Nuclear reprocessing is the chemical separation of
fission products and
actinide
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 info ...
s from
spent nuclear fuel. Originally, reprocessing was used solely to extract plutonium for producing
nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bomb ...
s. With commercialization of
nuclear power
Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced b ...
, the reprocessed plutonium was recycled back into
MOX nuclear fuel for
thermal reactor
A thermal-neutron reactor is a nuclear reactor that uses slow or thermal neutrons. ("Thermal" does not mean hot in an absolute sense, but means in thermal equilibrium with the medium it is interacting with, the reactor's fuel, moderator and struct ...
s. The
reprocessed uranium, also known as the spent fuel material, can in principle also be re-used as fuel, but that is only economical when uranium supply is low and prices are high. A
breeder reactor is not restricted to using recycled plutonium and uranium. It can employ all the
actinide
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 info ...
s, closing the
nuclear fuel cycle and potentially multiplying the energy extracted from
natural uranium by about 60 times.
Reprocessing must be highly controlled and carefully executed in advanced facilities by highly specialized personnel. Fuel bundles which arrive at the sites from nuclear power plants (after having cooled down for several years) are completely dissolved in chemical baths, which could pose contamination risks if not properly managed.
Relatively high cost is associated with spent fuel reprocessing compared to the once-through fuel cycle, but fuel use can be increased and
waste
Waste (or wastes) are unwanted or unusable materials. Waste is any substance discarded after primary use, or is worthless, defective and of no use. A by-product, by contrast is a joint product of relatively minor economic value. A waste pr ...
volumes decreased.
Nuclear fuel reprocessing is performed routinely in Europe, Russia, and Japan. In the United States, the Obama administration stepped back from President Bush's plans for commercial-scale reprocessing and reverted to a program focused on reprocessing-related scientific research.
Separated components and disposition
The potentially useful components dealt with in nuclear reprocessing comprise specific
actinide
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 info ...
s (plutonium, uranium, and some
minor actinides). The lighter
elements components include
fission products,
activation products, and
cladding.
History
The first large-scale nuclear reactors were built during
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
. These reactors were designed for the production of plutonium for use in
nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bomb ...
s. The only reprocessing required, therefore, was the extraction of the
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 exh ...
(free of
fission-product contamination) from the spent
natural uranium fuel. In 1943, several methods were proposed for separating the relatively small quantity of plutonium from the uranium and fission products. The first method selected, a precipitation process called the
bismuth phosphate process, was developed and tested at the
Oak Ridge National Laboratory
Oak Ridge National Laboratory (ORNL) is a U.S. multiprogram science and technology national laboratory sponsored by the U.S. Department of Energy (DOE) and administered, managed, and operated by UT–Battelle as a federally funded research an ...
(ORNL) between 1943 and 1945 to produce quantities of plutonium for evaluation and use in the
US weapons programs. ORNL produced the first macroscopic quantities (grams) of separated plutonium with these processes.
The bismuth phosphate process was first operated on a large scale at the
Hanford Site, in the later part of 1944. It was successful for plutonium separation in the emergency situation existing then, but it had a significant weakness: the inability to recover uranium.
The first successful solvent extraction process for the recovery of pure uranium and plutonium was developed at ORNL in 1949. The
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 pluto ...
process is the current method of extraction. Separation plants were also constructed at
Savannah River Site and a smaller plant at
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 ...
which closed by 1972 because of its inability to meet new regulatory requirements.
Reprocessing of civilian fuel has long been employed at the
COGEMA La Hague site in France, the
Sellafield site in the United Kingdom, the
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 ...
Chemical Combine in Russia, and at sites such as the Tokai plant in Japan, the Tarapur plant in India, and briefly at the
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 ...
in the United States.
In October 1976, concern of nuclear weapons proliferation (especially after India demonstrated nuclear weapons capabilities using reprocessing technology) led President
Gerald Ford to issue a
Presidential directive
A presidential directive, or executive action, is a written or oral instruction or declaration issued by the president of the United States, which may draw upon the powers vested in the president by the U.S. Constitution, statutory law, or, in ce ...
to indefinitely suspend the commercial reprocessing and recycling of plutonium in the U.S. On 7 April 1977, President
Jimmy Carter
James Earl Carter Jr. (born October 1, 1924) is an American politician who served as the 39th president of the United States from 1977 to 1981. A member of the Democratic Party (United States), Democratic Party, he previously served as th ...
banned the reprocessing of commercial reactor
spent nuclear fuel. The key issue driving this policy was the risk of
nuclear weapons proliferation
Nuclear proliferation is the spread of nuclear weapons, fissionable material, and weapons-applicable nuclear technology and information to nations not recognized as " Nuclear Weapon States" by the Treaty on the Non-Proliferation of Nuclear Wea ...
by diversion of plutonium from the civilian fuel cycle, and to encourage other nations to follow the US lead. After that, only countries that already had large investments in reprocessing infrastructure continued to reprocess spent nuclear fuel. President Reagan lifted the ban in 1981, but did not provide the substantial subsidy that would have been necessary to start up commercial reprocessing.
In March 1999, the
U.S. Department of Energy (DOE) reversed its policy and signed a contract with a
consortium of
Duke Energy,
COGEMA, and
Stone & Webster
Stone & Webster was an American engineering services company based in Stoughton, Massachusetts. It was founded as an electrical testing lab and consulting firm by electrical engineers Charles A. Stone and Edwin S. Webster in 1889. In the earl ...
