A
breeder reactor is a
nuclear reactorA nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate.The most significant use of nuclear reactors is as an energy source for the generation of electrical power and for the power in some ships...
that generates new
fissileIn nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission.All known fissile materials are capable of sustaining a chain reaction in which either thermal or slow neutrons or fast neutrons predominate...
or
fissionableNuclear fuel is any material that can be consumed to derive nuclear energy, by analogy to chemical fuel that is burned to derive energy. By far the most common type of nuclear fuel is heavy fissile elements that can be made to undergo nuclear fission chain reactions in a nuclear fission reactor;...
material at a greater rate than it consumes such material. These reactors were initially (1940s and 1960s) considered appealing due to their superior fuel economy; a normal reactor is able to consume less than 1% of the natural
uraniumUranium is a silvery-white metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. Besides its 92 protons, a uranium nucleus can have between 141 and 146 neutrons. The most common uranium isotopes are U-238 and U-235 . A uranium atom has...
that begins the fuel cycle, whereas a breeder can utilize a much greater percentage of the initial fissionable material, and with re-processing, can use almost all of the initial fissionable material. Breeders can be designed to utilize
thoriumThorium is a chemical element with the symbol Th and atomic number 90. It is a naturally occurring, slightly radioactive metal. Thorium is estimated to be about three to four times more abundant than uranium in the earth's crust...
, which is more abundant than uranium. Currently, there is renewed interest in breeders because they would consume less natural uranium (less than 3% compared to conventional light-water reactors), and generate less
wasteRadioactive waste is a waste product containing radioactive material. It is usually the product of a nuclear process such as nuclear fission. However, industries not directly connected to the nuclear industry may produce quantities of radioactive waste. The majority of radioactive waste is...
, for equal amounts of energy, by converting non-fissile isotopes of uranium into nuclear fuel.
Production of fissile material in a reactor occurs by
neutron irradiationNeutron radiation is a kind of non-ionizing radiation which consists of free neutrons.-Sources:Neutrons may be emitted during either spontaneous or induced nuclear fission, nuclear fusion processes, very high energy reactions such as in the Spallation Neutron Source and in cosmic ray interactions,...
of
fertile materialFertile material is a term used to describe nuclides which generally themselves do not undergo induced fission but from which fissile material is generated by neutron absorption and subsequent nuclei conversions...
, particularly
uranium-238Uranium-238 is the most common isotope of uranium found in nature. When hit by a neutron, it eventually becomes plutonium-239 ....
and
thorium-232Thorium-232 is the primary abundant nuclide of thorium. It is a slightly unstable radionuclide that is found in the earth's crust. It is a fertile material able to absorb a neutron and undergo transmutation into a nuclide that is able to support fission .In the form of Thorotrast, a thorium oxide...
. In a breeder reactor, these materials are deliberately provided, either in the fuel or in a
breeder blanket surrounding the core, or most commonly in both. Production of fissile material takes place to some extent in the fuel of all current commercial nuclear power reactors. Towards the end of its life, a uranium (not
MOXMixed oxide, or MOX fuel, is nuclear fuel containing more than one oxide of fissile or fertile materials. Specifically, it usually refers to a blend of oxides of plutonium and natural uranium, reprocessed uranium, or depleted uranium which behaves similarly to the low-enriched uranium oxide fuel...
, just uranium)
PWRPressurized water reactors comprise a majority of all western nuclear power plants and are one of two types of light water reactor , the other type being boiling water reactors . In a PWR the primary coolant is pumped under high pressure to the reactor core, then the heated water transfers...
fuel element is producing more power from the fissioning of
plutoniumPlutonium is a rare transuranic radioactive element. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen and...
than from the remaining
uranium-235Uranium-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 fission chain reaction...
. Historically, in order to be called a
breeder, a reactor must be specifically designed to create more fissile material than it consumes.
