|Fig. 1: Integral Fast Reactor Design. (Source: Wikimedia Commons)|
The Integral Fast Reactor (IFR) is a design for nuclear reactors that utilizes fast neutrons and a liquid metal cooling system. The four main components of an IFR, which is also known as a breeder reactor, are a liquid sodium cooling system, a pool-type reactor configuration, a metallic fuel, and an integral fuel cycle.  While it is not a reactor type that is in widespread use, the Clinton Administration cancelled the IFR program and the Congress terminated its funding in 1994.  This has caused the IFR to become somewhat of a political device, and therefore in this report we will focus on the basics of the IFR from a scientific perspective.
The liquid sodium cooling system is ideal from IFRs because it does not react chemically, and unlike LWRs it does not need to be kept under intense pressures. The IFR is designed with inherent processes to bring the core to a safe shut down.  The danger of course is that liquid sodium reacts explosively when exposed to air or water, but on the positive side the lack of a need to keep it under pressure means there is no need for pressure vessels, reducing the risk of a catastrophic pressure breach. The pool-type reactor configuration allows for large amounts of heat to be absorbed after shutdown, this is the primary source of coolant and can be seen in Fig. 1.  The use of metal as a fuel source also helps with the inherent safety of the IFR because metal has a higher heat capacity, which enhances the axial and radial leakage.  The integral fuel cycle is made possible my on-site pyroprocessing, which uses the waste produced and re-purposes it as fuel which can then be used in the IFR.
|Fig. 2: The Russian BN-600 fast breeder reactor. (Source: Wikimedia Commons.|
What makes IFRs unique is the speed at which the neutrons move, this is made possible by the fact that they are not slowed by water, as they are in Light Water Reactors, because of this the fast neutrons can split the Uranium atoms more quickly, continuing the reaction.
What makes IFRs really appealing is the fact that not only can they get almost all of the energy out of Uranium, which results in less waste overall, but the effective lifetime of the waste is reduced from hundreds of thousands of years to a few hundred years.  IFRs are also able to run on the nuclear waste of other reactors, as well as plutonium from weapons, similar to the Russian BN-600 reactor seen in Fig. 2, and the newer version the BN-800 (image unavailable).
While a complex topic to understand due to the shroud of political agendas that surround IFRs and breeders, when you get down to the basics of what makes IFRs unique, you can see that they have several advantages over LWRs, and if used in conjunction with Generation III reactors could do a lot to not only reduce nuclear waste, but make it more efficient overall.
© Craig Jones. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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