Permeability of helium gas of Silicon carbide ceramic composites material, which is one of the most important properties in application of SiC composite for advanced reactors, is studied by using a simple, low-cost test system. The test system can not only qualitatively determine whether the sample is permeable or not, but also quantitatively measure the permeability for the permeable ones by water displacement. The tests are conducted with low pressure in room temperature. The permeability of the SiSiC composite depends on the preparation method. In four flat-plate materials prepared by different processes for the test, the splint based SiSiC and cordierite coated fiber reinforced SiSiC are hermetic, the permeability of uncoated fiber reinforced SiSiC and CVD carbon coated fiber reinforced SiSiC are 0.216cm2/s and 0.109cm2/s, which imply that the permeability is cut in half with the coating. The samples are scanned under SEM to analyze their microscopic structures and verified that the difference of permeability is related to their coatings as well as the pores and cracks.
