A nuclear reactor
is an apparatus in which nuclear reaction takes place for different industrial purposes. In this apparatus, the nuclear fuel (U235
) is gone through nuclear fission process. The nuclear fission process is not stable process. It is a commutative process. A nuclear reaction
is a nuclear fission. When Uranium nuclei are bombarded with slow moving neutrons, the nuclei are split and emit huge heat energy and more neutrons.
These newly created neutrons are called fission neutrons and these also take part in nuclear fission process and create more heat and fission neutrons. This reaction is referred as a chain reaction. The uncontrolled chain reaction is explosive.
A chain reaction is started after the commencement of initial nuclear fission. Due to this chain reaction, there will be huge uncontrolled realize of energy results to a dangerous explosion if the process is not properly controlled. The function of a nuclear reactor is not only giving space for the nuclear reaction, it also efficiently controls the reactions so that in addition to giving safety, the system also gives desired output energy.
There are only four main parts of a nuclear reactor.
- A cylindrical strong and robust pressure vessel,
- Fuel rods of Uranium,
- Moderator and,
- Control rods.
The cylindrical stout pressure vessel houses the fuel rods. The fuel rods constitute the fission material. These fuel rods, containing nuclear fuel, release huge energy if bombarded with slow moving neutrons. The moderators are made of the graphite material and these enclose the fuel rods.
Graphite made moderate creates a barrier between fired neutrons and fuel rod and prevent the neutrons to strike directly to the fuel rods. In this way, the moderates slow down the motion of neutrons and slow down the rate of reaction. The main component of control rods is cadmium. Cadmium is a strong absorber of neutrons. These control rods are inserted into the reactor vessel and the level of insertion determines the rate of nuclear reaction. When these rods are inserted deep enough in the vessel, these absorb most of the fission neutrons. Then only very few of the fission neutrons are available for the reaction and as a result, the reaction is stopped. On the other hand, if the control rods are drawn out, after a certain level of the rods there will be sufficient neutrons become available to bombard the fuel rod to restart the nuclear reaction. The nuclear reaction creates heat energy. This heat is taken as the output of the nuclear reactor. Therefore, by controlling inward and outward movements of the cadmium controls rods, the output of the reactor is controlled. In an actual nuclear reactor
, these inward and outward movements of the control rods are not controlled manually instead these movements are fully automated and entirely depend on the load conditions of the system. The heat produced in the reactor during the reaction is carried to the heat exchanger with help of sodium metal coolants. This heat is ultimately utilized for producing steam
to rotate steam turbines. After giving up the heat to the heat exchanger, the coolant is returned to the reactor through inlet feeding pipes.