### TL;DR The production of cheap energy is a fundamental compon...
The top five biggest CO2 emitters accounted for 56% of global emiss...
> ***As stand-alone events these [Nuclear accident's] impacts are l...
### Primary energy consumption by energy source <iframe src="https...
For each country you take into account all the energy produced by n...
Health effects of energy production (2014) <iframe src="https://...
**Capacity Factor (CF):** The net capacity factor of a power plant...
This model reflects the mortality from all stages of the fuel cycle...
> However, empirical evidence indicates that the April 1986 Chernob...
>***In conclusion, it is clear that nuclear power has provided a la...
Prevented Mortality and Greenhouse Gas Emissions from Historical
and Projected Nuclear Power
Pushker A. Kharecha* and James E. Hansen
NASA Goddard Institute for Space Studies and Columbia University Earth Institute, 2880 Broadway, New York, New York 10025,
United States
*
S
Supporting Information
ABSTRACT: In the aftermath of the March 2011 accident at Japans
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, 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 an average of 1.84 million air pollution-related deaths
and 64 gigatonnes of CO
2
-equivalent (GtCO
2
-eq) greenhouse gas (GHG)
emissions that would have resulted from fossil fuel burning. On the basis of
global projection data that take into account the eects of the Fukushima
accident, we nd that nuclear power could additionally prevent an average of
420 0007.04 million deaths and 80240 GtCO
2
-eq emissions due to fossil
fuels by midcentury, depending on which fuel it replaces. By contrast, we
assess that large-scale expansion of unconstrained natural gas use would not mitigate the climate problem and would cause far
more deaths than expansion of nuclear power.
INTRODUCTION
It has become increasingly clear that impacts of unchecked
anthropogenic climate change due to greenhouse gas (GHG)
emissions from burning of fossil fuels could be catastrophic for
both human society and natural ecosystems (in ref 1, see
Figures SPM.2 and 4.4) and that the key time frame for
mitigating the climate crisis is the next decade or so.
2,3
Likewise, during the past decade, outdoor air pollution due
largely to fossil fuel burning is estimated to have caused over 1
million deaths annually worldwide.
4
Nuclear energy (and other
low-carbon/carbon-free energy sources) could help to mitigate
both of these major problems.
5
The future of global nuclear power will depend largely on
choices made by major energy-using countries in the next
decade or so.
6
While most of the highly nuclear-dependent
countries have armed their plans to continue development of
nuclear power after the Fukushima accident, several have
announced that they will either temporarily suspend plans for
new plants or completely phase out existing plants.
2
Serious
questions remain about safety, proliferation, and disposal of
radioactive waste, which we have discussed in some detail
elsewhere.
7
Here, we examine the historical and potential future role of
nuclear power with respect to prevention of air pollution-
related mortality as well as GHG emissions on multiple spatial
scales. Previous studies have quanti ed global-scale avoided
GHG emissions due to nuclear power (e.g., refs 5 and 810);
however, the issue of avoided human deaths remains largely
unexplored. We focus on the world as a whole, OECD Europe,
and the ve countries with the highest annual CO
2
emissions in
the last several years. In order, these top ve CO
2
emitters are
China, the United States, India, Russia, and Japan, accounting
for 56% of global emissions from 2009 to 2011.
11
To estimate
historically prevented deaths and GHG emissions, we start with
data for global annual electricity generation by energy source
from 1971 to 2009 (Figure 1). We then apply mortality and
GHG emissions factors, dened respectively as deaths and
emissions per unit electric energy generated, for relevant
electricity sources (Table 1). For the projection period 2010
2050, we base our estimates on recent (post-Fukushima)
nuclear power trajectories given by the UN International
Atomic Energy Agency (IAEA).
6
METHODS
Calculation of Prevented Mortality and GHG Impacts.
For the historical period 19712009, we assume that all nuclear
power supply in a given country and year would instead have
been delivered by fossil fuels (specically coal and natural gas),
given t heir worldwide dominance and t he very small
contribution of nonhydro renewables to world electricity thus
far (Figure 1). There are of course numerous complications
involved in trying to design such a replacement scenario (e.g.,
evolving technological and socioeconomic conditions), and the
Received: December 14, 2012
Revised: March 1, 2013
Accepted: March 15, 2013
Published: March 15, 2013
Article
pubs.acs.org/est
© 2013 American Chemical Society 4889 dx.doi.org/10.1021/es3051197 | Environ. Sci. Technol. 2013, 47, 48894895
retroactive energy mix cannot be known with total accuracy and
realism; thus, simplifying yet tenable assumptions are necessary
and justied.
