Nuclear fission reactors: Overview
Splitting atoms for steady, very low-carbon electricity
What this tile covers Reactors that split uranium or thorium atoms to make heat for steam turbines. Share of use 5.2% share of world energy supply (2024)Share of world total energy supply captured or extracted by each method, 2024 (latest year where noted). Denominator is the Energy Institute Statistical Review 2025 total of 592.2 EJ (physical energy content method); electricity from wind, solar, hydro and geothermal is counted at output, nuclear at reactor heat. Heat and biomass flows outside EI's total are set against the same 592.2 EJ. Nuclear 30.74 EJ, counted as reactor heat input, of 592.2 EJ (calculated). Source: Statistical Review of World Energy 2025 (74th edition), Energy Institute.
Key facts
| Output | Heat → electricity |
| Chain | Nuclear → heat → steam → mechanical → electrical |
Included from the reference tables
- Light-water reactors (pressurised, boiling)
- Heavy-water reactors (CANDU, India's PHWRs)
- Fast breeder reactors and thorium fuel cycles
- SMRs, microreactors, molten salt and high-temperature gas reactors
- Naval reactors
- Uranium mining, in-situ leaching and enrichment
Linked to the material world
U UraniumZr ZirconiumHf HafniumH₂O WaterAlso in Fossil and nuclear
CM Coal miningOGw Conventional oil and gas productionUOG Unconventional oil and gasExplore paths from here
More on this tile in the tabs above: efficiency, techniques, resources and labour, impact on the biosphere.