Advanced gas-cooled reactor
An Advanced Gas-cooled Reactor (AGR) is a specific type of nuclear reactor. These are the second generation of British gas-cooled reactors, using graphite as the neutron moderator and carbon dioxide as coolant. The AGR was developed from the Magnox reactor, and operates at a higher gas temperature for improved thermal efficiency, but requires stainless steel fuel cladding to withstand the higher temperature. Because the stainless steel fuel cladding has a higher neutron capture cross section than Magnox fuel cans, enriched uranium fuel is needed, with the benefit of higher "burn ups" of 18,000 MWt-days per tonne of fuel, requiring less frequent refuelling. The first prototype AGR became operational in 1962 but the first commercial AGR did not come on line until 1976.