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Nuclear Energy

As the world attempts to transition its energy systems away from fossil fuels towards low-carbon sources of energy, we have a range of energy options: renewable energy technologies such as hydropower, wind and solar, but also nuclear power. Nuclear energy and renewable technologies typically emit very little CO2 per unit of energy production, and are also much better than fossil fuels in limiting levels of local air pollution.

But whilst some countries are investing heavily in increasing their nuclear energy supply, others are taking their plants offline. The role that nuclear energy plays in the energy system is therefore very specific to the given country.

How much of our energy comes from nuclear power? How is its role changing over time? In this article we look at levels and changes in nuclear energy generation across the world, and its safety record in comparison to other sources of energy.

Nuclear energy generation

Global generation of nuclear energy

Nuclear energy – alongside hydropower – is one of our oldest low-carbon energy technologies.

Nuclear power generation has been around since the 1960s, but saw massive growth globally in the 1970s, 80s and 90s. In the interactive chart shown we see how global nuclear generation has changed over the past half-century.

Following fast growth during the 1970s to 1990s, global generation has slowed significantly. In fact, we see a sharp dip in nuclear output following the Fukushima tsunami in Japan in 2011 [we look at the impacts of this disaster later in this article], as countries took plants offline due to safety concerns.

But we also see that in recent years, production has once again increased.

Nuclear energy generation by country

The global trend in nuclear energy generation masks the large differences in what role it plays at the country level.

Some countries get no energy at all from nuclear – or are aiming to eliminate it completely – whilst others get the majority of their power from it.

This interactive chart shows the amount of nuclear energy generated by country. We see that France, the USA, China, Russia and Canada all produce relatively large amounts of nuclear power.

Two tips on how you can interact with this chart

  • View the data for any country as a line chart: click on any country to see its change over time, or by using the ‘CHART’ tab at the bottom.
  • Add any other country to the line chart: click on the Add country button to compare with any other country.

What share of primary energy comes from nuclear?

We previously looked nuclear output in terms of energy units – how much each country produces in terawatt-hours. But to understand how large of a role nuclear plays in the energy system we need to put this in perspective of total energy consumption.

This interactive chart shows the share of primary energy that comes from nuclear sources.

Note that this data is based on primary energy calculated by the ‘substitution method’ which attempts to correct for the inefficiencies in fossil fuel production. It does this by converting non-fossil fuel sources to their ‘input equivalents’: the amount of primary energy that would be required to produce the same amount of energy if it came from fossil fuels. We look at this adjustment in more detail here.

In 2019, just over 4% of global primary energy came from nuclear power.

Note that this is based on nuclear energy’s share in the energy mix. Energy consumption represents the sum of electricity, transport and heating. We look at the electricity mix below.

What share of electricity comes from nuclear?

In the sections above we looked at the role of nuclear in the total energy mix. This includes not only electricity, but also transport and heating. Electricity forms only one component of energy consumption.

Since transport and heating tend to be harder to decarbonize – they are more reliant on oil and gas – nuclear and renewables tend to have a higher share in the electricity mix versus the total energy mix.

This interactive chart shows the share of electricity that comes from nuclear sources.

Globally, around 10% of our electricity comes from nuclear. But some countries rely on it heavily: it provides more than 70% of electricity in France, and more than 40% in Sweden.

What are the safest sources of energy?

At the start of the Industrial Revolution, it was discovered that the energy in fossil fuels can be unlocked to make work more productive. This finding transformed human development: for most of history, living conditions across the world were equally poor. This began to change, rapidly, once we learnt how to use coal, oil, and gas. In more recent years, we have also gained access to modern renewables and nuclear power.

The increasing availability of cheap energy has been integral to the progress we’ve seen over the past few centuries. Energy access is one of the fundamental driving forces of development. The United Nations says that “energy is central to nearly every major challenge and opportunity the world faces today.”

But energy production has downsides as well as benefits. There are three main categories:

  • Air pollution: An estimated five million people die prematurely every year as a result of air pollution; fossil fuels and biomass burning are responsible for most of those deaths. 
  • Accidents: As well as deaths caused by the byproducts of energy production, people die in accidents in supply chains, whether in the mining of coal, uranium or rare metals; oil and gas extraction; the transport of raw materials and infrastructure; construction; or their deployment. 
  • Greenhouse gas emissions: Perhaps the most widely discussed downside is the greenhouse gases emitted by energy production, which are a key driver of climate change. 

