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 from used
nuclear fuel (
spent 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 ...
, or
irradiated
Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serv ...
nuclear fuel). It is based on
liquid–liquid extraction
Liquid–liquid extraction (LLE), also known as solvent extraction and partitioning, is a method to separate compounds or metal complexes, based on their relative solubilities in two different immiscible liquids, usually water (polar) and an orga ...
ion-exchange
Ion exchange is a reversible interchange of one kind of ion present in an insoluble solid with another of like charge present in a solution surrounding the solid with the reaction being used especially for softening or making water demineralised, ...
.
PUREX is applied to
spent 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 ...
, which consists primarily of very high
atomic-weight (
actinoid
The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The inform ...
or "actinide")
elements (e.g.
uranium,
plutonium,
americium
Americium is a synthetic radioactive chemical element with the symbol Am and atomic number 95. It is a transuranic member of the actinide series, in the periodic table located under the lanthanide element europium, and thus by analogy was named ...
) along with smaller amounts of material composed of lighter atoms, notably the
fission products
Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...
produced by reactor operation.
The actinoid elements in this case consist primarily of the unconsumed remains of the original fuel (typically
U-235,
U-238, and/or
Pu-239
Plutonium-239 (239Pu or Pu-239) is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 is also used for that purpose. Plutonium-239 is also one of the three main ...
).
Chemical process
The fuel is first dissolved in
nitric acid at a concentration around 7
M. Solids are removed by filtration to avoid the formation of
emulsions, referred to as
third phase
Third phase is the term for a stable emulsion which forms in a liquid–liquid extraction when the original two phases (aqueous and organic) are mixed.
The third phase can be caused by a detergent ( surfactant) or a fine solid. While third phase ...
s in the solvent extraction community.
The
organic solvent
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
consists of 30%
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) in a
hydrocarbon such as
kerosene. Uranyl(VI) ions are extracted in the organic phase as UO
2(NO
3)
2·2TBP complexes; plutonium is extracted as similar
complexes. The heavier actinides, primarily
americium
Americium is a synthetic radioactive chemical element with the symbol Am and atomic number 95. It is a transuranic member of the actinide series, in the periodic table located under the lanthanide element europium, and thus by analogy was named ...
and
curium
Curium is a transuranic, radioactive chemical element with the symbol Cm and atomic number 96. This actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first inte ...
, and the fission products remain in the aqueous phase. The nature of uranyl nitrate complexes with trialkyl phosphates has been characterized.
Plutonium is separated from uranium by treating the TBP-kerosene solution with reducing agents to convert the plutonium to its +3 oxidation state, which will pass into the aqueous phase. Typical reducing agents include N,N-diethyl-
hydroxylamine,
ferrous
In chemistry, the adjective Ferrous indicates a compound that contains iron(II), meaning iron in its +2 oxidation state, possibly as the divalent cation Fe2+. It is opposed to "ferric" or iron(III), meaning iron in its +3 oxidation state, such a ...
sulphamate, and
hydrazine. Uranium is then stripped from the kerosene solution by back-extraction into nitric acid at a concentration around 0.2 M.
PUREX raffinate
The term ''PUREX
raffinate In chemical separation terminology, the raffinate (from French ''raffiner'', to refine) is a product which has had a component or components removed. The product having the removed materials is referred to as the extract. For example, in solvent ext ...
'' describes the mixture of metals in
nitric acid which are left behind when the
uranium and
plutonium have been removed by the PUREX process from a
nuclear fuel dissolution liquor. This mixture is often known as high level
nuclear waste.
Two PUREX raffinates exist. The most highly active
raffinate In chemical separation terminology, the raffinate (from French ''raffiner'', to refine) is a product which has had a component or components removed. The product having the removed materials is referred to as the extract. For example, in solvent ext ...
from the first cycle is the one which is most commonly known as PUREX raffinate. The other is from the medium-active cycle in which the uranium and plutonium are refined by a second
extraction Extraction may refer to:
Science and technology
Biology and medicine
* Comedo extraction, a method of acne treatment
* Dental extraction, the surgical removal of a tooth from the mouth
Computing and information science
* Data extraction, the pr ...
with
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 ...
.
Deep blue is the bulk ions, light blue is the
fission products
Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...
(group I is Rb/Cs) (group II is Sr/Ba) (group III is Y and the
lanthanides), orange is the
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
products (from stainless steel pipework), green are the major actinides, violet are the
minor actinides and magenta is the
neutron poison
In applications such as nuclear reactors, a neutron poison (also called a neutron absorber or a nuclear poison) is a substance with a large neutron absorption cross-section. In such applications, absorbing neutrons is normally an undesirable eff ...
)
Currently PUREX raffinate is stored in
stainless steel tanks before being
converted into glass. The first cycle PUREX raffinate is very
radioactive
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
. It has almost all of the
fission products
Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...
