Plutonium and uranium extraction from nuclear fuel-eng

PUREX (plutonium uranium reduction extraction) is a

chemical A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combin ...

method used to purify fuel for

nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...

s or

nuclear weapons A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either nuclear fission, fission (fission or atomic bomb) or a combination of fission and nuclear fusion, fusion reactions (thermonuclear weap ...

. It is based on

liquid–liquid extraction Liquid–liquid extraction, also known as solvent extraction and partitioning, is a method to separate compounds or metal complexes, based on their relative solubility, solubilities in two different Miscibility, immiscible liquids, usually wate ...

ion-exchange Ion exchange is a reversible interchange of one species of ion present in an insoluble solid with another of like charge present in a solution surrounding the solid. Ion exchange is used in softening or demineralizing of water, purification of ch ...

. PUREX is the '' de facto'' standard aqueous

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 ...

method for the recovery of

uranium Uranium is a chemical element; it has chemical symbol, 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. Ura ...

and

plutonium Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four ...

from used

nuclear fuel Nuclear fuel refers to any substance, typically fissile material, which is used by nuclear power stations or other atomic nucleus, nuclear devices to generate energy. Oxide fuel For fission reactors, the fuel (typically based on uranium) is ...

(

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 and ...

, or

irradiated Irradiation is the process by which an object is exposed to radiation. An irradiator is a device used to expose an object to radiation, most often gamma radiation, for a variety of purposes. Irradiators may be used for sterilizing medical and p ...

nuclear fuel). It is also the standard process used in industrial scale operations. PUREX is applied to

, which consists primarily of very high atomic-weight (

actinoid The actinide () or actinoid () series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium. Number 103, lawrencium, is also generally included despite being part ...

or "actinide") elements (e.g.

americium Americium is a synthetic element, synthetic chemical element; it has Chemical symbol, symbol Am and atomic number 95. It is radioactive and a transuranic member of the actinide series in the periodic table, located under the lanthanide element e ...

) 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 releas ...

produced by reactor operation. Uranium Reprocessing

The actinoid elements in this case consist primarily of the unconsumed remains of the original fuel (typically

U-235 Uranium-235 ( or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists in nat ...

, U-238, and/or

Pu-239 Plutonium-239 ( 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 iso ...

Chemical process

The fuel is first dissolved in

nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...

at a concentration around 7 M. Solids are removed by filtration to avoid the formation of

emulsion An emulsion is a mixture of two or more liquids that are normally Miscibility, immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloi ...

s, 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 (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 p ...

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 a ...

(TBP) in a

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

such as

kerosene Kerosene, or paraffin, is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from the Greek (''kērós'') meaning " ...

. Uranyl(VI) ions are extracted in the organic phase as UO₂(NO₃)₂·2TBP complexes; plutonium is extracted as similar complexes. The heavier actinides, primarily

and

curium Curium is a synthetic chemical element; it has symbol Cm and atomic number 96. This transuranic actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first inten ...

, 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 Hydroxylamine (also known as hydroxyammonia) is an inorganic compound with the chemical formula . The compound exists as hygroscopic colorless crystals.Greenwood and Earnshaw. ''Chemistry of the Elements.'' 2nd Edition. Reed Educational and Prof ...

ferrous In chemistry, iron(II) refers to the chemical element, element iron in its +2 oxidation number, oxidation state. The adjective ''ferrous'' or the prefix ''ferro-'' is often used to specify such compounds, as in ''ferrous chloride'' for iron(II ...

sulphamate, and

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydraz ...

. 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 e ...

'' describes the mixture of metals in

which are left behind when the

and

have been removed by the PUREX process from a

dissolution liquor. This mixture is often known as high level

nuclear waste Radioactive waste is a type of hazardous waste that contains radioactive material. It is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, nuclear decommissioning, rare-earth mining, and nuclear ...