All energy sources have negative effects. But they differ enormously in the size of those effects. That difference can be easily summed up: by all metrics, fossil fuels are the dirtiest and most dangerous, while nuclear and modern renewable energy sources are vastly safer and cleaner.

From the perspectives of both human health and climate change, it matters less whether we use nuclear power or renewable energy, and more that we change to one or both of them rather than fossil fuels.

Nuclear power is far, far safer than fossil fuels, contrary to public belief

For most of the past 50 years, our energy systems have been dominated by fossil fuels, traditional biomass, hydropower and nuclear energy.1

In the future we expect renewable energy sources to contribute a rising share of total energy, but before we take a closer look at how renewables compare,  let’s first see how fossil fuels stack up against nuclear energy in terms of safety.

Anil Markandya and Paul Wilkinson (2007) published an analysis in the medical journal The Lancet, which compared the death rates from the major energy sources.2 In this study they considered deaths from accidents, such as the Chernobyl nuclear disaster, occupational accidents in mining or power plant operations, and premature deaths from air pollution.3 

This study was published in 2007, before the 2011 Fukushima Daiichi nuclear disaster in Japan. You might assume that the figures from this analysis therefore understate the death toll from nuclear energy, but in fact the opposite is true. Later in this article we look at a more recent study on the safety of low-carbon energy sources, published in 2016 which includes Fukushima impacts, and in fact reports a lower death rate than Markandya and Wilkinson (2007).4 There were no direct deaths from the Fukushima Daiichi disaster. The official death toll was 573 people, all of which were premature deaths from evacuation and displacement of populations in the surrounding area.5 In 2018, the Japanese government reported that one worker has since died from lung cancer as a result of exposure from the event.

To compare the safety of different energy sources, the researchers compared the number of deaths per unit of energy that is produced by them.6 In the visualization we see the safety comparison of fossil fuels, nuclear and biomass, measured as the number of deaths per terawatt-hour of energy production. One terawatt-hour of energy is about the same as the annual energy consumption of 27,000 citizens in the European Union.7

Nuclear energy is by far the safest energy source in this comparison – it results in more than 442 times fewer deaths than the ‘dirtiest’ forms of coal; 330 times fewer than coal; 250 times less than oil; and 38 times fewer than gas. To be clear: the figures in this analysis was based on energy production in Europe where anti-pollution regulation and technologies are already well ahead of many countries in the world;  in this case the death rate from fossil fuels may even be understated.

Let’s put this into the context of the 27,000 Europeans that one terawatt-hour would provide for. Here we are taking a very simplistic example, but imagine we have a village of 27,000 people.8 If they produced all of their energy from coal, we’d expect 25 people to die prematurely every year as a result (most from the impacts of air pollution). If they generated their energy from oil we’d expect 18 to die every year; and 3 to die if they relied on natural gas. 

If they got their energy from nuclear power, in most years there would be no deaths. In fact, it would take at least 14 years before you would expect a single death. It may even be the case that this figure is an overestimate – later in the article we look at a more recent analysis of nuclear safety which suggests this is closer to one death every 100 years.

Fossil fuels have therefore killed many more people than nuclear energy. 

In many countries, however, public opinion on nuclear energy is very negative and, as a consequence, policy decisions have in some places turned harshly against it. 

In the wake of the 2011 Fukushima nuclear disaster, Germany announced plans to phase out nuclear power generation: over the period from 2011 to 2017 it shut down 10 of its 17 nuclear facilities, and plans to close the remaining reactors in 2022.9

These policy decisions can cost lives. In a study published in the journal Environmental Science and Technology, Pushker Kharecha and James Hansen (2013) reversed the conventional question of ‘how many people have died from nuclear power?’ into ‘how many lives has nuclear power saved?’.10 They analysed how many additional people would have died over the period from 1971 to 2009 if nuclear energy had been replaced by fossil fuels. The human cost would have depended on the mix of fossil fuels used to replace nuclear – more would have died if more coal was used than oil or gas – but they estimate an average figure of two million lives saved.11

Replacing nuclear energy with fossil fuels kills people. This is likely to be the case in the recent example of Germany. Most of Germany’s energy deficit from scrapping nuclear was filled by increased coal production – the most polluting source with the largest health impacts. Analysis by Stephen Jarvis, Olivier Deschenes, and Akshaya Jha (2020) estimates that Germany’s nuclear phase-out has come at the cost of more than 1,100 additional deaths each year as a result of air pollution.12 Its plans to make its energy systems safer have done exactly the opposite.

