Nuclear power is often promoted as a low-carbon source that mitigates fossil fuel emissions and the resulting health damage and deaths caused by air pollution. But is it possible to provide estimates and actually quantify these effects?

A new paper from NASA’s Goddard Institute authored by Pushker Kharecha and James Hansen in the journal Environmental Science and Technology purports to do just that. Hansen is well known as one of the founders of modern global warming science. The authors come up with the striking figure of 1.8 million as the number of lives saved by replacing fossil fuel sources with nuclear. They also estimate the saving of up to 7 million lives in the next four decades, along with substantial reductions in carbon emissions, were nuclear power to replace fossil fuel usage on a large scale. In addition the study finds that the proposed expansion of natural gas would not be as effective in saving lives and preventing carbon emissions. In general the paper provides optimistic reasons for the responsible and widespread use of nuclear technologies in the near future. It also drives home the point that nuclear energy has prevented many more deaths than what it has caused.

Let’s start with the abstract:

“In the aftermath of the March 2011 accident at Japan’s Fukushima Daiichi nuclear power plant, the future contribution of nuclear power to the global energy supply has become somewhat uncertain. Because nuclear power is an abundant, low-carbon source of base-load power, on balance it could make a large contribution to mitigation of global climate change and air pollution. Using historical production data, we calculate that global nuclear power has prevented about 1.84 million air pollution-related deaths and 64 gigatonnes (Gt) CO2-equivalent greenhouse gas (GHG) emissions that would have resulted from fossil fuel burning. Based on global projection data that take into account the effects of Fukushima, we find that by midcentury, nuclear power could prevent an additional 420,000 to 7.04 million deaths and 80 to 240 GtCO2-eq emissions due to fossil fuels, depending on which fuel it replaces. By contrast, we assess that large-scale expansion of natural gas use would not mitigate the climate problem and would cause far more deaths than expansion of nuclear power.”

The authors look at deaths caused by various power sources during the period 1971-2009. To provide a comparison they build a model in which all the power which was provided by nuclear energy was hypothetically replaced by fossil fuel sources. They employ the same technique for the projected 2010-2050 period, assuming that all current nuclear power sources have been replaced by fossil fuels. Two scenarios are considered - one in which nuclear is replaced by coal and another in which it is replaced by gas. This takes into account the uncertainty regarding the nature of fossil fuel usage that’s inherent in future energy projections.

It’s worth noting that the authors consider only deaths and exclude from the model serious health crises such as heart failure, bronchitis and other respiratory problems; including these problems would further weaken the case for fossil fuels. The study also excludes aspects of nuclear power that cannot be easily quantified, such as deaths from nuclear proliferation.

The results are quite clear. In the 2000-2009 period alone nuclear power may have prevented an average of 76,000 deaths. This is an average and the range is quite large, but even the lower limit runs into the tens of thousands. For countries like Germany which have cut back on nuclear, the range of deaths is naturally higher. This is a result that Japan's current leaders should take to heart.

What is even more starkly clear is that the number of deaths caused by nuclear power is far lower than those saved by it; in fact there’s scant comparison. As the report notes, even the worst nuclear accident in history (Chernobyl) caused about 40 deaths; these include 28 immediate responders and about 15 deaths caused among 6000 victims of excess cancers (it’s always very difficult to detect statistically significant excess cancers in the presence of a high natural background rate). There have been no deaths attributable to the Three Mile Island accident. And while the verdict on Fukushima is still not definitive, the latest report on the accident predicts no direct deaths and a much lower exposure to radiation for the surrounding population than that purported to lead to fatal cancers. The bottom line is that, even assuming pessimistic scenarios, the number of deaths caused by nuclear power is a minuscule fraction of those lives which were saved by nuclear power replacing fossil fuels.

Nuclear-free projections for the next four decades look even more dire. The authors estimate between 4 and 7 million deaths for the “All-Coal” scenario and between 420, 000 – 680, 000 deaths for an “All-Gas” energy policy. This is something which countries like Germany and Japan that are planning to phase out nuclear must seriously consider. Only if all the nuclear power were replaced by equipotent renewable energy sources in the next four decades would these deaths be prevented. This kind of high-capacity deployment of renewables seems quite uncertain for now.

Of course it’s not just the deaths. All the fossil fuel sources replacing nuclear power would contribute a very significant concentration of greenhouse gases to the atmosphere and severely aggravate the effects of climate change. The authors estimate an additional 80 to 240 GtCO 2 -equivalents of greenhouse gases from fossil fuel sources in the next forty years if nuclear power were to decline. To put this into perspective, consider that the total amount of “allowable” input of greenhouse gases required to achieve a 350 ppm CO2 target by the end of the century is 500 GtCO2-equivalent. Nuclear power could thus reduce this load by 16-48%. Deploying some of the new promising reactor technologies could reduce this load even more.

The conclusions of the study are quite unambiguous. Even assuming uncertainties, nuclear power has saved at least hundreds of thousands of lives in the past forty years, and possibly millions. This is in stark contrast to the small number of lives lost in only one catastrophic nuclear accident. There are many more millions that would be lost if countries were to embark on a nuclear-free future replaced by fossil fuels. Natural gas might be a reasonable bridge to this future but it’s clear that it cannot be a sustainable one. It would take “heroic” efforts (in the words of the International Energy Agency) to replace all the nuclear power in the world with renewables in the next forty years. New generations of nuclear reactors like the molten salt and pebble bed reactors promise to make nuclear energy even more safe, efficient and cheap. Even Bill Gates is investing in a novel reactor design. The verdict is staring us in the face; we ignore energy from the atom at our own peril, and at the potential cost of a staggering number of lives from our children and grandchildren’s generation. It's not the kind of legacy we want to be remembered for.