Thermal Oxidation and Subsequent Characterisation of Gilsocarbon Nuclear Graphite

Abstract

Gilsocarbon is a graphite grade used as a main structural proponent of the current UK fleet of Advanced Gas-Cooled Reactors. In this research, multiple gilsocarbon graphite samples were thermally oxidised in an attempt to simulate the effects on the graphite of radiolytic oxidation, which occurs in the reactors core. A combined technique of characterising virgin and thermally oxidised samples was taken, the Grand-canonical Monte-Carlo data from gas adsorption isotherms and mercury porosimetry intrusion data, giving percolation characteristics across the entire pore range of the graphite by stitching this data together via the simulation software PoreXpert. It was confirmed that oxidation did increase the specific pore volume significantly within the oxidised sample. The majority of this increased pore-volume was found to be from the creation of new smaller features by oxidation, while smaller void-structures were also found to coalesce to increase the number of larger pores present too. This information will allow future work to more easily draw parallels or see differences between thermal and radiolytic oxidation of gilsocarbon, further developing the current models pertaining to the radiolytic oxidation of nuclear graphite.