Dungeness B is an advanced gas-cooled reactor (AGR) power station consisting of two 615 MW reactors, which began operations in 1983 and 1985 respectively. Dungeness B was the first commercial scale AGR power station to be constructed, the design being based on the much smaller Windscale AGR prototype; the WAGR. The £89 million contract was awarded in August 1965 to Atomic Power Construction ('APC'), a consortium backed by Crompton Parkinson, Fairey Engineering, International Combustion and Richardsons Westgarth. The completion date was set as 1970.
During construction, many problems were encountered in scaling up the WAGR design. Problems with the construction of the pressure vessel liner had distorted it such that the boilers, which were to fit in an annular space between the reactor and the pressure vessel, could not be installed, and the liner had to be partially dismantled and re-built. Although the cost of this work was relatively minor at about £200,000, the cost of financing for an extra 18 unproductive months a power station costing around £100 million of which some 60 per cent was already on the ground, was massive. Serious problems with the design of the boilers, which had to withstand the pounding of hot carbon dioxide (CO2), pressurised to 600psi and pumped around the reactor coolant circuit by massive gas circulators, were also discovered, and the casings, hangers and tube supports all had to be redesigned. The cost of these modifications, and financing during the delays, caused severe financial pressures to the consortium and its backers, and in 1969 APC collapsed into administration.
The CEGB took over project management, issued light penalties in order not to cripple Fairey and International Combustion, and appointed British Nuclear Design and Construction (BNDC) as main contractor. In 1971, problems with corrosion of mild steel components in the first generation Magnox reactors gave the designers cause for concern. The Dungeness B restraint couplings - mechanical linkages that held the graphite core in place whilst allowing it to expand and contract in response to temperature changes - were made of mild steel and could be subject to the same corrosion. A decision was made to replace them with components made from a new material. In 1972, problems with the use of galvanised wire that was used to attach thermocouples to stainless steel boiler tubes were discovered. During heat treatment of the tubes at temperatures up to 1,050oC, the galvanising zinc diffused into the tubes and made them brittle. The cost had by then risen to £170 million. By 1975, the CEGB was reporting that the power station would not be completed until 1977 and that its cost had risen to £280 million. By 1979 the cost had risen further to £410 million. Reactor 1 first generated power on 3 April 1983, some 13 years behind schedule and at a cost of £685 million, four times the initial estimate in inflation adjusted terms.
Like the "A" station, its turbines were built by C.A. Parsons & Company and it has two 600 MWe turbo-alternator sets, producing a maximum output of 1200 MWe, though net output is 1090 MWe after the effects of house load, and downrating the reactor output due to corrosion and vibration concerns.
In March 2009 Unit B21 was brought down for maintenance; serious problems were found and the reactor was shut down for almost 18 months. On 24 November 2009 a small fire in the boiler annexe of Unit B22 caused the second reactor to also be shut down. Subsequently Unit B22 has been intermittently offlined for periods of up to several months. Unit B21 was restarted in August 2010. Unplanned shutdowns continued into 2011, with B21 down for repairs from November 2011 to March 2012.
The station's accounting closure date is 2018, 35 years after first power generation. Life-extension options may be considered prior to this date.
Read more about this topic: Dungeness Nuclear Power Station