Download or read book Oxide Characteristics and Their Relationship to Hydrogen Uptake in Zirconium Alloys written by BD. Warr and published by . This book was released on 1991 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM) have been used to investigate composition and structure of oxides on pure zirconium and Zr-2.5Nb following both in and out-reactor exposures in aqueous and gaseous environments. Thin oxides formed in steam at 400°C on Zr-2.5Nb act as excellent hydrogen permeation barriers for CANadian Deuterium Uranium (CANDU) pressure tubes. Following up to 4350 effective full power days (EFPD) exposure in-reactor in the annulus gas, and out-reactor elevated exposures to deuterium gas, these oxides generally continue to show diffusional-type through-thickness deuterium concentration profiles, with negligible deuterium contents at the metal/oxide interface. Diffusion coefficients inferred from these profiles are as low as ~2 x 10-22m2/s at 300°C. The structure of these thin oxides on Zr-2.5Nb consists of columnar grains with amorphous regions at grain boundaries and at the metal oxide interface, and non-interconnected porosity, which implies that deuterium permeation is likely controlled by solid state diffusion through the bulk oxide. At regions containing relatively high deuterium contents in the bulk metal of removed pressure tubes, outside surface oxides showed several regions with flat deuterium concentration profiles with higher deuterium concentrations at the metal/oxide interface. Examination of thicker oxides with interconnected porosity, on pure Zr, following exposures to pure deuterium gas, also showed the presence of flat deuterium concentration profiles. This would tend to suggest that regions of high deuterium concentration dissolved in the base metal of pressure tubes may also contain oxides with interconnected porosity.
Download or read book Toward a Comprehensive Mechanistic Understanding of Hydrogen Uptake in Zirconium Alloys by Combining Atom Probe Analysis With Electronic Structure Calculations written by Mattias Thuvander and published by . This book was released on 2014 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Zirconium in the Nuclear Industry written by George P. Sabol and published by ASTM International. This book was released on 1996 with total page 907 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Zirconium in the Nuclear Industry written by Craig M. Eucken and published by ASTM International. This book was released on 1991 with total page 794 pages. Available in PDF, EPUB and Kindle. Book excerpt: The proceedings of the Ninth International Symposium on [title], held in Kobe, Japan, November 1990, address current trends in the development, performance, and fabrication of zirconium alloys for nuclear power reactors. the bulk of the most recent work on zirconium alloy behavior has concerned corr
Download or read book Zirconium in the Nuclear Industry Tenth International Symposium written by A. M. Garde and published by ASTM International. This book was released on 1994 with total page 805 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of the Hydrogen Uptake Mechanism in Zirconium Alloys written by MB. Elmoselhi and published by . This book was released on 1994 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrogen uptake in zirconium alloy CANDU (CANada Deuterium Uranium) pressure tubes and other core components is controlled by the rate of transport of atomic/ionic species across the oxide film. The importance of understanding the mechanism of transport stems from the need to predict and control the rate of uptake. Samples of Zr-2.5Nb and Zircaloy-2 were prefilmed in steam (H2O, 400°C at 2 MPa) and subsequently exposed to D2O (10-3 Pa to 18 MPa) and D2 (10-3 Pa) at a temperature range of 250 to 380°C in the laboratory. Samples from Zr-2.5Nb pressure tubes removed from CANDU power reactors were also examined. Hydrogen mobility in oxides was investigated by secondary ion mass spectroscopy (SIMS) following these exposures. Diffusional-type through-oxide-thickness deuterium profiles have been observed adjacent to the oxide-metal interface for samples exposed to environments containing D2O for 4 h out-reactor and up to 10 years in-reactor. These profiles probably represent the density of accessible sites on surfaces of intergranular porosity through-thickness. Although, in small regions observed by transmission electron microscopy (TEM) such porosity has not been found. Nevertheless, from observations of grain size, sufficient sites would be available to produce deuterium concentration observed near oxide surfaces. The observed deuterium concentration profiles appear to result predominantly from deuteroxyl groups bonded to such sites. Deuterium content at the oxide-metal interface provides an indication of the extent of interfacial intergranular porosity. High deuterium contents at the interface may imply local regions with absent oxide barrier at the interface. In the presence of sufficient D2O, the oxide is continually healed, and deuterium uptake is relatively low where short-circuit routes such as intermetallics in Zircaloy-2 are not present. In environments with relatively high D2:D2O ratios, deuterium atoms may diffuse through the oxide to the interface and react directly with the metal resulting in high deuterium uptake rates. It is proposed that observed deuterium profiles may be the sum of mainly two components. The predominant component is due to deuteroxyl groups residing on accessible sites on surfaces of intergranular porosity with no direct link to hydrogen uptake by the bulk alloy. The second masked component would be due to another mobile hydrogen species (for example, H) that is diffusing to the bulk alloy. Further work is needed to substantiate the proposed hypothesis that would include exposures with varying D2:D2O ratios and further TEM examination.