(DCS) to design and operate a
mixed oxide (MOX) fuel fabrication facility. Site preparation at the Savannah River Site (South Carolina) began in October 2005. In 2011 the New York Times reported "...11 years after the government awarded a construction contract, the cost of the project has soared to nearly $5 billion. The vast concrete and steel structure is a half-finished hulk, and the government has yet to find a single customer, despite offers of lucrative subsidies." TVA (currently the most likely customer) said in April 2011 that it would delay a decision until it could see how MOX fuel performed in the nuclear accident at
Fukushima Daiichi.
Separation technologies
Water and organic solvents
PUREX
PUREX, the current standard method, is an acronym standing for ''Plutonium and Uranium Recovery by EXtraction''. The PUREX process is a
liquid-liquid extraction method used to reprocess spent
nuclear fuel, to extract
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 ...
and
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 exh ...
, independent of each other, from the
fission products. This is the most developed and widely used process in the industry at present.
When used on fuel from commercial power reactors the plutonium extracted typically contains too much Pu-240 to be considered "weapons-grade" plutonium, ideal for use in a nuclear weapon. Nevertheless, highly reliable nuclear weapons can be built at all levels of technical sophistication using reactor-grade plutonium. Moreover, reactors that are capable of refueling frequently can be used to produce
weapon-grade
Weapons-grade nuclear material is any fissionable nuclear material that is pure enough to make a nuclear weapon or has properties that make it particularly suitable for nuclear weapons use. Plutonium and uranium in grades normally used in nucle ...
plutonium, which can later be recovered using PUREX. Because of this, PUREX chemicals are monitored.
Modifications of PUREX
=UREX
=
The PUREX process can be modified to make a UREX (URanium EXtraction) process which could be used to save space inside high level
nuclear waste disposal sites, such as the
Yucca Mountain nuclear waste repository, by removing the uranium which makes up the vast majority of the mass and volume of used fuel and recycling it as
reprocessed uranium.
The UREX process is a PUREX process which has been modified to prevent the plutonium from being extracted. This can be done by adding a plutonium
reductant before the first metal extraction step. In the UREX process, ~99.9% of the uranium and >95% of
technetium are separated from each other and the other fission products and
actinide
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 info ...
s. The key is the addition of
acetohydroxamic acid
Acetohydroxamic acid (also known as AHA or by the trade name Lithostat) is a drug that is a potent and irreversible enzyme inhibitor of the urease enzyme in various bacteria and plants; it is usually used for urinary tract infections. The molec ...
(AHA) to the extraction and scrub sections of the process. The addition of AHA greatly diminishes the extractability of plutonium and
neptunium, providing somewhat greater proliferation resistance than with the plutonium extraction stage of the PUREX process.
=TRUEX
=
Adding a second extraction agent, octyl(phenyl)-N, N-dibutyl carbamoylmethyl phosphine oxide (CMPO) in combination with tributylphosphate, (TBP), the PUREX process can be turned into the TRUEX (TRansUranic EXtraction) process. TRUEX was invented in the US by
Argonne National Laboratory and is designed to remove the transuranic metals (Am/Cm) from waste. The idea is that by lowering the
alpha activity of the waste, the majority of the waste can then be disposed of with greater ease. In common with PUREX this process operates by a
solvation
Solvation (or dissolution) describes the interaction of a solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of t ...
mechanism.
=DIAMEX
=
As an alternative to TRUEX, an extraction process using a malondiamide has been devised. The DIAMEX (DIAMide EXtraction) process has the advantage of avoiding the formation of organic waste which contains elements other than
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...
,
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...
,
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
, and
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
. Such an organic waste can be burned without the formation of acidic gases which could contribute to
acid rain (although the acidic gases could be recovered by a scrubber). The DIAMEX process is being worked on in Europe by the French
CEA. The process is sufficiently mature that an industrial plant could be constructed with the existing knowledge of the process. In common with PUREX this process operates by a solvation mechanism.
=SANEX
=
Selective ActiNide EXtraction. As part of the management of minor actinides it has been proposed that the
lanthanides and trivalent minor
actinide
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 info ...
s should be removed from the PUREX
raffinate by a process such as DIAMEX or TRUEX. To allow the actinides such as americium to be either reused in industrial sources or used as fuel, the lanthanides must be removed. The lanthanides have large neutron cross sections and hence they would poison a neutron driven nuclear reaction. To date the extraction system for the SANEX process has not been defined, but currently several different research groups are working towards a process. For instance the French
CEA is working on a
bis-triazinyl pyridine
The ''bis''-triazinyl bipyridines (BTBPs) are a class of chemical compounds which are tetradentate ligands similar in shape to quaterpyridine. The BTBPs are made by the reaction of hydrazine and a 1,2-diketone (such as hexane-3,4-dione) with ...
(BTP) based process.
Other systems such as the dithiophosphinic acids are being worked on by some other workers.
=UNEX
=
The ''UNiversal'' EXtraction process was developed in Russia and the
Czech Republic
The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...
