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Conference Article: Influence of air oxidation on thermal shock resistances of nuclear carbon materials

Kurumada, A.; Oku, T. (Ibaraki Univ., Hitachi (Japan). Faculty of Engineering); Harada, K. (Japan Atomic Energy Research Inst., Ibaraki (Japan)); Kawamata, K. (Ibaraki Univ., Ibaraki (Japan). Faculty Engineering); Sato, S. (Iwaki Meisei Univ., Fukushima (Japan)); Hiraoka, T. (Tokyo Tanso Co. Ltd., Kagawa (Japan)); McEnaney, B. (Bath Univ. (United Kingdom). School of Materials Science)

Abstract

The purpose of this study is to evaluate the influence of air oxidation at 500 deg. C on thermal shock resistances and thermal shock fracture toughnesses of a carbon fibre reinforced carbon composite (C/C composite) made from rayon carbon fibre felt and three fine-grain, isotropic, nuclear graphites. These thermal shock resistances and thermal shock fracture toughnesses for the four nuclear carbon materials were degraded slightly by oxidation. The extents of degradations of the thermal shock parameters were less than those of mechanical and fracture mechanics properties. However, the extent of degration of thermal diffusivity was much less than those of the thermal shock parameters. In observations of the microstructures of the fracture surfaces, after oxidation of the graphite, the size and the number of pores were increased and the fracture surfaces were roughened by oxidation of boundaries of graphite particles. After oxidation of the C/C composite, there was preferential removal of the boundary layer between carbon fibre and pyrolitic carbon matrix and carbon fibre pull out. However, the more graphitized cores of pyrolitic carbon remained and the extents of degradations of the thermal shock parameters for the C/C composite were less than those of the graphites.

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key words: Gas Cooled Reactor, Nuclear Technology

Reference:: Specialists meeting on graphite moderator lifecycle behaviour. Bath (United Kingdom). 24-27 Sep 1995.; International Atomic Energy Agency, Vienna (Austria); IAEA-TECDOC--901, pp:215-224