Download or read book Role of Nuclear Grade Graphite in Controlling Oxidation in Modular HTGRs written by and published by . This book was released on 2014 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: The passively safe High Temperature Gas-cooled Reactor (HTGR) design is one of the primary concepts considered for Generation IV and Small Modular Reactor (SMR) programs. The helium cooled, nuclear grade graphite moderated core achieves extremely high operating temperatures allowing either industrial process heat or electricity generation at high efficiencies. In addition to their neutron moderating properties, nuclear grade graphite core components provide excellent high temperature stability, thermal conductivity, and chemical compatibility with the high temperature nuclear fuel form. Graphite has been continuously used in nuclear reactors since the 1940's and has performed remarkably well over a wide range of core environments and operating conditions. Graphite moderated, gas-cooled reactor designs have been safely used for research and power production purposes in multiple countries since the inception of nuclear energy development. However, graphite is a carbonaceous material, and this has generated a persistent concern that the graphite components could actually burn during either normal or accident conditions [,]. The common assumption is that graphite, since it is ostensibly similar to charcoal and coal, will burn in a similar manner. While charcoal and coal may have the appearance of graphite, the internal microstructure and impurities within these carbonaceous materials are very different. Volatile species and trapped moisture provide a source of oxygen within coal and charcoal allowing them to burn. The fabrication process used to produce nuclear grade graphite eliminates these oxidation enhancing impurities, creating a dense, highly ordered form of carbon possessing high thermal diffusivity and strongly (covalently) bonded atoms.
Download or read book Oxidation of Carbon at High Temperatures written by Howard G. Maahs and published by . This book was released on 1971 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Surface Area burnoff Correlation for the Steam graphite Reaction HTGR written by and published by . This book was released on 1977 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The oxidation of core graphite by steam of air represents a problem area of significant concern in safety analyses for the high temperature gas cooled reactor (HTGR). Core and core-support graphite integrity and strength deteriorate with oxidation of the graphite, and oxidation furthermore could affect the rate of fission product release under upset conditions. Consequently, modeling of core response during steam or air ingress conditions requires an expression for the rate of graphite interaction with those impurities. The steam--graphite reaction in particular is a complex interaction of mass transport within the graphite with chemi-sorption and reaction on accessible surfaces; experimental results from graphite to graphite are highly variable, and the description of the reaction is not yet completely consistent. A simple etch pit model relating surface area to burnoff has been proposed and shown to provide reasonable correlation with experimental data obtained from steam oxidation studies of nuclear grade H-327 graphite. Unaccounted differences between theory and experiment arise at burnoffs exceeding 3 to 5 percent. The model, while not complete nor comprehensive, is consistent with experimental observations of graphite oxidation by O2(air), CO2, or H2O, and could have some utility in safety analysis.
Download or read book Radiation Damage in Graphite written by J. H. W. Simmons and published by Elsevier. This book was released on 2013-10-22 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nuclear Energy, Volume 102: Radiation Damage in Graphite provides a general account of the effects of irradiation on graphite. This book presents valuable work on the structure of the defects produced in graphite crystals by irradiation. Organized into eight chapters, this volume begins with an overview of the description of the methods of manufacturing graphite and of its physical properties. This text then presents details of the method of setting up a scale of irradiation dose. Other chapters consider the effect of irradiation at a given temperature on a physical property of graphite. This book discusses as well the changes in dimensions produced by irradiation and the effects of irradiation on the mechanical properties of graphite. The final chapter deals with the accumulation of stored energy, which is one of the main problems caused by the irradiation of graphite in nuclear reactors. This book is a valuable resource for physicists and chemical physicists.
Download or read book Nuclear Graphite written by R. E. Nightingale and published by Academic Press. This book was released on 2013-10-02 with total page 566 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nuclear Graphite focuses on the development and uses of nuclear graphite, including machining practices, manufacture, nuclear properties and structure, radiation, and electrical resistance. The selection first discusses the applications of graphite in the nuclear industry, machining practices, and manufacture. Discussions focus on early, current, and future applications of graphite, impregnation, graphitization, purification, general machining techniques, and equipment and methods in the nuclear industry. The book then examines the structure and nuclear and properties of graphite. The text evaluates radiation-induced structural and dimensional changes; radiation effects on electrical and thermal properties; and radiation effects on mechanical properties. Topics include radiation effects on crystal structure, electrical resistance, thermoelectric power, magnetoresistance, coefficient of friction, irradiation under stress, and elastic moduli of nuclear graphite. The book also ponders on stored energy, annealing radiation effects, and gas-graphite systems. The selection is a dependable source of data for readers interested in the applications of nuclear graphite.
Download or read book Corrosion of Nuclear grade Graphites written by E. L. Fuller and published by . This book was released on 1992 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Inhibition of Oxidation in Nuclear Graphite written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Graphite is a fundamental material of high temperature gas cooled nuclear reactors, providing both structure and neutron moderation. Its high thermal conductivity, chemical inertness, thermal heat capacity, and high thermal structural stability under normal and off normal conditions contribute to the inherent safety of these reactor designs. One of the primary safety issues for a high temperature graphite reactor core is the possibility of rapid oxidation of the carbon structure during an off normal design basis event where an oxidizing atmosphere (air ingress) can be introduced to the hot core. Although the current Generation IV high temperature reactor designs attempt to mitigate any damage caused by a postualed air ingress event, the use of graphite components that inhibit oxidation is a logical step to increase the safety of these reactors. Recent experimental studies of graphite containing between 5.5 and 7 wt% boron carbide (B4C) indicate that oxidation is dramatically reduced even at prolonged exposures at temperatures up to 900°C. The proposed addition of B4C to graphite components in the nuclear core would necessarily be enriched in B-11 isotope in order to minimize B-10 neutron absorption and graphite swelling. The enriched boron can be added to the graphite during billet fabrication. Experimental oxidation rate results and potential applications for borated graphite in nuclear reactor components will be discussed.
