This section of Chapter 12 looks at the design of the advanced gas-cooled reactor (AGR), which was chosen by the Central Electricity Generating Board as the succession plant to the Magnox reactors in the early 1960s instead of either the pressurised water reactor or the boiling water reactor.

The commercial AGR (CAGR) was developed from a prototype built at Windscale (WAGR), which was operated by the United Kingdom Atomic Energy Authority (UKAEA). There are a number of similarities between the AGR and the Magnox designs in that both are cooled by pressurised carbon dioxide and moderated by graphite. The fuel designs are quite different, however, because the AGR operates at higher temperature and is, therefore, more thermally efficient.

The first commercial AGR commenced construction at Dungeness in Kent on the site alongside an existing Magnox station, which has since closed down. The contract for a pair of reactors was awarded in 1965 and was closely followed, around 1967, by orders for stations at Hinkley Point in Somerset and at Hunterston, a replica design, in Ayrshire. As at Dungeness, both sites already had existing Magnox reactors on them. Different designs were chosen for the next stations at Hartlepool on Teesside and at Hey sham in Lancashire in 1969 and 1970 respectively. Neither of these sites had Magnox plant. The final two AGR stations constructed were on the same Heysham site and at Torness and were ordered nearly ten years later. These are again sister stations and are of a design similar to the reactors at Hinkley Point and Hunterston. All AGRs on sites with Magnox plant were termed the ‘B’ station. The Heysham AGRs are named ‘1’ and ‘2’. All AGR stations consist of a pair of reactors in a single building. They have a common service island for fuel handling and equipment maintenance and which is either between the two reactors or at the end of the building in the case of Hartlepool and Heysham.