In most of the methods of generating electricity in the simplest terms, you need a rotating wheel. You need movement for Kinetic Energy. In hydroelectricity, when the water falls from above, it moves the wheels, and creates energy. In wind energy, the wind moves the turbine, which produces energy once it starts rotating. In thermal powerplants, that uses coal to generate electricity steam is released by burring the coals, and the steam later moves the wheels. The kinetic energy is thus generated.
Even in case of nuclear energy, the wheel is moved by steam. But to make that steam, water has to be heated up first, whereas in thermal energy, coal heats up the water, in nuclear energy, the nuclear reactions taking place heats up the water.
Look at this diagram from a school book. You don’t need to get into the details, you can see a turbine that is rotated by steam. And the steam is generated because the nuclear reaction heats up the water. This water acts as a coolant as well. To prevent overheating around the reactor, the constant supply of water is a must.
In the Chernobyl plant, the water came from a nearby man-made water reserve. There was a river beside it too. It is important to have a consistent supply of water at all times. For this, the water pumps pushing the water into the pipes, should be working non-stop. But what happens in case of a power cut?
