Fukushima cost around $200 billion to clean up. I don't think that got factored into the cost of the power it sold.
Now I guess the answer here is insurance, but any insurance company that signs up for a potential payout of $200 billion is going to charge quite the premium, which won't make the already expensive nuclear power any more attractive.
And how do you even calculate the premium here? It's not a house or a vehicle with an easy to determine cost. We're talking about evacuating an area of unknown size for however long might be necessary.
In any case, my point is a different one: energy that's available on demand is more valuable than energy that is not, and we should price it as such. If we don't, we end up doing things like backing up our wind/solar with fossil...which also doesn't have its externalities priced in.
Right now we have a market where wind/solar don't have to pay for the externalities imposed by their intermittency. That is backwards.