; it is designed to completely remove the most troublesome
radioisotopes (Sr, Cs and
minor actinides) from the raffinate remaining after the extraction of uranium and plutonium from used
nuclear fuel. The chemistry is based upon the interaction of
caesium
Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...
and
strontium with
polyethylene glycol and a
cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, p ...
carborane
Carboranes are electron-delocalized (non-classically bonded) clusters composed of boron, carbon and hydrogen atoms.Grimes, R. N., ''Carboranes 3rd Ed.'', Elsevier, Amsterdam and New York (2016), . Like many of the related boron hydrides, these c ...
anion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
(known as chlorinated cobalt dicarbollide). The actinides are extracted by CMPO, and the
diluent is a polar
aromatic
In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...
such as
nitrobenzene. Other diluents such as ''meta''-nitrobenzotri
fluoride and phenyl trifluoromethyl
sulfone have been suggested as well.
Electrochemical and Ion Exchange methods
An exotic method using
electrochemistry
Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an out ...
and
ion exchange in
ammonium carbonate
A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate ...
has been reported.
Other methods for the extraction of uranium using ion exchange in alkaline carbonate and "fumed" lead oxide have also been reported.
Obsolete methods
= Bismuth phosphate
=
The
bismuth phosphate process is an obsolete process that adds significant unnecessary material to the final radioactive waste. The bismuth phosphate process has been replaced by solvent extraction processes. The bismuth phosphate process was designed 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 exh ...
from aluminium-clad
nuclear fuel rod
Nuclear fuel is material used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission.
Most nuclear fuels contain heavy fissile actinide elements that are capable of undergoing ...
s, containing uranium. The fuel was decladded by boiling it in
caustic soda. After decladding, the uranium metal was dissolved in
nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...
.
The plutonium at this point is in the +4 oxidation state. It was then precipitated out of the solution by the addition of
bismuth nitrate
Bismuth(III) nitrate is a salt composed of bismuth in its cationic +3 oxidation state and nitrate anions. The most common solid form is the pentahydrate. It is used in the synthesis of other bismuth compounds. It is available commercially. It is th ...
and
phosphoric acid to form the bismuth phosphate. The plutonium was
coprecipitated
In chemistry, coprecipitation (CPT) or co-precipitation is the carrying down by a precipitate of substances normally soluble under the conditions employed. Analogously, in medicine, coprecipitation is specifically the precipitation of an unbound " ...
with this. The
supernatant liquid (containing many of the
fission products) was separated from the solid. The precipitate was then dissolved in nitric acid before the addition of an
oxidant
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...
(such as
potassium permanganate) to produce PuO
22+. The plutonium was maintained in the +6
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
by addition of a
dichromate salt.
The bismuth phosphate was next re-precipitated, leaving the plutonium in solution, and an iron(II) salt (such as
ferrous sulfate) was added. The plutonium was again re-precipitated using a bismuth phosphate carrier and a combination of
lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between l ...
salts and
fluoride added, forming a solid lanthanum fluoride carrier for the plutonium. Addition of an
alkali produced an oxide. The combined lanthanum plutonium oxide was collected and extracted with nitric acid to form plutonium nitrate.
= Hexone or REDOX
=
This is a liquid-liquid extraction process which uses
methyl isobutyl ketone codenamed hexone as the extractant. The extraction is by a ''solvation'' mechanism. This process has the disadvantage of requiring the use of a
salting-out reagent (
aluminium nitrate
Aluminium nitrate is a white, water-soluble salt of aluminium and nitric acid, most commonly existing as the crystalline hydrate, aluminium nitrate nonahydrate, Al(NO3)3·9H2O.
Preparation
Aluminium nitrate cannot be synthesized by the reac ...
) to increase the nitrate concentration in the aqueous phase to obtain a reasonable distribution ratio (D value). Also, hexone is degraded by concentrated nitric acid. This process was used in 1952-1956 on the
Hanford plant T and has been replaced by the PUREX process.
= Butex, β,β'-dibutyoxydiethyl ether
=
A process based on a solvation extraction process using the triether extractant named above. This process has the disadvantage of requiring the use of a salting-out reagent (aluminium
nitrate) to increase the nitrate concentration in the aqueous phase to obtain a reasonable distribution ratio. This process was used at
Windscale in 1951-1964. This process has been replaced by PUREX, which was shown to be a superior technology for larger scale reprocessing.
= Sodium acetate
=
The sodium uranyl
acetate process was used by the early Soviet nuclear industry to recover plutonium from irradiated fuel. It was a never used in the West; the idea is to dissolve the fuel in
nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...
, alter the oxidation state of the plutonium, and then add
acetic acid and base. This would convert the uranium and plutonium into a solid acetate salt.
Explosion of the crystallized acetates-nitrates in a non-cooled waste tank caused the
Kyshtym disaster in 1957.
Alternatives to PUREX
As there are some downsides to the PUREX process, there have been efforts to develop alternatives to the process, some of them compatible with PUREX (i.e. The residue from one process could be used as feedstock for the other) and others wholly incompatible. None of these have (as of the 2020s) reached widespread commercial use, but some have seen large scale tests or firm commitments towards their future larger scale implementation.
Pyroprocessing
Pyroprocessing
Pyroprocessing (from Greek Πυρος = ''fire'') is a process in which materials are subjected to high temperatures (typically over 800 °C) in order to bring about a chemical or physical change. Pyroprocessing includes such terms as ore-ro ...
is a generic term for high-temperature methods. Solvents are
molten salts (e.g. LiCl + KCl or LiF + CaF
2) and molten metals (e.g. cadmium, bismuth, magnesium) rather than water and organic compounds.
