Oxidation and Hydrogen Uptake of ZIRLO Structural Components Irradiated to High Burn-Up PDF Download
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Author: D. Schrire
Publisher:
ISBN:
Category : Grid
Languages : en
Pages : 31
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Book Description
Good structural performance of the fuel assembly during irradiation is an indispensable requirement. Extension of licensed burnups demands continuous improvements, and more precisely on the design and processing of components made of zirconium alloys. Experience feedback on the assembly behaviour is necessary and continuous surveillance of the assemblies' performance is maintained through on site inspections and post irradiation examinations (PIE). For that purpose, two research programs have recently been performed which included PIE on selected pressurised water reactor (PWR) assembly components made of ZIRLO. In the first program, a 15 by 15 fuel assembly irradiated for four annual cycles in Ringhals 2 NPP was selected for PIE. Samples extracted from grid strap vanes, guide thimble, and guide thimble end to top nozzle joints were subjected to visual examinations and characterizations such as oxide layer thickness, orientation, and distribution of hydride precipitates and hydrogen content. In the second program, as extension of the irradiated material evaluation of 17 by 17 lead test assemblies (LTA) irradiated in Vandellós II NPP, outer grid strap vanes were removed from a normal operation three-cycle assembly and from a four-cycle LTA and sent to the hot cell laboratory for destructive examinations. One objective of this work was to analyse the behaviour of skeleton key parts at the end of their irradiation life. Special attention was paid to the performance of the guide thimble end to top nozzle joint. Another objective was to study the effect of an additional irradiation cycle on the oxide thickness, hydride precipitates distribution, hydrogen concentration, and hydrogen pickup fraction of ZIRLO grids. Furthermore, an analysis of the oxidation and hydrogen uptake contribution on ZIRLO grids growth was performed. The hot cell examination results are presented and evaluated in the paper.
Author: D. Schrire
Publisher:
ISBN:
Category : Grid
Languages : en
Pages : 31
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Book Description
Good structural performance of the fuel assembly during irradiation is an indispensable requirement. Extension of licensed burnups demands continuous improvements, and more precisely on the design and processing of components made of zirconium alloys. Experience feedback on the assembly behaviour is necessary and continuous surveillance of the assemblies' performance is maintained through on site inspections and post irradiation examinations (PIE). For that purpose, two research programs have recently been performed which included PIE on selected pressurised water reactor (PWR) assembly components made of ZIRLO. In the first program, a 15 by 15 fuel assembly irradiated for four annual cycles in Ringhals 2 NPP was selected for PIE. Samples extracted from grid strap vanes, guide thimble, and guide thimble end to top nozzle joints were subjected to visual examinations and characterizations such as oxide layer thickness, orientation, and distribution of hydride precipitates and hydrogen content. In the second program, as extension of the irradiated material evaluation of 17 by 17 lead test assemblies (LTA) irradiated in Vandellós II NPP, outer grid strap vanes were removed from a normal operation three-cycle assembly and from a four-cycle LTA and sent to the hot cell laboratory for destructive examinations. One objective of this work was to analyse the behaviour of skeleton key parts at the end of their irradiation life. Special attention was paid to the performance of the guide thimble end to top nozzle joint. Another objective was to study the effect of an additional irradiation cycle on the oxide thickness, hydride precipitates distribution, hydrogen concentration, and hydrogen pickup fraction of ZIRLO grids. Furthermore, an analysis of the oxidation and hydrogen uptake contribution on ZIRLO grids growth was performed. The hot cell examination results are presented and evaluated in the paper.
