Nuclear power has a bad reputation today.  For its history of several devastating events. Nuclear power in general is dangerous source because it involves radiation. Any damage to the power plant is potentially devastating for the surrounding environment. As it happened in Japan the earthquake and tsunami caused equipment in japan to malfunction and caused nuclear meltdown resulting in leak of radioactive material.
Out of all energy sources outside damage to the facility is most dangerous if its Nuclear power plant. Because it packs so much radiation any kind of incident may turn surrounding area into a nuclear waste.
Nuclear power if ensured its safety is potentially best source of energy so far.