,
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
products such as
iron/
nickel, traces of uranium, plutonium and the
minor actinides.
Pollution
The PUREX plant at the
Hanford Site
The Hanford Site is a decommissioned nuclear production complex operated by the United States federal government on the Columbia River in Benton County in the U.S. state of Washington. The site has been known by many names, including SiteW ...
was responsible for producing 'copious volumes of liquid wastes', resulting in the radioactive contamination of groundwater.
Greenpeace measurements in
La Hague and
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 nu ...
indicated that radioactive pollutants are steadily released into the sea, and the air. Therefore, people living near these processing plants are exposed to higher radiation levels than the naturally occurring
background radiation
Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources.
Background radiation originates from a variety of source ...
. According to
Greenpeace, this additional radiation is small but not negligible.
History
The PUREX process was invented by
Herbert H. Anderson and
Larned B. Asprey at the
Metallurgical Laboratory at the
University of Chicago, as part of the
Manhattan Project under
Glenn T. Seaborg
Glenn Theodore Seaborg (; April 19, 1912February 25, 1999) was an American chemist whose involvement in the synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Chemistry. His work in ...
; their patent "Solvent Extraction Process for Plutonium" filed in 1947, mentions
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 ...
as the major reactant which accomplishes the bulk of the chemical extraction.
List of nuclear reprocessing sites
*
COGEMA La Hague site
The La Hague site is a nuclear fuel reprocessing plant at La Hague on the Cotentin Peninsula in northern France, with the Manche storage centre bordering on it. Operated by Orano, formerly AREVA, and prior to that COGEMA (''Compagnie générale ...
*
Mayak
The Mayak Production Association (russian: Производственное объединение «Маяк», , from 'lighthouse') is one of the biggest nuclear facilities in the Russian Federation, housing a reprocessing plant. The closest ...
*
Thermal Oxide Reprocessing Plant
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 ...
and
B205
The Magnox Reprocessing Plant is a former nuclear reprocessing facility at Sellafield in northern England, which operated from 1964 to 2022. The plant used PUREX chemistry (based on tributyl phosphate (TBP)) to extract plutonium and uranium from ...
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 nu ...
*
Tokai, Ibaraki
*
West Valley Reprocessing Plant
The West Valley Demonstration Project is a nuclear waste remediation site in West Valley, New York in the U.S. state of New York. The project focuses on the cleanup and containment of radioactive waste left behind after the abandonment of a comm ...
*
Savannah River Site
*
Hanford Site
The Hanford Site is a decommissioned nuclear production complex operated by the United States federal government on the Columbia River in Benton County in the U.S. state of Washington. The site has been known by many names, including SiteW ...
* Idaho Chemical Processing Plant, (now
Idaho National Laboratory
Idaho National Laboratory (INL) is one of the national laboratories of the United States Department of Energy and is managed by the Battelle Energy Alliance. While the laboratory does other research, historically it has been involved with nu ...
)
* Radiochemical Engineering Development Center,
Oak Ridge National Laboratory
See also
*
Nuclear fuel cycle
The 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 w ...
*
Nuclear breeder reactor
*
Spent nuclear fuel shipping cask
A nuclear flask is a shipping container that is used to transport active nuclear materials between nuclear power station and spent fuel reprocessing facilities.
Each shipping container is designed to maintain its integrity under normal transport ...
*
Global Nuclear Energy Partnership
The International Framework for Nuclear Energy Cooperation (IFNEC) formerly the Global Nuclear Energy Partnership (GNEP) began as a U.S. proposal, announced by United States Secretary of Energy Samuel Bodman on February 6, 2006, to form an interna ...
announced February, 2006
References & notes
Further reading
* OECD Nuclear Energy Agency, The Economics of the Nuclear Fuel Cycle, Paris, 1994
* I. Hensing and W Schultz, Economic Comparison of Nuclear Fuel Cycle Options, Energiewirtschaftlichen Instituts, Cologne, 1995.
* Cogema, Reprocessing-Recycling: the Industrial Stakes, presentation to the Konrad-Adenauer-Stiftung, Bonn, 9 May 1995.
* OECD Nuclear Energy Agency, Plutonium Fuel: An Assessment, Paris, 1989.
* National Research Council, "Nuclear Wastes: Technologies for Separation and Transmutation", National Academy Press, Washington D.C. 1996.
External links
Processing of Used Nuclear Fuel, World Nuclear Association
Analytical Center for Non-proliferation
{{Webarchive, url=https://web.archive.org/web/20130301173649/http://www.world-nuclear.org/info/inf29.html , date=2013-03-01 – World Nuclear Association
– Congressional Research Service Report for Congress
Radioactive waste
Waste treatment technology
Nuclear chemistry
Nuclear reprocessing
Plutonium
Uranium