To determine the proportional substitution by coal and gas
in our baseline historical scenario, we rst examine the world
nuclear reactor properties provided by IAEA.
12
On the basis of
typical international values for coal and gas capacity factors
(CFs),
13
we then assume that each of the 441 reactors listed in
Table 14 of ref 12 with a CF of greater than 65% is replaced by
coal and each reactor with a CF of less than or equal to 65% is
replaced by gas.
For each country x, we rst calculate P
i
(x), the power (not
energy) generated by each reactor i:
=×
P
xxCx() CF() ()
iii
(1)
where CF
i
and C
i
denote the reactor capacity factor and net
capacity, respectively, listed in Table 14 of ref 12. We then
calculate f
i
(x), the CF-weighted proportion of generated power
by each reactor:
=
f
xPx Px() ()/ ()
i
i
i
i
(2)
Next, we calculate F
j
(x), the total proportion of generated
nuclear power replaced by power from fossil fuel j:
=Fx f x() ()
j
i
i
j()
(3)
where f
i
(j)
(x) simply denotes grouping of all the f
i
values by
replacement fuel j. For reference, on the global scale, this yields
about 95% replacement by coal and 5% by gas in our baseline
historical scenario, which we suggest is plausible for the reasons
given in the Results and Discussion section. Lastly, we calculate
I(x, t), the annual net prevented impacts (mortality or GHG
emissions) from nuclear power in country x and year t as
follows:
=Σ × × ×
I
xt Fx nxt nxt(, ) [IF () (, )] IF (, )
jj j n
(4)
where IF
j
is the impact factor for fossil fuel j (from Table 1),
n(x, t) is the nuclear power generation (in energy units; from
refs 6 and 14), and IF
n
is the impact factor for nuclear power
(from Table 1). Note that the rst term in eq 4 reects gross
avoided impacts, while the second reects direct impacts of
nuclear power.
For the projection period 20102050, using eq 4, we
calculate human deaths and GHG emissions that could result if
all projected nuclear power production is canceled and again
replaced only by fossil fuels. Of course, some or most of this
hypothetically canceled nuclear power could be replaced by
power from renewables, which have generally similar impact
factors as nuclear (e.g., see Figure 2 of ref 7). Thus, our results
for the projection period should ultimately be viewed as upper
limits on potentially prevented impacts from future nuclear
power.
We project annual nuclear power production in the regions
containing the top ve CO
2
-emitting countries and Western
Europe based on the regional decadal projections in Table 4 of
ref 6, which we linearly interpolate to an annual scale. To set
F
j
(x) in eq 4, we consider two simplied cases for both the
global and regional scales. In the rst (all coal), F
j
(x) is xed
at 100% coal, and in the second ( all gas), it is xed at 100%
gas. This approach yields the full range of potentially prevented
impacts from future nuclear power. It is taken here because of
the lack of country-specic projections in ref 6 as well as the
large uncertainty in determining which fossil fuel(s) could
replace future nuclear power, given recent trends in electricity
production (Figure 1, Figure S3 [Supporting Information], and
ref 14).
Methodological Limitations. The projections for nuclear
power by IAEA
6
assume es sent ially n o clim ate- chan ge
mitigation meas ures in the low-end case and aggressive
mitigation measures in the high-end case. It is unclear which
path the world will follow; however, these IAEA projections do
take into account the eects of the Fukushima accident. It
seems that, except possibly for Japan, the top ve CO
2
-emitting
countries are not planning a phase-down of pre-Fukushima
plans for future nuclear power. For instance, China, India, and
Figure 1. World electricity generation by power source for 19712009
(data from ref 14). In the past decade (20002009), nuclear power
provided an average 15% of world generation; coal, gas, and oil
provided 40%, 20%, and 6%, respectively; and renewables provided
16% (hydropower) and 2% (nonhydro).
