Breeder reactor 228058 223906168 2008-07-06T13:05:33Z SmackBot 433328 Date the maintenance tags or general fixes {{Refimprove|date=August 2007}} {{Mergefrom|Fast breeder reactor|date=July 2008}} A '''breeder reactor''' is a [[nuclear reactor]] that generates new [[fissile]] or [[Nuclear fuel|fissionable]] material at a greater rate than it consumes such material. These reactors were initially (1950s and 1960s) considered appealing due to their superior fuel economy; a normal reactor can consume less than 1% of the natural [[uranium]] 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. Also, breeders can be designed to utilize [[thorium]], which is more abundant than uranium. Renewed interest is also due to the dramatic reduction in waste they can produce and especially long-lived [[radioactive waste]] components. Production of fissile material in a reactor occurs by [[neutron radiation|neutron irradiation]] of [[fertile material]], particularly [[uranium-238]] and [[thorium-232]]. 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 reactor]]s. Towards the end of its life, a uranium (not [[MOX fuel|MOX]], just uranium) [[Pressurized water reactor|PWR]] fuel element is producing more power from the fissioning of [[plutonium]] than from the remaining [[uranium-235]]. 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 Reactor]]<ref> Adams, R. (1995). [http://www.atomicinsights.com/oct95/LWBR_oct95.html Light Water Breeder Reactor], ''Atomic Energy Insights'' '''1'''. </ref><ref> Kasten, P.R. (1998) [http://www.princeton.edu/~globsec/publications/pdf/7_3kasten.pdf Review of the Radkowsky Thorium Reactor Concept]. ([[PDF]]) ''Science & Global Security'' '''7''', 237–269.</ref> running on thorium fuel and cooled by conventional light water to the Russian [[BN-350 reactor|BN-350]] liquid-metal-cooled reactor with a breeding ratio of over 1.2.<ref>[http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fasbre.html Fast Breeder Reactors], Department of Physics & Astronomy, [[Georgia State University]]. Retrieved [[16 October]] [[2007]].</ref> Theoretical models of gas-cooled breeders show breeding ratios with an upper limit of 1.8 are possible.<ref>Hiraoka, T., Sako, K., Takano, H., Ishii,&nbsp;T. and Sato,&nbsp;M. (1991). [http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=5560940 A high-breeding fast reactor with fission product gas purge/tube-in-shell metallic fuel assemblies]. ''Nuclear Technology'' '''93''', 305–329.</ref> 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.<ref>Matthews, B. (1996). [http://arq.lanl.gov/source/orgs/nmt/nmtdo/AQarchive/96spring/plutonium_future.html Division Director Discusses Plutonium Future part&nbsp;1]. ''The Actinide Research Quarterly'' '''Spring''', 6–7.</ref> ==Breeding vs burnup== All commercial [[light water reactor]]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-[[burnup]] 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&nbsp;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.<ref> {{cite web | url= http://world-nuclear.org/info/inf15.html | title= Information Papers: Plutonium | date= April 2008 |work= | publisher= [[World Nuclear Association]] (WNA) | accessdate= 2008-06-24 }} </ref> Correspondingly, this effect extends the cycle life for such fuels to sometimes nearly twice what it would be otherwise. [[MOX 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 Reactor]], [[AP1000]] and [[pebble bed reactor]] are designed to achieve very high burnup.<!-- [http://www-personal.umich.edu/~akalchik/NERS442/DCD.Nuclear.Design.pdf] dead link --> 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&nbsp;percent as much fuel as they consume, improving their fuel economy by roughly 15&nbsp;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]]''' or FBR. The superior neutron economy of a [[fast neutron reactor]] makes it possible to build a reactor that, after its initial fuel charge of [[plutonium]], requires only natural (or even depleted) uranium feedstock as input to its fuel cycle. This fuel cycle has been termed the [[plutonium economy]]. * '''[[Breeder_reactor#The_thermal_breeder_reactor|thermal breeder reactor]]'''. The excellent neutron capture characteristics of fissile [[uranium-233]] make it possible to build a moderated reactor that, after its initial fuel charge of [[enriched uranium]], plutonium or [[MOX]], requires only [[thorium]] as input to its fuel cycle. [[thorium-232]] produces uranium-233 after neutron capture and [[beta decay]]. In addition to this, there is some interest in so-called "reduced moderation reactors".