scholarly journals The Role Of Chemical Reaction In Waste-Form Performance

1987 ◽  
Vol 112 ◽  
Author(s):  
P. L. Chambré ◽  
C. H. Kang ◽  
W. W.-L. Lee ◽  
T. H. Pigford
Keyword(s):  
Mass Transfer ◽  
Steady State ◽  
Dissolution Rate ◽  
Chemical Reaction ◽  
Borosilicate Glass ◽  
Reaction Rate ◽  
Waste Form ◽  
Spent Fuel ◽  
Wide Range ◽  
Chemical Reaction Rate

AbstractThe dissolution rate of waste solids in a geologic repository is a complex function of waste form geometry, chemical reaction rate, exterior flow field, and chemical environment. We present here an analysis to determine the steady-state mass transfer rate, over the entire range of flow conditions relevant to geologic disposal of nuclear waste. The equations for steady-state mass transfer with a chemical-reaction-rate boundary condition are solved by three different mathematical techniques which supplement each other. This theory is illustrated with laboratory leach data for borosilicate-glass and a spherical spent-fuel waste form under typical repository conditions. For borosilicate glass waste in the temperature range of 57°C to 250°C, dissolution rate in a repository is determined for a wide range of chemical reaction rates and for Peclet numbers from zero to well over 100, far beyond any Peclet values expected in a repository. Spent-fuel dissolution in a repository is also investigated, based on the limited leach data now available.

scholarly journals A Study of Steady Buoyancy-Driven Dissipative Micropolar Free Convection Heat and Mass Transfer in a Darcian Porous Regime with Chemical Reaction

2007 ◽  
Vol 12 (2) ◽  
pp. 157-180 ◽  
Author(s):  
O. Anwar Bég ◽  
R. Bhargava ◽  
S. Rawat ◽  
H. S. Takhar ◽  
Tasweer A. Bég
Keyword(s):  
Mass Transfer ◽  
Velocity Field ◽  
Heat And Mass Transfer ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Near Field ◽  
Packed Bed ◽  
Darcy Number ◽  
Reaction Model ◽  
Chemical Reaction Rate

In the present paper we examine the steady double-diffusive free convective heat and mass transfer of a chemically-reacting micropolar fluid flowing through a Darcian porous regime adjacent to a vertical stretching plane. Viscous dissipation effects are included in the energy equation. Assuming incompressible, micro-isotropic fluid behaviour the transport equations are formulated in a two-dimensional coordinate system (x, y) using boundary-layer theory. The influence of the bulk porous medium retardation is modeled as a drag force term in the translational momentum equation. Transformations render the conservation equations into dimensionless form in terms of a single independent variable, η, transverse to the stretching surface. A simplified first order homogenous reaction model is also used to simulate chemical reaction in the flow. Using the finite element method solutions are generated for the angular velocity field, translational velocity field, temperature and species transfer fields. The effects of buoyancy, porous drag and chemical reaction rate are studied. Chemical reaction is shown to decelerate the flow and also micro-rotation values, in particular near the wall. Mass transfer is also decreased with increasing chemical reaction rate. Increasing Darcy number is shown to accelerate the flow. Applications of the study include cooling of electronic circuits, packed-bed chemical reactors and also the near field flows in radioactive waste geo-repositories.

A TRAJECTORY-FOLLOWING METHOD FOR SOLVING THE STEADY STATE OF CHEMICAL REACTION RATE EQUATIONS

2009 ◽  
Vol 08 (supp01) ◽  
pp. 1025-1044 ◽  
Author(s):  
XIN-LONG LUO
Keyword(s):  
Steady State ◽  
Convergence Analysis ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Computing Time ◽  
Rate Equations ◽  
Time Step ◽  
Euler Formula ◽  
Chemical Reaction Rate ◽  
Trajectory Following

This article gives a trajectory-following method for the steady state of chemical reaction rate equations. In order to avoid wasting unnecessary computing time during the steady-state phase and get roughly accurate solutions during the transient-state phase, this method is realized via adopting the semi-implicit Euler formula as the stepping direction and adaptively adjusting the time-step size by an analogous trust-region technique. Under some standard assumptions, its global convergence analysis and local superlinear convergence analysis are also given. Finally, some numerical experiments of this method, in comparison with the traditional optimization methods and ordinary differential equation methods, are reported. The numerical results show that this trajectory-following method is a promising solution for this class of problems.

Diffusion and Mixing in Microchannel Analyzed by the Luminol Chemiluminescence

2013 ◽  
Author(s):  
Ruru Matsuo ◽  
Ryosuke Matsumoto
Keyword(s):  
Numerical Simulation ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Mixing Layer ◽  
Fluorescence Technique ◽  
Chemiluminescence Intensity ◽  
Luminol Chemiluminescence ◽  
Chemical Reaction Rate ◽  
Pdms Chip ◽  
Reaction Profile

This study focused on the diffusion and mixing phenomena investigated by using luminol chemiluminescence (CL) to estimate the local chemical reaction rate in the T-junction microchannel. Generally, the degree of mixing in microchannel is calculated by the deviation of the obtained concentration profiles from the uniform concentration profile by using fluorescence technique. Thus, the degree of mixing is a macroscopic estimate for the whole microchannel, which is inappropriate for understanding the diffusion and mixing phenomena in the mixing layer. In this study, the luminol CL reaction is applied to visualize the local chemical reaction and to estimate the local diffusion and mixing phenomena at an interface between two liquids in microchannel. Luminol emits blue chemiluminescence when it reacts with the hydrogen peroxide at the mixing layer. Experiments were carried out on the T-junction microchannel with 200 microns in width and 50 microns in depth casted in the PDMS chip. The chemiluminescence intensity profiles clearly show the mixing layer at an interface between two liquids. The experimental results are compared with the results of numerical simulation that involves solving the mass transport equations including the chemical reaction term. By calibrating CL intensity to the chemical reaction rate estimated by the numerical simulation, the local chemical reaction profile can be quantitatively estimated from the CL intensity profile.

ChemInform Abstract: ENHANCEMENT OF A CHEMICAL REACTION RATE BY PROPER ORIENTATION OF REACTING MOLECULES IN THE SOLID STATE

1975 ◽  
Vol 6 (46) ◽  
pp. no-no
Author(s):  
CHAIM N. SUKENIK ◽  
JOSE A. P. BONAPACE ◽  
NEIL S. MANDEL ◽  
ROBERT G. BERGMAN ◽  
PUI-YAN LAU ◽  
...  
Keyword(s):  
Solid State ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Chemical Reaction Rate ◽  
Proper Orientation
Sign in / Sign up

Export Citation Format

Share Document