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  • Author or Editor: A.M. Zhang x
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Summary  

To separate minor actinides from HLLW by extraction chromatography, a few novel silica-based di(2-ethylhexyl)phosphoric acid (HDEHP), 4,4¢,(5¢)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6), octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), and N,N,N¢,N¢-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric adsorption materials (HDEHP/SiO2-P, DtBuCH18C6/SiO2-P, CMPO/SiO2-P, and TODGA/SiO2-P) were synthesized by impregnating HDEHP, DtBuCH18C6, CMPO, and TODGA into the pores of porous SiO2-P particles, which were the new kind of inorganic/organic composites consisted of macroporous SiO2 and copolymer. The bleeding behavior of these composites was investigated by examining the effect of contact time and HNO3 concentration. It was found that in the tested HNO3 concentration range, a noticeable quantity of DtBuCH18C6, at least 600 ppm, leaked out from DtBuCH18C6/SiO2-P because of the protonation of DtBuCH18C6 with hydrogen ion, while the others were lower and basically equivalent to the solubility of HDEHP, CMPO, or TODGA in corresponding acidities solutions. Based on the batch experiment, the bleeding of CMPO/SiO2-P and TODGA/SiO2-P, the main adsorbents used in MAREC process for HLLW partitioning, was evaluated by column operation in 0.01M HNO3 and 3M HNO3. The quantity of CMPO leaked was ~48 ppm in 0.01M HNO3 and ~37 ppm in 3.0M HNO3. The bleeding of TODGA decreased from 23.2 ppm to 7.27 ppm at the initial stage and then basically kept constant. An actual bleeding of TODGA was evaluated by the separation of Sr(II) from a 2.0M HNO3 solution containing 5.0 . 10-3M of 6 typically simulated elements.

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Summary  

The sorption and desorption of radionuclide 90Sr2+were investigated on untreated calcareous soil and two treated soils to remove organic matter and calcium carbonate using batch technique. The experiments were carried out at ambient condition, pH 7.8±0.1 and in the presence of 0.001M NaCl. Effects of fulvic acid and ionic strength on the sorption of 90Sr2+on calcareous soil were also studied. It was found that the sorption isotherms are linear in the strontium concentration range used herein, and the sorption of 90Sr2+on the calcareous soil can be described as a reversible sorption process and the sorption mechanism is mainly ion-exchange. The sorption is dependent on ionic strength, and fulvic acid enhances the sorption of 90Sr2+on calcareous soil. Organic matter present in the calcareous soil is a significant trap of 90Sr2+and is responsible for the sorption.

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Summary  

The Minor Actinides Recovery from HLW by Extraction Chromatography (MAREC) process was used mainly for the separation of minor actinides (MAs) and some specific fission products (FPs) from highly active liquid waste (HLW) by the composite CMPO/SiO2-P of the macroporous silica based polymeric octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide (CMPO) and others. In this study a cascade of chromatographic separation was performed on a 3.0M HNO3 solution containing 5.0 . 10-3M of 13 elements, at 323 K. The cascade consisted of three columns the first and second ones were packed with CMPO/SiO2-P and the third with SiO2-P particles. The first column was employed to prepare various eluents containing saturated CMPO. The second column was used for separation into groups. The CMPO of CMPO/SiO2-P was recovered from the effluent by the third column and a CMPO-free effluent containing minor actinides was obtained. The elements contained in the simulated HLW of 3.0M HNO3 were separated into (1) a non-adsorption group (Sr, Cs, and Ru etc.), (2) a MA-hRE (heavy rare earth)-Mo-Zr group, and (3) a lRE (light rare earth) group by eluting with 3.0M HNO3, 0.05M DTPA (diethylenetriaminepentaacetic acid) (pH 2.0) and HNO3 (pH 3.5), respectively. The resultant MA-hRE-Mo-Zr mixture containing minor actinides was then separated into the groups (1) Pd-Ru, (2) MA-hRE, and (3) Mo-Zr by utilizing 3.0M HNO3, distilled water, and 0.05M DTPA (pH 2.0) as eluents. More than 92% of CMPO in the MA-hRE containing effluent was adsorbed by SiO2-P particles. The effectivity and technical feasibility of MAREC process were demonstrated.

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Abstract  

A new type of silica-based chelating extraction resin, DtBuCH18C6/SiO2-P, was prepared by impregnating a crown ether derivative, 4,4,(5)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6), into the porous silica/polymer composite particles (SiO2-P). The adsorption of Sr(II) and some other fission product elements was investigated by a batch adsorption experiment in HNO3 medium. It was found that Sr(II) exhibits a strong adsorption onto the extraction resin, while the other fission product elements show almost no or only weak adsorption. The adsorption kinetics of Sr(II) was explained by assuming as the rate-controlling step the complex-formation reaction between Sr(II) and DtBuCH18C6 contained in the extraction resin. The rate equation of Sr(II) adsorption was determined as:-d[Sr(II)]/dt = k[Sr(II)][DtBuCH18C6][NO3 ]0.5.

