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Abstract  

We give a non-existence theorem for Hopf hypersurfaces in complex two-plane Grassmannians G 2(ℂ m+2) whose structure Jacobi operator R ξ is of Codazzi type.

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Abstract  

In this paper, a separation method of radionuclides (Ba, Sr) from LiCl salt wastes generated from the electroreduction process of spent nuclear fuel was studied to recover pure LiCl salts and reduce radioactive wastes. The method consisted of chemical conversion process of BaCl2 and SrCl2 in LiCl molten salts by using lithium compounds and vacuum distillation process of LiCl salts. In the chemical conversion, BaCl2 and SrCl2 in LiCl molten salts were mainly converted into (Ba,Sr)CO3 or (Ba,Sr)SO4. Contents of Ba and Sr in LiCl salts recovered from the vacuum distillation process were equal to about 0.01 of initial concentrations of Ba and Sr in LiCl molten salts. These results will be utilized to recycle the LiCl salt wastes.

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Abstract  

Distillation and condensation characteristics of LiCl-KCl eutectic salts containing rare earth precipitates were investigated and a conversion of the rare earth oxychlorides to oxides was performed. The distillation flux was increased by about 1,000 times by reducing the pressure from 760 Torr to 0.5 Torr. The composition of the recovered salts was changed according to the condensed spot. The conversion temperature of the multicomponent oxychlorides was decreased when compared to that of a single component. It was found that the concentration of the chloride gas in the flue gas is an index to establish whether the conversion is completed or not.

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Abstract  

A study on the precipitation of uranium by oxalic acid was carried out in a multicomponent solution. The precipitation method is usually applied to the treatment of radioactive waste and the recovery of uranium from a uranium-scrap contaminated with impurities. In these cases, the problem is how to increase the precipitation yield of target element and to prevent impurities from coprecipitation. The multicomponent solution in the present experiment was prepared by dissolving U, Nd, Cs and Sr in nitric acid. The effects of concentrations of oxalic acid and ascorbic acid on the precipitation yield and purity of uranium were observed. As results of the study, the maximum precipitation yield of uranium is revealed to be about 96.5% and the relative precipitation ratio of Nd, Cs and Sr versus uranium are discussed at the condition of the maximum precipitation yield of uranium, respectively.

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Silicon (Si) is essential for normal growth and development in plants and is also beneficial for their responses to wounding. However, the mechanisms by which Si acts to mitigate the effects of wounding is not fully understood. This effect possibly occurs through a reduction in the oxidative stresses associated with wounding. Here, we tested this possibility by investigating the effects of applying different concentrations of Si (0,5 and 1,0 mM) to rice plants under wounding stress for a period of 6 and 12 h. We found that a higher uptake of Si was signifiacntly associated with an increase in leaf chlorophyll contet. In response to wounding induced oxidative stress, the extent of lipid bilayer peroxidation was reduced in a dose-dependent manner by Si application for 6 or 12 h. Activity of the catalase enzyme was initially lowered by Si treatment; however, at 1.0 mM Si, catalase activity increased significantly after 12h of wounding stress. A similar response was also observed for a peroxidase enzyme. Polyphenol oxidase showed a significant reduction in activity. We conclude that Si application does not only improve leaf chlorophyll content but can also overcome the oxidative stress due wounds or physical injuries.

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Abstract  

This paper describes ongoing research into the multi-physics model development of an electrorefining process for the treatment of spent nuclear fuel. A forced convection of molten eutectic (LiCl–KCl) electrolyte in an electrorefining cell is considered to establish an appropriate electro-fluid model within the 3-dimensional framework of a conventional computational fluid dynamic model. This computational platform includes the electrochemical reaction rate of charge transfer kinetics which is described by a Butler–Volmer equation, while mass transport is considered using an ionic transport equation. The coupling of the local overpotential distribution and uranium concentration gradient makes it possible to predict the local current density distribution at the electrode surfaces.

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Abstract  

A computational fluid dynamics (CFD)-based multiphysics model of a molten-salt electrorefiner is presented for the computational electro-fluid analysis. A target model of the electrorefining cell presented here has a structure arranged concentrically with the cathode annulus surrounding a rotating cruciform anode inside it. This comprehensive approach of a multiphysics model solves the convective and diffusive transport of ionic uranium and allows for a prediction of the concentration present in the LiCl–KCl eutectic electrolyte between the electrodes at a current driven condition. The coupling of the local overpotential distribution and uranium concentration gradient makes it possible to predict the local current density distribution at the electrode surfaces.

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Journal of Thermal Analysis and Calorimetry
Authors:
W. Liu
,
S. Kim
,
J. Lopez
,
B. Hsiao
,
M. Keating
,
I.-H. Lee
,
B. Landes
, and
R. Stein

Abstract  

In this study, the stepwise isothermal crystallization or thermal fractionation of Ziegler—Natta and metallocene based polyethylenes (ZN-PE and m-PE) with two kinds of branch lengths (ethyl and hexyl) and branch compositions were studied using simultaneous synchrotron small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The crystal long period and the invariant were determined by SAXS, and the variations of crystal unit cell parameters and the degree of crystallinity were determined by WAXD. The arithmetic mean length (Ln), the weightedmean length (Lw) and the broadness index (Lw/Ln) of the studied polyethylenes were previously determined by DSC. Results from these studies were interpreted using the model of branch exclusion, which affects the ability of the chain-reentry into the crystal phase. Multiple SAXS peaks and step-change in crystallinity change (WAXD) were seen during heating, which corresponded well with the crystal thickness distribution induced by stepwise crystallization. The effects of the heterogeneity of the 1-olefin branch length and the distribution on the crystal long period and the invariant as well as the degree of crystallinity were discussed.

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Summary  

Minerals in the soil range from those that easily weather to those that are very resistant to the weathering processes. The minerals used in this study are referred to as “resistates” because of their resistance to natural weathering processes.1 It is also known that there are some resistate minerals that have a tendency to contain uranium and thorium within their crystal structure. These resistates can contain as much as 15-20% of the total uranium and thorium present in the soil.9 Do resistates dissolve in acids, particularly in the HF/HNO3 procedures, if not what can be done to the HF/HNO3 process to dissolve more of the resistate minerals? How would these acid techniques compare to the fusion method used for mineral dissolution? Could the resistate minerals contain considerable amount of uranium and thorium? These were the questions addressed in this research. The comparative data indicate that the use of H2SO4 in the dissolution process resulted in ~25% overall increase in the minerals dissolving therefore resulting in a higher yield of extracted uranium and thorium.

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Summary  

A procedure is described to extend the current radiochemical method of seawater analysis for Pu and Am including Np. Short-lived 239Np tracer was prepared by separation from its 243Am parent. Irish Sea Water reference material (IAEA-381) containing known concentrations of 237Np, Pu isotopes and 241Am was used to test the procedure for small water volumes. Inductively-coupled plasma mass spectrometry (ICP-MS) was used in addition to alpha spectrometry for measurement of 237Np in the purified final Np fractions.

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