Sellafield

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Sellafield_Reprocessing_Plant

Sellafield is the name of a nuclear site, close to the village and railway station of Seascale, operated by British Nuclear Fuels Limited (BNFL), but owned since 1 April 2005 by the Nuclear Decommissioning Authority. Sellafield is located on the coast of the Irish Sea in Cumbria, England. It houses the Thorp nuclear fuel reprocessing plant, the Magnox nuclear fuel reprocessing plant, the inactive Calder Hall Magnox nuclear power station — the world's first commercial nuclear power station, and other older nuclear facilities.

History

Windscale

The Sellafield site is built on land that was formerly part of the Windscale nuclear site, which is named after a nearby village. Windscale was owned by the United Kingdom Atomic Energy Authority. Following the breakup of the UKAEA into research (UKAEA) and production (BNFL) arms, part of the site was transferred to BNFL. In 1981 the transferred part of the site was renamed "Sellafield" ^*. The remainder of the site remains in the hands of the UKAEA and is still called Windscale. Two air-cooled, graphite-moderated Windscale reactors constituted the first British weapons grade plutonium 239 production facility, built for the British nuclear weapons program in the late 40s and the 50s.

Windscale was also the site of the prototype British Advanced gas-cooled reactor.

Since its inception Sellafield has also been host to a number of reprocessing facilities, which separate the uranium, plutonium and other fission products from spent nuclear fuel. The uranium can then be used in the manufacture of new nuclear fuel, or in applications where its density is an asset. The plutonium can be used in the manufacture of mixed oxide (MOX) fuel for thermal reactors, or as fuel for fast breeder reactors, such as the Prototype Fast Reactor at Dounreay. In the past there has been some efforts to reuse the other fission products: for example, in the mid to late 50s, Caesium137 was extracted to produce kilocurie radiotherapy sources; however, this is now treated as waste.

The Windscale Piles

Following the decision taken in January 1947 for the UK to have an independent nuclear deterent Sellafield was chosen as the location of the plutonium production plant ^*. By July of 1952 the separation plant was being used to separate plutonium and uranium from spent fuel.

Unlike the early US reactors at Hanford, which consisted of a graphite core cooled by water, the Windscale Piles consisted of a graphite core cooled by air. Each pile contained almost 2000 tonnes of graphite, and measured over 24 feet high by 50 feet in diameter. Fuel for the reactor consisted of rods of uranium metal, approximately 1 foot long by one inch in diameter, and clad in Aluminium ^*.

The Piles themselves are currently being decommissioned.

The B204 reprocessing plant

B204 was built to extract the plutonium from spent fuel as part of the effort to build the UK's atomic weapons ^*. B204 operated from 1951 until 1964, with an annual capacity of 300 tonnes of fuel (or 750 tonnes of low burnup fuel). Following the commissioning of the Magnox reprocessing plant, B204 was itself recycled to become a pre-handling plant to allow oxide fuel to be reprocessed in the new plant, and was closed in 1973.

Calder Hall nuclear power station

Calder Hall was the world's first commercial nuclear power station. First connection to the grid was on 27 August 1956, and the plant was officially opened by Queen Elizabeth II on 17 October 1956 When the station closed on 31 March 2003, the first reactor had been in use for nearly 47 years [http://www.guardian.co.uk/nuclear/article/0,2763,918724,00.html.

Calder Hall had 4 Magnox reactors capable of generating 50 MWe of power each.

However, in its early life, it was primarily used to produce weapons-grade plutonium, with two fuel loads per year, and electricity production as a secondary purpose From 1964 it was mainly used on commercial fuel cycles, but it was not until April 1995 that the UK Government announced that all production of plutonium for weapons purposes had ceased [http://www.mod.uk/publications/nuclear_weapons/accounting.htm.

The Windscale fire

In 1957 one of the twin military reactors caught fire, resulting in a release of radionuclides into the environment. It has been claimed that this was the worst nuclear accident until Three Mile Island (TMI) in 1979. However since neither event resulted in immediate casualties (unlike for example the accident at the SL-1 plant in Idaho which killed the three operators, or the prompt criticality which killed Louis Slotin in 1946) this assertion is dependent upon epidemiological assessments. Both were later overshadowed by the Chernobyl accident in 1986. An estimated 750 terabecquerels (TBq) (20,000 curies) of radioactive Iodine-131 were released, and milk and other produce from the surrounding farming areas had to be destroyed. For comparison, 250,000 terabecquerels (7 million curies) of Iodine-131 were released by Chernobyl, and only 0.55 terabecquerels (15 curies) of Iodine-131 by TMI. In comparing only Iodine-131 released as a measure of the severity of an accident care must be taken, since it is estimated that TMI released 480 petabecquerels of radioactive noble gases, and had a low Iodine-131 release.

