Helium release and diffusion mechanism in SiC containing B4C

Helium release measurement have been carried out in the temperature range of 750-1260 DGC for neutron-irradiated *a-SiC powder. The powders were obtained from SiC ceramics containing B4C with varying contents of 10B, i.e., 4.2x1016, 1.13x1017 and 1.84x1017 atom/mg. Neutron irradiation was conducted up to a fluence of 2.8x1024 n/m2 (E > 0.1 MeV) at ~300 DGC. The diffusion coefficients were calculated for the temperature region of 750-1060 DGC and for time intervals 0-10, 10-60 min and 1-6 h at each temperature. The diffusion coefficient of He for SiC was affected by the original 10B concentration. Both helium diffusion coefficient and apparent activation energy were smaller for higher concentrations of 10B.