Breeding ratio
One measure of a reactor's performance is the "breeding ratio" (the average number of fissile atoms created per fission event). Historically, attention has focused upon reactors with low breeding ratios (at or slightly above a breakeven value of 1.0), so that they produce only slightly more fissile material than they consume. Such designs range from a breeding ratio of 1.01 for the
Shippingport ReactorThe Shippingport Atomic Power Station, "the world’s first full-scale atomic electric power plant devoted exclusively to peacetime uses," was located near the present-day Beaver Valley Nuclear Generating Station on the Ohio River in Beaver County, Pennsylvania, about from Pittsburgh...
running on thorium fuel and cooled by conventional light water to the Russian
BN-350The BN-350 was a sodium-cooled fast reactor nuclear power plant located at Aktau , Kazakhstan, situated on the shore of the Caspian Sea. Construction of the BN-350 Fast breeder reactor began in 1964, and the plant first produced electricity in 1973...
liquid-metal-cooled reactor with a breeding ratio of over 1.2. Theoretical models of breeders with liquid sodium coolant flowing through tubes inside fuel elements ("tube-in-shell" construction) show breeding ratios with an upper limit of 1.8 are possible.
In normal operation, most large commercial reactors experience some degree of fuel breeding. It is customary to refer only to machines optimized for this trait as true breeders, but industry trends are pushing breeding ratios steadily higher, thus blurring the distinction.
Breeding vs burnup
All commercial
light water reactorThe light water reactor or LWR is a type of thermal reactor that uses light water as a coolant and neutron moderator as opposed to heavy water as a coolant/moderator...
s breed fuel, but they have breeding ratios that are very low (though still very significant) compared to machines traditionally considered "breeders." In recent years, the commercial power industry has been emphasizing high-
burnupIn nuclear power technology, burnup is a measure of the number of fuel atoms that underwent fission. It is normally quoted in megawatt–days per metric ton of uranium metal or its equivalent , or gigawatt–days/MTU...
fuels, which are typically enriched to higher percentages of U-235 than standard reactor fuels so that they last longer in the reactor core. As burnup increases, a higher percentage of the total power produced in a reactor is due to the fuel bred inside the reactor.
At a burnup of 30 gigawatt-days per metric ton of uranium (GWd/MTU), about thirty percent of the total energy released comes from bred plutonium. At 40 GWd/MTU, that percentage increases to about forty percent. This corresponds to a breeding ratio for these reactors of about 0.4 to 0.5. That is to say, about half of the fissile fuel in these reactors is bred there. Correspondingly, this effect extends the cycle life for such fuels to sometimes nearly twice what it would be otherwise.
MOX fuelMixed oxide, or MOX fuel, is nuclear fuel containing more than one oxide of fissile or fertile materials. Specifically, it usually refers to a blend of oxides of plutonium and natural uranium, reprocessed uranium, or depleted uranium which behaves similarly to the low-enriched uranium oxide fuel...
has a smaller breeding effect than U-235 fuel and is thus more challenging and slightly less economic to use due to a quicker drop off in reactivity through cycle life.
This is of interest largely because next-generation reactors such as the
European Pressurized ReactorThe EPR is a third generation pressurized water reactor design. It has been designed and developed mainly by Framatome and Electricité de France in France, and Siemens AG in Germany...
, AP1000 and
pebble bed reactorThe pebble bed reactor is a graphite-moderated, gas-cooled, nuclear reactor. It is a type of Very high temperature reactor [formally known as the high temperature gas reactor ], one of the six classes of nuclear reactors in the Generation IV initiative...
are designed to achieve very high burnup. This directly translates to higher breeding ratios. Current commercial power reactors have achieved breeding ratios of roughly 0.55, and next-generation designs like the AP1000 and EPR should have breeding ratios of 0.7 to 0.8, meaning that they produce 70 to 80 percent as much fuel as they consume, improving their fuel economy by roughly 15 percent compared to current high-burnup reactors.
Breeding of fissile fuel is a common feature in reactors, but in commercial reactors not optimized for this feature it is referred to as "enhanced burnup". Up to a third of all electricity produced in the current US reactor fleet comes from bred fuel, and the industry is working steadily to increase that percentage as time goes on.
Types of breeder reactors
Two types of traditional breeder reactor have been proposed:
- fast breeder reactor
The fast breeder or fast breeder reactor is a fast neutron reactor designed to breed fuel by producing more fissile material than it consumes...
or FBR. The superior neutron economy of a fast neutron reactorA fast neutron reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons...
makes it possible to build a reactor that, after its initial fuel charge of plutoniumPlutonium is a rare transuranic radioactive element. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen and...
, requires only natural (or even depleted) uranium feedstock as input to its fuel cycle. This fuel cycle has been termed the plutonium economy.
