Graphite-moderated, CO2-cooled reactorSystem used to initiate, maintain and control a fission chai... type with natural uraniumUranium in the isotope composition occurring in nature, Natu... fuelSee 'nuclear fuel'. elements covered by a MagnoxCladding tube material in graphite-moderated, gas-cooled rea... sheath. ReactorSystem used to initiate, maintain and control a fission chai... type mainly built in Great Britain; e.g. Calder HallThe world's first commercial nuclear power plant in Seascale..., Chapelcross, Wylfa.