Thorp nuclear fuel reprocessing plant
Encyclopedia
The Thermal Oxide Reprocessing Plant, or THORP, is a nuclear fuel reprocessing
plant at Sellafield
in Cumbria
, England. THORP is owned by the Nuclear Decommissioning Authority
and operated by Sellafield Ltd (which is the site licensee company). Spent nuclear fuel from nuclear reactor
s is reprocessed to separate the 96% uranium
and the 1% plutonium
, which can be reused in mixed oxide fuel, from the 3% radioactive wastes, which are treated and stored at the plant. The uranium is then made available for customers to be manufactured into new fuel.
Between 1977 and 1978 an inquiry was held into an application by British Nuclear Fuels plc
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, was given the go-ahead in 1978, although it was not completed until the 1990s.
raffinate
, one way in which this is done is by avoiding the use of ferrous compounds as plutonium
reducing agents. In this plant the reduction is done using either hydrazine
or HAN (hydroxylamine
nitrate
).
Altogether 83 cubic metre
s (18,250 imperial gallons) of nitric acid
solution leaked from a small fractured feedpipe, which was discovered when a remote camera was sent in to examine THORP's Feed Clarification Cell on 19 April 2005. All the fluids collected under gravity into the secondary containment
, which is a stainless steel tub embedded in 2 metre thick reinforced concrete
, capable of holding 250 cubic metres of fluids.
The solution from the spill was estimated to contain 20 metric tons of uranium and 160 kilograms of plutonium. The leaked solution was safely recovered into primary containment using originally installed steam ejectors. Radiation levels in the cell preclude entry of humans and robotic repair of the fractured pipe is expected to be difficult. Officials are considering bypassing the faulty tank to resume operations.
The pipe fractured due to lateral motion of an accountancy tank, which measures volume by weight and moves horizontally and vertically in the process. The tank's original design had restraint blocks to prevent lateral motion, but these were later removed from the design for seismic uncoupling. However it appears this design change was not evaluated for fatigue, and it is inconceivable a proper review would have permitted this change.
The incident was classified as Level 3 out of 7 on the International Nuclear Event Scale
(INES), a "serious incident", due to the amount of radioactive inventory that leaked from primary to secondary containment without discovery over a number of months. This was initially considered by BNFL to be surprisingly high, but the specifications of the scale required it.
No radiation leaked to the environment and no one was injured.
Return to service will be dependent on appropriate modification proposals and any further regulatory requirements resulting from the ongoing investigations. As of March 2006 various restart and closure options were still being considered.
The British Nuclear Group was convicted for breaches of health and safety regulations following the accident, and fined £
500,000.
Production eventually restarted at the plant in early 2008 but almost immediately had to be put on hold again, for the repair of an underwater lift that moves fuel for reprocessing.
Other reprocessing sites
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
plant at Sellafield
Sellafield
Sellafield is a nuclear reprocessing site, close to the village of Seascale on the coast of the Irish Sea in Cumbria, England. The site is served by Sellafield railway station. Sellafield is an off-shoot from the original nuclear reactor site at Windscale which is currently undergoing...
in Cumbria
Cumbria
Cumbria , is a non-metropolitan county in North West England. The county and Cumbria County Council, its local authority, came into existence in 1974 after the passage of the Local Government Act 1972. Cumbria's largest settlement and county town is Carlisle. It consists of six districts, and in...
, England. THORP is owned by the Nuclear Decommissioning Authority
Nuclear Decommissioning Authority
The Nuclear Decommissioning Authority is a non-departmental public body of the United Kingdom formed by the Energy Act 2004. It came into existence in late 2004, and took on its main functions on 1 April 2005...
and operated by Sellafield Ltd (which is the site licensee company). Spent nuclear fuel from nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s is reprocessed to separate the 96% uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
and the 1% plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
, which can be reused in mixed oxide fuel, from the 3% radioactive wastes, which are treated and stored at the plant. The uranium is then made available for customers to be manufactured into new fuel.
History
Construction of THORP started in the 1970s, and was completed in 1994. The plant went into operation in August 1997.Between 1977 and 1978 an inquiry was held into an application by British Nuclear Fuels plc
BNFL
British Nuclear Fuels Limited was a nuclear energy and fuels company owned by the UK Government. It was a former manufacturer and transporter of nuclear fuel , ran reactors, generated and sold electricity, reprocessed and managed spent fuel , and decommissioned nuclear plants and other similar...