Table 1. Mortality and GHG Emission Factors Used in This
Study
a
electricity
source mean value (range) unit
b
source
coal 28.67 (7.15114) deaths/TWh ref 16
77 (19.25308) deaths/TWh ref 16 (China)
c
1045 (9091182) tCO
2
-eq/GWh ref 30
natural gas 2.821 (0.711.2) deaths/TWh ref 16
602 (386818) tCO
2
-eq/GWh ref 30
nuclear 0.074 (range not given) deaths/TWh ref 16
65 (10130)
d
tCO
2
-eq/GWh ref 34
a
Mortality factors are based on analysis for Europe (except as
indicated) and represent the sum of accidental deaths and air
pollution-related eects in Table 2 of ref 16. They reect impacts from
all stages of the fuel cycle, including fuel extraction, transport,
transformation, waste disposal, and electricity transport. Their ranges
are 95% con dence intervals and represent deviation from the mean
by a factor of 4. Mortality factor for coal is the mean of the factors for
lignite and coal in ref 16. Mean values for emission factors are the
midpoints of the ranges given in the sources. Water pollution is also a
signicant impact but is not factored into these values. Additional
uncertainties and limitations inherent in these factors are discussed in
the text.
b
TWh = terawatt hour; GWh = gigawatt hour; tCO
2
-eq =
tonnes of CO
2
-equivalent emissions.
c
Range is not given in source for
China, but for consistency with other factors, it is assumed to be 4
times lower and higher than the mean.
d
Some authors contend the
upper limit is signicantly higher, but their conclusions are based on
dubious assumptions.
35
Environmental Science & Technology Article
dx.doi.org/10.1021/es3051197 | Environ. Sci. Technol. 2013, 47, 488948954890
Russia have armed plans to increase their current nuclear
capacity by greater than 3-fold, greater than 12-fold, and 2-fold,
respectively (see Table 12.2 of ref 2). In Japan, the future of
nuclear power now seems unclear; in the scal year following
the Fukushima accident, nuclear power generation in Japan
decreased by 63%, while fossil fuel power generation increased
by 26% (ref 15), thereby almost certainly increasing Japans
CO
2
emissions.
Although our analysis reects mortality from all stages of the
fuel cycle for each energy source, it excludes serious illnesses,
including respiratory and cerebrovascular hospitalizations,
chronic bronchitis, congestive heart failure, nonfatal cancers,
and hereditary eects. For fossil fuels, such illnesses are
estimated to be approximately 10 times higher than the
mortality factors in Table 1, while for nuclear power, they are
3 times higher.
16
Another important limitation is that the
mortality factors exclude the impacts of anthropogenic climate
change and development-related dierences, as explained in the
Results and Discussion section. Aspects of nuclear power that
cannot me aningfully be quant ied due to very large
uncertainties (e.g., potential mortality from proliferation of
weapons-grade material) are also not included in our analysis.
Proportions of fossil fuels in our projection cases are
assumed to be xed (for the purpose of determining upper and
lower bounds) but will almost certainly vary across years and
decades, as in the historical period (Figure 1). The dominance
of coal in the global average electricity mix seems likely for the
near future though (e.g., Figure 5.2 of ref 2). However, even if
there is large-scale worldwide electric fuel switching from coal
to gas, our assessment is that the ultimate GHG savings from
such a transition are unlikely to be sucient to minimize the
risk of dangerous anthropogenic climate change (unless the
resulting emissions are captured and stored), as discussed in the
next section.
RESULTS AND DISCUSSION
Mortality. We calculate a mean value of 1.84 million human
deaths prevented by world nuclear power production from
1971 to 2009 (see Figure 2a for full range), with an average of
76 000 prevented deaths/year from 2000 to 2009 (range 19
000300 000). Estimates for the top ve CO
2
emitters, along
with full estimate ranges for all regions in our baseline historical
scenario, are also shown in Figure 2a. For perspective, results
for upper and lower bound scenarios are shown in Figure S1
(Supporting Information). In Germany, which has announced
plans to shut down all reactors by 2022 (ref 2), we calculate
that nuclear power has prevented an average of over 117 000
deaths from 1971 to 2009 (range 29 000470 000). The large
ranges stem directly from the ranges given in Table 1 for the
mortality factors.
Our estimated human deaths caused by nuclear power from
1971 to 2009 are far lower than the avoided deaths. Globally,
we calculate 4900 such deaths, or about 370 times lower than
our result for avoided deaths. Regionally, we calculate
approximately 1800 deaths in OECD Europe, 1500 in the
United States, 540 in Japan, 460 in Russia (includes all 15
former Soviet Union countries), 40 in China, and 20 in India.