Download or read book Effects of Oxidation on Oxidation Resistant Graphite written by and published by . This book was released on 2015 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Advanced Reactor Technology (ART) Graphite Research and Development Program is investigating doped nuclear graphite grades that exhibit oxidation resistance through the formation of protective oxides on the surface of the graphite material. In the unlikely event of an oxygen ingress accident, graphite components within the VHTR core region are anticipated to oxidize so long as the oxygen continues to enter the hot core region and the core temperatures remain above 400°C. For the most serious air-ingress accident which persists over several hours or days the continued oxidation can result in significant structural damage to the core. Reducing the oxidation rate of the graphite core material during any air-ingress accident would mitigate the structural effects and keep the core intact. Previous air oxidation testing of nuclear-grade graphite doped with varying levels of boron-carbide (B4C) at a nominal 739°C was conducted for a limited number of doped specimens demonstrating a dramatic reduction in oxidation rate for the boronated graphite grade. This report summarizes the conclusions from this small scoping study by determining the effects of oxidation on the mechanical strength resulting from oxidation of boronated and unboronated graphite to a 10% mass loss level. While the B4C additive did reduce mechanical strength loss during oxidation, adding B4C dopants to a level of 3.5% or more reduced the as-fabricated compressive strength nearly 50%. This effectively minimized any benefits realized from the protective film formed on the boronated grades. Future work to infuse different graphite grades with silicon- and boron-doped material as a post-machining conditioning step for nuclear components is discussed as a potential solution for these challenges in this report.
Download or read book Advances in High Temperature Gas Cooled Reactor Fuel Technology written by International Atomic Energy Agency and published by . This book was released on 2012-06 with total page 639 pages. Available in PDF, EPUB and Kindle. Book excerpt: This publication reports on the results of a coordinated research project on advances in high temperature gas cooled reactor (HTGR) fuel technology and describes the findings of research activities on coated particle developments. These comprise two specific benchmark exercises with the application of HTGR fuel performance and fission product release codes, which helped compare the quality and validity of the computer models against experimental data. The project participants also examined techniques for fuel characterization and advanced quality assessment/quality control. The key exercise included a round-robin experimental study on the measurements of fuel kernel and particle coating properties of recent Korean, South African and US coated particle productions applying the respective qualification measures of each participating Member State. The summary report documents the results and conclusions achieved by the project and underlines the added value to contemporary knowledge on HTGR fuel.
Download or read book Advances in Catalysis written by and published by Academic Press. This book was released on 1967-01-01 with total page 461 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Catalysis
Download or read book Thermal and Flow Design of Helium cooled Reactors written by Gilbert Melese and published by . This book was released on 1984 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt: This source book provides both an overview of gas-cooled reactors and a detailed look at the high-temperature gas-cooled reactor (HTGR). Taking a worldwide perspective, this book reviews the early development of the HTGR and explores potential future development and applications.
Download or read book Physics of High Temperature Reactors written by Luigi Massimo and published by Elsevier. This book was released on 2013-10-22 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: Physics of High-Temperature Reactors focuses on the physics of high-temperature reactors (HTRs) and covers topics ranging from fuel cycles and refueling strategies to neutron cross-sections, transport and diffusion theory, and resonance absorption. Spectrum calculations and cross-section averaging are also discussed, along with the temperature coefficient and reactor control. Comprised of 16 chapters, this book begins with a general description of the HTR core as well as its performance limitations. The next chapter deals with general considerations about HTR physics, including quantities to be determined and optimized in the design of nuclear reactors. Potential scattering and resonance reactions between neutrons and atomic nuclei are then considered, together with basic aspects of transport and diffusion theory. Subsequent chapters explore methods for solving the diffusion equation; slowing-down and neutron thermalization in graphite; HTR core design, fuel management, and cost calculations; and core dynamics and accident analysis. The final chapter describes the sequence of reactor design calculations. This monograph is written primarily for students of HTR physics who are preparing to enter the field as well as technologists of other disciplines who are working on the system.
Download or read book NUREG CR written by U.S. Nuclear Regulatory Commission and published by . This book was released on 1977 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Carbon Materials for Advanced Technologies written by T.D. Burchell and published by . This book was released on 1999-07-22 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study begins with a review of carbon materials, emphasizing structure and chemical bonding in various forms of carbon. It then goes on to discuss advanced technologies for the manufacture and modification of carbon-based materials and their practical applications.
Download or read book Advanced Energy Systems their Role in Our Future written by and published by . This book was released on 1984 with total page 854 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Energy for Hydrogen Production written by Karl Verfondern and published by Forschungszentrum Jülich. This book was released on 2007 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Status of and Prospects for Gas cooled Reactors written by International Atomic Energy Agency and published by . This book was released on 1984 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
