Download or read book Hydride Reorientation in Zircaloy 4 Under Different States of Stress as Studied with In Situ X Ray Diffraction written by M. Nedim Cinbiz and published by . This book was released on 2018 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanisms of Hydride Reorientation in Zircaloy 4 Studied in Situ written by Arthur Motta and published by . This book was released on 2014 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zirconium hydride platelet reorientation in fuel cladding during dry storage and transportation of spent nuclear fuel is an important technological issue. Using an in situ x-ray synchrotron diffraction technique, the detailed kinetics of hydride precipitation and reorientation can be directly determined while the specimen is under stress and at temperature. Hydrided Zircaloy-4 dogbone sheet samples were submitted to various thermo-mechanical schedules, while x-ray diffraction data was continuously recorded. Post-test metallography showed that nearly full hydride reorientation was achieved when the applied stress was above 210 MPa. In general, repeated thermal cycling above the terminal solid solubility temperature increased both the reoriented hydride fraction and the connectivity of the reoriented hydrides. The dissolution and precipitation temperatures were determined directly from the hydride diffraction signal. The diffraction signature of reoriented hydrides is different than that of in-plane hydrides. During cooling under stress, the precipitation of reoriented hydrides occurs at lower temperatures than the precipitation of in-plane hydrides, suggesting that applied stress suppresses the precipitation of in-plane hydrides. The analysis of the elastic strains determined by the shift in position of hydride and zirconium diffraction peaks allowed following of the early stages of hydride precipitation. Hydride particles were observed to start to nucleate with highly compressive strain. These compressive strains quickly relax to smaller compressive strains within 30°C of the onset of precipitation. After about half of the overall hydride volume fraction is precipitated, hydride strains follow the thermal contraction of the zirconium matrix. In the case of hydrides precipitating under stress, the strains in the hydrides are different in direction and trend. Analyses performed on the broadening of hydride diffraction peaks yielded information on the distribution of strains in hydride population during precipitation and cooldown. These results are discussed in light of existing models and experiments on hydride reorientation.

Download or read book Hydride Platelet Reorientation in Zircaloy Studied with Synchrotron Radiation Diffraction written by Arthur T. Motta and published by . This book was released on 2011 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrogen ingress into zirconium alloy fuel cladding in light water reactors can degrade cladding performance as a result of the formation of brittle hydrides. In service, hydrides normally precipitate in the circumferential direction and are homogeneously distributed through the cladding thickness in ideal cases. However, temperature and stress gradients in the cladding can promote hydrogen redistribution. This hydrogen redistribution is responsible for the formation of hydride rims, dissolution, and reorientation of hydride precipitates and for the formation of brittle hydrides at stress concentration locations, all of which can reduce cladding resistance to failure. Thus, it is crucial to understand the kinetics of hydride dissolution and precipitation under load and at temperature. Studies of hydrogen behavior in zirconium alloys are normally performed post facto, which causes them to suffer both from a scarcity of data points and from the confounding effects of studying hydrides at room temperature that might be dissolved at higher temperature. In the current study, we have used synchrotron radiation diffraction to study the kinetics of hydride precipitation and dissolution in situ (under load and at temperature). Samples of hydrided Zircaloy-4 were examined in transmission by using 80 keV synchrotron radiation while undergoing heating and cooling in a furnace. Temperatures ranged from 20 to 550°C, and loads from 75 to 100 MPa were applied. The hydrides dissolved and reprecipitated in a different orientation when sufficiently high loads were applied. Through careful study of the intensities and full-width half maxima of the diffraction peaks as a function of time, load, and temperature, it was possible to identify the characteristic diffraction patterns for the reoriented hydrides so that the kinetics of dissolution, reprecipitation, and orientation of the hydrides could be followed. The analysis of the diffraction patterns allowed a detailed understanding of the kinetics of hydride evolution under temperature and stress, as presented in this work.