Author: Adrienn Baris
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
In light water reactors the fuel is encapsulated in Zr-based claddings that withstand the harsh environment (neutron bombardment, high temperature and water under pressure); without absorbing too many neutrons to sustain the chain reaction in the reactor core. Relatively high corrosion resistance of Zr is achieved when alloyed (e.g. with Sn, Fe, Cr, Ni, or Nb). Some elements form second phase particles (SPPs) and provide protection against rapid corrosion. The cladding undergoes compositional and microstructural changes, such as irradiation induced SPP dissolution. Zr oxidizes at the metal-oxide interface by diffusion of the oxidizing species through the oxide layer. Therefore, a protective inner barrier oxide is essential to prevent the metal from fast reaction with different species. Hydrogen is released as a by-product of the oxidation, and by the radiolysis of the coolant. If H enters the metal it precipitates as brittle Zr-hydrides degrading the cladding's mechanical properties. The H-uptake is a critical safety issue. Although, extensive literature is available on this topic, there are some aspects that need better understanding. Increasing H-uptake of certain cladding types at high burnups was reported. The causes are not yet fully understood. To better understand the causes of increased H-uptake at high burnups, an extremely high burnup cladding (9 cycle LK3/L Zircaloy-2) from boiling water reactor provided the basis of the study. The same type of cladding after different service times was examined revealing the compositional and microstructural evolution. Two types of cladding from pressurized water reactor with medium burnup were studied to separate the reactor- and alloy-specific parameters from the generic ones. FIB tomography was used for the 3D reconstructions of the microstructure; EPMA and ChemiSTEM for the micro- and nanometric chemical analysis. It is revealed that regardless of alloy- and reactor-type, crack-free oxide and the absence of large hydrides in the vicinity of the metal-oxide interface; undulated interface; and presence of SPPs are among the essential factors for the cladding's high performance. It is demonstrated that the oxidation of the hydrides at the metal-oxide interface induces crack formation in the oxide, reducing its protectiveness. High level of SPP dissolution, large hydride phases in the metal and high level of porosity in the oxide at the interface, straight metal-oxide interface, stoichiometric oxide, increased Ni concentration in the inner oxide, segregation of Fe, Ni, Sn and slightly Cr in the metal grain boundaries, Sn segregation at the interface oxide are identified as the causes of increased H-uptake of the LK3/L cladding at high burnups. Although all of these factors are present after 9 cycles, the cladding does not show extremely fast oxidation and H-uptake even beyond the designed service time.
Author: Holger Wiese
Publisher:
ISBN:
Category : High burnup
Languages : en
Pages : 34
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Book Description
The objective of this paper is to summarize the results of the latest observations performed at Paul Scherrer Institut on irradiated fuel claddings, to characterize their corrosion and hydrogen-uptake behavior. Two categories of studies have been performed. (1) A series of destructive tests were achieved on the fuel rods irradiated in a boiling-water reactor (BWR), including hydrogen concentration by hot-gas extraction. These results provided the hydrogen content of the cladding at different stages of irradiation, at different elevations along the rod. (2) Another series of examinations using a correlative microscopy method, i.e., using different techniques, including transmission electron microscopy (TEM), electron probe microanalysis (EPMA), and secondary ion mass spectrometry (SIMS), on the same material and in the same region of the metal-oxide interface have provided useful data regarding the oxide layer combining the signals from oxides and from hydrides. Furthermore, the effect of the type of alloying element has been examined for in-reactor oxidation. These studies are subsequently combined with the findings from out-of-pile studies, using techniques, such as neutron radiography, to confirm the in-reactor observations. Results have shown that: (i) the hydrogen pickup fraction varies at different conditions and could even decrease as the oxide thickness increases; (ii) the distribution of hydrogen in the cladding is usually inhomogeneous; (iii) the most determining parameter for hydrogen uptake seems to be the microstructure of the oxide, and the nature of the alloying element will influence to a certain extent this parameter; (iv) furthermore, the stress in the oxide layer can modify the crack distribution in the latter, cracks will in turn shorten the route for the hydrogen to access the metal. These results will be discussed as a contribution to the available knowledge about hydrogen uptake and will provide a global support for the models of the uptake phenomenon.
Author: VF. Urbanic
Publisher:
ISBN:
Category : Corrosion
Languages : en
Pages : 17
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Book Description
The in-reactor corrosion and hydrogen pickup of Zircaloy-2 and Zr-2.5Nb pressure tube materials are being studied in two test loops: a light water loop in the NRU research reactor, and a new heavy water loop in the Halden reactor. The complimentary test programs examine the corrosion behavior of small specimens as a function of fast neutron flux and fluence, temperature, water chemistry, and specimen pre-oxidation.
