Pakistan Atomic Energy Commission

Islamabad, Pakistan

Pakistan Atomic Energy Commission

Islamabad, Pakistan
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Kafeel K.,Pakistan Atomic Energy Commission | Ahmed G.,Pakistan Atomic Energy Commission
ICET 2016 - 2016 International Conference on Emerging Technologies | Year: 2016

Dry storage casks are standalone containers that can be used to store spent nuclear fuel for an extended period of time. This paper is about the modeling and simulation of air ventilated dry storage cask used for long term storage of spent fuel assemblies from pressurized water reactors. A two-dimensional axis-symmetric model is generated for the actual cask geometry in order to simulate the thermal hydraulic behavior of the cask. The effects of natural circulation along with conjugate heat transfer have been taken into account within the numerical modeling scheme. Result obtained from the generated model is verified through comparison with data available in the literature. The model is then utilized to predict the cask response when loaded with spent fuel assemblies from Chashma nuclear power plant located in Pakistan. © 2016 IEEE.

Bakar M.A.,Pakistan Atomic Energy Commission | Sarwar M.S.,Pakistan Atomic Energy Commission
ICET 2016 - 2016 International Conference on Emerging Technologies | Year: 2016

The presented analysis carried out for the safety assessment of the Passive Residual Heat Removal System of secondary side (PRS), one of the Severe Accident Mitigating System of K-2/K-3 Nuclear power plants. Preliminary analysis of the PRS is carried out using computer code MELCOR, which is a thermal hydraulic code that models the progression of severe accidents in light water nuclear power plants. The system was analyzed under SBO without the main feed-water, auxiliary feed-water and the safety injection systems. The system is activated after the SBO and failure of auxiliary feed-water pumps and the turbine driven pumps by opening the isolation valves and closing the main steam isolation valve to avoid the steam loss. Three trains of PRS are modeled and connected with secondary side of each Steam Generators along with a make-up tank, each trains is connected with the same cooling tower (Heat Sink). The system can maintain the reactor in safe condition for 72 hours, if it is actuated before the large loss of primary coolant inventory or fuel damage in the core. The three independent trains for each steam generator are consider for heat removal of secondary side. If one of the train is considered unavailable that will lead to fuel failure and RPV failure within 72 hours. Although the failure time increases in comparison to the SBO without the PRS. The reactor remains in safe conditions if the PRS system operate at or above 80% of its design thermal load removing capability. The safety assessment was made with and without using this severe accident countermeasure introduced in K-2/K-3 NPP. © 2016 IEEE.

Ahmed M.,Pakistan Atomic Energy Commission | Kuhlmann H.C.,Vienna University of Technology
Fluid Dynamics Research | Year: 2012

The linear stability of the two-dimensional steady flow in an infinite cavity with a right-angled triangular cross-section is investigated numerically by the finite-element method. We consider the case when one of the walls enclosing the right angle moves away from it. Neutral curves, eigenmodes and kinetic-energy production rates are computed. Five different instability modes are found, depending on the aspect ratio, i.e. the length ratio of the walls enclosing the right angle. The spatial structure of the kinetic-energy transfer between the basic flow and the critical modes indicates that three of the critical modes for very shallow cavities are due to an elliptic instability mechanism. Two other critical modes, for moderately shallow to deep cavities, arise due to a centrifugal mechanism. The instabilities found are discussed and compared with those arising in rectangular cavities. © 2012 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.

Imtiaz M.,Nuclear Institute of Agriculture | Rashid A.,Pakistan Atomic Energy Commission
Pakistan Journal of Botany | Year: 2010

