External view of the reactor building at Heysham II nuclear power station near Morecambe, Lancashire, UK. Commissioned in 1988, Heysham II houses two Advanced Gas-cooled Reactors (AGRs). Each reactor core consists of a graphite cylinder containing many thousands of oxide fuel pins; stainless steel tubes containing pellets of enriched uranium dioxide. Heat is generated by nuclear fission within the uranium. Carbon dioxide gas is pumped through the core, cooling it and transfering the heat to four boilers. Steam, produced at high temperature and pressure within the boilers, drives a turbine generator to produce electricity.