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The fast breeder or fast breeder reactor (FBR) is a type of fast neutron reactor (a nuclear reactor that, since it has no moderator, uses fast neutrons) that also breeds more fissile material than it consumes.
Technical
FBRs usually use a mixed oxide fuel of up to 20% Plutonium dioxide (PuO2) and at least 80% Uranium dioxide (UO2). The plutonium used can be from reprocessed civil or dismantled nuclear weapons sources. Surrounding the reactor core are tubes containing non-fissile Uranium 238 which, by capturing neutrons from the reaction in the core, is partially converted to fissile Plutonium 239 (as is some of the Uranium in the core), which can then be reprocessed for use as nuclear fuel.
Fast reactors typically use liquid metal to cool the core and heat the water used to power the electricity generating turbines. Lead, NaK and sodium have all been used successfully as coolants. Water is not used since it would act as a moderator.
FBR generating plants
FBRs have been built and operated in the USA, France, the former USSR, Japan. One of the plants in the USSR was also previously used for desalination. An experimental FBR (FBTR) was commissioned in 1998 in India and is now in operation, while another experimental FBR in Germany was built but never operated.
One of the first FBRs was the experimental Dounreay Fast Reactor (DFR) which started operating in 1959 at Dounreay, Scotland, using a sodium-potassium coolant, and producing 14MW of electricity. This was followed by a larger 250MW Prototype Fast Reactor (PFR) on the same site in the 1970s until it was closed down in 1994 as the British government withdrew major financial support for nuclear energy development (DRF having previously been closed).
The first and only large scale breeder reactor, Superphénix, entered service in France in 1984, producing 1,200MW of electricity, and uses a liquid sodium heat transfer medium. Its predecessor, Phénix is currently the centre of work on destruction of nuclear waste by transmutation. However, Superphénix was shut down in 1997 due to high costs of operation, and various incidents; the liquid sodium cooling system proved largely unwieldy. Superphénix was also the focus point of various groups hostile to nuclear energy.
As of 2001, the only operational fast breeder in the world is the 300MW Monju reactor in Japan.
Future plants
As of 2003 one FBR was planned for India, and another for China using Soviet technology.
South Korea is developing a design for a standardised modular FBR for export, to complement the standardised PWR and CANDU designs they have already developed and built, but has not yet committed to building a prototype.
The FBR program of India includes the concept of using thorium to breed fissile uranium-233. In theory, it is also possible to use thorium to operate a thermal breeder reactor. This is not possible with purely uranium/plutonium based technology. Thorium fuel is the strategic direction of the power program of India.
Economics
The breeding of plutonium fuel in FBRs, known as the plutonium economy, was for a time believed to be the future of nuclear power. It remains the strategic direction of the power program of Japan. However cheap supplies of uranium and especially of enriched uranium have made current FBR technology uncompetitive with PWR and other thermal reactor designs. PWR designs remain the most common existing power reactor type and also represent most current proposals for new nuclear power stations.
Proliferation
It is generally agreed that the FBR poses a greater risk of proliferation of nuclear weapons than the PWR. Unlike a PWR, an FBR can in theory produce weapons grade material. However, to date all known weapons programs have used far more easily built thermal reactors to produce plutonium.
One problem with FBRs for producing weapons is that they produce significant quantities certain heavy plutonium isotopes (especially 240Pu) which are useless in weapons, and which in fact may cause a premature, low-yield detonation, or even a failed detonation. These isotopes fission either easily, or spontaneously, and would "pre-ignite" a bomb before it was fully assembled, causing at most a puddle of molten, no-longer-critical metal, rather than a nuclear explosion.
Associated reactor types
One design of fast neutron reactor, specifically designed to address the waste disposal and plutonium issues, was the Integral Fast Reactor (a.k.a. Integral Fast Breeder Reactor, although it would be possible to design an IFR to breed or not to breed a net surplus of fissile material)
[1] (http://www.nuc.berkeley.edu/designs/ifr/) [2] (http://www.nationalcenter.org/NPA378.html). It was designed to be fueled once, thereafter producing all its own fuel for operation by a similar process to a breeder reactor.
To solve the waste disposal problem, the IFR had an on site electrorefining fuel reprocessing unit that recycled the uranium and all the transuranics (not just plutonium) via electroplating, leaving just short half-life fission products in the waste. Some of these fission products could later be separated for industrial or medical uses and the rest sent to a waste repository (where they would not have to be stored for anywhere near as long as wastes containing long half-life transuranics). It is thought that it would not be possible to divert fuel from this reactor to make bombs, as several of the transuranics spontaneously fission rapidly enough that any assembly would melt before it could be completed. The project was canceled in the late 1980s after all elements of the system had been tested, but before engineering designs could be completed for an operational power plant.
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