We know that, a lot of energy is produced during the nuclear fission of Uranium atom.We get this energy in heat form. So, this is heat energy. Some mutually connected systems are needed to transform this heat energy into electric power. All these systems together are known as energy blocks or units.
Now, let's see how electricity is produced in atomic blocks. The atomic fuel is situated in atomic reactor's active zone. The atomic fuel is loaded in the reactor as heat emitter element. These heat emitter elements are UO2 tablets filled, thin walled, long, metal tubes.These fuel tablets are made from fissionable Uranium235 rich UO2 .
As soon as the atomic reactor is turned on, chain reactions are formed in the active zone. This process divides the Uranium 235 nucleus in two parts by the hit of neutrons. At the same time, a lot of heat is also produced. As a result of the nuclear fission of uranium, some(2/3) neutrons become free and hit the neighboring uranium nucleus. Thus using one neutron, we are getting 2 or 3 new neutrons which are able to break another nucleus. more neutrons become free from the broken nucleus, which breaks another nucleus and the chain reaction goes on.
The chain reaction is required to be controlled. That's why some of the neutrons are exploited by boron rod. If these rods are completely entered in the active zone, then the chain reaction won't be able to start because it will exploit almost all the free neutrons.
When these rods are partly pulled up from the active zone, then the chain reaction starts again. So, by pulling the rods up and entering them in the zone, the reaction is controlled.
To bring out the heat energy produced from atomic fuel, water is flowed with the help of a powerful pump in the active zone of the reactor. The water is boiled with the heat and creates vapour. Thia vapour flows through the steam turbine and oscillates the blades of the turbine. At the same time the turbine's axis rod which is joined with the blades is also oscillated. This axis rod and the generator's rotor axis rod is the same. So the rotor also starts to oscillate. As a result electricity is produced in the coil of the generator.