Electrorefining
Electrowinning, also called electroextraction, is the electrodeposition of metals from their ores that have been put in solution via a process commonly referred to as leaching. Electrorefining uses a similar process to remove impurities from a ...
,
distillation
Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the he ...
, and solvent-solvent extraction are common steps.
These processes are not currently in significant use worldwide, but they have been pioneered at
Argonne National Laboratory with current research also taking place at
CRIEPI in Japan, the Nuclear Research Institute of
Řež in Czech Republic,
Indira Gandhi Centre for Atomic Research in India and
KAERI
The Korea Atomic Energy Research Institute (KAERI) in Daejeon, South Korea was established in 1959 as the sole professional research-oriented institute for nuclear power in South Korea, and has rapidly built a reputation for research and developme ...
in South Korea.
Advantages of pyroprocessing
* The principles behind them are well understood, and no significant technical barriers exist to their adoption.
* Readily applied to high-
burnup spent fuel and requires little cooling time, since the
operating temperatures are high already.
* Does not use solvents containing hydrogen and carbon, which are
neutron moderators creating risk of
criticality accidents and can absorb the
fission product tritium and the
activation product
Activation products are materials made radioactive by neutron activation.
Fission products and actinides produced by neutron absorption of nuclear fuel itself are normally referred to by those specific names, and ''activation product'' reserved fo ...
carbon-14 in dilute solutions that cannot be separated later.
**Alternatively, voloxidation
(see
below
Below may refer to:
*Earth
* Ground (disambiguation)
*Soil
*Floor
* Bottom (disambiguation)
*Less than
*Temperatures below freezing
*Hell or underworld
People with the surname
*Ernst von Below (1863–1955), German World War I general
*Fred Below ...
) can remove 99% of the tritium from used fuel and recover it in the form of a strong solution suitable for use as a supply of tritium.
* More compact than aqueous methods, allowing on-site reprocessing at the reactor site, which avoids transportation of spent fuel and its security issues, instead storing a much smaller volume of
fission products on site as
high-level waste until
decommissioning. For example, the
Integral Fast Reactor
The integral fast reactor (IFR, originally advanced liquid-metal reactor) is a design for a nuclear reactor using fast neutrons and no neutron moderator (a "fast" reactor). IFR would breed more fuel and is distinguished by a nuclear fuel cycle ...
and
Molten Salt Reactor fuel cycles are based on on-site pyroprocessing.
* It can separate many or even all
actinide
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 info ...
s at once and produce highly radioactive fuel which is harder to manipulate for theft or making nuclear weapons. (However, the difficulty has been questioned.) In contrast the PUREX process was designed to separate plutonium only for weapons, and it also leaves the
minor actinide
The minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium (element 93), americium (element 95), curium (element 96), berkeliu ...
s (
americium and
curium) behind, producing waste with more long-lived radioactivity.
* Most of the radioactivity in roughly 10
2 to 10
5 years after the use of the nuclear fuel is produced by the actinides, since there are no fission products with half-lives in this range. These actinides can fuel
fast reactors, so extracting and reusing (fissioning) them increases energy production per kg of fuel, as well as reducing the long-term radioactivity of the wastes.
*
Fluoride volatility (see
below
Below may refer to:
*Earth
* Ground (disambiguation)
*Soil
*Floor
* Bottom (disambiguation)
*Less than
*Temperatures below freezing
*Hell or underworld
People with the surname
*Ernst von Below (1863–1955), German World War I general
*Fred Below ...
) produces salts that can readily be used in molten salt reprocessing such as pyroprocessing
* The ability to process "fresh" spent fuel reduces the needs for
spent fuel pools (even if the recovered short lived radionuclides are "only" sent to storage, that still requires less space as the bulk of the mass - Uranium - can be stored separately from them). Uranium - even higher specific activity
reprocessed uranium - does not need cooling for safe storage.
* Short lived radionuclides can be recovered from "fresh" spent fuel allowing either their direct use in industry science or medicine or the recovery of their decay products without contamination by other isotopes (for example: ruthenium in spent fuel decays to rhodium all isotopes of which other than further decay to stable
isotopes of palladium. Palladium derived from the decay of fission ruthenium and rhodium will be nonradioactive, but fission Palladium contains significant contamination with long-lived . Ru-107 and Rh-107 both have half lives in the minutes and will decay to Pd-107 before reprocessing under most circumstances)
* Possible fuels for
radioisotope thermoelectric generator
A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioa ...
s (RTGs) that are mostly decayed in spent fuel, that has significantly aged, can be recovered in sufficient quantities to make their use worthwhile. Examples include materials with half lives around two years such as , , . While those would perhaps not be suitable for lengthy space missions, they can be used to replace
diesel generators in off-grid locations where refueling is possible once a year. Antimony would be particularly interesting because it forms a stable alloy with lead and can thus be transformed relatively easily into a partially self-shielding and chemically inert form. Shorter lived RTG fuels present the further benefit of reducing the risk of
orphan sources as the activity will decline relatively quickly if no refueling is undertaken.
Disadvantages of pyroprocessing
* Reprocessing as a whole is not currently (2005) in favor, and places that do reprocess already have PUREX plants constructed. Consequently, there is little demand for new pyrometallurgical systems, although there could be if the
Generation IV reactor programs become reality.
