Operating Parameters ◽  
Orthogonal Collocation ◽  
Feed Concentration ◽  
One Dimensional ◽  
Tubular Reactors ◽  
The One

In this paper, the modelling, numerical lumping and simulation of the dynamics of one-dimensional, isothermal axial dispersion tubular reactors for single, irreversible reactions with Power Law (PL) and Langmuir-Hinshelwood-Hougen-Watson (LHHW)-type kinetics are presented. For the PL-type kinetics, first-order and second-order reactions are considered, while Michaelis-Menten and ethylene hydrogenation or enzyme substrate-inhibited reactions are considered for the LHHW-type kinetics. The partial differential equations (PDEs) developed for the one-dimensional, isothermal axial dispersion tubular reactors with both the PL and LHHW-type kinetics are lumped to ordinary differential equations (ODEs) using the global orthogonal collocation technique. For the nominal design/operating parameters considered, using only 3 or 4 collocation points, are found to adequately simulate the dynamic response of the systems. On the other hand, simulations over a range of the design/operating parameters require between 5 to 7 collocations points for better results, especially as the Peclet number for mass transfer is increased from the nominal value to 100. The orthogonal collocation models are used to carry out parametric studies of the dynamic response behaviours of the one-dimensional, isothermal axial dispersion tubular reactors for the four reaction kinetics. For each of the four types of reaction kinetics considered, graphical plots are presented to show the effects of the inlet feed concentration, Peclet number for mass transfer and the Damköhler number on the reactor exit concentration dynamics to step-change in the inlet feed concentration. The internal dynamics of the linear (or linearized) systems are examined by computing the eigenvalues of the linear (or linearized) lumped orthogonal collocation models. The relatively small order of the lumped orthogonal collocation dynamic models make them attractive and useful for dynamic resilience analysis and control system analysis/design studies.

Evaluation of Retardation Effect of Cesium Ions Through Groundwater Unsaturated Zone

2016 ◽  
Author(s):  
Takenori Ozutsumi ◽  
Yuichi Niibori ◽  
Taiji Chida
Keyword(s):  
Unsaturated Zone ◽  
Nuclear Power ◽  
Experimental Results ◽  
Retardation Effect ◽  
Silica Sand ◽  
Flow Paths ◽  
Near Surface ◽  
Advection Dispersion ◽  
Unsaturated Condition ◽  
Eastern Japan

Around near-surface underground, an unsaturated zone is formed in such porous layer composed of mainly silicate and silica sand. In the unsaturated zone in which pores are not completely filled with groundwater but also air, the migration of RNs is influenced by the presence of air phase. So far, though many studies have been reported about the unsaturated zone, little studies on the relation of the unsaturated zone and the migration of RNs have been carried out. In this study, the change of the migration of tracer ions in the unsaturated zone was examined by using a bed column, and analyzed by applying advection dispersion equation to the experimental results. As tracer ions, cesium (Cs) and strontium (Sr) were chosen in this study. These elements are the most important elements for the decontamination of Eastern Japan area caused by Fukushima the Daiichi Nuclear Power Plant accident. The experimental results showed the facilitation of the migration of tracer ions in the unsaturated zone. This causes the decrease in the sorption of tracer ions due to the inhibition of air phase. That is, the increase in the retardation effect by the clogging with air phase in flow paths was not remarkable. In the assessment of RNs migration under the unsaturated condition, these competing effects should be reflected adequately.

The Dissipation Function-Based Efficiency for Turbomachinery—Part I: The Efficiency of a Cooled Turbine Row1

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Chong M. Cha
Keyword(s):  
Mass Transfer ◽  
Dissipation Function ◽  
One Dimensional ◽  
Specific Heats ◽  
Gas Streams ◽  
Blade Row ◽  
The One ◽  
Turbine Airfoils ◽  
The Impact ◽  
Mixing Problem

The effect of coolant addition or “mixing loss” on aerodynamic performance is formulated for the turbine, where mixing takes place between gas streams of different compositions as well as static temperatures. To do this, a second-law efficiency measure is applied to a generalization of the one-dimensional mixing problem between a main gas stream and a single coolant feed, first introduced and studied by Hartsel (1972, “Prediction of Effects of Mass-Transfer Cooling on the Blade-Row Efficiency of Turbine Airfoils,” AIAA Paper No. 1972-11) for the turbine application. Hartsel's 1972 model for mass transfer cooling loss still remains the standard for estimating mixing loss in today's turbines. The present generalization includes losses due to the additional contributions of “compositional mixing” (mixing between unlike compositions of the main and coolant streams) as well as the effect of chemical reaction between the two streams. Scaling of the present dissipation function-based loss model to the mainstream Mach number and relative cooling massflow and static temperature is given. Limitations of the constant specific heats assumptions and the impact of fuel-to-air ratio are also quantified.

A Study of Experimental and Improved Absorption Model for the Spray Towers of Wet Flue Gas Desulfurization

2012 ◽  
Vol 550-553 ◽  
pp. 574-579 ◽  
Author(s):  
Ding Ping Liu ◽  
Hai Long Yu
Keyword(s):  
Mass Transfer ◽  
Flue Gas ◽  
Power Plants ◽  
Gas Flow ◽  
Film Theory ◽  
Flue Gas Desulfurization ◽  
Transfer Model ◽  
Actual Process ◽  
One Dimensional ◽  
The One

The wet flue gas desulfurization has been the most widely used in the coal-fired power plants because of high SO2removal efficiency, reliability and low utility consumption. A mathematical model of limestone/gypsum wet flue gas desulfurization (WFGD) system was developed based on the two-film theory of mass-transfer. In the one-dimensional two-film theory , the concentration of SO2in the bulk of the liquid(cAs) is difficult to accurately determine. The authors derive the accurate calculation of the value of cAs on the basis of the one-dimensional mass transfer model, making the model in line with the actual process. The model predictions were verified by experimental data. Experimental investigations of the effects of different operating variables on the SO2removal showed the reasonable process parameters such as the pH value of the liquid phase, droplet size of the spray and the flow rates of liquid and gas. Keep the slurry flow in a 50 ml/min, adjust the flue gas flow changes. Keep the flue gas flow in 5 l/min, adjust the flow slurry changes. The experimental results reveal that the model can describe the processes in this absorber well. Some experimental parameters (temperature, flue gas velocity) are difficult to accurately control, the model can give them fluence on the desulfurization efficiency.

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