Windscale Advanced Gas Cooled Reactor (WAGR)

The Windscale Advanced Gas Cooled Reactor (WAGR) (http://www.ukaea.org.uk/wagr/history.htm) was a prototype for the UK's second generation of reactors, the Advanced gas-cooled reactor or AGR, which followed on from the Magnox stations. The WAGR golfball is, along with the Pile chimneys, one of the iconic buildings on the Sellafield site. This reactor was shut down in 1981, and is now part of a pilot project to demonstrate techniques for safely decommissioning a nuclear reactor.

Magnox reprocessing plant

In 1964 the B205 Magnox reprocessing plant came on stream to reprocess spent nuclear fuel from the Magnox reactors The plant uses the "plutonium uranium extraction" Purex method for reprocessing spent fuel, with tributyl phosphate as an extraction agent. The Purex process produces uranium, plutonium and fission products as output streams. Over the 30 years from 1971 to 2001 B205 has reprocessed over 35,000 tonnes of Magnox fuel, with 15,000 tonnes of fuel being regenerated ^*.

HALES

Highly Active Liquor Evaporation and Storage (HALES) is a department at Sellafield. It conditions nuclear waste streams prior to transfer to the Thermal Oxide Reprocessing Plant plant.

Thermal Oxide Reprocessing Plant

Between 1977 and 1978 an inquiry was held into an application by BNFL for outline planning permission to build a new plant to reprocess irradiated oxide nuclear fuel from both UK and foreign reactors. The inquiry was to answer three questions: "1. Should oxide fuel from United Kingdom reactors be reprocessed in this country at all; whether at Windscale or elsewhere? 2. If yes, should such reprocessing be carried on at Windscale? 3. If yes, should the reprocessing plant be about double the estimated site required to handle United Kingdom oxide fuels and be used as to the spare capacity, for reprocessing foreign fuels?" ^*. The result of the inquiry was that the new plant, the Thermal Oxide Reprocessing Plant (ThORP) was given the go ahead in 1978, although it did not go into operation until 1994.

The "Beach Incident"

1983 was the year of the "Beach Discharge Incident" in which high radioactive discharges resulted in the closure of a beach. BNFL received a fine of £10,000 for this discharge 1983 was also the year in which Yorkshire Television produced a documentary "Windscale: The Nuclear Laundry", which claimed that the low levels of radioactivity that are associated with waste streams from nuclear plants such as Sellafield did pose a non-negligible risk [http://www.newscientist.com/article/mg12216693.300.html.

In its early days, Sellafield discharged low-level radioactive waste into the sea, using a flocculation process to remove radioactivity from liquid effluent before discharged. Metals dissolved in acidic effluents produced a metal hydroxide flocculent precipitate following the addition of ammonium hydroxide. The suspension was then transferred to settling tanks where the precipitate would settle out, and the remaining clarified liquor, or supernate, would be discharged to the sea. In 1994 the Enhanced Actinide Removal Plant (EARP) was opened. In EARP the effectiveness of the process is enhanced by the addition of reagents to remove the remaining soluble radioactive species. EARP has recently (2004) been enhanced to further reduce the quantities of Tc-99 released to the environment. ^*

The Vitrification Plant

In 1991 the Windscale Vitrification Plant, which converts high-level radioctive waste into glass, was opened. In this plant, liquid wastes are mixed with glass and melted in a furnace, which when cooled forms a solid block of glass.

The plant has three process lines and is based on the French AVM procedure. Principal item is an inductively heated melting furnace, in which the calcined waste is merged with glass frit (glass beads of 1 to 2 mm in diameter). The melt is placed into waste containers, which are welded shut, their outsides decontaminated and then brought into air-cooled storage facilities. This storage consists of 800 vertical storage tubes, each capable of storing ten containers. The total storage capacity is 8000 containers, and 2280 containers have been stored to 2001.