Modern renewables are about as safe as nuclear energy

Renewable energy sources will in future make up an increasing share of energy supply. How does the safety of renewable energy compare? 

Most of us have heard stories of hydropower dams flooding; people falling from roofs when installing solar panels; or wind turbines collapsing. And it’s true, these events happen. But just how common are they? Are the safety concerns about renewable energy exaggerated?

Benjamin Sovacool and colleagues (2016) investigated the safety of low-carbon energy sources in a study published in the Journal of Cleaner Production.13 In this analysis the authors compiled a database of as many energy accidents as possible over the period from 1950 to 2014 based on an extensive search of academic databases (including ScienceDirect and EBSCO host) and news reports via Google.14 The full list of accidents is made available in the underlying study; in the results below the authors compare death rates over the period from 1990 to 2013 only.

In the visualization I have combined the two studies described above so we can compare fossil fuels, nuclear and renewable energy. Again, death rates are given per unit of energy to allow a comparison. If you want to compare only low-carbon energy sources, you can find this data here.

You will notice two values for both nuclear and biomass – these represent the slightly different estimates from the two different studies: the earlier work of Markandya and Wilkinson (2007) and recent analysis by Sovacool et al. (2016).  I explain why these figures differ, and also how deaths from nuclear energy are estimated in the dropdown box at the end of this post.

We see a massive difference in death rates from fossil fuels versus nuclear and modern renewable technologies. Nuclear and renewable sources are similarly safe: in the range of 0.005 to 0.07 deaths per TWh. Both nuclear and renewable energy sources have death rates hundreds of times lower than coal and oil, and are tens to hundreds of times safer than gas.

This conclusion holds true regardless of whether you choose the higher (conservative) or lower death rate for nuclear energy. It is comparable to renewable energy technologies in both cases.

Let’s again put this into the context of our town of 27,000 EU citizens, who would collectively consume around one terawatt-hour of energy a year. These are the impacts if they got all of their energy from a given source:

  • Coal: 25 people would die prematurely every year;
  • Oil:  18 people would die prematurely every year;
  • Gas: 3 people would die prematurely every year;
  • Nuclear: it would take between 14 and 100 years before someone died;
  • Wind: 29 years before someone died;
  • Hydropower or solar: 42 years before someone died;
  • Solar: 53 years before someone died.

As well as being safe, modern renewables and nuclear energy are both extremely low-carbon

So far we’ve only considered the short-term health and social impacts of these energy sources. But we should also take into consideration their potential for future, longer-term impacts in their contribution to climate change.

The good news is that the safest sources are those which are low-carbon.

In the visualization I have plotted the death rates per unit energy data we looked at previously (on the y-axis) versus each source’s greenhouse gas emissions per energy unit (on the x-axis).

This measure of greenhouse gas emissions considers the total carbon footprint over the full lifecycle; figures for renewable technologies, for example, take into consideration the footprint of the raw materials, transport and their construction. I have adopted these figures as reported in the IPCC’s 5th Assessment Report (AR5), and more recent life-cycle figures by Pehl et al. (2017) which look at the emissions intensities of technologies in ‘2°C-compatible’ energy transitions to 2050.15,16,17

The size of each bubble represents its share of global primary energy production in 2018 (including traditional biomass in the total).18

There are few trade-offs here – the safer energy sources are also the least polluting. Coal performs poorly on both metrics: it has severe health costs in the form of air pollution, and emits large quantities of greenhouse gas emissions per unit of energy. Oil, then gas, are better than coal, but are still much worse than nuclear and renewables on both counts.

Nuclear, wind, hydropower and solar energy all cluster in the bottom-left of the chart. They are all safe, low-carbon options. But they still account for a very small share of global energy consumption – less than 10% of primary energy – as we see from the bubble size. 

