Wylfa Nuclear Power Station
Wylfa is a nuclear power station situated just west of Cemaes Bay on the island of Anglesey, north Wales. Its location on the coast provides an excellent cooling source for its operation. It is named Wylfa as a local resident David Hughes, who went on to become a prominent builder in Liverpool and build Cemaes town hall, had his cottage named Wylfa on the site in the late 19th century.
Wylfa houses two 490 MW Magnox nuclear reactors, "Wylfa-1" and "Wylfa-2", which were built from 1963 and became operational in 1971.
They have a combined capacity of 980 MW and Wylfa typically supplies 23 GW•h of electricity daily. It is the largest and last reactor of its type to be built in the UK. It was the second British nuclear power station, following Oldbury, to have a pre-stressed concrete pressure vessel instead of steel for easier construction and enhanced safety.
The original design output was 1,190 MW but unexpected accelerated ("breakaway") corrosion of mild steel components of the gas circuit in hot CO2 was detected even before the first reactor began operating. The channel gas outlet temperature, the temperature at which the CO2 leaves the fuel channels in the reactor core, had to be reduced, initially dropping the power output to 840 MW, which was later raised to 980 MW as more experience accumulated.
The graphite cores each weigh 3,800 tonnes, 6,156 vertical fuel channels contain over 49,248 natural uranium magnox clad fuel elements, hence the name magnox reactor. A further 200 channels allow boron control rods to enter the reactor and control the nuclear reaction. The primary coolant in the reactors is carbon dioxide gas.
The reactors were supplied by The Nuclear Power Group ('TNPG') and the turbines by English Electric.
The power station is operated by Magnox North Ltd. The site is owned by the Nuclear Decommissioning Authority (NDA). Its purpose is to oversee and manage the decommissioning and clean-up of the UK’s civil nuclear legacy.
On 20 July 2006 the NDA announced that the station will be shut down in 2010 because operation beyond then would be "totally uneconomic". However recently (25 February 2009) the NDA has begun considering a potential extension to Wylfa's life expectancy.
A second plant (generally referred to as Wylfa B) has been proposed, in part to provide for the needs of the Anglesey Aluminium smelter located in Holyhead. This proposal has been the subject of some local opposition, led by the group People Against Wylfa B ([PAWB] - "pawb" is Welsh for "everyone"). The subsidised electricity supply to the smelter company will end, even if the life of the nuclear station is extended by a year or two. Substantial works were needed to strengthen the reactors against deteriorating welds discovered in the safety review in April 2000. Amid public controversy, Greenpeace issued an independent safety appraisal by the nuclear engineering consultancy, Large Associates, but the permit to restart operation was given in August 2001. In addition to welding weaknesses, radiolytic depletion of the graphite moderator blocks was still of concern and PAWB continue to campaign for early shut-down of the plant as well as against any nuclear replacement. Nevertheless, in March 2006 the local council voted to extend the life of Wylfa A and to support the construction of Wylfa B, citing the potential loss of employment in the smelter works and nuclear station.