Nano-scale chemical evolution in a proton-and neutron-irradiated Zr alloy

Proton-and neutron-irradiated Zircaloy-2 are compared in terms of the nano-scale chemical evolution within second phase particles (SPPs) Zr(Fe,Cr)2 and Zr2(Fe,Ni). This is accomplished through ultra-high spatial resolution scanning transmission electron microscopy and the use of energy-dispersive X-ray spectroscopic methods. Fe-depletion is observed from both SPP types after irradiation with both irradiative species, but is heterogeneous in the case of Zr(Fe,Cr)2, predominantly from the edge region, and homogeneously in the case of Zr2(Fe,Ni). Further, there is evidence of a delay in the dissolution of the Zr2(Fe,Ni) SPP with respect to the Zr(Fe,Cr)2. As such, SPP dissolution results in matrix supersaturation with solute under both irradiative species and proton irradiation is considered well suited to emulate the effects of neutron irradiation in this context. The mechanisms of solute redistribution processes from SPPs and the consequences for irradiation-induced growth phenomena are discussed.<br/

New insights in structural characterization of zirconium alloys oxidation at high temperature

International audienc

INVESTIGATION OF NEUTRON RADIATION EFFECTS ON THE MECHANICAL BEHAVIOR OF RECRYSTALLIZED ZIRCONIUM ALLOYS

International audienceNeutron radiation induces important changes in the mechanical behavior of recrystallized zirconium alloys used as fuel cladding tube. The neutron radiation effects on the mechanical behavior for internal pressure test performed at 350DC have been investigated using a specific analysis in terms of isotropic hardening, kinematic hardening and viscous stress. The impact of irradiation has been interpreted in terms of microscopic deformation mechanisms observed by Transmission Electron Microscopy (TEM). It is proposed that because of the localization of the plastic deformation inside channels and because of the only activation of basal channeling, the kinematic hardening must be strong in irradiated zirconium alloys. A simple unified phenomenological modeling is also used in order to have a coherent description of the radiation effects on the mechanical behavior

INVESTIGATION OF NEUTRON RADIATION EFFECTS ON THE MECHANICAL BEHAVIOR OF RECRYSTALLIZED ZIRCONIUM ALLOYS

International audienceNeutron radiation induces important changes in the mechanical behavior of recrystallized zirconium alloys used as fuel cladding tube. The neutron radiation effects on the mechanical behavior for internal pressure test performed at 350DC have been investigated using a specific analysis in terms of isotropic hardening, kinematic hardening and viscous stress. The impact of irradiation has been interpreted in terms of microscopic deformation mechanisms observed by Transmission Electron Microscopy (TEM). It is proposed that because of the localization of the plastic deformation inside channels and because of the only activation of basal channeling, the kinematic hardening must be strong in irradiated zirconium alloys. A simple unified phenomenological modeling is also used in order to have a coherent description of the radiation effects on the mechanical behavior

Transmission electron microscopy study of second phase particles irradiated by 2 MeV protons at 350 °C in Zr alloys

International audienceIn order to improve the understanding of the microscopic phenomena occurring during irradiation in zirconium alloys, ion beam irradiations are performed at 350 DC (dose-rate of 2 × 10-5 dpa/s) on recrystallized Zy-4 and M5 alloys, with 2 MeV protons. The aim of this study is to determine in which way proton irradiations can be representative of neutron irradiations, considering the second phase particle changes and the influence of these changes on the microstructural evolution of the material during irradiation. The 2 MeV proton irradiation at 350 DC, performed here, seems to reproduces well what happened in Zy-4 in PWR conditions with a progressive amorphisation of the Zr(Fe,Cr)2 Laves phases, but with a lower growth rate and a higher Fe/Cr ratio of the amorphous rim. The Zr(Fe,Nb)2 s phase particles in M5 undergo a uniform amorphisation, while the native βNb precipitates remain fully crystalline as evidenced in neutron irradiation at very low irradiation temperature. No radiation-enhanced precipitation of nanometric BETA-Nb particles was observed. Thus, for M5 alloy, the present irradiation seems to be representative of neutron irradiations at a very low irradiation temperature. Nevertheless it does not reproduce what happens in PWR conditions, where no amorphisation and a drastic loss of iron is reported for the Zr(Fe,Nb)2 Laves phase SPPs. Despite the lower iron rejection from the particles into the matrix during proton irradiation than during neutron irradiation, <c>-component loop distribution is found to be similar after both types of irradiations. These results underline the influence of both dose-rate and temperature on second phase particles behavior under irradiation and point out the complexity of iron rejection influence on the basal <c>-component loops. Indeed, although the <c>-component loop nucleation and growth seem locally correlated to iron dissolution into the matrix, they do not seem to be directly correlated to the global amount of iron rejected

Influence of Pre-Transient Oxide on LOCA High Temperature Steam Oxidation and Post-Quench Mechanical Properties of Zircaloy-4 and M5™ cladding

International audienc