There is fierce debate about which low-carbon energy technologies we should pursue. And there are of course other aspects to consider, such as cost, construction times, and location-specific resource availability. But on the basis of human health, safety and carbon footprint, nuclear and modern renewables are both winners. A number of studies have found the same: there are large co-benefits for human health and safety in transitioning away from fossil fuels, regardless of whether you replace them with nuclear or renewables.19

Fossil fuels are killing millions of people every year, and endanger many more from the future risks of climate change.  We must shift away from them, drawing on all of our available options to do so.

Safest source of energy

Why do biomass and nuclear estimates vary? How are nuclear deaths calculated?

What was the death toll from Chernobyl and Fukushima?

When it comes to the safety of nuclear energy, discussion often quickly turns towards the nuclear accidents at Chernobyl in Ukraine (1986) and Fukushima in Japan (2011). These two events were by far the largest nuclear incidents in history; the only disasters to receive a level 7 (the maximum classification) on the International Nuclear Event Scale.

How many deaths did each of these events cause?

When it comes to nuclear accidents there are really two fatal impacts to consider: the first being the number of direct deaths which occurred either at the time of incident, or in the days which followed (i.e. the acute impacts); the second being the long-term (chronic) impacts of radiation exposure, which has known links to the incidence of several forms of cancer.

Deaths from Chernobyl

31 people died as a direct result of the Chernobyl accident; two died from blast effects and a further 29 firemen died as a result of acute radiation exposure (where acute refers to infrequent exposure over a short period of time) in the days which followed.25

The number of people who were impacted over long-term radiation exposure is more difficult to discern and remains highly contested. Part of this difficulty lies in the methodology used to estimate long-term deaths from low-level radiation exposure. In the published estimates shown, studies have utilised a methodology termed the ‘linear no-threshold model’ (LNT); this model is typically applied in assessments of radiation risk and in setting regulatory limits for environmental protection. However, the LNT method remains strongly contested, and is assumed to provide a conservative estimate of potential mortality [we have provided a short discussion on the LNT model and its implications in the technical notes at the end of this post]. As such, we may expect that the numbers quoted below to be interpreted as the upper limit of a given source’s estimate.

The chart here reflects a range of published estimates on the number of deaths resultant from the Chernobyl disaster. In its 2005/06 assessment ‘Chernobyl’s Legacy: Health, Environmental and Socio-Economic Impacts’ the World Health Organisation (WHO) estimated that the total number of long-term deaths will be around 4,000.26

However, this figure is related only to the proximate populations of Ukraine, Russia and Belarus which were exposed to high radiation levels; if extended to estimates of those exposed to low-level radiation across the region, this number rises to 9000.27

Other studies have suggested higher figures. A study in the International Journal of Cancer by Cardis et al. (2006) estimates a total of 16,000 deaths across Europe.28

Radiation scientists Fairlie and Sumner provide some of highest estimates, predicting between 30,000-60,000 deaths.29

The challenge of cancer risk attribution- especially at low doses of exposure in further geographic regions- makes this process of estimation particularly difficult. In its 2008 report, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) refrained from quoting a figure for the absolute number of deaths within populations exposed to low radiation doses from Chernobyl because of uncertainty in the limit no-threshold model and “unacceptable uncertainties in the predictions”.30

As shown in the chart, most published estimates lie in the range between thousands and tens of thousands.

Deaths from Fukushima

In the case of Fukushima, although 40 to 50 people experienced physical injury or radiation burns at the nuclear facility, the number of direct deaths from the incident are quoted to be zero. In 2018, the Japanese government reported that one worker has since died from lung cancer as a result of exposure from the event.

However, mortality from radiation exposure was not the only threat to human health: the official death toll was 573 people – who died as a result of evacuation procedures and stress-induced factors. This figure ranges between 1,000-1,600 deaths from evacuation (the evacuation of populations affected by the earthquake and tsunami at the time can make sole attribution to the nuclear disaster challenging). Stress-induced deaths affected mostly older people; more than 90 percent of mortality occurred in individuals over the age of 66.

In the chart we have shown the estimated number of total deaths by attributed cause.

