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Author: Jérom̂e Guterl Publisher: ISBN: 9781321870558 Category : Languages : en Pages : 119
Book Description
Plasma-material interactions might strongly affect plasma performances and life-time of future magnetic fusion devices. For example, retention and recycling of hydrogen isotopes in plasma-facing components (PFC) may lead to dynamics plasma-material interactions and significant accumulation of tritium in material. Understanding the multifaceted physics of hydrogen retention in PFC is thus crucial, but remains challenging due to the wide spectrum of retention processes on PFC surface (erosion, co-deposition, etc.) and in PFC bulk (trap sites, bubbles, etc.) induced by long-time exposure of PFC to high flux of energy and particles. In this context, we revisit in this work some aspects of the reaction-diffusion models used to describe retention of hydrogen implanted in material in fusion relevant. We first focus on the analysis of thermal desorption spectroscopy (TDS) experiments, showing that the evolution of hydrogen concentration in material during TDS experiments is usually quasi-static. An analytic description of thermal desorption spectra (TDSP) is then obtained in quasi-static regime and is used to highlight dependencies of TDSP on hydrogen retention parameters. The interpretation of Arrhenius plots to characterize hydrogen retention processes is then revisited. Moreover, it is shown that retention processes can be characterized using the shape of desorption peaks in TDSP, and that long desorption tails in TDSP can be used to estimate activation energy of diffusion of hydrogen in PFC. Hydrogen retention induced by a large number of different types of traps is examined next. A reaction-diffusion model of TDSP with a large number of types of traps is presented for the first time. The application of this model is illustrated on several experimental TDSP available in literature, which are consistently reproduced using several types of traps with a unique broad spectrum of detrapping energies. The values of these detrapping energies are shown to be in agreement with values predicted by density functional theory simulations when several hydrogen atoms are trapped in one material vacancy. Effects of surface processes on hydrogen retention and recycling are investigated in the second part. First, long-term outgassing of hydrogen from PFC during off-plasma events is considered. The super-diffusive power-law decay in time of the hydrogen outgassing flux is modeled with a revisited single trap reaction-diffusion model, showing that hydrogen outgassing is either surface-limited or diffusion-limited. The outgassing regime is shown to be governed either by processes in the bulk or on the surface of material. The influence of hydrogen concentration profiles in material on the power-law exponents is analyzed as well. Finally, the different models proposed in the literature to describe power-law decays of hydrogen outgassing flux experimentally observed during off-plasma events are reconciled. Hydrogen recombination and desorption on tungsten surface is investigated next using molecular dynamics (MD) and accelerated molecular dynamics simulations. Adsorption states, diffusion, hydrogen recombination into molecules, and clustering of hydrogen on tungsten surfaces are analyzed. It is shown that tungsten hydrogen interatomic potential, available in literature and used in MD simulations, cannot reproduce main features of hydrogen molecular recombination on tungsten surface. Hydrogen clustering on tungsten surface is nevertheless observed during MD simulations. Effects of hydrogen clustering on hydrogen desorption are thus analyzed by introducing a kinetic model describing the competition between surface diffusion, clustering and recombination. Different desorption regimes are identified, which reproduce some aspects of desorption regimes experimentally observed when tungsten surface is saturated with hydrogen.