The soils in Pakistan across 22 Mha cultivated area are predominantly alluvial and loessal, alkaline in pH, calcareous and low in organic matter. These factors are mainly responsible for nutrient fixation in soil and low availability to plants. Zinc (Zn) deficiency in Pakistan was the first micronutrient disorder recognised in early 1970s as a cause of hadda disease in rice. After identification of Zn deficiency, extensive research has been carried out during last four decades on micronutrient deficiencies in soils and their drastic effects on crops. Subsequently, field-scale deficiencies of zinc (Zn) boron (B) and iron (Fe) have been established in many field and horticultural crops. The most widespread deficiency is of Zn as 70% of the soils of Pakistan are Zn deficient and observed in rice, wheat, cotton, maize, sunflower, sugarcane, brassica, potato and in many other crops along with citrus and deciduous fruits. Boron deficiency is another major nutritional disorder which severely affects rice, cotton, wheat, sugarbeet, peanut, citrus and deciduous fruits. The third field-scale disorder is Fe chlorosis which has been exhibited in peanut, chickpea, cotton, citrus, ornamentals and many tree species. Copper (Cu) and manganese (Mn) deficiencies are of localized occurrence. The mineral elements like Zn, Fe and Cu are as crucial for human health as organic compounds such as carbohydrates, fats, protein and vitamins. The daily dietary intake of young adult ranges from 10-60 mg for Fe, 2-3 mg for Cu and 15 mg for Zn. Intake less than these values can cause slow physiological processes. These micronutrients deficiencies in soil are not only hampering the crop productivity but also are deteriorating produce quality. High consumption of cereal based foods with low contents of micronutrients is causing health hazards in humans. The contents of micronutrients in food can be elevated either by supplementation, fortification or by agricultural strategies i.e., biofortification and application of micronutrients containing fertilizers. Food fortification and supplementation are too expensive, not practical to be applied on large scale and not easily accessible to poor masses. The development of micronutrient efficient genotypes can be a successive tool to overcome the micronutrient disorders in soil and for improvement in human health. However, the harvesting of micronutrient enriched grains from field would mine out more micronutrients. The cultivation of these genotypes can be integrated with the application of micronutrients containing fertilizers. Addition of such fertilizers will not only correct the deficiencies but also improve the fruit size and quality of crops. In general, 2-5 kg Zn ha-1 may be adequate for improved crop production, however, soil applied Fe is generally ineffective except for Fe-sequestrine. Repeated sprays of Ferrous sulphate (FeSO4) or chelated Fe cure the chlorosis and improve the quality of food stuff. However, despite being highly cost effective, currently micronutrient use is negligible.

Iqbal M.S.,Forman Christian College | Khurshid S.J.,Pakistan Atomic Energy Commission | Muhammad B.,Hazara University
Medicinal Chemistry Research | Year: 2013

Mn(II)-, Fe(II)-, Co(II)-, Ni(II)-, and Zn(II)-Schiff base complexes containing anthranilic acid and aldoses as part of the base were prepared and characterized by microanalytical, thermogravimetric, and spectroscopic data. The complexes were found to be four-coordinate, anhydrous, and ML2 type. The spectral and magnetic data indicate a tetrahedral geometry for Mn(II) and Fe(II) complexes, and a planar geometry for Co(II), Ni(II), and Zn(II) complexes. Mn(II) and Zn(II) complexes showed a significant anti-inflammatory activity against kaolin-paw-edema. All the complexes exhibited selective inhibition of COX-2 in two different cell models. © 2012 Springer Science+Business Media, LLC.

Qadeer R.,Pakistan Atomic Energy Commission
Journal of Radioanalytical and Nuclear Chemistry | Year: 2013

The batch kinetics of ruthenium ions adsorption on activated charcoal has been investigated over a wide range of ruthenium ions concentration (0.05-0.40 g/L) at room temperature of 23 ± 1 C in 3 M HNO3 solution. The adsorption process of ruthenium ions proceeds via two stages: the first stage is rather fast, followed by slower one, indicative of boundary layer and intra-particle diffusion effects respectively. The mechanism of the adsorption is predominantly diffusion and the intra-particle diffusion played a significant role in rate determining, but it was not the only main rate determining step throughout the adsorption process. Both intra-particle and boundary layer diffusion seem significant in the rate controlling step. It was also observed that the adsorption of ruthenium ions adsorption process is best accounted for using pseudo second order kinetic model and the overall rate of adsorption process appears to be controlled by more than one step, namely the external mass transfer and intra-particle diffusion mechanism. Moreover, the adsorption of ruthenium ions obeys the Freundlich and the Langmuir isotherms in the concentration range studied. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Rauf W.,Pakistan Atomic Energy Commission | Brown J.M.,University of Oxford
Chemical Communications | Year: 2013

Several closely related palladium-catalysed reactions involve the addition of Pd-C across an alkene, and subsequent β-elimination of Pd-H to give a more substituted alkene. The Pd-C precursor, normally possessing an sp 2 carbon bound to palladium, can be formed in several different ways, leading to sub-classes of reaction based on a common principle and convergent outcomes. The reaction pathway can vary from simple to highly subtle depending on the nature of the reactants and the ligation of the catalyst. Mechanistic analysis provides results that elucidate the pathway and link the different reaction types. The identification of reactive intermediates by NMR, ES-MS and other spectroscopic techniques, or by less direct methods, is an integral part of the process. This Feature Article covers ligand-free palladium catalysis, including the contributions of the authors, and separates catalysis where ligands are involved into cationic and neutral pathways. © The Royal Society of Chemistry 2013.

