2,666 research outputs found
APOLLO3® CEA/DEN deterministic multi-purpose code for reactor physics analysis
No full textAPOLLO3® is a registered trademark of CEA.International audienceAPOLLO3® is a common project of CEA, AREVA and EDF for the development of a new generation code system for core physics analysis providing improved accuracy, flexible software architecture and high computation performances and taking into account both RandD and industrial application requirements. This paper presents the most important developments implemented in the deterministic APOLLO3® code, and their validation. APOLLO3® provides new capabilities from spectral aspect up to core calculations and a large panel of solvers adapted for different applications.This paper discusses the general architecture of the software platform, the data libraries, models of cross section self-shielding and solvers implemented in APOLLO3®. The last part of this paper describes the verification and the validation of that platform and examples of use cases PWR (Pressurized Water Reactor) and SFR (Sodium Fast Reactor) applications
1 and 2D Mineral Polyelectrolyte
No full textInternational audienceThe rich zoology of phase diagrams in the field of mineral/inorganic polyelectrolyte will be presented, whether they are (i) unidimensional with the highly flexible polyelectrolyte KPdPS4 and its self assembly (Sayetat et al, Angew. Chem.), NaNb2PS10 which forms nanotube structures (Camerel et al. Nanoletters), Li2Mo6Se6 which forms a nematic mesophase (Gabriel et al. Adv. Mater.) or (ii) bidimensional with the nematic structure of smectic clays nanosheet suspensions (Gabriel et al J. Phys. Chem.) or even the discovery of the first lamellar phase based on covalent nanosheets (Gabriel et al. Nature). This latter phase, presenting an exceptionnal hyperswelling behavior, so large that it enable light diffraction (unpublished results). Such a variety of behaviors makes of these polyelectrolyte solutions some very interesting models for the development of new theoretical approaches
Isotropic, Nematic and lamellar Phases in colloidal suspensions of Nanosheets studied by USAXS
No full textInternational audienceThe phase diagram of colloidal suspensions of electrically charged nanosheets, such as clays, in spite of their many industrial uses, is not yet understood either experimentally or theoretically. When the nanosheet diameter is very large (~ 100 nm – 1 µm), distinguishing the lamellar liquid-crystalline phase from a nematic phase with strong stacking local order, often called “columnar” nematic, is quite challenging. We show here that newly upgraded small-angle x-ray scattering (SAXS) beamlines at synchrotron radiation facilities provide high-resolution measurements which allow identifying both phases unambiguously, provided that single domains can be obtained. We investigated dilute (~ 0.1 vol%) aqueous suspensions of synthetic Sb3P2O143- nanosheets,1,2 with aspect ratio > 100, that self-organize into two distinct liquid-crystalline phases, sometimes coexisting in the same sample.3 Close examination of their x-ray diffraction patterns (Figure 1) and their reflection profiles in the directions perpendicular to the director demonstrates that these two mesophases are respectively a columnar nematic and a lamellar phase. In the latter, the domain size reaches up to ~ 20 µm, which means that each layer is made of ~ 600 to tens of thousands nanosheets depending on their size. Since the lamellar phase was only rarely predicted in suspensions of charged disks, our results show that these systems should be revisited by theory or simulations. The unexpected stability of the lamellar phase also suggests that the rims and faces of Sb3P2O143- nanosheets may have different properties, giving them a “patchy” particle character. Figure 1: SAXS patterns of the nematic (A) and lamellar phase (B). White arrows point to the nematic diffuse ring in A) and the lamellar reflections in B) where the inset shows the (001) reflection.[1] P. Davidson, J-C. P. Gabriel., Current Opinion Coll. Inter. Sci. 9, 377 (2005).[2] J.-C. P. Gabriel et al., Nature 413, 504 (2001) 508.[3] J.C.P. Gabriel et al, to be submitted (2018).* Author for Correspondence: [email protected]; [email protected]
Isotropic, Nematic, and Lamellar Phases in Colloidal Suspensions of Nanosheets
