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AbstractAbstract
[en] The interplay between radiation-generated defects and dislocation networks leads to a variety of changes in mechanical properties and results in a detrimental effect on the structural reactor component lifetime. The present PhD work focuses on studying elementary and collective dislocation mechanisms in irradiated iron-based materials, by means of dislocation dynamics (DD) simulations. Evolutions of the radiation-induced defect microstructure are studied first. Namely, the 1D diffusion of interacting prismatic loops is analyzed using the stochastic dislocation dynamics approach, accounting for the elastic forces acting between the loops and the stochastic forces associated with ambient thermal fluctuations. It is found that the interplay between stochastic forces and internal degrees of freedom of loops, in particular the loop reorientation, strongly influences the observed loop dynamics, especially the reaction rates resulting in the elastic confinement of loops.The cross-slip effect on the dislocation/loop interactions is then examined using a specific initial configuration associated with the glide plane change of a screw dislocation source, due to a single and well defined cross-slip event. It is shown that cross-slip significantly affects the effective strength of dislocation/defect interactions and therefore, post-irradiation plastic strain spreading. Lastly, post-irradiation plastic strain spreading is investigated at the grain scale using segment-based dislocation dynamics simulations, accounting for the thermally activated (screw) dislocation slip and cross-slip mechanisms. It is shown that each simulated irradiation condition can be characterized by a specific 'Defect-Induced Apparent Straining Temperature shift' (ΔDIAT) level, reflecting the statistical evolutions of the effective dislocation mobility. It is found that the calculated ΔDIAT level closely matches the ductile to brittle transition temperature shift (ΔDBTT) associated with the corresponding, experimentally-observed defect size and number density. This ΔDIAT/ΔDBTT correlation can be explained based on plastic strain spreading arguments. (author)
[fr]
Ce travail est une contribution a l'etude de la degradation des proprietes mecaniques des materiaux metalliques irradies, dans le contexte de la production d'energie nucleaire. Cette these porte en particulier sur l'etude du comportement des dislocations dans les materiaux ferritiques irradies, a l'aide de simulations de dynamique des dislocations (DD). L'evolution de la microstructure des defauts d'irradiation est tout d'abord analysee a l'aide d'un code nodal (code NUMODIS). Le Chapitre 2 traite en particulier de la diffusion et l'interaction de boucles prismatiques, en utilisant la dynamique des dislocations dite 'stochastique'. Ces calculs reproduisent les forces d'interaction elastiques boucle/boucle et les forces stochastiques associees aux fluctuations thermiques ambiantes. Il est ainsi montre que la reorientation des boucles (tilt) a un fort effet sur leur dynamique, en ce qui concerne notamment le taux d'evolution du confinement elastique boucle/boucle. L'effet du glissement devie sur l'interaction entre dislocation/boucle est ensuite examine au Chapitre 3. Cette etude fait appel a une configuration initiale specifique, associee a un changement du plan de glissement d'une source de dislocation vis. De cette maniere, il est montre que le glissement devie reduit considerablement la resistance des defauts/obstacles. Cet effet confirme le role critique du glissement devie durant la deformation plastique post-irradiation. La deformation plastique post-irradiation est etudiee a l'echelle du grain, au Chapitre 4, a l'aide de simulations DD a base de segments (code TRIDIS). Ces simulations traitent les mecanismes de glissement devie et de glissement thermiquement active (vis). Chaque condition d'irradiation simulee peut etre caracterisee par un 'decalage de la temperature apparente induite par des defauts d'irradiation' (ΔDIAT). Cette quantite est proportionnelle aux evolutions statistiques de la mobilite effective des dislocations. Le ΔDIAT calcule est pratiquement equivalent au decalage de la temperature de transition fragile a ductile (ΔDBTT) obtenu experimentalement, pour une taille et densite de defauts d'irradiation donnee. Cette correlation ΔDIAT/ΔDBTT peut etre interpretee a partir de mecanismes de deformation plastique elementaires, faisant appel a la theorie des dislocationsOriginal Title
Fragilisation des aciers de cuve irradies: analyse numerique des mecanismes de plasticite a l'aide de simulations de dynamique des dislocations
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27 Sep 2019; 147 p; 275 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses; Mecanique des Solides
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Thesis/Dissertation
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Stringfellow, William T.; Komada, Tatsuyuki; Chang, Li-Yang
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (United States). Funding organisation: USDOE. Assistant Secretary for Environmental Management (United States)2004
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (United States). Funding organisation: USDOE. Assistant Secretary for Environmental Management (United States)2004
AbstractAbstract