. Two PUREX raffinates exist. The most highly active

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 ...

with

. Deep blue is the bulk ions, light blue is the

(group I is Rb/Cs; group II is Sr/Ba; group III is Y and the

lanthanides The lanthanide () or lanthanoid () series of chemical elements comprises at least the 14 Metal, metallic chemical elements with atomic numbers 57–70, from lanthanum through ytterbium. In the periodic table, they fill the 4f orbitals. Lutetium ...

), 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 Minor may refer to: Common meanings * Minor (law), a person not under the age of certain legal activities. * Academic minor, a secondary field of study in undergraduate education Mathematics * Minor (graph theory), a relation of one graph to an ...

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 ef ...

) Currently PUREX raffinate is stored in

stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...

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 conside ...

. It has almost all of the

products such as

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

, traces of uranium, plutonium and the

Pollution

Waste from the commercial PUREX process include acidic aqueous raffinate with high levels of radioactive materials (HLLW) as well as high volumes of lower-level waste streams and degraded organic solvents. 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. It has also been known as SiteW and the Hanford Nuclear R ...

was responsible for producing 'copious volumes of liquid wastes', resulting in the radioactive contamination of groundwater.

Greenpeace Greenpeace is an independent global campaigning network, founded in Canada in 1971 by a group of Environmental movement, environmental activists. Greenpeace states its goal is to "ensure the ability of the Earth to nurture life in all its biod ...

measurements in

La Hague La Hague () is a commune in the department of Manche, northwestern France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Gui ...

and

Sellafield Sellafield, formerly known as Windscale, 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 storage, nuclear waste processing and storage and nucle ...

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. According to

, this additional radiation is small but not negligible.

History

The PUREX process was invented by Herbert H. Anderson and

Larned B. Asprey Larned (Larry) Brown Asprey (March 19, 1919 – March 6, 2005) was an American chemist noted for his work on actinide, lanthanide, rare-earth, and fluorine chemistry, and for his contributions to nuclear chemistry on the Manhattan Project and lat ...

at the

Metallurgical Laboratory The Metallurgical Laboratory (or Met Lab) was a scientific laboratory from 1942 to 1946 at the University of Chicago. It was established in February 1942 and became the Argonne National Laboratory in July 1946. The laboratory was established i ...

at the

University of Chicago The University of Chicago (UChicago, Chicago, or UChi) is a Private university, private research university in Chicago, Illinois, United States. Its main campus is in the Hyde Park, Chicago, Hyde Park neighborhood on Chicago's South Side, Chic ...

, as part of the

Manhattan Project The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada. From 1942 to 1946, the ...

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 i ...

; their patent "Solvent Extraction Process for Plutonium" filed in 1947, mentions

as the major reactant which accomplishes the bulk of the chemical extraction.

List of nuclear reprocessing sites

La Hague site The La Hague site is a nuclear reprocessing, 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 Cycle, Orano, formerly Areva, AREVA, and prior ...

Mayak The Mayak Production Association (, , from 'lighthouse') is one of the largest nuclear facilities in the Russian Federation, housing Production reactor, production reactors (''non'' electricity) and a reprocessing plant. The closest settlement ...

Magnox Reprocessing Plant 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 ...

and

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, the site licensee. Spent nuclear f ...

, both ended operation * Tokai, Ibaraki * West Valley Reprocessing Plant *

Savannah River Site The Savannah River Site (SRS), formerly the Savannah River Plant, is a U.S. Department of Energy (DOE) reservation in the United States, located in the state of South Carolina on land in Aiken, Allendale and Barnwell counties adjacent to the ...

* 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. Historically, the lab has been involved with nuclear research, although the labora ...

* Radiochemical Engineering Development Center,

Oak Ridge National Laboratory Oak Ridge National Laboratory (ORNL) is a federally funded research and development centers, federally funded research and development center in Oak Ridge, Tennessee, United States. Founded in 1943, the laboratory is sponsored by the United Sta ...

References and notes

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 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 ...

Plutonium Uranium