Author: Jérom̂e Guterl Publisher: ISBN: 9781321870558 Category : Languages : en Pages : 119
Book Description
Plasma-material interactions might strongly affect plasma performances and life-time of future magnetic fusion devices. For example, retention and recycling of hydrogen isotopes in plasma-facing components (PFC) may lead to dynamics plasma-material interactions and significant accumulation of tritium in material. Understanding the multifaceted physics of hydrogen retention in PFC is thus crucial, but remains challenging due to the wide spectrum of retention processes on PFC surface (erosion, co-deposition, etc.) and in PFC bulk (trap sites, bubbles, etc.) induced by long-time exposure of PFC to high flux of energy and particles. In this context, we revisit in this work some aspects of the reaction-diffusion models used to describe retention of hydrogen implanted in material in fusion relevant. We first focus on the analysis of thermal desorption spectroscopy (TDS) experiments, showing that the evolution of hydrogen concentration in material during TDS experiments is usually quasi-static. An analytic description of thermal desorption spectra (TDSP) is then obtained in quasi-static regime and is used to highlight dependencies of TDSP on hydrogen retention parameters. The interpretation of Arrhenius plots to characterize hydrogen retention processes is then revisited. Moreover, it is shown that retention processes can be characterized using the shape of desorption peaks in TDSP, and that long desorption tails in TDSP can be used to estimate activation energy of diffusion of hydrogen in PFC. Hydrogen retention induced by a large number of different types of traps is examined next. A reaction-diffusion model of TDSP with a large number of types of traps is presented for the first time. The application of this model is illustrated on several experimental TDSP available in literature, which are consistently reproduced using several types of traps with a unique broad spectrum of detrapping energies. The values of these detrapping energies are shown to be in agreement with values predicted by density functional theory simulations when several hydrogen atoms are trapped in one material vacancy. Effects of surface processes on hydrogen retention and recycling are investigated in the second part. First, long-term outgassing of hydrogen from PFC during off-plasma events is considered. The super-diffusive power-law decay in time of the hydrogen outgassing flux is modeled with a revisited single trap reaction-diffusion model, showing that hydrogen outgassing is either surface-limited or diffusion-limited. The outgassing regime is shown to be governed either by processes in the bulk or on the surface of material. The influence of hydrogen concentration profiles in material on the power-law exponents is analyzed as well. Finally, the different models proposed in the literature to describe power-law decays of hydrogen outgassing flux experimentally observed during off-plasma events are reconciled. Hydrogen recombination and desorption on tungsten surface is investigated next using molecular dynamics (MD) and accelerated molecular dynamics simulations. Adsorption states, diffusion, hydrogen recombination into molecules, and clustering of hydrogen on tungsten surfaces are analyzed. It is shown that tungsten hydrogen interatomic potential, available in literature and used in MD simulations, cannot reproduce main features of hydrogen molecular recombination on tungsten surface. Hydrogen clustering on tungsten surface is nevertheless observed during MD simulations. Effects of hydrogen clustering on hydrogen desorption are thus analyzed by introducing a kinetic model describing the competition between surface diffusion, clustering and recombination. Different desorption regimes are identified, which reproduce some aspects of desorption regimes experimentally observed when tungsten surface is saturated with hydrogen.
Author: Ahmed Hassanein Publisher: Springer Science & Business Media ISBN: 9401004447 Category : Technology & Engineering Languages : en Pages : 237
Book Description
A compendium representing the current state of the art in the modelling, simulation and physics of the interaction of hydrogen and helium with plasma facing materials in fusion reactors. This is the topic that will determine the success of the production of energy by future Tokamak reactors and it is here discussed by the world's experts. Topics covered are recycling of hydrogen isotopes; wall fuelling and wall pumping; active control of hydrogen recycling; hydrogen and helium behaviour in solids and liquid metals; and databases for recycling.
Author: C.H. Wu Publisher: Springer Science & Business Media ISBN: 9401143315 Category : Technology & Engineering Languages : en Pages : 351
Book Description
One of the most important issues in the construction of future magnetic confinement fusion machines is that of the materials of which they are constructed, and one of the key points of proper material choice is the recycle of hydrogen isotopes with materials at the plasma face. Tritium machines demand high safety and economy, which in turn requires the lowest possible T inventory and smallest possible permeation through the plasma facing materials. The recycle behaviour of the in-vessel components must also be known if the plasma reaction is to predictable and controllable, and finally, the fuel cycle and plasma operating regimes may be actively controlled by special materials and methods. The book discusses both laboratory experiments exploring the basic properties of non-equilibrium hydrogen-solid systems (diffusion, absorption, boundary processes) and experimental results obtained from existing fusion machines under conditions simulating future situations to some extent. Contributions are from experts in the fields of nuclear fusion, materials science, surface science, vacuum science and technology, and solid state physics.
Author: Catalina Quiros lara Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Plasma facing components in fusion reactors are exposed to intense thermal loads, plasma disruptions and high-flux particle bombardment. This leads to a plasma wall interactionthat degrades the overall performance of the materials, limits the lifetime of the components and has a strong influence on the plasma performance. One problem derived from plasmawall interactions is bubble and blister formation in materials. This poses a great concern since it changes the material properties and favors hydrogen isotope (HI) retention. Since tritium, a HI, is radioactive, its inventory is quite limited. Experiments have shown that surface modifications are highly influenced by several parameters such incident ion energy,fluence and crystallographic orientation. This work focuses on analyzing blister and bubble dynamics due to hydrogen plasma exposure in materials with a cubic crystal system and alow hydrogen solubility (i.e. Al and W). This provides a suitable background to understand phenomena related to crystallographic structure in hexagonal systems such as beryllium. In order to perform the experiments, the samples were polished and submitted to a heat treat mentto obtain a well-defined low-roughness base material. Afterwards, they were exposedto a fully characterized hydrogen plasma in which several parameters were varied, such asincident ion energy, fluence and discharge regime. The latter was performed in order to studythe effects stress, relaxation and cooling have on bubble and blister formation given tha tcurrent plasma reactors work in cycles instead of continuous plasma exposure. In addition,the microstructure and crystallographic orientation of the materials was varied during the experiments. The analysis of crystallographic orientation were performed by using {100},{110} and {111} single crystals. This allows studying blister morphology without the effect of grain boundaries and setting the basis to understand hexagonal crystal systems. Finally, in order to understand hydrogen dynamics in materials a 1D macroscopic rate equations model with a code named Hydrogen Isotope Inventory Processes Code (HIIPC) was used. This model allows predicting the amount of retained HI's in materials and the physical processes involved in this interaction such as HI implantation, migration, depth distribution and their release. The results obtained with HIIPC support the results obtained in the experimental section and contribute in the understanding of hydrogen dynamics in material.
