Effect of helium on dislocation loop formation and radiation swelling in SiC

SiC and SiC/SiC composites are considered as candidate materials for fusion reactors. In a fusion reactor environment, helium atoms will be produced in SiC up to very high concentrations (15000-20000 at.ppm) and therefore it is very important to understand how helium effects radiation swelling of SiC. In this paper a theoretical model of the helium effect on radiation swelling of SiC is suggested. This model is based on considering of kinetic growth of dislocation loops in the matrix taking into account the effect an internal electric field formed near dislocation loops has on diffusion processes of charged point defects. The trapping of helium atoms by vacancies results in an enhanced growth rate of dislocation loops and finally a swelling increase. The theoretical results for radiation swelling are compared with the existing experimental data. It is shown that helium atoms increase the radiation swelling of SiC, especially at high temperatures.