Abstract
The fuel safety and performance of high-temperature gas-cooled reactor (HTGR) are dependent on the integrity and geometric parameter of Tri-structural Isotropic (TRISO) coated particle. Micro X-ray computed tomography (CT) was used for nondestructive testing and three-dimensional measurement of the particle components which are composed of kernel, buffer layer, inner pyrolytic carbon layer (IPyC), silicon carbide (SiC) layer, and outer pyrolytic carbon (OPyC) layer. The thickness distribution and volume of kernel and coating layers are obtained by constructing 3D volume rendering of TRISO particle. Mean thickness of each layer is calculated for comparison with design value. A comparison between two-dimensional and three-dimensional measurement results is also made. It is found that the thickness distribution of all layers approximately obeys Gaussian distribution. Deviation of the thickness of kernel and coating layers between 3D measurement result and design value is 7.88%, -25.63%, -45.50%, 13.87%, and 14.73%, respectively. The deviation will affect the failure probability of TRISO particle. Obvious difference of the OPyC mean thickness between 3D measurement and 2D measurement is found, which proves that the proposed 3D measurement provides comprehensive information of the particle. However, 2D and 3D measured thickness of the kernel and IPyC layer tend to be similar.
Highlights
Tri-structural Isotropic (TRISO) coated particles are the fuel form for high-temperature gas-cooled reactor (HTGR) as well as other reactor forms [1, 2] due to its stability to retain fission product at even 1600∘C [3]
For large numbers of particles, digital radiography is recommended as this technique is fastimaging and economic in terms of large samples
2D and 3D measurement were used for a TRISO particle
Summary
Tri-structural Isotropic (TRISO) coated particles are the fuel form for high-temperature gas-cooled reactor (HTGR) as well as other reactor forms [1, 2] due to its stability to retain fission product at even 1600∘C [3]. It is composed of kernel, buffer layer, inner pyrolytic carbon (IPyC) layer, silicon carbide (SiC) layer, and outer pyrolytic carbon (OPyC) layer. Temperature distribution is affected by layer thickness. Thickness distribution and the volume of the particle will affect its failure probability. Strict testing and evaluation for TRISO particle are necessary before operation
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