Reaction sintered β-SiC specimens were neutron-irradiated in the fast breeder reactors, JOYO, Rapsodie and Phenix, at temperatures around 430 to 550°C to a fluence from 4.0 × 1023 to 1.0 × 1027 n/m2 (E > 0.1 MeV). A change in the specimen length was accurately measured using a conventional micrometer after isochronal annealing at high temperatures. The specimens irradiated to a neutron fluence of about 1025 n/m2 showed a larger dimensional change on anneals than those irradiated to a fluence of 1026 n/m2. A change in lattice parameters by annealing was also measured. It showed that the temperature dependence is nearby identical to that of the macroscopic length change. The transmission electron microscopic study of the neutron-irradiated β-SiC specimens showed the formation of irradiation induced defects, considered to be dislocation loops. An increase in the neutron fluence resulted in the growth of the dislocation loops. The dislocation loops in strongly irradiated β-SiC interacted with each other, forming the heavily disturbed dislocation structure. The effect of the neutron fluence on the microstructure and dimendional change was discussed.
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