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, was given the go-ahead in 1978, although it was not completed until the 1990s.
Design features
The chemical flowsheet for THORP is designed to add less involatile matter to the first cycle PUREXPUREX
PUREX is an acronym standing for Plutonium - URanium EXtraction — de facto standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel. It is based on liquid-liquid extraction ion-exchange.The PUREX process was invented by Herbert H. Anderson and...
raffinate
Raffinate
Raffinating something is a technique used in metallurgy to remove impurities from liquid material. There are many different kinds of raffination, for example you can use vacuum to extract hydrogen from metals....
, one way in which this is done is by avoiding the use of ferrous compounds as plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
reducing agents. In this plant the reduction is done using either hydrazine
Hydrazine
Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...
or HAN (hydroxylamine
Hydroxylamine
Hydroxylamine is an inorganic compound with the formula NH2OH. The pure material is a white, unstable crystalline, hygroscopic compound. However, hydroxylamine is almost always provided and used as an aqueous solution. It is used to prepare oximes, an important functional group. It is also an...
nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...
).
2005 leak
On 9 May 2005 it was announced that THORP suffered a large leak of a highly radioactive solution, which first started in July 2004. British Nuclear Group's board of inquiry determined that a design error led to the leak, while a complacent culture at the plant delayed detection for nine months. Operations staff did not discover the leak until safeguards staff reported major fluid accountancy discrepancies.Altogether 83 cubic metre
Cubic metre
The cubic metre is the SI derived unit of volume. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère...
s (18,250 imperial gallons) of nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
solution leaked from a small fractured feedpipe, which was discovered when a remote camera was sent in to examine THORP's Feed Clarification Cell on 19 April 2005. All the fluids collected under gravity into the secondary containment
Secondary containment
Can refer to*Containment building - A type of building used with nuclear reactors*Secondary spill containment - a technique for dealing with hazardous spills*A possible requirement for Chemical tanks...
, which is a stainless steel tub embedded in 2 metre thick reinforced concrete
Reinforced concrete
Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...
, capable of holding 250 cubic metres of fluids.
The solution from the spill was estimated to contain 20 metric tons of uranium and 160 kilograms of plutonium. The leaked solution was safely recovered into primary containment using originally installed steam ejectors. Radiation levels in the cell preclude entry of humans and robotic repair of the fractured pipe is expected to be difficult. Officials are considering bypassing the faulty tank to resume operations.
The pipe fractured due to lateral motion of an accountancy tank, which measures volume by weight and moves horizontally and vertically in the process. The tank's original design had restraint blocks to prevent lateral motion, but these were later removed from the design for seismic uncoupling. However it appears this design change was not evaluated for fatigue, and it is inconceivable a proper review would have permitted this change.
The incident was classified as Level 3 out of 7 on the International Nuclear Event Scale
International Nuclear Event Scale
The International Nuclear and Radiological Event Scale was introduced in 1990 by the International Atomic Energy Agency in order to enable prompt communication of safety significance information in case of nuclear accidents....
(INES), a "serious incident", due to the amount of radioactive inventory that leaked from primary to secondary containment without discovery over a number of months. This was initially considered by BNFL to be surprisingly high, but the specifications of the scale required it.
No radiation leaked to the environment and no one was injured.
Return to service will be dependent on appropriate modification proposals and any further regulatory requirements resulting from the ongoing investigations. As of March 2006 various restart and closure options were still being considered.
The British Nuclear Group was convicted for breaches of health and safety regulations following the accident, and fined £
Pound sterling
The pound sterling , commonly called the pound, is the official currency of the United Kingdom, its Crown Dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands, British Antarctic Territory and Tristan da Cunha. It is subdivided into 100 pence...
500,000.
Production eventually restarted at the plant in early 2008 but almost immediately had to be put on hold again, for the repair of an underwater lift that moves fuel for reprocessing.
See also
- Nuclear fuel cycleNuclear fuel cycleThe nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end, which are the preparation of the fuel, steps in the service period in which the fuel is used during reactor operation, and steps in...
- Reprocessed uraniumReprocessed uraniumReprocessed uranium is the uranium recovered from nuclear reprocessing, as done commercially in France, the UK and Japan and by nuclear weapons states' military plutonium production programs. This uranium actually makes up the bulk of the material separated during reprocessing...
