Air oxidation behavior of carbon and graphite materials for VHTR

Experimental studies were performed on the oxidation behavior of the carbon and graphite materials used for the reactor components of a VHTR. The selected sample graphites were IG-11, IG-110, PGX and TS-1621; and carbon materials were ASR-0RB, ASR-1RB and P3JHA-B. The conditions of the experiment were as follows; temperature, from 430 to 650 deg C (from 700 to 1000 deg C for IG-110); testing time, from 0.5 to 48 hours; air flow rate, from 2 to 7 1/min; Reynolds number, up to 90 (from 20 to 70 for IG-110). The following conclusion was obtained from the present study: (1) As for the graphite materials, the existence of impurities such as Ni, U, alkaline metals, Cu and Fe enhanced the oxidation reaction rate because these elements acted as the catalysts. (2) As for the carbon materials, the oxidation reaction rate was from 10 to 100 times as large as that of the graphite. The reduction of their compression strength after oxidation was also significant. (3) The oxidation behavior of graphites in the range of non-uniform oxidation above 700 deg C was very well simulated by the computer code, GRACE-T1. (Aoki, K.)