No full textInternational audienceThe phase diagram of colloidal suspensions of electrically charged nanosheets, such as clays, in spite of their many industrial uses, is not yet understood either experimentally or theoretically. When the nanosheet diameter is very large (~ 100 nm – 1 µm), distinguishing the lamellar liquid-crystalline phase from a nematic phase with strong stacking local order, often called “columnar” nematic, is quite challenging. We show here that newly upgraded small-angle x-ray scattering (SAXS) beamlines at synchrotron radiation facilities provide high-resolution measurements which allow identifying both phases unambiguously, provided that single domains can be obtained. We investigated dilute (~ 0.1 vol%) aqueous suspensions of synthetic Sb3P2O143- nanosheets,1,2 with aspect ratio > 100, that self-organize into two distinct liquid-crystalline phases, sometimes coexisting in the same sample.3 Close examination of their x-ray diffraction patterns (Figure 1) and their reflection profiles in the directions perpendicular to the director demonstrates that these two mesophases are respectively a columnar nematic and a lamellar phase. In the latter, the domain size reaches up to ~ 20 µm, which means that each layer is made of ~ 600 to tens of thousands nanosheets depending on their size. Since the lamellar phase was only rarely predicted in suspensions of charged disks, our results show that these systems should be revisited by theory or simulations. The unexpected stability of the lamellar phase also suggests that the rims and faces of Sb3P2O143- nanosheets may have different properties, giving them a “patchy” particle character. Figure 1: SAXS patterns of the nematic (A) and lamellar phase (B). White arrows point to the nematic diffuse ring in A) and the lamellar reflections in B) where the inset shows the (001) reflection.[1] P. Davidson, J-C. P. Gabriel., Current Opinion Coll. Inter. Sci. 9, 377 (2005).[2] J.-C. P. Gabriel et al., Nature 413, 504 (2001) 508.[3] J.C.P. Gabriel et al, to be submitted (2018).* Author for Correspondence: [email protected]; [email protected]
Evaluation of the concrete shield compositions from the 2010 criticality accident alarm system benchmark experiments at the cea valduc silene facility
No full textInternational audienceIn October 2010, a series of benchmark experiments were conducted at the French Commissariat a l'energie Atomique et aux energies Alternatives (CEA) Valduc SILENE facility. These experiments were a joint effort between the United States Department of Energy Nuclear Criticality Safety Program and the CEA. The purpose of these experiments was to create three benchmarks for the verification and validation of radiation transport codes and evaluated nuclear data used in the analysis of criticality accident alarm systems.This series of experiments consisted of three single-pulsed experiments with the SILENE reactor. For the first experiment, the reactor was bare (unshielded), whereas in the second and third experiments, it was shielded by lead and polyethylene, respectively. The polyethylene shield of the third experiment had a cadmium liner on its internal and external surfaces, which vertically was located near the fuel region of SILENE. During each experiment, several neutron activation foils and thermoluminescent dosimeters (TLDs) were placed around the reactor. Nearly half of the foils and TLDs had additional high-density magnetite concrete, high-density barite concrete, standard concrete, and/or BoroBond shields. CEA Saclay provided all the concrete, and the US Y-12 National Security Complex provided the BoroBond.Measurement data from the experiments were published at the 2011 International Conference on Nuclear Criticality (ICNC 2011) and the 2013 Nuclear Criticality Safety Division (NCSD 2013) topical meeting. Preliminary computational results for the first experiment were presented in the ICNC 2011 paper, which showed poor agreement between the computational results and the measured values of the foils shielded by concrete. Recently the hydrogen content, boron content, and density of these concrete shields were further investigated within the constraints of the previously available data. New computational results for the first experiment are now available that show much better agreement with the measured values
1 and 2D Mineral Polyelectrolyte: Synthesis, Structure, Properties and Applications
No full textInternational audienceIn this presentation I will present the very rich zoology that has been brought to light in the field of mineral/inorganic polyelectrolyte, whether they are (i) unidimensional with the highly flexible polyelectrolyte KPdPS 4 and its self assembly (Sayetat et al, Angew. Chem.), NaNb 2 PS 10 which self assemble to form nanotube structures (Camerel et al. Nanoletters), Li 2 Mo 6 Se 6 which forms a nematic mesophase (Gabriel et al. Adv. Mater.) or (ii) bidimensional with the demonstration of the nematic structure of smectic clays nanosheet suspensions (Gabriel et al J. Phys. Chem.) or even the discovery of the first lamellar phase based on covalent nanosheets in H 3 Sb 3 P 2 O 14 (Gabriel et al. Nature & PNAS). This latter phase, presenting an exeptionnal hyperswelling behavior, so large that it enable light diffraction (unpublished results).Such a variety of behaviors make of these polyelectrolyte solutions some very interesting models for the development of new theoritical approaches as well as potential applications.</div