Download or read book The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components written by Manfred P. Puls and published by Springer Science & Business Media. This book was released on 2012-08-04 with total page 475 pages. Available in PDF, EPUB and Kindle. Book excerpt: By drawing together the current theoretical and experimental understanding of the phenomena of delayed hydride cracking (DHC) in zirconium alloys, The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components: Delayed Hydride Cracking provides a detailed explanation focusing on the properties of hydrogen and hydrides in these alloys. Whilst the emphasis lies on zirconium alloys, the combination of both the empirical and mechanistic approaches creates a solid understanding that can also be applied to other hydride forming metals. This up-to-date reference focuses on documented research surrounding DHC, including current methodologies for design and assessment of the results of periodic in-service inspections of pressure tubes in nuclear reactors. Emphasis is placed on showing how our understanding of DHC is supported by progress in general understanding of such broad fields as the study of hysteresis associated with first order phase transformations, phase relationships in coherent crystalline metallic solids, the physics of point and line defects, diffusion of substitutional and interstitial atoms in crystalline solids, and continuum fracture and solid mechanics. Furthermore, an account of current methodologies is given illustrating how such understanding of hydrogen, hydrides and DHC in zirconium alloys underpins these methodologies for assessments of real life cases in the Canadian nuclear industry. The all-encompassing approach makes The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Component: Delayed Hydride Cracking an ideal reference source for students, researchers and industry professionals alike.

Download or read book Hydride Reorientation in Zirconium Alloy Nuclear Fuel Cladding Studied Using Synchrotron Radiation written by Jennifer Anne Jarvis and published by . This book was released on 2010 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: During reactor operation, waterside corrosion of Zirconium alloy fuel cladding leads to hydrogen pickup. Hydrides platelets will normally precipitate circumferentially in the cladding. However, under temperature and load, the hydrides can reorient in the radial direction. These brittle radial hydrides can drastically reduce the ductility and the fracture toughness of the cladding. This work contains an in-situ study of hydride reorientation. Using synchrotron radiation from the Advanced Photon Source (APS) at Argonne National Laboratory, x-ray diffraction in transmission geometry was used to study a hydrogen-charged sample under mechanical and thermal load. The sample was rolled Zircaloy-2 with a hydrogen content of 96 wt.ppm. It was studied under a loading cycle with temperature cycling from 25 to 400°C and with an applied tensile stress of 100 MPa. Under two cycles of loading, partial reorientation was achieved. This diffraction data was used to perform an evaluation of the intensity, peak broadening, and peak shift of hydride peaks, in order to characterize the kinetics of reorientation. Additionally, the dissolution and precipitation temperatures were studied. Optical microscopy was used to compare the microstructure and hydride orientation before and after the experiment.

Download or read book Effect of Hydrogen on Mechanical Behavior of a Zircaloy 4 Alloy written by and published by . This book was released on 2005 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydride formation is one of the main degradation mechanisms of zirconium alloys in hydrogen-rich environments. When sufficient hydrogen is present, zirconium- hydride precipitates can be formed. Cracking of the brittle hydrides near a crack tip can initiate the growth of a crack leading to the premature failure of the material. Hydride formation is believed to be enhanced by the presence of residual or applied stresses. Therefore, the increase in the stress field ahead of a crack tip may promote precipitation of additional hydrides. In order to verify these phenomena, the effect of internal stresses on the zirconium-hydride-precipitate formation, and in turn, the influence of the hydrides on the subsequest intergranular strain evolution in a hexagonal-close-packed zircaloy-4 alloy were investigated, using neutron and x-ray diffraction. First, the evolution of intergranular strains in a zircaloy-4 was investigated in-situ, using neutron diffraction, to understand the deformation behavior at the microscopic length scale. A series of uniaxial tensile loads up to 500 MPa was applied to a round-bar tensile specimen in the as-received condition and the intergranular (hkl-specific) strains, parallel and perpendicular to the loading direction, were studied. The results provide a fundamental understanding of the anisotropic elastic-plastic deformation of the zirconium alloy under applied stresses. Then the hydride formation was examined by conducting qualitative phase mapping across the diameter of two tensile specimens charged with hydrogen gas for 1/2 hour and 1 hour, respectively. It was observed that the zirconium hydrides ([delta]-ZrH2) form a layer, in a ring shape, near the surface with a thickness of approximately 400 [mu]m. The hydrogen-charging effects on intergranular strains were investigated and compared to the as-received specimen. Second, spatially-resolved internal-strain mapping was performed on a fatigue pre-cracked compact-tension (CT) specimen using in-situ neutron diffraction under applied loads of 667 and d4,444 newtons, to determine the in-plane (parallel to the loading direction) and through-thickness (perpendicular to the loading direction) lattice-strain profiles around the crack tip. An increase in elastic lattice strains near the crack tip was observed with the increase in the applied stresses. The effect of hydrogen charging was also investigated on CT specimens electrochemically charged with hydrogen. X-ray diffraction results clearly showed the presence of zircomium hydrides on the surfaces of the specimen.