Author: Holm Altenbach Publisher: Springer ISBN: 3030116654 Category : Science Languages : en Pages : 525
Book Description
This book presents a collection of chapters on the current problems of the theory of dynamical processes in generalized continua and structures, and has been compiled to commemorate the 70th birthday of Prof. Dmitry Indeitsev – a leading specialist in the field of dynamical processes in solids, fluids and structures. It discusses various applications related to Prof. Indeitsev’s contributions, including various discrete and continuous dynamic models of structures and media, as well as a number of dynamical processes in generalized media.
Author: GARY S. WAS Publisher: Springer ISBN: 1493934384 Category : Technology & Engineering Languages : en Pages : 1014
Book Description
The revised second edition of this established text offers readers a significantly expanded introduction to the effects of radiation on metals and alloys. It describes the various processes that occur when energetic particles strike a solid, inducing changes to the physical and mechanical properties of the material. Specifically it covers particle interaction with the metals and alloys used in nuclear reactor cores and hence subject to intense radiation fields. It describes the basics of particle-atom interaction for a range of particle types, the amount and spatial extent of the resulting radiation damage, the physical effects of irradiation and the changes in mechanical behavior of irradiated metals and alloys. Updated throughout, some major enhancements for the new edition include improved treatment of low- and intermediate-energy elastic collisions and stopping power, expanded sections on molecular dynamics and kinetic Monte Carlo methodologies describing collision cascade evolution, new treatment of the multi-frequency model of diffusion, numerous examples of RIS in austenitic and ferritic-martensitic alloys, expanded treatment of in-cascade defect clustering, cluster evolution, and cluster mobility, new discussion of void behavior near grain boundaries, a new section on ion beam assisted deposition, and reorganization of hardening, creep and fracture of irradiated materials (Chaps 12-14) to provide a smoother and more integrated transition between the topics. The book also contains two new chapters. Chapter 15 focuses on the fundamentals of corrosion and stress corrosion cracking, covering forms of corrosion, corrosion thermodynamics, corrosion kinetics, polarization theory, passivity, crevice corrosion, and stress corrosion cracking. Chapter 16 extends this treatment and considers the effects of irradiation on corrosion and environmentally assisted corrosion, including the effects of irradiation on water chemistry and the mechanisms of irradiation-induced stress corrosion cracking. The book maintains the previous style, concepts are developed systematically and quantitatively, supported by worked examples, references for further reading and end-of-chapter problem sets. Aimed primarily at students of materials sciences and nuclear engineering, the book will also provide a valuable resource for academic and industrial research professionals. Reviews of the first edition: "...nomenclature, problems and separate bibliography at the end of each chapter allow to the reader to reach a straightforward understanding of the subject, part by part. ... this book is very pleasant to read, well documented and can be seen as a very good introduction to the effects of irradiation on matter, or as a good references compilation for experimented readers." - Pauly Nicolas, Physicalia Magazine, Vol. 30 (1), 2008 “The text provides enough fundamental material to explain the science and theory behind radiation effects in solids, but is also written at a high enough level to be useful for professional scientists. Its organization suits a graduate level materials or nuclear science course... the text was written by a noted expert and active researcher in the field of radiation effects in metals, the selection and organization of the material is excellent... may well become a necessary reference for graduate students and researchers in radiation materials science.” - L.M. Dougherty, 07/11/2008, JOM, the Member Journal of The Minerals, Metals and Materials Society.
Author: Jérom̂e Guterl
Author: Jérom̂e Guterl
Author: Ahmed Hassanein
Author: C.H. Wu
Author: Catalina Quiros lara
Author: 
Author: Yu-Hong Zhao
Author: Holm Altenbach
Author: 
Author: GARY S. WAS
Author: Graham Michael Wright