Nuclear can be done safely, we know this, because every single time there has been an accident it's because an operator did something wrong. The problem is that nobody has yet designed a reactor that a sufficiently amoral operator could not make unsafe. Even if you have completely automatic and passive safety features, a bad operator could disable them if a false positive happens even once and costs them money.
For this reason nuclear has a LOT of regulation and red tape. It has far more than any other kind of energy, because even though the risk of accident is low the outcome of an accident is worse than any other kind of energy except hydro. Hydro has fewer things that can go wrong that are cheaper to check however, so regulations there tend to not be as expensive.