graphite-moderated reactor

A graphite-moderated reactor is a type of nuclear reactor that uses graphite as a moderator. The moderator's role is to slow down fast neutrons produced during nuclear fission, making them more likely to cause further fission events in the fuel.1

The first self-sustaining nuclear chain reaction was achieved in Chicago Pile No. 1 (CP-1) in 1942, which was a graphite-moderated reactor using uranium metal slugs and uranium oxide lumps. Graphite's ability to moderate neutrons efficiently, along with its structural properties, made it a key material in early reactor designs. Advanced gas-cooled reactors (AGRs) also utilize graphite as a moderator, with fuel pins inserted into channels within the graphite block. While graphite's moderating properties are beneficial, it can also experience structural changes and swelling under neutron irradiation within a reactor.2134