Dungeness Nuclear Power Station
Dungeness nuclear power station may refer to either one or both of a pair of nuclear power stations, only one of which is still operational, located on the Dungeness headland in the south of Kent, England. Dungeness A is a legacy Magnox power station that was connected to the National Grid in 1965 and has reached the end of its life. Dungeness B is an advanced gas-cooled reactor (AGR) power station consisting of two 615 MW reactors, which began operation in 1983 and 1985 respectively, and have been non-operational since 2018 due to ongoing safety concerns.
|Dungeness A Nuclear Power Station|
|Location||Kent, South East England|
|Nuclear power station|
|Reactor supplier||The Nuclear Power Group|
|Thermal power station|
|Units decommissioned||2 X 219 MWe net|
|Nameplate capacity||500 MWe|
|Commons||Related media on Commons|
|Dungeness B Nuclear Power Station|
|Location||Kent, South East England|
|Decommission date||Expected 2028|
|Nuclear power station|
|Reactor type||Advanced gas cooled reactor|
|Reactor supplier||Fairey Engineering Ltd|
|Thermal power station|
|Units operational||2 x 600 MWe (Operating at ~545 MWe net )|
|Nameplate capacity||1090 MWe|
|Commons||Related media on Commons|
There were many problems during construction of the second power station, which was the first full-scale AGR. It was supposed to be completed in 1970, but the project collapsed in 1969. The CEGB took over project management and appointed British Nuclear Design and Construction (BNDC) as main contractor. There were more problems and by 1975 the CEGB was reporting that the power station would not be completed until 1977 and the cost had risen to £280 million. By completion the cost had risen to £685 million, four times the initial estimate in inflation-adjusted terms.
In March 2009, serious problems were found when Unit B21 was shut down for maintenance, and the reactor remained out of action for almost 18 months. In 2015, the plant was given a second ten-year life extension, taking the proposed closure date to 2028.
Dungeness A is a legacy Magnox power station that was connected to the National Grid in 1965 and has reached the end of its life. It possessed two nuclear reactors producing 219 MW of electricity each, with a total capacity of 438 MW. The construction was undertaken by a consortium known as the Nuclear Power Group ('TNPG'). The reactors were supplied by TNPG and the turbines by C. A. Parsons & Co.
Nuclear fuel for Dungeness power stations can be delivered and removed via a crane loading facility at the end of the nine mile Appledore-Lydd-Dungeness branch railway. This is connected to the Ashford to Hastings line via an east-facing junction located to the west of Appledore station.
On 31 December 2006 the A station ceased power generation. Defuelling was completed in June 2012 and the demolition of the turbine hall was completed in June 2015. It is expected to enter the 'care and maintenance' stage of decommissioning in 2027.
Dungeness B is an advanced gas-cooled reactor (AGR) power station consisting of two 615 MW reactors, which began operation in 1983 and 1985 respectively. Dungeness B was the first commercial scale AGR power station to be constructed. Its design was 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, so 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 rebuilt. This work only cost about £200,000, but there was a huge cost of financing an extra 18 unproductive months for a power station costing around £100 million, of which some 60% was already on the ground. Serious problems were also discovered with the design of the boilers, which had to withstand the pounding of hot carbon dioxide (CO2), pressurised to 600 pounds per square inch (4,100 kPa) and pumped around the reactor coolant circuit by massive gas circulators. As a consequence, the casings, hangers and tube supports all had to be redesigned. The cost of the modifications, and financing during the delays, caused severe financial pressures for the consortium and its backers, and in 1969 APC collapsed into administration.
The CEGB took over project management, imposed 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. It was decided to replace them with components made from a new material. In 1972, problems were found with the galvanised wire that was used to attach thermocouples to stainless steel boiler tubes. During heat treatment of the tubes at temperatures up to 1,050°C, 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.
As with the "A" station, the turbines were built by C.A. Parsons & Company and the station 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, serious problems were found when Unit B21 was shut down for maintenance, and the reactor remained out of action for almost 18 months. On 24 November 2009, a small fire in the boiler annexe of Unit B22 caused the second reactor to be shut down as well. Subsequently, Unit B22 has been intermittently shut down for up to several months at a time. Unit B21 was restarted in August 2010. Unplanned shutdowns continued into 2011, with B21 down for repairs from November 2011 to March 2012.
