Gas-cooled, graphite-moderated nuclear reactors suffer ageing and degradation to the graphite during service posing a threat to the functionality of the core, and potentially, the safe operation of the reactor. Thus, the importance of modelling and measuring reactor core graphite properties and performance increases especially as continued use beyond the designed life time becomes significant. This book captures the proceedings from the third in a series of meetings addressing the extensive research and analysis performed to ensure the continuing safe performance of the graphite cores. Covering four broad themes: mechanistic; statistical; empirical; and, plant performance, this book should appeal to a broad range of readers from engineers and reactor operators to policy makers.