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	[[Category:Done ~~2015~~-07-24]]		[[Category:Done 2017-07-01]]
	<onlyinclude>'''Breeder reactors''' are a type of [[nuclear reactor]] which produce ''more'' [[~~fission~~]]~~able~~ materials than they consume. They are designed to extend the [[nuclear fuel]] supply for the [[electrical generation\|generation of electricity]],<ref name=brit>Encyclopaedia Brittanica. (June 19 2015). ''breeder reactor'' [Online], Available: http://www.britannica.com/technology/breeder-reactor</ref> and have even been mistakenly called a potential [[renewable energy]] source.</onlyinclude><ref>Bernard L. Cohen, University of Pittsburgh. (June 19 2015). ''Breeder reactors: A renewable energy source'' [Online], Available: http://sustainablenuclear.org/PADs/pad11983cohen.pdf</ref> Breeder reactors certainly have the ability to make nuclear fuels quite [[sustainable]] though which was Dr. Cohen's main point, see [[renewable and sustainable energy]] for a more thorough explanation. Concerns about [[nuclear weapons proliferation]] have been one large impediment to creating commercial breeder reactors.		<onlyinclude>'''Breeder reactors''' are a type of [[nuclear reactor]] which produce ''more'' [[fissile]] materials than they consume. They are designed to extend the [[nuclear fuel]] supply for the [[electrical generation\|generation of electricity]],<ref name=brit>Encyclopaedia Brittanica. (June 19 2015). ''breeder reactor'' [Online], Available: http://www.britannica.com/technology/breeder-reactor</ref> and have even been mistakenly called a potential [[renewable energy]] source.</onlyinclude><ref>Bernard L. Cohen, University of Pittsburgh. (June 19 2015). ''Breeder reactors: A renewable energy source'' [Online], Available: http://sustainablenuclear.org/PADs/pad11983cohen.pdf</ref> Breeder reactors certainly have the ability to make nuclear fuels quite [[sustainable]] though which was Dr. Cohen's main point, see [[renewable and sustainable energy]] for a more thorough explanation. Concerns about [[nuclear weapons proliferation]] have been one large impediment to creating commercial breeder reactors.

	Unlike normal reactors which only use [[uranium\|uranium-235]] as their fuel, which is only available in scarce concentrations of around 0.7% of natural uranium without [[uranium enrichment\|enrichment]], breeder reactors also make use of natural uranium-238 which is much more common. They can use approximately 70% of the uranium-238 for production of [[power]], whereas normal reactors can only use around 1% of it. They can also use [[thorium]]-232 to breed uranium-233, another fissionable product.<Ref name=brit/>		Unlike normal reactors which only use [[uranium\|uranium-235]] as their fuel, which is only available in scarce concentrations of around 0.7% of natural uranium without [[uranium enrichment\|enrichment]], breeder reactors also make use of natural uranium-238 which is much more common. They can use approximately 70% of the uranium-238 for production of [[power]], whereas normal reactors can only use around 1% of it. They can also use [[thorium]]-232 to breed uranium-233, another fissionable product.<Ref name=brit/>

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J.williams at 22:41, 11 August 2015

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[[Category:Done 2015-07-24]]
<onlyinclude>'''Breeder reactors''' are a type of [[nuclear reactor]] which produce ''more'' [[fission]]able materials than they consume. They are designed to extend the [[nuclear fuel]] supply for the [[electrical generation|generation of electricity]],<ref name=brit>Encyclopaedia Brittanica. (June 19 2015). ''breeder reactor'' [Online], Available: http://www.britannica.com/technology/breeder-reactor</ref> and have even been mistakenly called a potential [[renewable energy]] source.</onlyinclude><ref>Bernard L. Cohen, University of Pittsburgh. (June 19 2015). ''Breeder reactors: A renewable energy source'' [Online], Available: http://sustainablenuclear.org/PADs/pad11983cohen.pdf</ref> Breeder reactors certainly have the ability to make nuclear fuels quite [[sustainable]] though which was Dr. Cohen's main point, see [[renewable and sustainable energy]] for a more thorough explanation. Concerns about [[nuclear weapons proliferation]] have been one large impediment to creating commercial breeder reactors.

