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Author: HM. Chung Publisher: ISBN: Category : Irradiation Languages : en Pages : 26
Book Description
Zircaloy cladding tube specimens from commercial power reactor fuel assemblies (burnup >22 MWd/kgU) have been deformed to fracture at 325°C by either the internal gas-pressurization or the expanding-mandrel technique in a helium or argon environment containing no fission product species (e.g., I, Cs, or Cd). The fracture surfaces of ten irradiated specimens fractured by internal gas pressurization were examined by scanning electron microscopy; six specimens were found to contain various degrees of the pseudocleavage feature that is characteristic of pellet-cladding interaction failures. Out of ten test specimens fractured by expanding-mandrel loading, five were found to contain regions of pseudocleavage on the fracture surfaces. The specimens exhibited "X-marks" on the outer surface and brittle incipient cracks distributed on the inner surface, which are also characteristic of pellet-cladding interaction failures. Transmission/high-voltage electron microscope examinations of the thin-foil specimens obtained from regions adjacent to the failure sites showed that the ductile-failure specimens were characterized by a high density of dislocations which showed normal ->?-type Burgers vectors. In contrast, the brittle-type specimens were characterized by comparatively few dislocations which formed substructures. The dislocations in the brittle specimens were decorated by Zr3O precipitates 2 to 6 nm in size, and cubic-ZrO2 precipitates ? 10 nm in size were also observed in high density. These observations indicate a general immobilization of the dislocations. The low-ductility brittle-type failures appear to have been produced primarily as a result of the Zr3O and cubic-ZrO2 precipitates, augmented by precipitates of bulk hydride 35 to 100 nm in size. The bulk nature of these precipitates, which contrasts with the surficial nature of monoclinic ZrO2 and ?-hydride precipitates, was indicated from stereomicroscopy of weak-beam dark-field images. In situ irradiation of the spent-fuel cladding specimens by 1-MeV electrons at 325°C indicates that the Zr3O and cubic-ZrO2 precipitation is irradiation-induced, whereas the bulk hydride is not.
Author: HM. Chung Publisher: ISBN: Category : Irradiation Languages : en Pages : 26
Book Description
Zircaloy cladding tube specimens from commercial power reactor fuel assemblies (burnup >22 MWd/kgU) have been deformed to fracture at 325°C by either the internal gas-pressurization or the expanding-mandrel technique in a helium or argon environment containing no fission product species (e.g., I, Cs, or Cd). The fracture surfaces of ten irradiated specimens fractured by internal gas pressurization were examined by scanning electron microscopy; six specimens were found to contain various degrees of the pseudocleavage feature that is characteristic of pellet-cladding interaction failures. Out of ten test specimens fractured by expanding-mandrel loading, five were found to contain regions of pseudocleavage on the fracture surfaces. The specimens exhibited "X-marks" on the outer surface and brittle incipient cracks distributed on the inner surface, which are also characteristic of pellet-cladding interaction failures. Transmission/high-voltage electron microscope examinations of the thin-foil specimens obtained from regions adjacent to the failure sites showed that the ductile-failure specimens were characterized by a high density of dislocations which showed normal ->?-type Burgers vectors. In contrast, the brittle-type specimens were characterized by comparatively few dislocations which formed substructures. The dislocations in the brittle specimens were decorated by Zr3O precipitates 2 to 6 nm in size, and cubic-ZrO2 precipitates ? 10 nm in size were also observed in high density. These observations indicate a general immobilization of the dislocations. The low-ductility brittle-type failures appear to have been produced primarily as a result of the Zr3O and cubic-ZrO2 precipitates, augmented by precipitates of bulk hydride 35 to 100 nm in size. The bulk nature of these precipitates, which contrasts with the surficial nature of monoclinic ZrO2 and ?-hydride precipitates, was indicated from stereomicroscopy of weak-beam dark-field images. In situ irradiation of the spent-fuel cladding specimens by 1-MeV electrons at 325°C indicates that the Zr3O and cubic-ZrO2 precipitation is irradiation-induced, whereas the bulk hydride is not.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Zircaloy cladding tube specimens from commercial power reactor fuel assemblies (burnup>22 MWd/kgU) have been deformed to fracture at 325°C by either the internal gas-pressurization or the expanding-mandrel technique in a helium or argon environment containing no fission product species (e.g., I, Cs, or Cd). The fracture surfaces of 11 irradiated specimens fractured by internal gas pressurization were examined by scanning electron microscopy, and 7 specimens were found to contain various degrees of the pseudocleavage feature that is characteristic of pellet-cladding interaction failures. Out of 10 test specimens fractured by expanding-mandrel loading, 5 were found to contain regions of pseudocleavage on the fracture surfaces. The specimens exhibited ''X-marks'' on the outer surface and brittle incipient cracks distributed on the inner surface, which are also characteristic of pellet-cladding interaction failures.
