A nuclear reactor is a device of initiate and control a sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation.
When a slow moving neutrons attacks on the nucleus of U-235, its nucleus splits into Barium and Karypton by releasing a large amount of energy with 3-neutrons.
- 92U235+0n1 ———–> 56Ba142 +36Kr91+ 30n1 + Energy
The fissional material is used in the reactor is called as fuel. The commonly used fuels are uranium, plutonium or thorium. It can be U-235, U-238, U-236, Th-232. Uranium is mostly preferred as it.
Only neutrons of a fairly low speed should be used to have controlled chain reaction. To slow down the speed fast moving neutrons produced during the fission process, moderators are used. Moderators reduces the speed of the netron by absorbing its energy but not absorb neutron.
Graphite, heavy water , beryllium are common moderators.
- Control rods:
These rods absorb the extra neutrons and stop the chain reaction to proceed further. These rods are made up of steel containing a high percentage of material like cadmium or boron which can absorb extra neutrons. When control rods are completely inserted into the moderator block then all the neutrons is absorbed and reaction comes to halt.
Shielding prevent radiations to reach outside the reactor. Lead blocks and concrete enclosure that is strong enough of several meters thickness are used for shielding.
The coolant is a substance in a pipe to the steam generator where water is boiled. This is where heat exchange process occurs. Heat is absorbed by the coolant that is produced in the reactor. Typical coolants are: water, liquid sodium or carbondioxide gas.
Steam produced in the boiler is now passes to a turbine. The force of the steam jet causes the turbine move and the change in magnetic flux cause electricity. This is transmitted to substations for distribution of electric power.