About 25% of these deaths are due to occupational accidents,
and about 70% are due to air pollution-related eects
Figure 2. Cumulative net deaths prevented assuming nuclear power replaces fossil fuels. (a) Results for the historical period in this study (1971
2009), showing mean values (labeled) and ranges for the baseline historical scenario. Results for (b) the high-end and (c) low-end projections of
nuclear power production by the UN IAEA
6
for the period 20102050. Error bars reect the ranges for the fossil fuel mortality factors listed in
Table 1. The larger columns in panels b and c reect the all coal case and are labeled with their mean values, while the smaller columns reect the all
gas case; values for the latter are not shown because they are all simply a factor of 10 lower (reecting the order-of-magnitude dierence between
the mortality factors for coal and gas shown in Table 1). Countries/regions are arranged in descending order of CO
2
emissions in recent years.
FSU15 = 15 countries of the former Soviet Union, and OECD = Organization for Economic Cooperation and Development.
Environmental Science & Technology Article
dx.doi.org/10.1021/es3051197 | Environ. Sci. Technol. 2013, 47, 488948954891
(presumably fatal cancers from radiation fallout; see Table 2 of
ref 16).
However, empirical evidence indicates that the April 1986
Chernobyl accident was the worlds only source of fatalities
from nuclear power plant radiation fallout. According to the
latest assessment by the United Nations Scientic Committee
on the Eects of Atomic Radiation (UNSCEAR),
17
43 deaths
are conclusively attributable to radiation from Chernobyl as of
2006 (28 were plant sta/rst responders and 15 were from the
6000 diagnosed cases of thyroid cancer). UNSCEAR
17
also
states that reports of an increase in leukemia among recovery
workers who received higher doses are inconclusive, although
cataract development was clinically signicant in that group;
otherwise, for these workers as well as the general population,
there has been no persuasive evidence of any other health
eect attributable to radiation exposure.
17
Furthermore, no deaths have been conclusively attributed (in
a scientically valid manner) to radiation from the other two
major accidents, namely, Three Mile Island in March 1979, for
which a 20 year comprehensive scientic health assessment was
done,
18
and the March 2011 Fukushima Daiichi accident. While
it is too soon to meaningfully assess the health impacts of the
latter accident, one early analysis
19
indicates that annual
radiation doses in nearby areas were much lower than the
generally acce pted 100 mSv threshold
17
for fatal disease
development. In any case, our calculated value for global
deaths caused by historical nuclear power (4900) could be a
major overestimate relative to the empirical value (by 2 orders
of magnitude). The absence of evidence of large mortality from
past nuclear accidents is consistent with recent ndings
20,21
that
the linear no-threshold model used to derive the nuclear
mortality factor in Table 1 (see ref 22) might not be valid for
the relatively low radiation doses that the public was exposed to
from nuclear power plant accidents.
For the projection period 20102050, we nd that, in the all
coal case (see the Methods section), an average of 4.39 million
and 7.04 million deaths are prevented globally by nuclear power
production for the low-end and high-end projections of IAEA,
6
respectively. In the all gas case, an average of 420 000 and 680
000 deaths are prevented globally (see Figure 2b,c for full
ranges). Regional results are also shown in Figure 2b,c. The Far
East and North America have particularly high values, given
that they are projected to be the biggest nuclear power
producers (Figure S2, Supporting Information). As in the
historical period, calculated deaths caused by nuclear power in
our projection cases are far lower (2 orders of magnitude) than
the avoided deaths, even taking the nuclear mortality factor in
Table 1 at face value (despite the discrepancy with empirical
data discussed above for the historical period).
The substantially lower deaths in the projected all gas case
follow simply from the fact that gas is estimated to have a
mortality factor an order of magnitude lower than coal (Table
1). However, this does not necessarily provide a valid argument
for such large-scale fuel switching for mitigation of either
climate change or air pollution, for several reasons. First, it is
important to bear in mind that our results for prevented
mortality are likely conservative, because the mortality factors
in Table 1 do not incorporate impacts of ongoing or future
anthropogenic climate change.
16
These impacts are likely to
become devastating for both human health and ecosystems if
recent global GHG emission trends continue.
