Special Report

The World's Worst Nuclear Accidents

Although the nuclear age ushered in humankind’s most terrifying weapons, it also held the promise of a powerful and limitless new energy source. In 1954, the first nuclear power plant became operational in Obninsk, a city southwest of Moscow. Since then, most of the West, as well as China and India, have built nuclear facilities to power their economies. But almost from the start, many people have been fearful of the possibility of catastrophe.

To find some of the world’s worst nuclear accidents, 24/7 Wall St. reviewed several online sources to list accidents rated Level 4 or higher, according to the International Nuclear and Radiological Event Scale, or INES. Nuclear accidents are assigned a level ranging from zero to 10 by a scale developed in 1990 by the International Atomic Energy Agency and the Nuclear Energy Agency of the Organization for Economic Co-operation and Development. Our list does not include military-related accidents and is in chronological order.

According to the U.S. Energy Information Association, there are 31 countries with nuclear power reactors that generate 10.3% of the world’s electricity. In the U.S., there are 94 reactors operating in 30 states that produce almost 20% of total annual electricity generation. Though nuclear power does not produce carbon dioxide, it does generate nuclear waste, and these materials can remain radioactive and dangerous to people for thousands of years.

There have been very few serious nuclear incidents in the U.S. The most concerning was the accident at Three Mile Island in Pennsylvania in 1979, an incident that eerily followed the release of the nuclear-accident film “The China Syndrome” several weeks earlier. (Here are America’s oldest nuclear power plants.)

Nuclear accidents have occurred for a variety of reasons such as miscalculations involving experiments or tests, human error, or a flawed design at some of the facilities. In one case, an old radiotherapy device stolen by scavengers from a Brazilian hospital was mishandled by many people, killing four of them. In Japan, an earthquake and tsunami severely damaged three of the reactor buildings, and fuel in three of the reactor cores melted.   

The incident in Japan is one of two Level-7 events on the list. The other is Chernobyl. There have been two Level-6 accidents, and four Level-5 episodes. In one Level-5 event, a future U.S. president played a key role in averting a disaster. (These are the states with the most nuclear power plants.)

Click here to see the world’s worst nuclear accidents

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