How a nuclear power station makes electricity
A nuclear power station is a thermal plant. Instead of burning fuel, it uses heat from splitting uranium atoms to make steam for a turbine.
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Pressurised-water reactor (PWR) plant. Separate primary, steam/feedwater and cooling circuits are shown; containment is cut away for teaching. Motion is slowed for inspection. Coloured overlays reveal flow through enclosed equipment; gold pulses show net electrical energy transfer, not individual electrons.
How it works
- Controlled nuclear fission
- Heat carried by coolant
- Steam production
- Turbine rotation
- Generator electricity
- Transformer and grid
A nuclear power station uses heat released when atomic nuclei split in a controlled chain reaction. Fuel transfers that heat to a coolant; the coolant’s route depends on the reactor design. In the pressurised water reactor shown here, high pressure keeps the primary cooling water liquid. It passes through steam-generator tubes, heating separate secondary water into steam. That steam expands through a turbine connected to an electrical generator.
After the turbine, a condenser removes heat and turns the steam back into water for reuse. A separate cooling system carries the rejected heat to the environment. The reactor coolant, turbine steam and cooling water therefore have distinct jobs and normally remain separate in this arrangement. Control and protection systems manage the chain reaction, while barriers contain radioactive material. Cooling remains necessary after shutdown because radioactive decay in the fuel continues to release heat.
Inside the engineering
Follow the machinery, the working fluids and the electrical connection.
Mechanical
Primary coolant pumps circulate water between the reactor vessel and steam generators. Steam drives a turbine-generator train. The condenser and feedwater pumps close the secondary water cycle; control rods are not continuously moving during steady operation.
Thermal & chemical
Fission supplies heat without combustion. Pressurised primary water transfers heat through steam-generator tubes without mixing with the secondary water. A third cooling circuit removes rejected heat at the condenser; visible cooling-tower plumes are condensed water droplets.
Electrical
A synchronous generator supplies AC power through a step-up transformer. The generating unit also needs auxiliary electrical supplies for pumps, controls and cooling. The model explains energy conversion, not the plant’s complete protection and safety systems.
Main types and variations
The 3D cutaway represents a pressurised water reactor (PWR), not every nuclear station. Reactor families differ in coolant, neutron behaviour and heat-transfer equipment. “Small modular reactor” describes size and construction approach and can overlap with several of those families.
Pressurised water reactor (PWR)
Pumps circulate pressurised water through the core and steam generators. Heat crosses the steam-generator tube walls to a separate steam circuit. A pressuriser maintains primary-system pressure, while the secondary steam drives the turbine and returns through the condenser and feedwater system.
What changes in practice
Keeping reactor coolant separate from turbine steam defines the main layout. Steam-generator tubes are both heat-transfer surfaces and an important separation barrier.
Boiling water reactor (BWR)
Water boils inside the reactor vessel. Separators and dryers remove entrained droplets before steam travels directly to the turbine. The condenser turns the exhaust steam back into water, and feedwater pumps return it to the vessel. A separate PWR-style steam generator is unnecessary.
What changes in practice
The reactor and turbine share the steam-water circuit, so this design cannot be understood by simply copying the PWR’s separate primary and secondary loops.
Pressurised heavy-water reactor (PHWR)
In a CANDU-type PHWR, fuel sits in individual pressure-tube channels. Heavy water serves as coolant and as the moderator that slows neutrons, in separate systems. The hot coolant carries heat to steam generators. Special fuelling machines can replace fuel bundles while the reactor operates.
What changes in practice
Fuel channels and online refuelling distinguish this layout from a single-vessel light-water reactor. Pressure-tube condition is a major inspection and maintenance consideration.
Gas-cooled reactors: AGR and HTGR
A circulating gas transports heat out of the core instead of liquid water. Advanced gas-cooled reactors use carbon dioxide; high-temperature gas-cooled reactor designs use helium. The recovered heat can supply electricity generation and, in suitable high-temperature designs, industrial processes that also need heat.
What changes in practice
Gas cooling changes the heat-transfer equipment and temperature requirements. These are nuclear reactors; the coolant gas is a heat carrier, not a combustion fuel.
Fast-neutron reactors
Fast reactors sustain fission using high-energy neutrons rather than first slowing them with a moderator. Different concepts use sodium, lead or gas to transport heat. The reactor’s heat still needs a power-conversion system; the word “fast” describes neutron energies, not turbine speed or start-up time.
What changes in practice
Fuel composition, coolant choice and the intended fuel cycle must be considered together. A fast reactor is not automatically a breeder in every configuration.
Small modular reactors (SMRs)
SMRs package a smaller reactor in a design intended to use modular manufacturing or construction. Some are compact water-cooled reactors; others use different coolants and reactor physics. Each still needs fuel, heat removal, power conversion, protection systems and a suitable connection to its users.
What changes in practice
“SMR” alone does not identify the coolant or steam cycle. Compare the actual design and licensing status rather than assuming all small reactors operate alike.
Worth knowing
- Nuclear stations produce very little carbon dioxide while operating.
- They usually run near full output for long periods between refuelling outages.
- Spent fuel is highly radioactive and must be stored and managed for a long time.
See real examples
The atlas includes 196 nuclear records worldwide.
Show on the mapRelated answers
Textbook references
The science on this page follows these standard engineering textbooks. See the full bibliography.
- Introduction to Nuclear EngineeringFission, neutron physics, reactor types, heat removal and radiation protection.
- Thermodynamics: An Engineering ApproachRankine steam cycles used on the secondary side of the plant.
Sources
- EIA: Nuclear power plants ↗
- US NRC: Primary and secondary steam-generator circuits ↗
- EIA: How electricity is generated ↗
Cutaways reveal enclosed equipment. Layouts, dimensions, materials and animation speeds are illustrative; this is an educational model, not a plant design or a thermodynamic simulation.