Microbeam X-Ray Absorption Near-Edge Spectroscopy of Alloying Elements in the Oxide Layers of Irradiated Zircaloy-2 PDF Download
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Author: Aditya P. Shivprasad Publisher: ISBN: Category : Zirconium alloys Languages : en Pages : 31
Book Description
Hydrogen pickup of zirconium-based fuel cladding and structural materials during in-reactor corrosion can degrade fuel components because the ingress of hydrogen can lead to the formation of brittle hydrides. In the boiling water reactor (BWR) environment, Zircaloy-2 fuel cladding and structural components such as water rods and channels can experience accelerated hydrogen pickup, whereas Zircaloy-4 components exposed to similar conditions do not. Because the principal difference between the two alloys is that Zircaloy-2 contains nickel, accelerated hydrogen pickup has been hypothesized to result from the presence of nickel. However, an understanding of the mechanism by which this acceleration occurs is still lacking. We investigated the link between hydrogen pickup and the oxidation behavior of alloying elements when incorporated into the oxide layers formed on zirconium alloys when corroded in the reactor. Synchrotron radiation microbeam X-ray absorption near-edge spectroscopy (XANES) at the Advanced Photon Source was performed on carefully selected BWR-corroded Zircaloy-2 water rods at an assembly-averaged burnup ranging from 32.8 to 74.6 GWd/MTU to determine the oxidation states of alloying elements, such as iron and nickel, within the oxide layers as a function of distance from the oxide-metal interface at high burnup. Samples were chosen for comparison based on having similar oxide thicknesses, processing, elevation, reactors, and fluences but different hydrogen pickup fractions. Examinations of the oxide layers formed on these samples showed that (1) the oxidation states of these alloying elements changed with distance from the oxide-metal interface, (2) these elements exhibited delayed oxidation relative to the host zirconium, and (3) nickel in Zircaloy-2 remained metallic in the oxide layer at a longer distance from the oxide-metal interface than iron. An analysis of these results showed an apparent correlation between the delayed oxidation of nickel and higher hydrogen pickup of Zircaloy-2 at high burnup.
Author: Aditya P. Shivprasad Publisher: ISBN: Category : Zirconium alloys Languages : en Pages : 31
Book Description
Hydrogen pickup of zirconium-based fuel cladding and structural materials during in-reactor corrosion can degrade fuel components because the ingress of hydrogen can lead to the formation of brittle hydrides. In the boiling water reactor (BWR) environment, Zircaloy-2 fuel cladding and structural components such as water rods and channels can experience accelerated hydrogen pickup, whereas Zircaloy-4 components exposed to similar conditions do not. Because the principal difference between the two alloys is that Zircaloy-2 contains nickel, accelerated hydrogen pickup has been hypothesized to result from the presence of nickel. However, an understanding of the mechanism by which this acceleration occurs is still lacking. We investigated the link between hydrogen pickup and the oxidation behavior of alloying elements when incorporated into the oxide layers formed on zirconium alloys when corroded in the reactor. Synchrotron radiation microbeam X-ray absorption near-edge spectroscopy (XANES) at the Advanced Photon Source was performed on carefully selected BWR-corroded Zircaloy-2 water rods at an assembly-averaged burnup ranging from 32.8 to 74.6 GWd/MTU to determine the oxidation states of alloying elements, such as iron and nickel, within the oxide layers as a function of distance from the oxide-metal interface at high burnup. Samples were chosen for comparison based on having similar oxide thicknesses, processing, elevation, reactors, and fluences but different hydrogen pickup fractions. Examinations of the oxide layers formed on these samples showed that (1) the oxidation states of these alloying elements changed with distance from the oxide-metal interface, (2) these elements exhibited delayed oxidation relative to the host zirconium, and (3) nickel in Zircaloy-2 remained metallic in the oxide layer at a longer distance from the oxide-metal interface than iron. An analysis of these results showed an apparent correlation between the delayed oxidation of nickel and higher hydrogen pickup of Zircaloy-2 at high burnup.