1,3
Also, potential
global natural gas resources are enormous; published estimates
for technically recoverable unconventional gas resources
suggest a carbon content ranging from greater than 700
GtCO
2
(based on refs 23 and 24) to greater than 17 000
GtCO
2
(based on refs 24 and 25). While we acknowledge that
natural gas might play an important role as a transition fuel to
a clean-energy era due to its lower mortality (and emission)
factor relative to coal, we stress that long-term, widespread use
Figure 3. Cumulative net GHG emissions prevented assuming nuclear power replaces fossil fuels. Same panel arrangement as Figure 2, except mean
values for all cases are labeled. Error bars reect the ranges for the fossil fuel emission factors listed in Table 1.
Environmental Science & Technology Article
dx.doi.org/10.1021/es3051197 | Environ. Sci. Technol. 2013, 47, 488948954892
of natural gas (without accompanying carbon capture and
storage) could lead to unabated GHG emissions for many
decades, given the typically multidecadal lifetime of energy
infrastructure, thereby greatly complicating climate change
mitigation e orts.
GHG Emissions. We calculate that world nuclear power
generation prevented an average of 64 gigatonnes of CO
2
-
equivalent (GtCO
2
-eq), or 17 GtC-eq, cumulative emissions
from 1971 to 2009 (Figure 3a; see full range therein), with an
average of 2.6 GtCO
2
-eq/year prevented annual emissions from
2000 to 2009 (range 2.42.8 GtCO
2
/year). Regional results are
also shown in Figure 3a. Our global results are 714% lower
than previous estimates
8,9
that, among other dierences,
assumed all historical nuclear power would have been replaced
only by coal, and 34% higher than in another study
10
in which
the methodology is not explained clearly enough to infer the
basis for the dierences. Given that cumulative and annual
global fossil fuel CO
2
emissions during the above periods were
840 GtCO
2
and 27 GtCO
2
/year, respectively,
11
our mean
estimate for cumulative prevented emissions may not appear
substantial; however, it is instructive to lo ok at other
quantitative comparisons.
For instance, 64 GtCO
2
-eq amounts to the cumulative CO
2
emissions from coal burning over approximately the past 35
years in the United States, 17 years in China, or 7 years in the
top ve CO
2
emitters.
11
Also, since a 500 MW coal-red power
plant typically emits 3 MtCO
2
/year,
26
64 GtCO
2
-eq is
equivalent to the cumulative lifetime emissions from almost
430 such plants, assuming an average plant lifetime of 50 years.
It is therefore evident that, without global nuclear power
generation in recent decades,near-termmitigationof
anthropogenic climate change would pose a much greater
challenge.
For the projection period 20102050, in the all coal case, an
average of 150 and 240 GtCO
2
-eq cumulative global emissions
are prevented by nuclear power for the low-end and high-end
projections of IAEA,
6
respectively. In the all gas case, an average
of 80 and 130 GtCO
2
-eq emissions are prevented (see Figure
3b,c for full ranges). Regional results are also shown in Figure
3b,c. These results also dier substantially from previous
studies,
9,10
largely due to dierences in nuclear power
projections (see the Supporting Information).
To put our calculated overall mean estimate (80240
GtCO
2
-eq) of potentially prevented future emissions in
perspective, note that, to achieve a 350 ppm CO
2
target near
the end of this century, cumulative allowable fossil CO
2
emissions from 2012 to 2050 are at most 500 GtCO
2
(ref 3).
Thus, projected nuclear power could reduce the climate-change
mitigation burden by 1648% over the next few decades
(derived by dividing 80 and 240 by 500).
Uncertainties. Our results contain various uncertainties,
primarily stemming from our impact factors (Table 1) and our
assumed replacement scenarios for nuclear power. In reality,
the impact factors are not likely to remain static, as we
(implicitly) assumed; for instance, emission factors depend
heavily on the particular mix of energy sources. Because our
impact factors neglect ongoing or projected climate impacts as
well as the signicant disparity in pollution between developed
and developing countries,
16
our results for both avoided GHG
emissions and avoided mortality could be substantial under-
estimates. For example, in China, where coal burning accounts
for over 75% of electricity generation in recent decades (ref 14;
Figure S3, Supporting Information), some coal-red power
plants that meet domestic environmental standards have a
mortality factor almost 3 times higher than the mean global
value (Table 1). These dierences related to development
status will become increasingly important as fossil fuel use and
GHG emissions of developing countries continue to outpace
those of developed countries.
11
On the other hand, if coal would not have been as dominant
a replacement for nuclear as assumed in our baseline historical
scenario, then our avoided historical impacts could be
overestimates, since coal causes much larger impacts than gas
(Table 1). However, there are several reasons this is unlikely.
