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El-Khayatt A.M.,Egypt Atomic Energy Authority
Annals of Nuclear Energy | Year: 2010

The shielding of γ-rays and fast neutrons by concrete has been studied for concretes containing different lime/silica ratios. Calculations were carried out for six different concrete samples. The total mass attenuation coefficients (μ/ρ, cm2 g-1) have been computed at photon energies of 1 keV to 100 GeV using the personal computer software package WinXCom. Also the macroscopic effective fast neutron removal cross-sections (ΣR, cm-1) have been calculated using MERCSF-N program and the removal cross-section database for all required elements. The obtained results showed that the lime/silica ratio of concrete has significant and insignificant effects on μ/ρ and ΣR values, respectively. © 2010 Elsevier Ltd. Source

Saleh H.M.,Egypt Atomic Energy Authority
Nuclear Engineering and Design | Year: 2012

Phytoremediation is based on the capability of plants to remove hazardous contaminants present in the environment. This study aimed to demonstrate some factors controlling the phytoremediation efficiency of live floating plant, water hyacinth (Eichhornia crassipes), towards the effluents contaminated with 137Cs and/or 60Co. Cesium has unknown vital biological role for plant while cobalt is one of the essential trace elements required for plant. The main idea of this work i.e. using undesirable species, water hyacinth, in purification of radiocontaminated aqueous solutions has been receiving much attention. The controlling factors such as radioactivity concentration, pH values, the amount of biomass and the light were studied. The uptake rate of radiocesium from the simulated waste solution is inversely proportional to the initial activity content and directly proportional to the increase in mass of plant and sunlight exposure. A spiked solution of pH ≈ 4.9 was found to be the suitable medium for the treatment process. The uptake efficiency of 137Cs present with 60Co in mixed solution was higher than if it was present separately. On the contrary, uptake of 60Co is affected negatively by the presence of 137Cs in their mixed solution. Sunlight is the most required factor for the plant vitality and radiation resistance. The results of the present study indicated that water hyacinth may be a potential candidate plant of high concentration ratios (CR) for phytoremediation of radionuclides such as 137Cs and 60Co. © 2011 Elsevier B.V. All rights reserved. Source

El-Morshedy S.E.-D.,Egypt Atomic Energy Authority
Nuclear Engineering and Design | Year: 2012

One of the most limiting critical phenomena, which nuclear designers must consider, is the onset flow instability (OFI) phenomenon. It is the critical phenomenon limiting the reactor power from the thermal-hydraulic point of view especially material testing reactors (MTR). In the present study, an empirical correlation is developed to predict OFI in narrow vertical rectangular channels simulating coolant channels of MTR. The developed correlation involved almost all parameters that affecting OFI phenomenon in a dimensionless form. The coefficients involved in the proposed empirical correlation are identified by experimental data of Whittle and Forgan (1967) that covers the wide range of MTR operating conditions. The correlation predictions for subcooling at OFI are compared with predictions of some previous correlations where the present correlation gives much better agreement with the experimental data of Whittle and Forgan with relative standard deviation of only 6.6%. The present correlation is then used to predict the void fraction and pressure drop in subcooled boiling where the S-curves of Whittle and Forgan for OFI are predicted with good accuracy. Based on the present correlation, the OFI locus for the IAEA 10 MW MTR generic reactor is predicted and plotted against the flow velocity, exit coolant temperature and bubble detachment parameter under both fast and slow loss-of-flow transients where a vast safety margins for OFI phenomenon are predicted in both the steady and transient states as well. © 2011 Elsevier B.V. All rights reserved. Source

El Abd A.,Egypt Atomic Energy Authority
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2014

Void fraction simulating stratified air-water flow in cylindrical tubes of different radii was measured using transmission and scattering of gamma rays. A simple experimental set-up using 137Cs γ-ray point source of 10 μCi and NaI(Tl) detector was used. The void fractions determined from Compton-Compton scattering and transmission peaks were found in good agreement with the real void fractions. However, deviations were noticed between the results obtained from traditional Compton scattered gamma rays and real void fraction. It was shown that sensitivity of gamma ray scattering is better than the transmission measurements. The set-up used in the present work is simpler than those existing in literature and radiation safety and shielding requirements are minimized. © 2013 Elsevier B.V. Source

A systematic liquid-liquid extraction of lanthanum and neodymium from aqueous nitric acid solutions using a mixture of two neutral extractants, namely trioctylphosphine oxide (TOPO) and trialkylphosphine oxide (TRPO) in kerosene has been investigated. The different factors influencing the extraction affinity of those metals have been studied in detail. The extracted species for both metals have been found in the form of [M(NO3)3(TOPO)(TRPO)̄], where M refers to the metal ion. The temperature had a negative effect on the extraction of the metals where the extraction process has been found to be spontaneous in nature and associated with exothermic reaction. Since yttrium is accompanied with these metals in monazite ore, the extraction of Y(III) has also been studied. Based on the results obtained, a proposed method has been suggested to extract and separate the above metals from the hydrous oxide cake resulted by alkaline leaching of Egyptian monazite and a schematic diagram explaining the process has been presented. © 2012 Elsevier B.V. All rights reserved. Source

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