[en] This research was conducted to investigate the feasibility of applying microbial biodegradation as a treatment technology for wastes containing radioactive elements and organic solvents (mixed wastes). In this study, we focused our efforts on the treatment of wastes generated by biomedical research as the result of purifying tritium labeled compounds by high-performance liquid chromatography (HPLC). These wastes are typically 80 percent water with 20 percent acetonitrile or methanol or a mixture of both. The objective was to determine the potential of using biodegradation to treat the solvent component of tritiated mixed waste to a concentration below the land disposal restriction standard (1mg/L for acetonitrile). Once the standard is reached, the remaining radioactive waste is no longer classified as a mixed waste and it can then be solidified and placed in a secure landfill. This investigation focused on treating a 10 percent acetonitrile solution, which was used as a non-radioactive surrogate for HPLC waste, in a bioreactor. The results indicated that the biodegradation process could treat this solution down to less than 1 mg/L to meet the land disposal restriction standard
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20 Apr 2004; 7 p; 7. International In Situ and On-Site Bioremediation Symposium; Orlando, FL (United States); 2-6 Jun 2003; BNR: WN0219060; AC02-05CH11231; Also available from OSTI as DE00886821; PURL: https://www.osti.gov/servlets/purl/886821-HDPQL3/
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ALCOHOLS, BETA DECAY RADIOISOTOPES, BETA-MINUS DECAY RADIOISOTOPES, CHEMICAL REACTIONS, CHROMATOGRAPHY, DECOMPOSITION, DISPERSIONS, HYDROGEN ISOTOPES, HYDROXY COMPOUNDS, ISOTOPES, LIGHT NUCLEI, LIQUID COLUMN CHROMATOGRAPHY, MATERIALS, NITRILES, NONAQUEOUS SOLVENTS, NUCLEI, ODD-EVEN NUCLEI, ORGANIC COMPOUNDS, ORGANIC NITROGEN COMPOUNDS, RADIOACTIVE MATERIALS, RADIOISOTOPES, REMEDIAL ACTION, SEPARATION PROCESSES, SOLVENTS, WASTES, YEARS LIVING RADIOISOTOPES
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Stringfellow, William T.; Komada, Tatsuyuki; Chang, Li-Yang
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (United States). Funding organisation: USDOE. Mixed waste program (United States)2004
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (United States). Funding organisation: USDOE. Mixed waste program (United States)2004
AbstractAbstract
[en] Approximately 10 percent of all radioactive wastes produced in the U. S. are mixed with hazardous or toxic chemicals and therefore can not be placed in secure land disposal facilities. Mixed wastes containing hazardous organic chemicals are often incinerated, but volatile radioactive elements are released directly into the biosphere. Some mixed wastes do not currently have any identified disposal option and are stored locally awaiting new developments. Biological treatment has been proposed as a potentially safer alternative to incineration for the treatment of hazardous organic mixed wastes, since biological treatment would not release volatile radioisotopes and the residual low-level radioactive waste would no longer be restricted from land disposal. Prior studies have shown that toxicity associated with acetonitrile is a significant limiting factor for the application of biotreatment to mixed wastes and excessive dilution was required to avoid inhibition of biological treatment. In this study, we demonstrate that a novel reactor configuration, where the concentrated toxic waste is drip-fed into a complete-mix bioreactor containing a pre-concentrated active microbial population, can be used to treat a surrogate acetonitrile mixed waste stream without excessive dilution. Using a drip-feed bioreactor, we were able to treat a 90,000 mg/L acetonitrile solution to less than 0.1 mg/L final concentration using a dilution factor of only 3.4. It was determined that the acetonitrile degradation reaction was inhibited at a pH above 7.2 and that the reactor could be modeled using conventional kinetic and mass balance approaches. Using a drip-feed reactor configuration addresses a major limiting factor (toxic inhibition) for the biological treatment of toxic, hazardous, or radioactive mixed wastes and suggests that drip-feed bioreactors could be used to treat other concentrated toxic waste streams, such as chemical warfare materiel
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15 Jun 2004; 33 p; AC02-05CH11231; Also available from OSTI as DE00877613; PURL: https://www.osti.gov/servlets/purl/877613-AEpe0d/
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AbstractAbstract
[en] Abstract Background: Metal oxide clusters are very important inorganic materials, which are widely used in catalytic reactions. And neutron scattering is an important technique for the study of the condensed matters and materials. Purpose: The aim is to study the dynamics of the polymer chain confined in metal oxide cluster molecules. Methods: Quasielastic neutron scattering technique is employed to measure the dynamics of the sample. A theoretical model, which assumes that the vibrational, translational and rotational motions are independent of each other, is used to analyze the neutron spectra. Results: The dynamics of the polymer chain confined in metal oxide cluster are highly restricted in space. The large-scale motion of the chain is greatly hindered. The rotations of the methyl group and methylene group are also slowed down. Conclusion: The metal oxide cluster exhibits ultra-confinement effect on the polymer chains. (authors)
Source
4 figs., 20 refs.; http://dx.doi.org/10.11889/j.0253-3219.2016.hjs.39.110502
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Journal Article
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Nuclear Techniques; ISSN 0253-3219;
; v. 39(11); [6 p.]

