Measurement of Weight of Kernels in a Simulated Cylindrical Compact for HTGR Using X-ray Computed Tomography

The TRISO-coated fuel particle for the HTGR (high temperature gas-cooled reactor) is composed of a nuclear fuel kernel and outer coating layers. The coated particles are mixed with graphite matrix to make HTGR fuel element. There are two types of fuel elements, a spherical fuel element and a cylindrical fuel compact. The spherical fuel element is burned in a PBR (pebble bed reactor), such as HTR-10 in China and PBMR in South Africa. The cylindrical fuel compact is burned in a PMR (prismatic block modular reactor), such as GT-MHR (Gas turbine modular helium reactor) in the U.S.A. and HTTR in Japan. Fig. 1 shows a model of the cylindrical fuel compact. Weight of fuel kernels in an element is one of the most important properties for evaluating the characteristics of fuel element. Generally, the weight of fuel kernels in an element is measured by using chemical analysis or gamma-ray spectrometer. Chemical analysis is a destructive method, and a reference sample is required to keep accuracy for a gamma-ray spectrometer. Measurement error can be induced because geometric shape of test sample is a little different from that of a reference sample for a gammaray spectrometer. In this study, the weight of kernels in a compact is measured on the three-dimensional (3-D) information acquired by X-ray computed tomography (CT) for a cylindrical compact. The volume of kernels as well as the number of kernels is calculated from the 3-D density information. The weight of kernels will be measured form the volume of kernels or the number of kernels in a compact