Experimental Determination of Phase Equilibria and Occupancies for CO2, CH4, and N2 Hydroquinone Clathrates

Hydroquinone (HQ) forms organic clathrates in the presence of various gas molecules in specific thermodynamic conditions. For some systems, clathrate phase equilibrium and occupancy data are very scarce or inexistent in literature to date. This work presents experimental results obtained for the CO2–HQ, CH4–HQ, and N2–HQ clathrates, in an extended range of temperature from about 288 to 354 K. Formation/dissociation pressures, and occupancies at the equilibrium clathrate forming conditions, were determined for these systems. Experiments showing the influence of the crystallization solvent, and the effect of the gas pressure on HQ solubility, were also presented and discussed. A good agreement is obtained between our experimental results and the already published experimental and modeling data. Our results show a clear dependency of the clathrate occupancy with temperature. The equilibrium curves obtained for CO2–HQ and CH4–HQ clathrates were found to be very close to each other. The results presented in this study, obtained in a relatively large temperature range, are new and important to the field of organic clathrates with potential impact on gas separation, energy storage, and transport

Spallation reactions. A successful interplay between modeling and applications

The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200 MeV deuterons and 400 MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. The same year R. Serber describes the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a worskhop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie

The GUINEVERE Project for Accelerator Driven System Physics

paper 9414International audienceThe GUINEVERE project is part of the EUROTRANS Integrated Project of the 6th EURATOM Framework Programme. It is mainly devoted to ADS on-line reactivity monitoring validation, sub-criticality determination and operational procedures (loading, start-up, shut-down, ...) as a follow-up of the MUSE experiments. The project consists in coupling a fast lead core, set-up in the VENUS reactor at SCK*CEN Mol (B), with a GENEPI neutron source under construction by CNRS. To accommodate the accelerator in a vertical coupling configuration, the VENUS building is being heightened. The fast core will be loaded with enriched Uranium and will be moderated and reflected with solid lead (zero power experiment). For the purpose of the experimental programme, the neutron source has to be operated not only in pulsed mode but also in continuous mode to investigate the current-to-flux reactivity indicator in representative conditions of a powerful ADS. In this latter mode it is also required to make short beam interruptions to have access to the neutron population decrease as a function of time: from this spectrum it will be possible to apply different analysis techniques such as "prompt decay" fitting techniques and "source jerk" techniques. Beam interruptions will be repeated at a programmable frequency to improve time spectra statistics. Different sub-criticality levels (keff=0.99, 0.97, 0.95, ...) will be investigated in order to obtain a full set of data points for the final overall validation of the methodology. This paper describes the status of the experimental facility assembling, and the foreseen experimental programme to be started

Influence of complex defect on cast AS7G06-T6 under multiaxial fatigue loading

cited By 3International audienceAS7G06-T6 cast aluminum alloy is tested under tension, torsion and tension-torsion fatigue loading for two load ratios. Basquin's law and step loading method are used to obtain the fatigue limit under multiaxial loading. Crossland criterion and principal stress criterion considering Goodman idea are compared to evaluate the multiaxial behavior. The influence of complex defects on fatigue limit is analyzed under multiaxial loadings. Several artificial defects are machined on fatigue specimen with different distance between edges. A new definition of the equivalent defect size considering the distance between defect edges is proposed. For both tension and tension-torsion fatigue, the competition between single natural defect and complex artificial defects is observed and analyzed. © 2014 Elsevier Ltd

Multiaxial fatigue design of cast parts: Influence of complex defect on cast AS7G06-T6

cited By 2International audienceAS7G06-T6 cast aluminum alloy is tested under tension, torsion and tension-torsion fatigue loading for two load ratios. Basquin's law and step loading method are used to obtain the fatigue limit under multiaxial loading. Crossland criterion and principal stress criterion considering Goodman idea are compared to evaluate the multiaxial behavior. The influence of complex defects on fatigue limit is analyzed under multiaxial loadings. Several artificial defects are machined on fatigue specimen with different distance between edges. A new definition of the equivalent defect size considering the distance between defect edges is proposed. For both tension and tension-torsion fatigue, the competition between single natural defect and complex artificial defects is observed and analyzed. © 2014 Elsevier Ltd

Influence of casting defects on the fatigue behavior of cast aluminum AS7G06-T6

cited By 23International audienceAS7G06-T6 cast aluminum alloy is tested under tension fatigue loading for two load ratios. After the quantification of the Secondary Dendrite Arm Spacing (SDAS) and grain size of the material, fatigue tests are analyzed through fractographic Scanning Electron Microscope (SEM) observations in order to reveal the type of defects at the origin of the failure. The quantification of the defect size is performed for each defect and Kitagawa type diagrams are produced for each load ratio. It is shown that the critical defect size that does not lower the fatigue strength is close to the grain size of the material. The Defect Stress Gradient (DSG) approach that aims to simulate defect influence on the fatigue strength is presented in a multiaxial context. DSG approach is finally implemented in a finite element simulation of a structural component in order to show that such an approach can provide a defect size map. The latter can be used to define allowable defect size for industrial components. © 2014 Elsevier Ltd. All rights reserved

GUINEVERE: Construction of a Zero-Power Pb ADS at Mol

International audienceThe GUINEVERE project is running since 2007 and is part of the EUROTRANS Integrated Project of the 6th EURATOM Framework Programme. It consists first in the construction of a lead fast ADS mock-up at SCK-CEN Mol (Belgium) for the purpose of ADS subcriticality monitoring experiments, and beyond in support to the design of a Transmutation Experimental Facility (MYRRHA/FASTEF). To do so the VENUS reactor (SCK-CEN) will be coupled with a new GENEPI neutron source under construction by CNRS (France). To accommodate this new source (a 250 keV deuteron accelerator) in a vertical coupling configuration, the VENUS building is being heightened. In parallel the reactor core is being modified to be loaded with fuel assemblies made of enriched Uranium and solid Lead moderator pins, and hold radial and axial Lead reflectors. A new safety and control rod system is also under development. The new GENEPI-3C neutron source is designed to be operated in pulsed mode but also in continuous mode to investigate the current-to-flux reactivity indicator in representative conditions of a powerful ADS. In this latter mode it will be also possible to make short beam interruptions at a fixed frequency to have access to the neutron population decrease as a function of time. The vertical beam line will have the distinctive feature to be retractile, allowing target changing or complete removal (for critical configuration for example). The accelerator will be first completely assembled at LPSC Grenoble for beam characterization before to be transferred in Mol. We will present in this paper the status of this experimental facility assembling, and foreseen experimental programmes in the framework of fast transmutation system studies