The synthesis of graphite–glass composites intended for the immobilisation of waste irradiated graphite

Irradiated and contaminated graphite is a growing problem in the UK and around the world. Approximately 250,000 tonnes of graphite waste now exists worldwide. In order to immobilize this graphite, the material could be sintered with glass to form a glass composite material, with the aim that this material could be used on waste disposal in structural or shielding applications. Three candidate waste glasses, soda-lime silica, lead glass and borosilicate glass, were sintered in a range of atmospheres, over a range of temperatures, and with different loadings of graphite (10 wt.%, 30 wt.% and 50 wt.%). It was found that graphite would not be retained unless an inert atmosphere was used, but that solid glass–graphite composites could be made with minimal oxidation if temperatures 150 °C above their glass transition temperature were used. Soda-lime silica glasses were seen to sinter with few problems, but Pb glasses and borosilicate glasses were seen to suffer problems due to reduction and excessive crystallisation respectively. Waste loadings other than 10 wt.%, were seen not to densify, due to a combination of effects. However, composites were created with near acceptable properties.