Diffusion of Non-Gaseous Fission Products in UO2 Single Crystals II

1965 ◽  
Vol 20 (5) ◽  
pp. 673-675 ◽  
Author(s):  
Noboru Oi ◽  
Jinzaburo Takagi
Keyword(s):  
Diffusion Process ◽  
Single Crystals ◽  
Process Analysis ◽  
Diffusion Constant ◽  
Fission Products ◽  
Post Irradiation ◽  
Temperature Range ◽  
Gaseous Fission ◽  
Kinetics Of

The release of short-lived non-gaseous fission products from UO2 single crystals was studied in the temperature range of 1400 —2500°C by means of post-irradiation annealing. The release of the fission products studied appears to follow the kinetics of a diffusion process. Analysis of the data obtained gives the following diffusion constant,DΜο = 3.9 × 10-4 exp(-54,000/RT), DI = 1.5 x 10-3 exp(-59,000/RT), DTe = 6.6 × 10-3 exp(— 70,000/RT), DLa (tentative) =2.2 x 10-6 exp (— 35,000/RT)where the dimensions of D and RT are cm2/sec and cal/mol, respectively.

scholarly journals Evaporation Behavior of Non-gaseous Fission Products from UO2

1965 ◽  
Vol 20 (12) ◽  
pp. 1566-1568 ◽  
Author(s):  
J. Takagi
Keyword(s):  
Fission Product ◽  
Release Rate ◽  
Diffusion Constant ◽  
Fission Products ◽  
Post Irradiation ◽  
Product Release ◽  
Proportionality Constant ◽  
Gaseous Fission ◽  
Gaseous Fission Product ◽  
General Method

The evaporation behavior of non-gaseous fission products from UO2 was studied. The release rate of non-gaseous fission products during the post-irradiation annealing of UO2 was found to be controlled by the proportionality constant of evaporation, a, as well as the diffusion constant. The values of α for Ru, Ce, La, Mo and Te were determined at temperatures ranging 750 to 1600 °C and the general method of treating non-gaseous fission product release from UO2 was discussed.

MBE growth of compound semiconductors: Part II. Applications of the stochastic model

1992 ◽  
Vol 7 (5) ◽  
pp. 1235-1242 ◽  
Author(s):  
R. Venkatasubramanian
Keyword(s):  
Growth Rate ◽  
Surface Roughness ◽  
Phase Separation ◽  
Stochastic Model ◽  
Diffusion Process ◽  
Surface Diffusion ◽  
Growth Front ◽  
Mbe Growth ◽  
Temperature Range ◽  
Kinetics Of

In this part of the work (Part II), two typical applications of the stochastic model to the MBE growth kinetic studies are presented. The applications are the MBE growth kinetics of a hypothetical compound semiconductor, ab, and diamond cubic alloy, ax. In this study, the effect of the surface diffusion process on the MBE growth kinetics is analyzed. In the case of the compound, ab, the results of the present stochastic model are compared with that of a Monte Carlo simulation study in the temperature range of 600–850 K. The results of the two studies agree qualitatively. Higher substrate temperatures result in higher growth rate and growth front smoothness due to higher surface diffusion. Beyond 800 K, the growth rate and the growth front smoothness become independent of temperature because of the saturation of the interlayer diffusion process. In the case of the alloy studies, the kinetics of a hypothetical diamond cubic alloy in which the thermodynamics favors phase separation, is studied in the temperature range of 573–898 K. Below 648 K, due to negligible surface diffusion, there is no clustering of the alloy, but the surface roughness is very large. In the intermediate temperature range of 573–798 K, with increasing temperature, the surface diffusion increases, resulting in more clustering and less surface roughness. Above 798 K, due to very high surface diffusion, complete phase separation of the alloy and a smooth surface result.

