The
Magnox
Magnox is a type of nuclear power/production reactor that was designed to run on natural uranium with graphite as the moderator and carbon dioxide gas as the heat exchange coolant. It belongs to the wider class of gas-cooled reactors. The n ...
Reprocessing Plant is a former
nuclear reprocessing
Nuclear reprocessing is the chemical separation of fission products and actinides from spent nuclear fuel. Originally, reprocessing was used solely to extract plutonium for producing nuclear weapons. With commercialization of nuclear power, the ...
facility at
Sellafield
Sellafield is a large multi-function nuclear site close to Seascale on the coast of Cumbria, England. As of August 2022, primary activities are nuclear waste processing and storage and nuclear decommissioning. Former activities included nucle ...
in northern England, which operated from 1964 to 2022. The plant used
PUREX
PUREX (plutonium uranium reduction extraction) is a chemical method used to purify fuel for nuclear reactors or nuclear weapons. PUREX is the ''de facto'' standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium fr ...
chemistry (based on
tributyl phosphate
Tributyl phosphate, known commonly as TBP, is an organophosphorus compound with the chemical formula (CH3CH2CH2CH2O)3PO. This colourless, odorless liquid finds some applications as an extractant and a plasticizer. It is an ester of phosphoric ac ...
(TBP)) to extract
plutonium
Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...
and
uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
from
used nuclear fuel
Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor (usually at a nuclear power plant). It is no longer useful in sustaining a nuclear reaction in an ordinary thermal reactor an ...
originating primarily from Magnox reactors. The plant was originally constructed and operated by the
United Kingdom Atomic Energy Authority
The United Kingdom Atomic Energy Authority is a UK government research organisation responsible for the development of fusion energy. It is an executive non-departmental public body of the Department for Business, Energy and Industrial Strategy ...
(UKAEA), but in 1971 control was transferred to
British Nuclear Fuels Limited
British Nuclear Fuels Limited (BNFL) was a nuclear energy and fuels company owned by the UK Government. It was a manufacturer of nuclear fuel (notably MOX), ran reactors, generated and sold electricity, reprocessed and managed spent fuel (main ...
(BNFL). Since 2005 the plant has been operated by Sellafield Ltd.
Operation
The plant was commissioned in 1964 as both a replacement for the UK's First Generation Reprocessing Plant, and to process spent fuel from the national fleet of Magnox reactors. The First generation Plant was then converted into a pre-handling plant for Magnox reprocessing and was recommissioned in 1969. In 1973, after both plants had been shut down for one year for maintenance, a violent reaction called a "blowback" occurred in the First Generation Plant which contaminated that plant and 34 workers with
ruthenium
Ruthenium is a chemical element with the Symbol (chemistry), symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to ...
-106. Following this event the First Generation Plant was permanently closed.
Over its lifetime, the Magnox plant handled over 55,000 tons of spent fuel from the UK's fleet of 11 Magnox plants as well as reprocessing Magnox fuel from Italy, Japan, and fast breeder fuel from
Dounreay
Dounreay (; gd, Dùnrath) is a small settlement and the site of two large nuclear establishments on the north coast of Caithness in the Highland area of Scotland. It is on the A836 road west of Thurso.
The nuclear establishments were create ...
. In total, the plant has returned over 15,000 tons of uranium back into the fuel cycle. As of 2019, all Magnox reactors have now been retired from operation and defueled, with the last load of burnt-up Magnox fuel arrived at Sellafield in 2019.
B205 ceased operations on 17 July 2022, when it was announced that it had worked through the remaining spent Magnox fuel stockpiles. Thus completing its mission which spanned nearly 6 decades.
Process
The process used mixer settlers as the basis of the plant operation. The unit comprised a set of mixing compartments where the solvent and aqueous liquids mixed. The mix then passed to an associated settler compartment where the solvent separated from the aqueous and forms two separate layers. These then left the settler compartment to the next mixer compartments. The solvent and aqueous flowed in opposite directions through the mixer settler stages (typically 8 or more), controlled by careful design of the transfer ports between the settler stages.
The task to extract usable uranium and plutonium began with a process known as "decanning" where the
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
fuel can was separated from the inner uranium rod. The uranium rod was then sheared and dropped into a hot nitric acid solution within the Dissolver Cell. The aqueous stream was conditioned to the correct temperature and acidity and then passed to the first mixer settler system where fission products were separated from the uranium (U) and plutonium (Pu) by extraction of the U/Pu into the solvent phase comprising tri-butyl-phosphate in odourless kerosene. This had the effect of reducing the radiation levels in subsequent stages of the process and the resulting degradation of the solvents.
The solvent stream of U, Pu and remaining fission products passed to the critical mixer settler stages where the U and Pu were transferred into the aqueous phase, and fission products remained in the aqueous phase. Separation of the U and Pu was achieved by adding a reductant, which caused the Pu, but not the U, to transfer into the aqueous phase. Once separated, further removal of fission products was undertaken by more mixer settler units. The U and Pu streams were then passed to evaporators to concentrate the U and Pu before further processing in other plants.
The plant contributed the majority of liquid discharges from the
Sellafield
Sellafield is a large multi-function nuclear site close to Seascale on the coast of Cumbria, England. As of August 2022, primary activities are nuclear waste processing and storage and nuclear decommissioning. Former activities included nucle ...
site; around 132 Terabecquerels (TBq) annually.
Operation
50 Not Out
In 2014 Sellafield Ltd celebrated 50 years of Magnox Reprocessing from 1964 to 2014. Called "50 not out" to highlight that the plant was not shutting down, the events related to this celebration spoke about the history of Magnox and Reprocessing as well as design choices that led to the use of magnesium cladding and overall information about the Magnox Operating Programme.
2020 Controlled Shutdown
In 2020 due to coronavirus, Sellafield Ltd announced that the Magnox reprocessing plant will undergo a controlled shutdown to ensure less maintenance when it is eventually restarted. Whereas turning the facility off quickly in a response to reduced staff members on-site has a possibility to result in unnecessary maintenance or repair work. This will cause the closure date of the facility to be pushed back as no fuel will be reprocessed in this time.
Completion of Reprocessing
Magnox fuel reprocessing ceased on 17 July 2022, when the reprocessing plant completed its last batch of fuel after 58 years of operation. A total of 55,000 tonnes of fuel had been processed during those years.
See also
*
Reprocessed uranium
Reprocessed uranium (RepU) 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 makes up the bulk of the material s ...
*
Mixer-settler
Mixer settlers are a class of mineral process equipment used in the solvent extraction process. A mixer settler consists of a first stage that ''mixes'' the phases together followed by a quiescent ''settling'' stage that allows the phases to sep ...
References
{{reflist
Nuclear reprocessing sites
Nuclear technology in the United Kingdom