IMPURITIES AND EVALUATION OF INDUCED ACTIVITY OF SIC COMPOSITES PREPARED WITH CHEMICAL-VAPOR INFILTRATION

Carbon fiber reinforced SiC (C/SiC) and SiC fiber reinforced SiC (SiC/SiC) composites were fabricated by a chemical vapor infiltration (CVI) method to obtain the composites with minimized impurity contamination. The neutron activation analysis showed that 30 elements were detected as impurities. However total impurity concentrations in the C/SiC and SiC/SiC were lower than 14.5 wt ppm and 9.80 wt ppm, respectively. The evaluation of induced activity under the simulation of fusion neutron irradiation of 10 MW.y/m(2) was made based on the impurity concentration. The dose rates of both composites were assumed to decrease by about 6 orders of magnitude in one day cooling and by 9 orders of magnitude in several ten years. The results indicate that the present composites behave excellent in terms of low activation and the CVI is a potential process to obtain high-purity composites.