Author: Kimberly Colas Publisher: ISBN: Category : Zirconium oxide Languages : en Pages : 30
Book Description
The corrosion process (oxidation and hydriding) of zirconium alloy fuel cladding is one of the limiting factors on fuel rod lifetime, particularly for Zircaloy-4. The corrosion rate of this alloy shows indeed a great acceleration at high burnup in light water reactors (LWRs). Understanding the corrosion behavior under irradiation for this alloy is an important technological issue for the safety and efficiency of LWRs. In particular, understanding the effect of irradiation on the metal and oxide layers is a key parameter in the study of corrosion behavior of zirconium alloys. In this study, Zircaloy-4 samples underwent helium and proton ion irradiation up to 0.3 dpa, forming a uniform defect distribution up to 1 ?m deep. Both as-received and precorroded samples were irradiated to compare the effect of metal irradiation to that of oxide layer irradiation. After irradiation, samples were corroded to study the impact of irradiation defects in the metal and in preexisting oxide layers on the formation of new oxide layers. Synchrotron X-ray microdiffraction and microfluorescence were used to follow the evolution of oxide crystallographic phases, texture, and stoichiometry both in the metal and in the oxide. In particular, the tetragonal oxide phase fraction, which has been known to play an important role in corrosion behavior, was mapped in both unirradiated and irradiated metals at the submicron scale and appeared to be significantly affected by irradiation. These observations, complemented with electron microscopy analyses on samples in carefully chosen areas of interest, were combined to fully characterize changes caused by irradiation in metal and oxide phases of both alloys.
Author: X. Iltis Publisher: ISBN: Category : Alloying element redistribution Languages : en Pages : 23
Book Description
To understand the acceleration of the Zircaloy corrosion kinetics in PWR conditions, TEM microstructural characterizations of oxide layers grown in an autoclave or directly in-reactor have been performed. To separate the influence on the oxidation process of the irradiation damage in the alloy from the dynamic effect of neutron flux, oxide layers have also been grown in an autoclave on previously neutron-irradiated cladding. The comparative characterization of these oxide layers leads to the following results: the nucleation and growth process are observed to be similar on oxides formed in-autoclave and significantly different on oxides grown directly in-reactor, indicating that this process is essentially affected by neutron irradiation or, more generally, parameters specific to the reactor environment. Concerning grain growth phenomena, it appears that the high microstructural instability noticed in oxides formed in-reactor is also the consequence of parameters specific to the reactor environment such as neutron irradiation or the lithium concentration gradient. Finally, the iron distribution in the oxide is almost the direct image of the iron distribution in the metal.
Author: Gerry D. Moan Publisher: ASTM International ISBN: 0803128959 Category : Nuclear fuel claddings Languages : en Pages : 891
Book Description
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.
Author: A. T. Motta Publisher: ISBN: Category : Corrosion Languages : en Pages : 21
Book Description
To understand how alloy chemistry and microstructure impact corrosion performance, oxide layers formed at different stages of corrosion on various model zirconium alloys (Zr-xFe-yCr, Zr-xCu-yMo, for various x, y) and control materials (pure Zr, Zircaloy-4) were examined to determine their structure and the connection of such structure to corrosion kinetics and oxide stability. Microbeam synchrotron radiation diffraction and fluorescence of oxide cross sections were used to determine the oxide phases present, grain size, and orientation relationships as a function of distance from the oxide-metal interface. The results show a wide variation of corrosion behavior among the alloys, in terms of the pretransition corrosion kinetics and in terms of the oxide susceptibility to breakaway corrosion. The alloys that exhibited protective behavior at 500°C also were protective during 360°C corrosion testing. The Zr-0.4Fe-0.2Cr model ternary alloy showed protective behavior and stable oxide growth throughout the test. The results of the examination of the oxide layers with microbeam X-ray diffraction show clear differences in the structure of protective and nonprotective oxides both at the oxide-metal interface and in the bulk of the oxide layer. The nonprotective oxide interfaces show a smooth transition from metal to oxide with metal diffraction peaks disappearing as the monoclinic oxide peaks appear. In contrast, the protective oxides showed a complex structure near the oxide-metal interface, showing peaks from Zr3O suboxide and a highly oriented tetragonal oxide phase with specific orientation relationships with the monoclinic oxide and the base metal. The same interfacial structures are observed through their diffraction signals in protective oxide layers formed during both 360°C and 500°C corrosion testing. These diffraction peaks showed much higher intensities in the samples from 500°C testing. The results for the various model alloys are discussed to help elucidate the role of individual alloying elements in oxide formation and the influence of oxide microstructure on the corrosion mechanism.