Author: David John Young
Publisher: Elsevier
ISBN: 008044587X
Category : Business & Economics
Languages : en
Pages : 593
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Book Description
The book is concerned with understanding the fundamental mechanisms of high temperature alloy oxidation. It uses this understanding to develop methods of predicting oxidation rates and the way they change with temperature, gas chemistry and alloy composition. The focus is on designing (or selecting) alloy compositions which provide optimal resistance to attack by corrosive gases. . Emphasises quantitative calculations for predicting reaction rates and the effects of temperature, oxidant activities and alloy compositions. . Uses phase diagrams and diffusion paths to analyse and interpret scale structures and internal precipitation distributions . Provides a detailed examination of corrosion in industrial gases (water vapour effects, carburisation and metal dusting, sulphidation) . Text is well supported by numerous micrographs, phase diagrams and tabulations of relevant thermodynamic and kinetic data . Combines physical chemistry and materials science methodologies.
Author: A. J. Mueller
Publisher:
ISBN:
Category : Ductility
Languages : en
Pages : 20
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Book Description
Microscopic examinations of advanced zirconium alloy cladding irradiated to burnups over 70 GWd/MTU have revealed de-lamination of surface layers of the thin oxide. The new observation is termed "oxide surface peeling" or OSP. Examinations have revealed the layered structure of the oxide. Metallographic examination revealed that the waterside oxide on different irradiated Zr alloy cladding had a layered structure similar to the autoclaved corrosion specimens examined earlier. However, the OSP observations discussed here apply only to irradiated cladding. OSP is not observed in autoclave corrosion. A featureless intact oxide sub-layer was present in the interior oxide at the metal/oxide interface for all alloys. On top of this featureless layer, there were additional sub-layers with fine circumferential fissures believed to be associated with the cyclic corrosion rate transitions. The number of sub-layers depended on the corrosion resistance of the alloy. Intermediate corrosion resistance alloy had many sub-layers forming an overall intermediate thickness oxide. Higher corrosion resistance alloys had fewer sub-layers on top of the barrier oxide layer. In some cases, small patches of the top surface layers of the thin oxide were peeled off because of radial cracks generated in the oxide layer caused by tensile stresses created by a hard pellet contact. Metallography of the underlying cladding showed that hydride localization was not associated with the oxide surface peeling; in contrast to previous experience on the low corrosion resistance older claddings, such as Zircaloy-4, where a major thickness fraction of the thick oxide extending to the underlying metal was removed ("spalled"). The oxide surface layer peeling does not lead to irradiated alloy ductility reduction or enhanced embrittlement. The impact of oxide surface peeling observations on fuel performance is discussed in the paper. For fuel designs with low margin against grid-to-rod fretting wear, OSP may reduce this margin further.
Author: Jonathan E. D. Hawes
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Mattias Thuvander
Publisher:
ISBN:
Category : Alloys
Languages : en
Pages : 25
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Book Description
The ability of a zirconium alloy to resist corrosion relies on a compromise between two opposing strategies. Minimizing the hydrogen pickup fraction (HPUF) by invoking metallic electron conduction in the barrier oxide results in rapid parabolic oxide growth. On the other hand, slow sub-parabolic barrier oxide growth, as reflected in rate limiting electron transport, may result in a high HPUF. The objective of the present study is to offer mechanistic insights as to how low concentrations of different alloying elements become decisive for the overall corrosion behavior. Combining atomistic microanalysis with first principles modeling by means of density functional theory, the speciation and redox properties of Fe and Ni towards hydrogen evolution are firstly explored. Complementary atom probe microanalysis at the metal-oxide interface provides evidence for Fe and Ni segregation to grain boundaries in Zircaloy-2 that propagates into the ZrO2 scale. Descriptors for how alloying elements in ZrO2 control electron transport as well as catalytic electron-proton recombination in grain boundaries to form H2 are determined by means of theory. The findings are generalized by further atomistic modeling, and are thus put in the context of early reports from autoclave experiments on HPUFs of zirconium with the alloying elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Nb. A shunting mechanism which combines inner and outer hydrogen evolution mechanisms is proposed. Properties of the transient zirconium sub-oxide are discussed. A plausible atomistic overall understanding emerges.
