Reaction of boron carbide with oxygen and the effect of preirradiation in a nuclear reactor

Abstract

The kinetics of the oxidation of boron carbide between 503 and 528° have been studied by continuous measurement of weight change. The rate of oxidation reached a maximum at about 12% weight increase and this was maintained up to about 35% weight increase; the rate then decreased, the weight increase becoming proportional to the square root of time. At this stage the rate was controlled by a diffusion process. The activation energies for the initial and maximum rates were 37·2 (±1·5) and 39·9 (±0·5) kcal./mole respectively. Preirradiation of the boron carbide in BEPO enhanced the subsequent rate of oxidation. The initial acceleration of the reaction rate is attributed to splitting of crystals by oxidation along grain boundaries. Preirradiated crystals are more easily split than unirradiated crystals.