- thermal breeder reactor. The excellent neutron capture characteristics of fissile uranium-233
Uranium-233 is a fissile artificial isotope of uranium, which has been used in a few nuclear reactors and has been proposed for much wider use as a nuclear fuel. It has a half-life of 160,000 years....
make it possible to build a moderated reactor that, after its initial fuel charge of enriched uraniumEnriched uranium is a kind of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% 238U isotope, with 235U only constituting about 0.711% of its weight...
, plutonium or MOXMOX might be a name or acronym for:*Malaysian Oxygen Berhad - A Malaysian company that is specializes in providing total gas solutions.*Mixed Oxide Fuel, from nuclear reprocessing*An alien race in the TimeSplitters 2 video game, the Mox...
, requires only thoriumThorium is a chemical element with the symbol Th and atomic number 90. It is a naturally occurring, slightly radioactive metal. Thorium is estimated to be about three to four times more abundant than uranium in the earth's crust...
as input to its fuel cycle. thorium-232Thorium-232 is the primary abundant nuclide of thorium. It is a slightly unstable radionuclide that is found in the earth's crust. It is a fertile material able to absorb a neutron and undergo transmutation into a nuclide that is able to support fission .In the form of Thorotrast, a thorium oxide...
produces uranium-233 after neutron capture and beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted. In the case of electron emission, it is referred to as beta minus , while in the case of a positron emission as beta plus...
.
In addition to this, there is some interest in so-called "reduced moderation reactors", which are derived from conventional reactors and use conventional fuels and coolants, but are designed to be reasonably efficient as breeders. Such designs typically achieve breeding ratios of 0.7 to 1.01 or even higher.
Reprocessing
Use of a breeder reactor assumes
nuclear reprocessingNuclear reprocessing separates components of spent nuclear fuel.Reprocessing serves multiple purposes, whose relative importance has changed over time:*Producing plutonium for nuclear weapons...
of the breeder blanket at least, without which the concept is meaningless. In practice, all proposed breeder reactor programs involve reprocessing of the fuel elements as well. This is important due to nuclear weapons proliferation concerns, as any nation conducting reprocessing using the traditional aqueous-based
PUREXPUREX is the de facto standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel. It is based on liquid-liquid extraction ion-exchange...
family of reprocessing techniques could potentially divert plutonium towards weapons building. In practice, commercial plutonium from reactors with significant burnup would require sophisticated weapon designs, but the possibility must be considered. To address this concern, modified aqueous reprocessing systems, which add extra reagents, forcing minor
actinideThe actinoid or actinide series encompasses the 15 chemical elements that lie between actinium and lawrencium included on the periodic table, with atomic numbers 89 - 103...
"impurities" such as
curiumCurium is a synthetic chemical element with the symbol Cm and atomic number 96. A radioactive metallic transuranic element of the actinide series, curium is produced by bombarding plutonium with alpha particles and was named for Marie Curie and her husband Pierre.- Characteristics :The isotope...
and
neptuniumNeptunium is a chemical element with the symbol Np and atomic number 93. A radioactive metallic element, neptunium is the first transuranic element and belongs to the actinide series. Its most stable isotope, 237Np, is a by-product of nuclear reactors and plutonium production and it...
to commingle with the plutonium, have been proposed. Such impurities matter little in a fast spectrum reactor, but make weaponizing the plutonium extraordinarily difficult, such that even very sophisticated weapon designs are likely to fail to fire properly. Such systems as the TRUEX and SANEX are meant to address this.
Even more comprehensive are systems such as the
Integral Fast ReactorThe Integral Fast Reactor was a design for a fast reactor distinguished by a nuclear fuel cycle using reprocessing via electrorefining at the reactor site itself.The U.S. Department of Energy built a prototype but canceled the project in 1994, three years before completion...
(IFR) pyroprocessing system, which uses pools of molten
cadmiumCadmium is a chemical element with the symbol Cd and atomic number 48. The soft, bluish-white transition metal is chemically similar to the two other metals in group 12, zinc and mercury. Similar to zinc it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
and electrorefiners to reprocess metallic fuel directly on-site at the reactor. Such systems not only commingle all the minor actinides with both uranium and plutonium, they are compact and self-contained, so that no plutonium-containing material ever needs to be transported away from the site of the breeder reactor. Breeder reactors incorporating such technology would most likely be designed with breeding ratios very close to 1.00, so that after an initial loading of enriched uranium and/or plutonium fuel, the reactor would then be refueled only with small deliveries of natural uranium metal. A quantity of natural uranium metal equivalent to a block about the size of a milk crate delivered once per month would be all the fuel such a 1 gigawatt reactor would need. Such self-contained breeders are currently envisioned as the final self-contained and self-supporting ultimate goal of nuclear reactor designers.