Unlike normal reactors which only use [[uranium|uranium-235]] as their fuel, which is only available in scarce concentrations of around 0.7% of natural uranium without [[uranium enrichment|enrichment]], breeder reactors also make use of natural uranium-238 which is much more common. They can use approximately 70% of the uranium-238 for production of [[power]], whereas normal reactors can only use around 1% of it. They can also use [[thorium]]-232 to breed uranium-233, another fissionable product.<Ref name=brit/>

The most common breeding is of [[plutonium|plutonium-239]], which is bred through the process seen in Figure 1 below.<ref name=hyp>Hyperphysics. (June 19 2015). ''Fast Breeder Reactors'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fasbre.html</ref>

[[File:pubreed.gif|800px|thumb|center|Figure 1. The breeding of 239Pu in a breeder reactor. The neutrons are supplied by the decay of 235U, which transmute 238U to plutonium.<ref name=hyp/>]]

The first experimental breeder reactor (EBR-1) developed was in 1951 in Idaho, U.S.A. Subsequently Russia, Japan, Great Britain and France all developed experimental breeder reactors, however no nation has developed one suitable for high-capacity commercial use.<ref name=brit/> So far, France has made the largest implementation of breeder reactors with their Super-Phenix [[fast breeder reactor]].<ref name=hyp/>

==Types==

There are two categories of breeder reactors, based on the speed of the neutrons. '''Fast breeder reactors''' which use uranium-238 as fuel and '''thermal breeder reactors''' which use thorium-232 as fuel. Fast breeders do not require [[moderation]] since the neutrons need to be moving fast, whereas thermal breeders make us of moderation to achieve slower-moving neutrons.

===Fast===

The most promising type of breeder reactor is the '''Liquid Metal Fast Breeder Reactor (LMFBR)''', which operates by using liquid sodium as its coolant, and breeds plutonium from uranium-238.<ref name=brit/> It works by using highly [[uranium enrichment|enriched uranium]], between 15-20% uranium-235 content, surrounded or "blanketed" by natural uranium-238 in the reactor core.<ref name=hyp/> No [[moderator]] is used to slow down the neutrons, because fast neutrons [[transmutation|transmute]] uranium-238 much more efficiently than slow neutrons.

Using water as a coolant would reduce the neutron abundance, since neutrons are absorbed by water. Therefore liquid sodium is used instead. This immediately raised concerns of safety when initially thought of, since sodium is a highly reactive element. It is important to keep the liquid sodium from contact with air or oxygen to avoid explosions, however they aren't any more dangerous than [[pressurized water reactor]]s.<ref name=hyp/> This is because the sodium doesn't need to be pressurized to remain in a [[liquid]] state like water does; its boiling point is [[celsius|892oC]]. This makes the bursting of pipes far less likely than in other water-reactors. Liquid sodium is also a very good choice because of its [[heat transfer]] capabilities, due to its high [[specific heat capacity]].<ref name=hyp/>

[[File:lmfbr.gif|800px|thumb|center|Figure 2. Liquid metal fast breeder reactor.<ref>Hyperphyics. (June 19 2015). ''Types of nuclear reactors'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/reactor.html#c5</ref>]]

Other fast breeder types include [[supercritical water cooled reactor]]s, [[molten salt reactor]]s, and gas-cooled reactors. You can read more about fast breeder reactors [http://www.world-nuclear.org/info/Current-and-Future-Generation/Fast-Neutron-Reactors/ here].

===Thermal===

The possibility to breed fissile material in slow neutron reactors is unique to [[thorium]], as uranium cannot use thermal neutrons to do so.<ref name=wna>World Nuclear Association. (June 19 2015). ''Thorium'' [Online], Available: http://www.world-nuclear.org/info/Current-and-Future-Generation/Thorium/#b</ref> These reactors would need a fissile material to start the breeding just like fast breeder reactors, however the neutrons produced from this fissile material would need to be slowed down by a moderator.

The technology is much simpler than that of the liquid metal fast breeder; [[light water]] is used as the coolant to remove the [[heat]] produced by the continuous series of fission reactions rather than a liquid metal system.<ref name=brit/>

Thorium hasn't been used in large scale reactors, however some reactors have used it successfully in the past. A light water breeder reactor in Shippingport, Pa. USA operated for 5 years, and by the end of its operation it had 1.4% more fissile fuel than it began with.<ref name=wna/>

==Breeding ratio==

An important concept for a breeder reactor is how much fissionable fuel is being produced compared to how much fuel is being used. This is known as the '''breeding ratio'''. For example for the breeding of plutonium, the ratio would be the amount of plutonium produced to the amount of uranium-235 used. In the liquid metal fast breeder reactor (LMFBR), the breeding ratio is 1.4, however the actual achieved ratio is around 1.2.<Ref name=hyp/>

The number 1.4 is based off of the average number of [[neutron]]s given off by a fission reaction of uranium-235, which is 2.4. Only 1 neutron is needed for the [[fission chain reaction]] to be stable, so the remaining 1.4 neutrons (on average) could be used for the breeding of uranium-238.<Ref name=hyp/>

==Doubling time==

The amount of time for a breeder to produce enough material to fuel a second reactor is called its '''doubling time'''.<ref name=hyp/> Present goals for a breeder reactor's doubling time is 10 years, which means it would operate for 10 years producing energy and breeding fissionable material, after which this material could be used to produce the same energy output for another 10 years.<ref name=hyp/>

==References==
{{reflist}}
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Breeder reactor - Revision history

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