* The used salt from pyroprocessing is less suitable for conversion into glass than the waste materials produced by the PUREX process.
* If the goal is to reduce the longevity of spent nuclear fuel in burner reactors, then better recovery rates of the minor actinides need to be achieved.
* Working with "fresh" spent fuel requires more shielding and better ways to deal with heat production than working with "aged" spent fuel does. If the facilities are built in such a way as to ''require'' high specific activity material, they cannot handle older "legacy waste" except blended with fresh spent fuel
Electrolysis
The electrolysis methods are based on the difference in the
standard potentials of uranium, plutonium and minor actinides in a molten salt. The standard potential of uranium is the lowest, therefore when a potential is applied, the uranium will be reduced at the cathode out of the molten salt solution before the other elements.
PYRO-A and -B for IFR
These processes were developed by
Argonne National Laboratory and used in the
Integral Fast Reactor
The integral fast reactor (IFR, originally advanced liquid-metal reactor) is a design for a nuclear reactor using fast neutrons and no neutron moderator (a "fast" reactor). IFR would breed more fuel and is distinguished by a nuclear fuel cycle ...
project.
PYRO-A is a means of separating actinides (elements within the
actinide
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 info ...
family, generally heavier than U-235) from non-actinides. The spent fuel is placed in an
anode
An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...
basket which is immersed in a molten salt electrolyte. An electric current is applied, causing the uranium metal (or sometimes oxide, depending on the spent fuel) to plate out on a solid metal cathode while the other actinides (and the rare earths) can be absorbed into a liquid
cadmium
Cadmium is a chemical element with the Symbol (chemistry), symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Li ...
cathode. Many of the fission products (such as
caesium
Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...
,
zirconium and
strontium) remain in the salt. As alternatives to the molten cadmium electrode it is possible to use a molten
bismuth cathode, or a solid aluminium cathode.
As an alternative to electrowinning, the wanted metal can be isolated by using a
molten
Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which ...
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductili ...
of an
electropositive metal and a less reactive metal.
Since the majority of the long term
radioactivity, and volume, of spent fuel comes from actinides, removing the actinides produces waste that is more compact, and not nearly as dangerous over the long term. The radioactivity of this waste will then drop to the level of various naturally occurring minerals and ores within a few hundred, rather than thousands of, years.
The mixed actinides produced by pyrometallic processing can be used again as nuclear fuel, as they are virtually all either
fissile, or
fertile, though many of these materials would require a
fast breeder reactor to be burned efficiently. In a
thermal neutron spectrum, the concentrations of several heavy actinides (
curium-242 and
plutonium-240) can become quite high, creating fuel that is substantially different from the usual uranium or mixed uranium-plutonium oxides (MOX) that most current reactors were designed to use.
Another pyrochemical process, the PYRO-B process, has been developed for the processing and recycling of fuel from a
transmuter reactor ( a
fast breeder reactor designed to convert transuranic nuclear waste into fission products ). A typical transmuter fuel is free from uranium and contains recovered
transuranics in an inert matrix such as metallic
zirconium. In the PYRO-B processing of such fuel, an
electrorefining
Electrowinning, also called electroextraction, is the electrodeposition of metals from their ores that have been put in solution via a process commonly referred to as leaching. Electrorefining uses a similar process to remove impurities from a ...
step is used to separate the residual transuranic elements from the fission products and recycle the transuranics to the reactor for fissioning. Newly generated technetium and iodine are extracted for incorporation into transmutation targets, and the other fission products are sent to waste.
Voloxidation
Voloxidation (for ''volumetric oxidation'') involves heating oxide fuel with oxygen, sometimes with alternating oxidation and reduction, or alternating oxidation by
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the l ...
to
uranium trioxide with decomposition by heating back to
triuranium octoxide.
A major purpose is to capture
tritium as tritiated water vapor before further processing where it would be difficult to retain the tritium. Tritium is a difficult contaminant to remove from aqueous solution, as it cannot be separated from water except by isotope separation. However, tritium is also a valuable product used in industry science and
nuclear weapons, so recovery of a stream of hydrogen or water with a high tritium content can make targeted recovery economically worthwhile. Other volatile elements leave the fuel and must be recovered, especially
iodine,
technetium, and
carbon-14. Voloxidation also breaks up the fuel or increases its surface area to enhance penetration of reagents in following reprocessing steps.
Advantages
* The process is simple and requires no complex machinery or chemicals above and beyond that required in all reprocessing (
hot cells,
remote handling equipment)
* Products such as
Krypton-85
Krypton-85 (85Kr) is a radioisotope of krypton.
Krypton-85 has a half-life of 10.756 years and a maximum decay energy of 687 keV. It decays into stable rubidium-85. Its most common decay (99.57%) is by beta particle emission with maximum energy ...
or Tritium as well as
Xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
(whose isotope are either stable,
very nearly stable, or quickly decay) can be recovered and sold for use in industry, science or medicine
* Driving off volatile fission products allows for safer storage in interim storage or
deep geological repository
A deep geological repository is a way of storing hazardous or radioactive waste within a stable geologic environment (typically 200–1000 m deep). It entails a combination of waste form, waste package, engineered seals and geology that is suite ...
