How many nuclear actually killed is unknown because it's not as easy as: something happens, people drown.
It's more like: something happens, a few die fast, the rest dies earlier, their children live shorter or have disabilities, their children also, and so on. Meanwhile collecting waste which will do the same for later generations who might not remember what nuclear energy even is.
Did you even bother to read about how we estimate the casualties of nuclear incidents? It really sounds like you didn't, and just shared your first thought about it not being trivial.
> They have been around a bit longer don't you think?
How in the world does that make them less risky? If a dam collapses, it's generally very bad, even if it is an old dam.
The numbers are highly speculative and are either those you get pushed in your face by the nuclear astroturf (killed on site) or are scientific and the range is very wide since it's so hard to calculate. It's cancer and it happened in the Soviet Era.
Your whole comment didn't add anything to the discussion. What's your point?