Some studies of the effect of thermal and radiolytic oxidation on the neutron small angle scattering from nuclear graphites

Abstract

The neutron small angle scattering from electrographite blocks derived from petroleum coke and a gilso carbon has been measured before and after thermal or radiolytic oxidation. For both materials thermal oxidation results in an increase in the scattering whereas radiolytic oxidation causes a decrease. These observations can be explained qualitatively in terms of our present understanding of the respective oxidation mechanisms together with reasonable assumptions concerning the porosity size distribution. In the case of the petroleum coke graphite the addition of trace quantities of methane to the CO 2 atmosphere was shown to inhibit to a comparable extent the enlargement of small pores (≈2.5–10 nm radius, but excluding from consideration the long fine needle shaped pores) and the larger ones (≈1–10 μm) which contribute most significantly to the weight loss.