In the final hours of 2006 the Sizewell A and Dungeness A plants were shut down for the last time. The plants' four Magnox reactors were the longest-serving in the world.
Dungeness A, on the Kent coast, hosts two 220 MWe Magnox reactors, as does its sister plant Sizewell A on the Suffolk coast. The plants began generating electricity in 1965 and 1966 respectively and their age of 40 years established their four reactor units as the oldest operating in the world at the time of their final shutdown, 31 December 2006.
The plants and their sites are owned by the Nuclear Decommissioning Authority and operated by Reactor Sites Management Company , a part of British Nuclear Group which is to be sold off as part of the greater break-up of BNFL.
Sizewell A was recognised in 2005 as the safest industrial facility in the world by Det Norske Veritas (DNV) under its International Safety Rating System. DNV, a firm of independent risk management consultants established in 1864 with the primary objective of safeguarding life, property and the environment, had never before awarded any facility Level 10.
Both 'A' power stations have a 'B' neighbour. Dungeness B is comprised of two Advanced Gas-cooled Reactors (AGRs) which began operating in 1985 and 1989, while Sizewell B is the 's only pressurized water reactor (PWR), and began operation in 1995.
Under decommissioning plans approved by the Nuclear Installations Inspectorate, the first steps would be to remove used fuel from the plants to Sellafield for reprocessing. That process would take until about 2009, while demolition of the turbine halls would be completed around 2017. Initial plans would have the sites finally cleared only by about 2110. However, discussions are ongoing with nearby residents at Sizewell-cum-Leiston who would like to see the Sizewell A site decommissioned to a greenfield state by 2032.
The shutdown of these four old and small reactors reduces UK generation capacity by about 1% and set s nuclear's share of the total at about 19%. As Generation-I Magnox reactors and Generation-II AGRs are shut down over the years up to 2023, the Sizewell B PWR will be left as Britain's only nuclear power station.
British Nuclear Group
Det Norske Veritas
Nuclear Installations Inspectorate
Nuclear Decommissioning Authority
WNA's Nuclear Power in the United Kingdom information paper