Author: Publisher: ISBN: Category : Languages : en Pages : 16
Book Description
Specimen geometries have been developed to determine the mechanical properties of irradiated Zircaloy cladding subjected to the mechanical conditions and temperatures associated with reactivity-initiated accidents (RIA) and loss-of-coolant accidents (LOCA). Miniature ring-stretch specimens were designed to induce both uniaxial and plane-strain states of stress in the transverse (hoop) direction of the cladding. Also, longitudinal tube specimens were also designed to determine the constitutive properties in the axial direction. Finite-element analysis (FEA) and experimental parameters and results were closely coupled to optimize an accurate determination of the stress-strain response and to induce fracture behavior representative of accident conditions. To determine the constitutive properties, a procedure was utilized to transform measured values of load and displacement to a stress-strain response under complex loading states. Additionally, methods have been developed to measure true plastic strains in the gauge section and the initiation of failure using real-time data analysis software. Strain rates and heating conditions have been selected based on their relevance to the mechanical response and temperatures of the cladding during the accidents.
Author: H. Tsai Publisher: ISBN: Category : Axial specimens Languages : en Pages : 16
Book Description
Specimen geometries have been developed to determine the mechanical properties of irradiated Zircaloy cladding subjected to the mechanical conditions and temperatures associated with reactivity-initiated accidents (RIA) and loss-of-coolant accidents (LOCA). Miniature ring-stretch specimens were designed to induce both uniaxial and plane-strain states of stress in the transverse (hoop) direction of the cladding. Also, longitudinal tube specimens were also designed to determine the constitutive properties in the axial direction. Finite-element analysis (FEA) and experimental parameters and results were closely coupled to optimize an accurate determination of the stress-strain response and to induce fracture behavior representative of accident conditions. To determine the constitutive properties, a procedure was utilized to transform measured values of load and displacement to a stress-strain response under complex loading states. Additionally, methods have been developed to measure true plastic strains in the gauge section and the initiation of failure using real-time data analysis software. Strain rates and heating conditions have been selected based on their relevance to the mechanical response and temperatures of the cladding during the accidents.
Author: Yongli Ren Publisher: National Library of Canada = Bibliothèque nationale du Canada ISBN: 9780612915626 Category : Languages : en Pages : 242
Book Description
Based on previous work, a modified VEC technique has been developed in this study. This technique has been proven, through the HCP based Ti3Al2.5V tubing, to be reliable for fracture toughness measurement of thin-walled tubes. The average critical J integral value of unirradiated Zircaloy-4 cladding is hence determined to be 82.6 kN/m, corresponding to a KIC value of 101.1Mpa.m1/2. The evaluation on microstructure, microhardness, and elastic moduli of the cladding indicates that this material is moderately anisotropic or textured. Fractographic examination of entire fracture surface and crack tip side view demonstrates that the pre-crack fracture is a typical fatigue related fracture since fatigue striations are all over the fracture surface. On the other hand, the J-integral test fracture is of the mixed mode of microvoid coalescence with intergranular fracture since elongated and tear-shaped dimples, secondary cracks, and the zigzag crack propagation path are major features of the corresponding fracture surface.
Author: HM. Chung
Author: HM. Chung
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Author: R. B. Adamson
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Author: Leo F. P. Van Swam
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Author: H. Tsai![Fracture Toughness Behavior of Zircaloy-4 in the Form of Fuel Cladding Tubing in Nuclear Reactors [microform] PDF](https://books.google.com/books/content/images/frontcover/bbgjAAAACAAJ?fife=w80-h100)
Author: Yongli Ren