Building of the plant started
in 1965 and it came on-line in 1983. There are two AGR reactors that are
expected to be decommissioned in 2018.
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. 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.
On 31 December 2006 the A
Station ceased power generation. It is anticipated that defuelling will be
completed by 2009, the turbine hall demolished in 2010 to be replaced by an
intermediate level waste store in 2014. The waste store and reactor building
will then be placed on a care and maintenance basis until 2103, with final site
clearance and closure by 2111. Decommissioning is estimated to cost £1.2
billion. An alternative proposal has been made to accelerate cleanup for
completion by 2030.
Dungeness B
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.
The station's accounting
closure date is 2018, 35 years after first power generation. Life-extension
options may be considered prior to this date.
Text source:
Wikipedia