Nuclear power is one of the safest ways to generate electricity, at about 0.03 deaths per terawatt-hour once Chernobyl and Fukushima are counted in, according to an analysis by Our World in Data of historical accidents and pollution deaths. That rate sits close to wind and solar and far below coal or oil. The number spans the industry’s full history, from routine operation through Chernobyl and Fukushima.
Nuclear waste still has to go somewhere. A bad accident costs far more than the death count alone shows.
What deaths per terawatt-hour measures
One terawatt-hour is roughly what a mid-sized country’s grid delivers in a few hours, or what a single large power plant produces in a year or two. Anil Markandya and Paul Wilkinson built the foundational version of this comparison, publishing a life-cycle study of electricity and health in The Lancet in 2007. Benjamin Sovacool separately compiled a database of 279 major energy accidents between 1907 and 2007. The comparison below draws on both lines of research, plus a newer accident count.
By that tally, coal kills about 24.6 people per terawatt-hour and oil about 18.4, almost entirely from the sulfur dioxide and fine particulates that combustion pushes into the air year after year. Gas comes in at 2.8, and nuclear is lower still.
| Source | Deaths per TWh | Main driver |
|---|---|---|
| Coal | 24.6 | Air pollution |
| Oil | 18.4 | Air pollution |
| Gas | 2.8 | Air pollution, some accidents |
| Hydropower | 1.3 | Dam failures, mostly one event |
| Nuclear | 0.03 | Chernobyl and Fukushima |
| Wind | 0.04 | Construction and maintenance accidents |
| Solar | 0.02 | Installation accidents |
Source: Our World in Data, “What are the safest and cleanest sources of energy?”, combining Markandya and Wilkinson (2007) with a database of historical energy accidents.
Hydropower’s low average hides a single outlier. Nearly all of that death toll traces to one event, the Banqiao Dam failure in China in 1975. The same analysis puts the toll at an estimated 171,000 people.
Estimates for that single event vary widely. Chinese authorities have cited 26,000 confirmed dead, versus a Human Rights Watch estimate of 230,000 once deaths from the disease and famine that followed the flood get counted in.
Chernobyl’s death toll
The Chernobyl reactor exploded in April 1986, in what is now Ukraine. By 2005, fewer than 50 deaths had been directly attributed to radiation exposure, almost all of them rescue workers who took the highest doses in the accident’s first hours and months, according to the World Health Organization.
The WHO’s 2005 assessment also projected up to 4,000 eventual deaths from radiation-induced cancer among the roughly 600,000 people most exposed. The agency put that at an increase of about 3% over the cancer rate that group would see anyway, too small a rise to observe directly against the background rate.
Radioactive iodine released by the fire also drove up thyroid cancer among people who were children in the contaminated region at the time. By 2015, close to 20,000 thyroid cancer cases had been registered in the affected areas, and the United Nations’ scientific committee on radiation attributed about one in four of them to the accident.
The reactor involved was an RBMK design that lacked the containment structure standard on Western reactors and had a control-rod flaw that, on an emergency shutdown, briefly added reactivity to the bottom of the core instead of cutting it. The World Nuclear Association treats that flaw as central to why the accident escalated the way it did.
Fukushima’s death toll
The Fukushima Daiichi meltdown, in March 2011, didn’t kill anyone through direct radiation exposure. One plant worker died in 2018 of lung cancer that Japan’s government attributed to his radiation exposure on the job, the only radiation-linked death the accident has produced.
The rest of the deaths run on a separate count from that one radiation death. More than 100,000 people were moved out of the area as a precaution, on top of about 19,500 people killed by the earthquake and tsunami itself. Japan has certified 2,313 deaths as disaster-related among Fukushima evacuees, most from disrupted hospital care and the strain of relocating elderly and hospitalized patients during the evacuation.
About 27,000 people from Fukushima were still living as evacuees as of November 2025, 14 years on.
Nuclear waste, in volumes
A reactor generating 1,000 megawatts produces about 3 cubic meters of high-level waste a year when its fuel is reprocessed, against roughly 300,000 tonnes of ash from a coal plant generating a similar amount of power.
High-level waste and used fuel together make up less than 3% of nuclear waste by volume but hold 95% of its radioactivity, while intermediate-level waste adds another 7% and the remaining 90% is only lightly contaminated tools and clothing, the association says.
About 97% of used fuel can be recycled into new fuel, most of it reusable uranium. What can’t be recycled is vitrified, mixed into glass and sealed inside metal canisters, then buried in deep geological repositories, an approach France, Japan, Belgium and Russia already use for permanent disposal.
Radiation risk fades with time
Radioactivity isn’t a fixed hazard. It decays on a known schedule. Used fuel’s radioactivity falls to about a thousandth of its initial level after 40 years, the World Nuclear Association says.
The same group states that nuclear waste has never caused harm to people since the civil industry began, a claim that holds up against decades of operating records. That’s a claim about the industry’s history, though, not a guarantee about storage arrangements holding for the thousands of years some of this material stays hazardous.
Reactor accidents make headlines. Fuel handling and containment integrity are the routine work that keeps the accident rate low, and it’s not the part of the job the public usually hears about.
What this number does and doesn’t tell you
Deaths per terawatt-hour answers one question well. Historically, which sources of electricity have killed the fewest people relative to how much power they’ve produced? On that question, nuclear does about as well as wind and solar, and far better than any fossil fuel.
It answers a narrower question than people often assume. It’s a global historical average built mostly from twentieth-century reactors and two accidents. It doesn’t forecast what a reactor built under current safety regulation would do. It also treats a death from evacuation stress the same as a death from radiation exposure, which is fair for counting purposes but blurs how differently those two causes of death happen.
The number says nothing about what a bad accident costs. Estimates from the 1990s put Chernobyl’s cleanup and economic costs at hundreds of billions of dollars over two decades, the World Health Organization says. Fukushima evacuees alone had received about 9.7 trillion yen in compensation as of January 2021. Costs like that don’t show up in a death count, and they run far higher for nuclear than for the low-mortality alternatives it gets grouped with.
None of that changes the mortality data. Being statistically safe and having no downsides worth discussing are two different claims, and only the first one holds up here. In 2024, nuclear supplied about 9% of the world’s electricity, or 2,667 terawatt-hours. China alone had 28 new reactors under construction as of mid-2025, the fastest pace of any country and a bet that the safety record and the cost keep both moving in nuclear’s favor.
Germany bet the other way. It phased out nuclear power entirely and leaned more on coal to fill the gap, a choice the death-rate data doesn’t settle either way. That’s a call about cost and politics. This number was never built to answer it.