The Sellafield MOX Plant

Construction of the Sellafield MOX Plant was completed in 1997. Mixed oxide, or MOX fuel, is a blend of plutonium and natural uranium or depleted uranium which behaves similarly (though not identically) to the enriched uranium feed for which most nuclear reactors were designed. MOX fuel is an alternative to Low enriched uranium (LEU) fuel used in the light water reactors which predominate in nuclear power generation. MOX also provides a means of burning weapons-grade plutonium (from military sources) to produce electricity.

2005 Thorp plant leak

On April 19 2005 83,000 litres of radioactive waste was discovered to have leaked in the Thorp reprocessing plant from a cracked pipe into a huge stainless steel-lined concrete sump chamber built to contain leaks.

A discrepancy between the amount of material entering and exiting the Thorp processing system had first been noted in August 2004. Documentation of this finding was not passed up to the appropriate administrator.

Other indicators of a problem included a rise in temperature in the sump chamber and findings of radioactive fluid there, but these were ignored. The spill was recognized only after another audit suggested that further material was missing, prompting plant operators, after several days' delay, to train an automated camera on the faulty pipe and to actually measure the volume of liquid in the sump.

Responsible administrators have been disciplined. Some 19 tonnes of uranium and 160 kilograms of plutonium dissolved in nitric acid has been pumped from the sump vessel into a holding tank away from the now-closed Thorp plant. Radiation levels in the tank cell preclude entry of humans and robotic repair of the leak may be prohibitively difficult. Officials are considering bypassing the faulty tank to resume operations.

Sellafield and the local community

Sellafield directly employs around 10,000 people and is one of the two largest, non-governmental, employers in West Cumbria (along with BAE Systems at Barrow-in-Furness) ^*." target="_blank" > Because of the increase in local unemployment following any run down of Sellafield operations, the Nuclear Decommissioning Authority (and HMG) is concerned that this needs to be managed [http://www.gnn.gov.uk/environment/detail.asp?ReleaseID=133995&NewsAreaID=2&NavigatedFromDepartment=False.

Sellafield Visitors' Centre

Close to the Sellafield site is the Sellafield Visitors' Centre, which has a number of interactive exhibits, science workshops, and Europe's first immersion cinema. The visitors' centre was given a major update by the Science Museum in London, with the aim of provoking debate about power provision in the 21st century.

Controversy

The site has been the subject of much controversy because of discharges of radioactive material, mainly accidental but some alleged to have been deliberate. Since the early 1970s and the rise of the Environmental movement in the US and Europe, there has also been general scepticism of the nuclear industry. In part this has not been helped by the industry's early connections to the nuclear weapons programme.

In the hasty effort to build the 'British Bomb' in the 1940s and 1950s, radioactive waste was diluted and discharged by pipeline into the Irish Sea. Some claim that the Irish Sea remains one of the most heavily contaminated seas in the world because of these discharges, although the relatively small size of the sea will also contribute to this. (1) claims that 250 kg of plutonium has been deposited in the marine sediments surrounding the site, although other sources put the total 60% lower Cattle and fish in the area are contaminated with plutonium-239 and caesium-137 from these sediments and from other sources such as the radioactive rain that fell on the area after the Chernobyl disaster and the results of atmospheric atomic weapons tests prior to the partial test ban treaty in 1963. Most of the area's long-lived radioactive technetium comes from the reprocessing of spent nuclear fuel at the Sellafield facility. [http://www.radiochem.org/paper/JN41/j041Tagami.pdf.

Technetium-99 is a radioactive element which is produced by nuclear fuel reprocessing, and also as a byproduct of medical facilities (for example Ireland discharges approximately 6.78GBq of Technetium-99 each year despite not having a nuclear industry ^*). Because it is almost uniquely produced by nuclear fuel reprocessing, Technetium-99 is an important element as part of the Oslo Convention for the North-East Atlantic (OSPAR) since it provides a good tracer for discharges into the sea.

In itself, the technetium discharges do not represent a significant radiological hazard and recent studies have noted "...that in the most recently reported dose estimates for the most exposed Sellafield group of seafood consumers (FSA/SEPA 2000), the contributions from 99Tc and actinide nuclides from Sellafield (<100 µSv) was less than that from 210Po attributable to discharges from the Whitehaven phosphate processing plant and probably less than the dose from naturally occurring background levels of 210Po." British Nuclear Group (the licencing company for Sellafield) have recently commissioned a new process in which Technetium-99 is removed from the waste stream and vitrified in glass blocks [http://www.britishnucleargroup.com/content.php?pageID=31&nID=706" target="_blank" >^*.