Download or read book Modeling Zirconium Hydride Precipitation and Dissolution in Zirconium Alloys written by Evrard Lacroix and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nuclear fuel cladding undergoes waterside corrosion during normal operating conditions in pressurized water reactors, whereby the zirconium (Zr) in the fuel cladding reacts with the oxygen present in water, creating zirconia (ZrO) and releasing hydrogen. Part of the hydrogen created by the corrosion reaction can be absorbed into the fuel cladding. Once in the cladding, hydrogen redistributes by solid state diffusion in the metal, in response to gradients of concentration, temperature and stress. Once the local hydrogen solubility is exceeded, zirconium hydride precipitates are formed.The precipitation of hydrides may impact the integrity of zirconium-based nuclear fuel cladding, both during normal operation and during extended dry storage. It is important to model hydrogen behavior accurately, so as to assess cladding properties both in reactor and during dry storage. This is because the cladding is the first containment barrier, which prevents fission products to be released into the primary circuit. For this reason, this study aims to first understand hydride precipitation and dissolution and then implement this understanding into a hydride precipitation and dissolution model. To this end, differential scanning calorimetry (DSC) and in-situ synchrotron X-ray diffraction experiments were used to study the precipitation and dissolution of hydrides in Zircaloy-4 under different thermo-mechanical conditions.Results showed that when hydrided samples were cooled at cooling rates above 1C/min the hydrogen content in solid solution decreased, following the Terminal Solid Solubility for Precipitation (TSSP) curve. However, when the samples were held at a fixed temperature for a long anneal, the hydrogen content in solid solution continued to decrease below the TSSP and approached the Terminal Solid Solubility for Dissolution (TSSD). This result suggests that TSSP is a kinetic limit and that a unique solubility limit, i.e. TSSD governs the equilibrium hydrogen concentration in solid solution. DSC was used to perform isothermal precipitation experiments, from which the hydride precipitation rate and the degree of precipitation completion were quantified between 280 and 350C for the first time. The data obtained was used to generate a TTT diagram for hydride precipitation in Zircaloy-4 showing that hydride precipitation is diffusion-controlled at low temperatures and reaction-controlled at high temperatures. The experimental precipitation rate was fitted using the Johnson-Mehl-Avrami-Kolmogorov model to obtain a value of the Avrami parameter of 2.56 (2.5 is the theoretical value for the growth of platelet-shaped precipitates). It was also possible to derive the precipitation activation energy of for each process. Because it was possible to separate hydride nucleation and hydride growth, it was possible to ascertain that if the hydrogen content in solid solution is greater than TSSP, precipitation occurs by hydride nucleation. In contrast, precipitation occurs by hydride growth as long as hydride platelets are present and the hydrogen content in solid solution is above TSSD. Hydride dissolution will take place if hydrides are present and the hydrogen content in solid solution is below TSSP. Using this new understanding of hydrogen precipitation and dissolution mechanisms, experiments were conducted at the Advanced Photon Source (APS) using high temperature change rates to measure hydride nucleation and dissolution kinetics. These observations and measurements were combined to existing theory to a model, entitled Hydride Growth, Nucleation, and Dissolution model (HNGD model) that can accurately simulate hydrogen behavior in Zircaloy fuel cladding and that shows a significant improvement on the model used in BISON.The development of such a model is the first step towards obtaining a model for the impact of the development of hydride microstructure on nuclear fuel cladding mechanical properties during normal operation and to address concerns over fuel handling during dry storage. The use and benchmarking of such a code can be used to justify a safe burnup extension of nuclear fuel, which would reduce the cost of nuclear energy in an increasingly competitive market.