1 and 2D mineral lyotropic materials, from discovery to applications
No full textInternational audienceand 2D mineral lyotropic materials, from discovery to applicationsIn this presentation I will present the very rich zoology that has been brought to light in the field of 1D and 2D mineral/inorganic lyotropic nano materials, whether they are (i) unidimensional with the highly flexible polyelectrolyte KPdPS4 and its self assembly (Sayetat et al, Angew. Chem.), NaNb2PS10 which self assemble to form nanotube structures (Camerel et al. Nanoletters), Li2Mo6Se6 which forms a nematic mesophase (Gabriel et al. Adv. Mater.) or (ii) bidimensional with the demonstration of the nematic structure of smectite clays nanosheet suspensions (Gabriel et al J. Phys.Chem.) or even the discovery of the first lamellar phase based on covalent nanosheets in H3Sb3P2O14 (Gabriel et al. Nature et PNAS 2018). This latter phase, presents an exeptionnal hyperswelling behavior, so large that it enables light diffraction. Such a variety of behaviors makes of these 1D and 2D inorganic nano materials suspensions/solutions some very interesting models for the development of new theoritical approaches. I will conclude on their possible uses and applications.</div
Force sensing strategy for the backdrivable and dexterous CEA hand
No full textConference of 2013 16th International Conference on Advanced Robotics, ICAR 2013 ; Conference Date: 25 November 2013 Through 29 November 2013; Conference Code:104529International audienceThis work presents torque control and force sensing strategies for the new dexterous CEA hand. It is only based on proprioceptive signals and does not rely on external force sensors. We primarily focus on the mechatronic design rationale of the robotic hand. A modular approach simplifies the complex hand assembly and permits to concentrate efforts on one basic unit which is replicated throughout the hand. An optimized mechanical design of this unit assures backdrivability through the whole mechanism, including actuators and transmission of movement to the joints. Based on this feature, external forces applied to the finger can be sensed at the motor level. Overall, this mechatronic design contributes to the improvement of manipulation skills of robotic hands, thanks to the combination of high performance mechanics, high sensitivity to external forces and torque control capability without using external force sensor. Experimental results confirm the validity of our design approach, which provides a highly integrated method for sensing the interacting force
2D nanosheet based lyotropic liquid crystals: from synthesis to structure and applications
No full textInternational audienceIn this presentation I will present the very rich zoology that has been brought to light in the field of 2D mineral/inorganic polyelectrolyte colloidal suspensions. Indeed, if one can produce such suspensions with sufficiently high concentration, some ordering can take place leading to lyotropic mesophases. We will give example of such bidimensional systems and results ranging from the demonstration of the nematic structure of smectic clays nanosheet suspensions (Gabriel et al J. Phys. Chem.) to the discovery of the first lamellar phase based on covalent nanosheets in H3Sb3P2O14 (Gabriel et al. Nature et PNAS 2018). Lamellar phases are very significant as they are the basis of life such as we know it, because they enable the essential requirement: liquid compartmentation,. This lamellar phase firther stricking property is its exeptionnal hyperswelling behavior, so large that it enable light diffraction enabling rare liquid opalescence.Such a variety of behaviors make of these 2D inorganic polyelectrolyte suspensions some very interesting models for the development of new theoritical approaches but enable also applications, some of which will be described (Desvaux, Ang. Chemie; Camerel, Nanoletters & Adv. Funct. Mater.)
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El Arte Hiperólico de Gabriel García Márquez
No full textThis thesis examines the fiction of the Columbian author Gabriel García Márquez, and focuses on hyperbole as a fundamental characteristic of Márquez's fiction. There is special interest in three aspects of his work: setting, people, and themes
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