Microstructural analysis of TRISO particles using multi-scale X-ray computed tomography

Abstract

TRISO particles, a composite nuclear fuel built up by ceramic and graphitic layers, have outstanding high temperature resistance. TRISO fuel is the key technology for High Temperature Reactors (HTRs) and the Generation IV Very High Temperature Reactor (VHTR) variant. TRISO offers unparalleled containment of fission products and is extremely robust during accident conditions. An understanding of the thermal performance and mechanical properties of TRISO fuel requires a detailed knowledge of pore sizes, their distribution and interconnectivity. Here 50 nm, nano-, and 1 μm resolution, micro-computed tomography (CT), have been used to quantify non-destructively porosity of a surrogate TRISO particle at the 0.3–10 μm and 3–100 μm scales respectively. This indicates that pore distributions can reliably be measured down to a size approximately 3 times the pixel size which is consistent with the segmentation process. Direct comparison with Scanning Electron Microscopy (SEM) sections indicates that destructive sectioning can introduce significant levels of coarse damage, especially in the pyrolytic carbon layers. Further comparative work is required to identify means of minimizing such damage for SEM studies. Finally since it is non-destructive, multi-scale time-lapse X-ray CT opens the possibility of intermittently tracking the degradation of TRISO structure under thermal cycles or radiation conditions in order to validate models of degradation such as kernel movement. X-ray CT in-situ experimentation of TRISO particles under load and temperature could also be used to understand the internal changes that occur in the particles under accident conditions

Synthesis and characterisation of magnesium matrix composite reinforced with titanium dioxide nanoparticulates

“…Pure Mg and Mg-TiO 2 nanocomposite samples were examined through a high resolution Xradia Micro-Computed Tomography (μCT) facility at the AFMM lab, IISc Banglore. This micro-CT [22][23][24][25] system has a Hamamatsu x-ray source with the energy capability of 40-150 kV and the spatial resolution ranging from ∼30 μm to less than 1 μm. In this work, the x-ray source voltage was set at 80 kV, Power was at 10 W and the beam current was 86.9 μ A.…”

Three-Dimensional Measurement of TRISO Coated Particle Using Micro Computed Tomography

“…Beam hardening is the main problem of X-ray CT. Although it can be reduced by increasing photon energy, the contrast difference between coating layers is also mitigated [9]. 2D measurement of the particle thickness was ascertained by extracting the boundary of each layer with phase contrast imaging [10,11].…”

“…2D measurement of the particle thickness was ascertained by extracting the boundary of each layer with phase contrast imaging [10,11]. Mean thickness of each layer was calculated from 3D volume rendering of the particle [3,9]. First 3D 2 Science and Technology of Nuclear Installations reconstruction from an irradiated PYCASSO particles [12] was obtained.…”

Time‐lapse lab‐based x‐ray nano‐CT study of corrosion damage

“…Variations between data sets can also arise from changes in the x-ray source output and detector sensitivity over time. The effects of these 'systematic' variations can be reduced using local thresholding techniques for segmentation or by matching greyscale histograms of the volumes by applying a linear scaling such that the cumulative density functions are in good agreement (Lowe et al, 2015). Alternatively, Bradley proposed an approach based on a 'volumetric standard' (Bradley, 2016), which is either a region of the sample that does not vary between scans, or a separate object that is invariant and is included in the scan volume.…”