Key characteristics of coal plants (e.g., plant capacity, capacity
factor, and total production costs) are historically much more
similar to nuclear plants than are those of natural gas plants.
13
Also, the vast majority of existing nuclear plants were built
before 1990, but advanced gas plants that would be suitable
replacements for base-load nuclear plants (i.e., combined-cycle
gas turbines) have only become available since the early
1990s.
13
Furthermore, coal resources are highly abundant and
widespread,
24,25
and coal fuel and total production costs have
long been relatively low, unlike hi storically available gas
resources and production costs.
13
Thus, it is not surprising
that coal has been by far the dominant source of global
electricity thus far (Figure 1). We therefore assess that our
baseline historical replacement scenario is plausible and that it
is not as signicant an uncertainty source as the impact factors;
that is, our av oided historical impacts are more likely
underestimates, as discussed in the above paragraph.
Implications. More broadly, our results underscore the
importance of avoiding a false and counterproductive
dichotomy between reducing air pollution and stabilizing the
climate, as elaborated by others.
2729
If near-term air pollution
abatement trumps the goal of long-term climate protection,
governments might decide to carry out future electric fuel
switching in even more climate-impacting ways than we have
examined here. For instance, they might start large-scale
production and use of gas derived from coal (syngas), as coal
is by far the most abundant of the three conventional fossil
fuels.
24,25
While this could reduce the very high pollution-
related deaths from coal power (Figure 2), the GHG emissions
factor for syngas is substantially higher (between 5% and
90%) than for coal,
30
thereby entailing even higher electricity
sector GHG emissions in the long term.
In conclusion, it is clear that nuclear power has provided a
large contribution to the reduction of global mortality and
GHG emissions due to fossil fuel use. If the role of nuclear
power signicantly declines in the next few decades, the
International Energy Agency asserts that achieving a target
atmospheric GHG level of 450 ppm CO
2
-eq would require
heroic achievements in the deployment of emerging low-
carbon technologies, which have yet to be proven. Countries
that rely heavily on nuclear power would nd it particularly
challenging and signicantly more costly to meet their targeted
levels of emissions.
2
Our analysis herein and a prior one
7
strongly support this conclusion. Indeed, on the basis of
combined evidence from paleoclimate data, observed ongoing
climate impacts, and the measured planetary energy imbalance,
it appears increasingly clear that the commonly discussed
targets of 450 ppm and 2 °C global temperature rise (above
preindustrial levels) are insucient to avoid devastating climate
impacts; we have suggested elsewhere that more appropriate
targets are less than 350 ppm and 1 °C (refs 3 and 3133).
Aiming for these targets emphasizes the importance of retaining
Environmental Science & Technology Article
dx.doi.org/10.1021/es3051197 | Environ. Sci. Technol. 2013, 47, 488948954893
and expanding the role of nuclear power, as well as energy
eciency improvements and renewables, in the near-term
global energy supply.
ASSOCIATED CONTENT
*
S
Supporting Information
Comparison with avoided GHG emissions in pr ojection
periods of prior studies; gures showing upper and lower
bounds for prevented deaths and GHG emissions assuming
nuclear power replaces fossil fuels from 19712009, projec-
tions of nuclear power production by region, and total
electricity production from 19712009 by fuel source for the
top ve CO
2
-emitting countries and OECD Europe. This
material is available free of charge via the Internet at http://
pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*Phone: (212) 678-5536; fax: (212) 678-5552; e-mail:
pushker@giss.nasa.gov.
Author Contributions
P.K. designed the study with input from J.H.; P.K. performed
the calculations and analysis and wrote the paper with feedback
from J.H.
Notes
The authors declare no competing nancial interest.
ACKNOWLEDGMENTS
We th an k Chuc k Kutsc her of the U.S . DOE Natio na l
Renewable Energy Laboratory for helpful comments on our
methodology and three anonymous reviewers for helpful
feedback on our manuscript. Funding for this work was
provided by the Lenfest Foun dation and the Columbia
University NASA Cooperative Agreement (award
NNX11AR63A).
