Nuclear power plants generate electric power from fission in nuclear reactors.
The principle shown here is that of a modern pressurised water reactor (PWR) with two separate cycles: the reactor cooling cycle (primary cycle) and the feedwater-steam cycle (secondary cycle).
Nuclear fission produces heat, which is transferred to a coolant medium, which is thus heated. The coolant is usually water. Heating the water produces steam, which in turn drives a steam turbine.
Most nuclear power plants consist of several units, which generate electricity independently of one another.
Various types of reactor are used in nuclear power plants, with different nuclear fuels, cooling cycles and neutron moderators.
Each power unit of a nuclear plant has a capacity of 500 to 1500 megawatts.