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  • Author or Editor: Yu Yu-Fu x
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Abstract  

The present paper reviews briefly the recent advance in radioanalysis of low level plutonium in environmental and biological samples. Lots of new radiochemical methods for determination of plutonium in aerosols, natural waters, soil, sediments and various biological materials have been developed. The use and prospects of several radiochemical procedures are discussed.

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Abstract  

A study on solvent extraction of cerium/III/ ion with 1-/2-pyridylazo/-2-naphthol /PAN or HL/ in chloroform from perchloric acid solution is described. The effect of equilibrium time, the pH of the aqueous phase and the concentration centration of extractant in organic phase on the extraction efficiency of cerium/III/ has been studied. The results show that the mechanism of extraction reaction is 3Ce /aq/ 3+ + 3HL/o/ CeL3/o/ + 3H + /aq/

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Abstract

A surface immersed in R 4 is called a proper affine sphere if the position vector belongs to the affine normal plane. We classify proper affine spheres with ∇ g =0 whose affine mean curvature vector has constant length. Moreover, we find some concrete examples of affine spheres which are not affine umbilical.

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Abstract  

A study on extraction of thorium with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP)-loaded polyurethane foam is described. Open-cell polyurethane foam has proved to be effective as supporting material for PMBP. Thorium nitrate can be quantitatively extracted by PMBP-loaded polyurethane foam over a wide pH range. The effect of equilibrium time, pH, thorium concentration, various anions and flow-rate on the extraction efficiency of thorium is examined. A technique of extraction chromatography column with PMBP foam cylinder has been developed for trace thorium analysis of bulky water samples.

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Abstract  

Low level90Sr in environmental and biological samples is determined using a combined HDEHP solvent extraction-liquid scintillation procedure. Yttrium-90 is selectively extracted from nitric acid solution into 5% di(2-ethylhexyl) phosphoric acid (HDEHP) in toluene, and90Y in the organic phase is measured directly using an ultra low level liquid scintillation spectrometer.The working program of the Quantulus counter has been optimized. As the counting efficiency using liquid scintillation counting is high and the stripping and precipitation of Yttrium-90 oxalate is omitted, this procedure is simpler and more timesaving than traditional methods. The chemical recoveries of90Y were 85.1% for soil, 75.7% for milk and 65.3% for bone. The detection limit is 8 mBq.

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Abstract  

An improvement of -energy resolution for determining low level plutonium has been investigated using combined solvent extraction-low level liquid scintillation counter. In the present work, -energy resolution of 270–290 keV for liquid scintillation spectra of236Pu and239Pu is attained. Thus the simultaneous determination of low level plutonium with -liquid scintillation spectrometry may be practized.

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Abstract  

A method has been investigated for high-speed and efficient recovery of palladium from reprocessing waste of spent nuclear fuel by mixing the matrix feedstock with a small amount of KI and an appropriate inert solvent (such as kerosene) as collecting agent. Equilibrium of the reaction can be obtained in less than 30 sec. Percent recovery of palladium is more than 97%. Decontamination coefficient is high. No loss of effectiveness of the system was observed below 1×106 rad of irradiation.

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Fine, hollow, spherical particles with an average size of one micronmeter were formed through pyrolysis of aerosol of nickel nitrate solution. The aerosol product obtained by fast heating to 450°C consisted of tiny crystallites of NiO, hydrated nitrate, and other non-crystalline phase(s). By heating above 480°C, it consisted only of crystalline NiO. To understand the reactions occurring during the aerosolization process, thermal analysis was conducted on nickel nitrate hexahydrate in stagnant and flowing air using different heating rates. The mechanism for the decomposition of nickel(II) nitrate hexahydrate is proposed.

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The off-line two-dimensional supercritical fluid chromatography (SFC)–ultrahigh-performance liquid chromatography (UHPLC) was selected to separate the triterpene saponins from Panax notoginseng. The separation by SFC was performed on an Atlantis® HILIC silica column. Methanol was selected as a modifier, and the most time-saving gradient was developed. The decrease of the column temperature and the increase of the back pressure could shorten the retention time but had no effect on the separation selectivity. Then, the back pressure, column temperature, and flow rate were set as 131 bar, 45 °C, and 4.0 mL min−1, respectively. The retention behavior of the saponins from P. notoginseng was different between SFC and reversed-phase liquid chromatography (RPLC), which facilitated to construct an off-line SFC/RPLC–mass spectrometry (MS) system. In first dimension, a total of eight fractions were collected under SFC and further analyzed by RPLC–MS in second dimension. The result indicated that the retention behavior of triterpene saponins was mainly controlled by the hydrogen bonding interactions which were affected by the number and types of sugars, as well as the aglycone in the structure of triterpene saponins. Thus, the presence of “clustering effect” under SFC was observed, namely, one SFC peak always contained several saponins with same number of sugars and similar structure of aglycone. The clustering effect of triterpene saponins promised SFC to be used as first dimension to complete the preliminary crude separation in the two-dimensional liquid chromatography.

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Abstract  

The synergistic extractions of uranium(VI) nitrate using HDEHP,* PMBP** and TBP*** have been studied from benzene media. A new method is proposed to calculate the equilibrium constants for such kinds of ternary synergistic extraction systems. The extraction reactions and their equilibrium constants were found. Models for the extraction mechanism are also discussed.

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