Dungeness Nuclear Power Station

Dungeness A Nuclear Power Station
Dungeness A
Country	England
Location	Kent, South East England
Coordinates	50°54′50″N 0°57′50″E / 50.913889°N 0.963889°E / 50.913889; 0.963889Coordinates: 50°54′50″N 0°57′50″E / 50.913889°N 0.963889°E / 50.913889; 0.963889
Status	Decommissioning, B
Commission date	1965
Decommission date	2006
Owner(s)	NDA
Operator(s)	Magnox Ltd
Nuclear power station
Reactor type	Magnox
Reactor supplier	The Nuclear Power Group
Thermal power station
Primary fuel	Nuclear
Power generation
Units decommissioned	2 X 219 MWe net
Nameplate capacity	500 MWe
Website www.magnoxsites.co.uk/site/dungeness-a/
grid reference TR0832016959

Dungeness B Nuclear Power Station
Dungeness B
Country	England
Location	Kent, South East England
Coordinates	50°54′50″N 0°57′50″E / 50.913889°N 0.963889°E / 50.913889; 0.963889
Status	Operational, O
Construction began	1965
Commission date	1983
Decommission date	Expected 2028
Operator(s)	EDF Energy
Nuclear power station
Reactor type	Advanced gas cooled reactor
Reactor supplier	Fairey Engineering Ltd
Thermal power station
Primary fuel	Nuclear
Power generation
Units operational	2 x 600 MWe (Operating at ~545 MWe net[1] )
Nameplate capacity	1090 MWe
Website www.edfenergy.com/energy/power-stations/dungeness-b
grid reference TR0832016959

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

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.^[2] The construction was undertaken by a consortium known as the Nuclear Power Group ('TNPG').^[3] The reactors were supplied by TNPG and the turbines by C. A. Parsons & Co.^[2]

On 31 December 2006 the A station ceased power generation. Defuelling was completed in June 2012^[4] and the demolition of the turbine hall was completed in June 2015.^[5] It is expected to enter the 'care and maintenance' stage of decommissioning in 2027.^[4]

Dungeness B

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'),^[6] a consortium backed by Crompton Parkinson, Fairey Engineering, International Combustion and Richardsons Westgarth.^[3] 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.^[7] 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.^[8] 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.^[9] 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.^[10] By 1979 the cost had risen further to £410 million.^[11] 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.^[12]

As with the "A" station, the turbines were built by C.A. Parsons & Company^[2] 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.^[13]

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.^[14][15] 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.^[16][17][18] Unplanned shutdowns continued into 2011,^[19][20] with B21 down for repairs from November 2011 to March 2012.^[21]

In 2005, the station's accounting closure date was extended by ten years, which would allow it to continue operating until 2018, 35 years after first power generation.^[22] 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.^[23]

Consideration of Dungeness C

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.^[24] 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.^[25] 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.^[26] Despite these environmental concerns, local Conservative MP Damian Collins, supported by some residents, lobbied Parliament to reconsider that position.^[27][28]

HVDC station

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.

Ownership

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.

Location

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. 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.^[29] 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 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.^[29]

See also

• Nuclear power in the United Kingdom
• Energy policy of the United Kingdom
• Energy use and conservation in the United Kingdom

References

Other sources

1. Eddison, J (2000). Romney Marsh Survival on a Frontier. Tempus. ISBN 0-7524-1486-0. Page 139 also reports the 1990 flooding mentioned above. Page 139 also reports the 1990 flooding mentioned above.
2. "Romney Marsh". Retrieved 5 February 2006.
3. "Kent Against a Radioactive Environment". Archived from the original on 24 April 2006. Retrieved 20 March 2006.
4. "British Energy". Archived from the original on 28 September 2007. Retrieved 16 April 2006.
5. "industcards". Retrieved 16 April 2006.
6. "Going Critical" (PDF). Retrieved 16 April 2006.

External links

Wikimedia Commons has media related to Dungeness Nuclear Power Station.

• Dungeness A information page From the NDA.
• Dungeness B information page From EDF Energy.
• Kent Against a Radioactive Environment Local web site opposing the power stations.
• Photographs of Dungeness A From the British Nuclear Group image asset library.