Fission gas diffusion in uranium dioxide

1978 ◽  
Vol 364 (1719) ◽  
pp. 473-497 ◽  
Keyword(s):  
Experimental Study ◽  
Chemical Composition ◽  
Diffusion Coefficients ◽  
Gas Diffusion ◽  
Rare Gas ◽  
Ionic Crystals ◽  
Gas Migration ◽  
Fission Gas ◽  
And Migration ◽  
And Diffusion

We present the results of a theoretical investigation of the trapping and migration of the fission gas atoms, Kr and Xe in UO 2 . Our models differ from those previously presented in discussions of rare gas diffusion in ionic crystals. We propose that trapping occurs at vacancy aggregates, and that detrapping into interstitial sites is unimportant; gas migration is effected by the intrinsic mobility of the gas-trap complexes. We suggest that the trapping and diffusion of the two gas atoms occur by different mechanisms, owing to their different sizes. Our results explain many of the observations of the experimental study of Felix & Miekeley and emphasize the importance of the chemical composition of the fuel on gas diffusion coefficients. The contradictions between this work and the earlier studies summarized by Matzke is, we suggest, possibly due to the higher levels of radiation damage which may have been present in the crystals used in the latter work.

scholarly journals An Experimental Study of the Effect of Temperature on Effective Charge Numbers and Diffusion Coefficients of Lignosulfonate.

1992 ◽  
Vol 46 ◽  
pp. 941-948 ◽  
Author(s):  
Anna-Kaisa Kontturi ◽  
Kyösti Kontturi ◽  
Pasi Niinikoski ◽  
Lasse Murtomäki ◽  
Johan Springborg ◽  
...  
Keyword(s):  
Experimental Study ◽  
Diffusion Coefficients ◽  
Effective Charge ◽  
Effect Of Temperature ◽  
And Diffusion

scholarly journals The Influence of Sorption Pressure on Gas Diffusion in Coal Particles: An Experimental Study

Processes ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 219 ◽  
Author(s):  
Yang ◽  
Wang ◽  
Zhang ◽  
Ren
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Gas Diffusion ◽  
Gas Pressure ◽  
Fast Diffusion ◽  
Pore Characteristic ◽  
Coal Particles ◽  
Pore Size Distributions ◽  
Coal Ranks ◽  
And Diffusion

Gas pressure changes during the process of coal mine gas drainage and CBM recovery. It is of great importance to understand the influence of sorption pressure on gas diffusion; however, the topic remains controversial in past studies. In this study, four samples with different coal ranks were collected and diffusion experiments were conducted under different pressures through the adsorption and desorption processes. Three widely used models, i.e., the unipore diffusion (UD) model, the bidisperse diffusion (BD) model and the dispersive diffusion (DD) model, were adopted to compare the applicability and to calculate the diffusion coefficients. Results show that for all coal ranks, the BD model and DD model can match the experimental results better than the UD model. Concerning the fast diffusion coefficient Dae of the BD model, three samples display a decreasing trend with increasing gas pressure while the other sample shows a V-type trend. The slow diffusion coefficient Die of BD model increases with gas pressure for all samples, while the ratio β is an intrinsic character of coal and remains constant. For the DD model, the characteristic rate parameter kΦ does not change sharply and the stretching parameter α increases with gas pressure. Both Dae and Die are in proportion to kΦ, which reflect the diffusion rate of gas in the coal. The impacts of pore characteristic on gas diffusion were also analyzed. Although pore size distributions and specific surface areas are different in the four coal samples, correlations are not apparent between pore characteristic and diffusion coefficients.

Diffusion of Krypton in Cesium and Rubidium Iodide; A Comparison of Results Obtained Following Reactor Irradiation and Ion Bombardment

1970 ◽  
Vol 25 (2) ◽  
pp. 252-256
Author(s):  
Hj. Matzke ◽  
F. Springer
Keyword(s):  
Melting Point ◽  
Diffusion Coefficients ◽  
Ion Bombardment ◽  
Gas Diffusion ◽  
Rare Gas ◽  
Reactor Irradiation ◽  
Rare Gases ◽  
Gas Concentration ◽  
Comparison Of Results ◽  
Empirical Rule

Abstract The present study shows that under suitably chosen conditions, the same results of rare gas diffusion coefficients can be obtained in samples which are reactor irradiated to produce a homo-geneous concentration of rare gas, and in samples that are labeled with rare gas by controlled ion bombardment. In the present study, the diffusion of krypton in Rbl and Csl was found to follow the empirical rule of yielding activation enthalpies in the range (1.4±0.2) x 10-3 Tm eV, with Tm = melting point in °K. Trapping of rare gases (gas-gas or gas-damage interactions) was observed at high gas concentration.

