- Fast neutron reactor
Shevchenko BN350 nuclear fast reactor and desalination plant situated on the shore of the
Caspian Sea. The plant generates 135 MWe and provides steam for an associated desalination plant. View of the interior of the reactor hall.]
A fast neutron reactor or simply a fast reactor is a category of
nuclear reactorin which the fission chain reactionis sustained by fast neutrons. Such a reactor needs no neutron moderator, but must use fuel that is relatively rich in fissilematerial when compared to that required for a thermal reactor.
On average, more neutrons per fission are produced from fissions caused by fast neutrons than from those caused by
thermal neutrons. Therefore, there is a much larger excess of neutrons not required to sustain the chain reaction. These neutrons can be used to produce extra fuel, or to transmute long-halflife waste to less troublesome isotopes, such as the Phénixreactor near Cadarachein France, or some can be used for each purpose. Though conventional thermal reactors also produce excess neutrons, fast reactors can produce enough of them to breed more fuel than they consume. Such designs are known as fast breeder reactors. Fast neutrons also have an advantage in the transmutationof nuclear waste. The reason for this is that the ratio between the fission cross-section and the absorption cross-section in plutoniumand minor actinidesare higher in a fast spectrum.
Nuclear reactor design
Water, the most common coolant in thermal reactors, is generally not a feasible coolant for a fast reactor, because it acts as a neutron moderator. However some variants of the Generation IV reactorknown as the supercritical water reactormay technically be considered fast neutron reactors.
All current fast reactors are liquid metal cooled. Early reactors used mercury cooling and
plutoniummetal fuel. NaKcooling is popular in test reactors due to its low melting point. Molten leadcooling has been used in naval propulsion units as well as some other prototype reactors. Some of the newer generation of power stations use molten sodiumcooling. Gas-cooled fast reactors have been researched as well.
In practice sustaining a fission
chain reactionwith fast neutrons means using relatively highly enriched uraniumor plutonium. The reason for this is that fissile reactions are favored at thermal energies, since the ratio between the Pu239 fission cross-sectionU238 absorption cross-section is ~100 in a thermal spectrum and 8 in a fast spectrum. Therefore it is impossible to build a fast reactor using only natural uraniumfuel. However, it is possible to build a fast reactor that will "breed" fuel (from fertile material) by producing more fissile material than it consumes. After the initial fuel charge such a reactor can be refueled by reprocessing. Fission productscan be replaced by adding natural or even depleted uranium with no further enrichment required. This is the concept of the fast breeder reactoror FBR.
So far, all fast neutron reactors have used either
MOXor metal alloy fuel.
Like thermal reactors, fast neutron reactors are controlled by keeping the criticality of the reactor reliant on
delayed neutrons, allowing for control utilizing control rods/blades.However, they cannot rely on Doppler broadening(which affects thermal neutrons) or on negative void coefficient(there is no moderator, so there is no reactivity reduction from moderator boiling).
List of fast reactors
Fast reactors of the past
* Small lead-cooled fast reactors used for naval propulsion, particularly by the
* CLEMENTINE, the first fast reactor, built in 1946 at Los Alamos,
New Mexico. Plutonium metal fuel, mercury coolant, power 25 kW thermal, used for research, especially as a fast neutron source.
EBR-Iat Idaho Falls, which in 1951 became the first reactor to generate significant amounts of electrical power.
* EBR-II Prototype for the Integral Fast Reactor.
Dounreayfast reactors, DFR (Dounreay Fast Reactor) and PFR (Prototype Fast Reactor), in Caithness, in the Highland area of Scotland. DFR commenced operation in 1959 and produced 14MWe. PFR produced 250MWe.
SEFORin Arkansas, a 20 MWtresearch reactor which operated from 1969 to 1972.
Rhapsodiein Cadarache(20 then 40 MW) between 1967 and 1982.
BN-350, constructed by the Soviet Union in Shevchenko (today's Aqtau) on the Caspian Sea, 130MWe plus 80,000 tons of fresh water per day.
Fast Flux Test Facility, 400MWt, Operated flawlessly from 1982 to 1992, at Hanford Washington, now deactivated, liquid sodium is drained with argon backfill under care and maintenance.
Superphénix, in France, 1200MWe, closed in 1997 due to a political decision and very high costs of operation.
* KNK-II, Germany
Clinch River Breeder Reactor, USA
Integral Fast Reactor, a design of fast reactor with an integral fuel cycle, developed and cancelled in the USA in the 1990s.
Phénix, 1973, France, 233 MWe, restarted 2003 for experiments on transmutation of nuclear waste, scheduled end of life 2014
*, 1977-1997, 2003-, Japan
BN-600, 1981, Russia, 600 MWe, scheduled end of life 2010 [cite web
title=Beloyarsk Nuclear Power Plant]
FBTR, 1985, India, 10.5 MWt
Monju reactor, 300MWe, in Japan. was closed in 1995 following a serious sodium leak and fire. It is expected to reopen in 2008.
PFBR, Kalpakkam, India, 500 MWe. Planned to open 2010
* China Experimental Fast Reactor, 65 MWt, planned 2009 [ [http://www.zoomchina.com.cn/new/content/view/23038/81/ China 's first Experimental Fast Reactor (CEFR) Put into Operation in 2009 - Zoom China Energy Intelligence-New site ] ]
Russia, planned 2012 [http://www.inspi.ufl.edu/icapp07/program/abstracts/7348.pdf]
In design phase
* KALIMER, 600 MWe, South Korea, projected 2030 [ [http://ehome.kaeri.re.kr/snsd/eng/organization/organization.htm ***지속가능원자력시스템*** ] ]
Generation IV reactorUS-proposed international effort, after 2030
Gas-cooled fast reactor
Sodium-cooled fast reactor
**Lead-cooled fast reactor
*JSFR, Japan, project for a 1500 MWe reactor begin in 1998->2010
External links and references
* [http://www.insc.anl.gov/dbfiles/plant_category/FBR/bn.2.html ANL report on EARLY SOVIET FAST REACTORS]
* [http://sciam.com/article.cfm?chanID=sa006&colID=1&articleID=000D5560-D9B2-137C-99B283414B7F0000 Article on recent work on fast neutron reactors in Scientific American, December, 2005]
* [http://www.iaea.org/inisnkm/nkm/aws/fnss/auxiliary/iaea.html Fast Reactor Data Retrieval and Knowledge Preservation] seeks to establish a comprehensive, international inventory of fast reactor data and knowledge, which would be sufficient to form the basis for fast reactor development in 30 to 40 years from now.
* [http://www.world-nuclear.org/info/inf08.html Advanced Nuclear Power Reactors]
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