There has been concern that the Sellafield area will become a major dumping ground for unwanted nuclear material, since there are currently no long-term facilities for storing High-Level Waste (HLW), although the UK has current contracts to reprocess spent fuel from all over the world. However contracts signed since 1976 between BNFL and overseas customers require that all HLW be returned to the country of origin. The UK retains low- and intermediate-level waste resulting from its reprocessing activity, and instead ships out a radiologically equivalent amount of its own HLW. This substitution policy is intended to be environmentally neutral and to speed "return" of overseas material by reducing the number of shipments required, since HLW is far less bulky. ^*

Leukemia risks

In the early 1990s, concern was raised in the UK about apparent clusters of leukemia near nuclear facilities. Detailed studies carried out by the Committee on Medical Aspects of Radiation in the Environment (COMARE) in 2003 found no evidence of raised childhood cancer around nuclear power plants, but did find an excess of leukaemia and non-Hodgkin's lymphoma (NHL) near other nuclear installations including Sellafield, AWE Burghfield and UKAEA Dounreay. COMARE's opinion is that "the excesses around Sellafield and Dounreay are unlikely to be due to chance, although there is not at present a convincing explanation for them". [http://www.bnfl.co.uk/index.aspx?page=717. In earlier reports COMARE had suggested that "..no single factor could account for the excess of leukaemia and NHL but that a mechanism involving infection may be a significant factor affecting the risk of leukaemia and NHL in young people in Seascale."

Irish objections

Sellafield has been a matter of some consternation in Ireland, with the Irish Government and some members of the population concerned at the risk that such a facility may pose to the country. The Irish government has made formal complaints about the facility, and recently came to a friendly agreement with the British Government about the issue, as part of which the Radiological Protection Institute of Ireland and the Irish police force (An Garda Síochána) are now allowed access to the site. However, Irish government policy remains that of seeking the closure of the facility.

Fallout, a programme shown on the Irish national TV station RTÉ was a documentary-style drama showing the possible effects of a serious accident at Sellafield. This programme highlighted the fact that an accident could cause long scale contamination of Ireland's most densely populated area, including its capital city, Dublin.

Norwegian objections

Similar sentiments are shared by the Norwegian government and population, because the prevailing sea currents transport radioactive materials leaked into the sea along the entire coast of Norway. Water samples show increases of up to ten times of such materials as Tc-99. This is of great concern to the fishing industry, because they fear for the reputation of Norwegian fish, even though the radiation levels have not been conclusively proved as dangerous for the fish. The Norwegian government is also seeking closure of the facility.

Plutonium records discrepency

On February 17, 2005, the UK Atomic Energy Authority reported that 29.6 kg (65.3 lb) of plutonium, enough to make seven nuclear bombs, was unaccounted for in auditing records at the Sellafield nuclear fuel reprocessing plant. The operating company, the British Nuclear Group, described this as a discrepancy in paper records and not as indicating any physical loss of material. They pointed out that the error amounted to about 0.5%, whereas IAEA regulations permit a discrepancy up to 1% as the amount of plutonium recovered from the reprocessing process never precisely matches the pre-process estimates. The inventories in question were accepted as satisfactory by Euratom, the relevant regulatory agency. (BBC) (BNFL's response LINK NO LONGER ACTIVE).

Sellafield in art

German band Kraftwerk opened the song Radioactivity on their June 2005 live album Minimum-Maximum with an audio clip criticizing the Sellafield-2 reactor for radiation released into the atmosphere during typical operation and the dangers of reprocessing plutonium in regard to nuclear proliferation. Sellafield-2 was the name given by environmental groups including Greenpeace to a proposed second plant to reprocess oxide fuel (it is not obvious how seriously proposed, a public enquiry was never opened).

References

The worst accident in the world : Chernobyl, the end of the nuclear dream, by Nigel Hawkes, Pan Books : W. Heinemann (1986), ISBN 0330297430
Technetium-99 Behaviour in the Terrestrial Environment - Field Observations and Radiotracer Experiments, Keiko Tagami, Journal of Nuclear and Radiochemical Sciences, Vol. 4, No.1, pp. A1-A8, 2003
The excess of childhood leukaemia near Sellafield: a commentary on the fourth COMARE report, L J Kinlen et al 1997 J. Radiol. Prot. 17 63-71

External links

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