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AbstractAbstract
[en] The scattering amplitude of the geometric model is extended to a complex function, which is used to calculate the p-barp scattering at (s)/sup 1/2/ = 540 MeV. The model can fit the shape of the differential cross section and the position of the dip
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AbstractAbstract
[en] For smoothing and shaping the on-target laser patterns flexibly in high-power laser drivers, a scheme has been developed that includes a zoom lens array and two-dimensional smoothing by spectral dispersion (SSD). The size of the target pattern can be controlled handily by adjusting the focal length of the zoom lens array, while the profile of the pattern can be shaped by fine tuning the distance between the target and the focal plane of the principal focusing lens. High-frequency stripes inside the pattern caused by beamlet interference are wiped off by spectral dispersion. Detailed simulations indicate that SSD works somewhat differently for spots of different sizes. For small spots, SSD mainly smooths the intensity modulation of low-to-middle spatial frequency, while for large spots, SSD sweeps the fine speckle structure to reduce nonuniformity of middle-to-high frequency. Spatial spectra of the target patterns are given and their uniformity is evaluated.
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(c) 2011 Optical Society of America; Country of input: International Atomic Energy Agency (IAEA)
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AbstractAbstract
[en] We prepared samples with starting composition Ba8-Ge46-x-Cox (x=0, 4 and 6) by direct melting. These Ge-based compounds were characterized by X-ray diffraction and WDS, and we found two superconducting transitions at TC=10 and 4 K in the Co-free sample. Co-doping results in the suppression of TC to 7 K. The superconducting volume fraction also decreases with increasing Co-doping. For Co-doped samples, there is no 4 K superconducting transition. X-ray refinement shows that the compounds are mixtures of several phases. The dominant phase is diamond Ge, and we found no Ge-clathrate phases. Besides diamond Ge, there are also several weak diffractions from an unknown Ba-Ge phase, and most of them were indexed on the basis of a monoclinic unit cell. Diffraction peaks for Ba2Ge, BaGe, BaGe2, BaGe2O5, BaGeO3, Ba3GeO5, α-BaGeO3, BaGe2O5, Ba2Ge5O12, β-BaGeO3, Ba2GeO4 and BaGe4O9 were carefully searched for but not seen in the samples. For the Co-doped sample, besides the main diamond Ge phase, there is also a semiconducting phase CoGe2. With increasing Co content, the CoGe2 content increases. The WDS results agree with this result. The main phase composition for the Co-free sample is Ba0.01Ge99.9. We also discuss the origin of two superconducting transitions in Ge-based compounds
Source
7. M2SRIO: International conference on materials and mechanisms of superconductivity and high temperature superconductors; Rio de Janeiro (Brazil); 25-30 May 2003; S092145340400509X; Copyright (c) 2004 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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ALKALINE EARTH METAL COMPOUNDS, CARBON, COHERENT SCATTERING, CRYSTAL LATTICES, CRYSTAL STRUCTURE, DIFFRACTION, ELECTRIC CONDUCTIVITY, ELECTRICAL PROPERTIES, ELEMENTS, MATERIALS, MINERALS, NONMETALS, PHASE TRANSFORMATIONS, PHYSICAL PROPERTIES, SCATTERING, THERMODYNAMIC PROPERTIES, TRANSITION ELEMENT COMPOUNDS
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Bilayer-structured nanocomposite of Ag and crosslinked polyelectrolyte for the detection of humidity
Li, Yang; Wu, Taotao; Yang, Mujie, E-mail: liyang@zju.edu.cn2015
AbstractAbstract
[en] Nanocomposites of quaternized and crosslinked poly(4-vinylpyridine) (QC-P4VP) and silver nanoparticles were prepared by a two-step procedure, and characterized by Fourier-transform infrared spectroscopy, Ultraviolet–visible spectroscopy and scanning electron microscopy. Bilayer-structured humidity sensors based on the nanocomposites were fabricated, and the effects of the concentration of silver salt precursor and poly(4-vinylpyridine), the method for the reduction of silver salt, the deposition order of the sensitive layers and environmental temperature on the humidity sensing characteristics of the composite sensor have been examined at room temperature. The