How many are projected to suffer in the long-term from low-level radiation exposure? In its initial Health Risk Assessment of the nuclear disaster – published in 2013 – the World Health Organization (WHO) note exposure levels too low to affect human health for the national population, with exception to a few communities in closest proximity.31 The follow-up WHO Report published five years on – in 2015 – suggests very low risk of increased cancer deaths in Japan.32 In a review of the response and long-term health impacts of Fukushima, published by Michael Reich and Aya Goto (2015) in journal The Lancet, the authors note that: “no one has died from radiation exposure, and the UN Scientific Committee on the Effects of Atomic Radiation report in 2013 stated that substantial changes in future cancer statistics attributed to radiation exposure are not expected to be observed”.33,34

In more recent evaluations of rates of perinatal mortality (that is, stillbirths or deaths within the first week of life) in areas closest to the Fukushima site, there were no statistical indications of increased incidence.35 In fact, rates of perinatal mortality showed an overall decline with time—the general trend we see through improved healthcare and healthier lifestyles.

The death toll of the Fukushima nuclear accident dominated headlines for weeks after the event and overshadowed the much larger tragedy that happened at the same time and place: the Tsunami killed 15,893 people, more than 25 times the number from the nuclear accident.

Why was the death toll from Chernobyl so much higher than Fukushima?

Chernobyl and Fukushima are the only two disasters to receive a level 7 (the maximum classification) on the International Nuclear Event Scale. But why are more expected to die from Chernobyl than Fukushima?

There are a couple of factors which are likely to have played a key role here. The first of these concerns the technical functionality and safety measures of the respective nuclear facilities. Chernobyl occurred 25 years prior to Fukushima; it was the first instance of a nuclear accident at this scale. From a technical perspective, the nuclear reactors at Chernobyl were poorly designed to deal with such a scenario. Its fatal RBMK reactor had no containment structure, allowing radioactive material to spill into the atmosphere (in contrast, Fukushima’s reactors had steel-and-concrete containment structures, although it’s likely that at least one of these were also breached). Crucially, the cooling systems of both plants worked very differently; at Chernobyl, the loss of cooling water as steam actually served to accelerate reactivity levels in the reactor core, creating a positive feedback loop towards fatal explosion (the opposite is true of Fukushima, where the reactivity reduces as temperatures rise, effectively operating as a self-shutdown measure).

These technical differences undoubtedly played a role in the relative levels of exposure from both events. However, the governmental response to both events is also likely to have played a crucial role in the number of people who were exposed to high levels of radiation in the days which followed. In the case of Fukushima, the Japanese government responded quickly to the crisis with evacuation efforts extending rapidly from a three kilometre (km), to 10km, to 20km radius whilst the incident at the site continued to unfold. In comparison, the response in the former Soviet Union was one of denial and secrecy.

It’s reported that in the days which followed the Chernobyl disasters, residents in surrounding areas were uninformed of the radioactive material in the air around them. In fact, it took at least three days for the Soviet Union to admit an accident had taken place, and did so after radioactive sensors at a Swedish plant were triggered from dispersing radionuclides. It’s estimated that the delayed reaction from the Soviet government and poor precautionary steps taken (people continued to drink locally-produced, contaminated milk, for example) led to at least 6,000 thyroid cancer cases in exposed children.

Whilst prevention, and ultimately containment (which are predominantly technical issues), are crucial to the safety of nuclear energy production, these two events also highlight the importance of political governance and response in the aftermath of such disasters.

Nuclear energy is one of the safest energy sources

The potential risks of nuclear energy are real: in both Chernobyl and Fukushima, deaths occurred as a result of direct nuclear impacts, radiation exposure and psychological stress. Nonetheless, of the two largest nuclear disasters, the death toll was of the order of thousands, and hundreds in the latest. Arguably still too many, but far fewer than the millions who die every year from impacts of other conventional energy sources.

As covered in a separate blog post on the relative safety of energy sources, the comparatively low death toll from nuclear energy (resulting in 442 times fewer deaths relative to brown coal per unit of energy, even with radioactive exposure deaths included) is largely at-odds with public perceptions, where public support for nuclear energy is often low as a result of high safety concerns. The key distinction here is that nuclear risk is generally focused within low-probability, high-impact single events in contrast to air pollution impacts which provide a persistent background health risk.

Technical notes: how are deaths from radiation exposure estimated?