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  • Author or Editor: M. Ahmad x
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Abstract  

Prompt gamma-rays from thermal neutron capture reaction have been used to measure the concentrations of the main constituents namely Fe, Ni and Cr in 316-L stainless steel using recently established prompt gamma neutron activation analysis (PGNAA) facility at Pakistan Institute of Nuclear Science and Technology (PINSTECH). High resolution, high purity germanium detector with 40% relative efficiency was employed for the gamma-ray spectroscopy of the samples. The interference-free full energy gamma-ray peaks of the elements of interests were selected in the high energy low background region (5.0–9.0 MeV). The efficiency calibration of the detector was performed using ultra pure standards of chromium and chlorine obtained respectively from Merck and Alpha Inorganics. This paper describes, in addition, the salient features as well as the background of establishing PGNAA facility at the Institute.

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Summary  

This study provides useful information about the level and chemical composition of particulate matter and about the possible sources of the aerosol pollutant in Islamabad, the capital of Pakistan. Atmospheric aerosol samples were collected during winter (January and February) 1995, from two locations of Islamabad, namely of Sector F-7 and Sector I-9. Twenty-four elements were detected by using thermal neutron activation analysis (NAA) and atomic absorption spectrometry (AAS). The concentration of total suspended particulates (TSP) in the area around the industrial sector (I-9) was found to be more than twice higher (297 μg/m3) than in the Sector F-7 (133 μg/m3). The enrichment factor analysis revealed Zn, As, Br, Sb, I and Pb, originated mainly from anthropogenic sources. The elemental ratio analysis indicated that both Sectors I-9 and F-7 are under the influence of coal burning processes whereas transportation is responsible for the toxic pollutants Pb and Br. The present results were discussed and compared with those of the literature. The results may also serve as base line level as this work employed samples collected in 1995 and many of the air environmental change factors occurred after the sampling year.

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Abstract  

HNO3 transport across tri-n-butyl phosphate kerosene oil supported liquid membrane with or without uranyl ion transport has been studied. Parameters studied are the effect of TBP in the membrane, nitric acid in the feed solution and nitrate ion concentration in the feed solution. The flux of protons for 1 to 10 mol·dm–3 HNO3 solution is in the range of (0–25)·10–4 mol·m–2·s–1 and for the TBP concentration range of 0.359 to 3.59 mol·dm–3, the flux determined is (8.9 to 22)·10–4 mol·m–2·s–1. From the experimental data and using theoretical equations the complex under transport through the membrane appears to be 2TBP·HNO3 both in the presence and absence of uranyl ions. The diffusion coefficient for H+ ions through the membrane as a function of TBP concentration varies from (53 to 6)·10–12 m2·s–1, based on experimental flux and permeability data. The values of this coefficient supposing 2TBP·HNO3 as diffusing species, based on viscosity data and theoretical estimation varies from (82.50 to 3.30)·10–12 m2·s–1. The value of distribution coefficient varies in the reverse direction from 0.06 to 1.46 at the same TBP concentration.

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Abstract  

The characteristic absolute efficiency response curves of a high purity germanium detector (HPGe) for different counting geometries have been established in the energy range 50–1500 keV by measuring the absolute efficiencies using both mono-energetic and multi-gamma emitting radionuclide point calibrated sources supplied by IAEA. Several fitting functions proposed in the literature were assessed for interpolation within the intermediate energy range of interest. The values of the function parameters have been determined by using the linear least square methods. The problems associated with the measurements of experimental efficiency data at small source–detector distances and the importance of the correlation matrix in the estimation of precise uncertainties have been shown. It was found that the inclusion of correlation matrices in the propagation of error formulae plays a significant role up to 450 keV gamma-ray energy and results in a drastic reduction of errors associated with the predicted efficiencies. The discrepancy at closer counting geometries in the absence of true gamma-gamma coincidence corrections is found to reach to about 30%.

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Abstract  

Study of the extraction of W(VI) ions using supported liquid membrane has been carried out. The carrier used for this metal ion transport, is tri-n-octylamine (TOA) dissolved in xylene. The liquid was supported in microporous polypropylene film. The parameters studied are effect of carrier concentration in the membrane, acid concentrations in the feed solution, concentration of stripping agent on transport of W(VI) ions and of temperature on the transport properties of these supported liquid membranes. The optimum conditions of transport for these metal ions determined are, TOA concentration, 0.66 mol·dm–3 (TOA); HF concentration in the feed solution, 0.01 mol·dm–3 and concentration of NaOH used as stripping agent 2.5 mol·dm–3. The maximum flux and permeability determined under optimum conditions are 3.06·10–5 mol·m–2·s–1 and 8.44·10–11 mol· ·m2·s–1 at 25±2°C and 4.21·10–5 mol·m–2·s–1 and 11.55·10–11 mol·m2·s–1 at 65°C, respectively. The diffusion coefficients for the metal ion carrier complex in the membrane have also been determined. Under the optimum conditions the value for the metal ion carrier complex is 0.14·10–11 mol·m2·s–1. Mechanism of transport and the complex formed in the presence of HF have also been discussed. The transport process involves two carrier amine molecules and two protons.

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Abstract  

The nuclear properties of99mTc radionuclide are ideal for organ imaging. Study of the technetium transport across supported liquid membranes has been performed to get data for its separation from other elements. Tri-n-octylamine diluted in xylene was used to constitute the liquid membranes, supported in polypropylene microporous films. Stripping on the product solution side was performed with dilute NaOH solutions. The effect of sulphuric acid, nitric acid and hydrochloric acid in the feed on transport of99mTc as TcO 4 ions has been studied. The permeability of the given ions determined from kinetic activity data has been found to be in the order of PH2SO4>PHCl>PHNO3. The flux values have been calculated based on this permeability data. The increase in carrier concentration has shown an increase in flux and permeability values to a given optimum concentration. The increase in temperature has been found to reduce the transport of Tc ions. The optimum conditions for transport of99mTc for the given acid concentration have been determined. Mechanism of Tc ion transport has also been provided based on chemical reactions involved at the membrane interfaces and uptake of Tc ions by the membrane. MoO 4 2– ions do not permeate through membrane under optimum conditions of transport for TcO 4 2– ions from H2SO4 solution.

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Abstract  

Transport study for Ti(IV) ions using di-2-ethylhexylphosphoric acid (D2EHPA) (carrier)-CCl4 (diluent) liquid supported membrane in microporous polypropylene hydrophobic film has been performed. The parameters studied are effects of carrier, H2SO4, stripping agent (NH4F) concentrations and temperature variation on flux and permeability coefficients of the metal ion. The optimum concentrations of transport found are 2.04 mol·dm–3 D2EHPA, 1.0 mol·dm–3 H2SO4 in the feed and 1 mol·dm–3 NH4F as stripping agent. The maximum flux and permeability coefficient determined are 1.32·10–5 mol·m–2·s–1 and 8.02·10–12 mol·m–2·s–1, respectively. The transport of this metal ion is increased with increase in temperature. The mechanism of transport appears to be based on coupled counter ion transport phenomenon.

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Abstract  

A sensitive radiochemical procedure has been developed for the separation and determination of Dy, Sm, Gd, Eu, La and Lu in high purity uranium. The method is based on quantitative extraction of uranium using NPy/benzene as an extractant from 7M HCl solution. Rare earth elements (REE) remaining in the aqueous phase were subsequently determined by INAA.

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