Compatibility of CVD SiC and SiCf/SiC Composites with High Temperature Helium Simulating Very High Temperature Gas-Cooled Reactor Coolant Chemistry

Effect of dissolved hydrogen on the corrosion behavior of chemically vapor deposited SiC in a simulated pressurized water reactor environment

“…4 and 5 display the AFM surface morphology and roughness of CVD SiC specimens, respectively, before and after the corrosion tests with the control of dissolved hydrogen. In general, the corrosion of SiC, or the formation of SiO 2 , causes an increase in surface roughness because of the local corrosion (pitting or grain boundary attacks) and the inhomogeneous growth of SiO 2 [7,28]. However, there was no meaningful change in surface morphology and roughness after the corrosion tests, based on the AFM results in Figs.…”

“…7 shows the chemical states at the surface of CVD SiC determined by XPS analysis before and after corrosion tests. The Si 2p 1/2,3/2 peak of the as-ground specimen can be distinguished by three peaks, which were attributed to the very thin native oxide and the SiC bulk beneath the oxide layer [7], as shown in Fig. 7(a).…”

“…They also have attractive properties regarding nuclear applications, including a low neutron absorption cross-section, low induced activation, and high resistance to neutron irradiation. Therefore, SiC has been considered for use in reactor cores for such as a constituent coating layer of tristructural-isotropic (TRISO) fuel particles and a control rod sheath as a form of the composite in very high temperature gas-cooled reactors, as well as for blanket structural materials and flow channel inserts in nuclear fusion reactors [5][6][7][8][9][10].…”

Effect of irradiation damage on hydrothermal corrosion of SiC

“…For example, the surface may be passivated naturally through reactions with oxygen and water from ambient air or an abrasive suspension, decreasing the density of the dangling bonds at the surface. Indeed, multiple peaks containing Si-O and Si-C bonding have been reported for an as-polished SiC surface using X-ray photoelectron spectroscopy (XPS) analyses [22]. Although information on the thickness of the oxide layer in this case was not provided in [22], the thickness should be less than 10 nm considering the escape depth of photoelectrons.…”

“…Indeed, multiple peaks containing Si-O and Si-C bonding have been reported for an as-polished SiC surface using X-ray photoelectron spectroscopy (XPS) analyses [22]. Although information on the thickness of the oxide layer in this case was not provided in [22], the thickness should be less than 10 nm considering the escape depth of photoelectrons. As a concluding remark to this section, no significant changes in the surface roughness, chemistry, and intrinsic structure were detected at the surfaces of the specimens irradiated with Si ions by the AFM, cross-sectional TEM for Step height [nm]…”