Nuclear power plant

The operating principle of a nuclear power plant does not differ fundamentally from that of a fossil fuel-fired power station. The only difference is how the heat is produced. Nuclear power stations have a reactor, in which the fission of uranium atoms is the source of heat. ‘Conventional’ power stations produce heat by burning natural gas, coal or oil.

The heat from the reactor core is released into water circulating in a closed circuit along the nuclear fuel rods. This is called the primary circuit. The water in the primary circuit has an average temperature of 300 °C.  In a pressurised-water reactor, water cannot boil because it is under pressure. The hot water in the primary sector in turn releases heat to a second closed circuit known as the secondary circuit. They are hermetically sealed from each other. The heat exchange takes place in a steam generator, a large cylindrical heat exchanger consisting of thousands of tubes. The heat converts the water in the secondary circuit into steam. The steam produced in the secondary circuit expands across multiple turbine components, forcing it to turn. A generator connected to the turbine converts this kinetic energy into electricity, which is then injected into the high-voltage grid.

The steam used by the turbines is cooled in a condenser, where it is once again converted into water after coming into contact with thousands of tubes containing cooling water from the third circuit. The water can then return to the steam generator, where it is once again heated to the steam state.


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