- Red oilRed oilRed oil is defined as a substance of varying composition formed when an organic solution, typically tri-n-butyl phosphate and its diluent, comes in contact with concentrated nitric acid at a temperature above 120 °C.Red oil is relatively stable below 130 °C, but it can decompose explosively when its...
- PUREXPUREXPUREX is an acronym standing for Plutonium - URanium EXtraction — de facto standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel. It is based on liquid-liquid extraction ion-exchange.The PUREX process was invented by Herbert H. Anderson and...
- Pyrometalurgical Processing
Other reprocessing sites
- COGEMA La Hague siteCOGEMA La Hague siteThe AREVA NC La Hague site is a nuclear fuel reprocessing plant of AREVA in La Hague on the French Cotentin Peninsula that currently has nearly half of the world's light water reactor spent nuclear fuel reprocessing capacity. It has been in operation since 1976, and has a capacity of about 1700...
- Rokkasho Reprocessing PlantRokkasho Reprocessing PlantThe is a nuclear reprocessing plant with an annual capacity of 800 tons of uranium or 8 tons of plutonium, owned by Japan Nuclear Fuel Limited located in the village of Rokkasho in northeast Aomori Prefecture, Japan approximately 17 miles north of the US Air Force's Misawa Air Base...
- West Valley Reprocessing PlantWest Valley Reprocessing PlantWest Valley Reprocessing Plant was a formerly operational plant for the reprocessing of used nuclear fuel at West Valley, New York, USA. It was operated from 1966-72. During this time period, 600,000 gallons of highly radioactive waste accumulated in an underground waste tank...
- MayakMayakMayak Production Association refers to an industrial complex that is one of the biggest nuclear facilities in the Russian Federation. It housed plutonium production reactors and a reprocessing plant...
- Tōkai, IbarakiTokai, Ibarakiis a village located in Naka District, Ibaraki, Japan. It is approximately 120 km north of Tokyo, Japan on the Pacific coast.As of 1 January 2005, the village has an estimated population of 35,467 and a population density of 946.29 persons per km²...
(Tokaimura nuclear accidentTokaimura nuclear accidentThe Tokaimura nuclear accident , which occurred on 30 September 1999, resulted in two deaths. At that time, it was Japan's worst civilian nuclear radiation accident. The criticality accident occurred in a uranium reprocessing facility operated by JCO , a subsidiary of Sumitomo Metal Mining Co...
)
External links
- Nuclear Decommissioning Authority
- Sellafield Limited
- Bellona Foundation - Excellent Site for Detailed Info on Sellafield and associated environmental issues.
- Nuclear unit closed after checks - BBCBBCThe British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
, 23 April 2005 - Huge radioactive leak closes Thorp nuclear plant - The GuardianThe GuardianThe Guardian, formerly known as The Manchester Guardian , is a British national daily newspaper in the Berliner format...
, 9 May 2005 - THORP Fractured Pipe – Board of Inquiry Report, BNFLBNFLBritish Nuclear Fuels Limited was a nuclear energy and fuels company owned by the UK Government. It was a former manufacturer and transporter of nuclear fuel , ran reactors, generated and sold electricity, reprocessed and managed spent fuel , and decommissioned nuclear plants and other similar...
, 26 May 2005 - Thorp officials work to restore UK nuke reprocessing facility - Bellona FoundationBellona FoundationThe Bellona Foundation is a multi-disciplinary international environmental NGO based in Oslo, Norway. Founded in 1986 by Frederic Hauge and Rune Haaland as a direct action protest group, it has since blossomed into a recognized technology and solution-oriented environmental champion with offices on...
, 7 July 2005 - Thorp board of enquiry report released - Nuclear Engineering International, 27 July 2005
- Nuclear staff suspended over leak - BBCBBCThe British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
, 4 August 2005 - Workload forces delay over Thorp reopening - News & Star, 11 November 2005
- Leak of Radioactive Liquor in the Feed Clarification Cell at BNG THORP Sellafield, Review of the Management and Technical Aspects of the Failure and its Implications for the Future of THORP, John LargeJohn LargeJohn H. Large is an independent nuclear engineer and analyst primarily known for his work in assessing and reporting upon nuclear safety and nuclear related accidents and incidents...
, 13 April 2006 - includes diagrams - Thorp restart approved - Nuclear Engineering International, 17 January 2007
- Culture clubbed - Nuclear Engineering International, 25 April 2007
- HSE report into the THORP leak
- The sentencing of British Nuclear Group over the accident at THORP, Mr Justice Openshaw, 16 October 2006