Nuclear fission reactors
Reactors that split uranium or thorium atoms to make heat for steam turbines.
Capture · Fossil and nuclear · No. 46
- Capture
- Output: Heat → electricity
Today's reactors use less than 1% of the energy locked in mined uranium, yet still make about 9% of world electricity.
Chart: Illustration: Nuclear fission reactors
Where it comes from
Chart: Map of where it comes from
Uranium is mined or, for 55% of output, dissolved in place by solutions pumped through the ore. Centrifuges then enrich it from 0.7% U-235 to 3-5% for light-water reactors.
Three things to know
- Fukushima's radiation killed one person, while the evacuation was linked to 2,313 deaths.
- Life-cycle emissions are only about 5.1-6.4 g CO2e/kWh, among the lowest of any electricity source.
- In October 2026 Finland granted Onkalo the world's first operating licence for a deep geological repository for spent fuel.
The journey
- 1 Uranium oreMined, or dissolved in place underground
- 2 EnrichmentCentrifuges raise U-235 to 3-5%
- 3 FuelOxide pellets sealed in metal tubes
- 4 ReactorSplitting atoms boils water
- 5 TurbineSteam makes electricity at 33-37%
- 6 Spent fuelCooled, stored, sometimes reprocessed