High temperature oxidation of SiC under helium with low-pressure oxygen—Part 1: Sintered α-SiC

Gas-cooled Fast Reactor (GFR) is one system of the Generation IV International Forum systems studied by CEA (France). The considered coolant, helium, is pressurized at 7 MPa and the nominal working temperature is about 1300 K. In case of accident, reactor temperatures can reach 1900–2300 K. Several studies are carried out to determine the physico-chemical behavior of structural and cladding materials undergoing various environmental constraints. The cladding materials currently considered are refractory carbides, and particularly silicon carbide, SiC. Experimental tests at high temperature (1400–2100 K) on massive α-SiC samples coupled to mass variation, SEM and roughness analyses enabled to determine the transition between passive and active oxidation regimes, and to study the resistance to corrosion of such material in some conditions encountered in case of accident (high temperature increase up to 2300 K). The transition between passive and active oxidation obtained experimentally appears at 1300 K for an oxygen partial pressure of 0.2 Pa and at 1600 K for 100 Pa. The experimental mass loss rate obtained for conditions encountered during an accident – active oxidation – have shown that a maximal oxygen partial pressure of 10 Pa in helium is well suited to avoid a huge degradation of the α-SiC.