composite sensor exhibited low impedance under dry atmosphere due to the introduction of Ag nanoparticles, and could detect very low relative humidity (RH) (down to 1% RH) with good sensitivity (impedance change of 2000% from 1% to 30% RH). In addition, the composite sensor demonstrated very wide measuring range (1–98% RH), and revealed faster response and smaller hysteresis than the sensor based on QC-P4VP alone. The complex impedance spectra of the composite sensor in the environments with different RH levels were investigated to explore its humidity sensing mechanism. - Highlights: • Bilayer-structured nanocomposite of Ag and polyelectrolyte are facilely prepared. • Nanocomposite could measure humidity as low as 1% RH and show small hysteresis. • Nanocomposite is capable of detecting full-range humidity with high sensitivity
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S0254-0584(15)00025-5; Available from http://dx.doi.org/10.1016/j.matchemphys.2015.01.024; Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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AMBIENT TEMPERATURE, COMPOSITE MATERIALS, CROSS-LINKING, DEPOSITION, DETECTION, ELECTRICAL PROPERTIES, FOURIER TRANSFORM SPECTROMETERS, HUMIDITY, HYSTERESIS, LAYERS, NANOCOMPOSITES, NANOPARTICLES, NANOSTRUCTURES, POLYMERS, PRECURSOR, SCANNING ELECTRON MICROSCOPY, SENSITIVITY, SENSORS, SILVER, SPECTRA
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AbstractAbstract
[en] The microstructure and texture evolution of Fe–0.50%Mn non-oriented electrical steel during austenite (γ) to ferrite (α) transformation was studied following various processing conditions. The experimental results demonstrate that the γ→α transformation interface moves from the surface of sheets towards the inner part along the normal direction (ND) under a high temperature gradient in pure hydrogen atmosphere, hereafter calling the process as “directional” phase transformation. Driven by the anisotropic strain energy, the strong {100} textured columnar grains are obtained during the “directional” phase transformation in pure hydrogen atmosphere with a high flow rate. However, driven by the anisotropies of both strain energy and surface energy, the fine {100} and {110} textured columnar grains are developed in pure hydrogen atmosphere with a relatively low flow rate. By contrast, the transformation process is “global” when specimens are annealed in pure nitrogen atmosphere. As a consequence, a {111} texture with equiaxed grains is obtained. In addition, the effect of manganese (Mn) upon the surface oxidation behavior is investigated. - Highlights: • The various atmosphere conditions lead to the microstructure and texture evolution. • The γ→α transformation is “directional” in hydrogen and “global” in nitrogen. • {100} textured columnar grains are obtained at the high flow rate of hydrogen. • {100} and {110} textured columnar grains are obtained at a low flow rate of hydrogen. • A γ-fiber texture with equiaxed grains is obtained in “global” γ→α transformation
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S0304-8853(14)00855-5; Available from http://dx.doi.org/10.1016/j.jmmm.2014.09.033; Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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[en] In this paper, the effects of welding speed on the microstructures and mechanical properties of laser welded AZ61 magnesium alloy plates were investigated by microstructural observations, microhardness tests and tensile tests. The results show that the microstructure in the fusion zone consisted of fine α-Mg equiaxed dendrite crystals and dispersed β-Mg17Al12 particles. With an increase in welding speed, the sizes of α-Mg grains and β-Mg17Al12 particles in the fusion zone decreased and the volume fraction of β-Mg17Al12 particles increased. The ultimate tensile strength, yield strength and elongation of welded joint increased when the welding speed increased from 1800 mm min−1 to 2800 mm min−1. In addition, the average hardness value of fusion zone and heat-affected zone increased with the increase in welding speed
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S0921-5093(13)00484-X; Available from http://dx.doi.org/10.1016/j.msea.2013.04.093; Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing; ISSN 0921-5093;
; CODEN MSAPE3; v. 578; p. 303-309

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