*
Nuclear proliferation risks are low as no separation of plutonium occurs
* Radioactive material is not chemically mobilized beyond what should be accounted for in long term storage anyway. Substances that are inert as native elements or oxides remain so
* The product can be used as fuel in a
CANDU
The CANDU (Canada Deuterium Uranium) is a Canadian pressurized heavy-water reactor design used to generate electric power. The acronym refers to its deuterium oxide ( heavy water) moderator and its use of (originally, natural) uranium fuel. C ...
reactor or even downblended with similarly treated spent CANDU fuel if too much fissile material is left in the spent fuel.
* The resulting product can be further processed by any of the other processes mentioned above and below. Removal of volatile fission products means that transportation becomes slightly easier compared to spent fuel with damaged or removed cladding
* All volatile products of concern (while helium will be present in the spent fuel, there won't be any radioactive
isotopes of helium
Although there are nine known isotopes of helium (2He) (standard atomic weight: ), only helium-3 () and helium-4 () are stable. All radioisotopes are short-lived, the longest-lived being with a half-life of . The least stable is , with a half-lif ...
) can in principle be recovered in a
cold trap cooled by
liquid nitrogen (temperature: or lower). However, this requires significant amounts of cooling to counteract the effect of decay heat from radioactive volatiles like Krypton-85. Tritium will be present in the form of
tritiated water
Tritiated water is a radioactive form of water in which the usual protium atoms are replaced with tritium. In its pure form it may be called tritium oxide (T2O or 3H2O) or super-heavy water. Pure T2O is corrosive due to self- radiolysis. Di ...
, which is a solid at the temperature of liquid nitrogen.
*
Technetium heptoxide can be removed as a gas by heating above its boiling point of which reduces the issues presented by Technetium contamination in processes like fluoride volatility or PUREX;
ruthenium tetroxide (gaseous above ) can likewise be removed from the spent fuel and recovered for sale or disposal
Disadvantages
* Further processing is needed if the resulting product is to be used for re-enrichment or fabrication of MOX-fuel
* If volatile fission products escape to the environment this presents a radiation hazard, mostly due to , Tritium and . Their safe recovery and storage requires further equipment.
* An
oxidizing agent
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...
/
reducing agent
In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ).
Examples of substances that are commonly reducing agents include the Earth met ...
has to be used for reduction/oxidation steps whose recovery can be difficult, energy consuming or both
Volatilization in isolation
Simply heating spent oxide fuel in an inert atmosphere or vacuum at a temperature between and as a first reprocessing step can remove several volatile elements, including caesium whose isotope
caesium-137 emits about half of the heat produced by the spent fuel over the following 100 years of cooling (however, most of the other half is from
strontium-90, which has a similar half-life).
The estimated overall mass balance for 20,000 g of processed fuel with 2,000 g of cladding is:
Advantages
* Requires no chemical processes at all
* Can in theory be done "self heating" via the
decay heat of sufficiently "fresh" spent fuel
*
Caesium-137 has uses in
food irradiation and can be used to power
radioisotope thermoelectric generator
A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioa ...
s. However, its contamination with stable and long lived reduces efficiency of such uses while contamination with in relatively fresh spent fuel makes the curve of overall radiation and heat output much steeper until most of the has decayed
* Can potentially recover elements like
ruthenium whose ruthenate ion is particularly troublesome in PUREX and which has no isotopes significantly longer lived than a year, allowing possible recovery of the metal for use
* A "third phase recovery" can be added to the process if substances that melt but don't vaporize at the temperatures involved are drained to a container for liquid effluents and allowed to re-solidify. To avoid contamination with low-boiling products which melt at low temperatures, a melt plug could be used to open the container for liquid effluents only once a certain temperature is reached by the liquid phase.
* Strontium, which is present in the form of the particularly troublesome mid-lived fission product is liquid above . However,
Strontium oxide
Strontium oxide or strontia, SrO, is formed when strontium reacts with oxygen. Burning strontium in air results in a mixture of strontium oxide and strontium nitride. It also forms from the decomposition of strontium carbonate SrCO3. It is a stro ...
remains solid below and if strontium oxide is to be recovered with other liquid effluents, it has to be
reduced to the native metal before the heating step. Both Strontium and Strontium oxide form soluble
Strontium hydroxide
Strontium hydroxide, Sr(OH)2, is a caustic alkali composed of one strontium ion and two hydroxide ions. It is synthesized by combining a strontium salt with a strong base. Sr(OH)2 exists in anhydrous, monohydrate, or octahydrate form.
Preparatio ...
and hydrogen upon contact with water, which can be used to separate them from non-soluble parts of the spent fuel.
* As there are little to no chemical changes in the spent fuel, any chemical reprocessing methods can be used following this process
Disadvantages
* At temperatures above the native metal form of several
Actinide
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 info ...
s, including
neptunium (melting point: ) and
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 exh ...
(melting point: , are molten. This could be used to recover a liquid phase, raising proliferation concerns, given that uranium metal remains a solid until . While Neptunium and Plutonium cannot be easily separated by each other via different melting points, the different solubility in water can be used to separate them.
* If "nuclear self heating" is employed, the spent fuel with have much higher
specific activity, heat production and radiation release. If an external heat source is used, significant amounts of external power are needed, which mostly go to heat the uranium.