Iqbal J.,Pakistan Atomic Energy Commission
Proceedings of the Institution of Civil Engineers: Structures and Buildings | Year: 2014

Structures, systems and components that are essential for the safe operation and shutdown of a nuclear power plant may be subject to a variety of impulsive loads. This paper presents an experimental and numerical evaluation of the influence of ground shock and airblast forces on the structural response of a 1:8 scale reactor containment structure founded on schist. The numerical model, including both free air and schist properties, was programmed and linked to finite-element software as its user-provided subroutines. The numerical and experimental scaled model results demonstrate good agreement with each other. The full-scale simulation of typical reactor containment was subjected to surface explosions through the developed relationship for structural response analysis. The proposed methodology can be employed to evaluate the blast response of a concrete shell type containment structure and to estimate the integrity of containment.

Li F.,CAS National Astronomical Observatories | Liang G.Y.,CAS National Astronomical Observatories | Bari M.A.,CAS National Astronomical Observatories | Bari M.A.,Pakistan Atomic Energy Commission | Zhao G.,CAS National Astronomical Observatories
Astronomy and Astrophysics | Year: 2013

Context. Sulfur emission lines in the soft X-ray and extreme-ultraviolet regions are observed in a variety of laboratory and astrophysical spectra. But accurate electron impact excitation data for S xiii for state-of-the-art NLTE spectral models are scarce. Aims. We calculated electron-impact excitation collision strengths and effective collision strengths of S xiii for transitions among the lowest-lying 98 fine-structure states 1s22lnl′ corresponding to principal quantum numbers n = 2,3,4. The effective collision strengths for these transitions were computed over a wide temperature range (log 10Te (K) = 4.53-7.53) for various astrophysical plasma conditions. Methods. We used the fully-relativistic parallel Dirac R-matrix code to calculate collision strengths. To generate target wavefunctions and energy levels for scattering calculations, we employed the GRASP0 multi-configuration Dirac-Fock code for states up to n = 5. Results. The wavefunctions are generated from 27 configurations - 1s22lnl′(n = 2,3,4,5) - giving rise to 166 jj energy levels. The collision and effective collision strengths among the lowest 98 fine-structure levels are compared with the previous theoretical calculations. The collision strengths for most transitions agree well at higher incident electron energies. Conclusions. The resonant contributions to effective collision strengths are most dominant at lower temperatures. © ESO, 2013.

Ashfaq M.,University of Guelph | Hebert P.D.N.,University of Guelph | Mirza J.H.,National Institute for Biotechnology and Genetic Engineering NIBGE | Khan A.M.,National Institute for Biotechnology and Genetic Engineering NIBGE | And 2 more authors.
PLoS ONE | Year: 2014

Background: Although they are important disease vectors mosquito biodiversity in Pakistan is poorly known. Recent epidemics of dengue fever have revealed the need for more detailed understanding of the diversity and distributions of mosquito species in this region. DNA barcoding improves the accuracy of mosquito inventories because morphological differences between many species are subtle, leading to misidentifications. Methodology/Principal Findings: Sequence variation in the barcode region of the mitochondrial COI gene was used to identify mosquito species, reveal genetic diversity, and map the distribution of the dengue-vector species in Pakistan. Analysis of 1684 mosquitoes from 491 sites in Punjab and Khyber Pakhtunkhwa during 2010-2013 revealed 32 species with the assemblage dominated by Culex quinquefasciatus (61% of the collection). The genus Aedes (Stegomyia ) comprised 15% of the specimens, and was represented by six taxa with the two dengue vector species, Ae. albopictus and Ae. aegypti, dominant and broadly distributed. Anopheles made up another 6% of the catch with An. subpictus dominating. Barcode sequence divergence in conspecific specimens ranged from 0-2.4%, while congeneric species showed from 2.3-17.8% divergence. A global haplotype analysis of disease-vectors showed the presence of multiple haplotypes, although a single haplotype of each dengue-vector species was dominant in most countries. Geographic distribution of Ae. aegypti and Ae. albopictus showed the later species was dominant and found in both rural and urban environments. Conclusions: As the first DNA-based analysis of mosquitoes in Pakistan, this study has begun the construction of a barcode reference library for the mosquitoes of this region. Levels of genetic diversity varied among species. Because of its capacity to differentiate species, even those with subtle morphological differences, DNA barcoding aids accurate tracking of vector populations. © 2014 Ashfaq et al.

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