Burn-off and production of CO and CO2 in the oxidation of nuclear reactor-grade graphites in a flow system

Abstract

The oxidation behaviors of IG-110 and PGX graphites were investigated experimentally at 500-1,500°C for the oxygen concentration of 10 and 30 wt% (1.37 and 5.09 mol%) and the reacting gas velocities of 6.63 and 19.9 m/s (estimated at 900°C). The graphite specimens were prepared to simulate the annular coolant channel in the core of the HTGR. It has been found that the upstream surface is more oxidized for both IG-110 and PGX graphites, and that the oxidized surface of PGX is rougher than that of IG-110. The oxidation of IG-110 starts at about 700°C and reaches the maximum above 800-900°C accompanied by the maximum production of CO2 around 850°C and a monotonic increase in CO with increasing temperature. The oxidation behavior of PGX is similar to that for IG-110, except that the oxidation starts at lower temperature and produces more CO2 over 750-950°C while the concentration of CO becomes lower in this temperature range.