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: Cyril A. Migdal Publisher: ASTM International ISBN: 0803134932 Category : Antioxidants Languages : en Pages : 929
Book Description
This work presents papers from a December 2005 symposium held in Norfolk, Virginia, and sponsored by ASTM Committee D2 on Petroleum Products and Lubricants and its Subcommittees D02.09 on Oxidation and D02.C0 on Turbine Oils. Contributors include equipment manufacturers, end users, lubricant producers, lubricant additive suppliers, test equipment manufacturers, and standard test method developers. They share information on industry trends, evolving technologies, and changing equipment designs and operating conditions, with a focus on how these factors impact oxidation. Some topics covered include turbine oil performance limits, a new form of the rotating pressure vessel oxidation test, and degradation mechanisms leading to sludge and varnish in modern turbine oil formulations. B&w photos are included. There is no subject index. Migdal is affiliated with Chemtura Corporation.
Author: D. Pêcheur Publisher: ISBN: Category : Amorphization Languages : en Pages : 19
Book Description
Intermetallic precipitates are known to play a critical role in the oxidation process of Zircaloys. Since under irradiation they undergo structural changes, a specific study was conducted to analyze whether these transformations modify the oxidation behavior of the Zircaloy-4. Oxidation kinetics in autoclave were measured on reference, ion irradiated, and neutron irradiated materials. In the case of ion-irradiated samples, the oxidation kinetics are changed, while in the case of neutron-irradiated cladding, no significant change is observed after 60 days of oxidation. The behavior of reference and irradiated precipitates during the growth of these oxide layers was analyzed using analytical scanning transmission electron microscopy. Close to the metal-oxide interface, precipitates are incorporated unoxidized in the oxide layer. Then, when oxidized, at a few hundreds of nanometers from this interface, they undergo two major evolutions: their structure becomes either nanocrystalline or occasionally amorphous and an iron redistribution and depletion is observed. In the case of precipitates previously made amorphous by irradiation, a similar behavior is observed. The role of precipitates on the oxidation of the Zircaloy-4 is discussed in terms of interaction of the precipitates with the zirconia layer (stability of the dense oxide layer) and oxidation kinetics.
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: H. Anada Publisher: ISBN: Category : Congress Languages : en Pages : 20
Book Description
The microstructure of ZrO2 formed on sheet materials of Zircaloy-2 (Zr2), Zircaloy-4 (Zr4), and an alloy of 1.0% Nb added to Zircaloy-4 (1Nb-Zr4) was analyzed using HRTEM (high-resolution transmission electron microscopy). The relationship between the corrosion behavior of the alloys and the microstructure is discussed. Stress-relieved sheet specimens of the three alloys were prepared and corrosion tested under static conditions in steam at 673 K and 10.3 MPa for a total of 220 days. The order of corrosion resistance in 673-K steam was Zr2, 1Nb-Zr4, and Zr4. Several transitions were observed in the corrosion kinetic curve of 1Nb-Zr4 and Zr2. However, only the first transition was observed in the curve of Zr4. Oxide structure in the pre-transition region on Zr4 was analyzed to be in the following order from the outside surface: columnar m-ZrO2, t-ZrO2 layer, substoichiometric Zr oxide layer, and ?-Zr matrix. The t-ZrO2 layer was approximately 50 to 80 nm thick, and the substoichiometric Zr oxide layer was approximately 100 to 200 nm. These layers were absent in the microstructure of the oxide in the post-transition region. The substoichiometric Zr oxide layer consisted of m-ZrO2 grains that were less than 10 nm in diameter and some as yet unidentified grains that had lattice parameters similar to distorted and significantly oriented ?-Zr. However, the t-ZrO2 layered structure and the substoichiometric Zr oxide layer structure were observed in the post-transition oxides on Zr2 and 1Nb-Zr4. It was also observed that transformation of columnar grains to fine equiaxed grains had occurred near the lateral cracks and the incorporated intermetallic precipitates in post-transition oxides. It is implied from these results that the t-ZrO2 layer and the substoichiometric Zr oxide layer structures play an important role as a barrier layer in controlling the occurrence of kinetic transitions.
Author: H-O Andrén Publisher: ISBN: Category : Autoclave testing Languages : en Pages : 20
Book Description
The microstructure of oxide layers formed in steam in a 400°C, 10.3-MPa autoclave on different zirconium alloys was studied by transmission electron microscopy. Pre-and post-transition oxide layers on Zircaloy-4 with different heat treatments, and post-transition oxide layers on Zr-0.5Sn-0.53Nb were compared. Special attention was paid to the oxide-metal interface. In Zircaloy-4 with short annealing times and high post-transition corrosion rates, the interface had a disordered structure, and pores were found in the oxide very close to the interface. In Zircaloy-4 with low uniform corrosion rates, the interface consisted of highly ordered, columnar grains. The interface in Zr-0.5Sn-0.53Nb had a different appearance, with an intermediate phase of equiaxed grains between the columnar oxide and the metal. The hydrogen absorption of the zirconium alloys during oxidation was measured by the melt extraction technique on samples oxidized for 63, 147, and 343 days. The Zr-0.5Sn0.53Nb alloy had considerably lower hydrogen absorption than Zircaloy-4.
Author: X. Iltis
Author: George P. Sabol
Author: George P. Sabol
Author: Gerry D. Moan
Author: 
Author: Cyril A. Migdal
Author: D. Pêcheur
Author: Kimberly Colas
Author: H. Anada
Author: H-O Andrén