The Fast Breeder Reactor
Several prototype FBRs have been built, ranging in electrical output from a few light bulbs' equivalent (
EBR-IExperimental Breeder Reactor I is a decommissioned research reactor and U.S. National Historic Landmark located in the desert about southeast of Arco, Idaho. At 1:50pm on December 20, 1951 it became the world's first electricity-generating nuclear power plant when it produced sufficient...
, 1951) to over 1000 MWe. As of 2006, the technology is not economically competitive to thermal reactor technology; but
IndiaIndia, officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the south, the Arabian Sea on the west, and the Bay of Bengal...
,
Japanis an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, People's Republic of China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
,
ChinaChina is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
,
KoreaKorea is a civilization and formerly unified nation currently divided into two states. Located on the Korean Peninsula, it borders China to the northwest, Russia to the northeast, and is separated from Japan to the east by the Korea Strait....
and
RussiaRussia , officially known as both Russia and the Russian Federation , is a country in northern Eurasia . It is a semi-presidential republic, comprising 83 federal subjects...
are all committing substantial research funds to further development of Fast Breeder reactors, anticipating that rising uranium prices will change this in the long term.
Looking further ahead, three of the proposed
generation IV reactorGeneration IV reactors are a set of theoretical nuclear reactor designs currently being researched. Most of these designs are generally not expected to be available for commercial construction before 2030, with the exception of a version of the Very High Temperature Reactor called the Next...
types are FBRs:
- Gas-Cooled Fast Reactor
The Gas-Cooled Fast Reactor system is a nuclear reactor design which is currently in development. Classed as a Generation IV reactor, it features a fast-neutron spectrum and closed fuel cycle for efficient conversion of fertile uranium and management of actinides...
(GFR) cooled by heliumHelium is the chemical element with atomic number 2, and is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert monatomic gas that heads the noble gas group in the periodic table...
.
- Sodium-Cooled Fast Reactor
The Sodium-cooled fast reactor or SFR is a Generation IV reactor project to design an advanced fast neutron reactor.It builds on two closely related existing projects, the LMFBR and the Integral Fast Reactor, with the objective of producing a fast-spectrum, sodium-cooled reactor and a closed fuel...
(SFR) based on the existing Liquid Metal FBR (LMFBR) and Integral Fast ReactorThe Integral Fast Reactor was a design for a fast reactor distinguished by a nuclear fuel cycle using reprocessing via electrorefining at the reactor site itself.The U.S. Department of Energy built a prototype but canceled the project in 1994, three years before completion...
designs.
- Lead-Cooled Fast Reactor (LFR) based on Soviet naval propulsion units.
As well as their thermal breeder program,
IndiaIndia, officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the south, the Arabian Sea on the west, and the Bay of Bengal...
is also developing FBR technology, using both uranium and thorium feedstocks.
The Thermal Breeder Reactor
The
Advanced Heavy Water ReactorThe Advanced Heavy Water Reactor is the latest Indian design for a next generation nuclear reactor that will burn Thorium in its fuel core. It is slated to form the third stage in India's 3 stage fuel cycle plan...
is one of the few proposed large-scale uses of
thoriumThorium is a chemical element with the symbol Th and atomic number 90. It is a naturally occurring, slightly radioactive metal. Thorium is estimated to be about three to four times more abundant than uranium in the earth's crust...
. As of 2006 only
IndiaIndia, officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the south, the Arabian Sea on the west, and the Bay of Bengal...
is developing this technology. Indian interest is motivated by their substantial thorium reserves; almost a third of the world's thorium reserves are in India, which in contrast has less than 1% of the world's uranium. Their stated intention is to use both fast and thermal breeder reactors to supply both their own fuel and a surplus for non-breeding thermal power reactors. Total worldwide resources of thorium are roughly three times those of uranium, so in the extreme long term this technology may become of more general interest.
