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El Ouahdani S.,Abdelmalek Essaadi University | Boukhal H.,Abdelmalek Essaadi University | Erradi L.,Mohammed V University | Chakir E.,Universite Ibn Tofail | And 5 more authors.
Annals of Nuclear Energy | Year: 2016

A set of KRITZ-2 experiments light water moderated lattices with uranium oxide and mixed-oxide fuel rods, at room and elevated temperatures, performed in the early 1970's have been assessed. Using the MCNP6.1 code with the most recent cross section libraries: JENDL-4 and ENDF/B-VII.1, the critical experiments KRITZ: 2-1, KRITZ: 2-13, and KRITZ: 2-19 achieved in the Sweden reactor KRITZ were analyzed. We have used the ENDF/B-VII.1 data provided with the MCNP6.1.1 version in ACE format and the Makxsf utility to handle the data in the specific temperatures not available in the MCNP6.1.1 original data. The JENDL-4 evaluations were processed using NJOY99 (update 364) to the temperatures of interest. The detailed comparisons of the calculated and measured (Benchmark, 2005) effective multiplication factors and pin power distributions for UO2 and MOX fuelled cores presented in this work demonstrate a good agreement between calculation and measurements. The maximum deviation of the calculation from the experimental data for keff, is 0.58% (absolute value) obtained for the KRITZ 2:1 at 248.5 °C using ENDF/B-VII.1 data. To investigate better the influence of cross sections differences on the reactivity and temperature coefficient, we break down the infinite multiplication factor into its components using a pin cell model. Using this simple model we evaluated the temperature effect on the infinite multiplication factor and the effect on its components. We have also analyzed the temperature effect on the leakage by calculating the non leakage probability and the associated temperature coefficient. The overestimation of the calculated non-leakage probability values using JENDL-4 relatively to the calculated one using ENDF/B-VII.1 for all configurations and all temperatures can be explained by the overestimation of the absorptions in the JENDL-4 library especially in the resonance of the heavy nuclides. We can note that this discrepancy between the libraries decreases in hot conditions. For the reactivity temperature coefficient, our analysis has shown that the tendency of a negative error (overestimation by calculation of the absolute value of the RTC) usually observed when analyzing similar UO2 and MOX LWR lattices is confirmed. However, the level of the calculation error has been reduced significantly by using Monte Carlo modeling associated with the most recent nuclear data libraries. © 2015 Elsevier B.V. All rights reserved. Source


Bih L.,British Petroleum | Bih H.,British Petroleum | Amalhay M.,Direction Recherche and Developpement | Mossadik H.,Direction Recherche and Developpement | And 4 more authors.
Procedia Engineering | Year: 2014

As the increasing demands of compact and space-saving electronics, capacitors with high energy-storage density are eagerly desired. One of the greatest challenges in the development of new high energy density materials is to increase dielectric permittivity. In this present work, we present some first results relative to phosphate glasses, which could be used as the dielectric energy-storage materials to fabricate high energy density devices. They were prepared by means of rapid quenching method. DTA and X-ray diffraction analysis were used to control their vitreous states. Dielectric constant of the glasses was measured at the frequency from 1Hz to 1MHz under the testing temperature from 120 K to 360 K. The results indicated that some samples exhibit high dielectric properties. © 2014 The Authors. Source


Bih L.,British Petroleum | Bih H.,British Petroleum | Amalhay M.,Direction Recherche and Developpement | Mossadik H.,Direction Recherche and Developpement | And 4 more authors.
Procedia Engineering | Year: 2014

As the increasing demands of compact and space-saving electronics, capacitors with high energy-storage density are eagerly desired. One of the greatest challenges in the development of new high energy density materials is to increase dielectric permittivity. In this present work, we present some first results relative to phosphate glasses, which could be used as the dielectric energy-storage materials to fabricate high energy density devices. They were prepared by means of rapid quenching method. DTA and X-ray diffraction analysis were used to control their vitreous states. Dielectric constant of the glasses was measured at the frequency from 1Hz to 1MHz under the testing temperature from 120 K to 360 K. The results indicated that some samples exhibit high dielectric properties. © 2014 The Authors. Published by Elsevier Ltd. Source


Frank D.C.,Swiss Federal Institute of forest | Frank D.C.,University of Bern | Poulter B.,Montana State University | Poulter B.,CEA Saclay Nuclear Research Center | And 50 more authors.
Nature Climate Change | Year: 2015

The Earth's carbon and hydrologic cycles are intimately coupled by gas exchange through plant stomata. However, uncertainties in the magnitude and consequences of the physiological responses of plants to elevated CO 2 in natural environments hinders modelling of terrestrial water cycling and carbon storage. Here we use annually resolved long-term δ 13 C tree-ring measurements across a European forest network to reconstruct the physiologically driven response of intercellular CO 2 (C i) caused by atmospheric CO 2 (C a) trends. When removing meteorological signals from the δ 13 C measurements, we find that trees across Europe regulated gas exchange so that for one ppmv atmospheric CO 2 increase, C i increased by ∼0.76 ppmv, most consistent with moderate control towards a constant C i /C a ratio. This response corresponds to twentieth-century intrinsic water-use efficiency (iWUE) increases of 14 ± 10 and 22 ± 6% at broadleaf and coniferous sites, respectively. An ensemble of process-based global vegetation models shows similar CO 2 effects on iWUE trends. Yet, when operating these models with climate drivers reintroduced, despite decreased stomatal opening, 5% increases in European forest transpiration are calculated over the twentieth century. This counterintuitive result arises from lengthened growing seasons, enhanced evaporative demand in a warming climate, and increased leaf area, which together oppose effects of CO 2 -induced stomatal closure. Our study questions changes to the hydrological cycle, such as reductions in transpiration and air humidity, hypothesized to result from plant responses to anthropogenic emissions. © 2015 Macmillan Publishers Limited. Source


Sinouh H.,British Petroleum | Sinouh H.,Laboratore Of Chimie Des Materiaux Solides | Bih L.,British Petroleum | Azrour M.,British Petroleum | And 8 more authors.
Journal of Physics and Chemistry of Solids | Year: 2012

The glasses in the SrO-TiO2-P2O5 system were prepared by the conventional quenching route. The amorphous state of samples was verified by X-ray diffraction (XRD). Density, molar volume, micro-hardness, glass transition temperature (Tg), and crystallization temperature (Tc) parameters are determined for each glass. The results show that they depend strongly on the chemical compositions. The structure approach of the glasses is determined by using Infrared spectroscopy (IR). This investigation highlights that the glassy-matrix contains various phosphate structural units. The crystallization of the glasses by heat-treatments is performed and the crystallized phases Sr3P 4O13, TiP2O7, Sr(PO 3)2 are identified by XRD. The overall results are correlated to the glass structure and the nature of chemical bonds constituting the glass network. © 2012 Elsevier Ltd. Source

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