Fast Neutron Reactor
A Fast Neutron Reactor is a specific type of reactor that different from a Thermal ReactorThermal Reactor-- it is not very common because unlike a thermal reactor that uses neutron to sustain the chain reaction, a FNR has no neutron moderation and less primary coolant due to an excess of fast neutrons
- the capture to fission ratio is lower is fast reactors
- high number of neutron produced per one fission
- Neutron Flux has differences too
The following image shows the neutron flux differences
Neutron Flux differences in LMFBR vs ThermalsNeutron Flux differences in LMFBR vs ThermalsThis image shows the major differences in Thermal and LMFBR enutron energy with the neutron flux as the y axis and energy as X.
As neutron flux increases, thermal experiences a major slope downwards while in the .001 eV to 10 eV range, LMFBR doesn't even play a role - it is at a very high neutron flux and energy that LMFBR is effective
Back to Thermal Reactor
Back to Fast Neutron Reactor
FNR vs Thermal NE-Flux.png
One main difference in FNR vs TR is that the missing reactivity from the neutron moderators means that you need higher enrichment of natural UraniumUraniumNatural Uranium VS \#stub-- around 10% or more. Most reactors use hexagonal lattices (similar to VVER Reactor (WWER)VVER Reactor (WWER)Water-Water energetic reactor (WWER) or the Russian VVER from (from Russian: водо-водяной энергетический реактор, romanized: vodo-vodyanoi enyergeticheskiy reaktor, lit. 'water-water power reactor') is a series of PWR reactor designs developed originally by the Soviet Union, and now Russia, by OKB Gidropress. One of the initial reactor designs other then the RBMK Reactor, this design is a Thermal Reactor design using control rods and Light Water coolant. Their power varies, with electric powers) to reach smaller ratios of coolant to fuel. Compact nuclear cores are more common in FNRs, to reach desired core reactivity and therefore means that FNR cores usually achieve higher power densities. Neither Light WaterLight WaterLight water, although appearing to have a fancy name, is literally just ordinary water....except it does contain a small amount of Heavy Water. The point of light water is that it can be used as a moderator --however it can only be used in certain situations, as it absorbs too many neutrons to be used with unenriched uranium (which is why light water is presumably used in Spent Fuel Pools) Light water is mainly used in BWR reactors & PWR reactors Uranium Enrichment is necessary for the usage of nor Heavy WaterHeavy WaterHeavy Water is literally Deuterium oxide. It's molecular formula is that of regular Light Water--H2O, however it contains two atoms of deuterium and one atom of Hydrogen; resulting in 2D2O. It is about 10.6% denser than tap water and has a higher melting point, tasting slightly sweeter and can affect bioloigcal systems; large amounts are needed to poison humans, although it is toxic. It is produced using the Girdler sulfide process, and the usages of Heavy Water is mainly for nuclear science; can be used as coolant due to its moderating properties and insufficient thermal properties, therefore leading to using liquid sodium or lead as a coolant.
The fuel is either metal or ceramic, with metal claddingCladdingCladding is the thin walled metal tube that composes the outside of a fuel rod.
It's purpose is to prevent corrosion of the fuel by the coolant & release of fission contents into the coolant. Although Zirconium alloy is common, aluminum and stainless steel is also used.
Cladding Types
Zirconium alloy has been used for so long due to it's properties being very good for nuclear reactors.
* New research suggests that there is an alternative - SiGA cladding. This cladding is made from silicon car - unlike a PWR reactorPWR reactorThis reactor is a PWR reactor - a pressurized water reactor. This is a specific type of Nuclear Reactor--in that it is pressurized water. This is also the most common type of reactor used and produced.
The fuel rods are pressurized with helium, and the fission gas products result in more stability; as fuel "burns" in the reactor, the density increases resulting in small voids developing. Helium pressurization is necessary as these voids can cause potential rupture of fuel rods. Furthermore, the's ZirconiumZirconiumZirconium is a metal used in reactor cladding
Zirconium has excellent heat transfer properties and allows for efficient heat transfer. However, it has a negative reaction called Zircaloy hydriding, where zirconium and hydrogen combine for form zirconium hydride, embrittling reactor cladding and resulting in perforations. cladding. Liquids metals are used widely due to their heat transfer properties, and sodium cooled fast reactors are the most common design:
Because Sodium reacts violently with water, SFRs require a intermediate heat exchanger between RPVRPVReactor Pressure Vessel - contains all of the reactor heat.
In BWR reactors, the RPV contains the reactor core - basically the entirety of the main reactor assembly. The RPV is designed to withstand a very large amount of force considering that in a BWR it must withstand the pressure that both it operates at and at emergency designs -- this is due to the fact that in most designs, the RPV isn't considered to be at major risk: even during a major LOCA the RPV is considered to be at healthy condi and Steam Turbines. This requires much experience, leading to SFRs being slowly built.
Breeder ReactorBreeder ReactorA breeder reactor has one goal: to create more Nuclear Fuel then it uses. It is a type of Fast Neutron Reactor - and is the most common form of it (AFAIK). A breeder reactor has a nuclear conversion ratio that is greater than 1; meaning that it can create new fissile material faster than it consumes. Mechanically, many reactor designs can become breeder reactors; a PHWR Reactor have a ratio of .8, and many Light Water reactors have one of .6; changes in reactor design can increase the conversio
A breeder reactor is a specific configuration of a fast reactor (but not exclusive) - neutrons can breed more fuel from non-fissionable isotopes such as an absorbtion reactor on u-238, where p-239 from non-fissionable uranium 238 is produced, with a breeding ratio. The term breeder in general refers to configurations with a breeding ratio greater then 1