The images of what was left of Hiroshima and Nagasaki in 1945 after the United States dropped the atomic bomb scarred the world -- 200,000 people died in an instant, and once-bustling cities were pulverized into dust.



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But it was the invisible cloud of radiation that no one could defend against that haunted generations.


Popular American movies like the 1983 film "The Day After" played on people’s fears with images of a nuclear winter so destructive that it would kill almost every living thing.


Yet, by that same year, nuclear energy plants were being built from Argentina to South Korea to satisfy the demand for cheap, dependable sources of energy. According to the International Atomic Energy Agency, by 2009, nuclear energy produced almost 14 percent of the world’s electricity supplies. And the total demand for energy worldwide has continued to rise, although the latest nuclear disaster at Japan’s Fukushima plant appears to have dampened enthusiasm for an energy source that produces hard-to-dispose-of radioactive spent fuel and can result in widespread radioactive contamination.


Other major sources of energy have their own benefits -- and their own set of risks. Oil is finite, subject to political pressure and rising prices, and has caused significant environmental disasters of its own, ranging from destruction of habitats to large oil spills. Coal is blamed for significant air pollution, and mining for coal is an often lethal profession: coal mining accidents from Colombia to China have resulted in thousands of deaths.


Natural gas pollutes the air less than oil or coal, but transportation can be dangerous. Old and leak-prone natural gas pipelines can explode, killing and injuring dozens of people. Water or hydroelectric power is a renewable, efficient and clean source of energy, but dams are large enterprises that require a lot of land, and if they burst, the environmental damage is widespread.

The Risks of Power: Nuclear Energy