Chapelcross Nuclear Power Station
The site of the former Chapelcross Nuclear Power Station lies near Annan in Dumfries and Galloway. The site was originally home to part of RAF Annan, a World War II airfield and Tactical Exercise Unit (TEU), and the power station was built on part of the old airfield.
Built between 1955 and 1960 by Merz and McLellan, as consultant engineers, and LJ Cowes and partners, as associate architects, the station became operational in February 1959, notable as being both the first nuclear power station in Scotland, and one of the oldest in Britain.
The station was equipped with four 50 MWe Magnox reactors, had its own processing plant nearby (the adjacent Chapelcross Processing Plant, operated by the MoD), and was designed to perform two functions: the production of weapons grade plutonium for the military, and electricity production for the civilian market.
In 1967 there was a partial meltdown in reactor No 2, and the reactor was closed for two years, then successfully restarted in 1969. The true extent of the 1967 accident was not revealed for many years, and the press were told that no radioactivity had been released. The meltdown appears to have begun with breakage of a fuel rod, which then caught fire.
In 1987, reports claimed high instances of leukaemia in the area, but later studies have challenged their veracity.
In 1996, the station's operational license was extended to 2006, but in 1998, the discovery of a forty year old hairline crack in one of the 16 heat exchangers resulted in a six month shutdown.
In 2001, a basket of spent fuel elements was dropped and lay undetected for several days, however an investigation found that apart from the delay in detecting this occurrence, there was no hazard to either plant operators or the public.
In 2003, an RAF Hercules aircraft breached the No-Fly Zone around Chapelcross. Subsequent investigation revealed that the MoD had logged five similar breaches in the preceding three years: Torness in East Lothian; Dungeness in Kent; and Berkeley in Gloucestershire, where three breaches were recorded. As the plants were not designed specifically to withstand aircraft crashes, following the events of September 11, 2001, the British Government doubled the No-Fly zone to two nautical miles.
Power production at the plant ended in 2004, to be followed by the defuelling phase, with fuel being progressively removed from the reactors and sent to Sellafield for treatment, and marking the start of the decommissioning process. The premature closure of the station was brought about by a combination of operational problems and a fall in energy prices, as the plant was dependent on the export of electricity to England.
In May 2007, the most public part of this process took place as the four 300 foot cooling towers were demolished in ten seconds by controlled explosion.
In July 2008, formal permission was given for the start of the defuelling process of the four reactors, which will take some 3.5 years.
In February 2009, the start of operations to remove the spent uranium fuel rods from the reactors was announced.
In April 2009, the first flasks carrying spent nuclear fuel from the reactors left Chapelcross, en route to the reprocessing facility at Sellafield in Cumbria. Over the next three years some 300 similar journeys will be completed, transporting 38,000 spent rods in total.
The plant was operated by government owned British Nuclear Fuels Ltd (BNFL), but transferred to the Nuclear Decommissioning Authority when decommissioning began, and had employed over 400 staff. Apart from new employment opportunities arising from the decommissioning operation (a 100 year process), there is a proposal for a wood burning power station to be constructed in the area. Fuelled by fast-growing, coppiced willow trees, and estimated to cost some £30 million, provide hundreds of jobs during the construction phase, and seventy full-time jobs on completion.
The military role
Chapelcross, and its companion plant of Calder Hall in England, owed its existence only in part to the production of energy by nuclear power, as the two plants were part of the British nuclear weapons programme. While the power plants were producing electricity, their nuclear reactors were being operated in a mode which meant they were also producing weapons grade plutonium.
The British nuclear weapons programme began during the 1940s, and production of British nuclear weapons started in 1950 using material produced in two specially constructed nuclear piles at Windscale. However, in 1958, one of the piles caught fire, resulting in Britain's worst nuclear accident to date, and the total loss of the production facility as the remaining pile was shut down as a precaution. Two nuclear power plants were commissioned to provide the materials required for the programme, with Calder Hall (on the Windscale site) being the first to become operational in 1956 (and the first to close in 2003), followed by Chapelcross, which served as one of the main source of weapons grade plutonium until 1998.
Because of its military use, reprocessing of spent fuel from Chapelcross was kept outside of international regulation. However, in 1998 the Government announced that: "All re-processing from defence reactors at Chapelcross will in future be conducted under European Atomic Energy Community (EURATOM) safeguards and made liable to inspection by the International Atomic Energy Agency (IAEA)", effectively signalling an end to military plutonium production.
Plutonium was not the only weapons grade material produced in the plant's nuclear reactors. Tritium gas is used as an essential component many nuclear weapons, boosting their yield (up to two times), or producing variable yield weapons. However, tritium's half life is only twelve years, meaning that weapons dependent on its presence must be serviced every seven or eight years to maintain their effectiveness. Prior to shutdown, Chapelcross was used to build up stores of tritium for weapons service in the coming years. When these reserves are exhausted, a similar effect will be achieved using designs which incorporate non-radioactive lithium deuteride instead
An estimated 5,000 tonnes of Magnox Depleted Uranium (MDU) was held in storage at Chapelcross, part of a military stockpile formerly intended for use in depleted uranium weapons. In 1998 Britain announced that the material at Chapelcross would no longer be considered as military material and would be placed under EURATOM and IAEA safeguards.
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