Crushing Strength of Fuel Kernels for High-Temperature Gas-Cooled Reactors

概要

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The crushing strength of thorium oxide and thorium-uranium mixed oxide fuel kernels for high-temperature gas-cooled reactors (HTGR) was estimated by application of the Hertz theory of contact to the failure load obtained in a simple crushing test. The strength data were interpreted assuming the Weibull distribution. The crushing strength of the Th0<SUB>2</SUB> kernels ranged from 1.7 to 1.9 GPa. The strength was found to be closely related to the microstructure of the kernel and to be increased by the kernel properties : small grain size and smooth surface. Fracture would occur in a transgranular manner for the fine-grained kernels and in an intergranular manner for the coarse-grained. Flaws, which are located at or near surface of the boundary of the contact area, act as fracture origins.