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Discussion

### Primary energy consumption by energy source <iframe src="https://ourworldindata.org/grapher/primary-energy-consumption-by-source-and-region" style="width: 100%; height: 600px; border: 0px none;"></iframe> For each country you take into account all the energy produced by nuclear power and create a model to replace it with alternative fuels (coal or gas). For each reactor you take the capacity factor and replace it with an alternative fuel, coal ($CP>65\%$) or gas ($CP\leq 65\%$). Once we determine the percentage of energy for each fuel source we can compute the total number of deaths that would have happened by taking into account the impact factors in table 1. To compute the avoided deaths we just need to subtract the deaths that are caused by nuclear. The top five biggest CO2 emitters accounted for 56% of global emissions from 2009 to 2011. The following table shows emissions for the **top 20 emitters for the year of 2015:** !["biggest co2 emitters"](https://i.imgur.com/IGEmuPr.png) *Table: 20 countries that emitted the most carbon dioxide in 2015* Source: [Each Country's Share of CO2 Emissions](https://www.ucsusa.org/global-warming/science-and-impacts/science/each-countrys-share-of-co2.html) > However, empirical evidence indicates that the April 1986 Chernobyl accident was the world’s only source of fatalities from nuclear power plant radiation fallout. This changed in September 2018 (after this paper was published) the Japanese government has recognized for the first time that a worker at the Fukushima Daiichi nuclear power plant has died as a result of radiation exposure. Learn more here: [Japan acknowledges first radiation death among Fukushima workers](https://www.reuters.com/article/us-japan-fukushima-radiation/japan-acknowledges-first-radiation-death-among-fukushima-workers-idUSKCN1LL0OA) >***In conclusion, it is clear that nuclear power has provided a large contribution to the reduction of global mortality and GHG emissions due to fossil fuel use. If the role of nuclear power significantly declines in the next few decades, the International Energy Agency asserts that achieving a target atmospheric GHG level of 450 ppm CO2-eq would require “heroic achievements in the deployment of emerging low- carbon technologies, which have yet to be proven. Countries that rely heavily on nuclear power would find it particularly challenging and significantly more costly to meet their targeted levels of emissions.”*** This model reflects the mortality from all stages of the fuel cycle *(fuel extraction, transport, transformation, waste disposal, and electricity transport)* for every different source of energy but it has some limitations. As a matter of fact: - **The model excludes serious illnesses.** The mortality factors of such illnesses are 10 times than in Table 1 for fossil fuels and 3 times higher for nuclear fuels respectively. - The mortality factors **exclude the impacts caused by climate** change and development-related differences. - It does not take into account aspects of nuclear power that cannot meaningfully be quantified due to very large uncertainties (e.g., potential mortality from proliferation of weapons-grade material) - Proportions of fossil fuels in our projection cases are assumed to be fixed **Capacity Factor (CF):** The net capacity factor of a power plant is the ratio of its actual output over a period of time, to its potential output if it were possible for it to operate at full nameplate capacity continuously over the same period of time. To calculate the capacity factor, take the total amount of energy the plant produced during a period of time and divide by the amount of energy the plant would have produced at full capacity. Health effects of energy production (2014) <iframe src="https://ourworldindata.org/grapher/health-effects-of-energy-production" style="width: 100%; height: 600px; border: 0px none;"></iframe> > ***As stand-alone events these [Nuclear accident's] impacts are large. However, even as isolated, large-impact events, the death toll stands at several orders of magnitude lower than deaths attributed to air pollution from other traditional energy sources—the World Health Organization estimates that 3 million die every year from ambient air pollution, and 4.3 million from indoor air pollution. As so often is the case, single events that make headlines overshadow permanent risks that result in silent tragedies.*** Learn more here: [It goes completely against what most believe, but out of all major energy sources, nuclear is the safest](https://ourworldindata.org/what-is-the-safest-form-of-energy) ### TL;DR The production of cheap energy is a fundamental component of economic development and is highly correlated with prosperity. The production of energy can also result in negative health outcomes like mortality (deaths) and morbidity (pollution related impacts).  This paper examines mortality rates per unit of electrical power produced from different fuels, coal, natural gas as well as nuclear power. The authors examine historical data and model the potential future role of nuclear power with respect to prevention of air pollution-related mortality as well as greenhouse gas emissions. They find that nuclear power could help prevent: - an average of 420 000−7.04 million deaths - 80−240 GtCO2-eq emissions due to fossil fuels by midcentury, depending on which fuel it replaces. - large-scale expansion of unconstrained natural gas use would not mitigate the climate problem and would cause far more deaths than expansion of nuclear power.