KINETICS OF THE OXIDATION OF TITANIUM

1950 ◽  
Vol 28b (2) ◽  
pp. 60-72 ◽  
Author(s):  
L. M. Pidgeon ◽  
W. A. Alexander
Keyword(s):  
Low Temperatures ◽  
Oxidation Process ◽  
Film Formation ◽  
Surface Film ◽  
Diffusion Constant ◽  
Initial Oxidation ◽  
Temperature Range ◽  
Logarithmic Equation ◽  
Kinetics Of ◽  
And Diffusion

The rates of oxidation of titanium powder and sintered bar have been investigated in the temperature range 25° to 550 °C. at pressures of 2 and 20 cm. oxygen maintained constant throughout each experiment. It has been shown that the oxidation process can be divided into two mechanisms, viz., the formation of a thin surface film and diffusion of oxide into the metal. The surface film formation at low temperatures follows the logarithmic equation:[Formula: see text]on vacuum annealed metal surface. The diffusion process at higher temperatures is described by the equation:[Formula: see text]after the initial oxidation. This equation leads to preliminary values of the diffusion constant of the order of 10 × 10−8 cm2. per min. in the temperature range 463° to 565 °C.

scholarly journals Kinetics of MgWO4 Formation in the Solid State Reaction between MgO and WO3

1976 ◽  
Vol 31 (6) ◽  
pp. 619-621 ◽  
Author(s):  
Giorgio Flor ◽  
Riccardo Riccardi
Keyword(s):  
Solid State ◽  
Kinetic Study ◽  
Single Crystals ◽  
Solid State Reaction ◽  
Argon Atmosphere ◽  
Conductivity Measurements ◽  
Linear Rate ◽  
Rate Law ◽  
Temperature Range ◽  
Kinetics Of

The solid state reaction of MgWO4 formation from MgO (single crystals) and WO3 was investigated in the temperature range 800 - 985 °C under both air and argon atmosphere.The techniques employed for the kinetic study (contact and thermogravimetric methods) allowed to point out that the process follows the linear rate law in the early stages and the parabolic one in the subsequent stages.From inert marker experiments, kinetic determinations under the two different atmospheres and conductivity measurements, it was possible to state that the reaction is governed by a cation counterdiffusion mechanism

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

Study of potential oscillations during reaction of an aluminium single crystal with an aqueous KOH solution

1990 ◽  
Vol 55 (2) ◽  
pp. 345-353 ◽  
Author(s):  
Ivan Halaša ◽  
Milica Miadoková
Keyword(s):  
Aqueous Solutions ◽  
Single Crystal ◽  
Single Crystals ◽  
Periodic Potential ◽  
Optimum Conditions ◽  
Potential Oscillations ◽  
Dilute Aqueous Solutions ◽  
Experimental Findings ◽  
Kinetics Of

The authors investigated periodic potential changes measured on oriented sections of Al single crystals during spontaneous dissolution in dilute aqueous solutions of KOH, with the aim to find optimum conditions for the formation of potential oscillations. It was found that this phenomenon is related with the kinetics of the reaction investigated, whose rate also changed periodically. The mechanism of the oscillations is discussed in view of the experimental findings.

scholarly journals The combustion of aromatic and alicyclic hydrocarbons. II. The ignition of aromatic hydrocarbons at high temperatures

1939 ◽  
Vol 171 (946) ◽  
pp. 421-433 ◽  
Keyword(s):  
High Temperatures ◽  
Aromatic Hydrocarbons ◽  
Isothermal Oxidation ◽  
Present Communication ◽  
Temperature Range ◽  
Benzene Toluene ◽  
The Subject ◽  
Kinetics Of

In the first paper of this series (Burgoyne 1937) the kinetics of the isothermal oxidation above 400° C of several aromatic hydrocarbons was studied. The present communication extends this work to include the phenomena of ignition in the same temperature range, whilst the corresponding reactions below 400° C form the subject of further investigations now in progress. The hydrocarbons at present under consideration are benzene, toluene, ethylbenzene, n -propylbenzene, o-, m - and p -xylenes and mesitylene.

Test facility for studying kinetics of release of gaseous radioactive fission products from irradiated materials

1974 ◽  
Vol 36 (1) ◽  
pp. 89-91
Author(s):  
D. M. Skorov ◽  
A. I. Dashkovskii ◽  
A. G. Zaluzhnyi ◽  
O. M. Storozhuk
Keyword(s):  
Fission Products ◽  
Test Facility ◽  
Kinetics Of
Sign in / Sign up

Export Citation Format

Share Document