* Heating and cooling the vacuum chamber and/or the piping and vessels to collect volatile effluents induces
thermal stress. This combines with radiation damage to material and possibly
neutron embrittlement if
neutron sources like
Californium-252
Californium (98Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 245Cf in 1950. There are 20 known radioisotopes rangin ...
are present to a significant extent.
* In the commonly used oxide fuel, some elements will be present both as oxides and as native elements. Depending on their chemical state, they may end up in either the volatalized stream or in the residue stream. If an element is present in both states to a significant degree, separation of that element may be impossible without converting it all to one chemical state or the other
* The temperatures involved are much higher than the melting point of lead () which can present issues with radiation shielding if lead is employed as a shielding material
* If filters are used to recover volatile fission products, those become
low- to intermediate level waste.
Fluoride volatility
In the fluoride volatility process,
fluorine is reacted with the fuel. Fluorine is so much more reactive than even
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
that small particles of ground oxide fuel will burst into flame when dropped into a chamber full of fluorine. This is known as flame fluorination; the heat produced helps the reaction proceed. Most of the
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 ...
, which makes up the bulk of the fuel, is converted to
uranium hexafluoride, the form of uranium used in
uranium enrichment, which has a very low boiling point.
Technetium, the main
long-lived fission product, is also efficiently converted to its volatile hexafluoride. A few other elements also form similarly volatile hexafluorides, pentafluorides, or heptafluorides. The volatile fluorides can be separated from excess fluorine by condensation, then separated from each other by
fractional distillation or selective
reduction.
Uranium hexafluoride and
technetium hexafluoride have very similar boiling points and vapor pressures, which makes complete separation more difficult.
Many of the
fission products volatilized are the same ones volatilized in non-fluorinated, higher-temperature volatilization, such as
iodine,
tellurium
Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionall ...
and
molybdenum; notable differences are that
technetium is volatilized, but
caesium
Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...
is not.
Some transuranium elements such as
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 exh ...
,
neptunium and
americium can form volatile fluorides, but these compounds are not stable when the fluorine partial pressure is decreased. Most of the plutonium and some of the uranium will initially remain in ash which drops to the bottom of the flame fluorinator. The plutonium-uranium ratio in the ash may even approximate the composition needed for
fast neutron reactor fuel. Further fluorination of the ash can remove all the uranium,
neptunium, and plutonium as volatile fluorides; however, some other
minor actinides may not form volatile fluorides and instead remain with the alkaline fission products. Some
noble metals may not form fluorides at all, but remain in metallic form; however
ruthenium hexafluoride is relatively stable and volatile.
Distillation of the residue at higher temperatures can separate lower-boiling
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...
fluorides and
alkali metal
The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
(Cs, Rb) fluorides from higher-boiling
lanthanide and
alkaline earth metal (Sr, Ba) and
yttrium fluorides. The temperatures involved are much higher, but can be lowered somewhat by distilling in a vacuum. If a carrier salt like
lithium fluoride or
sodium fluoride is being used as a solvent, high-temperature distillation is a way to separate the carrier salt for reuse.
Molten salt reactor designs carry out fluoride volatility reprocessing continuously or at frequent intervals. The goal is to return
actinide
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 info ...
s to the molten fuel mixture for eventual fission, while removing
fission products that are
neutron poisons, or that can be more securely stored outside the reactor core while awaiting eventual transfer to permanent storage.
Chloride volatility and solubility
Many of the elements that form volatile high-
valence fluorides will also form volatile high-valence chlorides. Chlorination and distillation is another possible method for separation. The sequence of separation may differ usefully from the sequence for fluorides; for example,
zirconium tetrachloride
Zirconium(IV) chloride, also known as zirconium tetrachloride, () is an inorganic compound frequently used as a precursor to other compounds of zirconium. This white high-melting solid hydrolyzes rapidly in humid air.
Structure
Unlike molecular T ...
and
tin tetrachloride have relatively low boiling points of and . Chlorination has even been proposed as a method for removing zirconium fuel cladding,
instead of mechanical decladding.
Chlorides are likely to be easier than fluorides to later convert back to other compounds, such as oxides.
Chlorides remaining after volatilization may also be separated by solubility in water. Chlorides of alkaline elements like
americium,
curium,
lanthanides,
strontium,
caesium
Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...
are more soluble than those of
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 ...
,
neptunium,
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 exh ...
, and
zirconium.
Advantages of halogen volatility
* Chlorine (and to a lesser extent fluorine) is a readily available
industrial chemical
The chemical industry comprises the companies that produce industrial chemicals. Central to the modern world economy, it converts raw materials (oil, natural gas, air, water, metals, and minerals) into more than 70,000 different products. The pla ...
that is produced in mass quantity
* Fractional distillation allows many elements to be separated from each other in a single step or iterative repetition of the same step
* Uranium will be produced directly as
Uranium hexafluoride, the form used in enrichment
* Many volatile fluorides and chlorides are volatile at relatively moderate temperatures reducing thermal stress. This is especially important as the boiling point of uranium hexafluoride is below that of water, allowing to conserve energy in the separation of high boiling fission products (or their fluorides) from one another as this can take place in the absence of uranium, which makes up the bulk of the mass
* Some fluorides and chlorides melt at relatively low temperatures allowing a "liquid phase separation" if desired. Those low melting salts could be further processed by molten salt electrolysis.