Author: AT. Motta Publisher: ISBN: Category : Alloying elements Languages : en Pages : 21
Book Description
We have conducted a study of second phase particles and matrix alloying element concentrations in zirconium alloys using synchrotron radiation from the Advanced Photon Source (APS) at Argonne National Laboratory. The high flux of synchrotron radiation delivered at the 2BM beamline, compared to conventional X-ray generators, enables the detection of very small precipitate volume fractions. We detected the standard C14 hep Zr(Cr,Fe)2 precipitates (the stable second phase in Zircaloy-4) in the bulk material at a cumulative annealing parameter as low as 10-20 h, and we followed the kinetics of precipitation and growth as a function of the cumulative annealing parameter (CAP) in the range 10-22 (quench) to 10-16 h. In addition, the unique combination of spatial resolution and elemental sensitivity of the 2ID-D/E microbeam line at the Advanced Photon Source at Argonne (APS) allows study of the alloying element concentrations at ppm levels in an area as small as 0.2 X 0.3 ?m. We used X-ray fluorescence induced by this sub-micron X-ray beam to determine the concentration of these alloying elements in the matrix as a function of alloy type and thermal history. We discuss these results and the potential of synchrotron radiation-based techniques for studying zirconium alloys.
Author: JY. Ren Publisher: ISBN: Category : Irradiation Languages : en Pages : 8
Book Description
Experimental investigation of irradiation growth on annealed Zircaloy-4 and 20% to 50% cold-worked Zr-2.5wt%Nb specimens with stress relief has been carried out. The specimens are irradiated in a heavy water reactor at 610 K to 4.2 x 1024 n/m2 (E > 1.0 MeV). The growth strains increase linearly with fluence. The saturation of growth is not observed for all specimens. The difference of growth behavior between two kinds of Zircaloy-4 tube may be associated with the content of minor alloying elements and impurities that influence the microstructure evolution under irradiation.
Author: Sousan Abolhassani Publisher: ISBN: Category : Materials Languages : en Pages : 31
Book Description
This paper provides the results of investigations by transmission electron microscopy (TEM) on the selected materials from in-reactor oxidation tests in the Halden test reactor (Reference No. IFA-638) from 1998 to 2006. The objective of the IFA-638 test was to study the corrosion behavior of modern zirconium-based claddings to high burnup in pressurized water reactor water chemistry and thermal hydraulic conditions. The aim of this paper is to report on the microstructure of selected materials (ZIRLO®, E635, and Alloy A) after the irradiation to different burnup levels to determine the modifications induced by irradiation and to correlate results to their oxidation behavior. The TEM examinations revealed the nature of secondary phase particles (SPPs) and their modification under irradiation. Four types of SPPs were observed, namely ?-niobium precipitates, Zr0.5Nb0.3Fe0.2 (mainly in the ZIRLO alloy), Zr(Fe,Nb)2 (in E635), and (Cr,Fe)2Zr,Nb with varying niobium content (present in Alloy A: Zr-0.58Sn-0.31Nb-0.36Fe-0.26Cr). TEM observations showed that all three materials contained still several precipitates after irradiation and in the case of the ZIRLO alloy even after high burnups. Furthermore, the analysis of the metal side of the interface and its comparison with the oxide side led to the conclusion that all types of precipitates dissolved to some extent under irradiation and that their alloying element content decreased. The dissolution was intensified in the oxide. However, a more detailed examination showed that the ?-niobium precipitates dissolved at a slower rate, or knowing that their composition was much richer in niobium, the time needed for the precipitates to become fully depleted from niobium was longer. Regarding the amorphization under irradiation, the ?-niobium- and chromium-containing precipitates did not amorphize in the metal part of the interface. This was not the case for the other types of precipitates. Furthermore, these two types of SPP both showed delayed oxidation and due to this behavior the typical crack above the SPP in the oxide was also observed. These results are discussed to gain an improved understanding of the oxidation behavior of materials studied as a function of irradiation and residence time.
Author: Aditya P. Shivprasad
Author: Aditya P. Shivprasad
Author: Myra S. Feldman
Author: Kimberly Colas
Author: Kurt F. J. Heinrich
Author: X. Iltis
Author: Gerry D. Moan
Author: A. T. Motta
Author: AT. Motta
Author: JY. Ren
Author: Sousan Abolhassani