Advanced Gas-cooled Reactor (AGR) fuel pin, c 1958-1982.
© Science Museum / Science & Society Picture Library
In 1958, the United Kingdom Atomic Energy Authority (UKaeA) began work on the AGR, building a prototype at Windscale, Cumbria. Like a Magnox reactor, the core of an AGR is made of graphite and its coolant is carbon dioxide. However, the AGR operates at higher temperatures and gas presures and so it uses uranium oxide fuel clad in stainles steel. The uranium is slightly enriched.