Energy Nuclear Power Station — free printable diagram

How a nuclear power station works

A nuclear power station makes electricity the same way a coal or gas station does — by boiling water into steam and using that steam to spin a turbine connected to a generator. The only difference is where the heat comes from: instead of burning a fuel, the heat is released by nuclear fission, the splitting of large atomic nuclei inside a reactor.

Fuel

Uranium, sometimes plutonium

Reaction

Nuclear fission — a large nucleus splits in two

What fission releases

Heat energy

Reactor

Where the fission reaction is contained and controlled

Control rods

Absorb neutrons — lowered in to slow the reaction, raised out to speed it up

Heat exchanger / boiler

Uses the heat to turn water into steam

Turbine and generator

Steam spins the turbine, which turns the generator

Waste

Radioactive, and needs long-term storage

• Follow the diagram as an energy pathway: fission releases heat, the heat makes steam, the steam turns a turbine, the turbine turns a generator, the generator makes electricity. Every stage after the first is identical to a fossil-fuel station.
• Fission is a chain reaction. Splitting one nucleus releases neutrons that go on to split others, so without control it would accelerate — which is exactly what the control rods are there to prevent.
• Generating electricity this way releases no carbon dioxide, which is the main argument made for it. The counter-arguments are the radioactive waste, the cost of building and decommissioning the station, and the consequences of an accident.
• The large towers release water vapour, not smoke. They are cooling towers, part of getting rid of waste heat, and the plume is condensed steam — a very common misreading of the picture.
• Fission is not fusion. Fission splits a large nucleus and is what power stations use today; fusion joins small nuclei together and is what powers the sun.
• Most station diagrams show two separate water loops, joined only at the heat exchanger: a coolant loop that carries heat out of the reactor, and a second loop whose water is turned into the steam that drives the turbine. Tracing which loop is which is a good way to check a student is reading the diagram rather than the labels.