Couet, Adrien. Characterization of Oxide Porosity in Irradiated Zirconium Pre-Transition Corrosion Films

Principal Investigator
First Name:
Adrien
Last Name:
Couet
Institution:
University of Wisconsin
Title:
Assistant Professor
Team Members:
Name: Institution: Expertise: Status:
Jadin Swarts University of Wisconsin J. Swarts will perform the PAS at NCSU. She already visited the facility and discussed in person with the PAS beamline staff about this experiment. She is also studying the same samples using FIB/TEM and has quantified porosity by TEM analysis Graduate Student
Adrien Couet University of Wisconsin Corrosion, Synchrotron, Irradiation, Alloys, electrochemistry Faculty
Experiment Details:
Experiment Title:
Characterization of Oxide Porosity in Irradiated Zirconium Pre-Transition Corrosion Films
Describe the work that you are proposing in detail. Please include as many specifics as possible (e.g., dose, dose rate, ion energy, types of ions, beam line x-ray energy, irradiation temperature, analysis temperature, atmosphere, etc.):
Samples of proton-irradiated and non-irradiated zirconium-niobium alloys were autoclave-corroded in pure water at 320 °C for up to 120 days to form pre-transition oxide. Proton irradiation of Zr-xNb (x = 0.2, 0.4, 0.5, 1.0) specimens was completed under 2-MeV rastering proton beam to 1.0 dpa at 350 °C at the University of Wisconsin Ion Beam Laboratory as part of previous studies and the sample microstructure has been fully characterized using TEM/HRSTEM/APT thanks to a previous RTE award. Post-irradiation/post-corrosion oxides have been characterized using TEM and porosity has been quantified. As part of the proposed RTE, we will perform positron annihilation lifetime spectroscopy (PALS) and doppler broadening spectroscopy (DBS) at the Positron Intense Beam Facility at North Carolina State University in order to characterize and compare the pore density between the irradiated and non-irradiated samples at different depths within the thin oxide layer. Results will also be compared to pore quantification using Fresnel contrast TEM data already acquired.
Technical Abstract
We propose to investigate the porosity development and evolution in zirconium-niobium alloys, samples of irradiated and non-irradiated Zr-xNb (x = 0.2, 0.4, 0.5, 1.0) and Zircaloy-4 irradiated under 2-MeV rastering proton beam to 1.0 dpa at 350 °C at the University of Wisconsin Ion Beam Laboratory. These samples were then corroded in water at 320 °C for up to 120 days total exposure. Samples were archived at varying total exposures, resulting in a range of catalogued pre-transition oxide thicknesses for each irradiated alloy. As part of the proposed RTE, Positron Annihilation Lifetime Spectroscopy (PALS) and Doppler Broadening Spectroscopy (DBS) will be performed on these prepared samples at the Positron Intense Beam Facility at North Carolina State University. These results will be used to characterize and compare the pore density between the irradiated and non-irradiated samples at different depths within the thin oxide layer. It is noted that this would be the first time that PAS is used on pre-irradiated, corroded, specimen. Preliminary study performed by PI’s group at the NCSU facility confirmed that the sensitivity to the thin film oxide layer is too low using a positron point source because most of the annihilation events occur within the bulk material, resulting in a low signal-to-noise ratio. By using a positron beam condition, long-lifetime positronium can be detected with better resolution and sensitivity to investigate porosity in thin-film zirconium oxides. 12 samples will be analyzed, 4 pre-irradiated ZrNb samples corroded up to 120 days, 4 pre-irradiated Zircaloy-4 samples corroded up to 120 days and 4 unirradiated ZrNb and Zircaloy-4 samples corroded up to 120 days to serve as benchmark. The samples are already available and, after discussion with the NCSU PAS group, 4 weeks of beamtime are required to accommodate these 12 samples.