α-SiC ceramics containing 10B were neutron-irradiated in the JMTR to a fluence of 6.0 × 1024 n/m2 (E > 1 MeV) at 650° C. Helium release from SiC ceramics and powders was measured up to 2000° C. Microstructural observation by TEM was also carried out on SiC specimens annealed at temperatures in the range 1200-2000 °C. The helium release rate of the powder specimen started to increase at about 800°C and two peaks were observed at 1100 and 1260°C. By contrast, the sintered specimen showed a low gas release rate up to 1800°C and exhibited a rapid increase above this temperature. The helium release mechanism from the sintered specimen was discussed in terms of the mobility of helium atoms and vacancies, and bubbles at grain boundaries.
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