<ref> Yamashita, J., Kawamura, F. and Mochida, T. (2004). [http://www.hitachi.com/ICSFiles/afieldfile/2004/09/07/r2004_03_105.pdf Next-generation Nuclear Reactor Systems for Future Energy]. ([[PDF]]) ''Hitachi Review'' '''53''', 131–135.</ref> 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 reprocessing]] 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 [[PUREX]] 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 are proposed which add extra reagents which force minor [[actinide]] "impurities" such as [[curium]] and [[neptunium]] to commingle with the plutonium. 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 [[Nuclear reprocessing#TRUEX|TRUEX]] and [[Nuclear reprocessing#SANEX|SANEX]] are meant to address this. Even more comprehensive are systems such as the [[Integral Fast Reactor]] (IFR) pyroprocessing system, which uses pools of molten [[cadmium]] and electrorefiners to reprocess metallic fuel directly on-site at the reactor.<ref>Hannum, W.H., Marsh, G.E. and Stanford, G.S. (2004). [http://www.gemarsh.com/wp-content/uploads/Purex&Pyro%20P&S%20Jul04.pdf PUREX and PYRO are not the same]. ''Physics and Society'' '''July'''.</ref> 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&nbsp;gigawatt reactor would need.<ref>[[University of Washington]] (2004). [http://www.evworld.com/library/energy_numbers.pdf Energy Numbers: Energy in natural processes and human consumption, some numbers]. Retrieved [[16 October]] [[2007]].</ref> 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== {{main|fast breeder reactor}} {{Unreferencedsection|date=August 2007}} Several prototype FBRs have been built, ranging in electrical output from a few light bulbs' equivalent ([[Experimental Breeder Reactor I|EBR-I]], 1951) to over 1000&nbsp;MWe. As of [[2006]], the technology is not economically competitive to thermal reactor technology; but [[Japan]], [[China]], [[Korea]] and [[Russia]] are all committing substantial research funds to further development based on existing Liquid Metal FBR ([[LMFBR]]) designs, anticipating that rising uranium prices will change this in the long term. Looking further ahead, three of the proposed [[generation IV reactor]] types are FBRs: * '''[[Gas-Cooled Fast Reactor]]''' (GFR) cooled by [[helium]]. * '''[[Sodium-Cooled Fast Reactor]]''' (SFR) based on the existing Liquid Metal FBR ([[LMFBR]]) and [[Integral Fast Reactor]] designs. * '''[[Lead-Cooled Fast Reactor]]''' (LFR) based on Soviet naval propulsion units. As well as their thermal breeder program, [[India]] is also developing FBR technology, using both uranium and thorium feedstocks. ==The thermal breeder reactor== {{Unreferencedsection|date=August 2007}} The [[Advanced Heavy Water Reactor]] is one of the few proposed large-scale uses of [[thorium]]. As of 2006 only [[India]] 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 [[Uranium-234|U-234]] is formed upon further neutron irradiation. ====Notable Breeder Reactors==== * [[BN-600]] (Russia, end of life 2010)<ref>{{cite web |url=http://www.insc.anl.gov/neisb/neisb4/NEISB_3.2.A2.html |title=Beloyarsk Nuclear Power Plant }}</ref><ref>{{cite web |url=http://www.bellona.org/english_import_area/international/russia/npps/beloyarsk/35835 |title=Russian parliament and Kremlin party defends fast-breeder reactors }}</ref> * [[Clinch River Breeder Reactor]] (U.S., construction abandoned, not economically viable)<ref>{{cite web |url=http://www.heritage.org/Research/EnergyandEnvironment/EM5.cfm |title=Clinch River: The SST of the Eighties |publisher=The Heritage Foundation |author=Henry Sokolski |date=1982-09-24 |language=English }}</ref> * [[Monju]] (Japan, being brought online again after serious sodium leak and fire 1995)<ref>{{cite web |url=http://www.yomiuri.co.jp/dy/national/20080210TDY02307.htm |title=Govt set to OK refueling of Monju nuclear reactor |publisher=Daily Yomiuri Online |author=Yomiuri Shimbun |date=2008-02-10 |language=English }}</ref> * [[Superphénix]] (France, closed 1998)<ref>{{cite web |url=http://www.icjt.org/plants/uni/a/uni81a.html |title=Nuke Database System }}</ref> ==References== {{reflist}} ==See also== * [[Liquid Fluoride Reactor]] * [[Fast neutron reactor]] * [[Sodium-cooled fast reactor]] * [[Integral Fast Reactor]] * [[Lead cooled fast reactor|Lead-cooled fast reactor]] * [[Gas-cooled fast reactor]] * [[Generation IV reactor]] * [[Radioactive boy scout]] ==External links== * [http://www.nationalcenter.org/NPA378.html Breeder terminology] {{Nuclear Technology}} [[Category:Nuclear power reactor types]] [[cs:Množivý reaktor]] [[de:Brutreaktor]] [[el:Αναπαραγωγικός αντιδραστήρας]] [[es:Reactor reproductor rápido]] [[fr:Surgénération]] [[hu:Tenyésztőreaktor]] [[ml:ബ്രീഡര്‍ റിയാക്റ്റര്‍]] [[nl:Kweekreactor]] [[ja:高速増殖炉]] [[pl:FBR]] [[fi:Hyötöreaktori]] [[sv:Bridreaktor]]