I think the top 5 reasons for people that don't understand nuclear energy are against nuclear energy would include:
Safety concerns - The potential for nuclear accidents and the release of radioactive material into the environment is a major concern for many people.
Waste disposal - The radioactive waste generated by nuclear power plants remains hazardous for hundreds of thousands of years, and finding a safe and permanent method of disposal is a challenge.
Proliferation risks - The technology and materials used in nuclear power plants can also be used to create nuclear weapons, raising concerns about the spread of nuclear weapons and the potential for nuclear conflict.
Cost - The cost of building and maintaining nuclear power plants can be high, and there is also the cost of decommissioning the plant when it reaches the end of its life.
Public opinion - Many people simply do not trust or like the idea of nuclear power, and prefer alternative sources of energy such as wind, solar, or hydro power.