Nuclear fission reactors: Impact on the biosphere
Rare disasters, long-lived waste and remarkably few deaths
What this tab covers Effects on human, animal, plant, fungal and microbial life and on whole ecosystems: in the short term (construction and early years), medium term (operating life) and long term (decommissioning and legacy).In normal operation nuclear power has among the lowest death rates and emissions of any source. Its distinctive risks are rare severe accidents, radioactive waste that must be isolated for very long periods, and the impacts of uranium mining and cooling-water use.
Deaths per TWh (accidents and pollution, including Chernobyl and Fukushima) 0.03 (433 Chernobyl and 2,314 Fukushima deaths over 96,876 TWh generated 1965-2021 give 0.028, calculated)17 Life-cycle greenhouse gases 5.1-6.4 g CO2e/kWh11 Fukushima evacuation-related deaths 2,31318 Spent fuel generated worldwide (1954 to end 2016) about 390,000 tonnes19Effects over time
| Life affected | Short term | Medium term | Long term |
|---|---|---|---|
| Humans1819 | Construction-site and uranium-mining accidents | Chernobyl: 30 early deaths, eventual thyroid cancer deaths estimated at 96-385; Fukushima: 1 radiation death and 2,313 evacuation-related deaths, more than 160,000 people moved | Spent fuel must be isolated for very long periods; in October 2026 Finland granted the world's first operating licence for a deep geological repository (Onkalo) |
| Animals16 | Little evidence of effect beyond construction disturbance | Fish drawn into cooling intakes at once-through plants, which withdraw about 44,350 gallons per MWh | Little evidence of effect |
| Plants15 | Small site areas cleared | Little evidence of effect in normal operation | Little evidence of effect |
| Fungi and soil life15 | Little evidence of effect | Little evidence of effect | Little evidence of effect |
| Ecosystems819 | Uranium mining disturbs land, though 55% of uranium is now produced by in situ leaching without digging a pit | Warm water discharged to rivers or the sea | About 390,000 tonnes of spent fuel generated by end 2016, about a third reprocessed |
How the effects are reduced
Modern reactor designs add passive cooling and containment, and post-Fukushima reviews strengthened back-up power and flood defences. The large indirect toll at Fukushima came from evacuation, so planning for proportionate, short evacuations reduces harm. Spent fuel is stored in pools and dry casks, with deep geological disposal most advanced in Finland, and well advanced in Sweden, France, Canada and Switzerland. Cooling towers and intake screens reduce fish losses; in situ leaching reduces mining waste but needs groundwater restoration.
Sources
- World Uranium Mining Production World Nuclear Association, 2025
- Carbon neutrality in the UNECE region: integrated life-cycle assessment of electricity sources (ECE/ENERGY/141) United Nations Economic Commission for Europe, 2022
- How does the land use of different electricity sources compare? Our World in Data, 2022
- Operational water consumption and withdrawal factors for electricity generating technologies (Macknick et al., Environmental Research Letters 7, 045802) IOP Publishing (via OpenEI), 2012
- What are the safest and cleanest sources of energy? Our World in Data, 2024
- What was the death toll from Chernobyl and Fukushima? Our World in Data, 2022
- Status and Trends in Spent Fuel and Radioactive Waste Management International Atomic Energy Agency, 2022