There are many arguments, some related specifically to nuclear energy and others stemming from more general ideas about society. The problem of disposal of nuclear wastes hasn't been solved. There are several good technical solutions, but the political problem hasn't been solved in the U.S. Nuclear energy is uneconomical compared to other sources of energy. It is doing ok. It is bad for humanity to have plenty of energy. - unrelated .
Nuclear reactors produce plutonium, and plutonium is terrible because it can be used to make bombs.
Safeguards are indeed needed. Plutonium is the most poisonous substance known. No it isn't. Plutonium symbolizes nuclear war. - unrelated . Nuclear reactors are likely to have accidents with severe consequences for humanity.