What do you think is the safest form of power generation? What do you think is the deadliest? According to a a 2010 study by the World Health Organization, Centers for Disease Control, and National Academy of Science, coal is the deadliest by far, killing 170,000 people per trillion kilowatt hours, or a tragic 1.964 million people per year, 500,000 of which are in China. To put that in perspective, the WHO estimates that air pollution, the primary reason for coal's high mortality rate, kills 7 million people annually. 

So what is the safest form of power? One might think it's a green form of energy such as solar, wind, or hydro. This study suggests something different.

Nuclear power: least deadly, tied for lowest carbon footprint

Power SourceMortality Rate per Trillion Kilowatt Hours
% of Global Power SupplyAverage Annual DeathsTimes Safer Than Coal
Coal 170,000 50% 1.9635 Million  
Hydro 1,400 15% 4,851 121
Solar (Rooftop) 440 <1% <102 386
Wind 150 1% 102 1,133
Nuclear 90 17% 353 1,889

Sources: WHO, CDC, National Academy of Science.

According to the study, nuclear power is by far safest power source in the world -- 40% less deadly than the next safest, wind. 

Examining the numbers
What can explain these shocking statistics? Well, for coal the answer is two-fold. The largest culprit is air pollution, but mining accidents, especially in nations with weak safety regulations such as China, are also a factor. For wind and rooftop solar, the deaths mainly result from workers falling off towers and roofs during installation. Hydroelectric's deaths come mainly from rare but catastrophic dam collapses, such as the Banqiao, China, tragedy in 1976, which killed 171,000.

What's equally surprising, from a climate change perspective, is how these energy sources' carbon footprints compare. For example, coal emits an average of 900 grams of CO2 per KWhr, while wind and nuclear are tied at 15 grams per KWhr, because of carbon emitted during construction, steel production, and/or uranium mining.

The mortality rates for nuclear include the tragedies at Chernobyl and Fukushima, suggesting that nuclear power is, in fact, much safer than most people imagine. 

But what about the nuclear accidents, Fukushima, Chernobyl, and Three Mile Island? 

Three Mile Island
On March 28, 1979, a pressure control valve got stuck in the open position in Three Mile Island's No. 2 reactor. This allowed coolant water to leak out and caused the core to overheat and melt down. According to the U.S. Nuclear Regulatory Commission, this was the worst nuclear accident in U.S. history, yet the amount of radiation released was "small" and had "no detectable health effects on plant workers or the public." After the accident, many sweeping regulations were put in place to make sure such an accident never repeated itself. 

The Chernobyl incident occurred in 1986 in the Soviet Union and was the result of a faulty reactor and improperly trained staff. A steam explosion in the No. 4 reactor released 5% of the core's radiation into the atmosphere and killed two workers. An additional 28 people died of accurate radiation sickness within weeks, and 19 additional deaths occurred between 1987 and 2004, though the evidence for linking them to the disaster is inconclusive. 

On March 11, 2011, a magnitude 9.0 earthquake struck Japan and resulted in a 47-foot tsunami that wiped out the power and cooling systems for three reactors at the Fukushima Daiichi plant. All three cores melted down within three days. It took two weeks to stabilize the cores, and the incident resulted in the evacuation of 100,000 people. Tragically, an estimated 1,000 people were killed by the evacuation, but not a single death or case of radiation sickness resulted from the release of radiation, which amounted to 18% that of Chernobyl. 

The safety of modern reactors

Cumulative Reactor Years

Source: World Nuclear Association

Since the beginning of the nuclear age (14,500 reactor years) there have been a total of 10 core meltdowns, the majority at military and experimental reactors. After the accident at Three Mile Island, the U.S. Nuclear Regulatory Commission instituted new regulations that reactors be designed for one-in-10,000-year core damage frequency standards. In fact, reactors operated by U.S. utilities are designed for one-in-100,000-year damage frequency standards, one-in-1 million years for current generation reactors, and one-in-10 million years for the reactors being designed today. 

What about nuclear waste?
The average 1 GW nuclear reactor generates 27 tons of nuclear waste per year. Luckily, Hitachi Corporation is developing breeder reactors that can use plutonium waste as fuel. This will help eliminate existing waste and prevent future waste accumulation, because these reactors recycle their own waste until none remains.  

Bottom line
The fact is that nuclear power is one of the safest ways to generate electricity and also one of the best ways we have of combating climate change while still allowing economic growth. Modern fears concerning the risks of nuclear power are greatly exaggerated by activists, politicians, and the media, which too often are less concerned with the facts than with supporting their own economic interests and or agendas.

Adam Galas and The Motley Fool have no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.