Fast Breeder Reactors (FBR) Power Plant

When uranium U-235 is fissioned by slow neutrons it produces heat and an additional neutron. In case a fertile material like U-238 is kept in the same reactor surrounding the core of U-235, the fast moving additional neutron is absorbed by U-238 and converts it into plutonium (Pu-239), a fissile material. This man made fuel Pu-239 can be used for further fission.
Therefore, these type of reactors are important since they not only produce heat but also produce more secondary fissile fuels like plutonium more than fuel consumed in the reactor.
This is known as Breeding.
Similarly, Thorium (Th-232) can be converted into U-233 which is also a secondary fissile material.
Since, India has massive reserves of thorium and limited resources of uranium, development of these fast breed reactors are important.
As Fast breeder reactor is shown in figure below.
Fast Breeder Reactor Power plant | enggarena.net
Fast Breeder Reactor Power Plant
The enriched uranium U-235 or plutonium Pu-239 is kept without a moderator in the reactor core surrounded by a thick blanket of depleted U-238.
One additional neutron available from fission of U-235 is used to convert U-238 or Th-232 into U-233 as secondary fuels.
As in case of sodium graphite reactor, this reactor also uses two liquid metal coolants in which sodium is used as primary coolant and sodium potassium as secondary coolant.
In fast breeder reactors, the neutron shielding is provided by the use of boron or graphite. In order to protect against gamma radiations, a shield is provided made of lead or concrete or of other materials.

Advantages of Fast Breeder Reactor :

1. Moderator is not required.
2. Absorption of neutron is slow.
3. Secondary fissile material by breeding are obtained.
4. Small core is sufficient since it gives high power density as compared to other reactors.

Disadvantages of Fast Breeder Reactor :

1. Requires enriched uranium as fuel.
2. Neutron flux is high at the center of the core.
3. Thick shielding is necessary against radioactive radiations in primary and secondary circuits as in case of sodium graphite reactors.
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Sujit Kadus

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