What is the main reason that people are hesitant to use nuclear energy?
See this site, but note the source is a body that is eager to promote the adoption of nuclear power. The consequences of unrestricted carbon dioxide emission (promoted by coal-fired electricity), and the possible environmental consequences of damming rivers for hydroelectric power, have in the last few years caused some people to question whether opposition to nuclear power is entirely warranted.
There exist legitimate concerns over the safety of a nuclear power plant. Similar concerns could be (and have been) expressed with regard to the environmental consequences of a coal-fired plant, or a hydroelectric dam.