There are two reasons for this high risk peception. One is that while the probability of a catastrophic nuclear plant accident is very small, the damage due to a meltdown could be very high. The general fear is that it could be as high as what happened in Hiroshima or Nagasaki. However, this is misleading. When Hiroshima was bombed, people had no advance warning. At Fukushima, the population in a 20-km radius is already evacuated. So, even if there is a meltdown, the loss of life would be limited. Of course, these will be a high loss of property.
The second reason why people are wary of the risk of a nuclear power plant is that it is a risk not knowingly and willingly taken by people. People who may be affected by a nuclear power plant accident feel that it is a risk imposed on them.
One serious accident in a nuclear plant can lead to large-scale and long-lasting impacts — impacts that do not differentiate between the rich and the poor or the young and the old. But it is also true that our inability to provide clean energy sources to the masses is resulting in around 4,00,000 premature deaths annually from indoor air pollution — largely impacting children under 6. It has also been estimated that air pollution in urban areas leads to approximately 50,000 premature deaths. The key difference between these casualties and those arising from a nuclear accident is that these are widely dispersed geographically and spread through the year, although repeated annually.