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Abstract  

By substututing99Mo for the Mo in the reconstituted MoFe protein, the nuclear quadrupole interactions (NQI) of99Mo have been measured using the perturbed angular correlations (PAC). Two well-defined electric quadrupole interaction parameters have been observed. The configuration of the M-Center of the MoFe protein is identified by the quadrupole couplign constant Q1(412(9)MHz) and the asymmetry parameter 1(0.49(5)). Other parameters, VQ2(1939(13)MHz) and 1(0.90(1)), may correspond to a deformation M—Center of MoFe protein.

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Abstract  

On the basis of the theory of thermokinetics proposed in the literature, a novel thermokinetic method for determination of the reaction rate, the characteristic parameter method, is proposed in this paper. Mathematical models were established to determine the kinetic parameters and rate constants. In order to test the validity of this method, the saponifications of ethyl benzoate, ethyl acetate and ethyl propionate, and the formation of hexamethylenetetramine were studied with this method. The rate constants calculated with this method are in agreement with those in the literature, and the characteristic parameter method is therefore believed to be correct.In the light of the characteristic parameter method, we have developed further two thermo-kinetic methods, the thermoanalytical single and multi-curve methods, which are convenient for simultaneous determination of the reaction order and the rate constant. The reaction orders and rate constants of the saponifications of ethyl acetate and ethyl butyrate and the ring-opening reaction of epichlorohydrin with hydrobromic acid were determined with these methods, and their validity was verified by the experimental results.

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Three aromatic polyimides based on 3,3′,4,4′-biphenyl-tetracarboxylic dianhydride (BPDA) and three different diamines 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB), 2,2′-dimethyl-4, 4′-diaminophenyl (DMB) or 3,3′-dimethylbenzidine (OTOL) have been synthesized. These polyimides are soluble in hotp-chlorophenol,m-cresol or other phenolic solvents. Fibers have been spun from isotropic solutions using a dry-jet wet spinning method. The as-spun fibers generally exhibit low tensile properties, and can be drawn at elevated temperatures (>380° C) up to a draw ratio of 10 times. Remarkable increases in tensile strength and modulus are achieved after drawing and annealing. The crystal structures of highly drawn fibers were determinedvia wide angle X-ray diffraction (WAXD). The crystal unit cell lattices have been determined to be monoclinic for BPDA-PFMB and triclinic for both BPDA-DMB and BPDA-OTOL. Thermomechanical analysis (TMA) was used to measure thermal shrinkage stress and strain. A selfelongation has been found in the temperature region around 450°C. This phenomenon can be explained as resulting from the structural development in the fibers as evidencedvia WAXD observations.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: P. Aarnio, J. Ala-Heikkilä, A. Isolankila, A. Kuusi, M. Moring, M. Nikkinen, T. Siiskonen, H. Toivonen, K. Ungar, and W. Zhang

Abstract  

Linssi is a Structured Query Language (SQL) database for HPGe gamma-ray spectrometry. It covers the whole production chain from sample preparation to final analysis results. Static or mobile sampling and measurement and multiple sample types are supported. In addition, each sample can be split or combined any number of times. A sample may be measured multiple times and each measurement multiply analyzed as well. With Linssi, measurement setups with detectors, shields, attenuators and source geometries can be defined. Full control of calibrations, their histories and tracing of each calibration point back to its corresponding analysis and calibration measurement is supported. Linssi database and user scripts are available from http://linssi.hut.fi/radphys/linssi.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: W. Hennig, W. Warburton, A. Fallu-Labruyere, K. Sabourov, M. Cooper, J. McIntyre, A. Gleyzer, M. Bean, E. Korpach, K. Ungar, W. Zhang, and P. Mekarski

Abstract  

Measurement of radioactive xenon in the atmosphere is one of several techniques to detect nuclear weapons testing. For high sensitivity, some existing systems use beta/gamma coincidence detection to suppress background, which is very effective, but increases complexity due to separate beta and gamma detectors that require careful calibration and gain matching. In this paper, we will describe the development and evaluation of a simpler detector system, named PhosWatch, consisting of a CsI(Tl)/BC-404 phoswich well detector, digital readout electronics, and pulse shape analysis algorithms implemented in a digital signal processor on the electronics, and compare its performance to existing multi-detector systems.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: K. Ungar, W. Zhang, P. Aarnio, J. Ala-Heikkila, H. Toivonen, T. Siiskonen, A. Isolankila, A. Kuusi, M. Moring, and M. Nikkinen

Abstract  

Linux System for Spectral Information (LINSSI1) is a SQL database and established under Linux. Currently it is compatible with HPGe gammaspectra analysis software UniSampo, Shaman and Aatami. Based on this database and software, an automated analysis pipeline has been setup for Canadian CTBT radiological monitoring networks. This paper has investigated the performance of this pipeline in its capabilities and reliabilities of rapid small peak search, nuclide identification, and radionuclide activity concentration evaluation. Up to now, more than 80 thousand daily monitoring gamma-spectra have been automatically received and processed, the results have been stored in database. The pipeline nuclide detection limits is satisfied for environmental radiation monitoring and nuclear emergency preparedness.

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