* Fluorides and chlorides differ in water solubility depending on the cation. This can be used to separate them by aqueous solution. However, some fluorides violently react with water, which has to be taken into account.
Disadvantages of halogen volatility
* Many compounds of fluorine or chlorine as well as the native elements themselves are toxic, corrosive and react violently with air, water or both
*
Uranium hexafluoride and
Technetium hexafluoride have very similar boiling points ( and respectively), making it hard to completely separate them from one another by distillation.
* Fractional distillation as used in
petroleum refining requires large facilities and huge amounts of energy. To process tons of uranium would require similarly large facilities as processing tons of petroleum - however, unlike petroleum refineries, the entire process would have to take place inside radiation shielding and there would have to be provisions made to prevent leaks of volatile, poisonous and radioactive fluorides
*
Plutonium hexafluoride boils at this means that any facility capable of separating uranium hexafluoride from Technetium hexafluoride is capable of separating plutonium hexafluoride from either, raising proliferation concerns
* The presence of
alpha emitters induces some (α,n) reactions in fluorine, producing both radioactive and neutrons. This effect can be reduced by separating alpha emitters and fluorine as fast as feasible. Interactions between chlorine's two stable isotopes and on the one hand and alpha particles on the other are of lesser concern as they do not have as high a cross section and do not produce neutrons or long lived radionuclides.
* If carbon is present in the spent fuel it'll form
halogenated hydrocarbons which are extremely potent
greenhouse gases, and hard to chemically decompose. Some of those are toxic as well.
Radioanalytical separations
To determine the distribution of radioactive metals for analytical purposes,
Solvent Impregnated Resins (SIRs) can be used. SIRs are porous particles, which contain an extractant inside their pores. This approach avoids the liquid-liquid separation step required in conventional
liquid-liquid extraction. For the preparation of SIRs for radioanalytical separations, organic Amberlite XAD-4 or XAD-7 can be used. Possible extractants are e.g. trihexyltetradecylphosphonium chloride(CYPHOS IL-101) or N,N0-dialkyl-N,N0-diphenylpyridine-2,6-dicarboxyamides
(R-PDA; R = butyl, octy I, decyl, dodecyl).
Economics
The relative economics of reprocessing-waste disposal and interim storage-direct disposal was the focus of much debate over the first decade of the 2000s. Studies
have modeled the total fuel cycle costs of a reprocessing-recycling system based on one-time recycling of plutonium in existing
thermal reactor
A thermal-neutron reactor is a nuclear reactor that uses slow or thermal neutrons. ("Thermal" does not mean hot in an absolute sense, but means in thermal equilibrium with the medium it is interacting with, the reactor's fuel, moderator and struct ...
s (as opposed to the proposed
breeder reactor cycle) and compare this to the total costs of an open fuel cycle with direct disposal. The range of results produced by these studies is very wide, but all agreed that under then-current economic conditions the reprocessing-recycle option is the more costly one. While the
uranium market - particularly its short term fluctuations - has only a minor impact on the cost of electricity from nuclear power, long term trends in the uranium market ''do'' significantly affect the economics of nuclear reprocessing. If uranium prices were to rise and remain consistently high, "stretching the fuel supply" via MOX fuel, breeder reactors or even the
thorium fuel cycle could become more attractive. However, if uranium prices remain low, reprocessing will remain less attractive.
If reprocessing is undertaken only to reduce the radioactivity level of spent fuel it should be taken into account that spent nuclear fuel becomes less radioactive over time. After 40 years its radioactivity drops by 99.9%, though it still takes over a thousand years for the level of radioactivity to approach that of natural uranium. However the level of
transuranic elements, including
plutonium-239, remains high for over 100,000 years, so if not reused as nuclear fuel, then those elements need secure disposal because of
nuclear proliferation reasons as well as radiation hazard.
On 25 October 2011 a commission of the Japanese Atomic Energy Commission revealed during a meeting calculations about the costs of recycling nuclear fuel for power generation. These costs could be twice the costs of direct geological disposal of spent fuel: the cost of extracting plutonium and handling spent fuel was estimated at 1.98 to 2.14 yen per kilowatt-hour of electricity generated. Discarding the spent fuel as waste would cost only 1 to 1.35 yen per kilowatt-hour.
In July 2004 Japanese newspapers reported that the Japanese Government had estimated the costs of disposing radioactive waste, contradicting claims four months earlier that no such estimates had been made. The cost of non-reprocessing options was estimated to be between a quarter and a third ($5.5–7.9 billion) of the cost of reprocessing ($24.7 billion). At the end of the year 2011 it became clear that Masaya Yasui, who had been director of the Nuclear Power Policy Planning Division in 2004, had instructed his subordinate in April 2004 to conceal the data. The fact that the data were deliberately concealed obliged the ministry to re-investigate the case and to reconsider whether to punish the officials involved.
List of sites
See also
*
Nuclear fuel cycle
*
Breeder reactor
*
Nuclear fusion-fission hybrid
*
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 ...
*
Taylor Wilson's nuclear waste-fired small reactor
*
Global Nuclear Energy Partnership 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
World Nuclear Association
– World Nuclear Association
– Congressional Research Service Report for Congress
Annotated bibliography for reprocessing spent nuclear fuel from the Alsos Digital Library for Nuclear Issues
{{DEFAULTSORT:Nuclear Reprocessing
Radioactive waste