Nondestructive measurement of the weight of kernels in a simulated cylindrical fuel compact for HTGR using X-ray computed tomography

The TRISO-coated fuel particle for the high temperature gas-cooled reactor (HTGR) is composed of a nuclear fuel kernel and outer coating layers. The coated particles are mixed with graphite matrix to make HTGR fuel element. Weight of fuel kernels contained in the element is one of the important items for evaluating the characteristics of fuel element, which is generally measured by chemical analysis or gamma-ray spectrometer. The chemical analysis is a destructive method, and gamma-ray spectrometer requires elaborate reference sample for the measurement. In this study, X-ray computed tomography (CT) is suggested to measure the weight of kernels in an element. The three-dimensional (3D) density information is acquired by the X-ray CT for a simulated compact including simulated TRISO-coated particles with ZrO2 kernels. The volume of kernels as well as the number of kernels in the simulated compact was calculated from the 3D density information. The weight of kernels in the simulated compact was calculated from the volume of kernels and the average density of kernels. It was also calculated from the number of kernels and the average weight of kernels for comparison.