Behavior of SiC at high temperature under helium with low oxygen partial pressure

摘要

The behavior of SiC at high temperature under helium with low oxygen partial pressure is a key factor for its application as structural material in Gas-cooled Fast Reactors (GFR). After a literature study on the active-passive transition in the oxidation of SiC, a numerical study reproducing environments of the future reactors was realized with GEMINI software to evaluate SiC behavior under helium with low oxygen partial pressure (0.5-3500 Pa). It was found that increasing the partial pressure of oxidant pushes the passive to active transition to higher temperature and suppresses the vaporization of SiC. These results are in agreement with the calculation using the Wagner model. Experimental tests at high temperature (1300-2000 K) on massive SiC samples (sintered a and beta CVD), coupled to SEM, XPS and XRD analyses before and after oxidation tests are presented. They show that the level of oxidizing species has an important impact on the physico-chemical behavior of SiC as was also predicted by thermodynamic calculation. In addition, for the mass loss with time, the crystallographic structure is an important factor. Silicon carbide is a promising structural material for Generation IV nuclear reactors. Because of its mechanical and physico-chemical properties, it maintains its structural integrity at high temperature in helium environment with low oxygen partial pressure.