Download or read book X ray Diffraction Studies on Zirconium and Zircaloy 2 written by Myra S. Feldman and published by . This book was released on 1961 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fundamental Experiments on Hydride Reorientation in Zircaloy written by Kimberly B. Colas and published by . This book was released on 2012 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanical Characterization of Zirconium Hydrides with High Energy X Ray Diffraction written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Zirconium and its alloys are of technical importance, finding application as a structural material in the nuclear industry. Engineering components fabricated from zirconium slowly pick-up hydrogen as a result of in-reactor corrosion, degrading the components mechanical properties as a brittle hydride phase forms. This dissertation applies high energy X-ray diffraction to directly measure the mechanical properties of zirconium hydrides in the bulk and at stress concentrations in zirconium alloys. The current study is presented as a manuscript format dissertation comprised of three manuscript chapters. Chapter 3 reports the in-situ loading of hydrided Zircaloy-2 and discusses hydride/Zircaloy-2 matrix interactions as a function of applied load. Chapter 4 reports the mechanical behavior at a fatigue pre-crack in un-hydrided Zircaloy-2, comparing the results to finite element and polycrystalline plasticity models of the crack tip. Chapter 5 reports the effect of hydrides on the notch tip strain field. The three manuscript chapters are followed by a general discussion in Chapter 6 and conclusions in Chapter 7.

Download or read book Predicting the Flow Stress of Zircaloy 4 Under In Reactor Accident Conditions written by Chi-Toan Nguyen and published by . This book was released on 2018 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: During loss-of-coolant accident (LOCA) and reactivity-initiated accident (RIA), nuclear fuel rods experience high heating rates that change the microstructure and properties of zirconium cladding materials. We sought to determine how different fast heating rates affect the kinetics of transformation and whether their consequences on the material yield stresses in the dual-phase region could be predicted. Phase fraction and texture of cold-rolled Zircaloy-4 were thus measured at fast heating rates similar to those experienced during LOCA and RIA by in situ high-energy synchrotron X-ray diffraction; the yield stress was also measured at different heating rates to the same dual-phase temperature by the electrical resistance method. A crystal plasticity finite-element model was used to simulate the flow stresses with the inputs of the measured phase fraction and texture. The model was calibrated using the flow stress at the heating rate of 10°C s-1 and used to predict the flow stress at the heating rate of 50°C s-1 at the same temperature. A significant shift of the ? transus temperature was identified for fast heating rates in the range of 10 to 100°C s-1. There was great similarity in texture at different heating rates. In the dual-phase temperature region, the ? texture was almost identical to the starting texture, and the ? texture was nearly random. Yield stresses of cold-rolled Zircaloy-4 decreased at a faster heating rate at the same temperature of 920°C. A good agreement was found between the experimental and predicted flow stress at different heating rates, indicating this methodology can potentially be used to predict flow behavior in a fast transient regime.

Download or read book X ray Studies of delta and epsilon Zirconium Hydrides written by W. L. Korst and published by . This book was released on 1962 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Statistical Analysis of Hydride Reorientation Properties in Irradiated Zircaloy 2 written by S. Valance and published by . This book was released on 2011 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: The orientation of hydrides in fuel cladding determines the anisotropic fracture behavior of Zircaloy and the failure modes of cladding tubes. Approach coupling experiments using the cladding tube deformation test and finite element analysis have successfully led to the quantification of the stress influencing reorientation of hydrides in unirradiated samples. An improved version of this procedure was applied to six samples of irradiated Zircaloy-2 from two different rods with three classes of thermo-mechanical loading. It was found that at medium maximum temperature, when no more than half of the hydrides were dissolved, the mechanical loading showed no measurable effect. When most of the hydrides were dissolved, the orientation and location of the hydrides depended strongly on the mechanical loading: The hydrides spatial location followed the hoop tensile stress. When the number of loading cycles was raised, the fraction of radial hydrides increased even for very low hoop tensile stress. The inner side of the cladding showed a marked depletion of hydrides whatever the size of the hoop stress. Since our test setup involved a tri-axial stress state, the possible influence of the other components of the stress tensor was evaluated. Through the use of a classical nucleation law, it was shown that for our test setup, the hoop stress was the important mechanical quantity. Therefore, the inner side depletion of hydrides may be attributed to three other factors: Residual stress, a memory effect, and a pumping effect by the inner liner.