Experimental study on gas diffusion dynamics in fractured coal: A better understanding of gas migration in in-situ coal seam

Energy ◽  
2020 ◽  
Vol 195 ◽  
pp. 117005 ◽  
Author(s):  
Ting Liu ◽  
Baiquan Lin ◽  
Xuehai Fu ◽  
Yabin Gao ◽  
Jia Kong ◽  
...  
Keyword(s):  
Experimental Study ◽  
Coal Seam ◽  
Gas Diffusion ◽  
Gas Migration ◽  
Diffusion Dynamics ◽  
Fractured Coal

scholarly journals The simultaneous determination of air permeability and gas diffusion through ice layers in the field

2007 ◽  
Vol 38 (3) ◽  
pp. 203-210 ◽  
Author(s):  
G. Fortin ◽  
E. van Bochove ◽  
H.G. Jones ◽  
G. Thériault ◽  
M. Bernier
Keyword(s):  
Diffusion Coefficients ◽  
Gas Diffusion ◽  
Air Permeability ◽  
Structural Variations ◽  
Compacted Soil ◽  
Gas Chamber ◽  
And Diffusion ◽  
Sequential Measurements

A coupled air permeameter–gas chamber has been used to measure both the air permeability and diffusion coefficient of an inert gas through natural ice layers. The apparatus was designed to take sequential measurements of both these parameters for the same sample without any intermediate manipulation of the specimen. In avoiding manipulation, errors related to the structural variations between different replicates are eliminated. The apparatus is portable, allowing measurements to be made directly at the study site. The permeability is directly measured in situ by the air permeameter while gas samples used in the diffusion experiments are collected and subsequently analysed at the laboratory. The validation of the apparatus was accomplished by comparing theoretical values for the permeability of beds of spherical beads with known dimensions. Measured permeability values,for different ice samples vary from 0.005 × 10−10 to 12.9 × 10−10 m2. Mean diffusion coefficients ranged from 0.013 to 0.028 cm2 s−1. These values are situated in the range for those found between hard packed snow and loose compacted soil.

PREDICTION OF THE TRANSPORT PROPERTIES OF SF6 WITH O2, CO2, CF4, N2 AND CH4 MIXTURES AT LOW DENSITY BY THE INVERSION METHOD (PART II)

2004 ◽  
Vol 03 (01) ◽  
pp. 69-90 ◽  
Author(s):  
BEHZAD HAGHIGHI ◽  
ALIREZA HASSANI DJAVANMARDI ◽  
MOHAMAD MEHDI PAPARI ◽  
MOHSEN NAJAFI
Keyword(s):  
Potential Energy ◽  
Diffusion Coefficients ◽  
Potential Energy Function ◽  
Model Potential ◽  
Inversion Method ◽  
Low Density ◽  
Initial Model ◽  
Lennard Jones ◽  
Inversion Procedure ◽  
And Diffusion

Viscosity and diffusion coefficients for five equimolar binary gas mixtures of SF 6 with O 2, CO 2, CF 4, N 2 and CH 4 gases are determined from the extended principle of corresponding states of viscosity by the inversion technique. The Lennard–Jones 12-6 (LJ 12-6) potential energy function is used as the initial model potential required by the technique. The obtained interaction potential energies from the inversion procedure reproduce viscosity within 1% and diffusion coefficients within 5%.

scholarly journals Boundary behavior and product-form stationary distributions of jump diffusions in the orthant with state-dependent reflections

2008 ◽  
Vol 40 (02) ◽  
pp. 529-547
Author(s):  
Francisco J. Piera ◽  
Ravi R. Mazumdar ◽  
Fabrice M. Guillemin
Keyword(s):  
Random Fields ◽  
Diffusion Coefficients ◽  
Boundary Behavior ◽  
Stationary Regime ◽  
Product Form ◽  
Local Times ◽  
Nonnegative Orthant ◽  
State Dependent ◽  
The Times ◽  
And Diffusion

In this paper we consider reflected diffusions with positive and negative jumps, constrained to lie in the nonnegative orthant of ℝ n . We allow for the drift and diffusion coefficients, as well as for the directions of reflection, to be random fields over time and space. We provide a boundary behavior characterization, generalizing known results in the nonrandom coefficients and constant directions of the reflection case. In particular, the regulator processes are related to semimartingale local times at the boundaries, and they are shown not to charge the times the process expends at the intersection of boundary faces. Using the boundary results, we extend the conditions for product-form distributions in the stationary regime to the case when the drift and diffusion coefficients, as well as the directions of reflection, are random fields over space.

Measuring gas diffusion coefficients by means of a capillary open at one end

1994 ◽  
Vol 37 (5) ◽  
pp. 581-584 ◽  
Author(s):  
N. D. Kosov ◽  
I. V. Poyarkov
Keyword(s):  
Diffusion Coefficients ◽  
Gas Diffusion
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