Theoretical Consideration and Recent Progress of Chemical Enrichment Process for Uranium Enrichment

1990 ◽  
Vol 27 (11) ◽  
pp. 983-995 ◽  
Author(s):  
Maomi SEKO ◽  
Kunihiko TAKEDA ◽  
Hatsuki ONITSUKA ◽  
Tetsuya MIYAKE
1990 ◽  
Vol 89 (3) ◽  
pp. 372-380
Author(s):  
Kunihiko Takeda ◽  
Yoshikazu Nishigaki ◽  
Hatsuki Onitsuka

2007 ◽  
Vol 61 (1-2) ◽  
pp. 123-128
Author(s):  
Dragan Zivanov

According to the Non Proliferation Treaty (NPT), the signatory countries are not forbidden to preform uranium enrichment for peaceful purposes. However, if there is a justified doubt that the uranium enrichment is performed with the aim to produce nuclear weapons, this certainly causes great concern. In this case, the international community can apply pressure to a certain country if it determines that the country does not want to cease activities of making its own nuclear weapons. The international community pressure on the country can be intesified until its political leadership is not made to question and cease all activities of producing nuclear weapons. This pressure can be political, economic, and as a last resort-military. As a gesture of goodwill the country can stop the uranium enrichment process. In this way, the country shows that it finally gives up the intention to produce nuclear weapons. However, when military pressure is applied, i.e. military strikes (air strikes for example) on nuclear plants used for uranium enrichment, this certainly creates a risk of releasing radioactivity into the environment. That is why the aim of this paper is to signal this very fact. Using military force in these cases leads to additional radioactive contamination of the environment, so this way of solving conflicts should be avoided within the international community.


1989 ◽  
Vol 26 (11) ◽  
pp. 1061-1064 ◽  
Author(s):  
Yasuhiko FUJII ◽  
Masao NOMURA ◽  
Hatsuki ONITSUKA ◽  
Kunihiklko TAKEDA

Author(s):  
Chen Lei ◽  
Wang Ning

Uranium hexafluoride is the intermediate material of uranium fuel enrichment process, which is widely used in uranium conversion plant, uranium enrichment plant and nuclear fuel element plant[1]. Because of its active chemical properties and its radioactive and chemical toxicity, great importance should be attached to the uranium hexafluoride release accident. This paper describes the possible leakage scenarios for uranium hexafluoride accident. And the general step of the evaluation for uranium hexafluoride leakage accident release source term is given, as well as an application example for the feed facility of a gaseous diffusion plant.


2009 ◽  
Vol 5 (S262) ◽  
pp. 111-114
Author(s):  
Mikako Matsuura

AbstractDue to their brightness in infrared, asymptotic giant branch (AGB) stars are in important evolutionary stage to be understood at this wavelength. In particular, in next decades, when the infrared optimised telescopes, such as the JWST and the ELT are in operation, it will be essential to include the AGB phase more precisely into the population synthesis models. However, the AGB phase is still one of the remaining major problems in the stellar evolution. This is because the AGB stellar evolution is strongly affected by the mass-loss process from the stars. It is important to describe mass loss more accurately so as to incorporate it into stellar evolutionary models. Recent observations using the Spitzer Space Telescope (SST) enabled us to make a significant progress in understanding the mass loss from AGB stars. Moreover, the SST large surveys contributed to our understanding of the role of AGB stars in chemical enrichment process in galaxies. Here we present the summary of our recent progress.


1988 ◽  
Vol 81 (3) ◽  
pp. 421-428 ◽  
Author(s):  
Kunihiko Takeda ◽  
Hatsuki Onitsuka ◽  
Heiichiro Obanawa ◽  
Shin Saito

1989 ◽  
Vol 44 (5) ◽  
pp. 395-398 ◽  
Author(s):  
Y. Fujii ◽  
M. Nomura ◽  
M. Okamoto ◽  
H. Onitsuka ◽  
F. Kawakami ◽  
...  

The abundance ratios of 234U, 235U, 236U and 238U were determined by mass spectrometry on uranium samples obtained from a chromatographic uranium enrichment process based on the U(IV) - U(VI) chemical exchange reaction. According to standard theory, the elementary isotope effect in processes based on equilibrium chemical exchange is proportional to the mass difference of the isotopes. In the present work this has been confirmed for 234U, 236U and 238U. However, according to the observed data the fractionation between 234U and 235U is much smaller than the one between 235U and 236U in spite of the same mass difference in either isotopic pair. The anomaly of the fractionation is concluded to be due to the characteristics of 235U, which is the only odd mass number isotope in the present system.


Author(s):  
Teruo Someya ◽  
Jinzo Kobayashi

Recent progress in the electron-mirror microscopy (EMM), e.g., an improvement of its resolving power together with an increase of the magnification makes it useful for investigating the ferroelectric domain physics. English has recently observed the domain texture in the surface layer of BaTiO3. The present authors ) have developed a theory by which one can evaluate small one-dimensional electric fields and/or topographic step heights in the crystal surfaces from their EMM pictures. This theory was applied to a quantitative study of the surface pattern of BaTiO3).


Author(s):  
Dawn A. Bonnell ◽  
Yong Liang

Recent progress in the application of scanning tunneling microscopy (STM) and tunneling spectroscopy (STS) to oxide surfaces has allowed issues of image formation mechanism and spatial resolution limitations to be addressed. As the STM analyses of oxide surfaces continues, it is becoming clear that the geometric and electronic structures of these surfaces are intrinsically complex. Since STM requires conductivity, the oxides in question are transition metal oxides that accommodate aliovalent dopants or nonstoichiometry to produce mobile carriers. To date, considerable effort has been directed toward probing the structures and reactivities of ZnO polar and nonpolar surfaces, TiO2 (110) and (001) surfaces and the SrTiO3 (001) surface, with a view towards integrating these results with the vast amount of previous surface analysis (LEED and photoemission) to build a more complete understanding of these surfaces. However, the spatial localization of the STM/STS provides a level of detail that leads to conclusions somewhat different from those made earlier.


Sign in / Sign up

Export Citation Format

Share Document