Download or read book OBSERVATION AND MECHANISM OF HYDRIDE IN ZIRCALOY 4 AND LOCAL HYDRIDE RE ORIENTATION INDUCED BY HIGH PRESSURE AT HIGH TEMPERATURES written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrided Zircaloy-4 samples were produced by a gas charging method to desired amounts of hydrogen. For low hydrogen content samples, the hydrided platelets appear elongated and needle-like, orientated in the circumferential direction. Mechanical testing was carried out by the ring compression method at various temperatures. Samples with higher hydrogen concentration resulted in lower strain before fracture and reduced maximum load. The trend between temperature and ductility was also very clear: increasing temperatures resulted in increased ductility of the hydrided cladding. A single through-wall crack was observed for a hydrided sample having very high hydrogen concentration under ring compression testing. For samples having lower hydrogen concentrations, the fracture surfaces traversed both circumferential and radial directions, and for which voids were observed near the hydrides. Mechanical tests to study hydride reorientation in these samples are under way, and the results will be reported in the near future.

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 Metals Abstracts written by and published by . This book was released on 1988 with total page 1244 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Toward a Better Understanding of Dimensional Changes in Zircaloy 4 written by M. Blat-Yrieix and published by . This book was released on 2008 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: In pressurized water reactors, new operating conditions (higher burnup, new chemistry, etc.) can have an effect on the dimensional stability of the fuel assembly skeleton. Previous studies have shown that the fuel assembly growth is, among others parameters (free growth, creep), strongly driven by corrosion. Oxide layer and hydrides precipitation could both induce an increase of the dimensional parameters. The scope of the present study is, regardless of irradiation effect, to quantify and to understand the separate effects of hydrogen and oxide layers on the Zircaloy-4 dimensional changes. Experimental works have been performed in laboratory on stress relieved annealed (SRA) and recrystallized (RXA) Zircaloy-4 strips. First, the hydrogen impact on dimensional changes has been studied without the effect of the oxide layer. The measurements were performed at room temperature on strips previously pre-hydrided by the gaseous charging method. The hydrogen content of the samples was between 100 ppm and 2000 ppm. Results indicate a linear correlation between hydrogen content and length variation. RXA material is more affected by the hydrogen effect than the SRA material. Nevertheless, in comparison with data issued from out-of-reactor measurement, the impact of hydrides is not sufficient (with irradiation growth) to explain the post-irradiation examinations (PIE) results. To understand these differences, the oxide layer contribution must be quantified. Second, the impact of the oxide layer was therefore studied on RXA Zircaloy-4 strips. Corrosion tests have been performed in autoclave at 360°C in primary water (2 ppm Li-1000 ppm B-H2) on as-received and pre-hydrided materials. To obtain thicker oxide layer within a shorter duration, samples have been also oxidized in furnace at 415°C. Moreover, as no significant hydriding occurs during oxidation in air, we are able to characterize properly the specific effect of the oxide layer. As for hydrides' effect, an increase of strain is observed as the oxide thickness becomes thicker. The contributions of hydrides and oxide layer are then discussed with regard to the metallurgical properties of the alloy. Finally, all these results are compared with PIE observations. Free growth, hydride precipitation, and oxide thickness seem to be the three main parameters to explain the dimensional changes in Zircaloy-4 observed in reactor.