In 2005, the station's accounting closure date[clarification needed] was extended by ten years, which would allow it to continue operating until 2018, 35 years after first power generation. In 2015, the plant was given another ten-year life extension, allowing an upgrade to control room computer systems and improved flood defences, taking the accounting closure date to 2028.
In September 2018 the Office for Nuclear Regulation (ONR) directed that EDF Energy carry out a reassessment of corrosion of safety-related concealed systems. Inspections showed that seismic restraints, pipework and storage vessels were found to be "corroded to an unacceptable condition", and that would have been the state when the reactor was operating. Remedial measures included the upgrading of more than 300 metres of pipeline and of carbon dioxide storage vessels. The ONR classified this as a level 2 incident on the International Nuclear Event Scale. Dungeness B was initially expected to return to service in February 2019, later put back to 30 September 2019 to complete inspections.
Consideration of Dungeness CEdit
On 15 April 2009, Dungeness was included in a list of 11 potential sites for new nuclear power stations, at the request of EDF Energy, which owns and operates Dungeness B. The government did not include Dungeness C in its draft National Policy Statement published on 9 November 2009, citing environmental reasons and concerns about coastal erosion and associated flood risk. The site was ruled out by Secretary of State for Energy and Climate Change Chris Huhne in October 2010 with the former government's list of eleven potential sites reduced to eight. Despite these environmental concerns, local Conservative MP Damian Collins, supported by some residents, lobbied Parliament to reconsider that position.
From 1961 to 1984, Dungeness power station also housed the mercury arc valves of the static inverter plant converting AC into DC for transmission on HVDC Cross-Channel, the high-voltage direct current power cable carrying electric power across the English Channel to France. In 1983, a more powerful new inverter at Sellindge replaced this facility.
Both stations were originally built, owned, and operated by the Central Electricity Generating Board (CEGB). Following privatisation of the electricity supply industry and the later part-privatisation of the nuclear power generating industry they are now owned by two different bodies: the original Magnox plant Dungeness A by the non-departmental government body the Nuclear Decommissioning Authority (NDA) and newer AGR Dungeness B by EDF through British subsidiary EDF Energy.
The stations are built on the largest area of open shingle in Europe, measuring 12 km by 6 km, which has been deposited by the sea and built up over thousands of years. The entire area is moving slowly north and east as the sea moves the shingle from one side of the headland to the other. It is surrounded by a nature reserve Site of Special Scientific Interest (SSSI). A fleet of lorries is used to continuously maintain shingle sea defences for the plant as coastal erosion would otherwise move shingle away at an estimated rate of 6 m per year. Around 30,000 cubic metres of shingle are moved each year. It seems that deposition on the north shore of the headland does not keep pace with erosion, although the power stations are about 1 km to the west of that shore. In all, 90,000 cubic metres are moved each year along parts of the coast between Pett Level and Hythe. This is necessary for the safety of the entire area including the power stations. Around 100 million litres of cooling water are extracted and returned to the sea each hour, after being heated by 12 deg Celsius (22 deg F).
The position of the power station site on the headland over time is important.[according to whom?] Geological history places the beginning of the promontory, some 3000 years ago, as shingle deposits offshore from Pett Level. From there the evidence suggests that the headland enlarged and migrated up Channel to its present position.
The headland and the coastline between Pett Level and Hythe are volatile. In recorded history Walland Marsh to the west of the power stations has been flooded. In the space of sixty years severe inundation occurred, temporarily bringing the sea inland to Appledore and the original mouth of the River Rother from north of the headland at Romney to the south at Rye Harbour. The site is a few metres above Mean Sea Level and would be isolated in the event of flooding of the magnitude that submerged large areas of East Anglia and the Netherlands in 1953. It has been conjectured[who?] that the hurricane of 1987 did not bring the sea to the stations because there was a low tide at the time. Climate change could cause more frequent and powerful storms, and associated waves and surges are possible though not probable, and might increase the instability of the headland.
In the mediaEdit
The beach was used in 2012 to test the Olympic torch.
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