Characterization of Nuclear Materials and Fuels with Advanced X-ray and Neutron Techniques: X-ray Tomography and Microscopy
Sponsored by: TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Nuclear Materials Committee
Program Organizers: Xuan Zhang, Argonne National Laboratory; Jonathan Almer, Argonne National Laboratory; Maria Okuniewski, Purdue University; Joshua Kane, Idaho National Laboratory; Donald Brown, Los Alamos National Laboratory; J. Kennedy, Idaho National Laboratory; Arthur Motta, Pennsylvania State University

Tuesday 2:00 PM
March 16, 2021
Room: RM 51
Location: TMS2021 Virtual

Session Chair: Joshua Kane, Idaho National Laboratory; Xuan Zhang, Argonne National Laboratory

2:00 PM
Characterization of Nuclear Energy Materials in 2D and 3D using Laboratory-based X-ray Microscopy: Nikolaus Cordes¹; Joshua Kane¹; Aaron Craft¹; ¹Idaho National Laboratory
    Two dimensional (2D) and three dimensional (3D) laboratory-based X-ray microscopy has been used to characterize a variety of materials related to nuclear energy, including fuel (U-10Zr), cladding (SiC/SiC composites, zirconium alloys), and structural components (graphite). 3D X-ray imaging of nuclear fuels is difficult due to the inherent mass attenuation coefficients of high-Z materials and is limited to a fuel thickness of a few millimeters at most. However, sub-micrometer scale 3D X-ray microscopy can be employed to characterize nuclear fuel samples of the appropriate size. 2D X-ray microscopy can also be employed to characterize high aspect ratio fuel samples to supplement other characterization techniques. While the imaging of fuel is not trivial, the imaging of cladding and structural materials is more straightforward. This presentation will give an overview of the techniques used to image nuclear energy materials using laboratory-based X-ray microscopy at Idaho National Laboratory’s Irradiated Materials Characterization Laboratory.

2:20 PM
Non-destructive Correlative 3D Characterization of Nuclear Graphite: From the Microscale to the Nanoscale: Stephen Kelly¹; Robin White¹; William Harris¹; Tobias Volkenandt¹; Benjamin Tordoff¹; Giuliano Laudone²; Katie Jones²; Ben Veater²; ¹Carl Zeiss X-ray Microscopy; ²University of Plymouth
    Graphite is a key material in the design and operation of a wide range of nuclear reactors because of its attractive combination of thermal, mechanical, and neutron interaction properties. In all its applications, the microstructural evolution of nuclear graphite under operating conditions will strongly influence reactor lifetime and performance. However, measuring the 3D microstructural characteristics of nuclear graphite has traditionally faced many challenges. X-ray tomographic techniques face limitations in achievable resolution on bulk (mm-sized) specimens while serial sectioning techniques like FIB-SEM struggle to achieve adequate milling rates for tomographic imaging over representative volumes. To address these shortcomings, we present here a multiscale, targeted, correlative microstructural characterization workflow for nuclear graphite employing microscale and nanoscale x-ray microscopy with a connected laser milling step in between the two modalities. We present details of the microstructure, including porosity analysis, spanning orders of magnitude in feature size for nuclear graphite samples including IG-430.

2:40 PM
Irradiation Effects on Precipitate Distributions in High-temperature Ultrafine-precipitate-strengthened Steel Characterized by Synchrotron Micro-computed Tomography: Alejandro Figueroa¹; Sri Nori¹; Peter Kenesei²; Jonathan Almer²; Maria Okuniewski¹; ¹Purdue University; ²Argonne National Laboratory
    High-temperature ultrafine-precipitate-strengthened (HT-UPS) steel is considered for application in advanced reactor designs for its strength and creep resistance at elevated temperatures (>600°C). This effect is primarily due to the presence of nanometer sized metal (Ti, Nb, V) carbides along with M23C6Ź (M: Fe, Cr, Mn) precipitates. Synchrotron micro-computed tomography is unique in its ability to conduct three-dimensional geometric and volumetric analyses of second phase particles non-destructively, allowing for same-sample analysis before and after irradiation. By conducting synchrotron micro-computed tomography on both the pre- and post-irradiated conditions, an assessment was conducted on the irradiation-induced effects on the precipitates in HT-UPS steel. The HT-UPS steel samples were irradiated in the High Flux Isotope Reactor to doses of 0.003 and 0.3 dpa. To delineate irradiation behavior from thermal effects, same-sample annealing trials were assessed. imaged in both the pre- and post-irradiated conditions at the Advanced Photon Source.

3:00 PM
Identifying the Microstructural Origins of Creep Damage in Alloy 617: Mark Messner¹; Xuan Zhang¹; Meimei Li¹; Michael McMurtrey²; ¹Argonne National Laboratory; ²Idaho National Laboratory
    Creep damage often dictates the life of high temperature structural components, likely including components in future advanced high temperature nuclear reactors. Past work has developed a standard microstructural model for the nucleation and diffusion-assisted cavitation of voids on grain boundaries. However, there has been little direct experimental validation of this model. This work identifies the microstructural origins of creep damage using X-ray imaging of interrupted notched creep samples of Alloy 617. The approach adopted here is to fuse microresolution computed tomography and near field and far field High Energy Diffraction Microscopy data sets, taken at the Advanced Photon Source, in order to identify the location, size, and morphology of voids in the interrupted samples relative to key microstructural features and the local states of stress. This information will be used to refine microstructural models of creep damage in order to better predict the onset of creep failure in structural components.

3:20 PM
Getting “Around” the High Mass Attenuation Issue for μX-ray Computed Tomography of Nuclear Fuels: Joshua Kane¹; Nikolaus Cordes¹; Aaron Craft¹; Douglas Marshall¹; John Stempien¹; ¹Idaho National Laboratory
     As X-ray tomography is non-destructive it provides a unique opportunity to non-destructively examine the same region of a nuclear fuel or structural material pre- and post-irradiation. Such information can potentially be obtained at sub-micrometer resolution. One of the major challenges limiting the use of X-ray tomography in nuclear research is the significant mass attenuation of Uranium. Often, a traditional lab-based micro-focus or nano-focus source is incapable of practically imaging more than a millimeter of a fuel such as UO2. Additionally, imaging fuel and surrounding material (such as cladding) becomes difficult due to the significant differences in x-ray mass attenuation and limited dynamic range of traditional detectors.This work will utilize a TRISO fuel form to demonstrate a means to image “around” fuel and provide a high quality, high resolution reconstruction of the TRISO fuel kernel as well as the surrounding low-density low mass attenuation (pyrolytic carbon and silicon carbide) layers.