The Liquid Fluoride Reactor was also developed as a thermal breeder. Liquid-fluoride reactors have many attractive features, such as deep inherent safety (due to their strong negative temperature coefficient of reactivity and their ability to drain their liquid fuel into a passively-cooled and non-critical configuration) and ease of operation. They are particularly attractive as thermal breeders because they can isolate protactinium-233 (the intermediate breeding product of thorium) from neutron flux and allow it to decay to uranium-233, which can then be returned to the reactor. Typical solid-fueled reactors are not capable of accomplishing this step and thus
U-234Uranium-234 is an isotope of Uranium. In natural uranium and uranium ore, 234U occurs as an indirect decay product of 238U, but it makes up only 0.0055% of the raw uranium because its half-life of just 246,000 years is only about 1/18,000 as long as the half-life of...
is formed upon further neutron irradiation.
Traveling Wave Reactor
A theoretical type of self-contained breeder reactor called a
traveling wave reactorThe concept of the traveling wave reactor was first suggested in 1988 by the Soviet thermonuclear weapons designer Lev P. Feoktistov, and then again in the 1990s by Manhattan Project member Edward Teller, a scientist also credited with inventing the hydrogen bomb.-Principle:The broader category of...
is proposed in a patent by
Intellectual VenturesIntellectual Ventures is a private company claiming to invest in "pure invention". Its goal is to develop a large patent portfolio rather than to actually develop new systems, although it launched a prototyping and research laboratory in 2009 called Intellectual Ventures Lab. Its employees are...
. If it were to be built, it would be fueled by natural uranium, depleted uranium or thorium and would be able to operate for many years without needing any refueling.
Notable Breeder Reactors
- Experimental Breeder Reactor I
Experimental Breeder Reactor I is a decommissioned research reactor and U.S. National Historic Landmark located in the desert about southeast of Arco, Idaho. At 1:50pm on December 20, 1951 it became the world's first electricity-generating nuclear power plant when it produced sufficient...
(U.S., decommissioned 1964, world's first electricity-producing nuclear power plant)
- BN-600 (Russia, end of life 2010)
- Clinch River Breeder Reactor (U.S., construction abandoned in 1982 because the US halted its spent-fuel reprocessing
Nuclear reprocessing separates components of spent nuclear fuel.Reprocessing serves multiple purposes, whose relative importance has changed over time:*Producing plutonium for nuclear weapons...
program and thus made breeders pointless)
- Monju
is Japan's only fast breeder reactor. Located in Tsuruga, Fukui Prefecture in Japan, the reactor began construction in 1985 and first achieved criticality in April 1994....
(Japan, being brought online again after serious sodium leak and fire in 1995)
- Superphénix
Superphénix or SPX is a nuclear power station on the Rhône River at Creys-Malville in France, close to the border with Switzerland. A fast breeder reactor, it halted electricity production in 1996 and was closed as a commercial plant in 1997....
(France, closed 1998)
See also
- Liquid Fluoride Reactor
- Fast neutron reactor
A fast neutron reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons...
- Sodium-cooled fast reactor
The Sodium-cooled fast reactor or SFR is a Generation IV reactor project to design an advanced fast neutron reactor.It builds on two closely related existing projects, the LMFBR and the Integral Fast Reactor, with the objective of producing a fast-spectrum, sodium-cooled reactor and a closed fuel...
- Integral Fast Reactor
The Integral Fast Reactor was a design for a fast reactor distinguished by a nuclear fuel cycle using reprocessing via electrorefining at the reactor site itself.The U.S. Department of Energy built a prototype but canceled the project in 1994, three years before completion...
- Lead-cooled fast reactor
The lead-cooled fast reactor is a nuclear power Generation IV reactor that features a fast neutron spectrum, molten lead or lead-bismuth eutectic coolant, and a closed fuel cycle. Options include a range of plant ratings, including a number of 50 to 150 MWe units featuring long-life,...
- Gas-cooled fast reactor
The Gas-Cooled Fast Reactor system is a nuclear reactor design which is currently in development. Classed as a Generation IV reactor, it features a fast-neutron spectrum and closed fuel cycle for efficient conversion of fertile uranium and management of actinides...
- Generation IV reactor
Generation IV reactors are a set of theoretical nuclear reactor designs currently being researched. Most of these designs are generally not expected to be available for commercial construction before 2030, with the exception of a version of the Very High Temperature Reactor called the Next...
- Radioactive boy scout
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