Mechanisms of uniform corrosion of Zirconium alloys in water and steam PDF Download

Author: Boel Wadman
Publisher:
ISBN: 9789170329098
Category : Corrosion and anti-corrossives
Languages : en
Pages : 80

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Author: J. Paul Pemsler
Publisher:
ISBN:
Category : Steam
Languages : en
Pages : 26

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Author: M. Preuss
Publisher:
ISBN:
Category : Corrosion mechanisms
Languages : en
Pages : 23

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Understanding the key corrosion mechanisms in a light water reactor primary water environment is critical to developing and exploiting improved zirconium alloy fuel cladding. In this paper, we report recent research highlights from a new collaborative research programme involving 3 U.K. universities and 5 partners from the nuclear industry. A major part of our strategy is to use the most advanced analytical tools to characterise the oxide and metal/oxide interface microstructure, residual stresses, as well as the transport properties of the oxide. These techniques include three-dimensional atom probe (3DAP), advanced transmission electron microscopy (TEM), synchrotron X-ray diffraction, Raman spectroscopy, and in situ electro-impedance spectroscopy. Synchrotron X-ray studies have enabled the characterisation of stresses, tetragonal phase fraction, and texture in the oxide as well as the stresses in the metal substrate. It was found that in the thick oxide (here, Optimized-ZIRLO, a trademark of the Westinghouse Electric Company, tested at 415°C in steam) a significant stress profile can be observed, which cannot be explained by metal substrate creep alone but that local delamination of the oxide layers due to crack formation must also play an important role. It was also found that the oxide stresses in the monoclinic and tetragonal phases grown on Zircaloy-4 (autoclave testing at 360°C) first relax during the pre-transition stage. Just before transition, the compressive stress in the monoclinic phase suddenly rises, which is interpreted as indirect evidence of significant tetragonal to monoclinic phase transformation taking place at this stage. TEM studies of pre- and post-transition oxides grown on ZIRLO, a trademark of the Westinghouse Electric Company, have used Fresnel contrast imaging to identify nano-sized pores along the columnar grain boundaries that form a network interconnected once the material goes through transition. The development of porosity during transition was further confirmed by in situ electrochemical impedance spectroscopy (EIS) studies. 3DAP analysis was used to identify a ZrO sub-oxide layer at the metal/oxide interface and to establish its three-dimensional morphology. It was possible to demonstrate that this sub-oxide structure develops with time and changes dramatically around transition. This observation was further confirmed by in situ EIS studies, which also suggest thinning of the sub-oxide/barrier layer around transition. Finally, 3DAP analysis was used to characterise segregation of alloying elements near the metal/oxide interface and to establish that the corroding metal near the interface (in this case ZIRLO) after 100 days at 360°C displays a substantially different chemistry and microstructure compared to the base alloy with Fe segregating to the Zr/ZrO interface.

Author: Gerry D. Moan
Publisher: ASTM International
ISBN: 0803128959
Category : Nuclear fuel claddings
Languages : en
Pages : 891

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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: Stanley Kass
Publisher:
ISBN:
Category : Uranium alloys
Languages : en
Pages : 28

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Author: J. Paul Pemsler
Publisher:
ISBN:
Category : Steam
Languages : en
Pages : 28

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Author: George P. Sabol
Publisher: ASTM International
ISBN: 0803124996
Category : Microstructure
Languages : en
Pages : 953

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Author:
Publisher: ASTM International
ISBN:
Category :
Languages : en
Pages : 681

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Author: L. Lunde
Publisher:
ISBN:
Category : Corrosion tests
Languages : en
Pages : 20

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The nodular attack of ?-annealed Zircaloy-2 and Zircaloy-4 in steam at 500°C is dependent upon the presence of hydrogen in the environment, the important function being the hydrogen to steam ratio rather than partial pressures. The uniform corrosion between the nodules was unaffected by the hydrogen in the steam. ?-quenched Zircaloy-2 showed the opposite behavior, suffering nodular corrosion in hydrogen-free steam and corroding uniformly in steam with hydrogen additions. Nodules did initiate on Ozhenite-0.5, but did not develop into serious localized attack for ?-annealed material. Alloys with higher niobium content and Valoy were independent of hydrogen in the steam and they never suffered localized corrosion. The chromium-rich particles in Valoy did not influence the oxidation of the matrix adjacent to the particles under hydrogenated conditions. The iron-rich particles in the Zircaloys and in Ozhenite-0.5 decreased the oxidation of matrix in a region around each particle. Nodules initiated by oxide cracking over grain boundaries in areas with few intermetallic particles. The observed influence of hydrogen in the steam on nodular corrosion is attributed to its effect on the electron conductance of the oxidized iron-rich precipitates.

Author: Walter K. Boyd
Publisher:
ISBN:
Category : Corrosion and anti-corrosives
Languages : en
Pages : 100

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