Download or read book Hydrogen Absorption in Zircaloy During Aqueous Corrosion written by E. Hillner and published by . This book was released on 1964 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Zirconium in the Nuclear Industry written by Gerry D. Moan and published by ASTM International. This book was released on 2002 with total page 891 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annotation The 41 papers of this proceedings volume were first presented at the 13th symposium on Zirconium in the Nuclear Industry held in Annecy, France in June of 2001. Many of the papers are devoted to material related issues, corrosion and hydriding behavior, in-reactor studies, and the behavior and properties of Zr alloys used in storing spent fuel. Some papers report on studies of second phase particles, irradiation creep and growth, and material performance during loss of coolant and reactivity initiated accidents. Annotation copyrighted by Book News, Inc., Portland, OR.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1975 with total page 1090 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oxide Characteristics and Corrosion and Hydrogen Uptake in Zr 2 5 Nb CANDU Pressure Tubes written by MA. Maguire and published by . This book was released on 1996 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxides on removed pressure tubes from Pickering Unit 3 after 13.4 effective full power years (EFPY) have been examined to investigate the cause of variability in bulk alloy deuterium contents in outlet regions in order to improve predictions and minimize deuterium uptake in operating CANDU reactors. Secondary ion mass spectroscopy (SIMS) and electrochemical impedance spectrometry (EIS) were used for characterization with minimal sample preparation and modification. Two SIMS techniques were used for quantification: (1) the relative sensitivity factor (RSF) method, which requires a reference material and is subject to matrix effects as a result of variation in the secondary ion intensities of a species when different materials are sputtered; and (2) the SIMS infinite velocity (IV) method, which circumvents matrix effects by extrapolating all secondary ion intensity data to infinite velocity. A novel 13C oxide dating technique was used to determine oxide growth kinetics and ensure that oxide spalling had not occurred in the regions examined.
Download or read book Increased Hydrogen Uptake of Zirconium Based Claddings at High Burnup written by Adrienn Baris and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Tribology Design written by Mark Hadfield and published by WIT Press. This book was released on 2010 with total page 305 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Tribology and Design Conference explores the role of technology and design in the broader sense. It brings together colleagues from different disciplines interested in problems of surface interaction and design. The applications covered range from geomechanics to nano problems and from sustainability issues to advanced materials. It has never been so important for the designer to consider product and system durability in relation to reliability and sustainability issues. The topics for discussion also cover studies of tribology in nature and how the resulting lessons can be applied by the designers. Another important theme is the application of tribology in biomechanics, a field in which surface mechanics in general is of fundamental importance. This book contains the papers presented at the Third International Conference, arranged into the following subject areas: Design Tools; Test Methods; Surface Engineering; Tribology under Extreme Conditions; Surface Measurements & Lubrication.
Download or read book Mechanism of oxidation and hydrogen uptake in zirconium alloys written by B. Cox and published by . This book was released on 1985 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results from bundle rotation pressure drop measurements at aeclec spel have been analysed to determine the advantage of aligning junctions on fuel string pressure drop. design features that give minimum aligned pressure drops are identified. further bundle rotation pressure drop tests are recommended, and the goal for the cge bundle alignment techniques study is defined.
Download or read book Zirconium in the Nuclear Industry written by George P. Sabol and published by ASTM International. This book was released on 2000 with total page 953 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reactor Materials written by and published by . This book was released on 1966 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Materials in Nuclear Energy Applications written by C.K. Gupta and published by CRC Press. This book was released on 2018-05-04 with total page 239 pages. Available in PDF, EPUB and Kindle. Book excerpt: The text combines an account of scientific and engineering principles with a description of materials and processes of importance in nuclear research and industry. The coverage includes fuel materials, control and shileding materials, and so on - in fact, for most of the important pasts of a reactor.
Download or read book Results of the commissioning bundle test QUENCH L0 performed under LOCA conditions 2 aktualis Aufl written by Stuckert, J. and published by KIT Scientific Publishing. This book was released on 2014-09-05 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