Author:
Publisher: Elsevier
ISBN: 0081028660
Category : Science
Languages : en
Pages : 4871
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Book Description
Materials in a nuclear environment are exposed to extreme conditions of radiation, temperature and/or corrosion, and in many cases the combination of these makes the material behavior very different from conventional materials. This is evident for the four major technological challenges the nuclear technology domain is facing currently: (i) long-term operation of existing Generation II nuclear power plants, (ii) the design of the next generation reactors (Generation IV), (iii) the construction of the ITER fusion reactor in Cadarache (France), (iv) and the intermediate and final disposal of nuclear waste. In order to address these challenges, engineers and designers need to know the properties of a wide variety of materials under these conditions and to understand the underlying processes affecting changes in their behavior, in order to assess their performance and to determine the limits of operation. Comprehensive Nuclear Materials, Second Edition, Seven Volume Set provides broad ranging, validated summaries of all the major topics in the field of nuclear material research for fission as well as fusion reactor systems. Attention is given to the fundamental scientific aspects of nuclear materials: fuel and structural materials for fission reactors, waste materials, and materials for fusion reactors. The articles are written at a level that allows undergraduate students to understand the material, while providing active researchers with a ready reference resource of information. Most of the chapters from the first Edition have been revised and updated and a significant number of new topics are covered in completely new material. During the ten years between the two editions, the challenge for applications of nuclear materials has been significantly impacted by world events, public awareness, and technological innovation. Materials play a key role as enablers of new technologies, and we trust that this new edition of Comprehensive Nuclear Materials has captured the key recent developments. Critically reviews the major classes and functions of materials, supporting the selection, assessment, validation and engineering of materials in extreme nuclear environments Comprehensive resource for up-to-date and authoritative information which is not always available elsewhere, even in journals Provides an in-depth treatment of materials modeling and simulation, with a specific focus on nuclear issues Serves as an excellent entry point for students and researchers new to the field
Author: V S Saji
Publisher: Elsevier
ISBN: 0857095803
Category : Technology & Engineering
Languages : en
Pages : 421
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Book Description
Corrosion is an expensive and potentially dangerous problem in many industries. The potential application of different nanostructured materials in corrosion protection, prevention and control is a subject of increasing interest. Corrosion protection and control using nanomaterials explores the potential use of nanotechnology in corrosion control.The book is divided into two parts. Part one looks at the fundamentals of corrosion behaviour and the manufacture of nanocrystalline materials. Chapters discuss the impact of nanotechnology in reducing corrosion cost, and investigate the influence of various factors including thermodynamics, kinetics and grain size on the corrosion behaviour of nanocrystalline materials. There are also chapters on electrodeposition and the corrosion behaviour of electrodeposited nanocrystalline materials. Part two provides a series of case studies of applications of nanomaterials in corrosion control. Chapters review oxidation protection using nanocrystalline structures at various temperatures, sol- gel and self-healing nanocoatings and the use of nanoreservoirs and polymer nanocomposites in corrosion control.With its distinguished editors and international team of expert contributors, Corrosion protection and control using nanomaterials is an invaluable reference tool for researchers and engineers working with nanomaterials in a variety of industries including, aerospace, automotive and chemical engineering as well as academics studying the unique protection and control offered by nanomaterials against corrosion. Explores the potential use of nanotechnology and nanomaterials for corrosion prevention, protection and control Discusses the impact of nanotechnology in reducing corrosion cost and investigates various factors on the corrosion behaviour of nanocrystalline materials Provides a series of case studies and applications of nanomaterials for corrosion control
