Helium release measurements and diffusion coefficient calculations of helium in a neutron-irradiated -SiC have been carried out in the temperature range of 750-1,260 C. The powder was obtained from SiC ceramics containing B 4 C, of which 10 B concentration was 4:2Â10 16 atom/mg. Neutron irradiation was conducted up to a fluence of 2:8Â10 24 n/m 2 (E>0:1 MeV) at $300 C. The diffusion coefficients were calculated for the temperature region of 750-1,060 C with time range of 0-10 min. The diffusion coefficient of helium for SiC containing B 4 C was D ðcm 2 /sÞ¼1:38Â10 À10 exp½À0:91AE0:07 ðeV/atomÞ=kT. Dissociative and interstitial diffusion mechanisms were supposed. Diffusion coefficients were reduced above $1,160 C probably due to accelerated migration of vacancies.
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