Strength of Silicon-Carbide Coating Layers of Fuel Particles for High Temperature Gas-Cooled Reactors

Abstract

Strength and Young's modulus of pyrolytic silicon carbide (SiC) were measured. The specimens were the ringed SiC which were taken from TRISO coated fuel particles for High Temperature Gas-cooled Reactors (HTGR). Four kinds of unirradiated specimens and the two of irradiated ones were prepared for the measurement. The SiC coating layer consisting of columnar structure with large crystal grains (about 5 μm) was stronger than the SiC of laminar structure with small grains (less than 1μm). The mean strength of the former SiC was larger than 1,700 MN/m2, while that of the latter SiC, less than 1,600 MN/ms. The SiC with low density (3.14 g/cm3) was the weakest among the present specimens. By irradiation of fission recoil, the mean strength of the SiC of columnar structure with large grains almost unchanged, but that of the SiC of laminar structure with small grains increased about 14%, of which irradiation dose was about 20 times larger than that for the former specimen. As for Young's modulus, the values ranged between 324 and 381 GN/m2 and no significant dependence of the modulus on microstructure of the SiC and irradiation was recognized.